Soldering bullet connectors to motor wire

[joshuabardwell]

I have a Turnigy D3542/4 1450 kV motor that I wanted to shorten the leads on. I snipped off the leads and stripped back the insulation. From the size of hole on my stripper that I used, the wire is about 18-16 gauge. When I went to solder the bullet connectors on, I could not tin the wires at all. The reason, I think, is that there is such a mass of copper in the motor that it is sucking the heat away from the iron faster than the iron can put it in. Eventually, I got the connectors on by filling them with solder, then flowing it, then sticking the wire into the connector. But I know this is a bad joint and I don't like it.

My iron is rated at 60 watts, so I would think it would be plenty hot, but it's just not. What am I doing wrong?

In the future, would it maybe be better to shorten the leads on the ESC and leave the motor wires alone?

 

[RoyBro]

You should be able to tin any copper wire. 18-16 gauge isn't that heavy. So either your soldering iron isn't hot enough (in spite of its rating), or the tip needs to be cleaned. You could also try putting a little flux paste on the exposed wire to help flow the solder.

Hope this helps.

 

[makattack]

It could be that the wires inside/under the insulation is motor wire. Not bare copper wire. If that's the case, you'll have problems getting any solder to stick to them unless you strip them of the clear lacquer insulation around each strand.

I have a friend who discovered that with some motor wires he had in a cheap HK purchased motor, and had to apply tons of heat from his iron over a long time to burn off the insulation...

 

[Stradawhovious]

Assuming your methods and technique are sound, clean and re-tin the tip of your soldiering iron and try again. If it STILL doesn't work after that, hurl the iron as far as you can, into the deepest body of water you can find, and buy a new iron. (or try a new tip... but I'm from the "get a bigger hammer" school, and generally go for the path of least resistance)

 

[joshuabardwell]

It could be that the wires inside/under the insulation is motor wire. Not bare copper wire. If that's the case, you'll have problems getting any solder to stick to them unless you strip them of the clear lacquer insulation around each strand.

I am 99% sure This is the answer. The lacquer is a bronze color that made me think it was copper, but now that you mention it, I am pretty sure you're right. I've seen the same wire used for winding transformers, but it wasn't the same color so it threw me off.

This means that the bullet connectors have an even worse connection than I think, because they are only making electrical connectivity with the very tips of the wires.

Maybe I can burn off the lacquer with a butane torch?

BTW, the very ends of the leads had solder soaked into them from when the original connectors were installed, but I cut that off short. I guess they only removed the lacquer from the first inch or so at the factory.

 

[joshuabardwell]

Burning off the lacquer didn't really work. I mean, the lacquer burnt, but then the wires were coated with black soot that I had to scrape off, so I might as well just have scraped off the lacquer.

 

[William A]

Flux ?

 

[Balu]

Flux.

 

[joshuabardwell]

Flux ?

I have flux-core solder, so I don't have a separate flux pen, etc... Maybe I should get one.

 

[makattack]

I don't see what Flux will do until the insulation is all off. Any luck with scraping? I wonder if acetone might help. I use a 50/50 acetone/isopropyl alcohol mix to remove/clean Flux off parts after soldering.

 

[Tritium]

Scrub with Green Scotch-Brite pad (or 400 grit sand paper) after burning all the coating off you can.

Thurmond

 

[joshuabardwell]

Since people are asking, I'll give an update. I burned the enamel as much as I could with a butane torch, then scraped the residue and any remaining enamel with a hobby knife until I was sure I could see actual copper, not the bronze-colored enamel. Ultimately, I still couldn't get the solder to flow worth a darn. I filled the bullet connectors with solder and then pre-heated the wires as much as I could with the iron before flowing the solder in the connectors and sticking the wires in. I know, empirically, that it's a cold joint, but the motor spun up and ran just fine for the twenty total seconds of flight I got before I nose-dived the model into the ground and broke off the motor mount. Side note: tail heavy flying wings are un-controllable.

In the end, I am going to sub out the motor for something lighter. The forum post that I read that suggested this motor would be a perfect match for a 3S 2200 mAh batter seems to have been wrong. Or maybe their battery was a lot heavier than mine. My battery all-up weighs about 6 oz, and I need about 9 oz to get the CG even close to right. This time, I will side-step the whole issue by cutting the ESC leads short, not the motor leads, and that will be that.

 

[makattack]

I didn't realize you were putting that motor in a flying wing. A versa perhaps? If it's a pusher versa, you'll probably need to load up the nose with lots of ballast. My Blunt Nose Versa, with a 3300mAh battery still took about 50g of nose weight, and that's with FPV gear and two cameras mounted!

Sorry to hear you crashed, but the versa is so easy and fast to build, it shouldn't take long to get it back up in the air. With a 2200mAh battery, I need about 110g of nose weight to balance out (without FPV gear).

 

[joshuabardwell]

It's a Teksumo. I wanted to use the 2200 mAh batteries mostly because I already have four of them, so I needed a bigger motor to counterbalance it.