Star locking washers for motor screws (6-32)

Based on Foster’s quote below,
it seems like adding ‘star’ locking washers for motor screws as legal items would be a good idea, to improve robot reliability. I used lock-tite on the motor screws for the flat-bot double catapult, and I still can’t get 3 of those motors off. I removed one by dremeling a slot in the screwhead, and the heat helped soften the lock-tite.
You don’t even have to ship them, just make a web link that is out of stock and make them a legal product (eqv from local hardware store, or McMaster) for competition.

This would be a fantastic addition. Pretty much all robot maintenance ever is on those motor screws and trying to bend around a corner or three to get at them.

That, or make loctite legal.

Chris – Loctite is legal:

[INDENT]<R15> Parts may NOT be modified as follows:
(…)
b. Welding, soldering, brazing, gluing, or attaching in any way that is not provided within the VEX
Robotics Design System will NOT be allowed.
[INDENT]• Mechanical fasteners may be secured using Loctite or a similar thread-locking product.[/INDENT]
[INDENT][INDENT]o This may be used for securing hardware ONLY.[/INDENT][/INDENT][/INDENT]

I have had good results with using some Loctite 242 on the motor screws. As long as you use a medium strength Loctite and you don’t flood the piece with it you should be fine. Just be careful that you don’t allow the Loctite to come in contact with any of the plastic casing of the motor because Loctite makes plastic very brittle and the plastic will just flake away. Also make sure your motor bolts are in good condition, mainly the allen hole. If it is even a little bit stripped you will have quite the adventure trying to remove them.

Edit: I also find it really useful to have an allen wrench with the short end cut down to only about 1/4" this way it is easier to tighten motor bolts if you ever have an issue.

~DK

My biggest maintenance issue has always been with the motor screws. And whenever locktite is used, the allen wrench hole always strips out. Would love to see this come to Vex.

We discovered these on the parts list a year or two ago: http://www.vexrobotics.com/products/accessories/structure/screws-6-32.html

We do not use the black motor screws on competition robots.

Good to know, a star washer distributed by vex would also be tremendously useful.

I personally don’t think a star washer would be very good, the kep nuts don’t stay tight. We use the purple low strength loctite.

I do think screws like these in a #6 for motors might be the best solution:

http://www.vexrobotics.com/products/accessories/structure/locking-screws.html

Jon T

Star washer on the high strength motor screws with just a touch of tension are very secure. I’ve got a few robots that have about 5 hours of drive time on them and the motor screws are still good.

I have misgivings about using lock-tite on something that needs to get undone/done. In a penultimate design it should be fine.

Keps nuts on something that does not twist works well. So if you put three of them in a chassis corner and tighten them down they last. Only one in a chassis corner then they will come apart.

One of the hidden features of VEX is that if you have a good, solid design and use some reasonable build techniques it’s great. It will perform and last. Slap something together and it will sort of work, but it won’t last. Much like the real world :rolleyes: