# (CAD) 28 Cyl P&W R-4360



## Rayanth (Jun 11, 2011)

Well, I promised (threatened?) that I would start a WIP for my probably long-running design process for a scale Pratt & Whitney R-4360.

For anyone curious, the R-4360 is considered the largest piston engine to ever go into production for airplanes. It was used on a variety of aircraft at and after the end of World War II, and while thousands were manufactured, most were scrapped when the military no longer needed them due to the introduction of the jet age. Few remain, and fewer still are still flying. Most are in museums as static displays, many were even cut away to show the interior workings.

In the past couple of years I gained a sort of passionate love for this 28 cylinder radial engine that my girlfriend is probably a little jealous of. I have done a lot of research on the engine, and am always doing more. I feel the best way to show this beast a proper respect is to try and develop a working scale model.

*Countless design decisions will be forthcoming, and I welcome input from all corners of the forum on anything that sounds or looks questionable. While I intend to build this behemoth of a model, I currently have no shop, no machines, and very rusty skills. If something looks like it will be impossible to machine, please don't hesitate to speak up.*

The full-scale R-4360 sports some utterly astounding statistics. 4,363 cubic inches of displacement, 28 cylinders arranged in 4 rows of 7 cylinders, with 4 magnetos driving them. It 'sipped' upwards of 100 gallons of 108 octane fuel an hour (try that with today's prices!) all metered from a single pressure carburetor. Each cylinder sported a 5.75 inch bore with a 6 inch stroke, giving a 6.7:1 compression ratio and fired two spark plugs to ensure the cavernous compression chamber ignited evenly and fully. Intake ports were mounted on the top of the chamber, with exhaust out the side (analysis done since have suggested it would have been far more efficient to switch these two, and would have solved some of the intricate heat problems they had). This entire machine was air-cooled, requiring an astonishing amount of air to flow through the cooling fins, and indeed a lot of designs were tried to get the optimal cooling. The 3000-3500 horses were caged in a package that measured 55 inches in diameter and 96.5 inches long, weighing 3,870 pounds dry.

In military applications, the Wasp Major as it was known, was used in a variety of aircraft, from experimental to production. A list of aircraft that used this engine can be found on the following wikipedia article: http://en.wikipedia.org/wiki/Pratt_%26_Whitney_R-4360_Wasp_Major

Perhaps most notably was the F2G "Super" Corsair (Not the much more popular F4U Corsair, but very similar). Postwar, Several F2G's were converted into racers that dominated the air races until a tragic accident shut down the Unlimited Class until the 1960's. Since then, one Super Corsair named the Dreadnought took away numerous finishes, until it crashed in the mid 1980's. I believe Dreadnought is nearing rebuild, but that information may be inaccurate.

My goals with this design are to create a 1/6th scale version of the Wasp Major, though many design concessions will have to be made to ensure that it will be a running model. I will attempt to document the process of development, and as I am using a CAD program it should be easy for me to go back and make adjustments as required (provided I follow proper CAD procedures, something I often fail to do)

Again, if anyone sees anything questionable, has input, or any questions in general, please don't hesitate to jump in and help me. I apologize for this being a CAD work (for now!) and not a real machine, but some time down the road I will start another WIP when I have sufficient tools and skills to give the real thing a try.

Cheers,
- Ryan


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## dmac (Jun 11, 2011)

They are an impressive engine.


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## dsquire (Jun 11, 2011)

Ryan

Congratulations on the start of what is a very ambitious project. Myself and many others will be watching your progress. You have got the hardest part of the project done already, you have it started. :bow: :bow:

Cheers 

Don


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## stevehuckss396 (Jun 11, 2011)

I got my chair pulled up ready for this one.


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## steamer (Jun 11, 2011)

stevehuckss396  said:
			
		

> I got my chair pulled up ready for this one.




Me Too!  Blaze a way Rayanth!...Looking forward to the drawing!

Dave


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## mu38&Bg# (Jun 11, 2011)

Very cool. I always wonder what this sort of project uses for reference. Do you have some drawings you're using, access to an original, or is it going to be a semi scale sort of thing.


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## b.lindsey (Jun 11, 2011)

The drawings alone are an ambitious project...I'm definitely along for the ride!! Should be a great journey too.

Bill


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## Tin Falcon (Jun 11, 2011)

They are some engines I remember many years ago hearing a ww II bomber flying over the house at night. leaving after an air show. I will never forget th sound of the four radial multi stack engines what a drone. 
Probably wright cyclones but what a sound. 
Tin


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## Rayanth (Jun 11, 2011)

The majority of my references come from a book by Graham White, with whom I am also in email contact on occasion, titled 'R-4360 Pratt & Whitney's Major Miracle.' This book is published by Specialty Press, and is no longer in active print. The hard cover is very hard to find, and as a result is quite expensive when you do find it, but I was fortunate to stumble on a softcover copy on Barnes and Noble's website for $75. 

I also have a copy of the service manual for the engine, and a list of patent numbers related to it, which I use a free patent viewing website to download in PDF form and view.

Lastly, I do volunteer work at the restoration center for the Seattle Museum of Flight, and in one of our hangars we have an R-4360 sitting on a handling dolly in the back corner. It seems we'll never use it, or ever refurbish it, and I'm not permitted to take it apart, but I am more than welcome to take measurements of the outside and any photographs I want. I'm going to ask if I can take off one of the exhaust cooling manifolds so I can measure some of the stuff under it, I _might_ be able to convince them to let me do that.

Starting the project wasn't very hard for me... in fact, I could say I haven't actually started yet. The problem I'm facing is WHERE to start. This is an astonishingly complex project, and internal combustion engines in general have everything relying on everything else. I know certain dimensions, from which using standard I.C. formula I can extract other dimensions, but ultimately it boils down to finding a spot and starting there.

I've been turning this issue over in my head for the better part of a week. At one point I decided to do a mockup of the crankcase in my CAD program (Autodesk Inventor 2011), just to make sure I could get the polygons drawn to proper angles. It was far easier than I anticipated - one of the best features of this program is that you can plug in an equation as a dimension, and it will use the result.










Note, the holes 'drilled' in the crankcase are obviously not the full size for the piston. they were only put there to locate the cylinders easier.
Also note that I have the entire engine offset by a rotational factor. As seen, row 'C' is facing directly up, when in fact row 'A' (the aftmost) should be. I was in a hurry.

But a crankcase's dimensions are determined by the size of the components inside of it. So I can't just start at the crankcase, if I'm going to maintain a 1:6 scale. I have the known dimensions of my bore and stroke, 5.75 bore and 6 inch stroke, scaled, are 0.9583~ and 1.0 inches, respectively. From that, I can infer many things about the crankshaft, and ultimately, a radial engine is built around the crankshaft. So a crankshaft is where I will start... problem is, not a great deal of info is readily available about the crankshaft as far as dimensions. From the patent and Graham White's wonderful book, I know how far the offsets are between the master rod journals on each row, but the rest it seems will be up to me.


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## Rayanth (Jun 12, 2011)

*Crankshaft, Revision 0*

After reading all of the fun language that is a patent, two sayings came to mind. One, I've heard a few times in the various places I've been reading about machining engines. The other is a fairly popular one. Nike's "Just Do It", and "Start with a chunk of metal, and machine off anything that doesn't look like a [insert part, in this case crankshaft]"

A Crankshaft is effectively a long cylinder, with additional cylinder offset from its center line by 1/2 the length of the stroke. Where these offsets are, the main cylinder is cut away, to permit the rod for that crank throw to pass through the crankshaft's center line (If it couldn't, your engine wouldn't run very long. Half a turn at most.)

I have no information to go by for how thick the rods are. But what seems like a good guess to me, is about half of the diameter of the piston. My pistons are 0.9583 inches bore, so I'll use 0.479... naw, we'll just make it a half inch thick. I can always drop it to 3/8's later if I need to. If my rods are a half inch thick then by necessity my master rod journals need to be a half inch long, perhaps slightly longer. I'll add 1/32th of an inch to either side as a sort of buffer. Now, the patent drawing for the sideview of the crankshaft (patent is no. 2,426,879, I'm referring to Figure 21) shows lots of fine details, but being a patent, doesn't have dimensions. One notable thing is that the centerline bearing journals are bigger than the master rod journals, thus the 'long cylinder in the middle' is bigger than the master rod pin diameter. I can infer from a scale, assuming the patent drawing is to scale, that the diameter at the bearing is about 35% larger than that of the master rod journal.

... I talk a lot.

Anyway, while measuring that tidbit I found that at the scale I happened to print this image, the width of the crankshaft master rod journal pins is actually a half inch. this is a bizarre coincidence, but I'll take what I'm given! I can use this to get some other basic measurements with ease.

Anyone who saw my original post in the Questions thread regarding split gears will understand that I'm going to likely run into issues if I make this a single piece crankshaft. For now, I will design it as single piece, because it will give me a better visual idea of how I might be able to split it for a multi piece.

A basic layup of all those 'cylinders':













Obviously something's missing - there's nothing nearly strong enough actually holding the m/r journals in place but a thin piece of metal. I did warn that it was a basic layup. Of note in the second image is that each row is offset by 180 degrees, plus the offset between cylinders, of 12+6/7 degrees. this works out to 192.85 and change degrees, which allows each bank to fire on the opposite side of the bank before it, thus evening out vibration. This will make more sense when we get to firing order much later. (A preview of the firing order is visible at http://moozorzica.com/engines/4360order.jpg)

After some basic touchup, we have something that looks a bit more like a basic crankshaft :





This seems workable for now, so I'll leave it at this. Being as this is the first part, it's subject to great changes... hopefully not too badly, though.

I tried to keep the design minimal. I could have done the interconnects in that crazy half-round style they like to do, but this method will be way easier to machine, and will also lend itself to breaking down into multipart easier.

Based on this, I have : master rod thickness: 0.5", master rod journal diameter 0.435", master bearing diameters 0.5", 1/32" buffer on either end of master rod journals, all appropriate angular offsets between rows, etc. The overall crankshaft ends up being 7.200" long in its present design. 

Next up: master rods. These are two-piece designs, that clamp together around the master rod bearing (which are also split bearings but I am leaning towards a multipart crankshaft, in such a way that i can slip the m/r journal bearings in one piece, way cheaper that route) and will require attach points for the other 6 slave rods, in each row. The Wasp Major has two of these actually passing _through_ the bolts that hold the m/r halves together, which I'm sure I can manage, but will require custom made bolts.

This is enough for tonight. Thoughts on whether this would be machinable as one piece? a lot of pieces? Think I'd just end up making a bunch of scrap pieces in the process? I'd love to hear from you.

Cheers,
- Ryan


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## ozzie46 (Jun 12, 2011)

This is one very ambitious project! :bow:

  Can't help with your questions as you are way outside my comfort zone, but know that I'll be watching with great interest.


  Ron


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## gbritnell (Jun 12, 2011)

Ryan,
 I have been reading this thread from the beginning and would like to make a comment or two. First, although I applaud your desire to build this thing you have no idea what is involved. Reading posts by other fellows who have built single row radials will give you an idea of the work involved in producing such and engine. Now multiply that by 28 and even for machinists with years of experience it would become a daunting task. 
 Having designed several engines in my time I can tell you that there is much more to it than coming up with numbers. There's so many problems to be solved when miniaturizing that these issues alone can seem sometimes unsolvable. 
 The second part of my review is that of the actual machining. As you have found out by your initial postings about the gear mountings and how to split or not split them, for someone as you say with 'rusty skills' this should not be taken lightly. 
 I have somewhere upwards of 2500 hours in producing my V-8 engine and I would think that Steve has well over 1000 in just one of his so to build something like this my biggest concern would be the dedication to see it through. 
 You asked for any and all suggestions when you first posted and my advice to you would be, if you really enjoy aircraft radial engines why not design your own 5 or 7 cylinder engine? To design and build even one of these would be a great accomplishment. 
 Just my two cents worth.
gbritnell


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## metalmad (Jun 12, 2011)

u better bet ill be watching :bow:
pete


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## Admiral_dk (Jun 12, 2011)

I will certainly like to see you complete it, but can't help thinking that you ought to do it as a three step approach.

First a single cylinder IC engine with the same design and measurements of the parts as on the multi, as a "fast" way to confirm that you got all your calculations an the design right - it sure beats changing one cylinder head as opposed to 28 if you don't catch an error or the like before trying to run it.

Next step, make the 7 cylinder single row Wasp, again same design parameters. When this is a success, increase the number of rows as much as you desire.


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## steamer (Jun 12, 2011)

I would second Georges comments. It's hard to grasp skill level on a forum., but this engine will take a lot of it and time to boot!

....but then again, so does building a lot of projects.....I guess it depends on who's up for the challange and how stuborn you are. ;D

As Aeromotor's post states, Lee's engines are very well designed and documented. If I were you, I would buy the 14 cylinder two row engine DRAWINGS and have a good read. That would, in my book, constitute an investment in your education....and a very worth while one at that.  You don't live long enough to make all your own mistakes....learn from others......Dave


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## Rayanth (Jun 12, 2011)

I appreciate the comments, folks. I really thought I'd made something clear, but I will try again.

I don't intend to jump into this as my first machining project. I don't expect to even have the CAD work done before I get my shop set up. I know this is ambitious, but I can' keep myself motivated unless I have something special to strive for.

Building this machine is certainly going to be nearly as daunting as designing it at scale. I understand it's not 'just numbers' but a great deal of it IS the numbers. My CAD program is incredibly powerful, and will give me the rest - i can run all of the simulations on it to determine if my numbers _work_... and redesigning a part in Inventor isn't much more than simply changing the numbers - it does the rest. For example, critical dimensions that might change, have been given a custom label. All other dimensions on ANY part that relies on that dimension uses the label in the formula. So, down the road if I find that my crankshaft's main diameter is too big, All I have to do is change the initial value for it, and everything else that relies on it, the openings in the crankcase, the bearings, the gears, will all change for me - and those that are 'purchased parts' will kick back an error if the new dimension isn't available.

