Vex VersaPlanetary Gearbox Heat Problem

[matthewkennedy]

We've been running a VEX VersaPlanetary gearbox on an AndyMark 550 set up as a 1:1 (basically just using it as a bearing). Even with such a simple setup, the gearboxes are generating an obscene amount of heat. With no load and the motor running at 12v, the gearbox gets very hot to the touch, almost immediately. We've taken a few of them apart, and found one bearing that had lost a ball. We also have another gearbox set up as a 100:1, and it also gets hot in the same manner.

Is it normal for these gearboxes to get so hot? Are we ruining bearings? It seems like if the gearboxes were designed for the motors, and if we assembled them correctly (which we THINK we did...), they shouldn't get this hot. None of our other types of gearboxes get this hot.

Thanks in advance for any help!

[Dale]

Other teams have run into this as well. Start reading at post 118 in this thread (http://www.chiefdelphi.com/forums/showthread.php?t=111360&page=8&highlight=small+wheel)

[Paul Copioli]

First off, the VersaPlanetary gear boxes were not designed to be used 1:1 with a 19,000 RPM motor. You are at the limits of the bearing's speed ratings. We do not sell the gearboxes for use as 1:1 gearboxes.

With that said, we designed these gearboxes with FRC teams in mind knowing they would modify them. Many, many items used in FRC are used outside their intended purpose. We just put a few hooks in the design to help teams use these gear boxes in many different ways (like the CIM mounting, for example).

The heat is not a problem. The ring gear section is very thin and the entire gearbox is made from aluminum. That combination conducts heat very quickly. All of the other gearboxes are getting this hot inside, but have either steel or thick aluminum housings and do not conduct heat to the surface as quickly.

Running the gearbox at 1:1 with an AM-9015 (free speed of 19,000 RPMish) is near the limit of the bearings. Also, if you have a fully charged battery you probably are at about 13.5 volts which means the free speed is even faster. Something to consider when using the VersaPlanetary at 1:1.

Paul