pic: burnt up TETRIX motor

[davidthefat]

We had the same problem, a burned out motor. I assume that it is a blown inductor. How many amps will blow out the inductor? And is there an acceptable fuse that will prevent this from happening, preferably one that fits in the battery's fuse clip?

Thanks,
David

[chapman1]

In order to resore our blown Tetrix motor for "development" use (working on them is an "illegal" mod), I took it apart as follows:

- remove from gearcase
- mark the orientation of the brush plate relative to the case
-file away the areas where the case is "lipped over" to hold the brush plate. I used a small triangular file.
- carefully tap the opposite end (the gear) on a hard surface to pop the brush plate up.
- do not pull up on the brush plate! This will damage the brushes. Instead, slide it sideways off the commutator.

Once I had it apart, I could see that the inductor was obviously smoked. I unsoldered it, and in its place, soldered a solid wire (don't worry, it will still work!)

To reassemble:

- create 2 loops using fine thread. Hook one loop around each of the brushes.
- with the loops, carefully pull the brushes far enough apart to clear the commutator.
- pinch the threads around the circumference in a way that will hold the brushes while you reinstall the brush plate on the shaft.
- when it's in place, snip each thread loop and pull one end to remove them.
- place the motor on its side and using a small hammer, gently "tab over" the housing adjacent to the notches you filed away to remove the brush plate.

If you are as lucky as me, the motor will run like new! Granted, it doesn't have the "inductor", but it seems to work just fine for testing and development. It pains me to have to spend $30 each time a motor blows!

[SuperBK]

What current should the inductor be rated for?

I see its legal to repair it as per <R93>
b) a burned out motor may be repaired by replacement of the burned-out inductor with an identical part

[colin340]

Originally Posted by SuperBK

What current should the inductor be rated for?

I see its legal to repair it as per <R93>
b) a burned out motor may be repaired by replacement of the burned-out inductor with an identical part

I believe that the very has been stated somewhere but no one can find a replacement part

[Al Skierkiewicz]

Brian,
The highest current device I have found thus far for this size package is 900ma. Unfortunately, those are non-stock at Mouser.

[SuperBK]

Thanks Al, what size package is it? (length, width)? Ours is locked away in our trailer since we got home Saturday night from Palmetto. We have a week and a half to get ready for our next regional.

[lonski]

Originally Posted by vincentkee

Does anyone have problems with the tabs of the motors frequently breaking off?

We have our minibot climb up a steel pole that doesn't have a top so it falls down. We don't always catch it and then the tabs of the motors keep breaking, rendering them useless unless we solder on replacements.

we have had troubles with the connectors and we soldered the wires to the connector and never had any more issues with them beraking. we just have an issue with a brand new motor that we bought just burnt out. we broke in the motor before we put preassure on the motor and then we climed the pole and the tird time and the motor just randomly stoped. the shaft spins nicely the motor didnt heat up or smoke. anyone know how to open the motor

[Jeffy]

Originally Posted by lonski

we have had troubles with the connectors and we soldered the wires to the connector and never had any more issues with them beraking. we just have an issue with a brand new motor that we bought just burnt out. we broke in the motor before we put preassure on the motor and then we climed the pole and the tird time and the motor just randomly stoped. the shaft spins nicely the motor didnt heat up or smoke. anyone know how to open the motor

Easiest way is to lightly tap on the end of the motor shaft without the back end of the motor supported. The back piece pops right off.

[Ninja_Bait]

Originally Posted by colin340

my electrical people said a fuse would take to long to blow as the resistor or inductor was gone in under 2 sec

15- and 10-amp fuses saved our motors more often than 20's did. Once we had a design that worked, we switched back to 20-amp fuses because we had more of them, but the lower amperage was helpful.