Monday Mountain thread

[rrjjf]

Jay,

I also notices that problem with the drive line. As you know, most USH locos have a brass torque arm attached to the gearbox and fastened to a riser on the frame to prevent the gearbox from rocking. Lacking this, a motor shaft/gear shaft coupling that is attached to those shafts with set screws can also be used. I have made many of them.

Joe

[bob turner]

In my opinion, the beat solution to torque wrap-up is a very long worm shaft, a very short motorshaft, and a hunk of Toyota number O hose.

[Jay Criswell]

Yeah Bob, I think we all knew that and, yeah, it works. Not the most elegant but simple and effective.

Jay

[R.K. Maroon]

Is the gear box stabilized in any way? The way it looks in your photo the shaft will rotate and the coupling will fall out.

Good eye, Jay -- there is indeed a part missing. Here is a closeup of the topside of the gearbox:


You can see the adjustable stop to the left of the gearbox housing, and studs on the right, under the worm shaft, for its missing companion. I have the missing piece -- it was for some reason loose upon arrival. Note that the stop on the left is so gummed up that I am not sure it's really functionally adjustable any more. Some cleanup is needed here, for sure.

Would somebody please explain exactly what you mean by "torque wrap-up". Since a worm gearbox has its shafts at ninety degrees, it generates a moment (torque) about both the input shaft and the output shaft. Both of these torques have to be resisted by the chassis. Additionally, the input and output shafts themselves load like a spring from the driving torques. The stiffness in the gear train itself is usually pretty high (rubber tubing not withstanding) so if that is what is meant by torque wrap-up I will be surprised. I expect it to mean either that gearbox wants to rotate around the output shaft (the axle), which is what Jay seems to be interested in here, or wants to rotate about the input shaft (worm shaft), in a manner similar to the rocking of a V8 under the hood when you give it a little gas while idling.

If somebody would, please clarify this so in the future I will not have to assume just what is meant when this term is used.
Jim

[ScaleCraft]

In an automobile you have several torque-related attempts at wrap-up. First to be addressed is motor. Hence motor mounts, and in some extremely high-torque applications, steel mounts.
Second is rear (live) axle.....leaf springs....usually corralled by coil over and links or 4-bar.....but I digress.

Your motor in a locomotive is usually held pretty firmly from trying to rotate around it's axis.
You will find older units with rubber grommets that have perished and will attempt top rotate around their axis.
Worm shaft rotational forces, yes, might just try to lift one driver over the other (sort of like funny cars trying to get one headlamp over the other) but due to locomotive weight and axle bearings, generally success of that attempt is measured in failure units.

Like a live rear axle wrap-up on leaf springs, loco wrap-up is the rotational forces around the axle.
Having stops is..okay...BTDT....and keep the slides greased if it's sprung. If this is a fixed chassis, no springing or equalization, stops like you have, torque arm back to the motor, shims in the chassis will all work for me.
The torque arm back to the motor, for me anyway, is far more desirable for sprung chassis....keeping driveshaft flex point (u-joints or Toyopet Tubing) and the torque arm pivot at same place....or close..

[Jay Criswell]

To oversimplify or cause even more confusion (take your pick), when you apply power to a configuration shown in your photo, the gearbox with try to rotate. This behavior will cause your gearbox input shaft to rise or fall (depending on direction of rotation) and, if not stabilized your coupling will fail to stay engaged.

If what I think I see in your photo is correct I would say it's one of the poorest solutions I've ever observed. Jim, I don't mean that as an insult to you....you didn't build it.

I'll try to attach some photos of various torque arms and other solutions for mitigating the issue.

This is a coupling that Stu Kleinschmidt (forgive me if I spelled his name incorrectly). It's a model I repowered and replaced his motor mount with one of my castings



Various MG/USH/KTM mounts for stabilizing the gearbox input shaft.



A throwaway gearbox out of a PSC?Westside SP TW8. Of note is the torque arm. The rest is junk.


Something like what I believe Dave was describing.


Another junker. The torque arm is the most valuable part.


If space allows, and the customer doesn't mind seeing the gearbox, this is one of my preferred ways of dealing with it. Once again, using one of my cast motor mounts. Meant for connecting servo motors.




I don't know about you but I'm bored with this. Time to move on,

Jay

[ScaleCraft]

I like that coupling. If those cuts go all the way to the centreline, it's a modern version of the old spring coupling. Neat.

[Jay Criswell]

Dave,

Yep, they do.

Jay

[R.K. Maroon]

If what I think I see in your photo is correct I would say it's one of the poorest solutions I've ever observed. Jim, I don't mean that as an insult to you....you didn't build it.

No insult taken, Jay, and in fact it reinforces my own feelings. The metal-to-metal contact between the adjusting screws and the case of the gearbox looked like a bad idea to me. Nice photos, by the way -- thanks for posting.

Thanks to Dave for the clarification on what is meant by torque wrap-up. For what it is worth, I think wrap-up is an odd term in this context, as of course nothing gets wrapped up. The term would be more appropriate, for instance, in oil well drill pipe, which apparently wraps up several turns between rig and bit.

For what it's worth...
Jim

[bob turner]

Dave and I have similar backgrounds. Early autos had leaf springs holding the rear axle, and they would assume an "s" shape upon heavy loads such as acceleration and braking. For hot rodders they were not up to the job, and thus the advent of torque arms, called "traction masters" in the olden days.

The arms connected to the gearboxes are the same as traction masters, only smaller.

Jay's solution and mine are identical. He uses a more rigid coupling, which will work better for shorter worm shafts. As the worm shaft gets longer, the old Archimedes principle takes over and all you need is a hose.

I get a little torque wrap-up with my tender drive steamers. To counteract that, one truck is constrained laterally. On those, there is a bearing that takes the radial force of the worm shaft. I started out with ball bearings, but found that a properly lubricated solid bearing works just fine. The loads within the gearbox practically demand ball bearings.

[Jay Criswell]

Not all shafts are short.



Jay

[bob turner]

True, but the longer the shaft the better any solution works. Basic physics.

[rheil]

[quote="bob turner"]Dave and I have similar backgrounds. Early autos had leaf springs holding the rear axle, and they would assume an "s" shape upon heavy loads such as acceleration and braking. For hot rodders they were not up to the job, and thus the advent of torque arms, called "traction masters" in the olden days.

Bob,
I had Traction Masters on 3 different cars for drag racing. Although there were many variations of torque arms, Traction Masters was a proper brand name. Some days it is good to be old and remember those things.

[bob turner]

Dorazio, I was told:



It IS Monday!

[rogruth]

OH, OH, OH.
I remember seeing those locos and having some kind of a high.
Even when they were filthy dirty as most Pennsy locos were after WW II.

Very nice, Bob.