Edwards Radial 5 Build

[Brian-in-Oz]

Easy! make it out of titanium.

Hi all - a while back a friend gave me a piece of titanium bar 10'' X .750". Originally it was a hydraulic ram on the Sydney to Hobart winning yacht Wild Oats X1 which is one of the boats he works on. I must have been in an adventurous state of mind today as despite all the horror stories I had heard about machining titanium I decided it was time to put that exotic looking piece of metal in a chuck.
With sweating palms I decided the first thing I would do is attempt to cut the 5/16" X 24 thread. I had some nice HSS taps (mid taper and plug) and set about the task. First drill a hole with a I letter drill. It soon became apparent that this light weight and rather pretty metal is some tough customer. Despite using a liberal dose of tap magic as cutting fluid quite a bit of heat was generated but with a bit of patience and care a hole was drilled without delegating a spare hole in my letter drill case. Next step was to load the mid taper tap in the tailstock chuck and have a go at cutting a thread. Once again it became immediately apparent that this stuff was not remotely related to brass but non the less by repeatedly and very carefully cutting a bit and backing off I managed to get to the bottom of the hole without breaking the tap. I then finished with the plug tap with no further drama.
The big surprise was that on cleaning and inspecting the thread I would have to say that it was one of the nicest looking threads I have seen. Not the slightest sign of pickup, just a beautiful polished looking thread.
So far - so good, now to turn the nut and nose diameters. For this I used a slightly rounded nose sharp carbide insert and cut 10 thou. at a pass. While it was obvious once again that this is tough stuff the swarf peeled off cleanly leaving an excellent finish.
To mill the flats of the nut I ran my mill as fast as it would go and used a four flute HSS end mill cutter taking cuts of .2mm (my mill is metric) and sprayed CRC while cutting.
No problems were encountered and the finish was excellent and the cutter remained sharp. I was sure my ball turner would not take the stress of cutting the rounded nut nose so I did this with a coarse file first progressing to a fine file and finally polishing with carborundum paper.
And so ends my first encounter with titanium, admittedly on a small component.
Does it deserve its horror reputation? - in my opinion no.
Is it more difficult to machine than most metals I encounter? - definitely, but with solid rigid machinery and sharp tools and patience it is quite do-able.
Will I be using more titanium in future projects? - almost certainly not unless it is particularly specified - it is simply very time consuming (not to mention the cost) at least with the tooling most home shops possess.

I guess a bonus of having a titanium propellor nut is when someone asks what my Edwards Radial is made of I can say oh! titanium -uh- and a bit off other stuff.

Cheers all - Brian th_bs

 

[xjs]

Yo Brian --

Many thanks for the detailed information on pipe production. It's now in the same file as all your other excellent advice on How To Cook A Proper Radial.

Don't think I'll ever be able to top a titanium prop nut though. A platinum fuel tank? Diamond-studded motor mounts?

I know when I'm beat.

Best,

m

 

[Brian-in-Oz]

Hi all,

Tinkering continues in the quest of hopefully getting the Edwards to run. With Michaels permission I have plagiarised his design for an engine mount and have tried to keep dimensions with weight in mind so that it could actually be used in an aircraft. Wether this will actually happen is debatable as I am petrified at the thought of the engine coming into an uncontrolled contact with terra firma but you never know.
Next step is to mount the engine and go over it, adjust tappet clearance and check that all is OK with compression etc. and attempt to remedy any defects that may show up. I am also still researching glow plug drivers and will need to make a purchase soon but all in all "attempt to start day" inches slowly closer.
On the subject of machining titanium I have just watched a "You Tube" video on making the Lockheed Joint Strike Fighter Plane and they spent five months machining just one of the main airframe bulkheads. Sort of puts into perspective the challenges this material has for the home machinist !
How is your Edwards coming along Michael?

Cheers all - Brian *discussion*

 

[birdii16v]

Hi everyone. This is my first post on this forum! I have really enjoyed reading about this Edwards radial build, certainly got my interest light on!

