Changing pulley on Jack JK 563a servo motor

[rnzo]

Hi all,

I'm almost done renovating a Necchi 840 (which is a clone of a Pfaff 335), and I am at the stage of installing the servo motor.

I bought a Jack 563a servo motor (which is probably a bit overpowered), and the minimum speed is 200 rpm, which for me is still too fast.

I've been thinking of using a smaller pulley (like 45mm which is quite common or 40mm which is a bit more unusual)  on the servo.  I'm aware of the 13mm shaft considerations (I'm planning to use a 15mm shaft pulley with some inner tubing to adapt to  the 13mmm shaft, I think this was mentioned by Uwe on this forum).

My hope is that the 40-45mm pulley would slow the servo enough for my purposes, without having to build a full reducer with pulleys, bearings and an extra belt.

However, I'm facing a fundamental problem:  how do I unscrew/remove the nut that secures the pulley to the shaft ?  It find it super tight and can't really get a good grip on the pulley.

I tried to heat the nut with a heat gun, hoping it would expand with the heat and ease a bit, but was not successful (or maybe I need to try for a longer time).  Or maybe it's time to hit the gym on a more regular basis?

Any suggestion or tip would be very welcome (I read the tip about using a gear puller to get the pulley out, but I'm not yet at this stage!),

Lorenzo

PS:  The Necchi 840 was sold for parts, and I have been cleaning, renovating and fixing it.  Sadly, the top shaft that supports the balance wheel is slightly bent near the balance wheel.

This is not too bad as I don't intend to run it over say 150spm, but because of this deflection I don't really consider changing the balance wheel for a larger one, thus I am looking at the servo pulley or a speed reducer. 

 

[CowboyBob]

Get some large adjustable pliers & grip the pulley in the groove.OR you could put a belt in the pulley & hold on to it real close to the pulley while trying to loosen it.

[rnzo]

Thanks a lot Bob, very much appreciated!

The second approach (use belt in the pulley) reminded me of these rubber gizmos from my youth that we used to get better grip to open jam jars...

I went with this approach as with pliers I was concerned of leaving marks on the pulley.

And indeed, it  seems obvious *after* reading your suggestion, that as the V belt can transfer so efficiently torque to the sewing machine shaft, it can be used to get a good grip on the pulley.

Took me 5 mins, mostly finding the right body position so I could apply enough torque, and to remove the nut.

 I'm now off to order a gear puller (which will also help to remove say balance wheels if i need to do this in the future) to get the pulley out.

Thanks again and wishing everyone a happy Sunday!

Lorenzo

[CowboyBob]

6 hours ago, rnzo said:

Thanks a lot Bob, very much appreciated!

The second approach (use belt in the pulley) reminded me of these rubber gizmos from my youth that we used to get better grip to open jam jars...

I went with this approach as with pliers I was concerned of leaving marks on the pulley.

And indeed, it  seems obvious *after* reading your suggestion, that as the V belt can transfer so efficiently torque to the sewing machine shaft, it can be used to get a good grip on the pulley.

Took me 5 mins, mostly finding the right body position so I could apply enough torque, and to remove the nut.

 I'm now off to order a gear puller (which will also help to remove say balance wheels if i need to do this in the future) to get the pulley out.

Thanks again and wishing everyone a happy Sunday!

Lorenzo

The pulley should slide off by putting a wrench or screwdriver behind it & prying alittle.

[rnzo]

21 hours ago, CowboyBob said:

The pulley should slide off by putting a wrench or screwdriver behind it & prying alittle.

And sure enough the pulley is so close to the body of the motor that inserting some cardboard  (for some protection) and sliding a flat head screwdriver, and then gently turning the screwdriver is an easy way to free the pulley from the shaft!

Thanks again Bob, now I just have to be patient till I receive my 45mm pulleys and 15mm aluminum tube!

[MarB]

I 3D printed the pulley for the same motor out of PETG and so far so good. It is pain to print because of overhangs and needs to be 100% filled (first one cracked). But on the plus side, any size you want. This is my model - https://www.printables.com/model/164654-smooth-parametric-pulley.

[MtlBiker]

On 3/6/2023 at 3:27 PM, rnzo said:

And sure enough the pulley is so close to the body of the motor that inserting some cardboard  (for some protection) and sliding a flat head screwdriver, and then gently turning the screwdriver is an easy way to free the pulley from the shaft!

Thanks again Bob, now I just have to be patient till I receive my 45mm pulleys and 15mm aluminum tube!

Just FYI, when I changed the motor pulley on my flatbed machine to 45mm, after installing I found there was a rhythmic sort of knocking sound, very noticeable at lower speed.  I couldn't understand it.  I'd bought that pulley from the same authorized Consew dealer where I'd bought the machine.  I was convinced that my motor was defective.  This was during Covid and it wasn't easy to even find a dealer who was open, but I ordered a replacement motor.  When it came in, the first thing I did was remove the pulley from my old motor (without removing the motor from the table) and install it on the new motor.  And with the motor on the floor, I plugged it in and ran it to test.  I was very surprised that I had the same knocking sound with the new motor.  I took off the pulley and ran the motor... perfectly smooth and quiet.  I ran my old motor without the pulley and it too ran perfectly.  I put the original pulley back onto my motor and it too was perfect.  The problem is the 45mm pulley I had.  The diameter of the inner part of the pulley was 30mm while the original was 27.5 and the original also was slightly tapered.  And maybe the pulley wasn't properly balanced.  I called the supplier of the new motor and he said that yes, it was a known issue and that a pulley had to be perfect.  He sold me a "good" pulley and when I got it and installed, it was perfect.

So, if you have any issues after installing, suspect the quality of the pulley first, before getting a new motor. 

 

[Wizcrafts]

1 hour ago, MtlBiker said:

The problem is the 45mm pulley I had.  The diameter of the inner part of the pulley was 30mm while the original was 27.5 and the original also was slightly tapered.  And maybe the pulley wasn't properly balanced.  I called the supplier of the new motor and he said that yes, it was a known issue and that a pulley had to be perfect.  He sold me a "good" pulley and when I got it and installed, it was perfect.

So, if you have any issues after installing, suspect the quality of the pulley first, before getting a new motor. 

What a great reveal! Thanks for exploring and exposing this hidden issue. We have a member troubleshooting this very same problem in another thread. The diameters may be different on different motor makes and models and different pulleys from different suppliers. I guess it would be smart to have a package of thin shim material on hand when swapping out pulleys.