Atlas Shay - Old vs New

[randgust]

The catch on the Atlas mechanism is that everything - vertically and horizontally - about the motor transfers directly to the worm to worm gear clearance above the tower.  No universals, no towers, no end bearings, no nothing.  Mess with the motor and frame at your own risk.  Nothing else but the motor mount controls that tolerance.

I've been looking at the mechanism for years trying to shorten it, or use it as the basis for a Heisler, and I'm stuck, I'll admit it.

I've tested the second run right beside the first run and both work just fine, actually.   

It still ranks in my mind as a mechanism that you modify at your own peril, and I'm amazed it works as well as it does.

Oh, and even getting those worms off the motor without damaging it, yeah, good luck with that.   I don't have the machine shop that Gerd does, I've got some of his parts he made for the West Side Heisler, and it's beyond what I can do myself.  He drilled holed in the end to pound the shafts out.  Yikes.

[mmagliaro]

Randy,
On your observations, I agree with you.  I am not a fan of having the truck gears just pivot below the worm and
having that gear mesh work just because of looseness in the gear mesh and "good luck", but that's how it works.

And yes, if that motor isn't in just the right position, the whole thing will never work.   It will be tricky. 
I guess when I get to this project,
my thinking is that I can make some sort of mount for the new motor that will let me shim it until I get it right and then
screw it down.  It won't be one where I can just plunk it in there with shims and epoxy. 

I'm not sure I'm going to try to reuse the existing worms and flywheels.  They are just Mod 0.3 worms, so any typical engine worm will work in there.   Why not just put my own flywheels and worms on a new motor and leave the old motor alone?
(Although I know that on least on occasion in my life, I have drilled into the end of a closed worm to see the shaft and then tapped it out with a punch, like you describe.   I didn't do anything in the least bit fancy.  I just drilled into the end with a pin vise and got it "close enough" to the center by eye that I reached the end of the shaft.)

[peteski]

This design does not seem to be as bad as one would think.  The 2nd run Shay I have has the motor visibly skewed in the chassis. and it still works. One of these days. when I do my technical review of it, the photos will show the misalignment.

The original Kato RS-11 and RS-3 locos has a similar design, where the worms were directly attached to the motor shafts. There are also European model locos which share this type of design.  I agree, the design looks really iffy, but it works surprisingly well.

[randgust]

I got a collection of spare parts when the first run came out including gears and a spare frame - just to tinker with.   I'll give you credit for getting the worm off that way anyway, that should work even without a drill press.    But I think I'll stand back and watch how you want to attack the next part.

The Shay truck has one feature never repeated - a 54" 4x4 truck wheelbase, shortest out there.  That's a pretty common geared locomotive feature, and you can swap around wheels on that steel axle.  And inside wheel pickups can work too.   The thing that stumped me was replicating that worm gear to worm clearance with a different motor mount.  Everybody has wanted me to try a proper Heisler, I know I can do a one-off, but what I'd really like to do is find a way to reliably modify the Shay chassis to work for a kit plan.  It's just way, way, too long.   For a 47-tonner, the truck center to truck center distance is more or less 24' 4".  Atlas Shay is 28' 6".  So if you could even get the one flywheel cut off and shorten the frame to match for about 4', it could work.