What does a needle position servomotor do on leather sewing machine?

[Cumberland Highpower]

Is there any particular reason why every servo and clutch motor made comes with such a large pulley on the motor shaft?  Generally, the first thing I do is toss the original pulley and replace it with a smaller diameter one just like Constabulary does.

 

Edited October 13, 2022 by Cumberland Highpower

[CowBoyOUTLAW]

14 hours ago, Cumberland Highpower said:

Is there any particular reason why every servo and clutch motor made comes with such a large pulley on the motor shaft?  Generally, the first thing I do is toss the original pulley and replace it with a smaller diameter one just like Constabulary does.

 

Large pulley most definitely avoid slipping

[CowBoyOUTLAW]

17 hours ago, Constabulary said:

So how much speed reducer reduction will this motor / needle positioner now accept? 1:2, 1:3 or even more?

Does it matter how big the motor pulley is? Usually these motors comes with ~75mm pulley but most LW swap it to 40-50mm pulley.

I´m just a user but not an electronics geek so this question may sound stupid (maybe not).

Is there (probably) a way to adjust the "reduction acceptance" (I have no other word, sorry)  in the motor management menu? That would be a great feature.

 

Thanks for your idea, users might be not happy to adjust some parameters in motor management menu, so we set wide range ratio in motor board, acocording to HT-SP03 Bearing drive Speed Reducer, the gear ratio is 1:3 (https://www.cowboysew.com/slow-speed-sewing-machine.htm)

[kgg]

14 hours ago, Cumberland Highpower said:

Is there any particular reason why every servo and clutch motor made comes with such a large pulley on the motor shaft?  Generally, the first thing I do is toss the original pulley and replace it with a smaller diameter one just like Constabulary does.

A good example of the belt contact surface would be:

i) a 75mm diameter circle would allow a belt to contact with half of the circle at any given time. That means the belt actually contacts 117.81mm of the pulley surface

ii) a 50mm diameter circle would allow a belt to contact with half of the circle at any given time. That means the belt actually contacts 78.54mm of the pulley surface

iii) a 40mm diameter circle would allow a belt to contact with half of the circle at any given time. That means the belt actually contacts 62.83mm of the pulley surface

A 40 mm circle would only have 53.33 percent of the contact surface as a 75mm circle.

kgg

[Cumberland Highpower]

On 10/13/2022 at 10:01 PM, kgg said:

A good example of the belt contact surface would be:

i) a 75mm diameter circle would allow a belt to contact with half of the circle at any given time. That means the belt actually contacts 117.81mm of the pulley surface

ii) a 50mm diameter circle would allow a belt to contact with half of the circle at any given time. That means the belt actually contacts 78.54mm of the pulley surface

iii) a 40mm diameter circle would allow a belt to contact with half of the circle at any given time. That means the belt actually contacts 62.83mm of the pulley surface

A 40 mm circle would only have 53.33 percent of the contact surface as a 75mm circle.

kgg

 

I guess I should have just said "I don't know why an Engineer with any real world experience in actually using servo motor of this type, would draw up (as an OEM) a large drive pulley on a servo or clutch motor?" rather than just posting it as a rhetorical, slightly sarcastic question.

 

Edited October 15, 2022 by Cumberland Highpower

[kgg]

3 minutes ago, Cumberland Highpower said:

I think we all understand the physics of a "larger" pulley/belt friction/contact surface area and drive speed KGG

Personally I have never had a much of a problem with belt slippage on any of my machines and haven't needed to fiddle with the servo motor pulley size. When belt slippage has happened I was asking/hoping it would punch through something that was beyond the machines sewing limits. In those cases the belt slippage was a good thing and prevented possible damage to internal parts. lf I were to consider putting a speed reducer on or changing the servo motor pulley size it would be just to gain lower speed control not for extra punching torque.

In the end I guess the Engineers who design the machines have to take into account the stress that can be placed on internal parts and what size of motor / pulley sizes that would best accommodate the majority of users for a particular machine.

kgg