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PostPosted: Thu Apr 23, 2009 9:46 am 
Old School Grand Master
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Joined: Fri Oct 12, 2007 12:48 pm
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Location: Out here in the perimeter...
Do these offer any sideways movement or is it just up and down?

Wondering if it might work with two rings on back?

Neill


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PostPosted: Thu Apr 23, 2009 9:49 am 
Gold Trader / PoTM Winner / RB Rider
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Location: kent
I used to have one , and it is only up and down .

for two rings at the back you are better off using an old mech modified .


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PostPosted: Thu Apr 23, 2009 10:04 am 
retrobike rider
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Location: rutland
you could use an onone

just an allen key to move the jockey wheel and its sprung so itl take up the chain slack

ive seen a few trials riders using 2 sprockets at the back , the usual large tooth for trials and a smaller to get to where they want to ride quicker than walking pace . push the tensioner and move the chain over by hand then readjust the jockey wheel . they set them up so the chainline is best for the larger sprocket as they put more strain through it

there is a tooth ratio that keeps the chain under the same tension in 2 chainring/rear sprocket configurations . solves the chainline issue as its a matter of moving the chain further in or out while keeping it parallel

but it gets to the point where you have to start wondering if it would be better to just use a mech / shifter and range of sprockets


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PostPosted: Thu Apr 23, 2009 10:42 am 
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Joined: Wed Jun 13, 2007 11:10 am
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I'd tend to agree with the latter part of perry's comment. If you want some gears out back just use 7/8/9 and a mech and shifter. Getting off to change gear and make adjustments was left in the Alps by Mr. Campag. decades ago. SS or geared. Just get off the fence ;)


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PostPosted: Thu Apr 23, 2009 10:48 am 
Old School Grand Master
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Location: Out here in the perimeter...
mtbfix wrote:
Just get off the fence ;)


:lol: :lol: :lol:

I know, it was a theoretical solution to a practical problem.... 2:1 would be shite (=useless) where I regularly ride but ok on the road so I was only thinking...... :oops:


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PostPosted: Thu Apr 23, 2009 12:10 pm 
Retro Guru

Joined: Wed Jun 13, 2007 11:10 am
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Location: Reading way
Do a search for 'Hirondelle' bikes. You can run two sprockets at the back and a single chainring. Chain runs over the tops of both rear sprockets and returns on an idler mounted midway along the chainstay. This lets you run two gears, one driven by pedalling backwards. It is not aesthetically that pleasing but it serves a function. I dismantled mine so have no pics I am afraid.


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PostPosted: Thu Apr 23, 2009 10:14 pm 
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Joined: Sun Dec 14, 2008 2:11 pm
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Two sprockets? Sorry you've lost me. As soon as have two gears you may as well have three, and if you have three what's the problem with four? And before you know it you've got 27.

How about a Duomatic Torpedo? Now there's a two gear setup that's pretty cool with it.


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PostPosted: Thu Apr 23, 2009 11:14 pm 
98+ BoTM Winner / Gold Trader
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Joined: Wed Aug 15, 2007 7:29 pm
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Location: Netherlands
If you have some cash to burn White Industries do a double/double set-up in theuir ENO range. Two sprockets at the back and a double ring up front fitting the same chain with two ratio's : 35-38 and 16-19 so you run 35-19 or 38-16 with the same chain length, very nifty and nicely executed too

Image

The affordable solution is to just get the White double freewheel an make up the chainset from an old MTB triple.

Enjoy!!


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PostPosted: Thu Apr 23, 2009 11:50 pm 
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Location: hampshire
in answer to your original question, yes you can. as seen below the pulley is mounted on a spindle approx. 35mm long secured by a single allen bolt allowing a whole world of lateral adjustment.

Image


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