Scrap bin motor

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dvbydt

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Inspired by Chuck's opposed 4, I decided that I would have a play with rotary porting to see what I could learn about timing. Half way through some experimenting, this idea of a test bed motor came from nowhere!

[ame]http://www.youtube.com/watch?v=lOQOHEJTG00[/ame]

Building the bits.

Rotor1.jpg


TransferPort.jpg


Assembly
http://i757.photobucket.com/albums/xx213/dvbydt/Air%20Motor/Components1.jpg[/img]


Compressed air is supplied to the copper tube. I don't have steam but I am sure it would work.


The machining took about four hours and I then had a running motor. At 10 psi it runs at 2,000 rpm and at 20 psi it makes 5,500 rpm, I did not want to try it higher!

What did I learn? Rotary ports work easily and there is no need for extreem precision, stationary leakage is no problem. Timing is not that critical. Speed is best governed by restricting the exhaust.

Has anybody got anything to add about the design of rotary ports? Then I can get on with this next project.

Ian
 
i just dont get it for some reason how it works
 
Sid,

Compressed air flows into the stator spindle via the copper tube, then via the transfer port to the two pistons. These are forced appart moving about 5mm. At maximum stroke (the rotor has moved about 90 degrees) the air is cut off and the pressure is bled off via the exhaust port in the outer sleve. The rotor has now moved 180 degrees and the cycle is repeated.

The rotor is about 45mm OD, the pistons are 8mm and the rollers are Delrin.

Ian
 
Interesting application. Took me awhile to figure out what the pistons look like, but I think I've got it.

Chuck
 
i still dont get how it works but it is cool looking.
 
Thanks for taking an interest. Not very good at explaining how it works, sorry, perhaps this is better. I didn't do any drawings, just made it up from scrap bits.

Ian



Air Path.jpg
 
OH ok now i see how the thing works those little wheel are pistons hahaha
i just could not for the life of me figger out how that worked .
Thank you for that. it makes sence now
 
That's really a pretty elegant little engine with some nice design features. I particulaly like the slotted cylinder sides to keep the rollers oriented correctly. Wonder how well it would scale up?

Chuck
 
itowbig,

I'm pleased I managed to get the idea across.

Chuck,

It should scale up OK, but would probably need ball races rather than plastic rollers. It did cross my mind that the rotor might make a centrifugally supercharged, uniflow, 2 stoke a possibility, but just a pipe dream!

The reason I was experimenting with porting was for a small air driven V8, but the elegant ball valve exhaust ports on your opposed 4, has caused a redesign and that engine is on hold for the time being.

Ian
 
Glad you are trying the ball valve design. It's fun to see how other people adapt it to their own designs.

Chuck
 
What is the actual shape of the Rotor cavity - is it 3 holes at offset spacing, or is it a more complex set of curves?

Murray.
 
Murray,

Yes, just 3 bores. The concentric one done on the lathe, the two offsets done at the same setup on the mill with a
flycutting tool.

Ian
 
Hi Ian,

Could you post a few basic dimensions please - this one intrigues ???

Murray
 
Murray,

Drawing of the rotor for you, should give you most of the information. I didn't do any drawings before I started, just made it up as I went along, so the drawing is just measurements of the completed motor. Important is the 5mm hole size as it gives the correct spacing of 45 degrees for the porting.

Ian

RotorImage.jpg
 
Thanks Ian, it's now on my 'to-do' list.
Am I right in assuming that the Porting Holes go all the way through the Rotor Shaft, (making 4 in total)?

Murray
 
Murray,

Two holes and two slots - the inlet transfer ports that get covered by the outer sleeve.

Ian
 

That is the coolest thing. You were thinking outside the room holding the bag that the box was in!
 
With the number of views of this thread, I figured this little experimental air motor had earned a mount and a dust cover.

Ian

Dust Cover.jpg
 

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