Two weeks ago I shared with you the first 3D test print for my new HO scale DT6-6-2000, you can find the post here. As you may recall I had a few issues with the print, but this week the second test print arrived and the results are very good.
I reprinted the two truck center halves and the four gears as all had issues to be resolved. The final kit will need four truck center halves and eight gears.
The gears came out even crisper this time, I assume because the axel section of the gear is now a part of the gear rather than held in place by 3D print residue.
The gears up close are very accurate, but there’s still some residue on the axel which will need cleaning off. To do this I simply wipe it off with paper towel. The holes for all the gears will also need cleaning out and for this I use a drill to ream each hole. If it has 3D print residue in the hole it will cause the gear to bind and add drag to the motor. If all the holes bind it may even jamb up the gears.
This time everything fitted as planned. The clip covering the worm gear will need to be taken off, and the drive shaft removed, in order to fit it into the chassis.
The gears, as shown below, are simply positioned in place to check they are a good fit. Before I tested them under power from the motor I did all the cleaning mentioned above, and lubricated all the axel holes with light oil, from inside and out. Then, with the wheelsets removed, I checked that the sets of gears turned freely by running my finger along them. With the wheelsets refitted the whole assembly was a little tougher to turn, but this was expected given there are 3 more gears than in the original configuration. But once the driveshaft and worm gear was fitted I was able to turn the whole assembly by hand.
The test fit into the chassis was also good; below you can see the original truck on the left and the new one on the right now facing the right way for a DT6-6-2000 or RT-624.
The clip covering the worm gear holds the truck in place, and a pin in the underside of the chassis fits into a hole at the center of the truck, creating the pivot point.
The white of the truck center is barely visible through the truck side frames, but it can be painted, taking caution not to paint the axel holes. With the chassis reassembled, albeit with one new and one old truck, I lubricated the gears using oil designed for plastic gears from LaBelle. You can find a post about these products here.
The final thing to do was test the new truck, so I connected a basic DC controller to the chassis (there is no DCC chip fitted yet) to see how well it runs.
In the video below you can see I ran the chassis at full throttle in one direction then threw it into the other. Because of the two large flywheels, the direction change is not instant, but it’s still a heavy load on all the gears and they seem unaffected. The chassis is in a foam holder because the first time I did this the sudden reverse toppled the chassis over!
The new truck ran very smoothly and the slow speed looks okay, but the real test will be when it’s on some tracks. As I’m an N scale modeler I only have a short section of HO track at home, but later this week I’ll be able to test it on a layout. The chassis has an 8 pin DCC socket so I can plug in a chip and see how slow I can make it crawl, but I feel confident that I’ve resolved the issue with rotating the trucks, so now it’s just a matter of finishing the shell. I’m currently modeling the cab interior and I will share that with you when it’s finished and before we go to test print.