Custom speed reducer pulley for Singer 51W56

[FDC]

I was lucky to find this old post bed Singer locally. I have wanted a post bed for up coming boot projects but didn't really want to blow new machine money. Total tear down, fabricated the table and went with a servo motor drive. I will machine up a slip on driven pulley to further slow it down. Thrilled for find a spot in FLA that sold water decals for it.

I machined a new needle jbar that will take 135 needles to get me to #20 thread.  

I enjoy getting to understand these old mechanisms and give respect to the geniuses that created them so long ago. 

Edited June 6 by FDC

[Northmount]

1 hour ago, FDC said:

I was lucky to find this old post bed Singer locally

Good reason to post in show off, but I've moved it to leather sewing machines.

[FDC]

I have finished my speed reducer pulley for my 51W56. It slips on over the stock flywheel and is fixed there by set screws which fit into the stock flywheels set screw holes. My serve drive to 51W driven ratio is 2.07 to 1 now. It requires 4 1/2" 6061 rod to make. 

[nylonRigging]

looks like you spent time putting some thought into that overhaul . Very nice job .

.

[kgg]

On 6/6/2025 at 1:07 AM, FDC said:

I will machine up a slip on driven pulley to further slow it down.

Very nicely done. My suggestions on speed reduction:

i) if you need to slow down the machine and reduce servo motor "speed jump" you should add in a speed reducer pulley. Most of the brushless servo motors have a minimum startup speed of 500 rpm and a pulley size of 50mm. With some of the brushless servo motors the initial increase in speed from 0 to 500 rpm, speed jump, can be a problem.

With your arrangement by increasing the size of the hand-wheel pulley size from 2 3/4" (70mm) to approximately something just under 4.5" say 110mm you did gain some reduction in speed.

Example A:

i) Without the new hand-wheel pulley the speed of would have been 357.1 rpm with a minimum startup speed of 500 rpm at the servo motor.

ii) With the new hand-wheel pulley the speed would be reduced to 227.3 rpm with a minimum startup speed of 500 rpm at the servo motor.

To help with smoothing out the speed jump with the side benefit of increased torque install a speed reducer pulley between the servo motor and the new hand-wheel pulley.

Example B:   

1) With the new hand-wheel pulley and a minimum startup speed of 500 rpm at the servo motor.

i) install a 3:1 speed reducer pulley having a typical size of 6" large pulley and 52mm" small pulley the speed of the new hand-wheel pulley will be reduced to 78 rpm

If you had just used the original hand-wheel pulley size of 2 3/4" (70mm) and a minimum startup speed of 500 rpm at the servo motor the speed would have been reduced to 122 rpm at the hand-wheel.

kgg

 

[FDC]

On 6/9/2025 at 5:35 PM, nylonRigging said:

looks like you spent time putting some thought into that overhaul . Very nice job .

.

Thanks! I did try to think this one through, except for the amount of time it would take...

[FDC]

On 6/10/2025 at 7:43 AM, kgg said:

Very nicely done. My suggestions on speed reduction:

i) if you need to slow down the machine and reduce servo motor "speed jump" you should add in a speed reducer pulley. Most of the brushless servo motors have a minimum startup speed of 500 rpm and a pulley size of 50mm. With some of the brushless servo motors the initial increase in speed from 0 to 500 rpm, speed jump, can be a problem.

With your arrangement by increasing the size of the hand-wheel pulley size from 2 3/4" (70mm) to approximately something just under 4.5" say 110mm you did gain some reduction in speed.

Example A:

i) Without the new hand-wheel pulley the speed of would have been 357.1 rpm with a minimum startup speed of 500 rpm at the servo motor.

ii) With the new hand-wheel pulley the speed would be reduced to 227.3 rpm with a minimum startup speed of 500 rpm at the servo motor.

To help with smoothing out the speed jump with the side benefit of increased torque install a speed reducer pulley between the servo motor and the new hand-wheel pulley.

Example B:   

1) With the new hand-wheel pulley and a minimum startup speed of 500 rpm at the servo motor.

i) install a 3:1 speed reducer pulley having a typical size of 6" large pulley and 52mm" small pulley the speed of the new hand-wheel pulley will be reduced to 78 rpm

If you had just used the original hand-wheel pulley size of 2 3/4" (70mm) and a minimum startup speed of 500 rpm at the servo motor the speed would have been reduced to 122 rpm at the hand-wheel.

kgg

 

Acknowledged and all true however I had chosen to make a small table and space for a reducer pulley under the top was not really an option. I also tried to get this 51W56 off the ground for as little scratch as possible and that was easiest with aluminum that I had in stock. I slowed down my skiiver as you suggested and I like the results!

[friquant]

@FDC Will you post a photo of the motor pulley you're using?

[FDC]

I'm not sure what you mean by motor pulley, are you referring to the pulley on the servo motor? If so its stock, 45 or 50 mm I think.

[GerryR]

I realize that you already have the DC servo drive, but for future projects, you should consider an AC system with a variable frequency drive (VFD) and a 3 phase inverter rated gearmotor.  As an example of the control you would have, a 3 ph, 3/8 HP, 5:1 gearmotor can be operated from 10-90 Hz giving an output shaft speed of 35-459 rpm. Any speed running with less than 60 Hz is in constant torque mode, and greater than 60 hz is in constant horsepower mode.  The speed is controlled by a variable pot, not a link to an optical control and is easily top-speed adjustable, giving full range of the pot for control to the selected top speed.  The VFDs are relatively inexpensive, but the motors are a little pricey depending on your source, but for control, I think they are better than DC systems.  JMO, YMMV.  

P.S. Beautiful job on that machine!!

Edited July 12 by GerryR