Author Topic: 3 Cylinder Radial Compressed Air Engine  (Read 17221 times)

Offline Thayer

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Re: 3 Cylinder Radial Compressed Air Engine
« Reply #30 on: June 05, 2013, 06:54:56 AM »
Chuck,

That is a great runner indeed! Congratulations. I couldn't help but be reminded of the old Whirlwind by Bert Pond from years ago. My guess is you could turn a much larger prop if you wanted to.

Thayer

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Re: 3 Cylinder Radial Compressed Air Engine
« Reply #31 on: June 05, 2013, 08:01:31 AM »
Yeah good stuff Chuck!

Looks great as a three but could it be extended to six?
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Offline MuellerNick

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Re: 3 Cylinder Radial Compressed Air Engine
« Reply #32 on: June 05, 2013, 08:07:10 AM »
Quote
but could it be extended to six?


An even number of cylinders looks odd. :)
Radials always (?) had an odd number of cylinders. Yes, more would be possible. But the diameter of the hub has to increase as the number of cylinders increases.


Nick

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Re: 3 Cylinder Radial Compressed Air Engine
« Reply #33 on: June 05, 2013, 08:37:51 AM »
How about a five then?

I've been thinking about making the central 'hub' from a chunk of Ally rather than a casting so would have free choice on the number of cylinders.

Simon.
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Offline MuellerNick

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Re: 3 Cylinder Radial Compressed Air Engine
« Reply #34 on: June 05, 2013, 08:57:30 AM »
Quote
How about a five then?


You can make any number, as you want. You won't have any problems coming from the oddness or evenness of the cylinders as this design works like a two-stroke.
It is just that even cylinders look strange. At least to me.


Nick

Offline Jo

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Re: 3 Cylinder Radial Compressed Air Engine
« Reply #35 on: June 05, 2013, 09:05:37 AM »
If you are building a radial four stroke you have to have an odd number of cylinders because it operates on a "skip and fire cycle". If you had an even number of cylinders half of the cylinders would never fire  :facepalm:.

Jo
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Offline b.lindsey

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Re: 3 Cylinder Radial Compressed Air Engine
« Reply #36 on: June 05, 2013, 12:21:28 PM »
SCO....you could think about doing two rows of three to get the total of six cylinders, then offset the rows by 60 degrees if my early morning math is correct for an even appearance.

Bill

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Re: 3 Cylinder Radial Compressed Air Engine
« Reply #37 on: June 05, 2013, 12:39:59 PM »
Bill,

Yes I wondered about that - searching on the internet there is a Bristol 18 cylinder radial aero engine - an even number of cylinders but it's two rows of 9 so complies with Nick's requirements I think!

Simon.
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Offline MuellerNick

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Re: 3 Cylinder Radial Compressed Air Engine
« Reply #38 on: June 05, 2013, 12:56:02 PM »
Yep! Two rows is a new game.
The even number of cylinders comes from the way the camdrum (they had no camshaft) was and that they were all 4-strokes with pushrods.
If they had had OHC, they could have had andy number. But OHC was not common at that time for radials. At least to my knowledge (that doesn't mean too much).


But I think, we are drifting off way too much from Chucks work.




Nick

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Re: 3 Cylinder Radial Compressed Air Engine
« Reply #39 on: June 05, 2013, 01:00:56 PM »
Yeah but Chuck knocked it out way too quick - we need to persuade him to attempt a multi-row version  ;D
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Offline cfellows

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Re: 3 Cylinder Radial Compressed Air Engine
« Reply #40 on: June 05, 2013, 01:17:43 PM »
Thanks, folks, for the comments and support.  A five cylinder version may be in my future sometime.  I've thought about building Rudy Kouhoupt's 5 cylinder radial using my slave valve arrangement and may do that at some point.

I just wanted to add a few notes for those who are interested.

The crankshaft on my model has a diameter of .1875" of an inch.  I think Nick's crankshaft was closer to .27" so larger crankshafts are certainly not a problem.

Another thing to consider is the air pressure it takes to run my engine.  While the spring loaded ball exhaust valve engine is somewhat simpler to make it does require from 15 - 20 PSI to run.  And, it won't idle as slowly Nick's design.

Finally, the parameters of the spring and ball bearing are somewhat critical.  The ball bearing must move freely in the bore and a clearance of several thousands of an inch is desirable.  The spring must also fit loosely and have a very small compression force.  The springs on my engine are about .008" wire size, 1/8" OD, and just barely long enough to hold the ball bearing in position between power strokes.  The stiffer the spring, the more air pressure it takes to run the engine and the faster it will run, but won't idle as slow.

Chuck
So many projects, so little time...

 

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