Thursday, December 15, 2011

How to Re-wire a Potted Motor, Part 4: How to Terminate Your Wires

If you are able to solder as shown in Part 3, congratulations! That’s the most difficult part to learn. These next few things are much simpler in comparison.

Once we finally replace our old motor leads with new wiring, we’ll need to connect the ends of that new wiring to the “3-Pin Terminal Body,” which is this thing:

When we detach it later, you’ll see that inside are three threaded brass studs:

The wires need to connect to these studs. We’ll eventually connect them by either a) crimping pre-bought ring terminals onto them, or b) creating ring connections on the ends of the wires ourselves. I’m going to show you both methods so you can decide which you prefer.

Ring Terminal Method #1: Crimping

What you’ll need:

For crimping, you’ll need a wire crimping tool or one of the first two wire strippers we looked at in Part 1. While I referred to the Gardner-Bender tool as a piece of crap, it does have a useful crimping section on it. You’ll also need to buy some ring terminals, also called ring connectors. They come in two varieties, “insulated” and “non-insulated”:

Left: Insulated. Right: Non-insulated.
Get the non-insulated ones on the right. The insulated ones take up a too much space when connected to the terminal body, especially if you’ve got a cabinet-wired machine, which necessitates a snake’s nest of six different wires going into the terminal body. And we're going to create our own insulation later with heat-shrink tubing, so no worries.

Ring terminals also come in different sizes depending on the wire gauge. Since we’re using 18-gauge wiring, look for the ones that have “18” listed in their size. They may be labeled “22-18” which simply means they’ll fit wire gauges 22 to 18.

Lastly, ring terminals are sold with holes made for different stud sizes. The stud is the little brass screw that they’ll hook onto inside the terminal body. We want stud size #8.

So what you need are “18-gauge non-insulated #8 ring terminals.”

They cost pennies each and your local hardware store, electrical supply store or automotive parts store should have them. Buy at least a dozen to practice on; once crimped, they are not reusable. Here’s a link for a 20-pack on Amazon in case you can’t find any.

How to crimp a connector onto a wire:

To crimp a ring connector on requires some force and a good grip. Even if your grip is not good, you may still be able to do it; the trick is to use a tool that provides good leverage, as seen a little further down in the "No/Yes" photos. The only way to tell is to try.

On a wire scrap, strip off about 1/4" of insulation. There’s no need to braid it.

Gently place the ring connector into your wire crimper as shown below. Be careful not to squeeze it yet, just place it in there firmly enough to hold in place. Note that I’ve placed it in the section clearly labeled “22-18,” which is appropriate for crimping onto the 18-gauge wiring that we’re using.

Also note that I’ve placed the ring terminal into the crimpers towards the top of the tubular part, not the bottom, so there’s a little of the tube sticking out beneath the crimpers.

Now slide the exposed wiring through the tube in the ring connector, as seen in the photo, until the end of the wiring just peeks out:

Hold the wire crimpers as far down on the handle as you can go, for increased leverage.

You’ll need to use your other hand to hold the wire and the crimper, from underneath, so that the wiring doesn’t slide up or down while you’re crimping it. (That’s why we left some of the tube sticking out of the bottom.) Make sure you don’t pinch your fingers.

Now, squeeze the bejeezus out of the handles, and this should happen:

After you’ve firmly squeezed as hard as you can, the tubular part of the ring terminal should now be squashed-looking and biting into the copper wiring strands. The results should look like this:

Does it? Good. But we’re not done crimping yet, we’ve only done the top part. Now slide the crimpers down a little bit on the tube, to crimp the bottom part.

Squeeze again, and you’ll get this:

Here’s a before-and-after, so you can see how much we have crushed that tube. It’s important to get it pretty flat, not only to make a good connection with the stranded wires, but to prevent “overcrowding” once we eventually connect it to the 3-pin terminal body.

Left: Pre-crushed. Right: Crushed.
To be sure you’ve made a good crimp, try pulling the wire out of the connector.

If it doesn’t respond to your tugging, well done.

If it does come out, you need to squeeze harder next time; and if you’re not able to get it any tighter, this method will not work for you. Fortunately, there’s a second way to make a ring at the end of a wire.

Method #2: Self-Made, Soldered Rings

I learned how to do this by reading Elizabeth’s blog, and she in turn figured this out by reading Elle Dubya’s blog.

Start off by stripping about 1.5 inches of insulation off the end of a wire. (If you’re using the Katapult tool, you may need to strip off 3/4-inch first, then slide the tool down and strip off another 3/4-inch.) Braid the strands up.

Elizabeth and Elle used pencil tips to wind the wiring around, but believe it or not I don’t own any conventional pencils (sign of the times.) But luckily I discovered a standard spool pin is about the same size as the brass stud the ring will need to fit onto.

So, take a standard spool pin. (For practice’s sake you can even use the one sticking out of the top of your sewing machine, though that will not work once we get the motor in place.)

Wrap the wiring around it, keeping it fairly tight, to make a ring. Be sure to leave room on the “tail” to wrap that around the wiring in a short braid, closing the loop and adding some mechanical strength.

Then slide the wiring off of the spool pin. It ought to look like this:

Now, using the soldering skills you’ve hopefully practiced since the last entry, solder it up, making the whole thing silver.

Remember not to use glops of solder, but to instead let it flow into the wiring once it’s properly hot. If you make it too gloppy it won’t fit on the stud. Here are both bad and good examples:

Left: Too gloppy. Right: Could use a bit more solder, but pretty good.
After it cools, test the size of the newly-soldered ring by sliding it on the spool pin. It should slide up and down smoothly, with just a hint of friction. It mustn't be so big so that it doesn’t touch the spool pin at all, or it may not connect with the terminal stud.

If your ring is too big, you need to wrap it tighter the next time you make the loop; if it’s too small, you may have added too much solder and done a gloppy job. Practice this until you’ve got it right.

If it slides up and down the spool pin smoothly, with just a hint of friction, you can be sure it will fit cleanly on the brass stud in the terminal, as seen below. Congratulations!

If you've got either of those ring-making methods right, we'll be re-wiring the motor before you know it. Now there are just two more very easy skills we have to learn.

Go on to Part 5: Covering the Wires with Heat-Shrink Tubing