How to Re-wire a Potted Motor, Part 20: Hooking It All Back Up

Now we’re at the final step to getting your machine back up and running!

Start by sliding your newly-renovated motor onto the shaft.

Tighten the two motor mounting screws securely.

Then, unscrew the terminal body. Note that I’ve tucked the two motor leads behind the terminal mounting bracket. This is so that we can determine the proper length to cut the tails.

Now we’re going to make new connections on the ends of the wires. As we went over in Part 4, you can either make your own eyelet and solder it, or use crimp-on connectors.

Option 1: Self-Made Eyelets

The self-made-eyelet-and-soldering route requires plenty of wire, which is why we’ve left the “tails” of the motor leads so long. You’ll need to calculate where to cut the wire such that you’ll have plenty of material to form your ring. I suggest measuring and practicing on a scrap piece of wire first, so you can be certain where to cut and strip in order to produce a ring that will still reach the post it needs to connect to in the terminal body. If in doubt, cut too long, not too short!

Option 2: Crimp-On Connectors

Here I’m going to do crimp-on connectors, which requires less length and is easier for me to execute. I generally determine where to cut by letting the terminal body hang naturally, supported by the lighting wires that are still connected, and then drawing the motor lead over the knob that it will fit under. I then pinch the wire to the side of the knob furthest from the motor, as shown in the photo, and cut there. This will make the final wire long enough that I can comfortably manipulate it into place.

Next I strip the wire ends to the length required for a crimp-on connector, just 1/4" or so.
 

Then I gather the connectors and, very important, I immediately cut two pieces of 1/8” heat shrink tubing about 1/2" long.

I slide the heat shrink tubing onto the wires first…

…and only then do I attach the connectors and crimp them on.

Then I slide the heat shrink tubing down into place, as seen below. You’ll notice that now I’ve pulled the motor leads OVER the terminal mounting bracket.

I’ve done that so that I can get the wiring a good distance away from everything else, to comfortably fit a lighter under the heat shrink tubing.

Now they’re heat-shrunk and ready to go.

Re-Attaching the Wiring
When the ring connectors are ready, tuck the wiring back UNDER the mounting bracket, in their final position. Pull the red and black wires over to their appropriate posts on the terminal. (Here I’m working on a 201-2, which has a light switch, and you’ll observe I’ve had to thread the black wire underneath a different wire that arches over it, connecting the light switch to the red post.) If you have a cabinet-mounted machine, connect the foot controller wires too, even if the machine isn’t in the cabinet yet. We need to do some testing.

After connecting the right wires to the right posts, we tighten up the thumb screws. Get all three of them as absolutely tight as you can with your fingers.

Now it looks like this. Be sure you’ve got the motor leads tucked BEHIND the bracket…

…then screw the terminal back into the machine. Do NOT overtighten this screw. The terminal body is made of plastic and easy to break. You only want to get it tight enough that it doesn’t wiggle around when you plug the cord into it.

I’ve grossly overexposed the next shot so you can see how the motor leads come down unobtrusively from the motor and disappear behind the mounting bracket.

Now we’re at the moment of truth!

Running the Motor

I plug the machine back in without re-attaching the handwheel, because I want to run the motor with no load--that is to say, not powering the rest of the machine--to ensure that it runs smoothly. This way if the motor doesn’t run, I know it can only be the motor that is the problem, and not some jam somewhere else in the machine.

Then I get the button controller up on the table. (And obviously, you should not stick your fingers inside the motor housing for any reason!)

Here are the results:



That’s the sound of a potted motor 201 running with no load. Sounds very different than when it’s connected to the rest of the machine, no? Sort of reminds me of a jet engine. I’ll continue running it for a few moments to ensure it runs consistently. And if you’ve inserted new brushes, you ought to run the motor for five minutes or so anyway, to wear the brushes in.

Warning #1: If you run the motor as I’ve done in the video above but it sounds different--for example, if it buzzes first and starts haltingly--STOP and unplug the motor immediately.

Warning #2: If you run the motor for a few minutes and it gets warm, that’s fine, particularly if you’ve been running it full tilt. But if it gets HOT, please STOP and unplug the motor immediately.

Both of those warnings are signs that something is wrong with your motor, either in the field core, the windings or the armature itself. And that something might be dangerous, which is why we ought to unplug the machine immediately. Sadly, those problems are currently beyond the scope of this blog.

But hopefully, everthing has turned out fine.

Re-attaching the Handwheel

It’s my habit to unplug the motor when I re-attach the handwheel, though strictly speaking it’s probably not necessary.

The next thing I do is use the grease syringe to dab some droplets of grease around the perimeter of the fiber gear. People often over-grease these things, but you really don’t need to go nuts with it.

Then I put a single drop of oil on the shaft.

Next I slide the handwheel on.

Replace the washer.

Then screw the stop-motion wheel in, all the way.

Don’t forget to tighten the set screw.

That’s it! Congratulations and enjoy your machine!

Back in business.

