# different piston design for IC engine



## camnefdt (Feb 10, 2013)

I am yet to build my first anything on a lathe or milling machine, but am a super technically minded young individual driven by mechanics and general engineering.

At the moment i am busy designing out a long term project for one day when i have the experience and money to invest in such a project.

The question i have is, has anybody considered using a more modernized design for a piston over the good old straight long cylinder?

something along the lines of this. . .




This one is from an F1 car but the concept is there.

So has anybody tried one of these for a scaled IC or even considered doing this before?


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## stevehuckss396 (Feb 10, 2013)

I think myself I will stick to the long cylinder. Stuff like you show are designed for minimum friction and flat out performance. They are also designed to last one race and get tossed out. As my engines are not designed to go real fast I will most likely stick with what I see in production engines that are designed to run for hundreds of thousands of miles.


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## MuellerNick (Feb 10, 2013)

F1 budgets are so low, the have to save material wherever they can to cut costs. 


Nick


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## wildun (Feb 10, 2013)

camnefdt said:


> Best to take one step at a time, If you are trying to build something radical, (or just something ordinary) then start at the beginning and learn the arts of machining, casting metal etc. etc. - if these basic fundamentals  are  absent from your experiences then you will quickly lose interest and go nowhere.
> However I do understand your enthusiasm ( much like I was really) but don't let that enthusiasm die by having impossible ambitions which are beyond your reach, at least which are way beyond your reach at the moment.
> 
> Good luck with your projects and please don't lose your enthusiasm - you could of course prove me wrong though and if you do, then I'll accept that!


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## Swifty (Feb 10, 2013)

I can see that type of piston works, but goes against design principles where the piston should be at least as long as it is in diameter, preferably longer. This is to stop the piston cocking in the cylinder.

Paul.


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## camnefdt (Feb 11, 2013)

you are 100% correct in saying that this is purely a performance 'mod' piston. But in recent times, similiar designs (not as narrow) are being used in production performance cars purely for the fact that they weigh less and have less friction.

wildun
i dont plan to take shortcuts to achieve my goal, will start off with basics and make my up from there, i just love learning about new things mechanically and as a challenge to myself, am designing out a purely performance V8 to be actually used in a RC car (a project that is still many many moons away , but an eventual goal)

I am going over every single inch of the engine with a fine tooth comb to come up with the BEST possible engine with crazy performance and reliability. 

Swifty
As a rule 'they' say as long as your skirts of the piston are roughly half your piston diameter there should be no cocking in the cylinder. they are also done with the top of the piston perfectly round, and down at the skirts it is slightly oval to help stop the cocking in the cylinder and for expansion.


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## Lew Hartswick (Feb 11, 2013)

stevehuckss396 said:


> . They are also designed to last one race and get tossed out. .


For a couple years now the engines have to last for two races plus the practice and 
qualifying.  (F1 the only auto racing) 
   ...lew....


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## trumpy81 (Feb 11, 2013)

You have to remember that F1 engines are at operating temperature before they are even able to be started. They would disintegrate if started from cold, such are the tolerances of the components.

Such a piston in a model engine could easily 'twist' within the bore, and this is often the reason behind the extended skirts. Although in a lot of model engine designs I have looked at, I'm sure their pistons could easily be reduced in height without too many ill effects. Any offsetting of the crank to the cylinder center line will normally use an extended piston skirt to combat the increased piston to cylinder pressure. The premise being that the load is spread over a larger area and with greater moments of inertia.


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## wildun (Feb 12, 2013)

CAMNEFDT,
Desigining something of your own is a great project, designing the best solution for achieving "crazy performance and reliability" in a model (RC) car possibly would not be by using a V8 engine! - I think you will find that a fairly high performance single cylinder two stroke engine and properly designed exhaust chamber would beat it hands down, both in the power to weight ratio, the outright power and the cost, (unless cost is no object). 
Then, in the reliability stakes..... what if the engine seizes and/or breaks one of those rods you so lovingly fashioned, or bends the beautiful big long crankshaft you spent a month making?  ... in the case of the two stroke, probably a reasonably simple repair and back in business!
Point is, what do you want? - to be a draughtsman/designer and let your mind roam free? to have fantastic performance - with a model V8??, To have a very reliable and competitive model car- with a model V8? - to be a competent machinist to make all this come about? 
That's what I meant when I said  earlier, "one step at a time" and I'll add a bit more "everything starts with a dream, but for the dream to come true it needs to be tempered by reality".