I should introduce myself first, I live in Lincolnshire England and I am an engineer by profession. I have worked through an apprenticeship machining and fitting then after a break of a few years I went to university and studied for a degree in mech eng. Now that I am just about desk bound the garage is a real sanctuary where I can still get my hands dirty!

I am also a keen aeromodeller and the pride of my collection is my Gilmore red lion racer fitted with an SC 400 5 cylinder radial! This engine is also glow allot like the Edwards (but nothing like the quality) and is 64cc.

So I approach the Edwards from a slightly different path, I have the planes and can fly them but now I want to build my own engine!

I absolutely love my radial and fly it whenever I can, the sound is superb although I have to confess to being a full throttle freak. If it isn't doing 7k revs then I'm not enjoying it!😀.

I wondered if I may be able to offer advice on the actual running of a beast that is the 5 cylinder glow radial in return for all of the fantastic machining tips that I have already gained from you guys?

Firstly, glow plugs. I have always been a big fan of the os f type plugs in 4 stroke glows. They have served me very well and still do in the SC. It will idle very well with these plugs without a glow system however for security I do run an on board glow system. My engine was actually 2nd hand. The previous owner had given up on it as it wouldn't run well. I tested it after purchase and agree it was rubbish. I made one change and it cured everything - the glow plugs!

There aren't many glow systems on the market for 5 cylinders. Sullivan make one but I can only find bad reviews on this. My approach was to use three twin cylinder drivers from HobbyKing. This isn't the neatest approach but they work brilliantly. My radio is set up to switch the glows on to half power below 1/3rd throttle. Above this I don't use any power. The spare lead is just tucked away and causes no issues.
Here is a link to the drivers that I have used:

www.hobbyking.co.uk/hobbyking/store/__35848__Two_Cylinder_Engine_R_C_Glow_Plug_Driver.html

I will continue to follow your thread with great interest and hopefully some day soon I will start a build of my own! Thanks
Dan

 

[petertha]

Nice meeting you birdii16v

Coincidental you should mention the SC400. I was just looking at that engine ad recently, more specifically what appears to be a ignition harness offered. They only show the plug boots, not the business end. Do you know much about it or used it?
http://www.allelectricrc.co.uk/sc400-64cc-5-cylinder-radial-256-p.asp


Re the HobbyKing glow harness, good score there.
- its designed for 2 cylinders, so 3 harnesses = 6 plugs for 5 cylinders so 1 odd connector remains un-connected. I assume it must not 'overdrive' (overheat) that single plug as a result?
- How about your battery configuration? They say 3.2V~8.4V (1~2S LiXX)Do you run 1S or 2S lipo ? One pack feeding all harnesses? How much maH capacity? What kind of current draw do you see at the plugs? I'm guessing by this input range the board must have the equivalent of step down regulator.

Sorry for the non-Edwards post. Maybe if this has interest, re-post under a new multi-cylinder glow ignition title. This topic comes up often & I'm interested myself.

 

[birdii16v]

Hi. The leads shown in the picture are supplied with the engine. The instructions show these to be connected to a 2 volt battery. This works but gives full glow power so you need a large battery to get good duration. If I remember correct the current draw was around 10 amps.

I now use a 4 cell NiMH 5000mah with the glow driver's, this gives me enough power for a days flying.

The reserve (sixth) glow lead hasn't caused any problems and I get 5 very equal glows. Its a cheap solution that has been very practical for my application.

Apologies if I have gone off topic!

Dan

 

[Brian-in-Oz]

Hi Dan - welome to the forum.

