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.

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.

How to Re-wire a Potted Motor, Part 18: Re-installing the Armature and Worm

Folks, we’re now very close to the end. Having succesfully completed the actual re-wiring, your machine should now be up and running in no time. But first we have just a few more mechanical steps to get through.

Now we'll start closing the motor up, in preparation for re-attaching it to the rest of the machine. First, grab the worm, and I’ll show you a little time-saving trick.

How to Re-wire a Potted Motor, Part 17: Cleaning the Commutator

Now that our potted motor has been rewired and is partially back together, we need to put the armature back inside. But first we ought to clean the part of the armature called the commutator. The commutator is the series of copper bars arrayed in a ring. They are what the motor brushes make contact with, and they need to be smooth and clean so that electricity can be transmitted between commutator and brush.

The Singer manuals all say to clean your commutator with nothing more than a pencil eraser, but in practice that’s never worked for me. Perhaps it was a valid fix five or ten years into the life of the machines, but some of mine are from the 1930s and require more aggressive cleaning techniques involving a power drill and some sandpaper. The best thing to use is actually a rubber honing stick, but as I'm guessing most of you don't have access to those, I'll show you how to do this with sandpaper you can find in any hardware store.

How to Re-wire a Potted Motor, Part 16: Re-attaching the Field Core

Now we’ll begin closing the motor back up. Please orient your motor as shown in the photo above, which is the way we had it in Part 15.

Then note that there will be a potential problem in closing it up, as seen below:

If we’re not careful, the bottom motor lead will block one of the screws that attaches the field core to the rest of the housing.

How to Re-wire a Potted Motor, Part 15: Soldering On New Motor Leads

Now we’re finally ready to solder new motor leads on. Again, please ensure that your motor is oriented exactly as in the photo below, to ensure my explanations of “top/bottom” are correct:

Motor oriented with field core at left, bobbin winding assembly at top right.

Ready? Let’s begin.

How to Re-wire a Potted Motor, Part 14: Replacing the Motor Housing Grommet

I almost forgot! Before we take the big step of soldering the new motor leads on, there’s one more thing we ought to check, as this is easier to do while we’ve got the motor leads clipped and out of the way. Take a look at the rubber grommet covering the hole that the motor leads will eventually go through.

Here I can see this one has a crack in it:

How to Re-wire a Potted Motor, Part 13: Cutting and Prepping the Motor Leads

Now that we’ve got the motor as open as possible, we’re going to cut the motor leads at specific points to prepare for soldering new ones on.

First, very important, please orient your motor as shown in the photo above: The field core is to the left, the bobbin winder is at the top right. We need to have our motors oriented the same way so when I say “right/left/up/down” you’re not getting confused and cutting the wrong thing.

How to Re-wire a Potted Motor, Part 12: Detaching the Field Core

Now we need to access the motor leads so we can replace them. To get to the motor leads, we need to detach the motor’s core, or field core, from the motor housing. As you’ll see, we cannot detach it completely; although we will physically separate it from the housing, it will remain attached via two wires. (In the photo up above, the two wires in question look like water mocassins.) We must be careful not to disturb those two wires.

The first thing you’ll need to do is remove these two screws.

How to Re-wire a Potted Motor, Part 11: Armature & Worm Removal

With the grease wicks removed (and the motor brushes if they were willing to come out), it is now time for us to crack the motor open. In this entry we will learn to remove the motor cover and perform the crucial task of safely removing the armature. We will also learn the difference between a worm and a worm gear.

How to Re-wire a Potted Motor, Part 10: Motor Brush Removal

In preparation for removing the armature and cracking the motor open, we're now going to remove the two motor brushes. For those of you with no electric motor experience, they’re not “brushes” in the conventional sense; they’re little sticks of carbon that look like charcoal sticks. They reside in a tube leading into the motor and are covered by caps. There is one on the top of the motor, one on the bottom. And as you'll see, inspecting them can provide a good warning as to whether you'll be able to save this machine or not.

How to Re-wire a Potted Motor, Part 9: Grease Wick Removal

Now that we’ve got the motor separated from the machine, we can store the machine someplace else, to free up some desk space. We won't come back to the machine for a while.

Our next goal is to get the motor open. In order to do that we need to remove what’s called the armature, and if you don’t know what that is, you’ll see it shortly. In order to remove the armature we should first remove the grease wicks and the motor brushes, a multi-step process.

How to Re-wire a Potted Motor, Part 8: Motor Housing Removal

Now that we’ve got the motor leads disconnected (as shown in Part 7), we need to remove the motor housing in order to access the motor.

To get to the motor housing, we first need to remove the handwheel. I would ordinarily also disassemble and remove the bobbin winding assembly, but because that is an operation in its own right, I will save that for another entry and leave it attached to the motor housing. (Leaving the bobbin winding assembly on is not “standard operating procedure” for me, but as long as we are careful, we should be fine.)

How to Re-wire a Potted Motor, Part 7: Disconnecting the Motor Leads

Okay folks, time for us to get our hands on the machine.

Before removing the motor from your 201-2 or 15-91, we must first disconnect the motor leads. From here on in we’re going to need lots of different screwdriver bits, so be sure to read the entries on proper screwdriver bits if you’re unclear on this area; if you use the wrong type of driver and strip a screw in the middle of a motor re-wire, you’ll find it a huge hassle.

Step one is unplug the machine. Not at the wall, but at the terminal body.

How to Re-wire a Potted Motor, Part 6: The Underwriter's Knot

This is the last thing we need to learn before moving on to the machine! Congrats if you’ve made it this far.

