Kyosho Ultima ST EP Type-R RB6 transmission conversion

thingiverse

Okay, so, it seems to be impossible to get Ultima ST Type-R EP differential parts, so i created this quick conversion set, so you can upgrade the original transmission to RB6 (which you can still get parts really easily). So, what this set includes? - Stock style, but modified shock tower/upper control arm mount. Suspension geometry is 100% same as the original part. I only modified the transmission mounting point to accept RB6 transmission. - Rear chassis plate. I tried to reinforce it as much as i could. You should probably print it from CF Nylon. I printed it from CF/PETG. The best solution would be CNC it from aluminum, but its expensive. Lets see how this works out. I suspect the weak point will be the rear lower arm mounts screw holes. - Rear lower arm mounts. 1deg anti-squat and some degree of toe in. These are modelled from the original Type-R parts. (I reinforced these as much as possible). What you need? - Complete RB6 rear mount transmission and motor mount. (Transmission case that comes with the spare part set numbered UM508C.) - About 10mm longer dog bones/axles than stock. This is because RB6 diff cups are shorter. I suspect you need something like 95mm axles, but do your own measurements to verify. Im also releasing a chassis that offers a possibility to use RB5 rear chassis plate, which you can combine with RT6/SC6 lower suspension arms. They are 3mm shorter than Ultima ST stock arms, but then you can buy newer arms, use stock shafts etc. These parts are compatible with original Kyosho chassis, and also with my own chassis. UPDATE 26.1.2021! I included my modified motor mount to this upgrade package. The motor mount has integrated transmission input axle bearing holder, so you dont need the original holder anymore. You should print the motor mount from the hardest temperature resistant material you have. I printed mine from CF/PETG, but i suggest you should use nylon. 0.30mm layer height, 100% infill. Turn it upside down in a slicer and you dont need supports. Update 28.1.2021! I revised the whole motor mount. Theres no need to print new lower arm mounts, or shock tower mount or rear chassis plate. I removed the previous version of the motor mount, replaced it with updated design and also added transmission rear brace and rear bumper. To install the rear bumper, you will need two 25mm length x 3mm id and 5mm od aluminum standoff spacers. https://www.ebay.com/itm/M3-Aluminum-Round-Rod-Coupler-Nut-Standoff-Lightweight-Spacer-Stud-10-20-25-35mm/164396938141?hash=item2646d2339d:g:i6UAAOSw6bRfasRz These act as a support and they tighten up the rear of the motor mount to prevent any flex. And yea, it doesnt flex at all when assembled. I suspect that it should be possible to use this RB6 retrofit kit with the stock Ultima ST Racing Sports EP chassis also. I dont have it myself so i cannot confirm it, but looking at the pictures, it seems that if you use the whole retrofit set, (minus the rear chassis plate ofc, because RS-version has integrated rear chassis) it should work, you only need to drill two holes to your chassis for it to match the RB6 transmission lower mounting screws. If you dont want to drill your EP Racing Sports chassis, just print my chassis and swap it to your car. Its fully compatible with Type-R and Racing Sports parts. Update 29.1.2021 Added pinion/spur gear cover. Its designed around RB6 80T spur gear and 17t pinion (there should be space to change bigger pinions). Theres a hole in the gear cover for fast slipper adjustments, the "flange" is 14mm OD and 11mm ID. I will draw a plug for it later. Update 2.2.2021 Motor mount v.3.6 uploaded. Its compatible with all the other parts. Changes to previous release: - Lightened here and there (still as strong as previous version). - Made more space for the slipper system. - Changed the 2 aluminum post lengths to use 30mm standoff from previous versions 25mm (lighter and less material used when printed). - Compatible with all the other parts, no need to re-print them. I strongly recommend to use the v3.6. Update 3.2.2021! Added slipper eliminator .stl to the package. This is untested in action. I have printed it myself, but haven´t driven with it so i cant guarantee that it will be durable enough. To use the slipper eliminator, use the stock brass shim that comes with the RB6 input axle. Screw 2 3x3mm hex set screws from the sides of the slipper eliminator, so the set screws touch the input axle grooves (because the plastic simply wont last in the slipper). Drill three 3mm holes to the RB6 spur gear, using the slipper eliminator as a template. When using my motor mount: - First put the stock brass shim over the input axle. - Push the slipper eliminator over the axle and tighten the set screws. - Put three 3mm screws through the spur gear holes and put one 0,5mm washer on each screw. - Then just screw the spur on to the slipper eliminator, push the slipper eliminator shim thats in the .stl package over the axle and tighten the input axle end nut. UPDATE 11.2.2021 I kept breaking the rear chassis plate. Designed a stronger version of it and it seems to hold up great! The upgraded part is "Ultima ST EP-R UM-302 Rear Chassis for RB6 diff_v2.3 v1". I strongly recommend this version instead of previous. Enjoy.