My goal is to design this, while I gain my machining skills. I will be changing a lot as my skills evolve and I learn what can and can't be done. I will certainly build a few other engines before I tackle this one, and yes, 28 cylinders is a great deal of complexity. I am already working on designing a test rig for each cylinder. after each cylinder and piston is built, it'll be tested on its own as a one cylinder engine, before adding it to the 28 cylinder behemoth.

I'm even considering adapting plans for smaller radials to use the cylinders I come up with for the 4360 - this would let me build a few at a time, and if nothing in the design changes, use them later.

Re: Lee Hodgson - In a sense, he gave me the idea! I visited him personally at his shop in Cincinnati and saw his machines first hand. His father had begun work on designing the 4360, but ran into certain complexities and never finished the project. Those complexities were mostly in the very strange angles and offsets that are very hard to obtain - but with CNC, they should be quite doable. I respect Lee and all of his beautiful engines, and do fully expect to be building either the 14 or 18 double row from him before I start making chips for my 28.

I'm sorry to say it, but I won't be dissuaded! I have (hopefully, I'm only 31) a lot of years left to tweak and fine tune details if I must, but this machine will see life some day. I would hope that you all have experienced a project for which you had such dedication, and help me out when I stumble, on this one.

- Ryan


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## stevehuckss396 (Jun 12, 2011)

Rayanth  said:
			
		

> I'm sorry to say it, but I won't be dissuaded!




You have about 50 years before the body starts to fail to the point where model building is no longer possible. You better get going!!!

I am looking forward to seeing progress and if you never build a single part, this will still be a great thread.


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## Rayanth (Jun 12, 2011)

... It seems I woke up on the wrong side of the bed. (I was still IN bed when I wrote my last reply). I apologize if I was 'snarky' in my last reply. My life has been riddled with people telling me I can't do something, and nobody has ever told me I can. It seems everywhere I go, I meet with resistance. But I digress.

I am fully dedicated to making this thing run. It's been in my head for well over a year, and led me to many other radial engine designs that I have also toyed with in CAD while learning my CAD program as well as more about how the engines work. I've built the Edwards Radial 5 3 times in my CAD program now, making minor changes here and there so things worked better, and run all the simulations to ensure my changes didn't affect the running of the engine, etc. I have also done extensive reading on I.C. Engine design, and am fully familiar with the physics behind them.

As I did say earlier, I know better than to make this my first machining project. I agree, it's beyond my scope for now. I do intend to make the Edwards 5 (I haven't seen anything that makes me say "I can't figure out how to machine that") as one of my first projects, perhaps with a single-banger before that. Lee Hodgson's engines were suggested as a step up, and I've been considering those as well. I was leaning towards the 18 cylinder, but it seems the 14 cylinder will give me more information on the strange angles involved.

The biggest problem with the R4360 is that it's 4 rows. No other production radial engine is 4 rows. Others were developed, but never saw production. The added two rows add a ton of problems that can't be solved by gaining experience with one or two radials - even in a two row, the bearings and cams are on either end of the crankshaft... nothing has to worry about splitting bearings, splitting gears, and splitting the master rods (V8's might have to split the master rods, I'm not familiar with those - if anyone has a recommendation for a starter V8 I'd be glad to hear it). THAT is why I'm tackling the design phase now - the earlier I can identify the problems, the more time I have to figure out how to get around them.

Again, I apologize if I sounded snarky. This engine has become a dream of mine, and I was feeling rather defensive. I will see it through to the end, though it may take years. I will build my skills along the way, and probably make a million modifications to the design as I learn what will and won't work. I know it will be rough, but that's part of why it appeals to me - if anything, I am more determined to see something through, when I've been told "you can't" or "it's too hard" - I love to prove the naysayers wrong ;D

I've heard Bruce Satra may have made one but can't find anything on it, and only one other static, non-running model was made that I can find. This is entirely new waters, and I will be glad of any help you fine folks have.


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## el gringo (Jun 12, 2011)

Off topic in a way but I have to mention the feeling transmitted through my body whilst sitting amongst four Major Wasps running @ 60 inches just before the A/C released the brakes for the takeoff roll. As I think of it now I feel it. I was also fortunate enough to run them up for ground maintenance as a crew member (maintenance scanner, waist blister) RB 50f

Hope this dosn't screw up the thread too much!

ray M


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## Rayanth (Jun 12, 2011)

Ray-
not derailing my thread at all =) I love to hear the stories. I've heard it said that at a META power check in a maintenance hanger, if you were standing in the wrong spot you would be struggling just to breathe...one day I hope to experience the real thing, but until then, this is what I have =)

- Ryan


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## steamer (Jun 12, 2011)

Ryan,

Not trying to dissuade you.  I know where your coming from I can assure you. So does George and Steve.

I spent 13 years building a boat.  If you want a bunch a people telling you "you'll never do that" or "Are you nuts?!"

Try building a steamboat....from the ground up.  I got it worst from my siblings. I'm laughing now!

http://www.homemodelenginemachinist.com/index.php?topic=3198.0

If it's in your heart, go for it.

However, you did solicit comments...George was commenting, as was I.

Interesting thing about Forums...you only understand what has been typed

Glad you talked to Lee.  The fixturing for the engines is tough to do from scratch.  It's nice to get the drawing package with the manufacturing engineering done already! But I suspect you know that already.

We're a good bunch Ryan. We don't kick people when they're down, but help them up.

jump in and have fun.

Sincerely,

Dave


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## Tin Falcon (Jun 12, 2011)

. 





> It seems I woke up on the wrong side of the bed. (I was still IN bed when I wrote my last reply). I apologize if I was 'snarky' in my last reply. My life has been riddled with people telling me I can't do something, and nobody has ever told me I can. It seems everywhere I go, I meet with resistance. But I digress.


I feel your pain bro. I guess I have been feeling a little snarky this weekend as well. 

I know the feeling of being told no more often than I want to admit. Seems like a lot going on in life and lots to think about sometimes and often too little comfort and fun .
 The best of luck with this project . I will tell you the same thing I told my son a few years back "If anyone can figure out how to do it you can" My son loved legos when he was younger he is 21 now. when he was IIRC about 14 he wanted to build a working air powered engine built from legos. I he wanted me to figure it out for him . I did not feel like I had the time and energy to figure it out at the time. and I told him that as well he did figure it out the engine runs it shows up at shows and is in the gallery on the FAME site. sorry it does not link well. 
I sometimes quote the old possibly Chinese saying
"Those who say it can not be done please do not disturb those doing it. "
I would thing the biggest challenging will be the crank case. the crank shaft not too bad. the pistons cylinders con rods valves etc. you should get real good at lots of copies of each . 
Tin


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## Rayanth (Jun 12, 2011)

Not much work today on the 4360 'Wasp Major Mini'. I'm at the first of many roadblocks. Having designed the basic layout of the crankshaft, the next logical step would be the master rods. In themselves, the master rods aren't particularly complex, though certainly more complex than what you might expect of a smaller radial. Each master rod is identical, composed of two pieces split horizontally and joined together by 4 vertical bolts. These bolts pass through the plane of two of the link rod pins, the bolts have holes drilled in them to accommodate the pins passing through.

The issue here is that I don't have much to go by for the dimensions. While I had a good drawing of the crankshaft with which to make my measurements and scale, I only have a 3/4 view photo of a real master rod to go by. this view doesn't permit me much in the way of dimensions, and I've no idea what the scale is. I'm going to have to do a lot more guesswork to get this component right. Further compounding the fact is just how much of a load this component is under. The full scale engine transmits upwards of 1100 to 1500 horsepower through each master rod... improper design will easily lead to failure. The last problem is that a rod's length is only loosely determined by the stroke of the engine. One of my I.C. Engineering books suggests the ratio of the connecting rod length to the crank radius should be in the 3-4 range for 'smaller' engines (though the book's idea of 'small' is more on the scale of automobile engines). since my crank radius is the same as my stroke, this means a connecting rod length of 3 to 4 inches. A longer rod makes for a slower engine (if you disregard many other factors). 

The rod length drives my cylinder length, by way of deriving compression ratio from piston travel... so another component I could focus design on is the piston... Pistons around the world have the same basic conceptual shape. This engine in particular uses a domed-head piston in a hemispherical combustion chamber, compounding the math for the compression ratio, but nothing beyond my capabilities...

Just trying to decide where to go next... sigh, I hate decisions.

More later
- Ryan


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## steamer (Jun 12, 2011)

Hi Ryan,

Do you know the crank pin diameter? ( I think you said you had a good reference for the crank)

Secondly, do you have a reasonable scale view of the rod? with the crankpin bore?

If you know that diameter, you could scale the rest. It should get you close and the length can be adjusted later once you start laying in the top end of the cylinders...don't put too much detail in yet until you get the pistons and the cylinder top end laid in..A stick figuire right now would suffice until the rest of the parts are "doped out"...just a thought.

Dave


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## steamer (Jun 12, 2011)

by the way, a longer rod will reduce your piston peak acceleration and decrease your side load on the piston skirt.

As long as they don't buckle, a long rod won't hurt you. 

Dave


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## Admiral_dk (Jun 12, 2011)

I'm sorry if you hurt your feelings, that certainly NOT my intention - au contraire - I was only pointing a step by step approach to achieve what you set out to do.

If all the steps are small enough, they are (normally) all doable and all within reach.

I will certainly continue to follow this thread. All interesting threads here are bit like brainstorming and that has always been a part of the process (several times along the way) of the best projects I've been part of - I'll NEVER be able to make as good construction by myself as I has, when part of a team. And even if I can't contribute - I'll still learn something


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## steamer (Jun 12, 2011)

Hi Admiral

None other than Harry Ricardo used that approach on every new concept engine...single cylinder test bed first.


Dave


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## Rayanth (Jun 12, 2011)

Dave, I estimated the crankpin diameter as c/t the crankshaft (referenced as the 'master rod journal') as approximately 0.435 inches. However, the engine uses bearings in between the master rod and its journal. I realize many scale engines don't use the bearings, because they're not used so much that wear and tear is really a concern. I'm still fighting over the idea of using bearings on mine. It would certainly be FAR easier not to!

The only images I have to go by for the rods themselves are below. (I think. this is the first time i've tried 'attaching' images instead of inlining them. they're bigger)


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## Rayanth (Jun 12, 2011)

Admiral,

Think nothing of it. We'll just sweep those metal shavings under the rug. I was just in the wrong mood this morning when I read the replies. I get over things quickly, and am in a rather more upbeat mood today. Ironically, I hadn't fully understood the gist of what you were suggesting back on page 1, and it turns out I'd already more or less planned on that route, to a degree.

It had occurred to me that machining 28 cylinders worth of engine and putting them all together and seeing if it would run, wouldn't tell me WHERE a problem existed in all that metal. If I had binding, or uneven firing, or NO firing, or any of the multitudes of issues that could happen with a running prototype engine, it would be next to impossible to figure out which cylinder was at fault. So my idea is to build a test rig, on which EVERY cylinder will be tested before it is moved to the Wasp Major 'Mini'. In this way, presuming the test rig works, I will both be 'running in' each cylinder/piston/valve set, and ensuring they're machined properly before putting them in a place where it would be much harder to isolate problems with them.

I had also thought it could be interesting building them into a 7, then a 14, etc. this way i can machine a few at a time and avoid the tediousness of making 28 or 56 of every part!

I will require some input from the forum in the area of spark plugs. If I were to try and purchase Rimfires for this machine, and kept the 2-sparks-per-cylinder of the full scale, then it would cost me well over $1000 for the spark plugs alone. This cries out for making them myself, and I've seen several posts by others where they've had success at doing so. I hope to ask for help in that area when it comes time.


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## Captain Jerry (Jun 12, 2011)

As a kid living in Ft Worth Tx at the end of WWII, it was not uncommon to see and hear, flights of 100 or more B-24 Liberators overhead as delivery flights formed up leaving the Consolidated Aircraft plant. These planes had four of the Pratt & Whitney 14 cylinder radials. What a sound. Made your heart pound. And the silence as the last plane faded from sight was deafening. A few years the B-36 took to the air with six of the 28 cylinder engines. They were never produced at the same rate as the B-24 but we did see flights of six aircraft at a time. Even just six aircraft meant that over 1000 pistons were thundering over. This plane had high altitude capability and introduced the world to the sight of contrails in the clear blue sky.

There is nothing to compare with the sound of a big radial engine or lots of big radial engines.

Jerry


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## stevehuckss396 (Jun 12, 2011)

Rayanth  said:
			
		

> I will require some input from the forum in the area of spark plugs. If I were to try and purchase Rimfires for this machine, and kept the 2-sparks-per-cylinder of the full scale, then it would cost me well over $1000 for the spark plugs alone. This cries out for making them myself, and I've seen several posts by others where they've had success at doing so. I hope to ask for help in that area when it comes time.



Many here have made them so you will have many options in that department. What scale will this engine be designed to? I have plug designs down to #6-56. I have made plugs for the Demon at #8-40 thread


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## ozzie46 (Jun 12, 2011)

Regarding the bolts and link rod pins, wouldn't it be far easier to drill holes in the link rod pins and pass the bolts through them than the other way around? That way the pins would be captured and there should be very little if any end play.

 Ron


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## steamer (Jun 12, 2011)

Rayanth  said:
			
		

> Dave, I estimated the crankpin diameter as c/t the crankshaft (referenced as the 'master rod journal') as approximately 0.435 inches. However, the engine uses bearings in between the master rod and its journal. I realize many scale engines don't use the bearings, because they're not used so much that wear and tear is really a concern. I'm still fighting over the idea of using bearings on mine. It would certainly be FAR easier not to!
> 
> The only images I have to go by for the rods themselves are below. (I think. this is the first time i've tried 'attaching' images instead of inlining them. they're bigger)




Ron Colonna uses sheet silver in his Offy for bearing inserts.  Apparently this was the "cats backside" on racing motorcycles and some air craft engines.  He used .010 thick sheet. His book on the Offy is a GREAT read by the way...hint hint. ;D
No way connected, just thankful for the education I got from his book.

Silver is the best bearing material there is according to some and I know most of our WWII radials had silver lined inserts.

0.435 is damn close to 0.4375....It's easier to find those reamers... ;D


Dave


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## Rayanth (Jun 12, 2011)

I brain-farted when I made the calculation in my head. I knew there was a .43something... I'll make the change, very simple to do. The 4360 did indeed have silver-lined bearings which were subsequently lead-indium plated as well.