Still, no harm in dreaming - I always did, but I have also  faced all the realities (and disappointments )through my forty something years in engineering, - don't lose the dreams, but pace yourself and remember, learn only one discipline at a time - but keeping the others in sight - good luck and do well.


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## Goldflash (Feb 12, 2013)

I would buy a copy of "Modern Engine Tuning by A Graham Bell".  Read up on piston design , Bore to Stroke Ratio , Connecting Rod Ratio to Piston Stroke. 
Forged pistons versus cast pistons , port design and cylinder block design and crankshaft design camshafts etc etc etc . This book is a bible if you are building a 4 stroke or modifying a 4 stroke engine.   Better to make a single cylinder engine that you can keep making changes to so you are able to achieve quantifiable results first me thinks.


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## hi speed scrap (Feb 12, 2013)

Here is a design you might like to look at, its cast, and has a hollow crown
for piston cooling. If u look closely at the underside of the crown u can
see the oil hole, sorry about poor pics.
From 600hp diesel, done 1.4 mil k's this one
http://s1356.photobucket.com/albums/q729/dieselfx1/?action=view&current=HPIM1391_zps7c1d1ede.jpg

http://s1356.photobucket.com/albums/q729/dieselfx1/?action=view&current=HPIM1392_zpsa6415be7.jpg

Dave.

Oooops! wrong link, well they are there anyway.


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## Till (Feb 12, 2013)

A high performance V8 engine with the necessary singleplane crankshaft will lack the beloved bubbling sound.


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## camnefdt (Feb 12, 2013)

Hi guys thanks for all the replies and criticism, its always valued by such a novice as me. 

would just like to point out that i am aware that something engineered to the level of the F1 piston, is waaaaay overboard for a scale model V8. I was just using that as a reference point to ask the question whether anybody has tried using these type of pistons as apposed to the regular old straight cylinder. 

please also be aware that i will only be attempting the V8 in no less than 10 years and in that time will be doing lots and lots of experimenting and tinkering on single cylinder and other various IC engines to test out different designs and see what works and what doesn't.


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## wildun (Feb 12, 2013)

camnefdt said:


> in that time will be doing lots and lots of experimenting and tinkering on single cylinder and other various IC engines to test out different designs and see what works and what doesn't.


 
That's the story, - good on ya mate!


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## Niels Abildgaard (Feb 12, 2013)

Here is an idea for a piston/conrod assemblycompared to a more conventional type


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## camnefdt (Feb 13, 2013)

niels

thats exactly the type of idea i had, nothing overly engineered, but reduces the weight and friction of the piston, allows for better response on revving the engine and possibly better performance too. 

have you at all tried incorporating  that design into an engine as of yet?


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## FannBlade (Feb 13, 2013)

Hope to see your engine build soon and good luck with your venture.
F1 engines are the Holy Grail of engineering....my absolute favorite Motorsport. 18000 rpm and staying together defies all inertia logic.


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## canadianhorsepower (Feb 13, 2013)

FannBlade said:


> Hope to see your engine build soon and good luck with your venture.
> F1 engines are the Holy Grail of engineering....my absolute favorite Motorsport. 18000 rpm and staying together defies all inertia logic.


 
specialy a four strokes:fan: 
but the stroke is only 1.6 inch and bore max at 3.8


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## camnefdt (Feb 13, 2013)

FannBlade said:


> Hope to see your engine build soon and good luck with your venture.



thanks, i am only 21 and start my career on Friday  from there i plan to save up and get my first lathe or milling machine within a year a 2. Once i get that, nothing will be able to hold me back as i build up a nice workshop and begin messing around with various engines and other projects iv got on mind


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## Entropy455 (Feb 13, 2013)

Just a bit of discussion- 

F-1 engines run high compression, at very high rpm. Rules of F-1 racing limit engine displacement. Thus engineers are forced to make modifications elsewhere to increase power output  via increased rpm, increased compression, increased volumetric efficiency, etc. Extreme rpm operation requires minimizing rotating mass, minimizing reciprocating mass, and minimizing friction-surface areas. The baby piston skirt will minimize mass and cylinder-wall drag forces, however the tradeoff is accelerated piston skirt wear, and the design requirement of larger rod-stroke ratios. Also note that light-weight engine parts are usually the first to blowout when an engine falls slightly out-of-tune (aka detonation).

