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Old 09-11-2002, 03:31 PM   #1
stewgod
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Question Is It Possible to Lighten the Clutch Pedal?

I'm a paraplegic in dire need of some expertise!

My '02 WRX clutch is heavier than my previous 5 speeds (Jeep Wrangler & Nissan 240SX). Since I have to engage/disengage the clutch with hand controls, it's a bitch to do in the Soobie.

I need to find out if it's possible to reduce the (pedal) spring tension?

My only other avenue is to consider fabbing up a different hand control mechanism (ie motorcycle clutch lever-to operate some sort of custom servo).

I hope someone out there can help!

-Stew
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Old 09-11-2002, 04:17 PM   #2
GLwagon
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Most of the tention you are felling is from the preasure plate springs... more clamping force to hold clutch.
I would seriously look into having a new pedal made with diffrent geometry to leigthen the pedal throw or shorten the cable actuation... (this would take some measuring & thought...)
The main thing tat has to be kept is the switch for the cruse dissengaugement... The switch for the "start up" can be bypassed (just connect the wires together )
With out seeing the arm controlls... the only thing I can recomend is locating the actuating arm as low as posible on the factory pedal...
Any kind of helper spring setup would put undue stress on the throwout bearing...

or in your spare time lift weights... you'll be as tough as Swartenager no time
best of luck...
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Old 09-16-2002, 12:59 PM   #3
Dealer Xing
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My BMW's clutch pedal is like a rock, I may start developing uneven legs driving the beast. I havebeen wondering for a long time how to lighten a clutch pedal effort too.
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Old 09-16-2002, 05:55 PM   #4
goobie
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Default Idea

Well depending on your budget, you could think about doing a custom job on the hydraulic system of the clutch. I'm not an engineer by any stretch of the imagination but if one where to increase the amount of fluid displaced by the motion of the peddle it should in effect make the peddle "lighter" to operate.
If you maybe could find a slave cylinder with a bigger bore (If you find one that fits let me know!!) and a larger diameter hydraulic line you could push more fluid through the system while requiring less effort to do so. For the ultimate effect you could also attempt to increase the "Piston" (or plunger or what ever it's called) in the master cylinder so that more fluid will move from the source (i.e master cylinder)
While all of the above is possible to do, it will require a sizable budget (I'm thinking over a thousand) and a lot of cutom work and most likely some machine time which can drive the cost through the roof.
I would however be a cool project to do
I was acutally mulling this idea over a few weeks ago, not nessicarily to make the clutch peddle lighter but also more precise and consistant.

Can anyone offer any info to either support or disprove my idea?
Cheers,
Chad
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Old 09-16-2002, 07:20 PM   #5
GLwagon
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Default Re: Idea

Quote:
Originally posted by goobie
if one where to increase the amount of fluid displaced by the motion of the peddle it should in effect make the peddle "lighter" to operate.
If you maybe could find a slave cylinder with a bigger bore (If you find one that fits let me know)
you lost me some where, I think you have the right idea...

look at a floor jack design.... a tiny piston moves a bigger large one... 1:50 size hypethatically...
if it were 1:1 oooooffffff.
the clutch master & slave cylender are the same princeable...
if the master was 1/2 the diameter the slave the slave would only move 1/2 the masters movement...
I think there is a reduction designed into the factory system... the problem is at what point does the clutch not completely disenguage???the piston dia. of the master needs to be smaller OR the slave needs to be bigger
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Old 09-20-2004, 08:13 PM   #6
stewgod
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Default Spec Sizes for Stock '02 Clutch Master & Slave Cyl?

I think that I may be onto something...

I'm trying to find out the stock sizes for my '02 WRX Clutch Master & Slave cylenders...

HELP!


Stewgod@aol.com
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Old 09-20-2004, 11:28 PM   #7
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Yeah....you can change the bore sizes which will increase/decrease effort. However without going with a complete custom job, I'm not sure you're going to be able to find a slave or MC for the clutch system that will signifcantly alter the effort.