How to Re-wire a Potted Motor, Part 19: Re-installing the Brushes and Grease Wicks

 

With the armature and worm back in place, we’re now ready to install the final items: The brushes and grease wicks, and then we'll re-fill the grease tubes, as seen above. 

We’ll start with the brushes.

Old Brushes or New Brushes?

If your brushes are clean--meaning you’ve wiped them down with a napkin to remove loose grit and no previous owner has mucked them up with oil or grease--and 3/8” or longer in length, it should be fine. Once a brush gets down to 1/4" or less in length, it needs to be replaced.

With brushes that have been ruined by oil, I’ve read that some people use a flame to burn the oil off of them or otherwise clean them, but I do not have any experience in this area and cannot offer guidance as to whether it’s appropriate. I simply play it safe and replace them.

On that note, a motor expert whom I met in Ray White’s class told me he always replaces the brushes, no matter what.

Where to Get New Brushes

I order my replacement brushes from Jenny at Sew-Classic (here's a link). You may also be able to find replacements in your local hardware store; the dimensions you’re looking for are 3/16” by 3/16” square, and 3/8” or 1/2” long. You can also bring your old brushes down there to match them up.

Installing the Brushes

I’ve often read that people mark the orientation of their brushes when removing them from the motor, in order to be sure they go back in the same way. I don’t think this is necessary; now that you know what a commutator looks like and where it is inside the machine, it’s easy to tell, at a glance, how your brush should go into the machine.

First off observe that the end of your brushes (unless they’re brand-new, I’ll get to that in a sec) have curves worn into them.

That curve is worn into place by the brush riding on the commutator’s curved surface.

And even when the commutator's tucked out of sight inside the motor, the very shape of the potted motor housing echoes that curve.

So, it’s pretty easy to figure out which way the brush goes in; just make sure the curves match up.

As you’re inserting your brush into the brush tube, which we cleaned out earlier, be sure that the brush slides freely in the tube. If you feel it stick, don’t force it in--stop what you’re doing and remove the brush. You’ll need to do a better job cleaning out that brush tube.

Once your brush is inside, screw the brush tube cap on, ensuring that the spring is centered in the cap.

I tighten these caps very gently, since they are made of Bakelite and easy to break.

If your brushes are new, they may be completely flat on the ends. In that case you just insert them, and later you’ll run the motor for a few minutes to wear the brushes into the appropriate shape.

Once you’ve installed the brushes on both sides, we move on to the grease wicks.




Grease

Obviously you’ll need some grease. Be aware that all grease is not the same, they have different viscosities. What you want is specifically Singer-brand grease. If that is not available, you can actually use Vaseline or petroleum jelly, as that is the proper viscosity as well. (I would not recommend using Tri-Flow grease, which is impregnated with Teflon, and there’s debate as to whether the Teflon clogs up the wicks, preventing the grease from getting into them properly.)

In the photo above, below the Singer tube is a syringe from Jenny at Sew-Classic that I’ve loaded up with grease. The syringe is not strictly necessary, but I find it much more convenient to use, and now I’d rather not go back to not using one.

Installing the Grease Wicks

Now we turn to the grease wicks themselves. Here you can see I’ve “screwed” new wicks into the springs, and you can see the topmost one features the spring I mangled out of shape when removing it. 
 

I have tried--and failed--to restore that spring to its original condition, which is okay here because the exact tension of the grease wick springs is not crucial. What you want to do is cut the new grease wicks to be about 3/4" in length, and screw it into the spring far enough that the overall length is about 1 1/8”.

Once that's done, I dab just a few droplets of grease on the business end of the wick, as it will take some time for them to properly absorb the grease we’ll fill the grease tubes with, and I’d like a little lubrication on the shaft from the get-go.

Next I insert the grease wicks into the tubes. Be sure to look inside the tubes first to locate the holes in which to place the wicks.

Following that I place the retaining clips on top of each spring, oriented as in the photos. (Left and right are mirror images of each other.) Be sure the tab on the clip completely covers the spring.

Note that the tab completely covers the spring.

Then, using my forceps, I very gently squeeze the part of the clip encircling the spring. This temporarily bends the clip into itself, just slightly, so that you can slide it down into the tube.

Push the clip down so it’s at least past the first few screw threads carved into the side of the tube. You don’t have to shove the clip down all the way; later when we screw the caps in, the caps will push the clip down to the appropriate place.

Next I use the syringe to load the tubes up with grease.

You don’t have to go nuts here, just fill the empty spaces with grease, as shown in the photo. If you put in too much, it’s going to squirt out onto the caps when we screw them on, and we don’t want to do that.

Now we screw the caps in. If you can’t get a good grip with your fingers, don’t forget you can always use a penny to tighten them.

Next we pop the motor cover back on, and tighten the screws.

They don’t have to be terribly tight, so don’t knock yourself out; the chances of the motor cover vibrating off of the machine are slim.

We’re almost ready to go!

Go on to Part 20: Hooking It All Back Up