Where am I going wrong here: Clutch slave/master sizing ?

[jon@harrison.ne]

spdbrake, maybe I'm missing something but this is what I see: first, "with a 1.25" throw on the 3/4" master" is not relevant- the ratio of slave to master throw is the same for any input throw. Second, and more import, the slave to master throw ratio is a function of the area of the cylinders, not the diameters since the volume of fluid pumped equals the area times the throw and area is proportional to the diameter squared (area of a circle = pi x diameter squared/4). So a one inch throw on a 3/4" master driving a 1" slave will result in a 9/16 "(3/4 squared) throw at the slave, and a 1.25 " throw on a 3/4" master will produce a 0.703" throw on a 1" slave.

[spdbrake]

Originally Posted by jon@harrison.ne

spdbrake, maybe I'm missing something but this is what I see: first, "with a 1.25" throw on the 3/4" master" is not relevant- the ratio of slave to master throw is the same for any input throw. Second, and more import, the slave to master throw ratio is a function of the area of the cylinders, not the diameters since the volume of fluid pumped equals the area times the throw and area is proportional to the diameter squared (area of a circle = pi x diameter squared/4). So a one inch throw on a 3/4" master driving a 1" slave will result in a 9/16 "(3/4 squared) throw at the slave, and a 1.25 " throw on a 3/4" master will produce a 0.703" throw on a 1" slave.

Correct. Sorry if I'm confusing. My opening statement is only a "check my understanding" feedback. (Habit from thousands of flight crew debriefs.)
Volume is volume, thats Why I recommended a a 1.125" dia coupled with his current 1.0" slave for overdrive. Or possibly reducing the slave to 3/4" giving him a 1:1 movement on input and output.

[Gaz64]

If you currently have 3/4 master, 1 inch slave, I would either increase the master in increments of 1/16 (From 3/4 to 13/16),
or decrease the slave from 1 inch to 15/16, until the correct disengagement versus pedal feel happens.

A jump from 3/4 to 1 inch is way too much in one go, 78% increase in area.

Don't want a pedal you can't operate.

Gary