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DKNguyen
05-28-2009, 06:49 AM
I'm curious as to why it is said you should not shorten the motor wires (I am talking about the motor itself, not the ESC). I wanted to replace the soldered connectors with crimps onto fresh wire which means lobbing off the soldered end of the wire.

I've seen various reasons, and some of them don't seem to make sense:
1. Isolate the heat between the motor and ESC
This one seems to be the most valid one I've come across so far but nothing definitive.
2. Outrunner leads need to be kept the same resistance/length for the sensorless BEMF measurement of the ESC
Sure, but then why can't I just shorten them all by the exact same amount? People have extended the wires between ESC and motor which shouild cause the same problem.
3. The rest of the power wires on the motor are covered in enamel
Unless exotic litz wire is being used for the motor power leads (which it's not), I don't see why the power wires would be covered. It's already covered with insulation, why bother covering the individual strands again (unless it's litz wire). Yes, the windings are enamel covered wire, but the windings are not the power wires. Saying that the power wires are just extensions of the winding wire also doesn't make sense since you're basically saying that someone took stripped off a huge chunk of the power wires, separated the strands, and then used them to wind the motor.
4. People's motor wires are just so oxidized they need to clean them before solder will stick.
They ask why, and people come along telling them reason 3, which I think is false.

It's also completely possible that no one has ever talked about shortening the motor leads because they are already so short- they are only talking about shortening the motor wires on the ESC and I am getting the two confused.

Glacier Girl
05-28-2009, 11:43 AM
Well, as you said folks do lengthen the esc leads to the motor rather then running longer pack leads, so that would tend to toss out the window any reasoning of changing the motor lead lengths.

Other then keeping the leads the same length, I can't see any reason why you couldn't shorten them.

Other then the heat factor from the motor going towards the esc, I can't see a problem.

Honestly on some of the Strykers I've built,to keep wiring runs short, I unsoldered the leads off the esc and soldered the motor leads direct to the esc. And I've cut many motor leads to install new ends, as long as the leads were kept the same length, I've never had a problem.

As long as you get a good solder connection (where folks can get into trouble) you'd be doing just like the factory did mating a lead to the wiring termination points.

Long or short a motor and esc don't care. Just keeping all three leads the same length is the important part.

pd1
05-28-2009, 12:38 PM
Some motors use the winding wire for the lead outs. After winding they just let the left the wires long .The enamel coated wires just have an insulating sleeve over them.

If you try to shorten the wire, you have to clean the wire underneath real well or the solder won't stick.

Some motors have a short piece of stranded wire already attached to the winding wire. If you cut the wire too short you can run into the solder joint of the two wires.

A lot of people get the solder joint too hot when they solder.
When you solder your new connectors onto the shortened wire, you can loosen the factory connection on the other end.


Now knowing this you can make your own decision whether or not to shorten the motor wires.

ron_van_sommeren
05-28-2009, 02:57 PM
Only reason is that it may be difficult for the average modeller to extend them again. (de-insulating, soldering).

1- One would write "cool motor and controller", not "do not shorten motorwires".
2- Lots of wire in the coils, compared to lead length. And we are talking speed of light here. Difference in length won't have any effect.

DKNguyen
05-28-2009, 05:25 PM
Some motors use the winding wire for the lead outs. After winding they just let the left the wires long .The enamel coated wires just have an insulating sleeve over them.

This was the main thing I was concerned about- crimping onto the enamel of the wires. But how would you even pull this off at the factory? Wouldn't you have to wind the motor first, leave a bunch of long lengths, twist them all together and then dip them in insulation (or heatshrink or otherwise cover them)?

Only reason is that it may be difficult for the average modeller to extend them again. (de-insulating, soldering).
2- Lots of wire in the coils, compared to lead length. And we are talking speed of light here. Difference in length won't have any effect.

I was referring to keeping the wire resistances the same between the phases. Personally, I don't see how it would make that big a difference. A person might get 1cm difference between the wores at most on the thick, low resistance 16-12 AWG power leads leads, while there is much more thinner, higher resistance wire in the coils. The coils would be prone to larger differences in length, and the higher resistance of the thinner wire would make an even larger difference in resistance.

pd1
05-28-2009, 09:16 PM
This was the main thing I was concerned about- crimping onto the enamel of the wires. But how would you even pull this off at the factory? Wouldn't you have to wind the motor first, leave a bunch of long lengths, twist them all together and then dip them in insulation (or heatshrink or otherwise cover them)?