There was a rather heated discussion a few years back (on another forum), with regard to aluminum connecting rods for racing applications. At the time, aluminum rods were becoming a popular upgrade for street-driven (and occasional drag-strip driven) muscle-car engines (454s, 455s, 460s, etc). Heres the problem - aluminum will work-harden and fatigue with use - and with enough cycles, aluminum rods WILL ultimately fail  as many weekend racers have discovered by punching holes in their engine blocks at half-track. Another guy reported throwing a rod simply by starting his aluminum-rod engine in freezing weather.

The original thought was that because Top Fuel engines utilize aluminum rods, they must be the best choice for a street/strip engine also. The problem is that Top Fuel rods are aluminum because they can absorb the traumatic impulse events of burning nitro-methanol, whereas 4340 rods cannot. It is the work-hardening properties of aluminum that makes the rods able to absorb the trauma  and is also why Top Fuel rods are replaced every 3 to 5 races. . . .

Point being  just because a technology is good for F-1 race cars and/or Top Fuel dragsters, does not mean its good for all race engines, or basic engine building in general.

The old checker cabs were notorious for running 500,000 to 1,000,000 miles between engine rebuilds. Why? The answer is because of well designed heavy-duty parts that are moving relatively slowly.

Ive got a marine diesel engine with 14,000 hours on it, and its still running strong. Ask yourself this question  what would the power returns be, or fuel-efficiency returns be, by installing baby-skirt pistons into this marine diesel? Answer: it would likely be virtually immeasurable power returns on the dyno, and the engine would certainly not last for 14,000 hours of heavy-load usage.


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## trumpy81 (Feb 13, 2013)

Entropy455 Your tales of http://www.homemodelenginemachinist.com/members/entropy455the Aluminium rods etc... take me back to the '70's when most of the local hot rodder's thought big carbs were best. There was so many sick running V8's and inline 6's getting around at that time is was quite funny.

Your point about trade offs is also well taken.


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## Niels Abildgaard (Feb 15, 2013)

camnefdt said:


> niels
> 
> thats exactly the type of idea i had, nothing overly engineered, but reduces the weight and friction of the piston, allows for better response on revving the engine and possibly better performance too.
> 
> have you at all tried incorporating  that design into an engine as of yet?



Hello Camnefdt

It was just an CAD experiment. 
Somebody published drawing for a new Mercedes Smart Diesel engine, Diesels have much higher maximum pressure (push in rod) and not very great piston accelerations in top dead centre (pull in conrod) and the scheme could be wortwhile for singlecylinder genset.Not F1 where piston and rod will fly apart very soon.
The two conventional looking pictures are based on the Mercedes engine.
Happy Study and have You mastered to calculate piston accelerations yet?.
They are obscene in formula one.


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## Goldflash (Feb 15, 2013)

Have a look at this file for working out Piston acceleration at different crank angles/ Rpm etc  
You can play with the Inputs like Stroke , bore , and Rpm . It does not calculate piston side thrust at different crank angles but its a fun programme to play with 
I just wish I could remember where I got it from. 

View attachment Piston Acceleration.xls


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## stevehuckss396 (Feb 15, 2013)

I'm sure another thing considered by engine builders is the ease at which an old style barrel piston is made.


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## camnefdt (Feb 15, 2013)

hi guys, again thanks for all the replies 

just as a reminder, i am in no way trying to recreate the F1 piston in a scale engine with the same type of revving and speeds and everything, all i am trying to do is find a more efficient alternative to what is conventionally used.

such as these











these are average run of the mill pistons of which the one set was used in buiks almost 30 years ago as the standard production piston. but they are the kind of style and design that i am interested in trying for my engine design.

Please don't get too focused on the F1 aspect of the photo that i posted in my first post, it is just the first photo i got to for an example and i completely understand that it is an extreme in terms of the design of the piston.

some of the aspects i am looking at achieving for my engine is up to a max rev of 8000 RPM, a more 'exotic' sound to the V8 (using a flat plane crank) and i want to attempt using fuel injection with super charger. 

I am in no way trying to achieve the performance of the F1 standards.


