Questions re: DIY box style speed reducer

[AlZilla]

@Constabulary, I never thought of stapling a V-belt. But, why not ... we do it all the time with leather belts. Especially living where parts aren't plentiful and easy to find, this is a great idea.  Next time I see them on sale/clearance cheap, I'll stock up.

[Constabulary]

Back then I had no proper size V belt for the test setup. But yes, it actually works.

[fibersport]

Thanks Constabulary, extremely helpful!  In my mind I kept trying to find a 150mm pulley without much luck, never thought to just change the size of the smaller one as well.  I'll be placing my orders tonight!

Edited July 15, 2023 by fibersport
spelling error

[Constabulary]

You are welcome BTW - toothed V-belts are better when you go around small size pulleys.

[fibersport]

Parts all on order, now to just try and be patient for them to arrive.  Agreed on the belt also.

[shelr1]

fibersport sorry I just now saw your question.

I got most of my parts on Amazon

When I was researching I determined that shaft size is the key decision, mainly due to availability of pulleys with the correct diameter and bore size, and bore size of the pillow block bearings. I used 1/2 Inch shaft size. 15mm and 5/8" are other common choices.

6" Dia. Pulley Congress 1/2" bore

1.75" Dia. Pulley Terre Products 1/2" bore

1/2" bore Jeremey pillow block bearings

I sourced the shaft locally. 

The belts are size 3L,  3/8"wide, they are listed for automotive applications and work perfectly for sewing machines. There are lots of lengths available on Amazon. I needed a 46" and a 24".

I built the support frame from stuff I had laying around my shop.

Note: 3L belts will work on a 4L pulley, it will change your ratio slightly as it sits slightly lower in the pulley.

If I recall correctly I have about a 3.5 to 1 reduction.

[fibersport]

No problem.  I ordered my parts from ebay, they're coming in on a slow boat from China as they say so I'll have to be patient.

One other question:  is your reducer mounted on a hinge or something?  It looks like there is a pivot towards the outside of your frame.

Edited July 18, 2023 by fibersport

[shelr1]

fibersport, I used a bunch of stuff I had on hand to make the frame. I was trying to make it adjustable for belt tension, I found brackets for the ends that act like a hinge, but when I got the belts on simply moving the entire assembly up and down worked fine, and I fine tuned the short belt with the motor adjustment.  In retrospect it didn't need to pivot but it worked well.

The picture shows one of the end brackets, it attaches to the end of the table legs vertically. I'm not sure what the bracket was intended for maybe a garage door roller bracket.

[fibersport]

I really like your design, it has given me some great ideas for making mine.  I'll be sure to post some pictures when I get it done.  Thank you (and everyone else on this thread) for your inspiration!

[fibersport]

Here are a couple of pictures of my version of a speed reducer using information from this thread - thanks to all!  Pulley sizes are 120 and 40 mm with a 15 mm bore.  I welded up a U shaped frame out of 1-1/4" angle.  The frame pivots on the leg of my table and is tucked in so it's out of the way.  A spring keeps tension on the belts.  The motor mount is used to fine tune the belt tension on the belt between the motor and large pulley on the reducer.  Belt selection is kind of critical, I used a belt length calculator to pick my belts which worked well.  I would like to slow it down a little further as the lowest speed of my servo motor is a little too fast for my liking although I need to do some sewing to see if I can adapt to the slowest speed.  My options are a larger diameter large pulley, a larger balance pulley on the machine or a servo motor controller that has a lower intial speed.  Overall I'm very satisfied with it and really like the simple design.  I ran it without the spring and it worked OK until I tried to sew 4 layers of vinyl which cases the small pulley on the speed reducer to slip.   Adding the spring worked great, it actually rises up a bit on startup but there is no slippage on multiple layers of vinyl.  I don't have much tension on the spring, if it did start to slip all I would do is pull it down a little more.  I do need to cut the shaft down and paint the frame but until I spend a little more time with it I'll call it almost done!

 

Edited August 10, 2023 by fibersport
add pictures delete multiple post