VEX VP motor mount plate plastic deformed

The plastic plate that attaches between a motor and the VP gear box is easily deformed when tightened beyond snug, making me a little nervous. Is there a way to fix/improve on this?
Also, I can’t find in the instructions whether to use loctite. Seems like a good idea.

Use Loctite.

(I had previously incorrectly stated here that Loctite eats nylon. I’ve since been corrected by Nate_Laverdure and Chris_is_me that Loctite eats polycarbonate, not nylon. Thanks for the correction!)


We make our own custom plate out of 0.125" 6061T6 aluminum for high stress/load applications.

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The easy answer is: don’t tighten it beyond snug. Though this is hard to implement when you have a fleet of high school students that don’t know how tight to torque things down yet. We have squished a few of the plastic versaplanetary parts.

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Is it just a flat sheet with the correct hole spacing?

No, we also pocket out vents so the motor can intake air.

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No, this isn’t right… From the Loctite Design Guide for Bonding Plastic:

Neat, would you mind sharing pics/CAD?

You’re thinking of polycarbonate; glass filled nylon is Loctite safe. Please use Loctite on VP gearboxes; removing it is the fastest way to heartbreak as a loosely assembled gearbox can easily bind and eat itself.

This deformation happens in any case - there’s just not a lot of material on the outsides of the holes. Most of the time it’s not a big problem - the bolt holes aren’t what is locating the motor mount plate to the gearbox, they are just securing it.

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I know there exists a metal motor mounting plate but I dont see any reference to them to Vex’s website? Do they still sell them or was that a VP-V1 thing?

I’m pretty sure the metal plates are from an earlier VP generation. We still have some kicking around in our shop, but we’ve found that the holes in them don’t always line up exactly with the VP-V2 parts.

The metal motor plate did not use the motor boss to locate the motor in the gearbox. It used the motor shaft. With some motors this worked okay (e.g. the BAG) but with others (e.g. the RS550), runout in the shaft and other misalignment could really hamper the efficiency of the gearbox. The plastic plates remedy this by using the boss of the motor to locate.

CAD can be found on the VEXpro website. My team also machined our own plates and we just worried about the mounting and venting geometry. I don’t think the boss on the side that goes in the gearbox is important with metal plates.

Once you’ve disassembled and reassembled these hundreds of times you get to know how things should feel. On the plastic mount plates, you’ll want them snug but not overly tight to the point where things are deforming. A drop of loctite on the bolts definitely helps.

And remember - if you get it all assembled and you can’t turn it by hand on the 1 stage ratios or with a half inch wrench on the higher ratios (even 100:1 with a little force), something is binding. Take it apart and try again. Every now and then things need to run a little the first time too and they’ll move easier after that, especially if it’s the first time they’re running. Make sure you grease everything lightly - I have seen teams literally fill the VP with grease and it actually doesn’t run as well as using a smaller amount.

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Ha, I actually never checked if they had the cad for the mounting plates up

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