V-Belt Alternatives -> PU Round Belt

[Constabulary]

This for sure is not new but I think not much known so I thought I show what I did.

Since I´m fiddling with my vintage Singer a lot and have added several different type speed reducers to different machines I always hated that I do not have the right left V-Belt on hand. Of course in some cases you can adjust the SR or the motor angle but still annoying IMO. I have used round leather belt in some cases (meant temporarily) but they stretch with the time and you have to shorten them. I also had issued finding the right length especially for the machines with higher post (see below).

Long story short - I ordered some round PU belt with rough surface for testing and so far I´m quite pleased with them.

This is what I have ordered (cheapest I could find for testing)

https://www.ebay.com/itm/PU-Polyurethan-Rundriemen-mit-rauer-Oberflache-fur-die-Antriebsubertragun-PLA/312661290102

I have ordered 9mm / 5meter.

I haven´t yet tested the belts on my "heavy machines" / heavy materials that require a certain punching power on some projects. ATM I only have set up the 51w post bed and 108w binding machines with the round PU belts but I´m very pleased. Both rather light / medium duty machines but both machines appear to run a bit smoother. I cannot explain it technically but they overall just appear to run smoother. Just to have it mentioned - other that industrial V-Belts the PU belts are a little bit stretchy but not too bad. So I´m not sure (yet) how well they work with "heavy Duty" machines with heavy / thick / dense materials.

Optically black V-belts are nicer IMO but technically I´m quite pleased with the green round belts. Nice thing on the PU belts you can easily shorten them, melt the end (flame, soldering iron, heating iron....) and put them back together if the belt it a bit too long / need more tesnion.

Some pictures:

 

Edited April 9, 2021 by Constabulary

[DrmCa]

My Bonis runs on round leather belt with an S hook. I can make either of them whenever I need.

[JJN]

I have been using PU belts for a while now. I found a large roll (50 feet) cheap on ebay to try it out. Very handy to be able to set up a machine without having to run to the auto parts store and hope you measured right and they have my size in stock. it is a little stretchy because it doesn't have the cloth belting like v-belts, but grips well for me once I get the tension right. It is easy to melt together and never had had a connection break.

[Emery]

Any tips for someone to do this... I recently bought a machine and the current 10mil V belt twists for about 6 inches AND only at the guard end at top.  Spoke with the mechanic who serviced it prior to me buying.  He didn't want to take any responsibility as machine worked fine.  I asked a few more questions over the phone. 

He put the new belt on and admits the belt is the wrong thickness but he realigned the servo motor that someone else put on the table for the machine (Global SR 9929).  Told me it should be a leather belt but they don't work with servo motors and it should be an 8 mil belt.  He said he didn't run the machine for long when he did service it but he fixed the noise.  I asked what the noise was, and it was the belt hitting the guard at the top.   He claims he will send me the correct sized belt & then adjust the motor underneath (which I don't get from his explanation over the phone). 

I chatted with a colleague in Canada (who said this was the best decision they made to switch, have not had problem with belts since and rare to replace) who does the same work and uses similar machines and told me about these belt you melt.  Found out what and then found the thread in group. 

I want to switch to the PU belt, from needing I need to go with rough (green) vs smooth (red).  Just not sure if I need 6mil or 8mil.

And how do I best measure the size I need, do I mirror off the existing belt when I take it off?  

[Quade]

When you buy the PU belt it's one long piece, longer than you need, so, you can wrap it around the pulleys and line it up that way to get the length. Then cut and join. 

You could cut the old belt and measure it.  

I'm using a 3/8" automotive belt on one of my machines. Picked it up at the autoparts store.   I believe it's a 3L.  Each L of a belt size seems to be 1/8" which is a little over 3mm per L.  So 3/8" is 9.5 mm. 

[Quade]

I meant 3L = 9.5mm

[Emery]

6 hours ago, Quade said:

When you buy the PU belt it's one long piece, longer than you need, so, you can wrap it around the pulleys and line it up that way to get the length. Then cut and join. 

You could cut the old belt and measure it.  

I'm using a 3/8" automotive belt on one of my machines. Picked it up at the autoparts store.   I believe it's a 3L.  Each L of a belt size seems to be 1/8" which is a little over 3mm per L.  So 3/8" is 9.5 mm. 

Belts are Greek to me, I replace like for like in past. Add in I'm UK based vs NA.  I have a bunch of numbers and letters on the belt. I only plan to buy a meter of 6mil and 7mil PU. As I have read 8 is too big. 

1190/Z 46

114

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Matched Set

CEB0561

Edited March 28, 2023 by Emery
Error in belt size

[Quade]

PU isn't very flexible. So if you have small pulleys, smaller diameter is probably better.  I bought a couple different diameters but my pulley was simply too small to use them. Instead I picked up a 2L conventional belt which is about 6 mm.  My setup is unusual. I don't expect you'll have the problems I had.  I was trying to mate a "Sailrite Worker-B" motor to one of my machines.