Motor Protection?

I have been teaching a class of 15 students (first-time Vex users), and many of them like to use motors without the clutch, even though I’ve warned them time and time again against it. We haven’t had any ruined motors (yet), but in a way, I wouldn’t mind if one did, so they could see the consequences of this very bad habit.

My son (who is the lab assistant) suggested gluing clutch posts into all of the motors so that they would be forced to attach a clutch. This would also have the added benefit of not losing clutch posts as easily.

Can you see any drawbacks to doing this? Modest amounts of glue would be used to avoid crudding up the motor. Also what sort of glue would you suggest? Some possibilities:

  1. Superglue – not as permanent as one might think, as it is acetone-soluble (nail polish remover).
  2. Rubber cement – if used conservatively, you could yank out the clutch post again if desired.

I’ve made similar observations, and to date have not had any motors be damaged (with or without clutches).

I can recommend hot-melt glue for this. I haven’t used it for clutch posts, but I have used it on other gears/shafts to reduce play. It can be a little messy (stringy) to work with, but it will hold the posts firmly. You can pull the posts out using pliers, and pick out the remaining glue if you later decide you want to reverse the operation.


  • Dean

If you wish to keep the clutches in permanently I would coat the holes with epoxy since it sticks to metal, but I would not use hot-melt glue unless you rough-up the clutch posts first, because hot-melt glue does not stick to metal.

I’ve used hot glue to hold metal screws and nuts in on my bot before and it worked fine. There was a big discussion on this same topic here.

NOTE: read the whole discussion in that link on hot glue vs. other stuff. We concluded that Loctite/locking nuts work better.

I work with Indiana Robotics Educators, and we have demo robots that are used multiple times a week, and they do not have clutches. Those robots have been used for nearly 3 years now. We have had one motor failure, and I don’t think it was really due to the lack of a clutch. I could foresee a problem if a clutchless motor is used to lift a very heavy mechanism, but I am yet to burn up a motor due to the lacking of a clutch.

I would like to understand how the clutch actually protect the motor. The manual says that it momentarily disconnects the motor shaft from the shaft on the other side of the clutch. However, I tried testing the clutch to see how that works, and it didn’t seem to ever engage (ie, allow slippage). I had one shaft on the input side of the clutch and one on the output side and torqued them in opposite directions with two wrenches, expecting that the clutch would engage and the two shafts would move in opposite directions (I was hoping to shift the rotational orientation of the input and output shafts so I could use that to-realign where the neutral position on the servo motor was). However, with pretty significant torquing (far more than I’m sure the motors generate), the cluch never slipped. So I’d be interested to hear if someone thought that really was the way to engage the clutch.

How can you tell if your clutch has started to slip? Does it make a sound? I’ve had my motors drive things to where they get blocked by something else, and I hear a mechanical clicking sound. I had assumed that was the clutch, but now I wonder if that is something inside the motor since I am doubting if the clutches can actaully slip.

Try the Threads Motor Clutches and Answered: motor clutchs.

Try a Search for “clutches”, to find other Threads on this subject.