I was referring to keeping the wire resistances the same between the phases. Personally, I don't see how it would make that big a difference. A person might get 1cm difference between the wores at most on the thick, low resistance 16-12 AWG power leads leads, while there is much more thinner, higher resistance wire in the coils. The coils would be prone to larger differences in length, and the higher resistance of the thinner wire would make an even larger difference in resistance.

That's it exactly.

Sometimes to get additional copper per wind they also use more than one strand and that can make the job more complicated.

The wire is pre coated with the enamel insulation, it must be scraped off to get a good connection.
The enamel is not added afterwards.

It's not impossible to lengthen or shorten the wires. It's just the average person without soldering skill is not likely to get a consistent good connection.

When I wind my motors, I clean the end of the winding wire and slip on insulation and solder the connectors on. I'm starting with all clean components.
If you take a bought motor, the outer insulation might be glued on, that can complicate things too.

Paul

DKNguyen
05-29-2009, 12:11 AM
So do people who DIY motors also do the same thing? Run the coil wire longer tha needed and then twist it all together and cover it? Or do they just solder regular wires on?

I guess I'll just solder the motor connectors on then and crimp everything else.

Moxus
05-29-2009, 12:26 AM
it wont have any effect.
i have rewound my hacker b40 a couple of times now, and i havent even given a thought to the length of the wires. i do also have extended the wires between esc and motor.
and the motor runs like clockwork.
as ron says, the electrons run through the wire with a speed thats just infinity for any practical measures, so it doesnt matter.
the only problem i can se with VERY long wire extensions is capacitance between the leads, but they have to be really long for that to have any measurable effect.
shortening leads only makes parasitic capacitance less, so it cant be bad for any reason as far as i can see.

ron_van_sommeren
05-29-2009, 03:32 PM
So do people who DIY motors also do the same thing? Run the coil wire longer tha needed and then twist it all together and cover it? Or do they just solder regular wires on? ...Remove insulation before connecting. To remove insulation from litze-wire, heat it on (real) Aspirin with soldering iron. Acrid fumes.
Crimping AND soldering is a bad idea, solder flows under pressure.

... the electrons run through the wire with a speed thats just infinity ...Electrons drift at about 0.3m/s (them is lazy buggers ;)), the information travels at speed of light.

Prettig weekend ;) Ron

ron_van_sommeren
05-29-2009, 03:36 PM
In short, there are no electrical or magnetic reasons against shortening wires.

DKNguyen
05-29-2009, 07:25 PM
Thanks everyone. I'll probably eventually try crimping on at least one of the 6 22xx outrunners I have. Definately try to crimp to the 40xx outrunner until I know I can get it to work with the a 22xx. Depends on whether I feel like stripping the enamel or not, until then I guess I can crimp everything else and solder the motors.

All strands have to come into contact with the acid in the aspirin right? That's not a problem because the aspirin should melt into a liquid? It sounds like an acid-dip to remove the enamel without getting the strands covered in solder. Sounds like you could melt a couple aspirins in an itty bitty tube over a stove and dunk the wire in if you really wanted to.

ron_van_sommeren
05-29-2009, 11:29 PM
Aspirin does not melt, I think (never used it, never built a motor) maybe only very local. It's the acid that does the trick. That's why you you to use real acetylsalicylacid based pain killer.

I don't know what crimping does with the insulation. How much insation will it remove? Enough? You can remove insulation with a sharp knife, by heating (not all types) or grinding/sanding. Some other insulation removal tips somewhere in this thread, use 'thread tools' to search for 'insulation' within thread:
http://www.rcgroups.com/forums/showthread.php?t=240993

Prettig weekend ;) Ron

DKNguyen
05-30-2009, 01:14 AM
I'm just wondering how the aspirin's acid touches the enamel (fumes or or liquid) because it seems to me that if it stayed solid it'd be a pain to make sure all the strands touch the aspirin- but if that were the case we wouldn't need to heat it. Google says aspirin melts at 135C and is made by some kind of melting and recrystalization so it seems that it does melt (though the entire tablet probably doesn't liquify at once- that'd be messy).

Crimping just deforms the metal contact to hug tightly around the wire. It won't remove any insulative coating (thought it may crack it).