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## Rayanth (Jun 12, 2011)

stevehuckss396  said:
			
		

> Many here have made them so you will have many options in that department. What scale will this engine be designed to? I have plug designs down to #6-56. I have made plugs for the Demon at #8-40 thread



Steve, it's a 1/6 scale, but at the size of this machine that might mean something different to you than it does to me =) As noted in my crankshaft post, the crankshaft alone is 7.2 inches long.

In terms of the spark plug, the piston has a .958 inch bore and 1 inch stroke. give you an idea of the size of spark needed - my own experience in that area is quite limited.

- Ryan


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## steamer (Jun 12, 2011)

We progress!... ;D
IIRC, 7/16 or 1/2" was the journal size on Ron's engine
Here's Ron's Web Site....

http://www.ronsmodelengines.com/Offy.html

Take a look and see if any of that "floats your boat"

Dave


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## stevehuckss396 (Jun 12, 2011)

Rayanth  said:
			
		

> Steve, it's a 1/6 scale, but at the size of this machine that might mean something different to you than it does to me =) As noted in my crankshaft post, the crankshaft alone is 7.2 inches long.
> 
> In terms of the spark plug, the piston has a .958 inch bore and 1 inch stroke. give you an idea of the size of spark needed - my own experience in that area is quite limited.
> 
> - Ryan



At 1/6th anything will look to big. smaller the better but . . . the smaller the harder to make and reliability might suffer. 
when you get to the point where the head is designed, I'll send some cad files and you can see what they look like.


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## steamer (Jun 12, 2011)

That's a sweet looking plug Steve!


Here's a source for 0.999 pure silver sheet in 30 guage ( .010")

http://www.riogrande.com/MemberArea/ProductPage.aspx?assetName=101930

2" x 6" sheet is $28....and should provide enough bearing material for a few engines.

Dave


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## Rayanth (Jun 12, 2011)

Dave, am I mistaken in understanding that you're suggesting making the bearings myself?  I didn't think was possible...

- Ryan


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## steamer (Jun 12, 2011)

YUP!







That's the concept anyway...

If you have doubts...click on Ron's web page under "Listen to it run"

Dave


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## Rayanth (Jun 12, 2011)

... right, I'll just order the darn Offy book. ;D

Chances are it'll make me want to make an Offy. I've already got a few others on my potential list...

Damn you guys for giving me the bug! Now I'll be making little putt-putts until the end of my days... which is a long way off.

In other news, re-made the Edwards 5 Radial in CAD today. Needed to remember how I made the cams, so I figured I'd just do it again! Law of Sines gave me some pause for a while, but I'm back in business.


- Ryan


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## steamer (Jun 12, 2011)

Damn you guys for giving me the bug! Now I'll be making little putt-putts until the end of my days... which is a long way off.


Well I certainly hope so!


Good night Ryan

Dave


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## gmac (Jun 12, 2011)

Ryan;
I'll add my +1 for the purchase of Ron's Offy book, particularly for understanding the machining methodology. Another book I'd recommend, particularly for the radial is L.K. Blackmore's "Bentley BR2 World War 1 Rotary Aero Engine" which covers the plans and fabrication of a scale engine. One of these;
[ame]http://www.youtube.com/watch?v=P_-HhEfH1XQ[/ame]
Ron did one in 1/8th scale with glow system;
[ame]http://www.youtube.com/watch?v=R3bcrfC1Pz8[/ame]
I'll be following this thread - never mind the nay-sayers (just teasing, the support around here is phenomenal), why build something you're not passionate about?!
Cheers
Garry


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## Rayanth (Jun 14, 2011)

I was at the museum today, working on the YO-3A, but took some time off to grab a few measurements of the 4360 we have sitting in a corner gathering dust.

These measurements aren't exactly precise, but they are close enough for my purposes. Combined with the drawings I have from the patents and Graham White's book, they should enable me to derive quite a lot of other dimensions.

Cylinder base to intake port (low point of 'top' of cylinder): 11.5 inches
Half width of cylinder: 4 inches at base (because the cylinders are split between casings, this derives other info)
Front of row 2 cylinder to front of row 1 cylinder: 10" at base
edge of cylinder to bevel over case bolt: 1"
base of cooling fins to cooling fins at intake 'top' of cylinder is 10 inches, with 66 fins

initial derivatives of this information:
half a cylinder base is 4 inches, thus a cylinder base is 8 inches. front to front is 10 inches between rows, so there's 2 inches of 'space' at the case's face between rows. Additionally, as a cylinder is also 8 inches wide, and there is 1 inch to the bolt bevel, this leaves about 10" to each face of the heptagon that forms the perimeter of the case.

Depth of the cylinder, to the top of the cooling fins, combined with drawings from the book and patents, will allow me to set a scale to those drawings, and thus derive other dimensions; those dimensions combined with compression ratio and stroke will let me back-calculate the length of the master rod and link rods!

Hey, it's a long way to go around to get there, but since I can't take our engine apart, it's what I've got 

- Ryan


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## gadabout (Jun 14, 2011)

hey there is one on Ebay at the moment (Well was yesterday) starting price of $25k

http://cgi.ebay.com/ebaymotors/Prat...490484QQ_trksidZp3286Q2em7QQitemZ120715766222

cheers 
Mark


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## Rayanth (Jun 14, 2011)

Yeah, i've seen them for as little as 5k in the past. Still trying to pay off 17k on my car, which is actually doing me some good at the moment ;D


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## Rayanth (Jun 26, 2011)

*Piston, Revision 0*

Just worked 13 days straight, so I apologize for the lack of updates on this front. Today is a rare day off, before I go into another 12 days straight, and I'll have enough consecutive weekends to tell the company they can't designate me on the weekend of the 9th and 10th, so I can go to the (very nearby) Arlington Fly-In.

Today I'll try and get some of those dimensions I posted earlier, into some semblance of working dimensions to derive other stuff from. I would like to get the master rod started, but I need other things first.

Using the dimensions I recorded from the 'real thing' a couple weeks ago, combined with existing knowledge of bore, stroke, and compression ratio, I can figure out the dimensions of the cylinder. This will theoretically help me figure out the master rod length, and I can work from there.

So one of my measurements taken was the cylinder's height, which I placed at 11.5 inches to the top of the 'intake port' (This is the point on top where the intake is bolted in. The 4360's Intake is on top of the cylinder, and exhaust on the side). The following picture shows what that measurement actually means, highlighted in yellow. I can use this to figure out the scale of the shown drawing, then work out such things as valve sizes, the height of the cylinder sleeve, etc.







My printed copy of the image the above is excerpted from, has that dimension at approx 1.65 inches, giving me a scale of 1.65/11.5 or 14.3 %. Any dimensions taken from this drawing, divided by 0.143 should give me an approximate fullscale dimension, then divided by 6 gives me my scale dimension. To confirm this, I take a measurement of the piston, which we know has a bore of 5.75 inches, measures 0.82 in the drawing printout, which is 5.734 inches using my math - close enough for government work! And I'm former Air Force, I would know ;D

I will probably use this value to go back and work out some of my other dimensions that I was sort of guessing on, like the crankshaft. This drawing shows that as .43 inches, or 3 inches full scale, so half an inch at my 1/6 scale, and... I used .435 inches, so I have some work to do. (this was for the master rod journal) And of course a change here changes my master rod, so I'm glad I checked this now.

Moving back, I have decided to do a revision 0 mockup of the piston. Knowing the piston is 5.75 inch bore, I can correlate the two drawings I have that show the piston, to glean information on the wrist pin, and one view even shows a very clear outline of the master rod, which will help me later. The piston on the R4360 is hemispherical and has 4 rings, with one additional ring at the very bottom. The image shown gives a piston height of 0.59 on paper, or 4.125 at full scale, so .6875 (11/16) at my 1/6 scale. I can't quite make out the detail on the grooves for the piston rings, so I will just use an arbitrary for now, and call it 1/32x1/32, and space them roughly where they look in the drawing. I can blow it up later and get a slightly more accurate idea if I wish. Lastly, the hemispherical part appears to extend about .06 inches, or .4195, or .07 inches at scale, I'll go with the nearby .0625, 1/16th of an inch.

One minor deviation, the 1/6th scale puts the bore at a strange 0.9583 inches. I like to work with even numbers, so I would round this either to the nearest thousandth, or nearest fractional equivalent, which lets me choose between 0.958, or a fraction of either 15/16 or 61/64 (0.9375 or 0.953125 respectively) - 15/16 sounds nice and easy even though it's further from true scale, so I will use it for now. I understand machining is easier in decimals, but for now, it's easier for me to track the numbers if they equate nicely to fractions. This is being done in CAD, so they can always be changed later 

So, without much further rambling, we have a piston of 0.9375 bore, that has a base height of .6875, plus a hemispherical addition of .0625. This piston has (4) 1/32" grooves for the rings, plus an additional one near the bottom. (Some math would normally be required to figure out how to make that hemisphere, but CAD lets me just do an arc consistent with three points, and then rotate that arc about an axis to get the 3d solid  (I can then go back and get the radius of the arc if I need it - in this case it works out to 1.7890625 inch radius)

iso view:





side view to show hemispherical surface:





That will wrap up this post, but I'm obviously not done with the piston. It's all I can do from the one view in the patent that I was working from. Another view will give me the dimensions for the cutout for the wristpin, and the wristpin itself... and that will be my next post. perhaps later today, we shall see ;D

As always, comments are highly welcomed, as I don't have the machining experience to know if my decisions are wise! Would you have done something differently? Did I forget something important? Note this is Revision 0, or not-for-production; it's intended to get the basics down, and will not be made as-is. Rev0's are expected to be changed as other parts of the engine are designed and force changes in existing parts. 

- Ryan

(edited to correct typos. who needs proofreading when there's a 'modify'?)


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## steamer (Jun 26, 2011)

Ryan,

A logical progression.  Seems like a plan to me!

The elephant goes down one bite at a time.

Dave


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## Rayanth (Jun 26, 2011)

One small addition to the piston.

The patent picture that shows the cutaway view of the piston is to an odd scale. as the cutaway isn't of the same piston as the other view i was working from, which was the cylinder that points directly up. The cutaway is at an angle, so the piston is 'squashed' and that was going to lead me to inaccurate dimensions.

Upon closer inspection of the piston's cutaway, I determined that all four of the upper rings are compression rings. There's simply no cutout deep enough for oil to reach them, so the only oil ring must be the one at the bottom. Part of me wonders if this is to help combat the oil-pooling issue with the lower cylinders of radials. Either way, I opted to just fashion my own cutout for this area.

The 'walls' at the bottom were kept at 1/16" thickness to ensure stability for machining. the wrist pin was settled upon as 3/16" thickness based on what i could estimate from the cutaway drawing, so the hole for the wristpin is 3/16".






The only thing left is the holes for the oil to pass into the oil ring. I held off on this because I'm concerned of the size. the oil ring slot is 1/32" as currently designed. This limits the oil holes as a maximum of 1/32" diameter... and this seems rather small to me. I know at that scale liquids behave differently, so I ask the group - should I enlarge the slot so the holes can be bigger, or is 1/32" (0.03125) sufficient with, say, 8 holes ?

- Ryan

Postscript:
I may consider deepening the cutout for the master rod. I would have to look into it as a possible 'later' thing. If I cut out more material there, then I'm lightening the piston's overall weight, and thus forcing less work on the engine, and getting more power in the end. As it is right now, the cutout goes to the edge of the bottom compression ring, and it might not be that huge of a difference.

(edit to Postscript: I probably will have to go at least a little bit deeper. I forgot to account for clearance for the top of the master rod. doh!)


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## steamer (Jul 7, 2011)

Hi Ryan,

Make sure you have enough wall thickness between that lower oil control ring and the counter bore.

1/32 doesn't sound too far out. I would use Ron's Offy piston oil ring drains as a guide as his engine runs far faster than this will.  So should be big enough

Dave


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## Rayanth (Jul 7, 2011)

thanks for the heads up, Dave, I'll take a look and compare to the offy's thickness when I get a chance... possibly sunday. Work just exploded into an angry hornet's nest, so I haven't had a great deal of time to sit and think on this.

- Ryan


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## Admiral_dk (Jul 7, 2011)

Hi Ryan

I wouldn't use so many rings - to much friction on such a small engine - max. two compression rings and one oilring.

Of cause - if your goal is to make it as accurate as possible instead of a good runner (witch is rather tuff with this many cylinders in such a small scale) go ahead otherwise reduce the number of rings, surface area of the piston to cylinder interface and all other points of contact. If you make an exact copy of the original - I'll expect that you lose more than 70% of the generated power to friction.


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## gbritnell (Jul 7, 2011)

On a model engine I don't know how much lubrication is provided by an oil ring. 
As was stated, for model engine use 2 rings should be more than adequate for sealing and they can both be of the compression type. 
gbritnell


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## gbravo (Jul 7, 2011)

In my actual design of Wright J5, also I am considering 3 compression rings and one oil ring in the botton of the pistor, but if you estimate loose of 70%, is very high, I will recheck.
The oil ring in the piston botton I think is necessary because the oil splashed from the main connecting rod bearing and crankshaft bearings, drop directly to the bottom cylinders.


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## Rayanth (Jul 7, 2011)

So I grabbed the offy book on the way out the door and am examining it again. I can't compute the thickness of the wall at the oil ring off hand, i'll draw it up in cad and run the calculator on it there, but of note is the oil passage holes, which I had questioned my size on. I had arrived at 1/32" at scale, and the Offy is 3/64, or 1.5/32, which means I am probably fine at 1/32, but I will just adapt it to meet the Offy's size.

Calculating the wall thickness at the minimum point will require some basic trigonometry, and better calculator functions than my phone has handy, so I will do it later ;D

- Ryan


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## Admiral_dk (Jul 7, 2011)

An oilrings function isn't to lubricate the piston / cylinder, but to remove the excess oil from the cylinderwall in order to keep it in the crankcase. So for that reason it could be argumented that you should keep it, although it alone isn't going to keep you out of trouble with "hydro locks" in bottom cylinders if it's stationary for longer times between runs.

