Elbow Engine

[vascon2196]

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


View attachment Elbow Engine-1.pdf

 

[kvom]

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.

 

[vascon2196]

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

I make have to make a third flywheel now.

Thanks!

Chris

 

[Blogwitch]

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

John

 

[vascon2196]

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

 

[vascon2196]

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

 

[vascon2196]

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

 

[vascon2196]

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

 

[mklotz]

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.

 

[arnoldb]

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 ;D) - but introduce a lot of drag on the engine to overcome viscosity.

Regards, Arnold

 

[SBWHART]

Try slackening off the base port so that you get a little movement then see if you can find a sweet spot thats lump free, and tighten the port down to try and capture that spot.

Make sure you're elbows are not too long and bottoming out.

Make sure your elbows are perfectly square.

Make sure you have minimum vertical movement of the cylinder on the pins

Stew

 

[rake60]

I couldn't get mine to run at all on oil.

I got frustrated and greased the pistons with heavy wheel bearing grease.
It ran fine on that.

Rick

 

[vascon2196]

Thank you everyone for the feedback. So far I ran into the piston being too long and bottoming out. I fixed that by grinding them down. I am checking squareness with my 6" craftsman square and holding it up to the light...getting them as square as I can that way.

I also started out with heavy motor oil. Yes it will turn over by hand (if I spin it quickly).

What's wierd is its not even turning over the tiniest bit at 30psi?

I looked over the plans again to see if I milled the air ports 90-degress in the wrong direction but everything checks out.

I will check for squareness again, try using a lighter oil....maybe bearing grease as suggested, and maybe a voodoo rain dance or something.

Thanks again everyone!

Chris

 

[SBWHART]

This is quite a good way to check the elbows for squareness, first clock the vice jaw dead square first though

Also check that the upright is square and then check the port blocks are square to each other.

like this

I run mine on slide ways oil: I checked the speed the other day at full pressure it does 1400 RPM.


Hope this helps

Stew

 

[vascon2196]

It does hlep...thank you. I did not think to check for squareness there.

Thank you,

Chris

 

[Ken I]

The clearance between the cylinder and the porting needs to be practically zero - the ports are is large and even a tiny gap adds up to a lot of air just going straight past (leakage) and doing nothing - this can quicly overwhelm your supply pipe / galleries.

Check squareness of everything.

Whilst unlikely, check your porting is correct for inlet and exhaust for both sets of cylinders - you don't have one trying to run opposite to the other ?

Ken

 

[Foozer]

The "turns over by hand with a couple rough spots" is how mine started out.
You found the piston bottoming out issue. Mine was some, well have no idea actually. After some run time there is the slight cross hatch pattern on the pistons. Figure some burr must of existed that worked itself out with higher air pressure.

It just sat there and laughed at me on 30psi, Cranked the air up with a big hammer on standby . . . She decided to turn over at 60 plus, after a minute or two of run time it settled itself out. It will run. It will run, It will run, It will, It Will, It, It, GRR

Robert

 

[Blogwitch]

Now you are finding out why so many of these engines end up under the bench.

Sometimes, no matter how well they are made, they really do defy the magic spark to get them running.

Mine, luckily, started to run fairly quickly.

The only thing I have to offer over and above what everyone else has suggested is to only have the port blocks just nipped up, then with about 10 psi on the pipes, very gently, using the plastic handle of a small screwdriver, tap the port blocks, just to move them a tiny bit one way or another. I did elongate the holes for the port block bolts slightly in my baseplate, just for this expected occurrence. All of a sudden, when everything was getting very close, it started to turn over by itself, not perfectly, but trying. A tiny bit more tapping and I had the engine tamed.

John

 

[1Kenny]

Keep playing with it and you will find the magic spot. When I built mine I thought how in the world can it be so hard to get running, there is only 5 moving parts. It took a week to build and two weeks to get it to run. I slotted the vertical base so I could sync it to the horizontal base. One day I put air to it and slowly turned the vertical base back and forth. Bingo, it started running.

Kenny

 

[vascon2196]

I just recently picked the engine up to attempt some troubleshooting. I hooked it up to the air compressor at the college (which is much stronger than my own) and brought the air up to 60psi. I don't go any higher than that because at that point any engine should be running. This thing was not doing anything......until I tipped it to the side! If the flywheel is facing up (lying down horizontally) the engine started cranking!

I was able to lower the air pressure to just about 30psi and at last...progress.

I am going to take the whole thing apart, check for squareness based on your comments and suggestions, and see what happens.

Boy this engine is fussy.

Chris