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## petertha (Feb 15, 2013)

camnefdt said:


> ...thats exactly the type of idea i had, nothing overly engineered, but reduces the weight and friction of the piston


 
I wonder what the friction gain would amount to by simply lopping off a lower portion of the piston skirt? I would think the bulk of the piston OD is running moreso in clearance to cylinder ID anyway vs. the contact area of ring set responsible for sealing? (ie much closer fit, more rubbing contact therefore friction). Ive never really seen a proportional friction breakdown map quantified like: 60% rings + 40% piston = 100% friction, but it would be interesting. 

I'm familiar with ringless pistons in (RC) high-perf applications, buts thats a different kettle of fish. Although, there may be some learnings there too... 'extra' piston material can't be shaved too far off certain miniumums before the piston shapes deform under load/temp & the magic clearances are lost very quickly. Interesting subject, good luck.


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## Entropy455 (Feb 15, 2013)

Drag force on the piston skirt is not a significant factor. There are much more appreciable design challenges in getting a V-8 to safely turn at 8000 rpm. For example, achieving a proper dynamic balance of the rotating assembly, and the ability to dampen crankshaft torsional harmonics. Also, keeping the lifters in contact with the cam-lobes, and preventing the valves from bouncing off their seats (aka valve float) requires high valve spring pressures. This means running case-hardened cam-lobes and lifters, with a positive-pressure oiling system, or running an all-out roller cam with case-hardened needle-bearing rollers.

Normally you&#8217;ll snap a connecting rod, long before you pull a wristpin out of a piston.

Piston failure is often the result of running lean, or running too much spark advance, or inadequate fuel octane, etc - - - not from running a piston with a heavy-duty skirt.


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## Entropy455 (Feb 15, 2013)

A bit of engineering discussion:

Piston friction force is equal to the normal force along the friction surface (cylinder wall), times the friction coefficient of the joint.

The friction coefficient is pretty much a function of the lubricating oil. Note: piston manufacturers are now applying coatings onto piston skirts. These coatings are more of a wear-preventative measure, than a friction reducing measure. The friction coefficient has to do mainly with the shear forces within the oil film that is preventing metal-to-metal contact.

The normal force is primarily a function of rod-stroke ratio. Or more specifically, the smaller the rod-stroke ratio, the greater the piston will press into the cylinder wall. Thus longer rod-stroke ratios will directly decrease cylinder wall friction, and shorter rod-stroke ratios will directly increase cylinder wall friction.

Decreasing the piston skirt area will directly decrease the overall surface area of the oil that's preventing metal-to-metal contact. This means less friction, which means less power losses. It also however places higher shear-stress pressures on the remaining oil film, resulting in higher fluid-bearing stress on the piston skirt, and the cylinder wall. This directly increases the rate of cylinder wall and piston skirt wear. It also results in higher oil-film temperatures, causing accelerated thermal breakdown of the oil hydrocarbon chains.

Increasing combustion pressures will also increase the normal force along the cylinder wall. More cylinder pressure means more torque. It can be shown that crankshaft torque is ultimately a direct result of cylinder side-loading during the power stroke.

Increasing engine RPM will also increase cylinder wall drag forces, as the cylinder wall must &#8220;force&#8221; the connecting rod to change directions - as is stated within Newton&#8217;s Laws of motion.

Point being &#8211; there are literally dozens and dozens of engineering examples where engine longevity is directly sacrificed in the pursuit of increased &#8220;per-cubic-inch&#8221; power production.

On a related note: I&#8217;ve seen guys purchase 350 cubic inch small-block chevy engines, and then proceed to dump thousands of dollars into aftermarket performance parts. In the end, they have an engine that will make 1.25 horsepower per cubic inch - but it is octane sensitive, it runs with a narrow & elevated-rpm power-band, and it has elevated stress on pratically every moving part.

Whereas a wise man would purchase a 1970s Caddy 500 engine, do a low-budget stock-type rebuild, and make more overall horsepower, with a bone-crushing torque curve. . . . Saving thousands of dollars, and running for tens of thousands of additional miles between rebuilds. . .. . .

Point being - if you are not displacement limited, increase cubic inches first &#8211; then evaluate power-adding engine design modifications. . . . If you want to turn 8000 rpm "just becasue" then go for it. Otherwise slow things down, and stick with heavy-duty parts.