I'm most certainly no expert on motors with hanging cylinders, but I do know that one of the ways to prevent some of the problems is simply to let the "cylinder sleeve" reach higher into the crankcase than the oil level.

I'm not sure, but the P&W engines might be dry sump systems, witch will help quite a bit too.


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## steamer (Jul 7, 2011)

Well we can all discuss the function of the oil ring in this case.  I have NOT built a radial.

However, I think Ryan stated at one point that he spoke to Ageless regarding their 7 and 14 engines and maybe he has gleaned some information from that....


Just a thought....

Dave


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## Rayanth (Jul 7, 2011)

I hadn't really gone into great detail about the designs with Ageless, but I am about to place an order for the 14cyl plans, on payday. Probly get the casting too, just to put it on the 'to do' list for when I do get the shop set up ;D

(Current plans there are for a 1 cyl engine first project, then the 5 cyl Edwards radial, then the 14 Ageless while using the skills gleaned, to tweak the 28 design. The 4360 will be built in stages, with a single cylinder test bed to run each cylinder on to ensure they all work before mounting them all on the same engine. Might do a 7 cyl test bed as well, just because ;D)

As for oil rings...well i'm not the expert there. Discuss away!

- Ryan


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## steamer (Jul 7, 2011)

Just looking for data...Data is very helpful.

Dave


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## Rayanth (Jul 7, 2011)

Speaking with an A&P mechanic at work who has rebuilt a few 4360's, the purpose of the oil ring is indeed to drain excess oil from between the cylinder wall and piston. However, this then raises the question- why use a ring, and not just a channel in the piston and the holes through it? What purpose does the physical ring add, that pays off for the added friction and complexity?

If you forgo the ring, and use channel/holes, you could ensure that they drain beyond the base of the liner, and thus are effective on the gravitationally bottom cylinders...with a ring you have to make sure the ring stays in the liner, and lose that effect.

- Ryan


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## Leucetius (Jul 8, 2011)

IMHO The ring touches the cylinder, thus it can wipe the oil off.


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## mu38&Bg# (Jul 8, 2011)

The oil control ring is there to remove excess oil while the engine is running. It reduces oil consumption. The sealing rings only need a film of oil to ride on to do their work. Too much oil and it migrates past all of the rings into the combustion chamber where it ends up going out the exhaust valves.

In a model engine one can forgo oil rings and mix oil into the fuel like a two stroke, or just deal with the oil consumption. Most model engines using crankcase lube have oil control rings. I do believe they are effective, though I have no direct experience with them. A demo engine running a few minutes oil really isn't an issue. maybe if you intend to put the engine on a model and fly for hours on end, oil control is something to consider. The little Honda four stroke utility engines have a pair of compression rings and a typical oil control set.


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## gbravo (Jul 8, 2011)

In the radial engines that I know, the oil falls into the crankcase is received by the bottom wall, which forms a small accumulation chamber because the cylinder liners are longer, and then this accumulated oil is drain though a pipe or crankcase channel to the return tank below the engine, where it is sucks for the bilge pump and returned to the oil tank (dry sump system).


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## steamer (Jul 8, 2011)

Interesting

The 14 cyinder radial shown here has 1 (one) ring

http://engineman.de/index_eng.html 

HMMMMM  knowing what I know about the amount of friction in the system compared to the HP produced for an engine this size...there's some wisdom there.  Perhaps 2 rings if your work is not quite to national lab standards.......

Thoughts?....I know George already mentioned this

Dave


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## mu38&Bg# (Jul 8, 2011)

One is enough to run. And if you lube is mixed with fuel allows enough oil past the ring to lubricate the bottom end. Virtually all four stroke engine for radio control use just one ring.


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## steamer (Jul 9, 2011)

And to your point, it would appear that the crankcase is the intake plenum on that engine.  So clearly it's a mixed oil engine as you state.

Dave


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## Rayanth (Jul 20, 2011)

Just an update, things are getting incredibly hectic at work - when you produce these massive machines on a tight schedule, and have significant issues three in a row, the delays ripple back through the entire assembly line, and you end up risking "jig lock" - the beginning of the assembly line building components faster than the end can use them, and eventually running out of space, thus shutting down the whole line. I work at the end where the magic happens, as well as the delays, so i've been pulling a LOT of overtime lately...I can't remember the last time I worked less than 70 hours in a week, and I only had last weekend off because of a work injury.

Anyhow, haven't had free time for this project, though it's still on my mind. I might be able to work it a tiny little bit once I get to my new home in a few weeks, but in the meantime, don't expect any updates :/

- Ryan


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## steamer (Jul 20, 2011)

We're not going anywhere Ryan....take you time

Dave


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## abcmorgan (Aug 6, 2011)

Just wondering if you've seen this page, thought it might be worth a look....

http://www.enginehistory.org/model_engines.shtml

If you scroll down to Engine Models by Dennis Fadden there's an R-4360.

Regards,
Morgan


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## adamgd (Oct 16, 2011)

Cool project! :bow: 
I worked on Crutiss Wright R3350 engines and want to make an Ageless model. If you get things working could we get copy's of the plans? ???


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## BillH (Oct 17, 2011)

I could not imagine doing this project without a CNC lathe for all the cylinders and pistons!


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## steamer (Oct 20, 2011)

Hey Ryan,

Hope your feeling better, the house sale is closed, and the production line is not locked.

Seriously....hope all is well....come back soon.

Dave


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## Rayanth (Nov 23, 2011)

Greetings all,

I apologize for the lengthy absence, since my move things have gotten quite hectic, and Life has just gotten in the way. I appreciate the well wishes i've received, both here and in PM, and and hope to get back in the swing soon.

Regarding the 4360 at AEHS, I believe that is not a running model. I did quite a bit of looking into on hthat, and while it is articulated, I could never find anything about it ever running on gas.

I am still not sure if I can host decent machines on the puny power available in my garage, and I now have kittens to worry about indoors... shop plans will have to adapt for that.

I'll be in touch in the future, happy thanksgiving everyone!


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## jwcnc1911 (Jul 3, 2013)

I noticed you were on the forum in April of 13, any progress on this project?


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## Bentwings (Jul 19, 2020)

Rayanth said:


> Well, I promised (threatened?) that I would start a WIP for my probably long-running design process for a scale Pratt & Whitney R-4360.
> 
> For anyone curious, the R-4360 is considered the largest piston engine to ever go into production for airplanes. It was used on a variety of aircraft at and after the end of World War II, and while thousands were manufactured, most were scrapped when the military no longer needed them due to the introduction of the jet age. Few remain, and fewer still are still flying. Most are in museums as static displays, many were even cut away to show the interior workings.
> 
> ...


Hi I to am interested in the r4360 mine would be a bit smaller based  on M. hogston’ r 280  I just got the book by  White and  have waded through it once and now looking more closely. How does the crankshaft link rod work. I’d really like a picture. 1000 words.LOL making the crankshaft will be a horrendous task for a small lathe, I think I’d carefully mill as much as possible maybe eve go so far as Th mak some kind of fixture for a rotary table.  I doubt it would be strong enough to be built up. I have a good TIG welder but med issues has left me some eyesight issues.  I have a good cad program so I I think  I could model it. Maybe have it 3D printed for testing fit.  I have some blower thoughts too. Not for real supercharging but more for good fuel atomization. I’ve seen two different carb on the r2800 model so I’m beginning to think an automotive AFR gage might be useful. I’ve used then on hot rods for years so have experience with them. They aren’t as expensive as they used to be.   Keep in touch I don’t know how to add email short of direct and I’d rather not do that.

byron


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## Bentwings (Jul 19, 2020)

gbritnell said:


> Ryan,
> I have been reading this thread from the beginning and would like to make a comment or two. First, although I applaud your desire to build this thing you have no idea what is involved. Reading posts by other fellows who have built single row radials will give you an idea of the work involved in producing such and engine. Now multiply that by 28 and even for machinists with years of experience it would become a daunting task.
> Having designed several engines in my time I can tell you that there is much more to it than coming up with numbers. There's so many problems to be solved when miniaturizing that these issues alone can seem sometimes unsolvable.
> The second part of my review is that of the actual machining. As you have found out by your initial postings about the gear mountings and how to split or not split them, for someone as you say with 'rusty skills' this should not be taken lightly.
> ...


Second post on this. I’m also a Corsair fan having had a model in the family for over 60 years. Am I really that old. ....yes just watch me hobble down the street with my dog.   I’ve been a fan of the r4360 for many years. My father in law flew them as well as dive bombers during the war. I built a 1/5 Th scale model Corsair that I flew for 13 years . Traveled all over flying at different fields. I won 5 scale events so it sported 5 kill markers .LOL. I always wanted to build a new one as an F2G  but just never got around to it’ll the cowl is about 5” longer so the motor could be moved ahead to help balance it plus get rid of a couple pounds of weight. I did get to see the remaining racer one at Osgosh one year. Impressive.  The r2800 model mother is a huge project. It’s going to require all of my machine shop skills plus design for the 4360 if I decide to go that way.

byron


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## awake (Jul 20, 2020)

Bentwings said:


> Maybe have it 3D printed for testing fit.



Bentwings,

Just a heads-up (which you may already know, in which case my apologies!) - what is usually meant by "3d printing" (fused filament) can be quite good in terms of hitting size, especially for external features (not so much for internal holes unless one does some careful tweaking. However, "quite good" is not in the realm of machinist precision, so this type of 3d print is not likely to be good enough to test the fit. You might get sufficient precision from a resin-based process - I don't know, since I've not used that type of printer.

Again, apologies if I am telling you things you already know!


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## Bentwings (Jul 20, 2020)

awake said:


> Bentwings,
> 
> Just a heads-up (which you may already know, in which case my apologies!) - what is usually meant by "3d printing" (fused filament) can be quite good in terms of hitting size, especially for external features (not so much for internal holes unless one does some careful tweaking. However, "quite good" is not in the realm of machinist precision, so this type of 3d print is not likely to be good enough to test the fit. You might get sufficient precision from a resin-based process - I don't know, since I've not used that type of printer.
> 
> Again, apologies if I am telling you things you already know!


I’m well aware. Of printed part fits. The resin is better buy far more expensive. It was always nice to have something you could hold in your had when debating what to do next.

the front and rear crank counter weights were designed by a guy3-4 degrees ahead of me.   Gotta remember these motors were done and gone befor cad and cnc was even a dream. Just think, the fire control system on a ship couldn’t even be carried by air for shipping it rode the rails.the counter weights appear to be able to move slightly. There are cautions that fretting can occur so they were carefully 8nspected at over haul time. Replacing them in the field probably meant a near complete tear down. I just want to know more abou5 them and how they worked. A model engine may not need them.


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## awake (Jul 21, 2020)

Again, my apologies - I was afraid I was attempting to tell you something you already knew, but just in case ...


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## Bentwings (Jul 21, 2020)

awake said:


> Again, my apologies - I was afraid I was attempting to tell you something you already knew, but just in case ...


I


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## Bentwings (Jul 21, 2020)

I’d like to hear more about this project. I just spent the better part of two days researching and asking questions on why and how the link rod system worked. I now know that it was a cure for vibration that was caused by the weight reduction in the crankshaft.  For a model this complex feature probably won’t be necessary as the material doesn’t “scale” as far as strength is concerned. In other wards the tensile strength as well as stiffness modulus of elasticity will be the same just the parts will be much smaller and not subject to the huge power the full sized one made. You rarely se crankshaft failures in small engines like mowers and model aircraft.  Being a hot fodder adding big supercharger and a stiff load of nitro was my thing in my early years yes I destroyed a number of engines rather spectacularly but this motor would be hard pressed to make 15 hp. You see garden tractors that run for 30 plus years that have had little maintenance on them.  So strength is probably not an issue. I can see where machining tolerance might be but that hasn’t happened yet.
so I’d really like to be involved with this conversation. I to have extensive cad as well as tool making and engineering experience. This design is daunting no doubt. I haven’t really started yet as I have to close out two of my other expensive hobbies first.

if anyone is interested post a reply and maybe we can get together by email. I don’t do social media so that’s not a good way to contact me

byron


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## Bentwings (Jul 21, 2020)

Rayanth said:


> Ray-
> not derailing my thread at all =) I love to hear the stories. I've heard it said that at a META power check in a maintenance hanger, if you were standing in the wrong spot you would be struggling just to breathe...one day I hope to experience the real thing, but until then, this is what I have =)
> 
> - Ryan


I have to reply to my own reply. So here goes.

we now have decided on 4 rows of seven. Then someone says how are we going to cool this ? Som3 engineer raises his hand and says well we can just twist the whole motor. That will open up natural cooling paths. Fortunately we as modelers don’t have to deal with this.....yet.  But now you have  rotated the gangs of cylinders parallel to the crank. Fine that works until another guy says well, if we just twist the cylinders a little we can have even better cooling.......but wait, the cylinders don’t just twist about. They are not in line with the crankshaft rod journals.   So what is to be done. the piston wrist pin is now not parallel to a rod journal.   I haven’t figured this out yet. I scoured through the 4360 book but I didn’t find an answer to this , I hope it’s not some simple piece of geometry 8 missed.  I can see the rod having to turn the piston slightly but you would be asking fo rod and piston failures. My mind is scrambled b6 looking at all these drawings so I may have to just lay this out on cad and run a simulation to see if there is interference. I’m goin* to look a little further first. I sure don’t want to machine a whole crankcase only to find it won’t work.  Until later.,
byron


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## Peter Twissell (Jul 23, 2020)

Re. Movable counterweight sections:
It is my understanding that the moveable parts were added to the counterweights to correct a torsional vibration problem in the dual row and four row engines. The small amount of movement allows the effective counterweight mass to be reduced for small displacement, high frequency crankshaft torsional modes. The moving parts are suspended in oil and that provides damping, preventing the vibration mode from propagating to the extent that it caused fatigue.
See also Stockbridge Dampers.
For a model engine, the vibration modes will be entirely different. Unless the engine is expected to run under load for many hours, the additional complication of adding the moveable counterweights cannot be justified from a functional perspective.
Of course, there are some among us who would enjoy making the whole engine as close to scale as possible!
I believe the term is "masochists".


