393 motor emergency


#1

Someone decided to cut the wires off of our 393 motors. As we don’t have the V5 motors and are already signed up for a competition in one week. We also have no proof of who it was. Any suggestions?

Thanks!


#2

You can get repair kits online, I think. Can someone link one?

That’s terrible. :frowning: Can’t believe someone would do that to you guys.


#3


Not sure if this is what you need, but a lot of (if not all) of their products are competition legal, I think. Someone please correct me if I’m wrong.

Edit: You aight be able to find some DIY solutions here, if you’re capable of doing so. https://vexforum.com/t/motor-pin-repair-kit/27286/1 I’m not really sure if all of these solutions are leegal, though.


#4

Where are you located?


#5

This isn’t not our problem. They (whoever cut the wire) cut the wire at the very end where it connects to the motor. Thanks though!


#6

Colorado :slight_smile:


#7

Try contacting your Regional Support Manager and see if they can seek you some 393s quickly or connect you with a team willing to do so.


#8

If that’s the case, you could try soldering the wires back together (which could be a bit tricky), or strip some wires and reconnect using electrical tape (?) unless the wire was cut super clean.
Permitted by <R16>:


#9

Strip some of the insulation off the wire, desolder what is left of it on the PCB, and resolder it to the PCB.


#10

@Rieger.samuel26 as @Wiredcat Robotics said the best way to fix wires is to solders them and secure with heat-shrink tubing. I’ve done this kind of motor repairs a lot and it isn’t that hard. If you know anyone experienced with soldering in your community - they should be able to easily repair your motors.

Alternatively, you could repair your motors yourself and even without doing any soldering using string to secure spliced wires and some electric tape instead of heat-shrink tubing. Soldering would still be preferred as it will give you stronger connection.

If you post pictures of the cut wires, so we could see how much wire is left to work with, we could give you some more detailed instructions.

One thing that you will absolutely need for this job is a good wire cutter / insulation stripper tool designed to work with 20 and 22 gauge wires, similar to this one:
wire-insulation-cutter.jpg
Since you may not have a lot of wire to work with it is absolutely critical that you could reliably strip the insulation without damaging copper wires. You may need to practice on some loose wires first.

You could buy such tool for under $10 online and it may cost you more at the local hardware store. If you go to a hardware store you may want to grab some small diameter heat-shrink tubing and electric tape, if you don’t have it already.


#11

apparently it was cut all the way at the base


#12

If you have any nearby teams that are V5, you can see if they possibly can loan 393 motors to you or possibly buy from a same/lower cost.
In last resort you can redistribute your motor configuration and go with a weaker subsystem temporarily. For example, if you have a flywheel and a lift, you can ask your partners what ways they can score, and then you can place a motor in the subsystem opposite of the way they score. If you have an efficient enough drivetrain you could possibly take 1-2 motors off to improve your subsystems and uphold your offense.


#13

That’s why I said what I said. Desolder whatever is left off of the PCB, then solder the remaining wire on to the PCB again.


#14

I agree that soldering new wire leads to PCB is the cleanest way to fix it but, unless you are experienced at doing this type of repairs, I would avoid touching 393’s PCB. For whatever reason, the negative copper trace peels off very easily off the PCB. I tried to reduce soldering iron temperature to the minimum, but it still tends to happen.

So, if there is enough wire, then splicing it would be easier in this particular situation.


#15

The real issue is that soldering on the circuit board is considered illegal.


#16

Your only option seems to solder the connection back together, it is not too hard with the right equipment but you wouldn’t need to get new gear or new motor components. Also, what type of person would do this??? This is VEX, it is not like there are millions of dollars at stake.


#17

Game manual <R16a> states that “Motors … may NOT be altered from their original state in ANY
way”, but we are not talking about altering them - we simply try to restore their original working condition.

The manual’s intent is, clearly, to prohibit the modifications that violate the spirit of the game and would give some teams unfair competitive advantage (such as removal or bypassing of the PTCs).

You could counter-argue that <R16c> explicitly allows repair of the “external wires” and doesn’t mention anything internal. To which I will say that its likely intent was to discourage young students from trying to do repairs for which they are not qualified (yet).

However, game manual is not the word of God - they couldn’t predict and document all conceivable exceptions to the cases that would arise in the future. Instead, one of the favorite catch-all phrases in the game manual and official Q&A is that “we cannot issue a blank ruling” and “it is up to inspectors to determine the legality of the specific case”. This acknowledges that the life is complex and human interpretation is required to augment the manual.

