HOn30 AHM Minitrains Plymouth Frame Adapter

Here is an adapter to retrofit a Tomytec TM-TR02 chassis into a vintage Minitrains Plymouth.

The vast majority of original Minitrains suffer from split gears. To fix this I decided to re-power mine with a more modern and easily sourced mechanism. To achieve this, I designed this adapter in a way that it can be easily removed and the original chassis reinstalled if ever desired. 

Tips for printing:

Print the adapter of your choice (regular adapter or knuckle version) with the bottom of the adapter towards the print bed. Use support under the overhangs for the pockets on the bottom and under the front tabs. You do not need support for the tabs in the middle.

I printed mine using black petg with a 0.12mm layer height.

Assembly:

What you’ll need: AHM/Roco Minitrains Plymouth with original chassis removed, TomyTec TM-TR02 chassis with its long coupler extensions, 4 M1.6x4.5 screws, and additional weight.

To mount the TomyTec chassis to the adapter you have to first disassemble the chassis. Brooks 3D Models has a great video on how to do this here: https://www.youtube.com/watch?v=y7HveautnHE (stop after step 5) With the chassis split into its 3 major components add the weight portion to the top of the adapter and use the M1.6 screws to secure it from the bottom. Remove the long coupler extensions from the sprues included with the chassis and add these to their spot on the base of the chassis (these are used to fit into notches in adapter to keep the chassis from rocking back and forth). Insert the wheeled portion up from the bottom making sure the contacts are aligned and the coupler extension fit into their notches in the adapter. Snap the motor back on top sandwiching everything together. The Plymouth frame then slides over the adapter and the tabs on the outside lock into the holes on the front and the slots in the middle of the frame, the taller section of the adapter goes towards the rear/cab. I find it’s easiest to start the front tabs towards the middle of the frame and slide the adapter forward while gently prying the sides outward until you get it into the correct position and all the tabs are locked in, the frame should snap tightly around the adapter. (Depending on your printer/settings you may need to sand/file the tabs slightly to get a perfect fit). Next add some additional weight. I used Deluxe Materials Liquid Gravity in the 4 corner pockets on the underside of the adapter securing it with super glue and added some additional weight in the cab and behind the radiator on the body. Finally add the body and you’re good to go!

Final Notes:

The wheels won't exactly line-up with axle box detail on the frame, the TomyTec chassis wheelbase is 16mm while the Plymouth's is closer to 18mm. This however isn't very apparent during normal operation and is really only noticeable when you're handling the model and staring directly at the wheels. This is fine for me and I see it as small compromise to have a working model. It is a lot closer than using a Kato 4-wheeled chassis though.

This adapter won’t work with the frame casting from the BCH re-release of the Plymouth, they are just different enough. It will however work with the Funaro and Camerlengo resin Narrow Gauge Switcher body as it is basically a resin cast of the original Minitrains Plymouth (However from my experience it requires a lot of sanding, adjusting, and cleanup. Also from personal experience the quality of these can be hit and miss).

After much debate I did decide to include the adapter for the knuckle couplers. This modification is permanent and not for the timid and/or inexperienced modeler. Do this at your own risk as you can easily ruin the frame casting from the Plymouth. Depending on the quality of your prints you may need to file/sand the top of the notch to get the correct coupler height. You also need to modify the Minitrains frame casting to make room for the couplers. I used a hobby knife with a chisel blade to carefully remove the draft gear detail, and after filing it down I glued it towards the top of the frame. I then carefully filed out a notch in the frame frequently checking it against the adapter and checking the coupler height. With the frame modified and assembled I glued the coupler box for an Atlas Accumate 23015 into the notch in the adapter. I then assembled the coupler and shortened the screw included to hold the box together. Micro-Trains 1015 couplers could be used aswell.

If you have any comments, questions, suggestions, or funny remarks feel free to reach out to me. I hope to be sharing more of my models in the future including a Class B Climax and some other Hon30 locomotives designed for Resin Printing

Best Regards,

Dr. Fixet