Chain link length

[geekybiker]

I recently got a SA IGH in the mail, it came with a 22t sprocket, which is way too high for what I need. However I was out in the garage testing a length of 7spd chain on sprocket. the chain is 1/2" length and (I assume) 3/32" The roller width was okay, but when I wrapped the chain around the sprocket it wouldn't fit after 4-5 links. (around 1/4 around it). I was under the impression that all normal bike chains had the same 1/2" length and just varied in width mainly. I just want to make sure I end up with the right sprockets. I don't want to order any more SA sprockets if they're using a different standard. My motor and chainring fit this chain just fine. Did the hub I get come with a weird sprocket, or is all SA stuff like this?

 

[Papa]

3/32" chain won't engage the 1/8" sprocket teeth completely, even though both are 1/2" pitch. So you have 3 choices:

1. Get a 3/32 sprocket ( http://www.sheldonbrown.com/harris/sturmey-archer-parts.html#sprockets )

2. If you are handy with a file, you can use a sprocket from a cassette - the ID is correct, but you'll need to reshape the 3 matching inner splines (and remove the remaining) on the sprocket.

3. Switch to an 1/8" wide BMX type chain.

 

[John in CR]

Papa,

I think you missed the easiest one with the file, which is to narrow up the teeth on the sprocket he has to make the 3/32 chain fit. I did that with a freewheel once, being careful that filings didn't enter the small space in the freewheel. That freewheel still works fine 2 years later. I did it because I still wanted to be able to use the 3 speeds available thru the triple chainring and front derailleur.

John

 

[Papa]

Papa,

I think you missed the easiest one with the file, which is to narrow up the teeth on the sprocket he has to make the 3/32 chain fit.

Quite true, John, but I intentionally mentioned sprocket replacement first because they're only 6-8 bucks, so why bother? Plus, he also indicated changing ratios.

http://aebike.com/product-list/shimano-b367/internally-geared-hub-parts-nexus-alfine-cogs-t991-m4903-qc30/

 

[John in CR]

Papa,

I think you missed the easiest one with the file, which is to narrow up the teeth on the sprocket he has to make the 3/32 chain fit.

Quite true, John, but I intentionally mentioned sprocket replacement first because they're only 6-8 bucks, so why bother? Plus, he also indicated changing ratios.

http://aebike.com/product-list/shimano-b367/internally-geared-hub-parts-nexus-alfine-cogs-t991-m4903-qc30/

Sorry, I forgot he didn't already have the right sprocket. If the SA's are like my Nexus sprockets, I'd think they'll be tough to fit using a cassette sprocket filing from the inside out to leave 3 teeth. Plus they're dished for some reason, and the metal is thicker too. A file may be tedious either way. A bench grinder and a stock SA sprocket is a few minute job, and he can test that method out first with the existing larger sprocket he has.

I needed more teeth on mine, so I went 2 routes. One I welded a chainring to the stock sprocket...Ugly but functional. The other, I started with a BMX chainring, turned it open with a lathe, and added the 3 points for the groves by welding and shaped them with a file...prettier but a lot more work. Those are for the motor chain, and I added a bolt on piece of a steel hub to get the threaded part to add a freewheel for the pedal chain.

John

 

[Papa]

Plus they're dished for some reason,

I use the 'dish' for adjusting the chain line.

Come to think of it, I have a few extra IG 3/32" cogs here somewhere. I asked for 8-speed SA cogs, and they sent 3-speed instead - different animal. They are 19t IIRC. So if the OP (or anyone else for that matter) can use one, I'll be tickled pink to send him one.