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dean1484
dean1484 GRM+ Memberand UltraDork
1/16/13 7:29 a.m.

It is something I have thought of for quite some time. What I was wondering is does any one know the actual force required to press the clutch master cylinder in? The peddle uses quite a lot of leverage so I am guessing that it could be as much as 100-200 lbs maybe more.

My idea was to get some sort of liner motor or possibly a electronic actuator and have it press on a second master cylinder that is Ted in to the clutch hydraulics. That way you would maintain the peddle. I guess I could make up some sort of system that uses a lever if needed but then you increase the size of the unit and you need a loner working range.

I have always thought it would be cool to be able to control the clutch via a button on the shifter. Yes it would be an on off switch but that is really what you need when you are shifting through the gears. For pulling away from a stop you would use the normal peddle.

N Sperlo
N Sperlo UltimaDork
1/16/13 7:31 a.m.

Motorcycles have air clutches, but you're losing quite a bit of pressure control. Not bad for shifting up, but stop and go can suck. I knew a guy who installed one. You could actually run faster with the regular clutch.

RossD
RossD UberDork
1/16/13 8:00 a.m.

You could calculate the force you use with your leg, and the different mechanical advantages (hydraulic, levers...) to rough it out.

Say you use 20 lbs of force at your foot and go from there...

tr8todd
tr8todd Reader
1/16/13 8:17 a.m.

Most brake pedals are about an 8 to 1 ratio so I'd assume clutch pedals are about the same.

foxtrapper
foxtrapper PowerDork
1/16/13 8:19 a.m.

Problem with the tandem hydraulics. When the clutch pedal is fully released, a bleeder port is opened in the master cylinder to the reservour.

You could also do it with a cable and a bicycle hand brake lever.

wlkelley3
wlkelley3 SuperDork
1/16/13 8:28 a.m.

I've driven warehouse tugs that had an electric clutch with manual trans. Basically just a button on the gearshift knob to engage/disengage. Not sure what operated the clutch though, electric or hydraulic actuator.

RossD
RossD UberDork
1/16/13 8:52 a.m.

What about using the power steering pump and a hydraulic throwout bearing. The push button energizes a small three way valve and pushes on the t/out bearing. Releasing the button allows the valve to de-energize and allows fluid to return to the reservoir. Might need more than what I described but it should be close...

Giant Purple Snorklewacker
Giant Purple Snorklewacker MegaDork
1/16/13 9:22 a.m.

The early BMW SMG cars were just ordinary ZF manual transmissions with computer controlled magic using solenoids and valves to do the shifting. See if you can't find a diagram or even scavenge the valves from a JY?

oldtin
oldtin UltraDork
1/16/13 9:35 a.m.

I built one for the MG (ford 5.0/T5). Clutch control is on the gearshift knob. The pedal force to push the mc in is around 120 lbs, For a 20lb push, my pedal was at a 6:1 ratio - so actual force on the M/C.

There's also some multiplication in the clutch fork - something like 3:1 - moving the diaphram takes around 300 -350 lbs of pressure - at least in a T5. My set up is air over hydraulics. You can use a fast electric compressor or modify an a/c compressor for the supply. The air cylinder is (if I remember) is a 2" bore with a 1" throw. M/C is 3/4" with a 1.1" throw - which goes to a slave cylinder. Control button is basically a force gauge/linear potentiometer that is connected to a high speed valve (salvaged that off some medical lab equipment) - otherwise kelly pneumatics can make one. The button is linear in providing voltage (0-5v) - calibrated to the air valve. In the video the m/c is quick to act and slow to return - basically because it needs a few hundred pounds pushing back since everything is calibrated to have that weight pushing back.

clutch controller

dean1484
dean1484 GRM+ Memberand UltraDork
1/16/13 10:10 a.m.

That is slick!!!! I was wondering about pneumatic but carrying an air compressor and a reserve tank.. . . Well I guess you would not need all that much reserve.

oldtin
oldtin UltraDork
1/16/13 10:21 a.m.

I have a 1/2 gallon reserve tank tucked inside a fender and pressure switch for the compressor - so it's got a ready supply of 100 psi. I started with an electric compressor - knock off of a viair. It was obnoxiously loud so I modified a car a/c compressor - which actually puts out enough to run air tools - but costs a few hp in drag.

Ian F
Ian F PowerDork
1/16/13 10:44 a.m.

There was a similar discussion over on the CMS forum a year or so ago. Somebody was wanting a Spitfire but didn't have enough use of his left leg to operate the clutch (or something like that). The tight confines of a Spitfire limit automatic transmission options. A number of ideas were tossed around.

One idea (greatly simplified here) would be to use a bike brake lever on the shifter arm that operates a poteniometer. The pot would go to a small PLC to operate a servo actuator that would work the stock clutch pedal. One advantage of this is you can fine tune where the clutch will grab in relation to the lever position through PLC programming.

Back to your original idea, one potential side benefit of the push-button clutch would be to connect the same button to a fuel or ignition cut-off so that with some tweaking and practice you could do no-lift shifts.