After we eventually solder new wires onto the motor leads, inside the motor housing we’ll need to tie those new wires into what’s called an underwriter’s knot before we push the wires out through the housing.

An underwriter’s knot provides strain relief, so that if we tug and pull on the wiring while we’re installing the motor, it will not place any stress on the motor leads where they join with the motor’s field core. (The knot will simply catch on the inside of the housing.) This is very important, because if you break that connection at the field core, your potted motor then becomes a potted paperweight.

We’ll practice outside of the machine to be sure we can get the knot right. Ready?

How to Re-wire a Potted Motor, Part 5: Covering Wire Joints with Heat Shrink Tubing

Now that we’re able to solder two wires together, we’ll use heat shrink tubing to cover the soldered joints. It’s quick and easy.

Heat shrink tubing is just a little tube of thin, rubber-like material. You cut it to length with scissors. Then you slide it over your wire joint, apply heat with a cigarette lighter or heat gun and it shrinks a predetermined amount, acting as insulation and protection. It comes in different sizes and many different materials, but there's a particular kind we need.

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.

How to Re-wire a Potted Motor, Part 3: Learning to Solder

Once you’ve mastered wire stripping and braiding (as shown in Part 1) and understand the tools you’ll need (explained in Part 2), we can get down to actual soldering practice.

First thing I’ll say is, a soldering iron is dangerous. So is a kitchen stove and a steak knife. Because we learn early on to use a stove and a knife with care, we can use them daily without having any accidents. That same care should be taken with a soldering iron. Here are some steps I recommend:

A. Clean up your workspace. The soldering iron needs a dedicated place to rest where nothing else is near it. The tip gets extremely hot and there should be no chance it will accidentally touch anything, either while it is at rest or while you are using it. Remove all obstructions from your work area, leaving only the things you will need to do the job.

How to Re-wire a Potted Motor, Part 2: Tools/Materials Required for Soldering

You only need the one in the middle

If you can learn to solder, you can breathe new life into that basket-case 15-91 or 201-2 you’ve got with the rotted wiring insulation. If you’ve mastered the wire braiding we went over in Part 1, now you’re ready to try soldering. But before we get to that, I’ll describe the proper tools required, because I don’t want you to overeagerly buy the wrong items first like I did. Read this before you spend any money.

Also consider this: The soldering process requires holding the tip of a soldering iron against your wire joint to heat it, then adding solder. It requires a fairly steady hand--you may have to hold the iron steady for 30 seconds or longer with some precision--so if you have grip issues or arthritis, you may find this challenging; please read the “arthritis” paragraph at the bottom.

Tools and materials you’ll need:

How to Re-wire a Potted Motor, Part 1: Wire, Wire Stripping, & Wire Braiding

Singer’s models 15-91 and 201-2 come with beltless, direct-drive motors colloquially called “potted” motors. Sometimes the wiring inside is shot and needs to be replaced; half a century of temperature extremes can rot the insulation away, leaving dangerous bare-metal wires inside an all-metal machine that can transmit a shock to the user.

In this series of entries I’ll teach you to re-wire a potted motor. I’m writing this for people with zero experience, so there are quite a few tools and skills we’ll need to cover. The good news is, you can practice all of these skills without touching your sewing machine, so you can be sure you’ll be able to pull this off before you open your machine up.

Also be aware that you’ll need to acquire a fair amount of tools and materials to re-wire a motor. You or your spouse may already own some. In a nutshell, what we’re ultimately going to need is:

- Wiring
- Wire Strippers/Cutters
- Soldering Iron
- Solder
- “Helping Hands” Tool
- Heat Shrink Insulation
- Heat Gun or cigarette lighter

In addition, you may also need a crimping tool and ring connectors; you'll decide for yourself after we cover how to terminate the wire in a future entry. And don’t worry if you don’t know what some of this stuff is, we’ll eventually get into all of it.

More Updates Soon, and Send Me Craigslist Photos to ID!

Have you gotten any better at ID’ing Singers from Craigslist photos? I hope so, as it can really pay off. Case in point: I’m selling a 201 to an acquaintance, and she needs a table for it. I started cruising Craigslist looking for cheap sewing machine tables/cabinets to buy, and came across this one for $30 (cheap for the NYC area):

I immediately recognized it as a 206, Singer’s first zigzag. At 30 bucks I couldn’t pass it up, so I went the next day and fetched the machine. Not a bad deal; I've got a table for my buyer and scooped up a great machine in the process. 

So how could I tell it was a 206?
 

The giveaways that this was a 206

Model 206s are not easy to come by, and the ad was a week old by the time I stumbled on it. If the person had put “Singer 206” at the top of their ad, I’m sure the machine would’ve been long gone. 

If you need help ID’ing a Singer from a crappy photo, e-mail me a photo or a link to the ad, and I’ll identify it for you if I can. (I’ll post those photos and explanations here, but don't worry, I won't post the link to the ad if you're worried about competition from other buyers.) You can e-mail me at:

vintage (dot) singers (dot) nyc (at) gmail (dot) com 

Due to popular demand, I’ve been working on tutorials for how to re-wire a potted motor, like you’d find on a model 15-91 and a 201-2. Because I’m writing it up “… For Dummies” style, it is going to be long. I am aiming this tutorial at people who have zero electrical experience, so there’s quite a lot of information and tips I need to convey, and even reviews of different tools you can do the job with. Please be patient and I'll starting posting the multi-part series soon. 

In the meantime, feel free to send those Craigslist photos if you need help.