Re: Cox Engine of the Month -3 Way Tie Vote-Off

Jason_WI Sat Jan 28, 2012 12:30 pm

Not a barnett radial. It is a custom engine off of eBay I got a while back. Here is a drawing from the designer.

https://servimg.com/view/16999734/42

nitroairplane Sat Jan 28, 2012 12:47 pm

Thank god the designer is better with a mill than he is with a pencil Smile

But he got the point accross.

Surfer_kris Sat Jan 28, 2012 1:37 pm

So it is designed to fire sequentially and has a common crankcase?
Doesn't seem particularly smart, does it run?

**Admin** Sat Jan 28, 2012 2:25 pm

Thats right, I have to throw your radial page together that will load when someone clicks on the picture.

OK, I just made the page. Click on the small picture on the left and it will open a page with some info.

Big Al Sat Jan 28, 2012 3:59 pm

Surfer_kris wrote:So it is designed to fire sequentially and has a common crankcase?
Doesn't seem particularly smart, does it run?

It doesn’t seem likely to be a runner unless he has incorporated some ingenious way to create three crankcase suction/pressure cycles per rev. Not saying its impossible; just that it isn’t obvious to me Shocked

.
Al

nitroairplane Sat Jan 28, 2012 4:00 pm

It must run!
Even I could make one that didn't run.

Surfer_kris Sat Jan 28, 2012 4:30 pm

It would need a compressor on the intake in order to run, but it looks like it is just has a regular sure-start reed valve on it.

Jason_WI Sat Jan 28, 2012 4:59 pm

Surfer_kris wrote:It would need a compressor on the intake in order to run, but it looks like it is just has a regular sure-start reed valve on it.

You are correct in that it needs a compressor to run. Having 3 cylinders on one crankcase it looses its suction. Ideally it needs a roots type compressor. I am planning on modifying the rear cover to use a full length sure start crankshaft. I will have a pully on the output and it will drive a RB Innovations super charger. I have a carb off of a OS 12CZR that I am planning on using for the engine. I can then do away with the sure start backplate and make a radial mount out of aluminum. I have the supercharger and the aluminum. I just need the time.

The engine does run off the prime. I will have to get a vid of it up. The sound is amazing Very Happy

Jason

nitroairplane Sat Jan 28, 2012 5:13 pm

Oh yes I cannot wait!

Surfer_kris Sat Jan 28, 2012 5:24 pm

There are in principle three choices/possibilities in a multicylinder two-stroke engine; i) simultaneous firing (e.g. G-Mark .12 opposing twin), or ii) separate crankcases (e.g. G-Mark .30, 5 cyl. radial) or iii) compressor on the intake.

I can't think of any commercial 1/2A size engine with a compressor? So it seems like a bold endeavor...

nitroairplane Sat Jan 28, 2012 5:28 pm

Well how does valentine do it?
I don't have one of his to disassemble and look at.

Surfer_kris Sun Jan 29, 2012 1:53 am

I don't have any from valentine myself, but I believe each cylinder has an individual crankcase with gears that drives a center propshaft. I.e. the same design idea as the G-Mark .30 (5 cylinder radial).

nitroairplane Sun Jan 29, 2012 5:16 am

Just found this info.

"Let me introduce you to the Mark I & II Taifun 3 Cylinder Radial diesel engines. The crank case was machined from bar stock and only the Mark II was sand blasted. We manufactured 10 of these engines. The cylinders and spinner were anodized in different colors. Each cylinder had 2 intake and 2 exhaust ports. All of our multi cylinder engines have divided connecting rods and a one piece crank shafts. The Mark I has a 3 piece and the Mark II has a 2 piece crank case."

Surfer_kris Sun Jan 29, 2012 5:37 am

Looking through Valentine's site it seems that he has made both geared and compressor types;
5-cyl radial

Still, a two stroke engine cannot have one common crankcase volume unless the cylinders fire at the same time, or the crankcase is pressurized.

Cox Engine of the Month -3 Way Tie Vote-Off - Page 2 58-radial-5-cylinder

Cox Engine of the Month -3 Way Tie Vote-Off - Page 2 58-radial-5-cylinder

nitroairplane Sun Jan 29, 2012 5:41 am

Surfer_kris wrote:Looking through Valentine's site it seems that he has made both geared and compressor types;
5-cyl radial

Still, a two stroke engine cannot have one common crankcase volume unless the cylinders fire at the same time, or the crankcase is pressurized.

Yeah and i think even Valentine would struggle making a 4 stroke 5 cylinder radial of 0.098cc Smile

Surfer_kris Sun Jan 29, 2012 5:51 am

With a four stroke radial you can have a common crankcase without any problems, that's is perhaps where the poor design comes from.

nitroairplane Sun Jan 29, 2012 6:00 am

Yeah the designer probably did not have much experience with cox engines.

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