The Joys of Proto48

One of the joys of proto48 is that nearly everything needs to be converted. Or maybe it just seems that way.

I bought an O scale RY Models 44 tonner a few years back and, with some track down now, it’s time to convert it to proto48. The locomotive needs everything done besides the conversion but I want something running so I’m just attacking the power trucks for now. Some of these models came in as proto48 and it was my hope that the power truck frames were narrow enough for the conversion and by golly they are! So it seemed all that needed doing was to replace the wheels and regauge them. It ended up being somewhat more work than that.

The first step was to pull the old wheels off the axles along with their nylon top hat bushings which insulate them from the frame. NWSL proto48 33″ wheels were drilled out to match the outer diameter of the bushing. But the nylon bushings had deteriorated and needed replacing so new bushings were machined in Delrin®. Not the best choice of material as Delrin® is slippery but that’s what I had to hand. I machined the bushings a few thou large on the outer diameter and drilled the axle hole a step down, #47 rather than #46. Best to be tight with Delrin® as it can’t be bonded with LocTite or anything else for that matter.

Firing up the Sherline lathe revealed that all the ways and means had stiffened up to the point of being unuseable. It’s been a damp summer and some rust was showing here and there. So, I took some time out to give it a navy yard overhaul. I disassembled the entire tool, attacked the rust and relubed everything. Now it runs like new again!

Back to the 44 tonner, adjusting the back to back (1.100 – 1.110″ for proto48) on the new axles revealed that the shoulders on the axles needed to be machined back 0.033″ to accept the tighter gauge. Loosening the dog screws on the gears and chain drive sprockets, the axles were removed and machined. Noticing that the power pickups were looking the worse for wear they were cleaned up and retensioned. Then all was reassembled for a test run.

And run it did! A little cleaning with acetone improved the pickup. Here’s a photo of the first power truck running on the freight house spur at St. George.

One power truck converted to proto48 running on freshly laid code 83 freight house siding in St. George. Oh, there’ll be spikes in every tie and joint bars every 39′.
Here’s the setup for machining top hat bushings. The Delrin rod is center drilled from the tailstock chuck,  machined down to the target diameter and then parted leaving a full sized rim.
Converted truck on the left. Original truck on the right. Notice the difference in the wheels! In front, a NWSL proto48 wheel and one of my top hat bushings ready for installation.

While I have things apart I’m going to replace the wiring. The motor is connected directly to the contacts on each power truck. Loss of pickup on either truck stops the loco. Also, DCC is coming before too long so I want separate pickup leads and the motor leads. The pickup leads from both trucks should be connected for true eight wheel pickup. Some sort of plugs and sockets will make it easy to disconnect the trucks if needed. I might make a temporary patch panel on some perf board for these plugs which could come in handy for the decoder harness later.


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