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hydraulic gear change
hexxi - 3/5/13 at 07:06 AM

As it seems to be very difficult to route cables for gear shifting, I have have been starting to thing about a hydraulic gear shifting using some clutch slave- and master cylinders. Has anyone experience with this king setup?

40inches - 3/5/13 at 07:38 AM

I think hydraulic would be too slow. Google Kliktronic for electric version.

MikeRJ - 3/5/13 at 07:46 AM

Hydraulic gear change would be a pain IMO, imagine having to get the relative position of the gear lever correct to the gears by adding or removing tiny amounts of fluid.

hughpinder - 3/5/13 at 08:10 AM

Hydraulic should not be slow (welll at least to several thousand cycles per minute speed), or have we not heard of hydraulic tappets/ABS? The amount of movement at one end for a given movement at the other will depend on the ratio of cylinder areas. However people can cope pretty well with different lengths/throws of gear levers in different cars, so I don't suppose it will be a problem - especially if you use the same size cylinders mounted in the same relave positions at each end, so no effect on relative movement. I dont really know if the gear change would be stiff to operate though, and you may want to use larger hoses/retap cylinders to get more flow. I imagine you will have some fun setting up for and bleeding the system though. I'm guessing the only way to really find out is to get down to the scrappies and buy a couple of cylinders and some old hoses to try it with.
I'll be interested to hear how you get on.
Regards
Hugh

matt_gsxr - 3/5/13 at 10:12 AM

I don't see why it couldn't work, but would you not need a push pull system (i.e. 4 cylinders), in which case it all gets a bit complicated.

Matt

designer - 3/5/13 at 10:50 AM

As above, there is no reason it shouldn't work. But nobody has got it to work properly!

Alan Staniforth tried it back in the 60', with the Mini engined Terrapin, and abandoned the idea.

richardm6994 - 3/5/13 at 11:55 AM

hijac alert....but kinda relevant

something I've wondered about but never asked as I dont have a BEC is.,....would it be possible to use central-locking servos as a cheap electric gear change?

40inches - 3/5/13 at 12:14 PM

quote:
Originally posted by MikeRJ
Hydraulic gear change would be a pain IMO, imagine having to get the relative position of the gear lever correct to the gears by adding or removing tiny amounts of fluid.

The OP is referring to a bike gearbox, I believe, so purely linear.
I cant see that a hydraulic system would be worth pursuing, the electric shifters are almost instant in gear change, and there is nothing simpler to run than an electric cable. IMHO

hughpinder - 3/5/13 at 12:17 PM

Here's a sequential change in action:

http://www.youtube.com/watch?v=m4hj5vVAfkQ

And something from mountain bikes:

http://www.bikerumor.com/2011/06/26/video-acros-hydraulic-shifting-in-action

Regards
Hugh

coyoteboy - 3/5/13 at 12:20 PM

I've investigated hydraulic shifting on a bike box, it's perfectly possible using a dual acting arrangement and minor adjustments would have to be done using rod ends not the fluid ideally. It's relatively bulky and heavy compared to cables.

Can't be done (easily) with electrical means other than the likes of klik due to the torques required to shift, though I have been looking at a geared high speed stepper arrangement just for interests sake.

Chet - 3/5/13 at 06:33 PM

FYI,

I'd strongly suggest you consider the Flatshifter setup instead of trying to design a new approach.
Www.flatshifter.com

I use the Flatshifter Max / Expert system on our Hayabusa powered J15 USA demo car.

It works very well, performing both up and down shifts on both the track and road.

Graham at Flatshifter is extremely knowledgeable and helpful in setting the system up properly and answering questions.

Chet