Sewing machine RPM reduction

[DAN_IN_MN]

I put this in the POTD thread but wanted to share it in my own thread.

Corrected a buying error that happened over 50 years ago.

My dad did furniture upholstery. When he bought his sewing machine, he ordered the largest/fastest motor he could get which is around 3500+ RPMs. The machine was way too fast and my dad did fit a larger driven pulley years ago. Original pulley on the left.



I still find it too fast as the clutch still has to be feathered, so this is my solution. Found this very ugly but usable pulley in my stuff. Had to modify the hub. A bolt lost it's identity in the process. I'll clean it up and paint it if I like how this turns out. Not seen are two 1/4-20 set screws drilled in the hex head to hold it on the shaft.

With this view, you can see the amount the hub had to be changed to fit the machines shaft. The original hub had small splines and I just pressed the bushing in.


Belt redirect roller added. Those used timing belt tensioners do come in handy. The belt would rub on the slot in the table without this added roller as you can see in the second pic. The mounting bracket for it was from a lawn mower muffler mount. Cut, drill, and tap and it was done.

Now to find the correct belt length and get a new one.

 

[DAN_IN_MN]

I went to an online belt calculator and it looks like I'll be needed a 47" belt. Along with finding the belt length, I found an RPM calculator.

Here are the difference in RPMs with the pulley changes.

Driver pulley 1.5" with:

OEM pulley of 3" = 1456 rpm (Watch for those fingers!)

Pulley dad put on 5" = 875 rpm (A lot slower but still watch for those fingers!)

Pulley I added 7.25" = 602 rpm (To be determined!) I might be able to keep the clutch engaged.

I might be able to control this beast now.