different piston design for IC engine

[windy]

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

 

[Lauri]

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

 

[Lauri]

Another picture..

 

[Lauri]

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

 

[petertha]

And just for something on the other side of the spectrum demonstrating‘thick’ 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

 

[trumpy81]

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

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

 

[trumpy81]

..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?

 

[trumpy81]

And just for something on the other side of the spectrum demonstrating‘thick’ 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?

 

[petertha]

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.

 

[Lauri]

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

 

[Lauri]

That's how it looks like.


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

L

 

[trumpy81]

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