Driver bushings
I'm thinking of re-working an old Mantua General, but using different drivers. I am assuming the General used 1/8" diameter axles. The drivers I want to use have slightly smaller 3.0mm axles. Any thoughts on putting a bushing somehow or taking up the extra space in the axle slot? I think we are talking about 0.007" difference. I suppose another option is to make new 1/8" axles and turn down the ends to a smaller diameter to fit in the wheels.
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If memory serves, the General used the standard Mantua/Tyco "U" journals.
I'd try squeezing them over the new axles and glue or shim them in the frame if they're sloppy.

Dan M.
You could use .003" brass shimstock to bush the axles, placing the material as a liner inside the "U"-bearings. If you squeeze the existing bearings, it's a crapshoot if they'll even remain useable, and, at best, the displaced material would need to be trimmed just to get the coverplate reinstalled.

Respectfully Wayne, Shimming would work, but they'd be fiddly to keep in place.

I doubt that the displacement would be significant over .0035" per side.

I'd have to dig out my trig tables to calculate it, but a file would dress that pretty quick.

Another option would be to "Babbitt" the journals with solder and ream to size with a 3mm drill, not rocket science.

3mm I.D brass tubing would also work bedded in JB-Weld, (without the originals) I've restored carburettor shafts that way to pass emission tests. Just insert the lubed axles while it cures to maintain alignment.

It all boils down to what you're confident in doing.

Dan M.
I'm not familiar with the locomotive: does it have a one-piece cast frame like the Mantua Mikes and Pacifics, or a built-up frame like a brass steamer?
Regardless, with the frame upside down, I'd place a piece of axle stock over the shimstock, then force it into the bearing slot and clamp it in place. Trim the excess material which protrudes above the bottom of the frame, then trim the excess from the vertical portions which stick out from the ends, but leaving it connected at the bottom of the slot. Remove the axle stock and partially-formed shim, then trim the excess shim material, leaving a tab protruding outwards at the bottom of the "U". Use pliers to bend it away from the axle slot, and repeat this process at the opposite end. Once the coverplate is in place, the tabs will keep the shim from moving laterally.

Yes the model uses the same construction as the larger engines, but that is a concern, because the frame is much thinner.

We're talking 40+? year old Zamak, which is tougher than most white metals but has had time to crystallize, so I would urge caution with any applied force.

If pressing in shim-stock, I'd cut a notch in some scrap wood to hold the journals while pushing on them rather than risking the frame.

You could easily sweat them with solder in a wood fixture and forget extra tabs.

Dan M.

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