Building a Speed Reducer

[RWL2]

For those contemplating building their own speed reducer.  I used  1-1/4" x 1-1/4" angle iron from a bed frame since I had it available.  Old bed rails are frequently given away, so it's a good source of material.  There's no reason that you couldn't make one with a wooden frame though.

I had a selection of pulleys ranging from about 1.5" to 8" that I'd saved over the years.  I also had three pairs of pillow blocks accumulated over the years.  All were sleeve bushing ones.  If I were buying, I'd probably choose one with ball bearings.  I don't know if they make non-aligning pillow blocks, but if you have a choice, choose the self aligning pillow blocks otherwise you'll spend lots of time getting the alignment just so.  I chose to use the pair of pillow blocks taking a 1/2" shaft since I had some 1/2" steel around and I only had to put a reducer bushing in the large 8" pulley.  The speed reduction is calculated from the ratio of the pulley diameters, so the first reduction was from a roughly 2" pulley to an 8" pulley or a 1/4 reduction of the 1725 rpm motor.

I turned the table upside down for convenience in working and laid out the frame around the existing holes for the bolts from the clutch motor, measured the size pieces I needed and cut them on the chop saw.

I welded those pieces together next.  Clamping the frame to the table kept the frame from warping when the weld cooled.

Next was a mock up of the frame with shaft and pulleys attached to see what height to make the upright pieces.  Note that I had the pillow blocks elevated enough to allow some room between the large pulley and table top to permit sliding the belt in.  I chose to make mine 9" in height so it exceeded the size of the pulley.  In retrospect, there was enough space between the center of the motor shaft and the large pulley that I could have reduced this size to 6 or 7 inches.

I cut out the uprights and bolted the whole frame together, then sat the motor on top to be sure this was all going to fit.  As anticipated, the clearance to the horizontal piece of the table frame was tight.  I had to keep the motor more toward the front of the table than it had originally been mounted because of this support.

 

I inset the top piece / motor side piece of plywood into the reducer frame and added the angle iron shelf for the pillow blocks and bolted everything together, discovering that the large pulley was now going to extend farther from the frame of the speed reducer than I had expected.  This was caused by the location of the pillow block.  I thought about welding a piece onto the shelf for the front pillow block, but decided it was easier to just move the whole frame back a little.  In order to accomplish this, I reduced the length of the plywood base (the part against the table) and decided to use lag screws rather than the original bolts and bolt holes from the motor.  This allowed the frame to slide back and forth under the plywood "clamp".  When making the uprights I drilled three sets of holes for the pillow block shelf.  This will - at least in theory - allow for some tension adjustment of the belt from the speed reducer to the machine's handwheel pulley.  The tension from the motor to the large pulley is adjusted with the tension adjustment screw on the motor mount that's part of the clutch motor.  I paid minimal attention to the lengths of belts required and this could have been a fatal flaw if I couldn't have found the right length belt from the reducer to the machine since there is very little adjustment built into my frame for that.

I put the newly painted frame on the table, moved it to an appropriate position and tightened the lag screws.

Next it was time to mount the motor.  There had been some trial fittings for the location of the motor on the frame before I drilled the holes and mounted it.  The motor was moved back and forth a little so that the two pulleys were in relatively close alignment by eyeball.

 

With the motor securely in place it was time to flip the table right side up and see how it all looked.  

Then put the machine head into the table opening and aligned the small pulley of the speed reducer with the one on the handwheel.  At this point I took a piece of rope and measured the lengths of belt required.  Both belts needed to be about 36" in length.

 

As luck would have it, I had found an 8 ft length of leather belt at a yard sale the week before so I made my own belts in order to be sure these sizes would work.  An advantage of the leather belt is that as it stretches I can just remove the staple and shorten the belt to a new length.  I made my own staples.  16 Ga wire worked better than 14 Ga wire for the staples.  There is play in the speed reducer shaft causing it to be noisy - but I can control the speed of the sewing now.  It is not as slow as I've seen in some videos of machines with servo motors.  I cannot stop the needle in the up or down position as I've seen people do in videos of slow servo motors, but that might come with practice.  Despite the 1/4 reduction from the motor to the 8" pulley and an uncalculated reduction from the small pulley to the machine's handwheel pulley, I'm getting 424 rpm on the sewing machine shaft,  i.e. 424 stitches per minute.  I would have thought it would have been lower than that.  Regardless, it's a major improvement.

