So I've been scratching my head for a week or so now trying to figure out how to spec a pedal operated clutch master for a ZX14 and come to the determination I'm a dolt who can't add, subtract, or do long division. I've seen all kinds of hydraulic calculations and formulas for determining piston size but it all leaves me completely befuddled.

The slave cylinder is quite compact and is integrated into the drive gear cover. The piston measures 35mm in diameter and appears to have a max travel of 14mm. I can attach a pic if required.

Any suggestions as to what size mater is required to drive the slave without overpowering it? I've even considered retrofitting the stock master cyl from the bike to a foot pedal but that seems overly complicated when I know an off the shelf unit will work if I just figure out which size to choose.

Thanks in advance for you suggestions.

What's the bore of the original bike master cylinder? That's got to be a good starting point!

Wyn

I use a simple maxim - Bike engine=bike clutch=use bike clutch master cyl
You can't do better than using the original cylinders, if it works on the bike it'll work on the car.

Thanks guys, both good suggestions. The shop manual however doesn't list the bore of the master, and the stock unit would be very hard to fir into a foot pedal configuration.

I think I may have gotten my brain back on line and figured this out. If the slave cly is 35mm diameter and it moves a max of 14mm then the volume displaced is aprox 770 ((rad*3.14)*height = volume). A 16mm bore master cylinder must move aprox 31mm to max the slave travel. A wilwood small brake/clutch master with 16mm bore (5/8" has a stroke of 35.6mm listed. It can however be adjusted down to decrease the stroke by use of an adjuster nut on the push rod. With a 6:1 pedal stroke to plunger movement ratio that means decreasing the pedal by only a little over 1 inch. It will probably make for a short clutch pedal action, but certainly useable.

Now, did I do that right or did I mess up the math...again.


http://www.wilwood.com/Products/006-MasterCylinders/005-CSBMC/index.asp

Operate the hand lever via a foot pedal, you can make the travel what you want by altering the pedal pivot point.

I have used matched cylinders on my R1 engine. Both wilwood.
All I did was work out the working range of the clutch lever (as a lot of the travel is freeplay), removed the freeplay and then welded a longer arm onto the clutch lever to ensure that my cylinder stopped at the end of the clutch travel.
This should mean a full length foot pedal.
(slave is a pull cylinder, not push)


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OddSaabs

quote:

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((rad*3.14)*height = volume).

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Wyn, I did mine the old fashioned way without a calculator!
I took the freeplay out, then used a rule to measure how far the arm moved in a straight line. I compared this to the 34.9mm travel of the slave (specs supplied with the slave) and then it was easy to weld the longer arm on and use the rule to work out were the hole needed to be to get 34.9mm (approx) of lateral travel.

Russ I will need to be talking to you soon about supplying me with a braided pipe, brake and clutch system.
I am going to use braided throughout and not use the solid cupranickle stuff.

[Edited on 18/11/2007 by nitram38]

I haven't checked your calculation but remember that the area of a circle is pi x the square of the radius.

Your absolutely right! Even with the formula for the volume of a cyl right in front of me I still found a way to screw it up. Duh... The calculations come out very different when the square of the radius is used.

So on the advice of a fellow builder I checked to see how far the clutch push rod moves when the slave is actuated. He figured that it would be much smaller than the total throw of the slave and he was of course correct. It is quite difficult to push in the clutch rod as you might expect, but with enough mechanical advantage (a long lever) I was able to estimate that the rod moves less than 1cm in full travel. That changes things a bit.

With a throw of 9mm and using the proper calculation (I think) the volume of the slave cyl no becomes 8,655 mm3. The volume of a .7" master cyl (17.78mm) with a 35.6mm travel is 8,835 mm3. Seems like a good match, but I get this feeling that in the end we'll just have to try a couple cylinders to see which feels right under the left foot.

Thanks again for you insight. I use this site all the time for ideas and inspiration.