If you really want to go that route, I could dig through some of my old engineering books to try and see how much effort will increase decrease by changing the bore sizes.

I'm trying to think of something else, the only other thing I can think of is to make some sort of pivot arm that assists pushing in of the clutch.
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Old 09-20-2004, 11:40 PM   #8
stewgod
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That would be a great help!

Right now I've got a sample of one of these actuators www.addcoinc.com/i_actuator.htm

The 723 has 60 lbs. push/pull force & Speed = 1 1/2 inches per second. I'm trying to find a spring loaded 10k pot to mate to a motorcycle clutch lever. Ive got another sample from Celesco - www.celesco.com/cet/index.html.

But I'm thinking that if I could mate a Brembo Motorcycle Lever/Hydrolic Clutch assembly to do the very same that the stock clutch master & slave cyl.s do now.... I'd be much better off.

The only thing is... I dont know the stock bore sizes to tell my Brembo rep., so he can advise if it's do-able or not.

So if you could tell me the stock bore sizes, that would be awesome!

thanks
Stew
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Old 09-21-2004, 12:25 AM   #9
Legacy777
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Hmm.....those actuators and adjustable pot sound interesting. Not sure that would give you the best results, but it'd be cool.

I think the wrx slave cylinder has a bore of 11/16" The older turbo legacies I think have a bore of 3/4"

The older turbo legacies had a MC bore size of 5/8" I'm not sure if the wrx has the same bore size for the MC, however I would think you could give these #'s to your brembo guy as some rough numbers.

You may want to check out this thread on the legacy central bbs.
http://bbs.legacycentral.org/viewtop...utch+bore+size

I had to do some homework for my awd & 5spd swap.

I'm going to also point vrg3 to this thread, to see if he can give some help.
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Old 09-21-2004, 12:47 AM   #10
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I think a different hydraulic control system is probably the most reasonable way to decrease clutch effort. You will have a tradeoff, though -- if you increase mechanical advantage you also increase the length of the throw. Is that okay? Cuz then the way to go might be to eschew the stock master cylinder entirely and mount some other kind of hydraulic master cylinder with a smaller bore in the passenger compartment. You could connect that master cylinder directly to the slave cylinder using a long custom brake line. The slave cylinder uses an M10x1.0mm banjo fitting.

If you do it by using a larger-bore slave cylinder, it might involve having to modify the clutch pedal itself to allow it to travel further than stock.

I believe the stock WRX master cylinder is 11/16". The stock Legacy Turbo master cylinder is 5/8" as legacy777 said, but it won't bolt up in place of the WRX one as far as I know. If you could find a 1/2" or 9/16" master cylinder of some type maybe that would work.

Maybe something like this, assuming it has sufficient travel? http://www.hardracing.com/GP%20Tech/Thumbrake.htm

I think the numbers for the slave cylinders might be wrong... I know the stock 1st-generation Legacy Turbo slave cylinder is 3/4", but I think the WRX stock slave cylinder is 13/16"... I posted the wrong information in that thread on Legacy Central but mile hi corrected me.

If you do want a springloaded pot, maybe you could adapt a throttle cam from some car or bike? The cam is typically springloaded and the throttle position sensor (a potentiometer) mounts to it.

How much do you need to decrease the effort? Do you think it might be possible to put a stronger spring in parallel with the stock clutch release spring mounted under the hood?
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Old 09-21-2004, 07:50 AM   #11
duncangrant
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Stew, could you describe in some detail what your present system is, how it works and how you use it? In particular how much load and stroke can you tolerate on the hand control - I guess your steering with your clutch hand while shifting?

It sounds like you need a servo of some sort. Maybe a 'remote' brake servo could be used, but they're kind of big. Do any of the larger bikes have servoed brakes?

I guess the standard pedal has an effort of ~50lb over 6in so thats ~300 lb-inch. That electric actuator is only capable of 60*3 or 180 lb-nch, so I don't think its up to the job.

