Buggy BAG Motors

Hello Everyone,

We’re running one of our BAG motors at about 80% power into a 1:1 VEX VersaPlanetary.

Earlier today, it appeared that we had a BAG motor give out on us. We can’t tell if it’s a loose connection in the motor’s internals, or running the system with 1:1 wasn’t the wisest idea (with 2, 3-7/8 blue banebot wheels).

Anyone experience any sort of performance issue with a similar setup? We’re wondering if we need to perhaps reconsider our setup or perhaps it was a one-time occurrence.

  • Sunny G.

We had one get a bit flaky on us. Low torque, and if it stopped in a certain place it wouldn’t start again, but if it ran continuously it would keep on running. Took it apart (very nicely made motor inside) and it seemed like the brushes may have been hanging up a little bit, took them out, put them back in, slid them back and forth a little bit, and it seems fine.

BAGs are giving out on us too. In a 30:1 VersaPlanetary gearbox. We found that we could change rpms by moving around the leads. The motor would stop running for a short time then turn on again. We’re switching to an RS550.

We still haven’t had issues with either our practice shooter or our real shooter but 2587 did have an issue at the end of week 6. So I’m not sure what the difference is. We also use ours to collect so we stall it pretty regularly when testing things and they have all been fine so far.

We had an issue with a couple. We found that the coating on two of the wires going to the commutators wasn’t stripped off before they were soldered together. We stripped off the coating and re-soldered the wires to the commutators and all was well.

Hope this helps

We didn’t think about making a deal of it as we didn’t find anyone else with the issue

We had the exact same symptoms, except in the 1:1 configuration. The max rpm would sometimes be different, and we tried adjusting victors, when finally the motor just wouldn’t move when we applied power. Looks like we’re packing some RS 545’s before the team leaves for Palmetto tomorrow.

I’ll see what I find when i take one apart. Has anyone else been experiencing similar symptoms?

987 has had similar issues to what you are all describing on 3 of our BAG motors. VEX support has been extremely helpful via phone and email support and we are sending these back. Agree with sanddrag that the internals are high quality. We had the issues when attached to planetary gearboxes and under no-load situations.

We haven’t had any particular problems we weren’t able to solve. As well as what’s stated above, make sure that the set screw clamping the gearbox and motor is tight (and hopefully still there!). Tightening (or replacing) them has solved our issues.

Wow, I thought we were the only ones. We have been having the same issues with the BAG motor on our intake. Just changes rpm at will and it seems like moving the wires going into the motor have an effect on it as well.

We also have had some quirky bag motors. I’m not too sure on the specifics, but some of the issues seemed to be due in part to unsupported motor leads being pulled away from the case. We added a simple relief loop to the wiring and that seems to have done the trick.

Otherwise, BAG’s are pretty awesome.

We’ve been experience the following

  • They run with a variance of RPM when they do run.
  • Sometimes after running once they don’t turn back on. We go and spin the wheel lightly and it kicks on. (probably the brushes hanging up)
  • We’ve had this issue with about 6 of them.

Obviously the risk of this happening is high and we don’t want it happening during our matches so we have switched them out to the RS550.

Glad we weren’t the only ones having issues.

All,

This has been brought to our attention, but we have taken apart several motors here in our inventory and have not found any of the problems you are describing. The best way we can help solve this issue is for you to work with our customer service department to send us your bad motors so we can investigate. We will send you out replacement motors immediately as long as you agree to send back your bad motors within one week.

Moving the wires to change RPMs, based on the construction method of this motor is highly unlikely to me so there must be something else. Please know that the construction method of the BAG motor internals is exactly the same as the CIM motor with smaller parts. The leads are mechanically isolated from the electrical connection to the brushes.

The most likely scenario is that the brushes are hanging up on the commutators, but we can only solve it if we get some motors back. We have plenty in stock and can ship you replacements same day.

EDIT: UPDATE - We are pulling all of the BAG motors from inventory and 100% inspecting for the lost commutator issue. I will send updates as we figure out the % of motors with this issue.

Paul

I believe this is the issue. In both cases that I can recall with our BAG motors, the motor was able to spin again once we rotated the shaft a small amount by hand.

I will find our bad BAGs and send them back. Thanks!

We had similar issues with 2 motors.

We took one apart and didn’t see anything obvious, but it was late so we put a Mini CIM in its place (they’re super easy to mount to the Versaplanetaries) and were happier with performance anyway.

So here is an update: We have a few of the bad motors back from customers and they display the same symptom. I will try to explain briefly.

There are 7 commutators on the BAG motor and two brushes. For those not familiar with how a DC motor works, the commutators are the things that spin with the rotor (shaft) and contact the brushes to generate the magnetic field.

In the bad BAG motors, there is an open connection between the two wires that make up the winding. This results in one set of 3 commutators disconnected from a set of 4 commutators. When one brush is contacting only within the set of 3 and the other brush is contacting only within the set of 4 the motor will receive no current and not spin. This symptom will only show if the motor stops at a spot described above.

We are inspecting all of our BAG motors in inventory to find any motors with this condition. We have inspected about 500 so far and have not found any bad motors.

What we don’t know is if this is a condition caused by use or a problem right out of the box. Our theory is that the problem is right out of the box so our inspections should eliminate this issue.

You can inspect your own motors by using a ohm meter on the two leads and spinning the motor slowly. If the resistance goes into the k Ohm or M Ohm range, then you have the problem.

We will replace all motors with this condition if you contact our customer support at support@vexrobotics.com.

I’m seriously impressed by the speed of the response from the people at VEX!

Fingers crossed ours are working perfectly so far!

  • Bochek

For both of our problematic motors, we ran for several hours before the issue appeared. Once it appeared, we observed a ~1 in 5 chance that the motor would not start from a given stopped position. The motors were assembled and disassembled from their respective mechanisms/transmissions several times as well before the problem arose, so it is possible that some combination of operation and handling contributed to the issue.

We’ve had two go bad more or less immediately after assembling them to a Versa and running them lightly. Another has been in use with no issues.

Nice to see the quick replies.

Our issues have also been with motors that seen extensive use for a few hours/testing sessions, and then they just conk out.

Oh well, nothing to do until after our week 1.

  • Sunny G.

We believe this is isolated to a specific date code. we are still investigating, but it will be very helpful to let us know your date code. The code is
“YWWD” - Year, Week, Day all numbers. The last two letters are the actual factory. All of our motors are made in the same factory so that part of the date code is not relevant.

If you can e-mail me paul_copioli [the at symbol] vexrobotics [dot] com your date codes of bad motors, then that may help expedite the process.

Thanks,
Paul