still uncertain on some of the hard #s so if somebody knows, or has some thing mocked up and can take a measurement that would help. What makes it daunting is that it is very close to feasable, unless my logic is faulty, Im missing something ,or my calculator is broke, based on the numbers that have been supplied of moving 500lbs 0.275. ------------------b x s---- volume---- srf area of piston hyd throwout .....1.22 x 0.275 ..0.32 .....1.16 mc type master ..0.64 x 1 ........0.32 ....0.30 According to Pascal's principal the surface area of the piston is used to calculate the ratios. the bore size is only relevant to establis the needed voulme. And on my calculator this is a 3.9:1 ratio moving 500 lbs with 3.9 advantage is 128 lbs. of force needed on the end of the Master cyl. plunger. lets look at adding in the lever. Lever travel is limited to 3" by grip and the stroke is 1" a variable According to my calculator that is 3 to 1 ratio moving 128 lbs with a 3:1 advantage is 42 lbs. at the end of the lever. The 3.9:1 hyd ratio is multiplied and compounded by the 3:1 mechanical leverage netting a 11.7:ratio over the clutch. If a longer stroke master could be had the suface area could be less the volume the same and effort proprtionatly less. Of course if the thing needs to move more than 0.275 or is more than 500 lbs then this is far off from working like this. As the clutch wears the hyd TOB will need to stroke more to accomodate. VISA VERSA if the actual numbers are less.
I have all the respect in the world for the mathmaticians who can work this out on paper. I can't balance a checkbook. I did, however, work it out by trial and error with steel, my lathe and torch and a common sense approach. My hand clutch works. I use it every day that the weather allows me to ride. I don't know how many pounds it takes to operate, but I can pull it and hold it in for as long as I need. It is, somewhat, inelegant but it works. I am running a regular Centerforce diapragm pressure plate and a street disc with Marcel springs. As one poster noted, Boss Hoss used a vacuum booster. If you look closely at one, you will notice that there is also, what they refer to as, a "heel assist". This is a small pedal that you depress at the same time that you squeeze the hand lever because the effort at the handlebar lever is too great. You can hold the clutch disengaged without it, just not for long unless you're G.I Joe with Kung Fu Grip. This was why I sistered up the vac booster with a mechanical booster. The problem was that whenever I got an acceptable pull at the lever, it was not enough stroke to disengage. Adjusting the ratio didn't help. There was no happy medium. The electo servos and other solutions that have been offered don't spin my crank. All I want between me and my clutch, carb and brakes are steel or hydaulic fluid. The rest have too much to go wrong or there is no "feel" to them. All I can offer is what has worked for me and is on the road and will be on the road later today, scaring the weak and infirm and making lesser men feel inadequate
Can you post some pics of this setup. You mentioned this a few times on this thread and I have been to your site and It was hard to Find what you are talking about. You mentioned 2008 posts. I saw a few pics but they dont show how you finished it or the heel assist you mentioned. Sure would help alot.
11.7 to 1 ratio would mean for 3 inch movement at the lever we get only 0.25 movement at the clutch centre, not enough travel. And even then it's still quite a high poundage to pull on a squeeze type lever. As I said before I am not saying it's impossible, in fact I used a bike style lever operated clutch on a small block hemi I put together a couple of years back, but to get it to work required fitting a race clutch which requires half the amount of movement at the thrust to go from free play to fully dissengaged, which in turn allows the ratio to reduce the force at the lever down to something that can be operated reasonably easy . But it's still heavy, without the trick of using a zero marcel plate I figure all car clutches come out on or over the limit of human hand squeeze, hence I would tend to think that the simple answer is to use power from another source to actually move the clutch and just control that with a nice light easy to move lever which the operator has more chance of being able to move smoothly and thus engage the clutch. Because as I say even if you do manage to get a ratio of master and slave cylinders which moves the release bearing far enough the lever will be nearly needing both hands to squeeze, even the 42lbs worked out above is too much to pull more than a few times, you would soon find that makes the thing a real bind to drive.