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## wildun (Feb 15, 2013)

Just a couple of points, correct me if i'm wrong.
Could the low profile pistons be a help by enabling the use of longer conrods which will in turn reduce the sidethrust on the piston at mid stroke and also help to keep engine height to a minium when using these longer rods? 
Also 8000rpm doesn't sound enough to obtain reasonable power from a model V8, after all the usual racing V8 ( big engines) today must surely be approaching that figure! 
As an example, the little Honda four stroke 125cc 5 cylinder and the 50cc two cylinder GP motorcycles of the mid nineteen sixties revved to 22000 rpm, (quite extreme of course) but true nonetheless.


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## Lakc (Feb 15, 2013)

The internal combustion engine in design and practice. Charles Fayette Taylor

http://books.google.com/books?id=mX1-OJBQ6ngC&printsec=frontcover#v=onepage&q&f=false

Read it, believe it, but dont outbid me on ebay when I finally find a copy with money in my pocket.  I have had the pleasure of a copy at my disposal from a good engineering library in the past. Its indispensable when you want to get serious about designing your own engines. Since it was published it has been the bible of the industry.

It mentions piston speed being the basic design anchor for any engine power requirement. This makes sense, as its mentioned piston assembly friction is almost half of the whole engine, and speeds are generally 5-15 meters second.

This is the piston for my last engine. Its a compromise of the new and the old. Dia .980" and height about .6, 15degree dome with three .040 reliefs. I had plenty of room so no need to cut the skirt, but in a nod to more modern design I did move the rings and pin as high as possible. There are so many things to handle with a new design you dont tend to be so revolutionary with everything at once, but I do try to be evolutionary.


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## wildun (Feb 16, 2013)

Great book, but really way over my head in many of the chapters. 
However I do remember someone suggesting that in GP (motorcycle again) it would be better to base the classes entirely on mean piston speed! - thus having many different machines and engine capacities competing fairly against each other. 
Of course this didn't happen, but I guess there was some wisdom there - even if it does blow my theory of 8000 revs not being high enough for a model V8 engine!  - depends on the stroke/bore ratio used I suppose.


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## camnefdt (Feb 16, 2013)

Lakc said:


> The internal combustion engine in design and practice. Charles Fayette Taylor
> 
> http://books.google.com/books?id=mX1-OJBQ6ngC&printsec=frontcover#v=onepage&q&f=false
> 
> ...



thats an awesome looking book  definitely worth tracking down 

Have you tried your piston out in an engine? how does it perform?


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## canadianhorsepower (Feb 16, 2013)

> [Read it, believe it, but dont outbid me on ebay when I finally find a copy with money in my pocket./QUOTE]
> 
> Hi Jeff, thanks for that book reference, I just ordered one
> here is a link where many used one are availlable, enjoy
> ...


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## Lakc (Feb 16, 2013)

camnefdt said:


> thats an awesome looking book  definitely worth tracking down
> 
> Have you tried your piston out in an engine? how does it perform?


They havent broken yet


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## canadianhorsepower (Feb 16, 2013)

[quoteThey havent broken yet 
	

	
	
		
		

		
		
	


	



__________________
Jeff 
][/quote]
do you have pictures or specs of the motor your running these in
thanks


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## Lakc (Feb 17, 2013)

Here is the build thread from a few years back. 

http://www.homemodelenginemachinist.com/f31/homebrew-boxer-twin-prototype-10465/

After switching to spark ignition I am still trying to get it running. Lack of spare time has been the biggest factor.


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## cfellows (Feb 17, 2013)

Can't see any reason it wouldn't work.  I could see that a short piston might be useful if you are building an engine with a really short stroke.  However, unless you have a compelling design criteria that requires it, there is generally no good reason for a short piston (and cylinder).  

Chuck


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## Alec Ryals (Feb 20, 2013)

trumpy81 said:


> You have to remember that F1 engines are at operating temperature before they are even able to be started. They would disintegrate if started from cold, such are the tolerances of the components.
> 
> Such a piston in a model engine could easily 'twist' within the bore, and this is often the reason behind the extended skirts. Although in a lot of model engine designs I have looked at, I'm sure their pistons could easily be reduced in height without too many ill effects. Any offsetting of the crank to the cylinder center line will normally use an extended piston skirt to combat the increased piston to cylinder pressure. The premise being that the load is spread over a larger area and with greater moments of inertia.