My interpretation here is that if team is in dire situation (through no fault of their own) then it is reasonable to perform motor repairs that do not violate the spirit of the game, even if you could argue that they violate the letter.

Yes, to stay fully legal they would need to either borrow motors from another team or order a new set. However, I find it ridiculous that anyone would think that (if they couldn’t find spares locally) then the only acceptable solution would be to force them to skip competitions for the next 6 weeks and spend $180 for the replacements. I believe, helping them to repair their motors is not only the right thing to do but will help students’ education by making them less afraid to look under the hood.

@lacsap, isn’t Massachusetts a “right to repair” state?

I think enshrining this right in the law gives people of Massachusetts huge competitive advantage in the decades to come.

I wish VEX put more efforts into shaking off the stigma that one should never touch anything inside the black box and actually encouraged students to dive deep into the inner-workings of their components. Making transparent cases for some of the parts would be extremely nice.


#18

To be clear - it is not just a matter of soldering a new set of wires, but assuring the ferrite core is also part of the wire assembly.

So, as I mentioned before, VEX does not sell a wire assembly, nor specifies all the parts, working to replace the assembly from the PCB is not something that would have passed inspection in the past.

Dig as much as much as you wish about Massachusetts right to repair… the end result is that the repairs need to pass inspection.

Also note that I have been an advocate of all legal repairs on Q&A as simple as possible. Working on the PCB for me crosses the line since you can not be sure what else was repaired “inside” the motor housing.

As always, feel free to ask on the Official Q&A.

My recommendation would be to notify the EP AND the RECF Regional Support Manager to know about this unusual circumstance.

End of the day, you have someone in your own organization that made a decision to destroy club equipment… sad day for the club.


#19

If you guys find out who did it you should buy V5/more 393’s and then charge then for the damaged motors and the replacement motors.


#20

@Rieger.samuel26 the best advice in your situation is to either get a replacement motors from another team or VEX, or have someone with soldering experience to repair them for you. However, as the last resort, below are the instructions on how to repair your motors without soldering, using only wire insulation stripper, scissors, thread, and a little bit of glue. And if you choose to do that, please, follow @lacsap advice and notify official at the competition you are going to attend.

I am sure they will not object since you are not gaining any unfair competitive advantage and may even be impressed by your perseverance.

393_motor_repair_1.jpg

This is an old motor I pulled from a discarded components bin, which has wire cut very close to the housing.

393_motor_repair_2.jpg

As you can see there isn’t much wire left to work with. I also pulled the gears out and note how one of the gears is badly worn. It would need to be replaced with a new gear, which is sold inside motor refurb kit.

393_motor_repair_3.jpg

The next step is to push wires on both sides into ferrite core so that it easier for you to transfer more of the wire to the motor side.

393_motor_repair_4.jpg

After that I put rubber seal back on the wire and used wire stripper tool (20-22 slot) to strip insulation on all ends. It was very tricky to do it on the motor side where wire length is limited, but you could practice on some spare wires first. Notice that I stripped more wire on the other side.

393_motor_repair_5.jpg

In the next step I twisted wires together. First I used non cutting end of the tool to twist insulated spans, then twisted copper conductors by hand. You, obviously need to be very careful not to apply too much force because you could break the wires.

This will be a good time to test if the motor is working. Also, if you know how to solder, this would be the time to solder the wires.

393_motor_repair_6.jpg

However, we are going to use string to secure the insulated portion of the wires. Make sure to do few loops, tie a knot, then few more loops, tie another knot … repeat 3-5 times.

393_motor_repair_7.jpg

The next step is to dab a little bit of super glue onto the insulated section of wires and the string. I prefer to use Gorilla brand for this type of plastics and the string, because Krazy brand tend to make plastics brittle. Avoid putting any glue onto the copper conductors. After that cut any excess string.

393_motor_repair_8.jpg

Test the motor again. If it works you could put little pieces of electric tape to cover conductors and turn the wires around (carefully).

You also need to wrap 15-20 loops of string around both wires and dab them with the glue to prevent wire from sliding out of the rubber sleeve.

After glue dries out and you tested the motor one more time, you are ready to replace the gears, and close the motor.

Good luck!