 

 

Edited October 13, 2020 by RWL2

[Pintodeluxe]

Your pulley sizes look good to me.  Maybe the lack of surgical control is just because it's a clutch motor.  I've sure enjoyed my box style speed reducer.  I started with a conventional reducer, and couldn't tip the head back to oil underneath (had to get a wrench out).  Now with the box style reducer, I forget it's down there.  Works great.

This week I'm making an under-table hook to hold a roll of cording.  Came home from the hardware store with a bunch of iron pipe fittings.  It's fun to mod your tools just the way you need them.  

[RWL2]

10 hours ago, Pintodeluxe said:

This week I'm making an under-table hook to hold a roll of cording.  Came home from the hardware store with a bunch of iron pipe fittings.  It's fun to mod your tools just the way you need them.  

Post pictures when you have it done.  It was through pictures of other's speed reducers that I got my concept for how to make my own.  Pictures of what people do or make are helpful.

[Ken Nelson]

If you pick up the needle end of a table machine, you release the tension of the belt and can slip it right off using a standard speed reducer.  The box speed reducers are nice though.

Edited October 13, 2020 by Ken Nelson

[CowboyBob]

Looks good & at 4-1 that should work real slow esp if you ever get a servo motor.

[sandmanred]

I'm facing the same challenge of speed control on a clutch motor.  In asking around someone suggested greasing the cork on the clutch.  I was reluctant to try it because it's not easy to undo but I went ahead anyways.  I polished the metal face of the clutch and put a light coat of grease on cork and it does help get a bit more control. 

The other thing that help is to modify the linkage from the foot pedal to the clutch motor.  Either extend the lever on the clutch motor or shorten the foot lever throw.  Looking at your pics a new hook on the foot pedal about half way between the axle and the existing rod that connects to the clutch lever would be a good start. This shortens the throw at the clutch to give a bit better control as well.

[RWL2]

1 hour ago, sandmanred said:

The other thing that help is to modify the linkage from the foot pedal to the clutch motor.  Either extend the lever on the clutch motor or shorten the foot lever throw.  Looking at your pics a new hook on the foot pedal about half way between the axle and the existing rod that connects to the clutch lever would be a good start. This shortens the throw at the clutch to give a bit better control as well.

I can understand making an extension to the clutch lever, but I'm not sure what you're describing for the foot pedal.  After adding the speed reducer, the connecting rods would have been so short that it seemed better  to bend a piece of metal and make a link rather than permanently shortening the rods until I saw how this was going to work.  Do you have a photo of yours illustrating a modification to the foot pedal?

[sandmanred]

38 minutes ago, RWL2 said:

I can understand making an extension to the clutch lever, but I'm not sure what you're describing for the foot pedal.  After adding the speed reducer, the connecting rods would have been so short that it seemed better  to bend a piece of metal and make a link rather than permanently shortening the rods until I saw how this was going to work.  Do you have a photo of yours illustrating a modification to the foot pedal?

Here's a picture of what I meant.  You can see the original point the connecting rod attached on the right.  And you can see the blank hole to the right of the current attachment point, I tried it but it was too short. You can see ended up about midway between the original point and the axle.  My connecting rod is adjustable in length so easy to adjust to accommodate the connection point changes. 

Edited October 19, 2020 by sandmanred

[RWL2]

A picture is worth 1000 words.  That does look like a good method to increase the sensitivity of the clutch to foot pedal position.

[Firestar1485]

FYI.  You can also replace the pulley on your sewing head with a larger diameter!

On my Juki LU562, I choose not to build a reducer but instead (1) replaced old clutch with servo motor (pretty cheap online $100 and manually adjustable down to 320 rpm), (2) replaced stock motor pulley with smallest I could find ($10-15 at hardware store), and replaced machine head pulley with largest I could find ($20-30).   Switching from clutch to servo ($100) + switching out pulley sizes ($50 w/belt) made a big difference; guessing I got it down to 200 spm or less.

PS  I also added a manual handle to the pulley on the machine head for manual use for extreme slow and punching strength. I eventually sold the LU562 because it did not have reverse and the bobbin was undersized for my liking.  Now I'm looking at a JUKI DNU-241H, larger bobbin, easier to find prewound bobbins by the gross, etc.