201 potted motor drive
 

i just thought I'd post a couple pictures to show how a 201 potted motor actually spun the main shaft. I am supposing a 15-91 and the green variant is very similar. I was surprised that the clutch stop washer was different from a belted motor.

whoops didn't show drive

Thanks for sharing. I have got two beltet versions of the Singer 201k. I think the original motor i very weak, and from the information I have got on the potted motor, it is weak too. I have tried to figure out the gearing of the this potted drive from some photos from a Singer sewing machine blog. But I am not quite sure of this. I found 10 teeth on the motor shaft and 48 teeth on the main flywheel shaft. Can you confirm these figures?

The machine isn't near me right now, but I'll check for you.

I'm wondering what you consider weak. Weak would not be a word that I would associate with 201s from what I have read about these machines. According to https://sewalot.com/singer_201k_sewalot.htm Rolls Royce used the 201 for some of their upholstery and dashboards. Also, some English bookbinders switched from industrial machines to the 201. Doesn't sound like they are 'weak.'

Janey - Neat people never make the exciting discoveries I do.
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Thanks for your comment OurWorkbench.

I think that the 201 have got some excelent and strong mechanics, and it can gain a lot from having a stronger electric motor, that the original to domestic purposes. This is an example of the strength of a 201k with a modified drive:

Video of Singer 201k sewing plywood

According to my information, the potted motors used in the US have a 0.6 A rated input current. Many machines produced by Japan in the 1950-1970 for the US market had external motors with an input current of 1.0 - 1.5 A. I know, that it do not transfer directly to shaft power of the motor, but I think most electric motors at the time had higher input current than this 0.6 A and therefore the potted motor most likely have got lower shaft power than many other machines on the market.

For the European market the 201k was almost all belt driven with external motor. I have got two of those. I have measured the shaft torque and shaft power of one of these motors (produced 1950) and compared it to motors from a 66k (from 1930), the motor of a Singer 237 and a modern cheap motor from China. The result is here:

https://www.quiltingboard.com/attach...1&d=1593790316
(I own the copyrights of this line chart in png-file)

As you can see, the motor of the 201 got the lowest shaft power in this comparison.

I do not know why the original motors for 201 was chosen to be so weak compared to motors of other sewing machines. I guess that special versions with stronger motors were sold for industrial use in upholstery and bookbinding.

Who on the hell wants to sew or would even think about sewing plywood for a start? While i don't own a model 201, i do use a 15-91 on a daily basis and have found no problems at all with weakness in the motor (regardless of material). Baffles me this kind of talk tbh. If you want a bit more punching power then swap the solid handwheel with the older spoked version i say https://cdn.quiltingboard.com/images...es/thumbup.png

I agree, that sewing plywood is rare, but I know it was used for some panels in the Vintage MB sports vehicles. I have got this couple of references too:
https://www.icd.uni-stuttgart.de/tea...-bent-plywood/
https://materialdistrict.com/article/sewing-wood/

The video above that show a 201 sewing plywood is mostly a statement about what the machine is able to do with sufficient driving punching power. The video channel show other examples too. I think the Singer 15 can be modified to sew plywood or other heavy materials as well. But the potted motor will be insufficient for that.

Until I see some new data, I stick to my the statement about the potted motor is weaker than other typical sewing machine motors. I guess that some people are convinced by dreams and others by figures and tests.

A lot of people love their Singer 15-91, and this machine can most likely do more heavy stuff that most domestic machines in general. The newer domestic plastic machines are no match to the good vintage machines.

Makes no sense to me in using one of these type of machines for this kind of purpose. Was never designed for that kind of work at all is my point. Anyone serious in this kind of work would never look at this kind of machine for that kind of work in my opinion. Would never produce the same level of finish and provide nothing but headaches. Interesting post, just seems pointless in the real world.

Could just swap a motor, stand back and see what breaks first.

https://www.quiltingboard.com/member...98-600603.html

Efficiency based on rated amps of belt drive motors does not apply to the 201K2, being a gear drive. The gear drive is so much more efficient since it does not suffer from the drawbacks of belt drives. If you can do it, measure the output at the main drive shaft, not the motor shaft. Measuring the motor output does not take into account the belt tension,and power losses result. At the needle my 15-91 has far more "power" than the belted model.

Leon- I don't have a 201 for a direct comparison, but it appears that the gear case is interchangeable between the 15-91 and 201k2..

Gymnast- You're probably right on the gear count of 10-48. I had no quick way to attach a degree wheel to the motor output, but spinning the handwheel 1 revolution produced between 4.5 to 5 turns at the motor. Hard to visualize the exact locations on the end of motor shaft, but close enough.

Measurement on the main shaft could give more reliable information. But we do not have that.

V-belts should have an effieciency of about 90-96 % according to this reference. But with belts the effieciency do depend on maintenance factors, so of cause it can be bad.
Book on transmission

Worm gears with a gear ratio of 1:5 should have an effiecency of about 90 % according to this reference:
Article on worm gear

So from a theoretical point of view, I do not find a big difference in the two ways of the drive. I guess, that the V-belt may have some more static friction. But in both cases the static friction of the commutator in the motor will be significant.

way off topic. Chevrolet Corvairs had fan/alternator belts that had two 90 degree bends in them .I always questioned their efficiency. Never owned one.

When I see the potted motor sold from ebay, the seller claims that the motor with drive can be used on both the 201 and 15-91. However you need to be aware, that the bobbin winders are different, because different bobbins are used.

Good to know, Thanks Gymnast2