Gasp! Where's the pull? Cool model!

 

Just thought I might point out that most radial engines have an odd number of cylinders. I have seen some two stroke ones with even numbers but all the 4 strokes I've seen are odd. Has to do with the firing order. Still I want to see what the pull looked like. :!:

 

That is cool man! Now you need a 1910 era plane to mount it on!

 

Really cool! I have to admit I also noticed the even number of cylinders. Four stroke radials were usually five or seven cylinder. I used to know why the need for odd number of cylinders, but I have forgotten that. I also can't remember where I live. I have a Phlatformer coming. It will be interesting to see what it does. Good job you guys on this radial engine project. I would like to see some sort of pointed and fitted piece for the nose of the various pusher jets like the FunJet, F22, etc. That would tidy up and toughen up the nose on the planes.

Chuck
...somewhere in Indiana...

 

The odd number of cylinders has to do with the firing order of a 4 stroke. It fires every other cylinder as the crank rotates around, if you count that around you can see that in two revolutions you have every cylinder fire, if you've got an even number of cylinders then it doesn't work out.

 

I've been thinking about it too, Gefahren, and I think there must be something particularly related to radial engines that forces the odd-number issue - but I haven't got a clue what it might be.
After all, there are 4, 6, 8 and 12-cylinder automobile engines that work smoothly enough for ground travel. 4-cylinder engines fire in the typical order of 1-3-4-2 and I think many 6-cylinder cars fire 1-2-4-6-3-5.

 

Not to take this too far off topic, but...

It is something related to a radial engine. Each bank of cylinders has one crank "lobe" that they are all connected to, so as the crank spins each cylinder goes to Top dead center one after the other in order around the engine. So one will start the combustion cycle the next will start the intake cycle then the next is combustion and so on around the engine untill you come back to the first cylinder again and its doing and intake cycle now. With an even number of cyclinders there would be a "gap" in the firing order that would really make the engines shake more than they already do. So the firing order for a 9 cylinder would be 1-3-5-7-9-2-4-6-8.

Also note that they always had one cylinder pointing straight up to help minimize the oil collection in the lower cylinders when the engine was not running.


Now, any ideas how to get the fins on the front of the plug for the engine? and just how thin can they reasonable be made?

 

Ahh yes! All cylinders are driven off the same lobe on the crankshaft, so it's not possible to mix up the firing order! Now, why didn't I think of that?

 

I looked into making it a 7 cylinder motor, E=T, and it took me all of 10min to do the conversion. Why don't you do it too before you cut it again?

 

Sure, no problem. While at it, I made a 9 cyl. version too. Both are in the same file. Make changes as you see fit!!! Attached files Multi Cylinder Radial Engine 3.skp (1.5 MB)Â