Shortening or re-soldering motor wires

[Dan B.]

I’ve read that basically any motor should never have its wires shortened. For example, if you needed to solder a different size bullet on you can’t snip the existing bullets off, they must be de-soldered instead because it’s not possible to properly tin the shortened wires and the motor would run terribly or not at all. I can’t for the life of me understand why this would be the case. What am I missing? I know many people must have shortened, tinned, and soldered motor wires, right?
If anything, it seems to me that the shorter the motor wires the less the resistance would be and that could be beneficial.
Any advice from the pros would be greatly appreciated.

 

[Cheez]

I’m no pro, but I’ve shortened and reattached connectors and shortened direct connections several times without any obvious consequences. I don’t have an ohm meter but less resistance seems very likely.

 

[SrC]

Good points made.
From what I learned:
-Short leads yes, have least resistance. The general rule. Can this slight resistance affect a motor's Timing or EMF's back signalling? IDK.
-Excess wire length is sloppy, adds liability as well as unneeded weight.
- Many including myself have removed bullets and even hardwired directly. Mostly Sensored type motors that have 3 shunts for soldering directly. Ideal way with No connector.
- I feel the 3 phase wires should be of equal length, so what resistance that does exist, is identical for all 3 motor's phase wires. It is hard to remove ALL 100% of resistance. Neglible resistance occurs with the shortest wires possible even in a perfect world.
- I noticed that Raz had a wiring Tutorial a few years back and felt that if there are connectors that are Inline along the wires (not at the ESC) that the connectors shoud be staggered. He felt that Phase cross signalling could occur, if the connectors were placed side by side next to each other. All while the wires remain equal in length. But OE setups don't adhere to this rule. Connectors always sit next to each other.
- Reworking/Solder Tinning is necessary for large guage wires. 12g and larger IMHO. Most motors OE wires are 12g+. It can be done well enough if your skills allow.
-Keep wire gauge the same throughout the circuits length. Larger gage is always best if possible.
- I use acid free Flux paste with a large blunt tip and 750-800F solder temps for fast "Shiny" solder joints. Dull looking "Cold "joints are the ones that would fail, all while having more resistance.

 

[Fishtank]

I’m no pro, but I’ve shortened and reattached connectors and shortened direct connections several times without any obvious consequences. I don’t have an ohm meter but less resistance seems very likely.

I’ve shortened many motor wires in my day never a problem!

 

[#ARRMArcfanboy4life]

unneeded weight.

Last time I checked, a small amount of added weight on an rc car (to a point) isn't a problem.

 

[Dan B.]

I noticed that Raz had a wiring Tutorial a few years back and felt that if there are connectrs that are Inline along the wires (not at the ESC) that the connectors shoud be staggered. He felt that cross signalling could occur, if the connectors were placed side by side next each other. All while the wires remain equal in length.

A good theoretical hypothesis. Interesting to note though that motor manufacturers do not stagger the length of the motor wires, even when they’re short and must obviously be lengthened and outfitted with the bullets of your choice. I.e, TP motors. I just got a new TP 5660 and the pre-tinned leads are only about 3 or 4 inches long, but equal in length. I could perhaps see the argument in sensored motors…. Food for thought.

 

[SrC]

There are many ways to wire up a rig. Forr the sake of efficiency, even a gram not needed in theory, should not be there. Longish wires that can flop around are not best. Might be easeir to work on the rig perhaps. But Grams add up. And longish wires propped up can even create a higher center of gravity. Is that needed? No.
Track rigs are always setup with shortest length wiring as possible. There are may ways to do this. And will work fine for most.
Just that there is the one most efficent way if guided by Electrical Fundamental Rules.
Pick your poison

 

[Diem Turner]

You can shorten the wires on Castle motors without issue as they have a bridge connector between the windings and the external wires which are just normal 8AWG or 10AWG stranded copper wires. TP motors are a different story entirely. The wires that come out of the back of the can are the windings themselves which means that each individual strand is insulated. If you chop the pre-tinned tips off those wires you won't be able to tin the wires again until you remove all of the insulation from each of the strands which is a bit of a chore. Just something to keep in mind.

 

[SrC]

Last time I checked, a small amount of added weight on an rc car (to a point) isn't a problem.

Agree and you will never notice the difference. But there is absolutely a gram increase. I notice many go to CF to save weight/few grams, yet their wires are all too long. Doesn't make sense to me. I take the approach of minimal weight/wire length where possible . Just a Habit I always followed. From my track days. Build kits from scratch. Watching how the Pros do it. For bashing, many don't see the need.
But like this Thread asks the question.... Yes there is a proper way. IMHO.

