Buggy BAG Motors

Paul, would it help if we organized an informal check of motors at some of the regionals? I know my team isn’t using the BAG motor this year, but I want to check ours the next time I’m at our build space (if only to avoid issues if we try to use it in the future), and it sounds like it would be quick and easy to walk around the regional with a multimeter and check any BAG motors that are there.

We’re using a three and have some spares as well. I don’t think we have any problems. The 1:1 BAG on our shooter tops at 11000 RPM, but I figured that was from loading. I can’t check any till Lone Star, but I’ll be sure to check them there.

Anyone else have further problems? We have had 4 out of 5 fail.

Vex customer service has been great and we have more on the way.

I’m hoping we have just had bad luck and others are not having as many troubles as ours.

If people tell me they worked well for them during week one I’ll be much happier.

We’ve had the failures and have since swapped everything to 550’s which brings up another problem in that there are no piloting features for the 550’s on the versaplanetaries so it takes a great deal of effort and fiddling with alignment to get the planetaries to not bind.

The low prices are great but I have to say all of the problems encountered thus far are not leaving a great impression for anyone I have been in contact with.

I checked the three I had on had with the resistance check that Paul suggested, and all three of them work (Highest reading I could get was 80 ohms). Unable to check the 3 that may have been buggy, as they’re inside the bag itself.


We had 3/3 bags just fail over the course of the regional. Just ended up switching to RS Motors/AM motors.

Will be sending motors back to VEX sometime this week.



I would like to know more about all the problems you have been having with the VEXpro items. Can you please either PM me or e-mail me at paul_copioli <the at symbol> vexrobotics.com? We have received very little complaints about the VersaPlanetary this season so I am interested in what problems you are hearing about or witnessing.

The Versaplanetaries purposely do not have pilots because the motor shaft is supposed to be the pilot. If you follow the procedure in the user’s guide you should not get any binding between the motor and the gearbox. This motor mounting technique is very common with industrial servo motors and does not require a motor pilot.

With regards to the BAG motor issue, we are still working on root cause analysis, but the leading suspect is too much tension on the automatic motor winding machine. This can cause elevated stress in the copper wire. We have not finalized our findings yet, but we are working as quickly as possible on getting to the bottom of this problem. However, we have not received any motors back from customers yet and we are having a hard time reproducing the problem here. As soon as we get more failed units we can try to get to the bottom of this as quickly as possible.


I have to say I love the vex planetary gearboxes. Not having to press a gear on the motor using a force just lower than what is required to bend the shaft, turning the motor into trash is great. You do have to use an allen wrench in good shape to tighten the set screw though.

To stay on topic, we have not unbagged our bag motors yet.


Thanks for the quick reply to everyone and the updates on this issue, awesome customer service! I will try to locate the BAG motor we removed a few weeks ago due to a similar failure and ohm it out to see if it has the issue.

We also had a couple more BAG motors fail over the weekend, and replaced them with RS550s. There is now only one BAG on the machine, and we will swap it out during our unbagging window before our next district event (since we bought all of our BAGs in a couple of bulk purchases, the odds seem fairly high that it will fail eventually).

We 3D printed ABS spacers to help pilot the 550s into the VersaPlanetary motor plate since even when we followed the directions as closely as possible, we were unable to obtain a gearbox that didn’t bind, make clicking noises, or wobble when run. The issue (I think) is that mounting the motor concentric to the motor plate is difficult because the holes are too large to pilot the RS550’s M3 bolts. Leaving the motor bolts loose ensured that we ran without binding or clicking, but resulted in a vibrating motor.

Regardless, with the spacers, installing a 550 is a breeze and everything runs smooth as butter. The VersaPlanetaries are a fantastic gearbox once you get them together! There’s a reason 341 has 5 of them on our robot :slight_smile:

I realize there is nothing you guys can do about the BAG motors without some failed units, so I will make some time this week to round up our problematic ones and send them your way.

Agreed. We found a metric allen wrench that seems to fit better than the recommended standard allen wrench size. I forget the sizes now. We wound up rounding out a couple of set screws until we got the hang of it. If there was one improvement I would recommend to the VersaPlanetaries it would be to simply drop a few spare set screws in the bag of small parts.

BTW: We had 3 “bad” BAG motors that developed the issues described in this thread. I contacted Paul as requested and they are send out replacements right away. In the mean time they emailed me an overnight shipping label and I have shipped them back our 3 “bad” BAG motors for testing. Hopefully this will provide some insight into the problem. I can’t say enough good things about VexPro and the IFI guys customer service and how they are handling this issue. Thanks guys!

For all applications that use Allen keys, I personally suggest these:

They are only marginally more expensive than regular Allen keys, but they are awesome. I have yet to see one strip after using them for several years, even extremely small ball-point sizes like 5/64".

In addition, because they have a better contact profile against the hex sockets in the screws, they reduce the chances that you will accidentally strip a screw. I have also seen screws that were “stripped” being easily removed/tightened with these high-torque Allen keys.

Thanks for the heads up on the High-Torque Allen wrenches. I’ll add some to my next McMaster order and give them a try.

Chuck I’ve been using them all this year and they have been great. Buy the sizes you use commonly in bulk. They’re worth it.

Paul, our shooter failed twice in eliminations at FLR – not positive it was the BAG motors (which we had already checked for dead spots before installing them as replacements for the bad ones), but we’re going to pull them once we get the robot out of the bag at Buckeye, and I’ll send them your way. I’d love to hear what you find with those two in particular, as they tested good before use. (I’m not saying the failure was the motors. I can’t figure out what else it could possibly be, as our shooter worked great all through quals and nothing changed, but at the very least it will be another data point for you guys as you work through this issue).

Thanks for your prompt attention to the matter. Your customer service is great! (As are your mecanum wheels and versaplanetary gearboxes!)

We ran into the same issues. I PM’d Paul about it, and he says the runout on the RS-550 shaft is horrible, which would explain things. What does your magic spacer look like? Can you post it here or on Thingiverse?

So i have a strange motor problem, the BAG motor is connected to a spike relay - i turn the spike relay on and sometimes the motor docent spin. I have to give the motor a push to get it going.

the batteries are fresh and the motor has no load. i checked all connections and nothing seems to be loose.

See this thread:

We made a couple of different types of spacers to play around with, but all of them worked. The simplest one was simply a 3D printed “washer” that was a tight slip fit inside the motor plate and on the boss of the RS550. We also made a more complex part that additionally piloted the RS550/Motor Plate assembly to the gearbox itself, but this didn’t seem any better/worse.

Dustin will post the drawings as a white paper.

Runout in the RS550 shafts sounds like it is the main culprit, and would explain the vibration issues we see when the shaft alone provides piloting.

Hopefully today. Heh. On account of there’s this Lone Star Regional tomorrow and the 3D printer is at work and all…

I could draw it myself, but I don’t have the parts available to check fits. Speaking of, what did you guys print this on? A commercial printer, or a Reprap derivative?