Wheel Shafts

Our wheeled robots are named after the size of the gear motor they use. How the wheels are mounted to the motors is also important. We offer three basic styles of robots that use different wheel mounting methods. We do this to offer different solutions to sideloading the motors. Motor gearboxes are not specifically designed to support a load. They are designed to rotate a shaft or apply torque. To protect the motor gearbox with heavier loads, the wheel axle should be supported by the chassis.

• Direct Mount (DM): The wheel and shaft are directly mounted to the motor.
• Single Bearing (SB): The motor is mounted directly to the wheel shaft, but there is an outboard bearing that helps to support the load.
• Double Bearing (DB): This is the most robust configuration. The wheel shaft is supported by the two bearings, and the shaft is chain or belt driven.

For more detailed information on motor mounting, visit our ATR Support page.

Direct Mount ATR

Direct Mount (DM): Some platforms use a chassis with a motor bolted to it and a wheel bolted directly to the motor shaft. This works fine for light loads, our IG32-DM4 4WD Robot is a perfect example. The durability of the robot platform is directly related to the durability of the motor and gearbox. The more weight you put on the chassis the more the motor has to support.

Single Bearing ATR

Single Bearing (SB): For larger loads we have designed a platform that takes the vast majority of the weight off the motor shaft by adding a longer shaft and supporting it with a ball bearing in the chassis. This platform is demonstrated in our IG32 and IG42 ATR examples. The motor is still coupled to the wheel directly just with a longer shaft that runs through a bearing.

Double Bearing ATR

Double Bearing (DB): For even larger loads we designed a platform that takes the load off of the motor completely like our IG42-DB4, IG52-DB4, and IG52-DB4-E. The wheel is bolted to a high strength axle and that is supported by two industrial-grade ball bearings. ANSI #25 chain and sprockets connect the motor to the axle. The bearings bearings take all of the load off of the motor shaft and put it on the chassis. This makes for a truly heavy-duty robot platform.

Chain or belt drive motors to wheels

Chain driving also provides another opportunity to gear down the robot to a desired speed. If you are not sure what size motor will work for you then the chain driving can offer some flexibility with speed and torque without having to change the motors. We offer chains and sprockets for doing all sorts of gear reductions. If you want the motor to spin the same speed and have the same torque as the motor, then you go 1:1 (i.e. a 15 tooth to a 15 tooth). If you want more torque and less speed then you gear it down like 1:2 (15 teeth to 30 tooth), so the motor will turn two times for per 1 wheel revolution resulting in half the speed, but twice the torque. If you have plenty of torque but want to speed things up you can go 2:1 (i.e. 30 teeth to 15 teeth) so every turn the motor makes the wheel will make 2, but you will have half the torque. The advantage of the chain drive is you can select any combination of reductions to tune your robot to work best for the payload and terrain. You want to try to tune it so the motor works at its peak efficiency during normal operation. Typically you do not want to gear up too much because you lose some efficiency with reductions. So if you are using a gear motor and have a 1:17 reduction in the gear motor, then use a 3:1 speed up, you are losing a lot of your power due to the inefficiency of gearing. We have several motors to choose from. If you are still having trouble deciding on the motor, select one of the pre-built kits that already have the motors selected as default.

If you are doing a very small robot see our Servo Modification Support Page so you can use hobby servos and modify them for continuous rotation.