Adler 120 reduction, not Not Leather

[GPaudler]

Hi Sewers, thanks for your interest - this is how I slowed-down and torqued-up my 120-2 with a cameo by my 105-27.

I turned the huge hand wheel around to get it's v-belt groove closer to the machine so that the motor wouldn't have to be cantilevered too far. The first photo also shows the new bobbin-winder drive wheel which was in my pile for 20 years. I have no idea why I have it or what it's from. There's no reason to think it's for a sewing machine but it has just the right offset and is much nicer than the original plastic-hubbed Adler part.

The second photo shows how tight the fit is. The swing arm is 1/4"x 1-1/2" stainless steel. I like to mount the intermediate pulleys on a swing arm so that the belts' lengths are not critical.

The third photo shows the pulleys I turned out of aluminum, the smaller one is press-fit into the larger and has two bearings pressed-in; one each side. I try to use skate bearings whenever possible because they are common and inexpensive. If they can handle a 200lb knucklehead hucking massive air, they are up to this job. That's engineering.

As I mentioned, it's my policy to not make any irreversible changes to a machine, so the positions of existing holes somewhat dictate the design. The big pulley has a hole in it for the hex key to tighten the swing arm pivot bolt. On the 105, I pressed-in a sintered bronze bushing for the pivot shoulder bolt but that was unnecessary for a pivot that's rated for 0 RPE (Revolutions Per Ever)

The 120 has its big plinth with holes in opportune positions for the aluminum angle bracket on which I mounted the motor, controller and box of electronics. I milled vertical slots in the bracket to allow tensioning of the v-belts but one weakness of this design is that I have to remove the electronics box to loosen/tighten the motor bracket bolts.

The controller is mounted diagonally so that the arm doesn't stick to far out the back and it doesn't intrude on the clearance between the spine of the machine and the needle.

They are much more expensive than a regular rubber belt, but the twist-lock style belts allow me to vary the design as I go without a hundred trips to buy wrong-length belts. I like the twist-lock belts but they aren't too happy with small pulleys because they offer less contact area than solid rubber belts. I wipe contact cement or gasket dressing onto the contact surfaces, letting it dry before installing the belt, to make them a little stickier.

But that's just me, Gary

 

 

[GPaudler]

Here are the photos that fell off:

[Uwe]

Wow, that is seriously impressive work! There isn't a millimeter to spare anywhere near that reducer pulley. Thank you so much for taking the time to disassemble the parts and document your setup.

I had been contemplating mounting a "floating" reducer pulley on a swivel arm, but your solution is way simpler and more elegant than what was bouncing around in my head. I too have a bunch of skate bearings left over from previous projects - time to put them to work.

Now I have to figure out workholding for turning my own reducer pulleys. The small pulley seems straightforward enough,  but the big pulley stumps me. Is your lathe chuck simply big enough to hold the big pulley on the outside diameter to turn the center hole first? My experience on a lathe is limited and I know just enough to be dangerous and occasionally productive.

 

[GPaudler]

Thanks Uwe. I'll often drill and tap a hole in the center of a band-sawn blank and screw a bolt into it, then hold the bolt head in the three-jaw chuck. Be sure to not turn it backwards. In this case, I made the small pulley first and pressed it into a hole I bored in the big blank so I could hold the small pulley in the chuck. You could also hole-saw three holes, arrayed evenly around the center, each big enough to insert one chuck jaw. Or, if your chuck has removable jaws, remove them and bolt the pulley blank to the threaded holes that the jaws were screwed-to.

On the Adler 105, I started with an off-the-shelf die-cast pulley that had a small, cylindrical hub that was easy to hold.

How embarrassing! I just noticed that I wrote "to" where it should have been "too".

[GPaudler]

Oops, again. Here's the photo of the 105:

[Uwe]

I'll have to set aside some time to do some pulley trials on the lathe. Thanks for the workholding tips!