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 21,990 gebraucht
Reely (511492C) Tuningteil Alu-CNC-Felgenmitnehmer 6-Kant (4 St.) (511492C)
GW31ZY DC 12V 35RPM 1:218 Reduction Ratio 15KG.CM Double Shaft Worm Geared Motor
Price: $46.96
1 new from $46.960 used
  • Product Name: Geared Motor
  • Model: GW31ZY-A35
  • Rated Voltage: DC 12V
  • No-load Speed: 35RPM
  • Rated Speed: 26.5RMP
  • Rated Torque: 15KG.CM
  • Rated Current: 1.8A
  • Shaft Size: 8 x 13mm/ 0.31" x 0.51"(D*L)
  • Female Thread Diameter: 2.5mm/ 0.1"
  • Motor Body Size: 30 x 55mm/ 1.1" x 2.2"(Max.D*L)
  • Gear Box Size: 60 x 40 x 25mm/ 2.3" x 1.5" x 1"(L*W*T)
  • Wire Length: 10cm/4"
  • Main Color: Gray
  • Main Material: Metal
  • Net Weight: 365g
  • Package Includes: 1 x Worm Geared Motor
uxcell Hardware Metal Lathe Round Bar Stock Rod 19/32" x 5/16"
Price: $5.00
1 new from $5.000 used
Made of metal, 15cm length and 0.8cm diameter.
Widely used in hardware, molds, and the occasion of the mechanical transmission.
Pillow Block Bearing, Letool4pcs Zinc Alloy Diameter 8mm 5/16" Bore Ball Bearing Pillow Block Mounted Support Kit
Price: $10.99
You save: $1.99 (15 %)
2 new from $10.990 used

Easy to install.
Durable with high precision.
Can withstand great weight.
Angle between the inner bearing and outer fixing ring is adjustable.
Pillow Block Bearing is widely used in various of machinery, such as machinery and equipment, conveyors, machine manufacturing, ect.

Please read the instruction to confirm it is the correct size the bearing you are looking for.

Package Included:

4 x Pillow Block Bearing
CNBTR Zinc Alloy KFL08 Flange Pillow Block Bearing Housings 8 mm Diameter
Price: $4.38
1 new from $4.380 used
Material: zinc alloy
Color: silver
Inner diameter: approx. 8mm/0.32 inch
Outer diameter: approx. 27mm/1.1 inch
Length: approx. 48mm/1.9 inch
Height: approx. 12mm/0.48 inch
Weight: approx. 27g
Product Name : Flange Pillow Block Bearing
Single-row deep groove ball bearing insert accommodates misalignments between the shaft and the housing.
Two-bolt flange-style housing for a ready-to-mount installation where surface and guided shaft are perpendicular.
Pillow Block Bearing Flange Block Bearing is widely used in various of machinery, such as food machine, conveyering systems, machinery and equipment, conveyors, machine manufacturing ect.
Please read the instruction to confirm it is the correct size the bearing you want.

Package include:
1x Flange Pillow Block Bearing
Reely 1:5Roue complète pour MonsterTruck avec jantes 6 rayons et profil de pneus Noir Profil Block (112181C
Prix: --
0 neufs0 d'occasion
  • Adapté pour type de modélisme : monstertruck
  • Conditionnement : 1 paire
  • Convient au modèle (modélisme) : Monstertruck Breaker II 1/5 (239990)
  • Couleur des jantes : noir
  • Design des jantes : 6 rayons
  • Diamètre de pneu : 205 mm
  • Entraîneur de jante : 24 mm 6 pans
  • Largeur des pneus : 90 mm
  • Type de pneus pour voiture RC (catégorisation) : roues complètes
  • Type/profil de pneu : Block-Profil
  • Échelle : 1:5


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 – Raspberry Pi robot
Big Rob – Raspberry Pi robot power train
Big Rob – Raspberry Pi robot motor driver BTS7960B and Python program
Big Rob – Raspberry Pi robot outdoor camera
Big Rob – Raspberry Pi robot with differential GPS
Big Rob – Raspberry Pi robot with nice teeth
Big Rob – Raspberry Pi robot Peak Power Pack power supply

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