Vex VersaPlanetary Gearbox


We are college engineering students on a robotics team. Our team is working to develop a semi-autonomous Mars rover capable of autonomous navigation, presence of life detection, equipment servicing, and more.

Currently, we are designing our drive system including the motors and any accompanying electrical hardware to control them. Our specs are as follows:

  • The battery is made of lithium-ion cells in a 6s22p configuration outputting 22.2V nominal, 25.2V max, 77Ah, and 220A max
  • We estimate that we need a total torque of about 2.35 Nm per motor and we are planning to use 6 motors with a 16:1 gearbox ratio
  • Our tentative wheels have a diameter of 8.5 in. and we would look to be going about 5mph max. Our rover would be about 50kg.

Regarding our gearbox, we were looking at potentially purchasing the VersaPlanetary Gearboxes in a 16:1 configuration with the VersaPlanetary Integrated encoder add-on. However, before we made the purchase I had a few questions regarding how these would interface with our system:

  1. We are planning to use the following motor with this gearbox and encoder: Motor. We were wondering which motor coupling would this motor need to be able to connect into the VersaPlanetary Gearbox in a 16:1 configuration (FYI: the motor has a key slot). Also, we will be using a case around the motor and an adapting plate between the motor and gearbox that will take about 7mm of the 20mm motor shaft. Will this be long enough for the 16:1 gearbox and encoder? Also since it looks like we are connecting two stages together for the 16:1 gearbox, would we need the optional VersaPlanetary 0-2 stage screw kit as well?

  2. We are planning to use the following motor controllers with our system: Motor Controller. We believe these motor controllers should be able to interface with the VersaPlanetary Integrated encoder as they both support PWM, however, we wanted to make sure that the two would be able to work properly? Also regarding the cable connector from the encoder to the motor controller, we found the recommended cable listed on your site. However, our motor controller does not take this kind of connector and only has 5 input wires. So we were planning on either splicing this cable open to making the proper connections or making our own custom connectors from parts online. Which approach would you recommend considering we also need to account for the PWM signals being transferred? Also, I know PWM signals may not be transmissible over a long distance. Do you know how long that distance is before we start losing signal quality?

Any guidance or advice would be much appreciated.


Joseph Kawiecki

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Woooo this is a long one. I’m just going to start off by saying: you might get better answers for your questions on Chief Delphi. Chief Delphi is a forum for frc, and it seems many of your parts are similar to that of FRC. Now onto the ones I CAN answer.

Just because your shaft has a key hole doesn’t mean it will mate with a pinion. Vex pinions in the versaplanetary gearbox are extremely small, and the motors this gearbox is meant for are smaller than yours. I do not believe your motor will mate with the pinion, even if you make a mounting plate. Also, if you still go this route, you will need the 0-2 stage screw kit.

Next up: Just because something supports PWM doesn’t make it compatible. Do your research, on the subject, and see (as I don’t know). PWM only means pulse-width modulation, and is like saying all motors can run with all types of batteries. Its just a type of signal, and not all connection types are compatible. You would have to check the mapping of the pads on the encoder and motor controller. I would suggest buying a pwm cable for your motor controller and splicing it based on that. Also, with PWM signals, they do fade out over time, however, this time is an incredibly long amount. Our frc robot has a run of about 20ft. So that shouldn’t be much of a worry for you.


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