Your experience with a running radial could be priceless to Michael and myself.
My Edwards Radial is virtually "finished but not finished". I am not completely happy with the evenness of compression and want to sort this out before even attempting to get it to run. I was never very happy with the method described in the plans for making the piston rings - turn up an oversize tube of cast iron and mill a slot along its length then compress in a chuck and finish bore and grind.
The slot compresses OK at the chuck end but remains slightly open at the other end and there is the possibility of distortion.
Anyhow I have decided to spend more time and effort on the rings and make new ones by the Trimble method and a spare set while I am at it before even attempting to get the engine to run.
I have also been looking around at glow drivers and this one caught my attention as it comes in twins and singles so you can daisy chain two twins and a single together for five cylinders. http://www.southhertsmodels.co.uk
Do you have any knowledge of this product.
There is an Australian distributor for South Herts Models.
Looking forward to seeing you make some radial swarf.

P.S. petertha definitely not off the thread - right on the money in fact.

Cheers Brian wEc1

 

[xjs]

Hello all --

Xjs back again, feeling a bit of an underachiever. You'll have perhaps heard that work is the curse of the drinking classes? Well, I'm here to tell you it's also the curse of the swarfing classes...just far too little shop time the last few months, and now I find myself (not TOO unhappily, I must admit) on holiday, on the other side of the planet from my poor, neglected Radial.

Most all of the valve train is now done...valves, pushrods, lifters, retainers, springs, even mostly done with the rockers.

I've run across a bit of a snag with the heads, though...just before leaving town I pulled off a head to try out my recently acquired valve seat cutter. Wasn't at all happy with the result...it seemed the screw-in valve guide didn't line up exactly with the valve seat, producing an asymmetrical result I didn't like the look of at all. Pulled another head...same result. Then, had to rush away and haven't played with it since. I'm rather hoping this doesn't mean I'll have to make a new set of heads from scratch...now I won't know for sure till I get back to HI in a couple of weeks.

Brian, your motor looks ready for prime time...all that pretty pipe work, and those motor mounts look better than the originals! Sorry, butl instructive, to hear about your reservations about the rings though. I suppose if these radials were easy, everyone would be making 'em!!

And Dan, great to have you aboard! Thanks for starting the discussion on glo plugs, and I know Brian is as exited as I am at the prospect of having another build going.

Aloha all,

 

[birdii16v]

Hi Brian,

I haven’t come across South Herts Models or that particular glow driver however after reading the literature it appears to be a sophisticated system and very likely well up to the job!

If you need a simple method to test the engine then a 2v lead acid battery will do the trick. A very functional (but not tidy) method of attaching the power supply to the glow plug is to use an electrical terminal block with the plastic stripped off. My leads are now attached using this method however they are out of sight in the cowling.

I'm interested in the method you will use to measure the compression. This is something that i have thought of doing on the SC engine as it has suffered with cooler cylinders at the bottom of the engine. This may be simply down to fuelling but i thought it may be worth a compression check.

My idea was to make an adaptor to use an automotive compression tester however I’m not sure that the gauge scale will be adequate. It would be simple enough to make so may be worth me having a try.

Dan

 

[Brian-in-Oz]

Hi Dan,

sorry for being so slack in answering your post - I have been spending most of my spare time recently putting together a rather complex itinerary for a planned overseas trip of three months. I have seen small compression testers listed online that screw into the glow plug hole but I don't think it would be to difficult to make one. Many years ago (like nearly fifty) I made a tester to keep an eye on the compression of my Cooper "S" (the proper one) that got thrashed within an inch of its' life. To do this I simply attached a compression gauge to a tube and on the end of the tube attached the valve and teat cut from an inner tube that pushed this into the spark plug hole which sealed while cranking the engine. Pressing the valve released the pressure and so a reading could then be taken on the next cylinder - simple but it worked a treat. I am sure something could be done on a smaller scale.
On the Edwards front I have decided to make a whole new set of piston rings and heat treat them in a temperature controlled oven (kindly loaned by a friend with a very nice commercial machine shop) and am working on a jig that can be returned to the lathe accurately between centres and individually grind the rings for each cylinder. I will post some pictures of this soon.
Unfortunately it does not look like i will have the engine running before we leave - ah well, looks like Xmas is the new deadline.

