Bad Overland drives, total write-offs?

[Jay Criswell]

Hey Butch,

Yeppers! That's what it is.

Jay

[Chris Webster]

I am also wondering if I am the only one whose eyebrows went up when Bill said he owned THREE centipedes.

I'm not surprised.

On ebay, they have been going for less than more typical OMI diesels. Plus, centipedes seem to be catnip for SPFers -- last weekend, I visited an HO layout of Altoona and Horseshoe curve over which FOUR centipedes were pulling a freight.

[R.K. Maroon]

Jay -- thanks for the information regarding the kingpin and the desire for your drive shaft pivot points to be on that same axis. I had never heard this before but once explained is seems naturally correct. If I am thinking about this right, such a setup would have little or no piston action in the shaft. I am opening a beer now, as I have learned something today and can relax for the remainder.

Jim

[bob turner]

It actually reduces the angles required of the joints.

[riogrande491]

Guys -

On the later drives with a smaller Pittman 83x3 slung low and part-way through the frame, two aluminum tube shafts to axle gearboxes, I have a couple axle gearboxes that at times can lock up solid when coming to a stop, especially if the gearbox screws arrived loose. They don't always lock up, but only seem to do it occasionally when they come to a stop under a significant load (train running upgrade.) Otherwise they run just fine. Backing to take slack unlocks them every time. I've only seen this on gearboxes that are not driven by the motor shaft.

After removing said axle gearboxes from the trucks I can usually lock them up in my hands. Perhaps a top land on the worm is hitting the top land of the worm gear. Chasing the usual suspects including cleaning and inspection proved fruitless.

Any thoughts on how to remedy this? Alignment tips while tightening the gearbox screws? There is an awful lot of free play with the gearbox screws and it is easy to get either the input shaft or axle visibly out-of-kilter. The screws do a poor job of providing an accurate alignment. Trashing them isn't an option, and I can't afford the drive rebuild of those I would trust.

Any ideas?

Thanks!

[up148]

Hey Butch,

Yeppers! That's what it is.

Jay

Jay,

From the looks of the correct "B" unit side frame, it looks like a 1993 run, not the 1st run. Unless you removed the "fake" fuel tank that hid the OMI tank drive (that makes sense actually) on the original run model. Regardless, I'll bet it runs great. Is the "A" unit repowered with your drive too, or just a dummy now?

BH

[sarge]

Bob,

I'm not quite sure if I'm understanding you're description, but I think I know what you mean. Bear in mind, though, I might be way off-base with the below, since I don't have any of this stuff actually in my hands to diagnose...

Case 1; I have had some of Ajin's boxes wear very quickly such as the worm can overide the wormwheel. What you are describing sounds to me like they are already dreadfully worn, if the tolerances are already so sloppy the box screws are "adjusters". They aren't intended to be.

Case 2; Sometimes the wormshaft has too much slop fore and aft, making for a bind under load when the end of the worm is forced against the box; USH steam boxes are rather notorious for "cogging" in this manner. The solution is oiled washers fore and aft to keep the worm in one place and lubed. This also has the added benefit of keeping the worm in one place with respect to the wormwheel.

If the first case, especially if you bought these locos used, you are pretty much looking at new boxes, and you must be careful because, even though the box might look the same, the gears aren't necessarily from run to run.

If the second case, brass washers or very hard fibre make good thrust washers after being soaked in a light machine oil. Then keep everything maintained and lubricated.

There is no Ajin box that doesn't need operator maintenance throughout its lifespan.

[Robert]

Sarge, I have not heard of "oiled washers".

Do they result from merely soaking in oil?

Also do they retain this oiled quality?

Enlighten this curious Yank...

Robert

[E7]

There is no Ajin box that doesn't need operator maintenance throughout its lifespan.

The exception might be those green ones the stuff came in!

[sarge]

Sarge, I have not heard of "oiled washers".

Do they result from merely soaking in oil?

Also do they retain this oiled quality?

Enlighten this curious Yank...

Robert

That would be, hmmmm, washers with oil on them? Simples!

I do recommend the following little trick from low-speed mechanical drive design. If you need (let's use this simple example for clarity) a 0.100" thrust washer on each side of something in an oiled situation, use two 0.050" thrusts rather than one 0.100" one. Same dimension but two tend to keep an oil film sandwiched between them long after the one has dried out. Its a clever and very old mechanical design trick from the ancients now almost lost. Always use two thin ones rather than one thick one.

[Robert]

Somehow the way the oiled washers were being discussed, I thought there was something I needed to know more about...perhaps it was the fiber washers soaked in oil that made me ask the question. Ok simples...

Robert

[bob turner]

It is called "Oillite" and it is a porous bronze. It can be impregnated by soaking. Lionel used them. Probably not necessary in these already sketchy gearboxes - just use brass, and coat them with gear oil.

A lot of model train gearboxes, including the venerable Lobaugh, do not have proper gear mesh. That always results in gear failure.

[riogrande491]

Sarge -

Thanks for responding to my query! The axle gearboxes are some sort of zinc(?) alloy with inserted bronze bushings for the input shaft. All the ones in question are on previously-owned locomotives, both my own and one on a friend's diesel. When these were imported I was a young and "unrepentant HO scaler."

On one of my Overland GP30s every one of the gearbox screws were loose and I suspect that was done by the previous owner to mitigate problems. After tightening only one exhibited this problem, but persistently.

When I get a "round toit" I'll open that GP30 gearbox and see if there is evidence of gear wear and excessive free-play on both the input shaft and axle.

If I only there was a "magic geometric relationship" I would mill a custom tuning saddle to enforce that geometry while tightening down the screws.

Thanks for the heads-up about gear ratios. I had no clue that there was no consistency! That knowledge in of itself is worth its weight in gold. Again, thanks, Sarge!

If anyone else has experiences tuning 1980s Overland drives, please chime in! let's share the knowledge of those who have worked on these mechanisms and made them, in "Missouri speak, more better!"

Thanks in advance, y'all!

[sarge]

Robert:

Ah! I see what was confusing in my prose; my apologies.

I have used hard fibre, but over time they will go soft, so you get to maintain them, too. Just different maintenance, but hard fibre thrusters can be really nice and they do hold a light machine oil for a long time. You do have to change them periodically, and quite a few ancient drives use them as axle thrust-washers.

Bob;
Oilite bronze is something I've used for bearings against polished steel, but not in washer form. Bronze on steel with a film of oil is one of the best bearings going, even tailshafts on ships are often pillowed up with bronze bearing blocks. Beautiful.

[Robert]

Robert:
Ah! I see what was confusing in my prose; my apologies.

Tossed and turned all night on my retreat into "simples". Now I will have to nap for a while to regain my usual state of mind.

I have heard of Oilite Bronze bearings.

Robert