  How does the crank bore get off center from the cylinder bore?? and how does this increase the compression.
Alec Ryals


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## windy (Feb 21, 2013)

On another ME forum I was asking a similar question about using a short skirt piston.
My engine is a 14cc two stroke flash steamer powering a tethered hydroplane (122.91mph over 500metres) and I am always trying to find that extra mph.
Having seen a JRM (Jawa) 499cc speedway piston with a very short skirt I wondered if I could do something similar to my piston to reduce friction?
My flash steam engine is a two stroke with a poppet valve to let superheated steam in and uniflow ports to let the exhaust out.
It has a narrow Dykes ring that if I used a short piston would it rock too much and destroy its seal?
11,000rpm under load, 15,000rpm with no load.
Piston and ring are cast iron running in a steel cylinder liner.
I have not seen any model competition engine with a short piston and wondered why.
[ame]http://www.youtube.com/watch?v=xdeUe9JcBVU[/ame]
This is my first meeting of 2012.
All suggestions on the merits or otherwise of using a short piston welcome.

Windy


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## Till (Feb 21, 2013)

Alec Ryals said:


> How does the crank bore get off center from the cylinder bore??








Alec Ryals said:


> and how does this increase the compression.
> Alec Ryals


It doesn't increase compression. It increases contact pressure per surface area because of bigger side forces.
The piston skirt is pressed against the wall of the cylinder liner. It's sidewards.


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## jack620 (Feb 21, 2013)

Fastest steamboat I ever saw!


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## Goldflash (Feb 21, 2013)

Wow I am impressed with your Hydroplane.  Can you supply more  details on the uniflow engine and the flash steam system 
Goldflash


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## windy (Feb 22, 2013)

I decided to alter an old piston to reduce weight and friction to find any problems that might arise on the uniflow flash steam engine.
One of my local club members pointed out that when the piston is a few degrees past BDC the uniflow ports are now open to the crankcase and that oil could be lost to the atmosphere via the silencer.
After a run the boat sinks if not retrieved quickly so water could enter the crankcase by the silencer.
So I have an old barrel and piston and will alter it to the new shape and run the engine up on the lathe and see what happens to the lubrication.
Modifying the piston reduced the weight by at least 1/8oz maybe more but will have to check the crankshaft balance if the test is successful.

 Windy


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## trumpy81 (Feb 22, 2013)

Alec Ryals said:


> How does the crank bore get off center from the cylinder bore?? and how does this increase the compression.
> Alec Ryals



Alec if you draw a circle that represents the crank, normally the cylinder center line would follow the vertical center line from the center of that circle.

If you then draw another line parallel to the vertical center line but some distance away from it, the second line would then be the center line of the cylinder.

I hope that makes sense?

As for compression, I didn't mention that at all?


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## trumpy81 (Feb 22, 2013)

Till said:


> It doesn't increase compression. It increases contact pressure per surface area because of bigger side forces.
> The piston skirt is pressed against the wall of the cylinder liner. It's sidewards.



Sorry Till, I didn't see your post until after I replied. Yours is a much better explanation than mine ... lol ... Thanks.


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## Alec Ryals (Feb 22, 2013)

No one makes a engine with off-set cylinders except for models.
Alec Ryals


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## Alec Ryals (Feb 22, 2013)

Hello, Are you running a westinghouse (Stuart Sirus or Sun) type engine.
Thank You
Alec Ryals


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## canadianhorsepower (Feb 22, 2013)

Alec Ryals said:


> No one makes a engine with off-set cylinders except for models.
> Alec Ryals


 
Not quite, it's a common practice on hot saws,
and some scooter


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## Lakc (Feb 22, 2013)

Alec Ryals said:


> No one makes a engine with off-set cylinders except for models.
> Alec Ryals


http://en.wikipedia.org/wiki/Desaxe

Appears a few production ones do.


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## jixxerbill (Feb 22, 2013)

Lakc said:


> http://en.wikipedia.org/wiki/Desaxe
> 
> Appears a few production ones do.


 

Must be more than can be seen in that video.. that engine will not rotate the way it looks there ?


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## Lakc (Feb 22, 2013)

Dont believe everything you read on the internet, even Wikipedia. 
While the cylinders do show desaxe, the video is not really appropriate to that page. The beauty, and downfall, of some wiki pages is that anyone can edit them.

The text citations for Toyota and VW both using desaxe engines is believable, however, and the ASE paper cited makes it rather credible.


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## aonemarine (Feb 22, 2013)

I remember seeing an old piston design that did not have a wrist pin, instead it had a ball and socket...
  That hydroplane is awsome!!  Love to see some more about it. There is nothing like it in the US that I know of.....


