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jrwhalley

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Reply with quote  #1 
Having had occasions to search for obscure or non-existent bobbin winder tires and/or drive belts on vintage or otherwise orphaned sewing machines I have gotten lucky searching through industrial o-ring catalogs from Parker and other companies. For sewing machines, the two material choices that I have found are most suitable and cost effective have been NBR (nitrile butadiene) or occasionally silicone, which is much softer and less durable, but can be used to advantage on some friction drive wheels. Imperial sized pieces seem to have fewer choices in terms of cross section and generally are in 1/16" steps, but there is usually a greater variety  when you look at the metric sized range which is available in 1mm, and .5mm steps in some sizes.

For example, the last couple of machines I have been able to substitute an o-ring for a non-existent bobbin tire were a Gritzner High-Arm where a Parker 6mm x 28mm I.D. replaced the original (Mc Master Carr p/n 1302N443, under $9 for a pack of 5), and the first Singer 101 we bought, which used a (factory serviced only) bobbin winder with a synthetic leather wheel with a Parker 6mm x 24mm (MMC p/n 1302N436, $6.20 for a pack of 10). As you can see, the pricing is not exorbitant, and it can get you out of a bind for that part made of unobtanium. For most of the Singers and Vintage White sewing machines, their sheer ubiquity makes locating spares a painless proposition, but for others it can be The Great Snark Hunt. Keep in mind that there are "square-section" o-rings as well which can be used to repair the bobbin winders on some of the European and Japanese machines from the 60s and 70s, but the listings are less generic and generally sparser. As with everything else, YMMV.

I've attached a couple of sizing charts for folks convenience, but the Parker-Hannefin website has pretty much any related technical document you could imagine.

 
Attached Files
pdf PAI Standard O-Ring Dimensions & Illustrations.pdf (1.63 MB, 6 views)
pdf Parker oring 2008 ORD 5712.pdf (974.07 KB, 4 views)

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Zorba

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Reply with quote  #2 
I used a buna O-ring as a belt once with less than satisfactory results, and have seen them used as winder tires on occasion.
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Farmer John

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Reply with quote  #3 
IIRC, standard 0 rings are around 70 Durometer, which is quite stiff.  They don't like to bend around small diameter pulleys, as it takes a lot of power to do so..  When I had a batch of 40 Durometer 0 rings made up for the Elna grasshopper drive belt, I ran into very stiff opposition on the Elna site.  I even offered a free belt to the detractors, who all declined, as it would negate their position on the issue. 
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Zorba

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Reply with quote  #4 
Probably a buna O-ring.
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Farmer John

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Reply with quote  #5 
Bruce, how does the softness and flexibility of the hardware store o ring belt compare to the original Elna belt.  I think that my Grasshopper has a transparent or amber belt.  Is that likely to be an original ?
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Zorba

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Reply with quote  #6 
The time I used a Buna O-ring as a belt, it didn't work too well as that particular situation because that really needed a V-belt for clearance reasons. Otherwise, I pretty much agree with JonesHand52, although I have zero idea as to long term longevity. The O-ring was less stretchy than than the round belts I've seen as I recall.
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jrwhalley

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Reply with quote  #7 
I'm a bit more of a pragmatist about this. I've seen everything from old shoelaces to clothesline used to replace the leather belts on treadle machines, and new leather belting is readily available along with the proper belting pliers to do a factory OEM quality replacement for relatively short money. (Typically around $30 for a good set of pliers and $20-30 for lifetime supply of leather belt)

A couple of bucks to replace a non-existent drive belt or bobbin tire when the alternative is having an oversized paperweight or doorstop seems like a great deal. If a "real", factory belt is available at less than blood-letting prices, it usually is the superior option, but 95+% of what I've seen lately is generic Chinese replacement parts and I'm willing to bet that the Shore numbers on those parts are all over the place. If the durometer of a neoprene/buna-n/NBR o-ring is too high to handle a tight radius, try the silicone version instead. Worst that I could foresee is an earlier failure, and being out a couple of bucks. And it beats using rubber bands.

-Jim W
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Farmer John

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Reply with quote  #8 
Bruce, speaking only of the Elna Grasshopper, I did exactly as you suggested, years ago.....I got a hardware store 0 ring for the Elna.  I found it lacking in stretch and flexibility, as the Grasshopper has no belt tension adjustment, and a low powered motor.   Thus a soft Buna N composition was selected to match the qualities of the original belt.  I am sorry that you disdain civil conversation and scientific research.  From me, you will hear not another word on the subject.
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JonesHand52

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Reply with quote  #9 
John, I do not disdain civil conversation and scientific research. If I hurt your feelings, I'm sorry. I'm sure you will find a safe space somewhere. I just think that all the naysaying is a bit over the top when all it takes is a couple of bucks and a trip to Ace Hardware to get one and try it out. By all means pay 20 bucks for a genuine amber belt for the Grasshopper, but in the meantime a usable replacement is available. My Grasshopper clone runs just fine with one. Perhaps I should delete my entries. 

Update: My entries are gone. Forget about the O-rings. 

-Bruce
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Cari-in-Oly

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Reply with quote  #10 
Only 3 days til the full moon and it's showing............

Cari

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Zorba

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Reply with quote  #11 
And its not even a Mercury Retrograde...
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PatriciaPf

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Reply with quote  #12 
Quote:
Originally Posted by JonesHand52


Update: My entries are gone. Forget about the O-rings. 

-Bruce


Well, that's too bad.  I have an Elna Grasshopper and would have liked to read what you wrote regarding O-rings.  
Patty

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