Quote:
Originally Posted by AllenGregoryIV
JVN or Paul, can you explain how the VersaPlanetary motor connectors work? I've looked through the CAD and I see the set screw, the collar type thing with the slit and the place that it goes. My real question, "is the setscrew the only thing keeping the motor engaged?" I do like the access holes for the setscrew, and that you can swap motors with out removing the gearbox from the robot.
I'm excited to get VEXpro parts in.
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Allen,
The motor connection that the VP uses is one of the more counter intuitive engineered items I have come across in my time as an engineer. This technology is used on industrial robotic gear boxes all over the world and is becoming the common adapter for high rigidity, low backlash applications.
There are two basic principles at work:
(1) The motor pilot is not used, but the shaft is actually used as the pilot.
(2) The set screw really isn't used as normal set screw (clamping on a rigid shaft). It is used as a clamping lever to squeeze the C-coupling into an ellipse.
The C-coupler (collar type thing with the slit) and the input collar (the thing the C-coupler fits into are precision machined for an exact slight clearance. In addition, you use a specific C-coupler based on the motor shaft diameter. There is a different coupler for 3mm, 1/8", 1/8" with knurl, and 5mm shafts all with the same OD so they fit in the input collar. The clamping screw is tightened (don't really need that much tightening torque) and turns the C-coupler into an ellipse which locks it in place with no backlash. I have accidentally hand tightened a coupler before and it still locks solid. It took me over 9 months of rigorous testing when I was at FANUC to approve this technology for use on our robots, but after the testing I was sold. easy for replacing bad motors, easy for replacing the gear sets, and no more press fitting gears on motor shafts.
Now for high end motors like industrial robots use, this next benefit really isn't a benefit, but for some of the less expensive, non-high tolerance motors we use in FRC, I have found that this next benefit is really helpful:
Since you do not have to completely clamp the motor face to the VP mounting face, any shaft runnout misalignment between the motor shaft and motor mounting face is completely mitigated by just hand tightening the mounting motor plate mounting screws. Since the screws only act to keep the motor case from spinning, they only need a little loctite and hand tightening.
We will have detailed diagrams on how this all works prior to kickoff.
Paul