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On Thu, 2003-09-04 at 00:56, Shad Laws wrote: > Hello- > > > Well, that's great for the Dakota... > > The problem with the setup that I (and ISP people) discovered is this: as > the line ages, it becomes more and more compliant. It doesn't fail; it > doesn't burst; it doesn't leak. It just gets "flexible" and swells up under > pressure like a rubber brake line. Sounds harmless enough, right? > Well, this Dakota has 150K on it of farm truck service. The plastic line runs about 3" away from the exhaust pipe. And it has not given me a bit of problems. And Dogdge has probably sold hundreds of thousands of these over the years. I think the problem is, is the quality of tubing that is in the ISP kit. We use a lot of plastic air line tubing at work for industrial use. We have had problems with a couple brands. We have switched to Parker-Hannifin and had no more problems. > > > I calculated the pressure on the line at only about 100psi under normal > > conditions. This is on an 11" truck clutch. Our clutches should not need > > much more than that even on compitition engines. > > I disagree... it's higher than that for us. The math requires that you know > the clutch clamping force, the clutch arm ratio, the slave cylinder > diameter, and the pressure plate finger pivoting ratio. I know all the > numbers off the top of my head except the last one, so I can't do it for my > case. > I doubt if it is that much higher. You are going to a lot of extra work to calculate it. Figure the square inches of the master cylinder and the slave. Mine are 3/4" bore. The one in the ISP picture looks like they are both the same bore.Use a bathroom scale to calculate the force required to operate the pressure plate. Calculate the leverage length of the release arm and the clutch pedal. Clamping force of the clutch has nothing to do with it. It is pressure needed to release it. Since I now have air line fittings in mine, I can put a pressure gage in line to prove it. It is a PIA to bleed the system but I can do it. -- Russ Wolfe '66 FB MT '71 FB AT '65 Bug (not running) russw@classicvw.org http://www.classicvw.org ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ List info at http://www.vwtype3.org/list | mailto:gregm@vwtype3.org