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Old 03-01-2012, 04:53 PM   #1
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Default Elbow Engine

So I have decided to build the infamous Elbow Engine. I am using the plans found on the John-Tom website http://www.john-tom.com/html/SteamPlans.html.



Starting out with a bang (literally)...once I found out that I goofed the flywheel hub to the point of no repair I smashed it with a hammer. It sounds childish (and it is) but it felt great. Practice makes perfect right? The second attempt led me to make a fixture for mounting in the mill vice and everything went nice and smooth, so far so good. Next will be the flywheel rim.

The photo shows a correct flywheel hub and the hammered one. I have also included a CAD image of the fixture. It is a 2" diameter piece of aluminum cut to approximately 1" in length. I drilled and reamed a 1/4" hole in the center for a dowel pin and some 10-32 tapped holes for mounting. My intent was to create a program on the Bozo-Trak to cut (1) slot....I then unclamped the hub and indexed it 90-degrees using the dowel in the center. It worked out great. After the 4-slots were milled out I cut the outside diameter. After that I used the 4 outer tapped holes to mount the hub while I milled out the bore.

I can already see some of you (old school) machinists twitching in your chair asking "why didn't he use a 4-jaw chuck". Am I right Why do you think a hammer was taken to the first hub?

Chris



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Old 03-01-2012, 06:11 PM   #2
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Default Re: Elbow Engine

Since you have a CNC mill, you "might" have tried it my way:

Mount soft jaws in the vise and mill a circular pocket equal in diameter to the flywheel stock. Then with the stock securely clamped you can mill the 4 pockets plus the center bore without moving the piece.

All's well that ends well.



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Old 03-01-2012, 06:28 PM   #3
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Default Re: Elbow Engine

Ahhhhhhhhhh.....that sounds better! See, this is why I like this forumn.

I make have to make a third flywheel now.

Thanks!

Chris

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Old 03-01-2012, 06:33 PM   #4
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Default Re: Elbow Engine

On the other hand, why not make it without using CNC, then we can all enjoy your build.

John

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Old 03-02-2012, 12:59 AM   #5
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Default Re: Elbow Engine

John...I purchased a small rotary table a few years back for doing just that at home. But at the college I have access to the Proto-Trak and get to use it whenever I have time. This flywheel hub is the only part I will be using CNC for...the rest will be done manually.

Stay tuned...more to come.

Chris

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Old 03-06-2012, 11:59 PM   #6
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Default Re: Elbow Engine

I finished the flywheel rim using 3-1/2" steel pipe as suggested in the plans. This was the first time I made a two piece flywheel so I was a bit nervous....and yes I had to scrap one because I removed too much material on the inside diameter. The second flywheel rim came out great.

The two brass cylinders came out fine...however the cylinder I planned on using for the flywheel did not fit and the cylinder that sits on the valve block did. I switched them around which is no big deal but now the cylinder that will sit on the valve block has a slight step in it.

I reamed the center holes of each cylinder to 3/16" diameter for a standard shoulder screw instead of a 1/4" screw like the plans had suggested. I felt that the head of the screw came too close to the pistons and made the decision to step it down a little. I like using shoulder screws anyway.

The valve block came out great and yes I used the Bozo-Trak to make the valve port slots...my rotary table is getting jealous!

Base tomorrow...I'm saving the pistons for last.

Chris


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Old 03-18-2012, 10:53 PM   #7
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Default Re: Elbow Engine

Well I finished the sucker...and it seems as though I have a lot of "finessing" to do until it runs.

One I have it running there will be additional pictures and hopefully a video.

I am having a hard time spinning it freely by hand...it grinds an awful lot in a couple of areas.

I'll keep on cranking away though...

Chris

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Old 03-20-2012, 09:39 PM   #8
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Default Re: Elbow Engine

I can't get this thing to work...is there any special way to assemble it for timing?

I have tried many different configurations and at 30psi it does nothing except leak air.

I machined and installed an o-ring into the base cylinder and that did nothing.

It spins freely by hand with a couple of rough spots.

Any suggestions? Should I smash it with a hammer?

Chris

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Old 03-20-2012, 09:48 PM   #9
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Default Re: Elbow Engine

Try lubricating the pistons with a heavy oil, eg 30 wt motor oil. That may form enough of a seal to get it to turn over.

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Old 03-20-2012, 09:52 PM   #10
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Default Re: Elbow Engine

Hi Chris

No - the hammer won't work....

Where are the rough spots; this engine does not like rough spots... Are you trying to just turn the flywheel without any air pressure applied to the engine ?

What oil are you using for lubrication? - try different oils, starting with thin and moving on to thicker - mine runs best with diesel engine oil.

There's a problem with using thicker oils though - they provide a better seal (and stickier spots for spectators to rub off their faces ) - but introduce a lot of drag on the engine to overcome viscosity.

Regards, Arnold



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