The latest addition to the critter fleet is this GE 25 Tonner.
The shell is Damin Keegan’s excellent design from Shapeways and the mechanism is a modified 12mm axle space geared turnback drive from Narrow Garage Japan. Thanks
@Chris333 and
@u18b for the links to the mechanisms. The chassis is 3D printed and nicely done.
I’ve had this shell for well over a year and had started powering it using a Bachmann 44/70 tonner truck. The axle spacing was right but the gear tower was centered and I was trying to use a shorter motor without much success. When I saw the link to the Narrow Garage chassis and his drawings showed the main part of the drive at 6mm width I knew it would work. The inside of the shell measures just over 6mm.
The drive comes with a 10mm motor so I remotored it with a 6x15 coreless. The shaft on the coreless is smaller than the stock one so I made a bushing that ended up only .004” wall thickness but it worked.
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I shortened the chassis and added a styrene cradle for the new motor. Photo shows the stock chassis on the left.
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I changed the stock wheels to ESM at first but ended up changing those to Tangent 36”. The stock wheels have a metal hub which rides in the 3D printed frame so I turned down bushings from brass stock to go over the now half axle wheels.
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I needed a way to hold the shell to the chassis so brass angles were glued to the squared up ends of the lower chassis section. The notch in the brass is where the coupler screw passes by. I milled the shell so the bottom of the angle was flush with the top of the coupler opening. Screwing the coupler to the shell traps the brass angle holding everything together and establishes shell and coupler height. The shell is printed with the screw holes already in it so I tapped them for 00/90 screws.
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The ground pad on the ESU Lokpilot Micro is about the size of a pinhead and it’s difficult to keep the solder joint from breaking. My remedy was to lay the wire so it exits the decoder opposite the stock wires then hot glue the capacitor side of the TCS KA-N1 keep alive to the decoder. This traps the ground wire to avoid breaking the solder joint and still makes a compact electronics package.
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Some thin double sided tape holds the decoder and keep alive vertical and it just fit up in the cab after scraping some thickness out of the cab ceiling.
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Since I was freestylin’ this one anyway I used elements from multiple prototype photos. I thought the external air cleaner on the hood was cool so I made one from brass. Railings are .008” phosphor bronze wire and the air whistle is a piece of brass wire drilled to accept an .008 wire “pipe”.
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