Electric Motor theory – why and how we lubricate

There have been a lot of discussions about sewing machine motor lubricants over the years and I thought I’d take a step further back and discuss why we do this, how we do this and why some of the information “out there” is sort of F.U.D. (<- Wikipedia Link)

First off:  Why do we lube or oil a motor?  (I’m a why person, have you noticed this yet?? I’m quite sure I drive some people nuts with my “whys?”… )

Let’s start with an analogy: a car’s motor (or internal combustion engine) Even the most basic version of this motor uses a sump system to make sure that things are receiving the oil that they require.  This delivery system pumps oil (via an oil pump) to where it needs to go so that your engine stays cool and relatively friction-free while producing an amazing number of controlled gasoline fueled explosions per minute in order to generate the power needed to move the car.  This is a well controlled automatic lubrication delivery system.  Without proper lubrication, there would be too much friction between things like the pistons and the cylinder walls that – when combined with the heat – would cause the engine to seize or in a situation of under lubrication – incur significant wear.

You’d never run your car without oil or “down a few quarts”, right? Even if you’re not a car person, you probably know that’s a bad idea.

Now, let’s look at how that analogy applies to a sewing machine:

Besides the method of power generation (electricity vs. combustion) the next most notable difference would be the lack of an automated lubrication delivery system.  Some industrial sewing machines have somewhat more complex oil delivery systems but let’s forget about them for the moment.

In the absence of an automated system, YOU become the lubrication delivery system.  On your vintage machines, you do this by giving various parts of your machines a drop of oil every X hours.  A very good rule of thumb is everything that’s rotating or reciprocating (i.e. moving up and down or side to side) should be oiled every 8 hours of use.  If it’s rocking, it should be done every 6 months.

This 8 hours is great for spinning things that you can see but many of us forget that the motor is spinning too – mainly because it’s in a housing and behind the machine so it’s easy to miss that motion.  The thing is, the motor is spinning way faster than the fastest spinning part on the sewing machine itself.  It’s true – look how many times the pulley on the motor spins vs. how many times the handwheel spins.  If the rule of thumb is based on the machine and not the motor, you should be lubricating the motor way more often.   I think that the manufacturers (Singer, White and others) knew that this would be a pain and not get done, so the developed a sort of “passive” lubrication system. Not automatic, but you don’t have to do it every 15 minutes either.

Enter the grease wick system. A very simple solution to a fairly complex problem.

Because there are far fewer moving parts in an electric motor, we can get away with a wick system.  Technically, we’re lubricating only the main shaft and the bushings that it rides in.  These bushings are special bushings made of copper or bronze– both are somewhat porous metals that can hold tiny bits of oil to reduce friction between the bushing and the shaft.  The grease wick (or on some non-Singer motors – an oil wick) takes advantage of this ability to hold the grease/oil as well as one other natural byproduct of a motor – heat.   As the motor runs, it heats up due to friction on the bushing and shaft.  A small amount of heat melts the grease that the warmed shaft makes contact with and the grease flows into the bushing and shaft area.   This creates lubrication which reduces friction and heat.  This effectively “turns off” the need for lubrication again until the shaft warms up again because it’s used up that allocation of melted grease.

Why is reducing friction so important?

Friction causes heat and wear – both are destructive forces in a motor so we need to reduce both.  With enough friction, we also lose performance and eventually the motor can be damaged beyond repair.

Why am I supposed to use a particular lube?

Motors that call for grease in their grease ports should have grease, and motors calling for oil should have oil.  This is how the manufacturer built the motor to function its best and there’s no really good reason not to adhere to the kind of lubrication specified.

The brand of lubricant that you use is up to your own preference as long as its properties are suitable for the intended use.  Companies like Singer used to say to use their grease only or calamities would happen, small kittens would be harmed, etc.  This part was marketing and propaganda.  It also could cross the line into F.U.D. – Fear, Uncertainty and Doubt.

What does suitable mean? This means no synthetic greases, no greases with additives (like PTFE), no 3in1 oil, no salad oil, coconut oil, baby oil, etc.    If the grease you use for a motor calling for grease is a low melting point organic (i.e non-synthetic) grease – it should be fine.    Sewing machine oil should also be fine for a motor calling for oil.

I used the wrong lube, Is it wrecked?

If you put sewing machine oil into a motor that’s supposed to have grease – it’s potentially OK depending on how much you put in.  If it was a couple of drops (not 22 drops because they were small), this actually may help a little because it can wet the wick inside the grease tubes and help get the grease flowing.  If it was more than a couple of drops, the motor should be disassembled and inspected/cleaned for oil seeping past the bushings.

If you used a synthetic grease (This includes Tri-Flow synthetic grease in the tube.) where an organic grease should be used,  it needs to be removed.  The motor should be inspected and the grease wicks changed before refilling the grease cups with the proper grease.  Synthetic greases typically don’t have a melting point and will therefore not protect the motor. Additionally, the additives in some greases may clog the wicks.

If you used anything other than sewing machine oil in a motor calling for sewing machine oil – especially if you used 3in1 oil in your motor – it should be inspected and cleaned and the wicks changed then the right oil used for the motor.

If you put grease or oil in where the brushes go – the motor MUST be repaired.  See the photo above this section for what the brush tube usually looks like.

I’ve heard that the wrong lube will “flood” the motor.

This is somewhat of a misinformation or at the very least it’s an exaggeration.  In a properly running motor this is nearly impossible.

Properly greased, there is typically a bead of grease that’s maybe the equivalent of 2mm ( less than 1/10″) in diameter squeezed in around and through a felt wick into a tube that’s roughly an inch long.

Note:  Some motors will have a wick “screwed into” a spring in the grease tube.  Some will have only a wick.  Some have neither.  NO motor will have a motor brush where the grease goes.

In short, a very small amount of grease resides in those grease tubes.  The motor is only liquefying the very tip of that grease that’s touching the armature shaft of the motor.  In order for the grease to “flood” a motor, all of it (and then some) would have to be liquefied in a short period of time.   The only way this would happen is if the motor was running really hot (belt too tight or too much load on the machine) and even then, there’d likely have to be a large excess of lube forced in as well.  Or it would have to have been massively over filled then overheated several times over the life of a machine.

If some grease/oil did get past the bushing and into the guts of the motor – there’s a remote chance that the commutator (<-Wikipedia Link) and the armature (<-Wikipedia Link) may see some – which are the parts of the motor that don’t want to be lubricated.

I hope this clears up a little bit of why lubricating motors is so important and why we lubricate with what we do.  I usually find if I know why I’m supposed to do something, I’m more likely to do it.  How about you??

Today’s post title- Night Ranger – Sister Christian

P.S. My next post – that’s already in progress – is going to be about suitable grease for Singer motors.

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