# Scrap bin motor



## dvbydt

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.












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


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## itowbig

i just dont get it for some reason how it works


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## dvbydt

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


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## 1hand

thats pretty cool.

Matt


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## cfellows

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

Chuck


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## itowbig

i still dont get how it works but it is cool looking.


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## dvbydt

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


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## itowbig

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


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## cfellows

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


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## dvbydt

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


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## cfellows

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

Chuck


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## imagineering

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.


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## dvbydt

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


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## imagineering

Hi Ian,

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

Murray


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## dvbydt

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


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## imagineering

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


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## dvbydt

Murray,

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

Ian


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## crueby

That is the coolest thing. You were thinking outside the room holding the bag that the box was in!


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## dvbydt

Crueby,

Looks like someone discovered the same box years ago! Jeff posted this link in plans.

http://www.aqpl43.dsl.pipex.com/MUSEUM/POWER/unusualsteamrotycyls/unusualsteamrotycyls.htm#ljung

I'm miffed 

Ian


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## dvbydt

With the number of views of this thread, I figured this little experimental air motor had earned a mount and a dust cover.

Ian


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## dvbydt

These photos were meant to be attached to the prious post, but I got it wrong somehow!


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## BaronJ

dvbydt said:


> 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!
> 
> http://www.youtube.com/watch?v=lOQOHEJTG00
> 
> Building the bits.
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 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




Very ingenious Ian !  A nice bit of machining too. 
I wonder does it self start or do you have to give it a quick flick ?


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## deverett

Seeing Ian's original I shamelessly copied it, but without the wood base.  It doesn't self start, but a quick flick will get it going.  Runs at surprisingly low air pressure.

It always gets a lot of interest at the small shows I take it to.

Dave
The Emerald Isle


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## BaronJ

Hi Dave,

Thankyou for your reply.  I did wonder if it would self start with it having two stable positions on the rotor.  I found the concept fascinating.  So much so that I have started to collect a few bits together to try and make one.

Just a thought experiment having read the linked article would it scale to say six cylinders or even more and would an odd number of cylinders allow self starting.

I would love to see yours.


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## deverett

With me camera out, I took a video of my 'rotor Motor'.

[ame]https://www.youtube.com/watch?v=71_vJ9dniyw[/ame]

Anyone know how you can get rid of the discolouration on the bronze?  Normal polishing doesn't work.

Dave
The Emerald Isle


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## BaronJ

Hi Dave,

Thankyou for that video.  What a lovely sound.  I was a little surprised at how smooth and stable the speed was.  I'm most impressed. th_wav

Re the polish on bronze.  I'm sorry !  I don't know.  If the truth be known I don't think I could really tell the difference between brass and bronze.  Though I did mention that cutting a keyway recently in a brass bush was hard work compared to the same in steel.  Someone suggested that it might be bronze and not brass.

Thanks:


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## MCRIPPPer

you can pickle brass that has been heated and discolored. the discoloration is really just copper, because the zink burned out or migrated away when heated. so all you need to do is mix some vinegar, salt, and hydrogen peroxide. it will etch the copper but leave the brass behind. 

to tell the difference between brass and bronze is simple. brass is yellow and hard and makes flaky chips when machined. everything else is bronze. imo brass is just one of the bronzes (copper alloys).


if your material makes stringy chips or makes continuous chips when drilled, or is darker than bright yellow, its bronze of some kind.


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## BaronJ

MCRIPPPer said:


> to tell the difference between brass and bronze is simple. brass is yellow and hard and makes flaky chips when machined. everything else is bronze. imo brass is just one of the bronzes (copper alloys).
> 
> if your material makes stringy chips or makes continuous chips when drilled, or is darker than bright yellow, its bronze of some kind.



In that case the material I used must have been bronze !  When I turned it I needed to hone the lathe tool because it seemed not to want to cut, the tool seemed worn and blunt.  The swarf was little fine hair like strings and the tool left patterning when facing.

When I cut the keyway in the bush that I had made, the swarf was little curls that fell out, till I put a drop of oil on the tool holder because it seemed to rub and grab in the bore when retracting.

Yes, colour wise, its a sort of rose gold colour rather than a yellow, more a light copper shade.  In fact thinking about it, I have a brass retainer on the lathe and its a much darker colour than that is.

Well at least I now know that I've got a 75 mm by 30 mm AF bit of bronze hex bar left to play with.  I originally picked it up in the local scrap yard for a couple of pounds !.

Thanks for that info.


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## MCRIPPPer

brass and bronze may get oxidation on them but if you sand it to bare metal brass is really light yellow, no red.


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## abby

Brass is definitely not bronze , the different name is possibly a clue to this fact !  Very few bronzes come in bar form , they are mainly supplied as ingots for casting .
One bronze that does is Aluminium bronze, which looks identical to brass but you  will find it almost impossible to machine without newly sharpened  cutters, it can be identified from brass as it shows a very slight but  noticeable magnetic attraction.
The other bronzes that can be bought as bar or rod for machining tend to be phosphor bronze or gun-metal ( red brass in the US just to be awkward ) which do have a reddish colouration.
Most of the rod brass you will come across is 60/40 copper/zinc with very slight variation , also as 70/30 alloy known as cartridge brass mainly in sheet form.
The ductility and maleability of copper alloys varies greatly , many bronzes cannot be drawn into rods or forged so they will only be found as castings or cast bar.


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## BaronJ

Hi Abby,

I'm totally confused now !

The bit of bar is definitely not magnetic.  It does have a slight copper hue to it and it seems to be very tough.  I tapped six holes in it for M3 and it wasn't as easy as I would have expected.




This picture is a slice off the end of the bar bored out, and drilled.
The other half has the threaded holes in it.  I can post a picture of that if you wish me to.

Thanks:


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## MCRIPPPer

maybe silicon bronze? would have cost you big money tho if it was!  most bronze can be a bit hard to machine, almost like machining tough steel. it looks like brass in the pic, but by your description it doesn't sound like it.

where i work there were several sticks of 1.5" dia. silicon bronze rod about 15' long. apparently quite expensive! 

they had to be bent and they kept bending back straight after a few hours! tough stuff.


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## barnesrickw

Maybe Tin knows the difference between brass and bronze. Get it....


Sent from my iPad using Model Engines


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## aonemarine

260 brass maybe?  Kinda looks like it to me.  Doesn't machine as nice as 360, but seems to take a better shine when polished.


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## mcostello

there are many varieties of yellow looking brass. I have a sample of something called DV metal that is a pig to machine and it looks like that.


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