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## Till (Feb 23, 2013)

Alec Ryals said:


> No one makes a engine with off-set cylinders except for models.
> Alec Ryals


You are wrong. 



A good example is the very successful Volkswagen VR6 engine family.
If you are bored and willing to pass free time, please have a look at: http://en.wikipedia.org/wiki/VR6


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## windy (Feb 23, 2013)

Hi aonemarine.
If you look at the following there is a lot about my side of model engineering. http://www.onthewire.co.uk/ 

It used to be done in the States years ago but radio control has taken over. 

We have classes for shop bought engined powered hydro's and British classes for home built engines of IC and steam.

The home built ic class is over 130mph so Bob the previous steam record holder and myself are trying to beat that speed in 2013.

Tuning ideas are freely exchanged which is very good for developement. 

If you contact Hugh and Lynn on the above web site they are always interested in the history of tethered cars and hydroplanes so if there are any members that know of the States tethered cars or boats they would be interested.

Paul


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## petertha (Feb 23, 2013)

windy said:


> I have not seen any model competition engine with a short piston and wondered why. Windy


 
I was trying to remember what RC engine piston I had come across that struck me as being severley hogged out. It was the OS-FS-120 4-stroke (circa mid 80's? but dont hold me to that date). Ive pasted in some google pics of it & other 'reduced' pistons for visual reference. Some are not necessarily shortened but lets say put on a severe diet in other dimensions 

Here is a link to OS parts manuals. Hopefully you can scan accross the exploded views as a means to examine pistons & judge relative dimensions. 
http://www.osengines.com/parts/exploded-views.html


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## windy (Feb 23, 2013)

Another  type of piston to think about.


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## RonSkingley (Feb 23, 2013)

Hi Paul,

Please excuse a quick 'off topic' remark, but I'm very glad to hear there is still interest in flash steam hydroplanes.
My step father was Arthur Cockman, so I have an interest there, and I well remember Sundays at Victoria Park with my father, Jack Skingley.
I now live in Southern Ireland so unfortunately have little opportunity of visiting there.

All the best, and keep up the good work 

Ron


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## trumpy81 (Feb 23, 2013)

windy said:


> Hi aonemarine.
> If you look at the following there is a lot about my side of model engineering. http://www.onthewire.co.uk/
> 
> It used to be done in the States years ago but radio control has taken over.
> ...



Paul, I'd love to see what your hydroplane would do if allowed to free run (untethered) The tethering must introduce drag and other speed restricting effects?

As far as I know, the SSME (Sydney Society of Model Engineers) in Sydney still have tethered events for cars and boats, have you heard of them?


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## Lauri (Feb 23, 2013)

Hi.

How about this? This is the piston/cylinder group of our control line engine. 

L


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## trumpy81 (Feb 23, 2013)

Lauri said:


> Hi.
> 
> How about this? This is the piston/cylinder group of our control line engine.
> 
> L



That's an impressive looking piece of gear Lauri. I bet it performs well?


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## windy (Feb 23, 2013)

Hello Andy M,
As what happens sometimes the thread gets waylaid but on the wire has this from Sydney http://www.onthewire.co.uk/mmanls.htm

That control line engine piston and cylinder is interesting and would like to know some more about it.

Good to hear from Arthur Cockmans relative.

Paul


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## Lauri (Feb 24, 2013)

Yes, it works well. The set in the picture has been running for allmost 100 hours and shows very little wear and no carbon buildup. So, mechanically it is very good. But to work perfectly as a control line aerobatic engine, there is still a long way to go as the requirements are a bit differend. I am still playing a lot with the porting, combustion chamber shapes, timings and such.
 The cylinder/piston in the picture are made by Rob Metkemeijer, he has the serious machinery to do the bore and chrome & hone it. I do everything else that is possible with my Schaublin 102. Enclosed is some pics of my work.
 At the moment I'm busy with piston rings, I want to know wether a standard flat ring or a dykes ring is better for our use. L


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## Lauri (Feb 24, 2013)

Another picture..


