Building Jerry's Donkey

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Jerry,

Nice self portrait - a bit flashy ::)

True to form my bandwidth improved this morning and it's beautiful to watch. :bow:

Best Regards
Bob
 

Great work Jerry!

Go slay 'em.
 
I love it! Are you going to post plans when you're finished?
 
No, I'm not "Iron Man". Here is a picture of me and "Iron Man" together. That's "Iron Man" on the right.

Meandironman.jpg



 
Well, into the shop to deal with the clutch lever. I had a general idea how I was going to work this out, but things changed a bit as I got into it. Several months ago, I posted some drawings that looked good but as I got into it things changed. I planned to use a pin that was in a hole crossdrilled in the actuator shaft. It woud engage slots cut diagonally in a bushing that simulated internal threads. I had a hazy idea how I was going to get the pin in the shaft and the shaft in the bushing and the bushing in the frame, but it got way to complicated to be built.

The final version uses a solid shaft with one 1/16" slot milled across it at 70 degrees. The single pin that provides the axial thrust is disguised as a grease cup on top of the frame in the pictures below. This pin engages the slot and when the shaft is rotated with the handle through an arc of about 55 degrees, the shaft is moved about 3/32" pressing on a pin that moves in the shaft bore, pushing on the clutch bushing and engaging the clutch. Sounds to simple but it works a treat. This is the right hand thread on the main hoist. The left hand thread needed for the front hoist just means that the slot will be milled at the opposite angle. Problem solved.

I didn't take pictures. For one thing inspiration and execution was happening so fast, I could barely keep up. For another thing, the wife was babysitting both of the great grand daughters, so she got dibs on the camera. I brought the results home and took some pictures of the assembly. It may not be ready for prime time but this is a work in progress. My philosophy is make it work, then make it pretty. I know, the fasteners are crappy and the finish is rough and the grease cup is way out of scale, but its progress. Have a look.

Jerrysdonkeyclutchlever036.jpg


Jerrysdonkeyclutchlever038.jpg


Jerrysdonkeyclutchlever039.jpg


Jerrysdonkeyclutchlever040.jpg


Jerrysdonkeyclutchlever043.jpg


If that,s not enough pictures, tell me, I got more.

Jerry
 
Jared said:
I love it! Are you going to post plans when you're finished?

Jared,

I didn't overlook your question about posting plans, I just forgot to answer. The truth is I don't know. I am not a trained draftsman and although I can produce a 3d model with full motion, and produce a working drawing with the dimensions I need, the part often doesn't get built that way and I don't always go back and modify the model and the drawing. The drawings and dimensions make perfect sense to me but a real machinist might be so irritated by them that someone might get hurt by flying tools.

Still, if someone wanted to build one of these or for that matter if anyone wanted to build any of my other original design (Weeble, or 3 Cylinder Spider) I would be willing to help, including drawing with the above caveat. But lets see if I can get this thing completed first.

Jerry
 
It sure is turning out to be a pretty little winch, Jerry.
You're doing well on both fronts.

Dean
 
Wow what a neat machine. I just spent the last 45 minutes reading the entirety of this thread.

That's just amazing Jerry!

 
Looking great Jerry....keep the pictures coming....but building has dibs ;D

Dave
 
Back to the shop. Vacation is over, including a week in the north Georgia mountains complete with an unexpected bear encounter. I should be feeling restored and raring to go but the heat is so intense that it overpowers my shop AC by noon so I'm going to work short hours until it cools off some.


Here is a shot of the crankshaft from the American Hoist Brochure. Note the eccentrics integral with the crank webs.

CrankfromBrochure.jpg


Here is my version.

CrankShaft003.jpg


This looks like a straightforward assembly but there are hidden pitfalls. The original shaft has the webs Shrunk to the shaft with a square key. The gear also fits over a square key but it is not obvious how it is secured. I'm not setup to cut internal key ways and there is not room to use a grub screw so I decided to solder the web disks to the shaft.

That presents more problems. How do I fit the gear and the oillite bushings. I could fit the pieces to the shaft before soldering the webs but I know I will regret that in the future if either needs to be replaced. The solution that I came up with is a two piece shaft. The shaft is milled to 1/2 thickness for a length of 1/2". I was going to join them inside a collar but there is the gear which will serve the purpose. What may not be obvious is that the two halves of the shaft are not clamped together. They are jacked apart inside the gear. The grub screw passes through a clearance hole in the gear, threads into one half of the shaft and presses against the other half, forcing the two halves apart, griping the gear and making a surprisingly rigid assembly.

CrankShaft004.jpg


Thanks for watching

Jerry
 
Jerry,

That's a really good tip :bow: ....way cool Thm:

Philly
 
Bogstandard said:
A great solution Jerry, two birds with one stone or should that be grub screw.

Bogs

Grub screw conservation is everyone's responsibility. I'm just doing my best to be responsible.

Jerry
 
Gerry,

Another great innovation from you. :bow: :bow:

Best Regards
Bob
 
Now, that's model engineering!
Nice job, Jerry.

Dean
 
Thanks to all who are following this build and special thanks to Dean, Bob, Kvom, Bogs, Sam and Philly for taking the time to respond. What I enjoy most about this hobby is the small AHA! moments when a surprising solution jumps out at you. It is also great to be able to show it to an appreciative group of model engineers around the world.

There are lots of challenges remaining. In spite of the fact that I have built several engines in the past, I have never built a conventional double acting cylinder with a D-valve. I have no plans so I have to work out all the details and dimensions myself. Not really difficult if you know how but I don't. The interactive Zuener diagram written by Charles Dockstader has been getting a real workout and I think I've got a pretty good set of dimensions worked out.

The cylinder has a .625" bore and a 1" stroke in keeping to 1/10th scale.

The eccentrics have a center offset of .0935" which gives a valve travel of .1875"

The steam valve slots and the exhaust ports slots will be 3/32 (.0934)" wide wit a 3/32" flat between them.

The valve cavity will be .282" wide and the valve plate will be .470" wide.

These dimensions produce no lead, no lap, 100% cutoff. There is no expansion and no compression.

The engine will run on compressed air.

Would performance be improved by tweaking any of these specs?

Thanks in advance for your suggestions.

Jerry



Edited to correct loose decimal position and to correct eccentric throw. (JLG)
 
Just discovered this thread. Great build Jerry! That is some really fine work.

Chuck
 

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