Motor cable melted - replacement?

[Boris Lämpel]

After changing the motherboard on my Gotway MSP I noticed the reason for its breakdown: melted phase wires caused a short circuit. So I need to replace the phase wires coming from the motor through the axle to the motherboard.

Did anyone of You have the same problem? I need to know which cable to take: I want to have the maximum thickness that fits the axle combined with good (but thin and heat resistant) insulation and a material that has a low resistance. Any suggestions?

[mrelwood]

 

1 hour ago, Boris Lämpel said:

Did anyone of You have the same problem?

I’ve done the same operation on an MSX. The key is to find the cable with the highest amp rating of the ones that have the same outer diameter than the original. The originals are Teflon coated cables, which is what you should use as well, so that should narrow your search. Depending on where you’re shopping, you might not even have too many Teflon wires to choose from.

[alcatraz]

Does the axle help with cooling?

Have people had wires melt inside the axle alone? I'd guess they would show signs externally first. But I'm not sure.

[mrelwood]

6 hours ago, alcatraz said:

Does the axle help with cooling?

Have people had wires melt inside the axle alone? I'd guess they would show signs externally first. But I'm not sure.

On my MSX the major issues were somewhere else, but it did have molten wire shields inside the axle as well. While the axle surely cools them down, it also makes the wires run very close to each other.

Back then Marty shared a tip about spreading the wires with those watchacallit tying straps, and it might’ve saved my cables from melting. They would’ve melted only a few meters later…  On my MSX the motor wires were 60cm long (25cm would’ve been enough), and the excess wires were all bunched up and tied together tightly. Unsurprisingly that’s where they shorted. GotWay did shorten the cables after that.

[alcatraz]

32 minutes ago, mrelwood said:

On my MSX the major issues were somewhere else, but it did have molten wire shields inside the axle as well. While the axle surely cools them down, it also makes the wires run very close to each other.

Back then Marty shared a tip about spreading the wires with those watchacallit tying straps, and it might’ve saved my cables from melting. They would’ve melted only a few meters later…  On my MSX the motor wires were 60cm long (25cm would’ve been enough), and the excess wires were all bunched up and tied together tightly. Unsurprisingly that’s where they shorted. GotWay did shorten the cables after that.

That's interesting. Do you mean that if you had used Marty's mod it would have saved you from that fall?

It surprises me that the axle section isn't as bad. What if it's something crazy like the motor produces a pressure that moves a little air?

I bought some glass fiber tubing (like what Begode uses, but not enough). Only problem is that if you cover up the whole wire you don't quite see the damage and you can't do the axle section. 

How much did you push the wheel when it happened? Were you on sand or doing crazy climbs? Pushing lots of amps, probably.

I feel like I want to clean my xt60 connectors now, expand the pins, and use more glass fiber tubing.

Edited June 14, 2023 by alcatraz

[mrelwood]

20 minutes ago, alcatraz said:

That's interesting. Do you mean that if you had used Marty's mod it would have saved you from that fall?

Probably, but:

20 minutes ago, alcatraz said:

How much did you push the wheel when it happened? Were you on sand or doing crazy climbs? Pushing lots of amps, probably.

Plenty. It was the steepest section I’ve ever tried to crawl up, and it was 100m (or 150m, not sure) long. And I weigh 105kg. I was maybe 10 meters from the top when the wheel failed. With separated wires it would’ve probably been 5 meters… 

20 minutes ago, alcatraz said:

It surprises me that the axle section isn't as bad. What if it's something crazy like the motor produces a pressure that moves a little air?

As the motor heats up, sure it will slowly blow a minute amount of air, but that hot air isn’t cooling anything.

 The axle is a large piece of steel that acts exactly like the thermal block on any other device.

 

20 minutes ago, alcatraz said:

I feel like I want to clean my xt60 connectors now, expand the pins, and use more glass fiber tubing.

My incident happened in about 2018, so even Begode has since improved their high amp behavior on their wheels. I wouldn’t worry, unless you love cheesecake and you’re going to crawl up long and stupidly steep inclines.

[alcatraz]

Cheesecake phaaaaa

[Boris Lämpel]

In my case it happened when I forced the wheel into really hard acceleration from a standstill.

But nothing melted. The cables are like 8 years old and experienced a lot of movement, especially with an axle replacement and lots of motor removing, but also on my offroad trips. The short circuit was because of broken insulation. The connection was closed through the metal of the axle. After further examination I was really surprised to find out that there were no traces of melted material. Only the insulation and some cores of the cable were broken.

 

Thanks a lot @mrelwood for Your shared experience. I already could organise the right cable, now I need patience until it arrives...