Direct Drive Servo Motor retrofit for vintage singer 491D

[DonInReno]

5 hours ago, JClif88 said:

Yes, this is a concern, I don't actually do lots of leather work so probably don't need a super slow speed but do want to work at a slower speed, I'm not sure how slow these motors can be tweaked to go and I'm hoping a bit of practice should be all that's required when it's tweaked right down

I do like how compact they are - as long as you aren’t expecting it to sew slower than other generic servo motors it seems interesting.

I was curious how these super compact servos attach and found a photo from a different servo that seems to show one as it comes out of the box.   On one end of the stator (spinny thing) there’s a bearing in the servo’s housing, but there isn’t a bearing on the other end - so I’m assuming the bearing supporting the machine handwheel serves as the output bearing of the motor.   The adaptor plate and shaft connector you will need to make up will probably have to be quite exact.

[dikman]

"spinny thing"......

 

[JClif88]

On 11/18/2020 at 2:22 PM, DonInReno said:

I do like how compact they are - as long as you aren’t expecting it to sew slower than other generic servo motors it seems interesting.

I was curious how these super compact servos attach and found a photo from a different servo that seems to show one as it comes out of the box.   On one end of the stator (spinny thing) there’s a bearing in the servo’s housing, but there isn’t a bearing on the other end - so I’m assuming the bearing supporting the machine handwheel serves as the output bearing of the motor.   The adaptor plate and shaft connector you will need to make up will probably have to be quite exact.

The pictured unit looks like the ones they sell for Overlockers, but I suspect they are the same internally.

I've not actually used a servo motor yet but I'm hoping, bringing the speed down as far as possible on the control unit (around 400-500 RPM) should give me a usable range.

I contacted a US supplier about the Yuma motors and they've stated they have fitted them on to a Singer 591 so the shank on my 491 should be suitable, I just need a way of stabilising the motor which will require drilling and tapping my machine or fabricating some other mounting system.

It also seems that they supply converters with the units to adapt the servo to many common shank sizes (I think mine is 14.7mm)

I'm also interested in whether I can modify the controller to have better speed control via the optical sensor as shown on this forum which would be great.

[dikman]

13 hours ago, JClif88 said:

I'm also interested in whether I can modify the controller to have better speed control via the optical sensor as shown on this forum which would be great.

IF it uses an optical sensor. It appears that most, if not all, of the generic servos use Hall-effect sensors, not optical now.

[DonInReno]

I’ve also tried some things not all that traditional, and while tried and true is almost always the way to go, sometimes it’s worth it just fast a learning exercise.    I also like a more compact form factor, but there is no way I’d go without a 3:1 reducer.

My preferred setup so far is a planetary reducer directly coupled to the motor and one short belt.  I’ll bet eventually a company will offer a servo mated to a planetary reducer.

[dikman]

That's neat, Don. I would imagine the only reason it hasn't been offered is cost? Plus, of course the bog standard servo is a straight swap for either a clutch or another servo motor, no messing around.

[Constabulary]

For a while I have been playing with the idea of an NEMA planetary gearboxes like this:

https://www.ebay.de/itm/Planetengetriebe-Drehzahlminderer-Nema17-23-34-Getriebekopf-3-5-8-20-30-40-50-1/264861653607

But when putting approx 120€ for a 1:3  planetary gearboxes + tinkering in relation to a DIY Speed reducer the DIY version was the winner.

 

Edited November 21, 2020 by Constabulary

[dikman]

Another advantage of a home-made reducer is you can tinker with the ratios by changing pulley sizes.

[DonInReno]

12 hours ago, Constabulary said:

For a while I have been playing with the idea of an NEMA planetary gearboxes like this:

https://www.ebay.de/itm/Planetengetriebe-Drehzahlminderer-Nema17-23-34-Getriebekopf-3-5-8-20-30-40-50-1/264861653607

But when putting approx 120€ for a 1:3  planetary gearboxes + tinkering in relation to a DIY Speed reducer the DIY version was the winner.

 

If a sewing servo had a NEMA nose so it would simply bolt up to a NEMA reducer it would be much easier! Lol

My current project is a Wittgenstein Alpha 3:1 reducer off eBay and SP-1100 servo from Keystone Sewing.  It seems these reducers are available in a huge range of input and output sizes, as well as base adaptor measurements, both metric and inch.   This one is 5/8” input, 7/8” output, with 70mm x 70mm holes in the base.  The servo hasn’t made it here yet, but an adapter plate between the two will need to be made, or at least new holes drilled in the reducer base.

Other than the compact size there is no noticeable benefit over using a 3:1 pulley reducer.    

[JClif88]

13 hours ago, DonInReno said:

If a sewing servo had a NEMA nose so it would simply bolt up to a NEMA reducer it would be much easier! Lol

My current project is a Wittgenstein Alpha 3:1 reducer off eBay and SP-1100 servo from Keystone Sewing.  It seems these reducers are available in a huge range of input and output sizes, as well as base adaptor measurements, both metric and inch.   This one is 5/8” input, 7/8” output, with 70mm x 70mm holes in the base.  The servo hasn’t made it here yet, but an adapter plate between the two will need to be made, or at least new holes drilled in the reducer base.

Other than the compact size there is no noticeable benefit over using a 3:1 pulley reducer.    

This is really interesting, so in theory, could a planetary gearbox reducer be found to link a servo motor directly to the shaft?

It's good to know if I find the direct drive motor too fast, I might be able to use a planetary gearbox reducer to slow it down.....