Cheers Dan - Michael and all - Brian :hDe:

 

[LADmachining]

I have the plans somewhere for a small engine compression tester that was designed by the late Bob Shores. They were made available from the floridaame.org website.

The tester used a small pressure gauge with a 1/8"NPT that are typically used on pneumatic fittings, and a non-return valve to keep the accumulated pressure within the gauge (and maintain the reading) until reset.

Will dig them out and post them.

** EDIT ** Here is a link to the drawing - http://floridaame.org/HowTo_files/image002.jpg

 

[Brian-in-Oz]

Hi All,
thanks for the link on the compression tester Anthony.
Once I come to grips with making piston rings properly I will probably make one.
After being dissatisfied with the Edwards method of slot, clamp and machine piston rings I had a go at the Trimble method and was not satisfied with the results here either. I believe that heat treatment by this method is not precise enough for consistent results and I also found the ring not contacting the bore at all points around the circumference.
In my mind the only way to get a perfect ring fit is to grind it to the exact bore size after the ring has been wedged open and correctly heat treated in a temperature controlled oven.
To this end I have made a jig to hold heat treated and correctly gapped rings in a compressed state while grinding to size. I have made the jig to operate between centres driven with a lathe dog so that it can be easily and repeatedly removed and replaced in the lathe and be dead true each time which is not possible with a chuck.
I have decided to make the rings 10 thou. oversize and they are then loaded into the tube of which the bore is also 10 thou. oversize and is a perfect sliding fit onto the jig. The tube with the rings loaded is pushed onto the jig until they contact and are concentric with the ridge and then the neatly fitting clamping cap is mounted and tightened. The tube is then removed leaving the rings clamped in a compressed state ready for grinding with the tool post grinder.
Another advantage of this jig is it will fit a high precision grinder graduated in microns that a friend with a machine shop has and he kindly offered the use of.
When I have machined up some rings and ground them I will report as to the success or failure of this method. If nothing else this exercise with piston rings has been a great learning curve.
An extremely in depth article on piston rings as well as a similar diagram to the jig I have made can be found here - http://www.model-engine-plans.com/engineeringtips/pistonrings.htm
Pictures below should give some idea as to operation.

Cheers All - Brian :wall:

 

[ozzie46]

Brian, I think you will be disappointed again with your method.

I'm sure you just over looked this but here goes.

If you grind the rings to the bore size after heat treamant and gapping, there will be no out ward springiness or pressure to force the rings against the bore and they won't seal bore to build compression.

The rings should be made to a stiff push fit in the bore,THEN gapped and heat treated so they will exert the required pressure on the cyl bore.

Ron

 

[Cogsy]

I think he's compressing the rings, then locking them in a compressed state and grinding to the bore size. When released they will again expand but they won't be a truly round shape until they are placed into the bore. Then they should be a true full contact ring, with the required pressure against the bore.

 

[Brian-in-Oz]

Thanks for your interest and comments Ron and Al.

Ron the rings will have tension against the bore as they will have "springiness" after being heat treated in a wedged open state. The purpose of the tube is to hold the rings in a compressed state and keep them perfectly concentric prior to assembling and tightening the cap that holds them in position for grinding to the bore size.
Al correctly grasped the idea in that on removal from the grinding jig the rings will expand but after fitting to the pistons will be compressed to fit the cylinder and should be a perfect fit on their whole circumference with the correct pressure against the cylinder walls. When I mentioned gapping the rings I was referring to the very small (about 4thou.) clearance at the "break" that allows the ring to compress minutely smaller than the bore so that binding cannot take place and tension is maintained against the cylinder walls and there is only a tiny gap where blow by can take place.
I have to source some more cast iron so it will be a week or so before I get to actually make some more rings but will post a report on how I get on.

Thanks again for your interest guys - i hope this better explains the principle.

Cheers Brian Thm:

 

[ozzie46]

Ok. I see now.