4cylndrfury
4cylndrfury UltimaDork
1/16/13 10:53 a.m.
Ian F wrote: One idea (greatly simplified here) would be to use a bike brake lever on the shifter arm that operates a poteniometer. The pot would go to a small PLC to operate a servo actuator that would work the stock clutch pedal. One advantage of this is you can fine tune where the clutch will grab in relation to the lever position through PLC programming.

GameboyRMH
GameboyRMH GRM+ Memberand PowerDork
1/16/13 11:17 a.m.

Was gonna say some people on here have already done it but I see oldtin's already chimed in

The problem with the servo idea is that you'd need the mightiest servo in the history of mankind. I don't think you're going to get away with plain electric actuation, unfortunately.

oldtin
oldtin UltraDork
1/16/13 12:13 p.m.

In researching it, I couldn't find electric linear actuators that could move fast enough or on the solenoid front, are on/off - so too fast. Also getting perfect proportional control is tricky - or at least can be expensive. If you use feedback cylinders/valves and controllers, you can get really tight proportional control, but it will cost - it's a complicated set up in a car for proportional control - basically, getting consistent voltages - some components need 12v, some are 24v and some 5v to all play nice. The complex system rarely worked fully.

In simplifying - just use the butt dyno to detect movement - all you really need is a reliable (not necessarily proportional) relationship between the trigger and the air valve (or hydraulics if you went with a ps pump). People here had a lot of good ideas - I went the way I did for the level of control - with a goal of being able to drive in a traffic jam if needed. On the GRM version - use the trigger from a video game controller (or the linear pot I used was about $10 at digikey)- a high speed air valve will be about $250 and a 2" x 1" throw cylinder is about $50. Add in another $100-150 for air lines/pressure switch, safety valve an old sanden a/c compressor and new seals (there's a small mod to these to make them live).

Even more direct, you could skip the m/c and mount the cylinder to the trans or on a fully hydraulic system, go with a controller/valve straight to a hydraulic throw out bearing - if you can find a proportional valve instead of on/off valves.

golfduke
golfduke New Reader
1/16/13 12:21 p.m.

hmmmmm, I have access to a load cell at work. I could probably rig something up as a science experiment. This is definitely possible, and depending on the level of automation/customization I bet you could fine tune a lever operated clutch pretty easily and with minimal force input.

Damn, now you've got me curious.

oldtin
oldtin UltraDork
1/16/13 12:49 p.m.

AP Racing has an off the shelf version. Costs $10k with a minimum order of 15.

oldeskewltoy
oldeskewltoy Dork
1/16/13 1:33 p.m.

Hmmm, couldn't the old VW autostick (principle)be adapted to work by button???

dean1484
dean1484 GRM+ Memberand UltraDork
1/16/13 1:37 p.m.
oldtin wrote: AP Racing has an off the shelf version. Costs $10k with a minimum order of 15.

All the more reason I want to do it with duct tape and crazy glue.

GameboyRMH
GameboyRMH GRM+ Memberand PowerDork
1/16/13 1:38 p.m.
oldtin wrote: AP Racing has an off the shelf version. Costs $10k with a minimum order of 15.

Warn people dammit, I nearly had a stroke!

dean1484
dean1484 GRM+ Memberand UltraDork
1/16/13 2:23 p.m.
GameboyRMH wrote:
oldtin wrote: AP Racing has an off the shelf version. Costs $10k with a minimum order of 15.
Warn people dammit, I nearly had a stroke!

What no GRM group by

4cylndrfury
4cylndrfury UltimaDork
1/16/13 2:36 p.m.
N Sperlo wrote: Motorcycles have air clutches, but you're losing quite a bit of pressure control. Not bad for shifting up, but stop and go can suck. I knew a guy who installed one. You could actually run faster with the regular clutch.

so, why again couldnt a motorcycle hand-lever-style clutch lever be mounted to the shifter in the car? maybe a cruiser style instead of a sportbike clutch...think goldwing or the like. Figure out a grassrootsy junkyard way to multiply the force the lever puts out since the car clutch is likely going to require more force (theoretically would spread the engagement range of the lever throw to make heavy traffic use a little better). All components are available off the shelf, decent modulation is possible, cost is pretty low...what am I missing?

Giant Purple Snorklewacker
Giant Purple Snorklewacker MegaDork
1/16/13 3:22 p.m.
GameboyRMH wrote:
oldtin wrote: AP Racing has an off the shelf version. Costs $10k with a minimum order of 15.
Warn people dammit, I nearly had a stroke!

There can be no logical explanation for that except some idiot was willing to pay for it once before.

RossD
RossD UberDork
1/16/13 3:56 p.m.
Giant Purple Snorklewacker wrote:
GameboyRMH wrote:
oldtin wrote: AP Racing has an off the shelf version. Costs $10k with a minimum order of 15.
Warn people dammit, I nearly had a stroke!
There can be no logical explanation for that except some idiot was willing to pay for it once before.

The kicker is that since the idiot payed for it once, he still had to buy 10.

turboswede
turboswede GRM+ Memberand PowerDork
1/16/13 4:44 p.m.

Here's one way of doing it:

http://www.network54.com/Forum/12159/message/1179016544/18+month+project%2C+the+footless+X1-9

Of course this wasn't for performance so much as making it possible for someone without the use of their legs to drive their sportscar again. Still there are some interesting ideas there and it is definitely Grassroots in approach!

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