Tim
Posted a lot
Posts: 3,340
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Hey up
looking into making a modification to my bike (wont say what at mo in case it isnt viable) - ok i said anyway :-)
Can anyone take a measurement for me (no rush) - i'm going to measure myself but would be great to have a seperate figure to verify against and make sure its right.
Can anyone tell me how much cable a 9spd shifter will pull across its range - I.e. starting in first gear, how many mm of movement is there in the cable up to 9th gear.
Cant find any official documentation telling me this.
Thanks a lot!
Tim
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Last Edit: Aug 5, 2008 14:07:12 GMT by Tim
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what make of shifter will you be using? because sram and shimano work differently. i have a pair of 08 XT shifters downstairs i can quite easily measure the difference for you
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Tim
Posted a lot
Posts: 3,340
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shimano, as sram pull twice as much making my idea less viable :-)
forgot to state that! good point
Thanks!
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Last Edit: Aug 5, 2008 10:00:32 GMT by Tim
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right measuring through my rear mech from a common point at the end of the barrel adjuster i had 45mm of cable in 9th gear, changing down into first i got to 25mm of cable making the cable travel 20mm. i did it 3 times to make sure as the second measure ment i got some mad figure ;D
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Tim
Posted a lot
Posts: 3,340
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25mm of cable pull, thats a bit less than I envisaged, which is good
thanks a lot mate!
i've got a set at home I can do on the desk to double check but thats a great ball park figure to start with
right, now i need to source/knock together some small hydraulic rams/pistons that have at least 25mm of movement - not gonna be easy
you've probably guessed what i'm doing :-)
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Last Edit: Aug 5, 2008 10:17:42 GMT by Tim
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A line lock for off road burnouts?   |
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 it doesn't matter if it's a Morris Marina or a Toyota Celica - it's what you do with it that counts  |
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Tim
Posted a lot
Posts: 3,340
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haha, got one of them already :-) <engage arnie voice> it is called my legs <disengage arnie voice> I've had a hard-google and cant see anything that would have any small pistons - long and thin, kind of like the lego technics pneumatic ones, but hydraulic and not made of plastic :-)  |
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Last Edit: Aug 5, 2008 10:34:56 GMT by Tim
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Tim
Posted a lot
Posts: 3,340
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haha, i dunno, i have absolutely no idea what your doing at all.
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Tim
Posted a lot
Posts: 3,340
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cable actuted hydraulic shifter - short straight cable run to a piston, then I can route a hose wherever I want, then mount the opposing piston on the dropout, connected to a piece of cable which actuates the mech - no need to modify the shifter or mech
no idea if it would work, no real reason why not as long as both pistons are exactly the same - then they should both move the same amount - the same as the cable - e.g. 2.5mm per shift
just for a bit of fun :-)
might be able to modify a pair of magura HS33 levers if they have enough piston movement
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Last Edit: Aug 5, 2008 14:07:51 GMT by Tim
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i think shimano did something like this aaaages ago. i've seen a picture of it I'm sure it was pneumatic tho?
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This'll be the bad boy you are on about. Didn't really take off though. Shimano Airline System.  |
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Tim
Posted a lot
Posts: 3,340
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Shimano Airlines, used in prototype for for downhill but not brilliant, heavy and limited amount of shifts, but supposedly super-precise and fast
had to use compressed air to force the mech across the block, so limited
mine, if i can find a set of pistons to mock it up, should be bulletproof :-)
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At first I thought you were making a chopper style top tube shifter. Then when I saw the hydraulic pistons I thought you were building a computer controled automatic gear shifting system.  I think that Shimano are bringing out an electronic gear shifting system. Mavic used to have one. What about using motor bike brake parts. Maybe the rear brake master cylinder would be good. Also some mechs have a rollamajig on the rear part. Maybe get one and fit the piston on where the rollamajig was |
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Last Edit: Aug 5, 2008 17:08:27 GMT by alecw35
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Tim
Posted a lot
Posts: 3,340
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At first I thought you were making a chopper style top tube shifter. Then when I saw the hydraulic pistons I thought you were building a computer controled automatic gear shifting system. I think that Shimano are bringing out an electronic gear shifting system. Mavic used to have one. What about using motor bike brake parts. Maybe the rear brake master cylinder would be good. Also some mechs have a rollamajig on the rear part. Maybe get one and fit the piston on where the rollamajig was Shimano are testing electronic shifting on the top of the range road groups, as are campag i think there has been elec nexus for a while for city bikes I may have to do somethign with a top tube mounted shifter anyway as my chopper needs restoring :-) |
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rysz
Club Retro Rides Member
Posts: 2,558
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IIRC, the tension spring that rear mechs use is pretty hefty and you will need a pretty solid ram in there to shift the mech over!
Maybe steam enthusiasts who make the scale models of steam engines might be able to help?
Rysz.
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Tim
Posted a lot
Posts: 3,340
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IIRC, the tension spring that rear mechs use is pretty hefty and you will need a pretty solid ram in there to shift the mech over! Maybe steam enthusiasts who make the scale models of steam engines might be able to help? Rysz. If a cable can pull it, the piston should fine, as its being actuated by the cable in the first place, no? thats a good idea on the steam enthusiasts side of things |
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rysz
Club Retro Rides Member
Posts: 2,558
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If a cable can pull it, the piston should fine, as its being actuated by the cable in the first place, no? thats a good idea on the steam enthusiasts side of things It is quite a long cable though which will give you a lot of mechanical advantage that you will not have with a hydraulic system? Or am I confusing myself? Rysz. |
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Tim
Posted a lot
Posts: 3,340
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If a cable can pull it, the piston should fine, as its being actuated by the cable in the first place, no? thats a good idea on the steam enthusiasts side of things It is quite a long cable though which will give you a lot of mechanical advantage that you will not have with a hydraulic system? Or am I confusing myself? Rysz. Confusing yourself i think :-) i think anyway - shifter pulls standard cable, cable pulls piston mounted on bar, piston mounted on seatstay moves, pulling a cable which actuates a rear mech, as normal :-) |
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