Big Rob – power train

Jan 10th, 2017 | By | Category: Robot cars, Top story

This article describes the components I build by myself or I bought for the power train. The power train are all components the robot needs to mount the big buggy tires and to get the tires spin. The DC gear motors are very strong and that’s the reason why the power train has to be very stable. Additional to all the torque of the DC motors the payload of the robot should be high enough to mount an additional box on top of the chassis of the robot for further technical equipment.

The picture below shows the main pieces of the power train I bought to get started with the design.

  • Figure 1: Is an 8mm in diameter and 120mm long silver steel axel. I bought a 8mm x 500mm silver steel and cut the axle into four pieces.
  • Figure 2 & 3: Are the mounts for the big buggy tiers. This is a typical mount from Reely I bought to mount tires on axles. Reely 511492C aluminium CNC hex rim hub.
  • Figure 4: Is an 8mm inner diameter zinc alloy pillow block as a flange bearing. I used this type of bearings in my robot to mount the axels.
  • Figure 5: Is an 8mm inner diameter pillow block with a mounted ball bearing. Because of my short 120mm axles I was not able to use this pillow block in my robot.
Custom-Build-Robots-Big-Rob details

Custom-Build-Robots-Big-Rob details

The very first design of the power train looks like shown in the picture below. Because of the short axle I could only use one ball bearing in my robot. But I think this is enough.



The next picture shows the power train together with the dc gear motor and an additional shaft coupling coupler to mount the axel too the dc motor drive shaft. This coupler has also an 8mm inner diameter.

The name of the DC gear motor is GW31ZY. You will find this motor with different speeds. I used a 12V version with 35 rmp and a very high torque of round about 15 kg/cm.



To machine the plastic of the grey box was very easy with a normal drill. I invested a few Minutes to find the best position to the mount the dc motor and to drill the holes for the power train. To mount the DC motor I used four L shape Mounting Brackets. Then I mounted the dc gear motor into the box together with the power train. Afterwards I marked the position of the ball bearing to drill the holes for the ball bearing into the box.

The next pictures shows how I mounted everything into the plastic box.

Big Rob 4x4 dc motors

Big Rob 4×4 dc motors

Component Overview

This is a list of the components I used in my robot to build the power train. I used the Amazon online shop to buy all my components because it is very easy and I could rely on the good customer service.

Preis: --
4 neu von EUR 22,300 gebraucht


All the other components like the Raspberry Pi or the motor driver are listed in the following component overview.

Additional Robot Car Component list


The next pictures shows the Big Rob by -12 °C driving around in the snow.




The hardest part of this project was to find everything to build the power train. I invested many hours to search for the components and to think about the setup. With the Reely hex rim hub it was very easy to mount the big tires on an 8mm axel. The very strong 12 V DC gear motors are perfect as engines for my robot. Actual I am powering the robot with two 7.2 V power packs I switched together parallel to get 14.4 V for the DC motors.

Article list - Big Rob:

Big Rob – A Raspberry Pi powered robot
Big Rob – power train
Big Rob – Software comming soon

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