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## Bentwings (Jul 23, 2020)

After investigating thes incredible things I’m in complete agreement. I’m not sure “ scale” ones would be effective and may actually do harm. They certainly would if they came apart!  Scale is nice but “invisible scale” is not my thing.


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## Bentwings (Jul 23, 2020)

I also looked up the stock bridge dampers but again most of us simply could not afford the labor to even think about this. my experience in hot rod R.C  warbirds has shown that simply adding a little material solved the vibration problems. Even my tuned pipe exhaust systems suffered some vibration issues but it was not a big deal to add a bit larger coupler to the pipe and make a bit thicker material to the exhaust flanges.   Should I build a 27 cyl radial I’ll leave the movable dampers off until testing is complete. It will be enough work just getting it all together. From what I’ve seen so far these radials run pretty smoothly as they are.


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## Bentwings (Jul 23, 2020)

I’ve spent the better part of two days chasing info on these. The guy that was hired to fix the vibration issue said the crankshaft was too heave so in p&w plan they let him cut weight off the counter weights which helped in the overall weight. Apparently this vibration issue was noted in other applications so it was a natural to add them here he also did the same to the r2800 although I couldn’t find any pictures or other documentation.  There is note of it however. Also a note that the pivot bearings failed due to fretting Even though the bearings were carefully coated. I wonder how these were replaced in the field . It’s pretty tight in there. Maybe there was a special tool or the entire half or end of the motor was removed.  I thought cars had a lot of nuts and bolts.  In the search I also found that high g turns put excessive loads on the motor due to the gyro effect of the prop. I had never thought of that. There were a number of cases where prop had problems that caused the entire motor to be ripped off. The crankcase and motor mounts were strengthened to fix this issue. My son’sRCP 51  tore the prop hub up and nearly ripped that motor out before I got it stopped. Tore up a $30 prop and a$150 spinner. R.C. models aren’t cheap either. I’ve seen a number of radials on models but they run pretty smooth compared to to two stroke gas motors.  That P51 has a 5.8 cu in two stroke advertised hp is around 6-7 .  It definitely makes that. It will squash the gear strut all the way down under full power. 45+ pounds thrust.


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## Bentwings (Jul 23, 2020)

Bentwings said:


> I’ve spent the better part of two days chasing info on these. The guy that was hired to fix the vibration issue said the crankshaft was too heave so in p&w plan they let him cut weight off the counter weights which helped in the overall weight. Apparently this vibration issue was noted in other applications so it was a natural to add them here he also did the same to the r2800 although I couldn’t find any pictures or other documentation.  There is note of it however. Also a note that the pivot bearings failed due to fretting Even though the bearings were carefully coated. I wonder how these were replaced in the field . It’s pretty tight in there. Maybe there was a special tool or the entire half or end of the motor was removed.  I thought cars had a lot of nuts and bolts.  In the search I also found that high g turns put excessive loads on the motor due to the gyro effect of the prop. I had never thought of that. There were a number of cases where prop had problems that caused the entire motor to be ripped off. The crankcase and motor mounts were strengthened to fix this issue. My son’sRCP 51  tore the prop hub up and nearly ripped that motor out before I got it stopped. Tore up a $30 prop and a$150 spinner. R.C. models aren’t cheap either. I’ve seen a number of radials on models but they run pretty smooth compared to to two stroke gas motors.  That P51 has a 5.8 cu in two stroke advertised hp is around 6-7 .  It definitely makes that. It will squash the gear strut all the way down under full power. 45+ pounds thrust.


I don’t quite understand stand what limits  travel on these. There are no dimensions on the patent drawings.


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## Bentwings (Jul 23, 2020)

Rayanth said:


> Well, I promised (threatened?) that I would start a WIP for my probably long-running design process for a scale Pratt & Whitney R-4360.
> 
> For anyone curious, the R-4360 is considered the largest piston engine to ever go into production for airplanes. It was used on a variety of aircraft at and after the end of World War II, and while thousands were manufactured, most were scrapped when the military no longer needed them due to the introduction of the jet age. Few remain, and fewer still are still flying. Most are in museums as static displays, many were even cut away to show the interior workings.
> 
> ...


i too have a strong interest in the motor as well as building the metal scale model. I’ve also looked into plastic fabrication. Even 3D printing. The man I chatted with indicated that he could do as much of the assembled cad model as I wanted. He said something about the set is that he can control adjacent surfaces so getting it apart would not be too difficult he said making parts on a tree like model parts was a waste of a lot of material in the branch tabs that is more common to molds so that sounds encouraging.

now I just have to sit down and creat solid works models them assemble them in an assembly. He said that’s all he needs. Then he could give an estimated cost.


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## mayhugh1 (Jul 23, 2020)

Have you seen this:





__





						Pratt R-4360 Build
					

Hello, Here is a link to my site showing progress on a Pratt R-4360 It's a slow project but I keep plugging away on it. Follow the link for up dates. http://www.nyemachine.com/pratt_whitney_r4360.php




					www.homemodelenginemachinist.com
				




The first post has a link to the builder's website that may be of interest.

Terry


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## Bentwings (Jul 23, 2020)

Rayanth said:


> Well, I promised (threatened?) that I would start a WIP for my probably long-running design process for a scale Pratt & Whitney R-4360.
> 
> For anyone curious, the R-4360 is considered the largest piston engine to ever go into production for airplanes. It was used on a variety of aircraft at and after the end of World War II, and while thousands were manufactured, most were scrapped when the military no longer needed them due to the introduction of the jet age. Few remain, and fewer still are still flying. Most are in museums as static displays, many were even cut away to show the interior workings.
> 
> ...


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## Bentwings (Jul 23, 2020)

I’m a Corsair enthusiast too. I’ve had a model in the family for over 60 years.
at one point I built a 1/6 model fo the F4u-1d  not much difference just opinions I think. This was built before everybody had one. I tried to follow and scale it off a Bunker Hill squadron. I was at an event and an elderly gentleman came over and said he really liked my model but there was an error in the markings. Turns out it was his group. So I did to send me pictures and I’ll repaint it. So Idid. He met me at another even5 and was just floored as it was exactly like his group. I had him come out and be my spotter and crewchief while I flew the demonstration. I don’t think I’ve ever seen anyone that thrilled. We took pictures and exchanged them through the mail.  I built this plane well before they became ho hum attractions at model meets especially this size.  Interesting fact no one in the club would help fly it as it was a very striking and large model. I had not flown for years but had talked at length with my father in law who flew them during the war and afterwards. He always sail use lots of rudder when you take off so my first flight I had full right rudder in before it left the ground. It kinda slide around the first left turn until I let up on the rudder. I flew it for 13 years. I drill have my log book. It’s over “ thick double sided pages. I broke a few parts hear and there but no crashes.   I was going to make it into an F2G which would only have entailed adding few inches to the nose and a different air scoop. And a couple inches to the vertical stabilizer. I won five scale events so I had five kill markers on it. But I never did.if 8 ever built another I certainly would. I was fortunate to see the red and white racer fly at Osgosh, and the sound of that 4360 still rings in my ears.  It’s a very complex. Model. There are some nice kits out now  super expensive. Probably $10 grand for the plane and $7-8 for the Moki 400 radial.  Prop is several   hundred more.  I’ll build a motor before the plane just to run at events.  Just for the enjoyment of doing it.  
anyway I’m going to get Solid works fired up and make som minor  changes to the home screen.


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## Bentwings (Jul 24, 2020)

I was part of a bunch of scale warbird modelers for awhile. We tried to make our planes as close as possible. My constant thing was panel lines. As normally done on models in fully size would be terrible. If you look at the vintage planes you can see the removable pieces but even 20-30 feet away they nearly disappear. Just look up close next time you can and you will see there is less gap than cars have even today. Anyway I needed a gun sight on the Corsair that kinda looked scale. I had numerous pictures too so one night I just started making dome thing that looked real.it in reality was terrible, but at an event one judge side it was remarkably realistic.!  I somet8mes kept a towel over the cockpit so people couldn’t see it.  It had some wire like things like battery or power connection a goofy looking screen with crosshairs and a couple circles.... all pure imagination but many liked it . So some times if it looks scale maybe it is.

back to the crank. It’s going to be what actually balances according to standard practice. It’s going to be tough enough to make in the first place. I can invision trying to remove excess metal from s finished crank after the fact. It may require a special fixture just to hold it. I haven’t got that far yet so I’ll have to deal with it when the time comes. Hopefully dorm cad pictures will show up her.

byron


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## Bentwings (Jul 24, 2020)

mayhugh1 said:


> Have you seen this:
> 
> 
> 
> ...


im really glad there are others interested in an operating model of this engine.. I searched far and wide but only found some minor attempts. Not even a plastic model. Other than outline stuff. I found that Ltggo actually made a model of it but it was never released as there weren’t the 10, 000. Interests in it to make it a production model.
I found I have to reconfigure my cad since the computer update. My lap top can’t handle the program at all. I should have made an offer on my son’s laptop but it was just to9 much money.  I don’t have my computer on the internet to avoid hacks and virus invasion. I’ll be able to export to a memory stick and jpeg to my iPad I think. I’ll have to see maybe I can get a better printer too. The heat index is 99 deg going to over 100 tomorrow. Just got in from afternoon walk with m6 dog. It’s hot and sticky. The grass is wet still from morning dew.


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## Bentwings (Jul 27, 2020)

Rayanth said:


> *Crankshaft, Revision 0*
> 
> After reading all of the fun language that is a patent, two sayings came to mind. One, I've heard a few times in the various places I've been reading about machining engines. The other is a fairly popular one. Nike's "Just Do It", and "Start with a chunk of metal, and machine off anything that doesn't look like a [insert part, in this case crankshaft]"
> 
> ...


I ve now spent a full week everyday looking and studying this motor-engine. I happened to run into an old friend I ran dragster with. NHRA in their constant missing the things that brought fans to the races ended the top gas dragsters these had to run pump gas or the new race gas. We ran this class for a number of years then the twin engine cars arrived. They would have needed some new changes but not elimination of one of the greatest fan pleasers these looked like a big diesel was getting ready with billowing black clouds of exhaust. We had to run very rich idle as there was no accelerator pump in the fuel injection. If you didn’t the motor would sneeze on take off. 
well so the idea of coupling the motors came up we already had a new coupler just for this and I had a second motor all ready to go. So thinking after the fact I thought it might be possible to couple two 7 cylinder radials back to back. You would need reverse rotation cams and ignition firing order but those are not hard to do. Modern cars use a flex plate only 1/8” thick to handle hundreds of hp. So maybe a 1/16” or even thinner flex plate made from 4130 sheet readily available from race car shops work for this. After all most of these radials only make 6-7 hp each. Looking at the real 4360 crankshaft it looks like it was married to the 7 cylinder crank at the center main bearing. It would still require a new center bearing but it’s within building process. Once I get some dimensions I’ll look further into this.  I welcome any comments.


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## KellisRJ (Jul 28, 2020)

dmac said:


> They are an impressive engine.



We had one, non running, at my A&P school. I used to drool over it .


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## Master (Jul 29, 2020)

I remember the 4360's.  Often heard C-124 crews radio that they were sending an engineer into the wing to perform maintenance or inspections during flight.   We once were diverted in flight to escort a C-124 with 4360's that had an engine fire enroute to Kwajelin.  We could see the glow miles before we caught up to them.   With only three of their engines going we had difficulty slowing down in our Navy VC-118 with R2800's.  All turned out well fortunately.


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## Bentwings (Jul 29, 2020)

Master said:


> I remember the 4360's.  Often heard C-124 crews radio that they were sending an engineer into the wing to perform maintenance or inspections during flight.   We once were diverted in flight to escort a C-124 with 4360's that had an engine fire enroute to Kwajelin.  We could see the glow miles before we caught up to them.   With only three of their engines going we had difficulty slowing down in our Navy VC-118 with R2800's.  All turned out well fortunately.


I read an account of a flight engineer crawling out in the wig to replace a burned out generator. Bag of tools and a big generator. Must have been an ordeal even then. Terribly noisy.


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## Master (Jul 29, 2020)

The C-124 was a huge airplane.  I have heard similar stories.  I think the number two and three engines were accessible in flight.  Not sure of the two outboards.  The C-124 was a real Air Force workhorse.  Pretty slow though.  On occasion we could see them flying below us.


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## Bentwings (Aug 11, 2020)

Rayanth said:


> Well, I promised (threatened?) that I would start a WIP for my probably long-running design process for a scale Pratt & Whitney R-4360.
> 
> For anyone curious, the R-4360 is considered the largest piston engine to ever go into production for airplanes. It was used on a variety of aircraft at and after the end of World War II, and while thousands were manufactured, most were scrapped when the military no longer needed them due to the introduction of the jet age. Few remain, and fewer still are still flying. Most are in museums as static displays, many were even cut away to show the interior workings.
> 
> ...


I would really like to correspond with you on this project as I have a keen interest in the 4360 to an as a model. . I can give you an email address if you like just add request to this post

byron nelson


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## Bentwings (Aug 11, 2020)

Rayanth said:


> Well, I promised (threatened?) that I would start a WIP for my probably long-running design process for a scale Pratt & Whitney R-4360.
> 
> For anyone curious, the R-4360 is considered the largest piston engine to ever go into production for airplanes. It was used on a variety of aircraft at and after the end of World War II, and while thousands were manufactured, most were scrapped when the military no longer needed them due to the introduction of the jet age. Few remain, and fewer still are still flying. Most are in museums as static displays, many were even cut away to show the interior workings.
> 
> ...