Can you post some pics of this setup. You mentioned this a few times on this thread and I have been to your site and It was hard to Find what you are talking about. You mentioned 2008 posts. I saw a few pics but they dont show how you finished it or the heel assist you mentioned. Sure would help alot. Sorry about the lousy pix on my blog. The only way to get a better shot is to take it apart and that ain't gonna happen anytime soon. What I have is a lever, about 10 inches long with a pivot at the center. This mounts to the frame of the bike and the lower end has link that goes forward to the TO arm. There is a heavy spring, I got mine from a Caddy hood hinge, that goes from the lower end of the lever to a tab welded to the frame. It is stretched very tight. It works on an over center principle. When the clutch is disengaged, the lever pivots clockwise until it just, barely, goes past center. When I pull the clutch, the lever begins to go counterclockwise. As soon as it goes past center, the Cad hood spring begins to apply pressure and assists the vacuum booster and badda bing, there ya go. I might have been able to use the spring booster alone without the vac unit if I were to use a Long or B&B cover. The diapragm clutches actually get easier to disengage the farther you push. It is a function of the Belleville spring that they use. The problem that I had was, if I pulled the Cad spring too tight, the clutch would not reengage because the Belleville spring didn't exert enough presure at full disengagement to overcome the force of the hood spring. Since a Long or B&B gets harder the more you push, it might be a better choice. I could just crank up the tension on the mechanical booster until I get an acceptable pull at the hand lever and toss the vac unit in the parts pile. I don't have a heel assist. I don't need it. Here is a sketch. I'm no artist, so don't snicker
I agree but its so damn close! Of course if that bearing needs to move 0.5 to actually take up the slop, free play, adjustment and wear issues then this is just piontless, that 0.275 got me going on this again. The numbers are pretty close and perhaps a synergy of rounding error?? Previous posts and discussion mentioned 50 lbs of "grip" on the human hand, would be about the limit and remain usable. So I would take it that you agree with the theory and train of math layed out above ?? Lets just say that for Chopholiday's project the pressure plate is much less, then this would be within our previously discussed limits. Or if TOB travel is less then that also would bring it line. Using a master with a longer stroke and smaller bore would also decrease the effort significantly. There are alot of variable elements too many to make a solid determination. The link above has a great write up on MC master cyls and even pictures an adjustable one. You know I had to google it ("marcel" clutch") and I got a beautiful descrioption of purses.WTF?? took me a while to find a tech on it pertaining to Automotive clutch. That seems to be what you dont want to be with out. I was unsure what that was, Thanks for a new thing !!! Ok so what do you have as far as 12v servos capabile of pushing 300lbs on a 1.3:1 clutch fork and move it an inch or so. Where did you find it?Where do I look.
Did you look into the dual disc clutch? With 2 no marcel discs, the travel would be little or no more than one disc with no marcel, and the pressure needed would be cut in half. My experience with dual disc has all been in trucks, there they are awesome. Might be enough to make this work without power boost.
Do you have any hard #s on that set up? How did it behave when you put it in the truck? That is a diaphram spring Correct? vs 3 finger My understanding is with a diaphram spring the pedal pressure is less and the clamping force are more? Is it the travel that is less with equal release pressure at the bearing would make a lighter pedal? Or less pressure at the bearing but more travel to make a lighter pedal with a pivot point adjustment? My mind is telling me that the travel required would be more because there needs to be a release and clearance from 4 surfaces, but my mind has BSed me before. Do you have a good link for the dual disc clutch set-up and theory ?
I put a link to the Ram setup in post 53. Here it is again - http://www.ramclutches.com/Specialty products/Street_dual_2.htm It's a diaphragm setup, Ram is very good about building special setups so I believe you could get whatever you wanted to make it work. The Truck setups I worked on were OEM in medium duty (33,000 lb GVW and up) trucks, not something I adapted. More friction surfaces mean more lift, but a second disc would not double the lift. A 9 plate MC clutch only needs less than .065 lift to release freely, that's .007 per plate. The .030 I posted before I now realize is the air gap spec - after the clutch is released, you need to be able to put an .030 feeler gage between the plates.
