Tips for soldering wires onto used motors

[njdriver04]

I have three runners I am getting going for the spring, I am having problems because the older motor contacts already have solder on them. Thoughts suggestions are appreciated.

[shodog]

being clean is key. get a 40w iron and remove all the old solder. Clean all the grease, dirt and old flux off with Isopropyl alcohol. pre tin the wire by dipping it in flux paste then put some solder to it. Then place the wire on the contact, heat the wire and then put the solder to it.

[njdriver04]

cool thanks

[bully]

If they are really gunked up i heat them with iron and quickly hit them with a wire brush,tape any areas you don't want to scratch like decals etc.. They come up like new,clean iron tip well and tin both as usual mate..

[shodog]

There is some braided wire called solder wick. When heated on solder It will remove it from the surface. At my work they are super picky when you solder something that they send you to solder classes and you have to certified to do any flight soldering.

[RC10th]

A good quality rosin core solder will also do the trick and is less messy than using flux paste. A high but quick heat is the best method, use a good quality 40+ watt iorn with a wide tip and always keep the tip clean.

[Peakey]

As above really more heat the better and flux is a must. The better you tin your wires the better finish you will get

[treystoys]

I realize this is an older thread, but figured I'd give my input.

First, as the other guys have said, a higher wattage iron along with steady hands will end in a better joint. The main thing you want to really worry about too much heat on is circuit boards and battery cells, but since this is a basic motor rewire we'll leave that info as is I use a vintage Ungar UTC 300 (made by weller) 60 watt iron with a mid sized 3/16 tip to get the heat where I want it. I also forgo all the cleaning items such as wire brush and solvents and just use fresh rosin core solder and a little heat to remove anything old and gritty. If your re-soldering a factory joint, the likely hood of it being contaminated is slim unless you know it has gotten grease or oil on it.

That being said, I always solder over a non flammable surface, if not available, a few layers of aluminum foil works for a temp area.

To remove the old joint and solder, I hold the motor so the working joint is on an angle to drip off away from the motor after its heated. Pre tin your tip, and wipe that away either on a damp sponge or damp paper towel folded into a bout a 2" square. Also use small amounts of solder to test the tips heat before attempting to solder or de-solder anything (that's going to keep unwanted heat off the joint and keep it from soaking up into the rest of the component) with a good 4-6"s of solder (I use the thinner stuff) unwound I'll apply solder to the tip and when it will melt the instant it touches the tip no sooner then its ready to work. Now back again to the motor, if de-soldering, and the motor is in a jig or held firmly in place (the handles of a small needle nose pliers work well here, cradle the motor between them and put a rubber band around the open end, trust me you don't want a motor with the endbell heated to 500 degrees to land in your lap! lol) Ok sorry, hold the heated tip firmly against the joint, within 2-4 second the solder should start melting. If you've angled the joint down, you can basically scrape the solder and wire off after its started melting. When its off, you can keep the motor in that position and dab some solder on the joint to pre tin the area, at the same time if it looks dirty then use the solder like a cleaner and hold heat at one end of the joint and let the solder wick to the other side and fall off the tab until you have a nice layer of shiny solder on the tab.

Your ready to add a new wire now. For handling the tinning of and soldering wires, a piece of silicone fuel tubing an inch or so long that has a slit down one side can be put over the wire as an insulator to allow you to hold the wire with your fingers without melting your finger prints off I usually set the solder spool so that the solder is extended facing me and pull it up and make it into an arc so its one less thing to handle. This leaves the wire in one hand and the iron in the other. I remove only the amount of wire insulation needed to solder that particular joint. No need to have uncovered wire exposed anywhere not needed. Anyhow with the wire stripped, I always twist the exposed wire end to keep it from fraying I hold the exposed wire to the top of the iron (hot air rises ) touch the solder to the side or top of the wire and let the solder soak into it. After the tinning process inspect your work and make sure the solder has soaked through entirely. If not re-tin using the step above. If you find you are unable to get the wire tined completely, it may be contaminated or old and handled too much, replace it with a new wire and try again.

Once tined through and through its time to make the connection. Some guys use a jig with small alligator clips to hold things in place, but I use my fingers and if needed the fuel tube to insulate a little. So holding the wire on the tinned motor tab, apply heat to the tinned wire with pressure enough to melt solder and push the joints together. Once melted its very important to keep the cooling joint perfectly still. A cold joint will look very dull and brittle and will very likely fail once current (heat) is flowing through. A good joint will "appear" solid and shinny, and will hold heat up too the melting point of the solder used.

I am new here, however I've been actively involved in rc for probably 30 years, most of those soldering I hope I wasn't too long, however I wanted to be as detailed as possible for the guys attempting to solder for the first time.

Thanks for reading!!

Trey