I to have a Pashto also interest intert in this engine. I would enjoy trading email and thoughts. Post if you would like to participate. I’ll try and watch here daily
byron


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## Bentwings (Aug 12, 2020)

Bentwings said:


> I to have a Pashto also interest intert in this engine. I would enjoy trading email and thoughts. Post if you would like to participate. I’ll try and watch here daily
> byron


Once again I’ll add some of my interest and dealings. I built a 1/5 give or take scale model of a Corsair. f4u-1d. At the time I debated whether to make it an F2 G . It would have allowed adding about an inch to the nose. Which would have been easy just by moving the cowl forward. I hsdnot completed it at the time so I was unsure how much nose weight it needed or where to put it. It had a very nice blend of radius just behind the cowl that I think really helped reduce drag. I say this as it was considerably faster than the zero of the same scale and every bit as fast as the bearcat.  Adding the inch rudder extension would have helped  handling too. I didn’t know this at the time as big scale Corsairs were not popular then.  I finally ran across a guy with the exact same plan set but he had done the conversion. He had a slightly more powerful engine however being a semi pro drag racer I managed to wring out more power out of my motor than Mose at the time. His plane had more gap around the cowl so the cowl flaps were more out in the breeze. I was into fluid dynamics then at my job so I did do some analysis of this.  I was the only one using this software where I worked so I didn’t have anyone to challenge my results. Directly. Another guy had a Sea Fury of the same scale and in a simulated pylon race I couldn’t get away from him but he couldn’t pass me either.  Thinking back had I left the 3 pounds off and re radiused the nose of the fuselage. I think the speed would have been even better. The plane weighed 38 pounds so 3 pounds would have been very significant.   The plane flew very much like the full size lots of right rudder on take off. Interesting ly in talking to my father in law who flew thes during the war noted a special flaf setting for combat. He said he never really understood the theory of it but it did allow very high degree turns. I added a flap setting to simulate this . One of the scale manuvers required in scale flight demos in contests was a very high g sustained turn. Full size hav special instrumentation for this. It enabled the Corsair to out fly the zero under exacting conditions Other than zoom and boom. I practiced with this quite a bit and won 5 events so became the club “ace”   The scale zero was not even in out league once I got this down. Pilot turns were spectacular with my extra speed. I never entered the warbird pylon races but it would have been competitive I feel. I flew this plane for 13 years before retiring it due to my health issues. It still exist in my son’s closet. Anyway I always wanted to try the bigger engine as I was sure I could coax more power than most out of it but they were just too expensive then.
I recently noted that the 4360 began experiencing bearing failure after high g turns so it was something else to add to this “major engine. It apparently was solved but not really put to the test in high performance fighters.
I have some ideas on the crankshaft construction since I don’t think the model could develope the dynamics of the full size as the relative strength of it doesn’t really ”scale”. A model just couldn’t develope the kenitic energy by vibration the way the full size did.
I’ll have plans in a week or so for the 18 cyl so I’ll start cad models from them an work in parallel with the 28 cyl. Model. It’s very complicated in model size let alone manufacture or build it. A scale plastic model is my dream for shop” for now. My. Hodgson will probably have to black my calls as he knows more about thes than I’ll ever forget.

Byron.


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## Bentwings (Aug 13, 2020)

Bentwings said:


> Once again I’ll add some of my interest and dealings. I built a 1/5 give or take scale model of a Corsair. f4u-1d. At the time I debated whether to make it an F2 G . It would have allowed adding about an inch to the nose. Which would have been easy just by moving the cowl forward. I hsdnot completed it at the time so I was unsure how much nose weight it needed or where to put it. It had a very nice blend of radius just behind the cowl that I think really helped reduce drag. I say this as it was considerably faster than the zero of the same scale and every bit as fast as the bearcat.  Adding the inch rudder extension would have helped  handling too. I didn’t know this at the time as big scale Corsairs were not popular then.  I finally ran across a guy with the exact same plan set but he had done the conversion. He had a slightly more powerful engine however being a semi pro drag racer I managed to wring out more power out of my motor than Mose at the time. His plane had more gap around the cowl so the cowl flaps were more out in the breeze. I was into fluid dynamics then at my job so I did do some analysis of this.  I was the only one using this software where I worked so I didn’t have anyone to challenge my results. Directly. Another guy had a Sea Fury of the same scale and in a simulated pylon race I couldn’t get away from him but he couldn’t pass me either.  Thinking back had I left the 3 pounds off and re radiused the nose of the fuselage. I think the speed would have been even better. The plane weighed 38 pounds so 3 pounds would have been very significant.   The plane flew very much like the full size lots of right rudder on take off. Interesting ly in talking to my father in law who flew thes during the war noted a special flaf setting for combat. He said he never really understood the theory of it but it did allow very high degree turns. I added a flap setting to simulate this . One of the scale manuvers required in scale flight demos in contests was a very high g sustained turn. Full size hav special instrumentation for this. It enabled the Corsair to out fly the zero under exacting conditions Other than zoom and boom. I practiced with this quite a bit and won 5 events so became the club “ace”   The scale zero was not even in out league once I got this down. Pilot turns were spectacular with my extra speed. I never entered the warbird pylon races but it would have been competitive I feel. I flew this plane for 13 years before retiring it due to my health issues. It still exist in my son’s closet. Anyway I always wanted to try the bigger engine as I was sure I could coax more power than most out of it but they were just too expensive then.
> I recently noted that the 4360 began experiencing bearing failure after high g turns so it was something else to add to this “major engine. It apparently was solved but not really put to the test in high performance fighters.
> I have some ideas on the crankshaft construction since I don’t think the model could develope the dynamics of the full size as the relative strength of it doesn’t really ”scale”. A model just couldn’t develope the kenitic energy by vibration the way the full size did.
> I’ll have plans in a week or so for the 18 cyl so I’ll start cad models from them an work in parallel with the 28 cyl. Model. It’s very complicated in model size let alone manufacture or build it. A scale plastic model is my dream for shop” for now. My. Hodgson will probably have to black my calls as he knows more about thes than I’ll ever forget.
> ...


I’m sorry for my poor spelling. I have a medical condition that leaves me with double vision . So typing is extremely difficult. I have to squint some times and even closing one eye doesn’t help.  In the shop I have to be very careful too. 
thanks
byron


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## SmithDoor (Aug 18, 2020)

in past and think how a two cycle wood worked.
Today they are building very large ship engines using 2 cycle. 
Fewer parts almost twice the power per cylinder.

Dave


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## Bentwings (Aug 19, 2020)

I suppose with 18 cylinders going up and dow you would have a relatively even vacuum. However gas carbs depend on the strong vacuum pulse to pull fuel from the tank.there have been many two stroke radials made from two stroke rods and pistons so it might work. It’s a lo5 of work making a crankcase plus making the crankshaft would be an issue too. Most small engine like rc models have pressed together cranks often with a roller bearing at bothe ends. So a pressed crank would not be out of the question just a lot of precision work for an unknown engine
OShad a 5 cyl for awhile sail makes a nice 3 cyl radial that’s glow operated.
probably the best thing would be to model it up in cad so you could see issues befor they happen.  You could purchase most cylinders but they get expensive fast.  Nant have very tight fitting pistons some even stick at top dead center until warmed up.
i just got my Hodgson plans for the 18 cylinder engines.there is a lot of work in these engines. I’ll know more about it as I get into modeling the parts. The drawings are pretty clear. There are just a lot of individual parts that have multiples. Just making the fixtures and special tools are a major undertaking.  I dropped the plan set when the page clip came apart. Just picking up the pages an sorting them correctly took my entire lunch time and I live alone. Fortunately as language became pretty corse.LOL


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## Steamchick (Aug 20, 2020)

Big ship engines that are 2-strokes are Diesel (often using heavy oil, that is solid at room temperature and needs melting!). Thus they use turbo-charging BLOWERS to force the air into the cylinders, not crankcase pumping, and also have high pressure direct fuel injection... so no carburetors. 
Incidentally, Carbs do not use crankcase vacuum directly to draw-in the fuel. The crankcase vacuum draws in the air, which develops a partial vacuum (actually this should be described as sub-atmospheric pressure) in the venturi because the air as accelerated and faster flowing gas has a lower pressure... Thus the normal air pressure pushes the fuel upwards from the float chamber into the venturi to mix with the flowing air. Small Aero-engines just have a needle valve as the air is fast enough through the small inlet port to draw-in the fuel from the tank at almost the same level as the jet.
Sorry to be pedantic about this, but you made a supposition about the Ship engines that seemed a bit "off-beam. I'm sure you know a lot more about the small Aero-engines than I do so I'll accept any corrections gladly! 
K


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## SmithDoor (Aug 20, 2020)

It some I look at and wonder why very small or very large.

They made a few truck engines 2 cycle.

It seems like a great place for cycle to replace large aircraft engines is 2 cycle.

Dave



Steamchick said:


> Big ship engines that are 2-strokes are Diesel (often using heavy oil, that is solid at room temperature and needs melting!). Thus they use turbo-charging BLOWERS to force the air into the cylinders, not crankcase pumping, and also have high pressure direct fuel injection... so no carburetors.
> Incidentally, Carbs do not use crankcase vacuum directly to draw-in the fuel. The crankcase vacuum draws in the air, which develops a partial vacuum (actually this should be described as sub-atmospheric pressure) in the venturi because the air as accelerated and faster flowing gas has a lower pressure... Thus the normal air pressure pushes the fuel upwards from the float chamber into the venturi to mix with the flowing air. Small Aero-engines just have a needle valve as the air is fast enough through the small inlet port to draw-in the fuel from the tank at almost the same level as the jet.
> Sorry to be pedantic about this, but you made a supposition about the Ship engines that seemed a bit "off-beam. I'm sure you know a lot more about the small Aero-engines than I do so I'll accept any corrections gladly!
> K


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## Bentwings (Aug 20, 2020)

Steamchick said:


> Big ship engines that are 2-strokes are Diesel (often using heavy oil, that is solid at room temperature and needs melting!). Thus they use turbo-charging BLOWERS to force the air into the cylinders, not crankcase pumping, and also have high pressure direct fuel injection... so no carburetors.
> Incidentally, Carbs do not use crankcase vacuum directly to draw-in the fuel. The crankcase vacuum draws in the air, which develops a partial vacuum (actually this should be described as sub-atmospheric pressure) in the venturi because the air as accelerated and faster flowing gas has a lower pressure... Thus the normal air pressure pushes the fuel upwards from the float chamber into the venturi to mix with the flowing air. Small Aero-engines just have a needle valve as the air is fast enough through the small inlet port to draw-in the fuel from the tank at almost the same level as the jet.
> Sorry to be pedantic about this, but you made a supposition about the Ship engines that seemed a bit "off-beam. I'm sure you know a lot more about the small Aero-engines than I do so I'll accept any corrections gladly!
> K


Small  stroke engines use the crank case vacuum pulses to operate a fuel pump. This allows the chainsaw to operate in any position.sorry if I wasn’t clear on this. Some model engines us this to operate a pulse controlled fuel pump . I’ve use$ these many times on very high performance model engines. Another way to get fuel to the carb is to take pressure from the exhaust to the fuel tank thus forcing fuel to the carb. The needle valve then controls mixing as you noted. I’ve never put a pressure gage on to measure it but bu without it the engines don5 run very well. It’s usually one of the first things to check if there is poor performance on these rngines. Gas carbs have a port or separate line to the crankcase. By having very slight forced fuel feed these small engines can be very reliable..  yard equipment are good examples. Tillitson And Waldron carbs are used extensively.
super sizing these probably wouldn’t work very well. There are already many automotive carbs that woto fine until, emmisions become an issue then electronic fuel injection takes over. There are aftermarket systems that work fine.

but that’s all getting away from big two strokes. There are some pretty big snowmobile engines as well as the super bike engines.there are still a few two strokes around but the Eli has made the four strokes king. Just look at the new outboard marine engines. They are extremely powerful and reliable.


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## SmithDoor (Aug 20, 2020)

The truck and ship engines uses a super charger for the air. The crankcase is oil bath.
Far fewer parts than a 4 cycle engine.

The first 2 cycle used a oil bath crankcase and a cylinder for air intake and one the compress the air for combustion. Still few parts over same size 4 cycle engine.

Dave




Bentwings said:


> Small  stroke engines use the crank case vacuum pulses to operate a fuel pump. This allows the chainsaw to operate in any position.sorry if I wasn’t clear on this. Some model engines us this to operate a pulse controlled fuel pump . I’ve use$ these many times on very high performance model engines. Another way to get fuel to the carb is to take pressure from the exhaust to the fuel tank thus forcing fuel to the carb. The needle valve then controls mixing as you noted. I’ve never put a pressure gage on to measure it but bu without it the engines don5 run very well. It’s usually one of the first things to check if there is poor performance on these rngines. Gas carbs have a port or separate line to the crankcase. By having very slight forced fuel feed these small engines can be very reliable..  yard equipment are good examples. Tillitson And Waldron carbs are used extensively.
> super sizing these probably wouldn’t work very well. There are already many automotive carbs that woto fine until, emmisions become an issue then electronic fuel injection takes over. There are aftermarket systems that work fine.
> 
> but that’s all getting away from big two strokes. There are some pretty big snowmobile engines as well as the super bike engines.there are still a few two strokes around but the Eli has made the four strokes king. Just look at the new outboard marine engines. They are extremely powerful and reliable.


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## Bentwings (Sep 1, 2020)

This thread is pretty old but extremely interesting.

to the original thread starter,,,,afte4 reading your interest and beginnings I’d strongly recommend obtain8ng a set of Lee Hogson’s 18 cylinder model. He has a very good knowledge of building the model as well as a lifetime machinist.  Exile not exact scale he has created a great expandable design. He has als explored many alternat solutions to problems and many of these engines are completed and very functional.  I think along the way things dont always ”scale” exactly. Metallurgy is one I know well After 35 years of engineering and 25 years as toolmaker. I also build and fly giant scale rc warbirds. Dealing with scale factors is intrinsic with this.

do get a set of drawings to continue your quest. You may want to visit Tom maker site for some great construction and machining solutions.

byron Nelson.


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## SmithDoor (Sep 2, 2020)

I would hate to all that time in a RC plane and then fly the model.
My background is  have built and fly RC planes and a hobby rebuild old engines. My living for over 40 years was manufacturring aircraft hangar doors. 

I have always wonder why large full size aircraft have not used the two cycle engines. 
A engine like the P & W R-4360 has so many parts and if was manufacturring as two cycle it would be a lot fewer parts and lighter.
Most only  think  of two cycle as oil burning not a big  engine that does not burn oil.

Today they are using two cycle for very large ships.