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## Lauri (Feb 24, 2013)

..and the latest muffler. The engine weights 270grams + the side resonant muffler which is a little under 40g. L


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## petertha (Feb 24, 2013)

And just for something on the other side of the spectrum demonstrating&#8216;thick&#8217; pistons, this is the typical configuration for YS 4-strokes circa early 90's. On the upstroke , fuel mixture flows from the carb & enters the crank case through arotary disc valve, somewhat similar to a 2-stroke. On the down stroke thecharge is compressed above ambient like a supercharger effect (hence the benefitof more solid looking piston body).

http://www.rcmplans.com/issues/requested/content/reviews/pdf/r-rv-ys140-101997-1-1.pdf


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## trumpy81 (Feb 24, 2013)

windy said:


> Hello Andy M,
> As what happens sometimes the thread gets waylaid but on the wire has this from Sydney http://www.onthewire.co.uk/mmanls.htm
> 
> That control line engine piston and cylinder is interesting and would like to know some more about it.
> ...



Thanks Paul! It was good to see some pics of my old stomping grounds again, I'll have to keep a link to that


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## trumpy81 (Feb 24, 2013)

Lauri said:


> ..and the latest muffler. The engine weights 270grams + the side resonant muffler which is a little under 40g. L



Very Nice Lauri!!! You certainly are a very skilled machinist! Kudos for the pics!

Have you played with the venturi shapes much and spray bars?


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## trumpy81 (Feb 24, 2013)

petertha said:


> And just for something on the other side of the spectrum demonstrating&#8216;thick&#8217; pistons, this is the typical configuration for YS 4-strokes circa early 90's. On the upstroke , fuel mixture flows from the carb & enters the crank case through arotary disc valve, somewhat similar to a 2-stroke. On the down stroke thecharge is compressed above ambient like a supercharger effect (hence the benefitof more solid looking piston body).
> 
> http://www.rcmplans.com/issues/requested/content/reviews/pdf/r-rv-ys140-101997-1-1.pdf



Peter, you're a wealth of knowledge on obscure engines, where do you find all this stuff? ... 

The British used positive crankcase pressure in a similar manner for years. In fact most pre '86 Triumphs use it to increase the available torque together with the 'hemi' heads and pistons. Although they didn't use full body pistons like the YS does. I wonder if such a piston would work on my bonnie?

I bet that YS could swing a very coarse prop.

Doesn't the Dykes ring provide better dimensional stability?


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## petertha (Feb 25, 2013)

trumpy81 said:


> Peter, you're a wealth of knowledge on obscure engines, where do you find all this stuff?... I bet that YS could swing a very coarse prop.


 
Well, I cant take much more credit than middle age memory & having run the stuff in the day. YS was/is 'the name' in RC competition aerobatic (pattern) engines, first 2S, then 4S. They really set the bar for technical innovation, power & reliability. So not really obscure to that event, probably 70% of competitors  used them, the remainder OS engines & few others. Probably the same for RC heli's in the day. 'Gassers' (methanol actually) are slowly being edged out by electric drive motors, but much of that is a function of the specific event rules.

The 1.2-1.4 CI of that era ran 15-16" dia props x 12-14" pitch. I seem to recall ~2.5 hp/in3 multiples. I've been out of this scene for long time. The current YS engines are up to 1.7 CI displacement, timed ignition modules, direct fuel injection, integral shock dampening mounts... Cool stuff but $$ too.

Sorry, I can't speak to the ring design with anything useful.


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## Lauri (Feb 25, 2013)

trumpy81 said:


> Very Nice Lauri!!! You certainly are a very skilled machinist! Kudos for the pics!
> 
> Have you played with the venturi shapes much and spray bars?



Thanks. Yes, I spent last summer playing with differend venturi's . But I must say that with a healthy engine, with good thermalbalance and stabile burning process, the venturi shape shouldn't be too critical. I am working with an overly powerfull and super light engine which tends to run too cool. this kind of thermic inbalance tends to magnify the effects of certain variables, like the venturi and combustion process.
But I kind of like this approach, because it:
-allows me to find differences in processes that would be difficult to see in a healthy engine
-means that, as power is not an issue, I can build the stability up by increasing the exhaus back pressure. This means even quietet silencer.

But I really shouldn't disturb this thread with my stuff, this should be about funky piston designs.

L


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## Lauri (Feb 25, 2013)

That's how it looks like.


-12,6cc
-bore 24mm
-stroke 28mm

L


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## trumpy81 (Feb 25, 2013)

Thanks Lauri. I really like your venturi drawing it's not unlike some of my drawings from ages past. I always wanted to experiment with the venturi shapes and other things on my competition marine engines but at that time I did not have the equipment or the means to acquire it, so I never got to experiment. I had to be content with what came in the box ... lol


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