Singlespeed chain tension

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Regurgatron
Posts: 71
Joined: 28 Mar 2008, 12:37pm

Singlespeed chain tension

Postby Regurgatron » 27 Aug 2009, 9:54pm

Hello

I found an old Raleigh road bike in a skip. I converted it to singlespeed using a stripped down Shimano MTB drivetrain. The drivechain is nice and clean, but pretty worn.

The frame has semi-horizontal dropouts so I've provided tension by making the chain just long enough when the wheel's at the front of the dropout, then knocking it backwards as far as I can.

Everything was going fine for a couple of months, but now I throw the chain on every climb.

Do you reckon if I get some proper singlespeed cog + chainring I'll be alright (what with their massive tall teeth an' all)? Or do I need a tension device?

Goodbye

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DaveP
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Joined: 9 Mar 2007, 4:20pm
Location: W Mids

Re: Singlespeed chain tension

Postby DaveP » 27 Aug 2009, 10:56pm

Does the chain come off the sprocket or the chainwheel?
Sprockets originating from a cassette are designed to allow the chain to dismount easily. Theres no doubt that a singlespeed sprocket with full height teeth holds the chain more securely.
But. It was ok and now it isnt.
Could be an old chain that is now too worn, or it could be that the wheel is twisting in the drop outs under load. If the wheel has quick release fitted you might need to change the axle and use old fashioned nuts.
A chain tensioner might help if the chain tension varies a lot as the pedals are turned, but otherwise you should be able to get the transmission to work without it.
Trying to retain enough fitness to grow old disgracefully...

bensonboo
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Joined: 29 Jun 2009, 7:28pm

Re: Singlespeed chain tension

Postby bensonboo » 28 Aug 2009, 11:49am

I experimented with a dismantled cassette until I found a gear that would enable me to run without a tensioner (I have vertical dropouts so no adjustment possible) and did get some jumping. I also had a slightly slack chain until I bought a proper rear cog and new chain, no more jumping and much better tension.
I tried the On-one tensioner before changing the number of teeth but found it poorly made and it didn't help.
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djnotts
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Joined: 26 May 2008, 12:51pm
Location: Nottingham

Re: Singlespeed chain tension

Postby djnotts » 28 Aug 2009, 12:14pm

As long as the drop out slots allow for say 3/4" axle movement, then a tensioner will achieve nothing - unless possibly one or more of the cog/ring/chain are heavily worn!

And IMO/E Q/R should be fine.

Something needs replacing. Quite possibly EVERYthing!

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Regurgatron
Posts: 71
Joined: 28 Mar 2008, 12:37pm

Re: Singlespeed chain tension

Postby Regurgatron » 28 Aug 2009, 2:09pm

Thanks for the help.

I think there's something in the idea that the axle is twisting in the dropouts. But, on reflection, I think the whole system is just too worn. I was hoping to get away with just using junk out of the shed, but I'm going to go mad and invest in a dedicated SS cog and chain.

bensonboo: Man. Your set is, like, properly clean! You could eat your tea off it. Mine is slightly less bling:

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