Dave



Bentwings said:


> This thread is pretty old but extremely interesting.
> 
> to the original thread starter,,,,afte4 reading your interest and beginnings I’d strongly recommend obtain8ng a set of Lee Hogson’s 18 cylinder model. He has a very good knowledge of building the model as well as a lifetime machinist.  Exile not exact scale he has created a great expandable design. He has als explored many alternat solutions to problems and many of these engines are completed and very functional.  I think along the way things dont always ”scale” exactly. Metallurgy is one I know well After 35 years of engineering and 25 years as toolmaker. I also build and fly giant scale rc warbirds. Dealing with scale factors is intrinsic with this.
> 
> ...


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## Peter Twissell (Sep 2, 2020)

The Junkers Jumo engines were 2 stroke diesels - used in aircraft sizes up to the huge Blohm and Voss bomber Wiking.
Ship 2 stroke diesels are very heavy, which doesn't matter so much in a ship, but in an aircraft you need a good kW/Kg ratio.
The Jumos had respectable power to weight, but were just as complex as a four stroke, with dual crankshafts and opposed pistons.


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## Bentwings (Sep 2, 2020)

My Corsair took a while to build due to family moves. One thing many rc scale builders don’t do is research the full scale flight characteristics. They don’t always “scale exactly”but often are close. It’s easy to have more than enough power in these models so dealing with this is an issue. But as we say, that’s what the throttle is for. I could not get anyone to help fly it the first time so I flew it myself using known flight issues. They were notorious for excess York on takeoff requiring heavy rudder input especially in windy weather. I did exactly as the full size on carrier take offs with nearly full right rudder. In flight it flew very scale like. I won 5 scale events I entered in 5 different states. I flew it 13 years before retiring it to one of my sons. Who still has it. It never had a crash and only one dead stick with minor damage.   These big rc scale plans don’t take kindly to being horsed off the ground just as full size plans don’t.  Today there are corsairs with big 5 cylinder radial engines that are a real marvel to see and hear.  There are some big two stroke engines that can really haul these around.
I don’t think it would be easy to build a light enough 18 cyl engine to fly 1/4 scale model.  Maybe extensive use of unobtanium. Would do it.LOL I’m just getting started on cad model 18 cyl radial. I’ll have to finish this first before going far on the 28 cyl.cad model. There are many road blocks before even starting. I’m still learning history of development of the 4360.  I can’t even imagine the engineering hours that went into it. Just cad models will take forever.
byron


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## Cogsy (Sep 2, 2020)

I heard some reports a few years ago of ultra-light type aircraft using 'traditional' 2-stroke engines and having engine failures. What seemed to be happening was when they were descending they'd throttle back to idle and set up a descent rate, however if the descent rate was slightly too high the prop would be driven by the airflow and the engine would turn at a higher rpm than idle - but would not be receiving enough oil at the idle fuel rate to sustain the higher rpm. From what I read, generally when they went to throttle back up the engine would seize from a sustained lack of lubrication.


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## ddmckee54 (Sep 2, 2020)

That engine was built in the days when a pocket calculator would have been a 6" slide rule and a piece of scratch paper.  I've still got my 10" log-log slide rule, somewhere, and if I scratched my head long enough I could probably even remember how to use it.

I guess that's why they built full-sized mock-ups of everything.

Don


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## Bentwings (Sep 3, 2020)

ddmckee54 said:


> That engine was built in the days when a pocket calculator would have been a 6" slide rule and a piece of scratch paper.  I've still got my 10" log-log slide rule, somewhere, and if I scratched my head long enough I could probably even remember how to use it.
> 
> I guess that's why they built full-sized mock-ups of everything.
> 
> Don



that’s interesting. When I decide to go back to engineering school I had an instructor who was a marathon runner for metallurgy. He came into class and jumped on the table like it was a stepping stone and pointed to the large yellow teaching slide rule hanging over the chalk board. He look the group over then pointed to the slide rule and asked if anyone knew what it was pointing at me he said you don’t answer. I was a good 10 years senior to the class. Then again pointing at me he said explain what this is. So I did then he said find the sq roof of 9. Well easy enough but it took a few seconds to recall the moves. He very good now let’s get into metallurgy.  He often had us do presentations on our work in front of the class then gave very pointed critiques of them. You had to be prepared in his class. I did get an A in the class and had many hours of“teaching
“ my findings  and experiences in lab work. It was probably the best class I had in the 5 years at school. Standing in front of the group answering pointed questions and occasional challenges was extremely valuable in the following years in my engineering career.


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## SmithDoor (Sep 3, 2020)

it was German they ever thing complex Junkers Jumo 205 - Wikipedia
This is how simple a two cycle diesel






Dave


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## SmithDoor (Sep 3, 2020)

I have know idea why the Germans made a simple engine complex .
Yesterday I posted a photo how simple a large 2 cycle are done.
The photo just showed today.

I had a Detroit 2 cycle engine in a large forklift it work great.

Dave



Peter Twissell said:


> The Junkers Jumo engines were 2 stroke diesels - used in aircraft sizes up to the huge Blohm and Voss bomber Wiking.
> Ship 2 stroke diesels are very heavy, which doesn't matter so much in a ship, but in an aircraft you need a good kW/Kg ratio.
> The Jumos had respectable power to weight, but were just as complex as a four stroke, with dual crankshafts and opposed pistons.


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## ddmckee54 (Sep 4, 2020)

I always thought that the Germans over-engineered everything in WWII, then I saw what Rolls-Royce did with the Merlin.  I forget how may thousand parts it takes to build just one engine.  It ALMOST makes the R-4360 look simple.

Don


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## Peter Twissell (Sep 4, 2020)

There are a number of reasons behind the Jumo design. Among them were the lack of high octane fuel in WW2 Germany and the shortage of nickel for making valves and seats.
The Jumo is a highly efficient uniflow engine. In my opinion, it was an appropriate solution to the problem.


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## Bentwings (Sep 14, 2020)

Rayanth said:


> Ray-
> not derailing my thread at all =) I love to hear the stories. I've heard it said that at a META power check in a maintenance hanger, if you were standing in the wrong spot you would be struggling just to breathe...one day I hope to experience the real thing, but until then, this is what I have =)
> 
> - Ryan


it appears that it’s been awhile since you last posted so many of ure waiting on your progress.

i spent many years building scale model rc aircraft. Along the way I discovered that many things don’t “scale” very well and are often mis scaled in terms of reality. For example aircraft panel joints or lines. There are few openings in panel that are 1/8”this means at 1/4 scal the opening or gap could be 1/32”. That’s barely a scratch on a 1/4 scale model. I used a sharp exactly knife and flex straight edges to draw scale skin joints. My big Corsair was to be shown as a fresh out of the factory plane thus a nice shiny blue finish. I put as many lines as I had accurate measurements  of. I viewed many CAF Corsairs over the country from 20 feet even flying ones had almost no panel lines. Even cowl line were barely visible front gear doors had leather hinges so I used scraps from a fine leather purse for mine. model pilots were very hard to find . Any preprinted one looked like dead pilots so I had my artist wife paint mine with me as the model. Operating details just don’t scale well. You can have man6 pictures of cockpit instruments but they just never look right.
now to real hard ware . Engines don’t come anywhere near scale . Most of these planes were grossly overpowered. My father in-law flew the planes so I constantly asked about flying them. They could take off in 60-80 feet under the right conditions. Our flying field was about 200 feet so more than enough for a real one to take off. Bu5 to be scale looking it took pilot skills to keep it on the ground going straight with full right rudder. Full throttle was not scale at all. To be scale you had to just nurse the throttle barely clearing the weeds. The first event I entered I scored high in scale appearance an near perfect in flight performance. We had to do at least 5 scale maneuvers using the field centerline. The final high speed pass strafing run had both USMC vets Who were judges bailing out of their chairs They said except for no real bullets flying about that it was just like the beaches.  It’s nearly impossible to scale a carrier landing but a nice 3 point from almost stalled won the event.
I would suggest you get Lee Hodgson’ plan set  and use his bore and stroke numbers. This will get you relatively easy dimensions and easier parts to make. He shows many fixtures and tools required. It’s no small project even with these.   The crankshaft will be a real project in itself. Again a lot of this does not “scale” easily. Just putting the crankcase parts together so the bearing bores all line up will be a trick. It’s a long ways to get the pieces to fit as precisely as needed. It might be best to align hone them. Not all automotive shops have hones to do this. Even line boring is a long ways.  You might be able to do it on a Bridgeport with some special supports. Things are pretty small in this scale. Valves and seats are tiny plus it takes a lot of them....all the Same.
please keep us posted on progress.


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## Bentwings (Jul 1, 2021)

Rayanth said:


> Ray-
> not derailing my thread at all =) I love to hear the stories. I've heard it said that at a META power check in a maintenance hanger, if you were standing in the wrong spot you would be struggling just to breathe...one day I hope to experience the real thing, but until then, this is what I have =)
> 
> - Ryan


I may have already replied but I couldn’t find it if so then ignor me. I also ask forgiveness for spelling as I have a double vision issue that makes typing extremely difficult. Sometime a misspelled word completely changes the note . I do proof read with a magnifying glass but even that aid I still miss things.

so. I’ve built many rc scale warbirds. My handle should give a clue to my favorite.

your engine task is a daunting project. I don’t think anyone has built or even presented a cadd model of this engine. It was on my list but even with access to solid works I have stayed away.  I do have the Hobson 18 cyl plan set and have reviewed it page by page. Then given thought to your project.  When scaling models one thing come out quickly. That is not everything scales perfectly nor functionally. Cadd makes numeric things relatively easy. But when you transfer this to an operating machined engine it may not work out as you planned.

starting with the crankshaft is where I’d start too. Tom from Tom’s maker site has done a very nice job of creating and building an 18 cyl. Radial. On his cadd and cnc. Reading and looking at the Hobson drawings shows some great ideas as. The issue I see is that the engine may take many assembly steps and pressing the crank together may cause issues.  Looking at Whitesbook you can see the complexity of it.  Those movable counterweights may not be necessary as the vibration probably won’t be present as the material and proportionate strength, may not scale.  Hobson only uses a 1.000 bore. So the piston is already designed as are the rings and assembly fixture. I looked at the two piece rod but I don’t think there is room enough room for a strong enough bolt without changing other things. The 18 cyl. crank has a splined insert crank pin. In real life it must have been a huge project to remove and replace this. I don’t know the torque needed. To get around this I look back on some drag racing issue we had with narrowed rear ends befor custom axels were made. A large axel was cut off near the flange then turned down to fit in a hole bored through the flange. This provided a bearing surface. Then the flange and axel were sssembled. Some were press fit then welded. The best were pressed then drilled on the hole line for a dowel,pin and welded. These were incredibly durable in the era.  So for the new radial a slip fit could be made using the same feature it would be removable for assembly and disassembly. Modern two stroke small engines use press fit cranks.a hard prop strike or crash udualy knocks them out of slighnment or bends them. But some careful machine work would probably work on this model.  Inventer may have some stress analysis available.  I did a lot of this in industry with some expensive software. I even had vibration software. It’s been a long time since I even looked at my notes on this . I’d try it my self if I ever get out in the shop again. Doctor would probably commit me if he knew what I’m doing as it is.  I’m not supposed to play any sports not even tiddlywinks . I ventured out to the batting cage . By using an eye patch I was able to hit a few pitches but I’m out of the game for good.

anyway. I just wanted to stay with you on this. I hope you can put up some screen shots as you go.

hood luck as you go on.

byron.


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## cds4byu (Jul 2, 2021)

Boston museum of science has a cutaway R4360.  It's a beautiful piece of engineering art.  I could look at it for hours (but not so my wife....)

If you want to see the real thing, that's one place to go.

Carl


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## vederstein (Jul 2, 2021)

A quick Google search says that Lycoming's XR7755 was the largest radial engine.  It never got past the experimental stage though.

From the website:

"The U.S. military’s naming conventions provide some info about the XR-7755: X stands for experimental; R indicates a radial cylinder configuration; and 7755 is the approximate displacement in cubic inches. That’s not a typo: 7755 cubic inches, 127 liters. There were 36 cylinders laid out in four rows of nine, each one with a 6.375-in bore and a 6.75-in stroke, displacing 215 cubic inches per cylinder."

Link:









						Lycoming’s Leviathan: XR-7755, the Largest U.S. Aircraft Engine of World War II
					

Lycoming, supplier of engines to Auburn, Cord, and Duesenberg, has an additional claim to fame: builder of the XR7755, the largest U.S. aircraft engine of World War II.




					www.macsmotorcitygarage.com


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## JLaning427 (Jul 3, 2021)

Not to tangent away too far from the OP's topic, but....

The Lycoming referenced above is likely the biggest radial for US aircraft use, but the Russians had some big inline radials in marine service after WW2.  42, 56, and 112 cylinder versions of these engines saw service in various high speed craft.  There is (or was, not sure if they are still active) a German tractor pulling team (Dragon Fire) using one of the 42 cylinder engines converted to alcohol. 


Here is an article on the engines:








						Yakovlev M-501 and Zvezda M503 and M504 Diesel Engines
					

One of the largest aircraft engines ever built, the 42-cylinder Yakovlev M-501 was modified into the Zvezda M503 marine engine. A further redesign created the 56-cylinder Zvezda M504.




					oldmachinepress.com
				




Excerpt from link:
Zvezda also coupled two 56-cylinder engines together front-to-front with a common gearbox in between to create the M507 (and others) engine. The engine sections could run independently of each other. The 112-cylinder M507 displaced 23,361 cu in (383 L), produced a maximum output of 10,453 hp (7,795 kW) at 2,000 rpm, and produced a maximum continuous output of 9,863 hp (7,355 kW) at the same rpm. The engine was 22.97 ft (7.00 m) long and weighed 37,699 lb (17,100 kg). The M507 had a fuel consumption of .378 lb/hp/h (230 g/kW/h) and a time between overhauls of 3,500 hours for the engines and 6,000 hours for the gearbox.

Zvezda engineer Boris Petrovich felt the 56-cylinder M504 engine could be developed to 7,000 hp (5,220 kW), and the M507 (two coupled M504s) could be developed to over 13,500 hp (10,067 kW). However, gas turbines were overtaking much of the diesel marine engine’s market share. Today, JSC (Joint Stock Company) Zvezda continues to produce, repair, and develop its line of M500 (or ChNSP 16/17) series inline radial engines as well as other engines for marine and industrial use.

