CT1 Tank gearbox by Iliya Cerjak

Build it yourself Tank transmission for use in radio controlled tanks & other tracked vehicles.

Tank transmission tank gearbox for radio controlled vehilces
RC Tansmission logo

3D CAD data and/or 2D production drawings available on request.

Go here for more downloads.


Tank gearbox RC transmission CT1

CT1 2 channel controlled

2 x Forward-neutral-Reverse output

1/30 gear ratio



CT1 -Tank gearbox bi-directional dual clutch




Typically designed for large-scale tanks. Suitable for any tracked vehicle, this universal transmission enables full control over the vehicles movement with 2 radio-controlled channels (servos). 1 engine powered input shaft is transferred to 2 output shafts. Both output shafts have servo controlled clutches and drive direction, which can be operated on-the-fly. The engines output shaft can be directly coupled to the input shaft, no need for an extra clutch (clutches are build into the transmission). When used in combination with the CT2 or CT3 you create a 2 or 3 speed tank transmission.



Technical details


This gearbox consists out of 2 bi-directional clutches, each driving one output shaft to power a tank. The 2 clutches are operated by 2 servos. Each output shaft has 3 modes, forward, reverse, and neutral, all operated by one servo.  By proportionally controlling the clutch proportional steering is accomplished. A final worm-worm gear transmission of the output shafts makes the tracks automatically braking, so no need for extra brakes. One can imagine controlling a vehicle with this transmission by the 2 stick movements on a remote; both sticks forward, the vehicle moves forward, both sticks backward, the vehicle moves backwards, move one stick gradually back, the vehicle gradually makes a turn, one stick fully backward, other fully forwards, the vehicle turns about its axis. The animation below explains the working principle.


Needed materials: aluminum bar 50x8mm, Aluminum sheet 4mm, brass round 10 & 40mm, Perspex sheet 4mm and miscellaneous fasteners. All gears are stock size, available for example at Sterling Instruments , RS components, Conrad or any other small drive components supplier, so are all the bearings and shafts.


Above a CT1 & CT3 build by a customer.

His review; ‘Thank for the plans they are working out great…

My name is Chris and I am a Machinist for about 22 years now.

This project has been one of the most favorite ones I have ever made….



Animation of the bi-directional clutch.                     Animation of the tank-gearbox.


(Click on picture to see larger image)



Exploded view and assembly.                                 Outer dimensions of the assembly.




The drawing set consists out of; One assembly drawing, with detailed comprehensive exploded views and cross sections. A detailed parts list, manufacturing notes, and all drawings with the parts’ dimensions, manufacturing instructions and details.

3D CAD data and/or 2D production drawings available on request.

Go here for more downloads.



Click on picture to see larger image)


CT1 Main assembly drawing.




The next pictures show the real thing. On the first picture a top view of the CT1 completely assembled. The second shows the CT1 in parts. Don’t mind the very low quality of the parts, I made most of them myself with very little patience. See the CT1s build into the Abrams, Mike’s Stuart, and several others build by customers.


(Click on picture to see larger image or video)

CT1            CT1_exploded_perspective

CT1 top view.                                       CT1 in parts.

Test stand


Having finally build my CT1 and CT3 I had to put them through their paces. The test stand consists out of a 25cc 2-stroke Mitsubishi engine driving a CT1 through a CT3. The engine is mounted on rubber damping mounts onto a wooden base plate. The CT’s stand on aluminum poles, flexible couplings connect the drive shafts. I put all parts together, drowned the CT’s in WD40 and started the engine. Et voila, everything worked as planned. In the video you see the clutches being frantically operated and the gearbox shifting through its 3 gears. To determine the output torque I clamped a vice on one of the output shafts; it was possible to tilt the whole vise turning the input shaft by hand and applying only a small force on the clutch.


(Click on picture to see larger image or video)

CT1_CT3_combo               CT1_CT3_teststand

The CT1&CT3                                       The test rig





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