Edit-
Maybe these links will help:
DIY remote servo
Guidosimplex (Italy)
Electronic Clutch

Last edited by duncangrant; 09-21-2004 at 06:29 PM.
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Old 09-29-2004, 05:09 AM   #12
stewgod
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My hand controls right now are pretty simple because they're made to operate an AUTO trans.

The hand control is a bar (like 1/2 a handle bar on a motorcycle); positioned just like your turning indicator, off/out from the steering column off the left hand side.

TO BRAKE: a rod drops down off the handle bar straight to the top of the foot/brake pedal.

TO ACCELERATE: (for the auto trans hand control set-up & way it was designed to be used) One rotates the hand bar, twisting it around the column so that you're pushing it towards the floor mat. As if you were to twist the turning indicator around the column.

5 SPEED SET-UP: Brake remains same, but the motion to accelerate now operates the clutch. And now the throttle is operated by a jet ski throttle lever & cable. My problem is (A) the tension of the clutch pedal is much greater than other 5 speeds I've owned, and (B) the distance I must twist/push down to engage the clutch fully, is so great that I'm smashing into my leg in order to fully engage clutch to shift & start the car.

ULTIMATE SET UP: I'd like to utilize a motorcycle clutch lever (cable operated or possibly mate a Brembo Hydrolic Clutch lever). This lever would mate to a master cylinder that would work a slave cylinder (mounted in parallel with the stock slave, so that other able bodied people could operate the car). Brake would still remain, and throttle could either (A) go back to the normal/auto motion or (B) use a twist motorcyle throttle.

I think that I'd lean towards using a cable clutch set-up because I'd like to fab a lever for the shifter as well as the lever on the hand control bar.
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Old 09-29-2004, 08:44 AM   #13
duncangrant
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So for a gear change you let go of the wheel - or does the clutch extension lock in the down position?
Is a solution that requires releasing the wheel while changing acceptable? Are insurance happy with that?
It sounds that for your existing solution to work acceptably you need to reduce both the force and travel of the clutch - and that means using a servo.
The m'bike clutch lever will definately require a servo.

For a simple servo-less solution would this work? - Have a separate large travel mechanical lever which can lock-down, preferably on the rhs to simplify shifting. Mounting on to the transmission tunnel shouldn't be too hard. The mechanism to cross-over the other pedals to get to the clutch would have to be carefully designed, but it would still be simple. It could use a separate slave cylinder tee-ed into the clutch line to avoid the mechanical link but there are complications with that (check valves and a release valve in case both pedal and lever are actuated). A 12-15" throw should give an acceptable weight.

Is the brake operation acceptable?
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Old 09-29-2004, 03:06 PM   #14
stewgod
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The clutch lever/hand control does not lock in place. It wouldn't be feasible to have it do that.

When I shift, I engage the clutch (with the hand control) using my left hand, and my right hand reaches the shifter and changes gears. Yes, my hand does leave the wheel (as I only have my right hand to steer); however, after engaging the clutch I can put my thumb on the wheel and hold the cars course. I usually can shift when driving in a straight line, so it's not a big deal.

Not the greatest image of the controls I've been using: www.advanced-mobility.com/Products5.htm

INSURANCE CO. - It's not something that I make aware, but they do know I ride a two wheeled motorcycle and don't have any objection to that.

The servo-less idea is kind of where I am right now. With a mechanical leverage cam set up - which isn't working well at all. Too much throw & too much tension to push in the clutch. The lighter I can make the clutch, makes the throw distance greater...

I've got that electronic servo - which I agree with you, probably wont work. I wanted to mate that under the dash, and have it simply push in the foot pedal. That way I wouldn't have to plumb wires n' hydrolic hoses n' mount a master & slave cyl.s. Also, I could get away with mounting a 2nd clutch lever (on the stickshift itself), so I could either engage the clutch on the hand control bar & stickshift.
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