USAT H/W Truck mods

First: be sure to lube the axles, very little factory lube in the trucks, save those bearings!

As in the main page, there is excessive rolling friction, caused by a matte black finish on the wheel backs and carbon brushes on one wheel per truck.

While the USAT streamliners have the same setup, the backs of those wheels are a mirror like nickel plated finish with very little friction.

 Something must be done.

Construction:

3 axle truck with all metal bolster and sideframes and jouirnals, the sideframes mount to the bolster with 2 screws each.

All 3 axles are in journals. All 3 journals are in a single casting that is sprung with 2 springs, between the end and center axles. All journals have pressed in brass bearings.

The center axle has a journal bearing with a vertical slot to give it independence from the end axles.

So far it looks like an effective suspension system.

As some background information, here is a guide by Ted Doskaris, which documents a process and parts to mount USAT H/W trucks on Aristo H/W cars, which has some good and unique information on the USAT trucks themselves.

https://www.camarillopacific.com/wp-content/uploads/2022/10/AristoHeavyweightUSAT_3axleTruckCamPacAdaptorInstallGuide.pdf

Drag and what to do:

When I first got these, I got stringlining with very few cars. I even eliminated the S curve you see in my home page. Since I could easily run a 10 car USAT streamliner I could not figure what the issue was. Eliminating the S curve did not solve all the issues.

As in the main page the issue is excessive friction with the 2 outer axles using carbon brushes on the matte black wheels.

New wheels to pick up power with low friction:

So getting together with my friend Dave Stubbs, we decided to swap out the wheels for ball bearing wheels with power pickup. There used to be a lot of options, but over the years:

• • the Aristo BB wheelsets are gone
  • Accucraft makes them, in 1:29 and 1:20.3 freight sizes, no published size, but probably too small for the passenger cars, and they are not great quality
  • LGB has made them for years, but wrong size, plastic centers to the chrome wheels and really sloppy ball bearings.

We finally found that Train-Li in Reno, NV had access to to some very high quality stainless steel ones, and they are close in diameter.

Dave decided to replace all the wheels, to make them the same size, but I thought that replacing the center axle only on each truck would work.

Stock wheel diameter: 1.24", Train-Li: 1.22", so a difference in height to rail only 0.01", so I felt confident that using one of these in the center position would work, and also the center wheel is less visible, so the shiny stainless steel would be less noticeable (planning the black felt marker trick anyway). Also a lot cheaper to buy 2 axles per car than 6 !!!

In addition, with the nice "keep alive" circuit in the cars, I figured that 4 wheel pickup at DCC voltage would be fine, no need for more pickup.

Well, finally after about a year, I embarked on the project, pulling the trucks apart for the first time. This is when I discovered the vertical slot bushing for the center axle, so good in that wheel diameter is pretty much a don't care, but only the weight of the center axle will have provide the contact pressure for the power pickup.

 Off I went, removing the carbon pickup brush assembly on both trucks, regauging all wheels. The USAT outer wheels can be regauged by simply twisting and turning, and of course the USAT we all off, many undergauge, like 1.55 - 156" back to back.

The ball bearin g wheels needed to be disassembled, and the center tube milled a bit shorter. Strangly they were overgauge.

Put the car on the track: SHORT! Huh? Oh, the usat truck is all metal, and the USAT wheels have insulators on BOTH wheels.

The ball bearing wheelsets have "live" axle stubs, so I was effectively shorting the rails through the all metal truck.

Dave has an ides to replace the USAT bolster with some FR4 board (Fiberglas Reinforced), and thus solve that issue, but now the USAT axles, being solid will be an issue, since each sideframe will be live to the rail it is over.

I'll probably slice the USAT axles in half, and use a delrin tube to insulate them from each other. I can also fine tune the tube length to get just the right gauge.

Other mods

modify to increase down travel of outer axles, looking to remove the rectangular pad at the bottom of the journal. Will require removing bottom strap and either putting pins back in or tapping for a small screw.