Now back to the discussion....


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## Bentwings (Jul 4, 2021)

Being a big drag race in my younger days and driving my supercharged Streetrod som 34k mile with no blower issues, I have looked at model engine supercharging. The only really successful mfg of supercharged engines is Conley. I don’t really know how much boost his positive displacement blower makes. Probably not a lot. It serves as a good fuel atomizer just as the street blower I had did. The issue is it’s hard to get much air flow into it and super tight clearances are required. Aluminum tends to fall up in a heart beat especially when hot. Gas is not a good lubricant. 
the other issue is spinning it in its best envelope. Radio enginges have used turbo and centrifugal blowers for a long time. Even these have to be designed around close tolerance and highspeed rotation. I did look into compounding an two speed systems bu gear boxes an bearing get expensive fast and machine work gets beyond hobby shop capability. So it still becomes fuel atomization and supplying enough air. The Hobson enginges have a centrifugal blower but it’s mainly for distribution and atomizing. But doing much different than shown gets complicated fast. The 28 cyl is complicated enough to keep most awake at night as it is. I don’t think it would be a good idea to try and use exhaust to spin a turbo, it may over heat exhaust valves and seats. Then you run into the same issues we had years ago in drag racing. Burned pistons and dropped valve seats. It would not be fun repairing this in one of these radials.it looks was but remember this is very miniure model there are lots of finely machined parts so you could make a big mess. I think s dump would be a nice project. There are small engine Fumo available but cost might make them impractical. The farm tractor synod are pretty simple to duplicate. A little math could give realistic readings.

byron


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## petertha (Jul 4, 2021)

Bentwings said:


> The Hobson enginges have a centrifugal blower....



I suspect you mean Hodgson engines


			Ageless Engines


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## Bentwings (Jul 7, 2021)

Yeah your right it’s my vision again. Hogs on has an impeller that looks like a centrifugal blower. It rotates at crank speed so does more mixing than pressure. I looked at s planetary gear box to over drive it but it’s just not really practical to do this in my mind. I don’t have the technology to develop much of a centrifugal multi stage system. It would probably be more difficult than the engine itself.   I even thought of using model airplane electric ducted fans but it still takes a lot of engineering and testing. I not equipped to do this now. It was hard enough to create a supercharged Streetrod that was efficient and durable.


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## Peter Twissell (Jul 8, 2021)

My big radial (2.3 litres) has exactly the arrangement you describe, with an impeller normally driven at crank speed, to act as a mixer, with a planetary gear which can be engaged to drive it at 4 X crank speed, in the hope that it might generate some boost.


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## Bentwings (Jul 8, 2021)

Peter Twissell said:


> My big radial (2.3 litres) has exactly the arrangement you describe, with an impeller normally driven at crank speed, to act as a mixer, with a planetary gear which can be engaged to drive it at 4 X crank speed, in the hope that it might generate some boost.


I’m glad someone else sees this correctly. There is nothing wrong with it. Domes what is supposed to. With a compound planetary you cold get considerably more rpm. That’s what I had in mind. Now adding a model airplane electric ducted fan to the intake would add considerable amount of intake air at some pressure so you might begin getting boost. This is beginning to look like the full scale. I stopped her as I just don’t have the test equipment to evaluate progress.you can begin to see what p&w engineers tan into. Next is inter-cooling. It’s easy to see why the p47 became so full of ducts-and exhaustpipes.my supercharged Streetrod had intake air temps of 200 deg F. A friend has nearly the same combination and same temps. Runs great but an inter cooler would help. They are another 3~3” thick so blower high becomes ridiculous. Boats use them however. Free cold water.
I doubt you could get more than a couple pounds boost even with fine  engineering  just too hard to make precision enough parts at this scale. Nice idea of your gearing 
however.
Byron


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## Peter Twissell (Jul 8, 2021)

I ran a rudimentary test of my blower, using my milling machine to drive the planetary gear. At the mills maximum of 1800 rpm and the blower at 7200 rpm, the 1kw mill motor was struggling, but it was shifting a lot of air (against no back pressure).
I'll be happy if it makes enough boost to offset the extra load it imposes on the engine. It's worth it for the impressive howling sound alone.
Pete.


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## Bentwings (Jul 8, 2021)

Peter Twissell said:


> I ran a rudimentary test of my blower, using my milling machine to drive the planetary gear. At the mills maximum of 1800 rpm and the blower at 7200 rpm, the 1kw mill motor was struggling, but it was shifting a lot of air (against no back pressure).
> I'll be happy if it makes enough boost to offset the extra load it imposes on the engine. It's worth it for the impressive howling sound alone.
> Pete.


That’s funny. Probably why the my Streetrod 6_71blowr whistled pretty good when you got after it a bit. The funny car you could hear in the driver seat. If you couldn’t the blower need real stripping.

byron


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## Bentwings (Jul 8, 2021)

Bentwings said:


> That’s funny. Probably why the my Streetrod 6_71blowr whistled pretty good when you got after it a bit. The funny car you could hear in the driver seat. If you couldn’t the blower need real stripping.
> 
> byron



Spelling error again. 
I meant re stripping putting new Teflon seal strip in it. I’m surprised it took that much power to spin.have to look at the crank to see if it could stand more stress from compounding planetary. I don’t know how much power these motors make. I’ve heard up to 10 hp.Rc model radials can make 15 to almost 20 spinning 32 inch props.I have a 5.8 cu in 2 stroke that can make well over 45 pounds thrust w it’s a 23x14” pitch 2 blade prop. I’m looking forward to see your progress on this big motor. 

byron


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## Bentwings (Jul 9, 2021)

As a result of your interest in supercharging I’ve begun searching the internet for more info.. 
it doesn’t take long before you begin to see how complicated a simple thought can become. P&w probably found this also.with a huge engineering staf and equally large machine shop facilities they gained knowledge quickly. Systems became vey complicated. See p 47 details. Then with all the new oxygenated air how to get fuel into in the proper ratio became an issue.this is where the first throttle body fuel injection came to be. So far as modelers this is about where we are the carb is no longer an easy device to work with. There are small fuel injectors but an electronic management system is needed. More complications. You could go to mechanical fuel injection similar to what we use on top fuel drag racers. They are not exactly as easy as they used to be either.  Various sensors are required . You could add an 02 sensor as I used on my Streetrod. But they add a couple hundred dollars right away. They do work. It was key to making my supercharged hot rod about as close to a daily driver as you can get.  We don’t have much but a series of props and tachometer to work with in our complicated engines. .

mph boy I have really open the can of worms. I’ll stop here unless y’all want to continue. We spen hours doing this stuff in the hot rod shop. Sometimes things work, some times the day is taken up with trying to figure out why we have a blown up engine.LOL
Buron


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## lohring (Jul 9, 2021)

Liquid seal pumps would be a simple solution to a low rpm, high efficiency supercharger.  It has built in intercooling and could use fuel as the seal.  They run forever as vacuum pumps.  See  Find Out How Liquid Ring Vacuum Pumps Work | Nash

Lohring Miller


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## Bentwings (Jul 9, 2021)

lohring said:


> Liquid seal pumps would be a simple solution to a low rpm, high efficiency supercharger.  It has built in intercooling and could use fuel as the seal.  They run forever as vacuum pumps.  See  Find Out How Liquid Ring Vacuum Pumps Work | Nash
> 
> Lohring Miller


You are right. I had forgotten about high vacuum pumps. I do remember the special oil was extremely expensive. These were used in the aerospace R&D area I worked in to create space type vacuums. We had a one cubic yard vacuum chamber in a dry room. It took forever to pull it down.the sides and door were flat so we’re subject to deflection due to high vacuum. I was tasked with calculating then verifying this.while not particularly difficult math it was much more difficult to prove by measurement. Sealing took special o rings purchased from Parker.the pump and motor made so much noise they had to be enclosed in a separate room extension. Guess who had to research and present quotes for exotic sound dealing materials. My fancy in the day computer worked overtime with this stuff. It was nice in a way as I got premium top of the line software and many training trips. I’m actually glad I don’t have this now. My mind has enough to do just keeping up here LOL.I’m now being pressured to get dictating software.  I get all these health care offers so I asked about a secretary but insurance won’t pay for that…….yet. I want to go out in the shop but my doc says he will commit me if I do. Maybe I should just bring the shop to my living room.

byron


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## lohring (Jul 10, 2021)

It doesn't take a special liquid.  Dental vacuum pumps use water.

Lohring Miller


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## Bentwings (Jul 10, 2021)

lohring said:


> It doesn't take a special liquid.  Dental vacuum pumps use water.
> 
> Lohring Miller


You are noting water. Water is death in very high vacuum chambers.
Also I was in a govt sponsored military research facility there were only limited number of times you could go in and out of the dry room per shift. Less than 5%rh.you never got sick there but dry skin and dry eyes were issues we dealt with. Pure lithium and some extremely active electrolytes used in lithium batteries was common. You never touched anything with bare hands or any bare skin. The common joke was you wash hands before going into the bathroom as well as after. Then you had to spend dry out time in the air lock doorway. Both ways.You learned a new meaning to clean and dry working in this environment.


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## lohring (Jul 11, 2021)

The vacuum pump I'm talking about is in a dental office where solids as well as liquids are suctioned up.  Similar pumps are used on submarines where a variety of substances get sucked out of the bildge.  The pump doesn't care.  If you need a clean output, use another style pump.  As a compressor some fuel spillover could be controlled to operate the engine as well as to form the seal.  I'm not aware of this use.  I think it would be an interesting experiment.  Dental vacuum pumps have a controlled inflow of water that flushes out the seal area and gets pumped out.  The same could work in a compressor.  

Lohring Miller


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## Bentwings (Jul 24, 2021)

Rayanth said:


> *Piston, Revision 0*
> 
> Just worked 13 days straight, so I apologize for the lack of updates on this front. Today is a rare day off, before I go into another 12 days straight, and I'll have enough consecutive weekends to tell the company they can't designate me on the weekend of the 9th and 10th, so I can go to the (very nearby) Arlington Fly-In.
> 
> ...


Above was a post about driving the Hobson impeller. It seemed to me that the power required seemed very high considering the size of the unit(blower) or mixer what ever you want to call it. I had considered something ver similar early in thinking of modeling the 28 cylinder. I’ve had supercharged streetrods for many years using the gmc roots superchargers. They do take a lot of power to drive very fast. Eventually the more or less stop pumping air above 8500 blower rpm. We ran them much faster but the idea was to get max boost as quick as possible to get the car moving off the line. This did work but high gear when the hemi way Erving high the bioethics was just along for the ride. As driver I had plenty of time to look around for the competition and sometime watch him drive on by.LOL.  The solution was to reduce the fuel flow quickly at some given rate as there just was not enough air to mix with it. The big scoop on the blower helped with ram air effect some but not something we did much about as there were only a few options available and we had the largest available. The plan worked as we won our share of races especially 1/8 mile ones. Leaning it out each run produced better speeds and elapsed times. We just didn’t go far enough fast enough. Races won an pay at the end of the day was more important than setting records. We had our dhare but could have done better. .
So to continue. I considered multi staging and coumpoundkng centrifugal blowers but gear trains and gear boxes began being a concern. In order to better understand planetary gear sets and the possibility of adding supercharging to these cool engines I ordered a tamia planetary gear model. It just came today but I haven’t ventured into assembly or modification yet. This kit even includes a small electric motor do you can drive your creation. It was inexpensive so I though I could always get another and build a nice compound planetary drive based on this model. It really surprised me at how small the parts are. It shows a needle nose pliers but I done thing even Snsp on Tools has one this tiny. I have a reasonable education in automatic transmission in cars and we had a 3 speed manually operated. Trans in the racer so taking them apart and reassembling thenm is not an issue.  All the plastic parts can be purchased in metal if you shop around. Ratio calculations are readially available on the internet.  Mounting a carb on the intake side the blowing into another blower might be asking for a fire or mini explosion. I just saw this very thing on the internet so I think making a rotary valve carb like the old glow engines had would be best as could use a pressurized fuel tank it would operate much like our race care fuel injection. It’s called mechanical FI I to would take some careful machine work and some good o rings but they are available. Regulating fuel pump pressure might be a bit tricky but by running on alcohol rather than gas you have a much wider air fuel ratio to work with. Overly rich or lean usually doesn’t make much difference.alcohol is readily available even at Home Depot. It’s a bit pricy but many horrid shops have it too even E85 would work fine I think.
I’m going to work with this micro miniature thing and maybe get another so I can compound it easily. Worst care the gears can be drawn in cad an 3 d printed pretty reasonably.
Anyway I’d like opinions and maybe more testing results. I saw a blower made from PVCpipe pieces a. Purple days ago. I may have saved the site I’ll have to look.

byrom


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## Bentwings (Aug 11, 2022)

Rayanth said:


> . I would suggest 3 d printing parts as you go  the effectbiscthevtime saving . If you make a mistake you don’t have to worry much about the time spent machining a mistake it about like what was said when we first started 3 d modeling even in wire frame .it was easy to just push delete and start over . Scrapping a week work in the machine shop was harder to explain  lusvitvgivesvthevsbilitybtobtestvfitvandcassemble  You may miss or rethink something and just print new . You may want to consider a 3 d printer of your own  costcwisectheybhsce come way down in price and set up pretty easily .  Things like superchargers don’t scale very well even compounded it’s hard to get the air to just flow.   I might suggest a modification  for you . Create a pair of gmc type diesel blowers and either stack or plumb then compounded.  There are a number of already modeled ones  I think in grab cad   Centrifugal and turbos just don’t work well  a number of these have been made an most can’t inflstva plastic bag
> *Crankshaft, Revision 0*
> 
> After reading all of the fun language that is a patent, two sayings came to mind. One, I've heard a few times in the various places I've been reading about machining engines. The other is a fairly popular one. Nike's "Just Do It", and "Start with a chunk of metal, and machine off anything that doesn't look like a [insert part, in this case crankshaft]"
> ...


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