You can shorten the wires on Castle motors without issue as they have a bridge connector between the windings and the external wires which are just normal 8AWG or 10AWG stranded copper wires. TP motors are a different story entirely. The wires that come out of the back of the can are the windings themselves which means that each individual strand is insulated. If you chop the pre-tinned tips off those wires you won't be able to tin the wires again until you remove all of the insulation from each of the strands which is a bit of a chore. Just something to keep in mind.

Excellent point.

 

[Dan B.]

You can shorten the wires on Castle motors without issue as they have a bridge connector between the windings and the external wires which are just normal 8AWG or 10AWG stranded copper wires. TP motors are a different story entirely. The wires that come out of the back of the can are the windings themselves which means that each individual strand is insulated. If you chop the pre-tinned tips off those wires you won't be able to tin the wires again until you remove all of the insulation from each of the strands which is a bit of a chore. Just something to keep in mind.

Well, that’s exactly the answer I was looking for. I didn’t know that’s how TP’s were done. I’ll not shorten them, lol. Fantastic info, thanks!

 

[SrC]

That was the answer.

 

[slick2500]

You can shorten the wires on Castle motors without issue as they have a bridge connector between the windings and the external wires which are just normal 8AWG or 10AWG stranded copper wires. TP motors are a different story entirely. The wires that come out of the back of the can are the windings themselves which means that each individual strand is insulated. If you chop the pre-tinned tips off those wires you won't be able to tin the wires again until you remove all of the insulation from each of the strands which is a bit of a chore. Just something to keep in mind.

I think I recall some of the cheap eBay motors go this route as well.

 

[LibertyMKiii]

Well, that’s exactly the answer I was looking for. I didn’t know that’s how TP’s were done. I’ll not shorten them, lol. Fantastic info, thanks!

The copper has enamel on it that insulates the wire so it does not short into other windings inside the motor.
This enamel can be scraped off or chemically removed. I have a YT video on chemically removing the enamel. It is messy and toxic at best.
If you don't need to shorten them I wouldn't.

 

[PeighDay]

The copper has enamel on it that insulates the wire so it does not short into other windings inside the motor.
This enamel can be scraped off or chemically removed. I have a YT video on chemically removing the enamel. It is messy and toxic at best.
If you don't need to shorten them I wouldn't.

Well I was a complete idiot and shortened my TP Motor wires. Though I did not cut past the part that was exposed by shrink wrap. Maybe 5mm. Do you think I will still be okay?

 

[LibertyMKiii]

Well I was a complete idiot and shortened my TP Motor wires. Though I did not cut past the part that was exposed by shrink wrap. Maybe 5mm. Do you think I will still be okay?

Probably will have to strip enamel off.
You can take a razor blade and scrape a single wire. Or try to "tin" the wire. You will know quickly if it has an enamel coating on it.

 

[PeighDay]

Probably will have to strip enamel off.
You can take a razor blade and scrape a single wire. Or try to "tin" the wire. You will know quickly if it has an enamel coating on it.

Appreciate your response. I was able to resolder new bullet connectors. Bench tested the motor and it still works.

Do you think by shortening the wires it caused damage to the motor and decrease the longevity / stability of it? Or at this point consider it a loss and lesson learned?

 

[Dan B.]

Appreciate your response. I was able to resolder new bullet connectors. Bench tested the motor and it still works.

Do you think by shortening the wires it caused damage to the motor and decrease the longevity / stability of it? Or at this point consider it a loss and lesson learned?

If you got good solder joints it should be fine. When you said shrink wrap I’m assuming you meant the insulation on the motor cables? If you didn’t cut past that you’ll be just fine. Or did you mean the clear inner wrap under the insulation? That could possibly be an issue if they were coated strands. If you just shortened 5mm or so because the tinned portion was too long for your connectors you didn’t do anything wrong at all.

 

[PeighDay]

If you got good solder joints it should be fine. When you said shrink wrap I’m assuming you meant the insulation on the motor cables? If you didn’t cut past that you’ll be just fine. Or did you mean the clear inner wrap under the insulation? That could possibly be an issue if they were coated strands. If you just shortened 5mm or so because the tinned portion was too long for your connectors you didn’t do anything wrong at all.

I didn’t cut past the black wire insulation. I removed the red, green, and yellow part of the shrink wrap / insulation. Under it looked like a large amount of tinned wired.

Appreciate you help.