Push Button Clutch (GRM style) AKA home made.

I have been driving my 924s daily for about 5 years now. This means among other things lots of Boston traffic. I have been thinking that it would be nice to make the clutch a push button deal. With the exception of starting in first this seems easily doable. And with a little more thought even standing starts seem possible.

I have been looking for an electronic ram that I could set up with a second master cylinder that would be T'ed into the pressure side of the clutch system. I would then, with a push of a button, be able to activate the ram that would press on the master cylinder it causing the clutch to disengage. I was going to put a safety switch on the clutch peddle (similar to a brake light switch) that would prevent the electronic clutch switch from working when the clutch pedal is in operation. If both were used at the same time it would blow the slave cylinder apart possibly destroying my clutch.

1. Anyone have a source for the ram that I cold use to activate the master cylinder?

2. I was thinking of installing the back flow reducer that is used in the early WRX's to slow the engagement. Reducing the drive-line shock of instant on off that this would have.

3. I was even thinking of having a electronically selectable valve that could be switched (possibly by gear location selection) that would cause the clutch to engage slower allowing for starts in first gear.

Other than it allowing for faster shifts there is is no real advantage to this system. In essence you could speed shift the car and still use the clutch. It is one of those things that I will probably build just because.

It would make driving around town much easier. The clutch would become a push button affair.

Anyone out there already done this? Any info on sourcing the ram unit would be very helpful.

Anyone know the mechanical force required to operate the master cylinder on a 924s?

I remember seeing a similar setup on a japan grand touring car featured in another mag, years ago. Thought it would be hoot to build my own, and use it for around town, and if you could figure out the whole standing start trick, market it to the disabled crowd. imagine if you were injured and became a parapalegic, and couldn't work a clutch anymore. If someone came to you and told you that you could row a gearbox again would you jump at the opportunity? Good luck with it, and keep us informed on how it works out.

For actuators, McMaster Carr should have almost anything you can think of. Maybe add an Accusump to your engine oil system and disengage using engine oil pressure. Low pressure/low RPM might mean slower clutch engagement while at high pressure/rpm it would engage quickly?

You might also try the FSAE forums. I was working on a Nitrogen-powered clutch actuator for our car when I was in school, but abandoned it when the drivers were hand clutching better and more consistently. It was also VERY much an on/off system. I have heard that other teams have been successful in the past though, so YMMV

VW semi-automatic..

Vacuum operated clutch with a fluid coupling to smooth out engagement.

It sucked pretty hard.

Shawn

Ok I started doing some looking around here and found I need some tech info here.

McMaster carr was my first stop. But I was not pleased with what I found. I was thinking of using the power steering pump for my source of hydraulic force. This still may end up being the best way to go but it could lead to issues as low engine speed means low pressure so the activation would be based on motor speed. I would also have to figure out a way to electronically control the valving adding another level/layer of complexity

Looking further I found a source of electronic linear actuators that may fill the bill. I like the electronic option as ti makes setting things up much simpler. A simple moment switch to activate. Mount the linear activator and the ,aster to a plate in the proper configuration and just run a single line T'ed in to the pressure side of the clutch system, wire a power source and the switch. This seems way to simple. The electronic ones are also small about 6"x2"x3" +/-

So now a couple questions.

1. What is the total movement of the master cylinder for a 944. IE how far is it compressed / what is the piston travel in the master cylinder?

2. What is the force required to move the piston in the master cylinder. This one is going to be a bit of a pain to figure out. I am hoping some one knows this. I will probably have to measure the length of the clutch peddle and get the amount of offset from the pivot point that the rod is that compresses the master cylinder. Then measure the force to move the peddle (simple scale between my foot and the peddle). With this I can back calculate the force being exerted on the piston of the master.

I found several potential electric linear actuator units that have 1" and 2" travel. They also have good speed/force. The high speed is rated at 55mm/sec at 35lbs. The standard unit is rated at 25mm/sec at 57lbs. The next one I could find is at 10mm/sec at 150lbs. After that it gets to slow at 7mm/sec at 200lbs

Any info on this would be helpful So now I guess it is time to go get data from the car and see what I actually need.

What I am hoping to get around is the need to start calculating the volume of fluid moved. I will probably have to go with the higher PSI rated unit making the speed a tad slow. if the travel is one inch then at 10 mm/sec it would take 2.5 second to disengage the clutch. This is not an acceptable option and probably lead to waring out the clutch. If the force of the larger ram is needed I will have to go get a master cylinder that has a larger bore so the that I would move more fluid with less movement of the piston in the master.

So while I am asking is there a list of master cylinder bores out there? I am sure that the Hot Rod people must have this info for there custom setups.

MC bores: 5/8" or 0.60" or 3/4". Look for Girling or Tilton. The various GRM advertisers like Pegasus and maybe Racerparts Wholesale carry them. I know Pegasus has a whole selection.

MRS' had an automatic manual shifter setup, at least for the first year. If I recall, they sucked and were slower than just shifting it yourself.

There was a thread on the Xweb forums about building something similar for an X-1/9, they used air pressure and a BMX brake lever on the shift lever.

What if you had the actuator move the pedal, instead of a second master cylinder?

A pneumatic linear actuator will probably be the way to go. Finding an electric solenoid with enough cajones to move the clutch is gonna be a trick, and they are either on or off. There will not be a way to control it without a complex spring/damper setup. With a pneumatic actuator you could use a regulated exhaust on the actuator to control how quickly you let out the clutch.

It may also be easier if you used an additional master cylinder, which would be controlled by the actuator. You could remote mount it where ever to get it out of the way and just tee into the line.

Ingredients

clutch master

linear actuator

(2) solenoid valves

regulator

air compress + small tank

simple logic circuit

Could dragster airshift components be modified for what you're doing?

I have no experience with them but it was the first thing I thought of.

Shawn

If you add a source of hydraulic pressure without having the pedal pushed in some, won't all the fluid just end up in the reservoir? You'll need to figure that out as well

Strizzo wrote: If you add a source of hydraulic pressure without having the pedal pushed in some, won't all the fluid just end up in the reservoir? You'll need to figure that out as well

Electronically controlled check valve that is activated when you activate the ram?

Could I put the second master inline with the first instead of a T-ing it in to the high pressure side?

Anyone know the answers to these scenarios?

hit these guys up?

http://www.pingelonline.com/components.htm

Sweet!!! That is what the GRM Bezerkley (sp) bike powered thing needed!!!

You could add a couple hydraulic solenoid operated valves pretty easily to a logic sequence. You can get kits that plug into your computer via a usb or serial port. I've played with em for a few years, and they are super simple to program. Everything you need besides the mount for the linear actuator to the master cylinder is readily available.

1) Press button (momentatry) 2) close hydraulic valve to primary master cylinder 3) open hydraulic valve to pneumatic master 4) open exhaust valve to linear actuator 5) open intake to linear actuator 6) Valve extends and pressurizes master cylinder #2, which disengages clutch 7) wait for command

1) Press button 2) Close intake valve to linear actuator 3) Open regulated exhaust valve to linear actuator 4) Clutch lets out (use like a 2-3 second delay) 5) open hydraulic valve to primary master 6) close hydraulic valve to pneumatic master 7) wait for command