Ron

 

[petertha]

... and I also found the ring not contacting the bore at all points around the circumference.

This is great stuff. I hadn't realized there was any subsequent information or opinions subsequent to the Trimble methods.

1) I'm curious when you say 'not contacting', how did you determine this & quantify it?

2) Just for kicks, have you similarly tested a so-called commercial ring like any typical RC 4-stroke of similar bore inside the liner & compared how they fare against your shop made effort?

3) Does the cast iron machine (grind) any different once its been heat treated to gap open state? What kind of stone or abrasive grit would be appropriate here?

 

[Brian-in-Oz]

Hi Petertha - thank's for you your interest in my piston ring making attempts.
I'll try to satisfactorily answer your questions.

1. It was easy to determine the rings were not contacting on their whole circumference. When heat treated by the Trimble method they take on a blue colour like rifle blueing and this tends to rub off at contact points exposing the "high spots". I also placed a ring in the bore and blocked off its' centre and placed a bright light in the bore behind the ring and in a dark room you could actually see a tiny sliver of light peeping through where the ring was not contacting.
The high spots were at the gap and exactly adjacent just as described in the article in the link in my first post on rings.
2. I don't have access to a commercial engine for comparison.
3. I am not a metallurgist so I cannot speak with any authority as to the effect of grinding or skimming after heat treating other than to assume it has little or no effect as commercial cast iron rings are usually made from pre heat treated blanks and then ground. Any heat generated in the grinding process would be absolutely minimal as only a fraction of a thou. will be removed at a time and the jig would quickly dissipate that.
If I resort to using a friends commercial grinder think in microns not thousandth of an inch. 25.4 microns to one thousandth of an inch. I should be able to get a nice fit working with those tolerances - just makes us home modellers realise how coarsely graduated the equipment most of us work with really is.
None the less I am first having a go with my tool post grinder (3 " white aluminium oxide wheel - not sure of the grit size, it was supplied with the kit but is fairly fine) as I would like to complete the Edwards using all my own equipment.
You can call me pedantic because I am but I prefer the idea of the rings evenly contacting the bore and not potentially wearing the bore unevenly while waiting for the rings to "bed" (i.e wear in).
Of course until I actually make some rings with this method everything is hypothetical so will post results good, bad or otherwise.

Cheers Brian :

 

[Swifty]

Hi Brian, I'm following your post with great interest and enjoying the pics. I had a great Jones and Shipman cylindrical grinder at work, that too was graduated in microns on the fine feed dial and was dead on accurate. I get the impression that some people think that heat treating cast iron rings actually hardens them, it's only to set the gap at the correct sprung size.

Your method of holding the rings for grinding sounds like an excellent way of doing things, if I recall correctly, most of our cylindrical grinding was done with a 60 grit wheel, both hard and soft material.

Paul.

 

[Brian-in-Oz]

Paul - just out of interest I will find out what make of cylinder grinder is in my friends workshop - it is his temperature controlled oven I am going to use to heat treat the rings. I have just had a phone call from Surman Metals in Adelaide to say some cast iron and 2024 aluminium I had ordered will be in in a couple of days so I should be able to get into making some rings by the weekend.
I have a stack of grinding wheels for my flatbed grinder and I had a look and they are 60 grit and look about the grit same as the one on my tool post grinder.
Just for fun I took a picture of the cross feed dial on my "oldy but a goody" Hercus lathe. The dial is only .970" in diameter and and the graduations .001" which means advancing just one graduation mark removes a whopping .002".
To be able to accurately machine with 25 odd more graduations jammed in between those tiny graduations is something for us hobby guys to just dream about.
None the less I still work between those graduations when needing the accuracy - I tighten up the way gibs a tad so things don't move too freely and creep the feed forward with as steady a hand as possible.
What sort of work did you do Paul - we need people like you with a practical machining background to to keep us hobby hackers on track.

Cheers Brian *knuppel2*