Building an HOn3 Mule, regauging an Athearn

[cnrglen]

Since I finally go some decent trackwork on my logging branchline, and my MDC shay isn't complete, I need an engine to test it out.
I found several Athearn conversions for sale on Ebay for 75-100$ but I figured I could build one foe much cheaper.
I also found an article in the October 1980 MR that details re-gauging athearn trucks for HOn3. I used that and some of my own calculations to convert an Athearn F-7 to narrow gauge. The engine was free and if it worked okay I figure I'll try it on a smaller Athearn unit and see what I can kitbash out of it.



I started with an older-model Athearn F-unit. The ones that come with the cast-metal sideframes on the trucks. The newer trucks with the square axle bushings won't work.

This unit was well-used and needed some wheel cleaning and lubrication before it started moving.
I ran it for a few minutes before disassembling it.
 

I then disassembled both trucks and cleaned all the parts with Isopropyl alcohol and let them dry.
 

six parts have to be modified in each truck, the four wheels and the two axles. The wheels need to have their metal axles respaced and moved outward. I used a NWSL sensipress to do this. The modified wheel will have .14" of the axle on the inside


The plastic axle/gear will also need to be shortened, but equally on both sides. I found that shortening the axle from the gear to the end to .113"did the trick. I used a sanding disk in my Dremel to shave the plastic axle down, checking with my digital caliper and a kadee wheel gauge as I went.


I also checked the completed wheelsets on my test track and they roll just fine.


Now re-assembling the trucks is a bit more tricky. Since the metal axles in the wheels have been moved, the wheelsets no longer just drop into the trucks. The wheels have to go in first, then press the plastic axles onto them.

Then install the rest of the gears in the on side, add the wheels into the other side, then place the two side together, pressing the wheels into the plastic axles and re-gauging them.


The only problem now is that the bottom truck cover will now fit so it will have to be left off. The MR article gives a template to make a new styrene cover the is glued on with contact cement.
 

I re-assembled the chassis and ran it on my test track. It runs just as well as it did when it was standard gauge.