Multipule friction plates do increase the clutch's torque for the same spring force, however unlike a motorcycle clutch ( which has Zero marcel again !) where 0.07 per plate will allow the clutch to spin free an automotive clutch has this spring wave built in which means that pressure plate has to move by several thou more than the amount of wave in the plate, a typical street clutch can have 65 thou of marcel wave, which means the plate is moving 0.065 plus what ever clearance. Yoyodyne quotes 0.030 clearance, so that's 0.095 times two times the ratio of the diaphram fingers ( 3 to 1 as ball park ) which is 0.57 so while the spring force has gone down the distance has increased by an amount that puts us right back where we started from. I tend to think of this as reality, a world where you get something for nothing is not the one we live in. No matter how you do the maths, a automotive clutch with a large amount of excess travel built in ( as is the norm for smoothness of engagement ) is going to be very heavy to work with a hand control which is squeezed. The amount of force times the distance is going to be high what ever. Assuming we want to move the clutch full travel in a second, say allow the force to be 550lbs over full inch travel, which is a nice easy 1/12 hp sized motor, which at 12volts is going to draw just over 5amps, not that big a motor, windscreenwiper sized would be plenty, leadscrew 1mm pitch, 25revs would be our inch movement.
Right. But consider two discs with no marcel. And the air gap figure was to insure clean power shifting at high RPM with balky synchronizers etc, probably not as much necessary in this application.
Exactly what I have been saying all the way through, if you use a race plate with no Marcel the distance you have to move the pressure plate comes down to only a few thou and you can operate the clutch with your paw, which is how I have got round it before. Only down side is that with zero marcel the clutch is fairly on/off, so the operator has to have a higher skill level than Mrs Murgatroyd. But yes I can confirm that with zero marcel it is perfectly possible to hand operate a car type clutch. Still ends up as heavy as any bike you are likely to find but it's operable.
I really think with hand operation you won't miss the marcel. Fingers are much more sophisticated than feet, and a sophisticated clutch linkage(i.e.hydraulic w/no belcrank) will reduce the slop present in an oem linkage. Modern bikes have a plate in the clutch that functions like the marcel in a car clutch. First thing we do is take that out and throw it away when doing HP modifications, and it reduces the amount of travel needed and the clutch feels much better to a skilled rider's hand.
Some sort of power assist has to be possible. I know they exist - some sort of hydraulic pump or linear actuator that lets you move your hand clutch a little and (using the power assist power, not your hand's power) moves the clutch arm a corresponding (but greater) amount. I've seen stuff like that in manufacturing plants and such - just not sure what it would be called or where to find it. But what do I know, I've always run an automatic...
Those are the possibles as I see it, ether mod the clutch to remove the excess movement ie use zero Marcel plate plus probably fit a axial slave to reduce losses in linkage, which would allow the clutch to be hand controlled, but the lever will still be heavy. Or you have to take power from some other source, be it vacuum, pressurised oil, or electric. The second option has the advantage that it allows the use of a stock street clutch which is may already be fitted, plus it allows the force required at the lever to be reduced to a much more comfortable level.
I plan to test my theory of a working setup in the next few weeks...... It is mostly borrowed from Amphicar's setup: http://www.amphicar.com/oldspotlights.htm (go to this page, scroll down a bit, there is an explanation of what he did, plus pics. I am a paraplegic myself, so I have been pondering this one for the past year. First with my stock banger-powered A coupe, (sold it) and now for my new AV8 RPU with a 36 for flathead and 3 spd. One small change I am making is to omit the vaccum pump Amphicar uses, and use engine vacuum from the flathead to run a power brake booster (with the motorcycle clutch lever+ some linkage PULLING the plunger INTO the booster, sending fluid out to a wilwood slave.... Question is, can I get the 1 3/8" throw to do what I need it to do by pushing the lever that actuates the rod and other shit that actuates the clutch...... I am also toying around with adding another lever to my regualr hand controls for the clutch.... Seems like the easiest option, although I question the safety of it, and it would take some getting used to. I dont want to switch anyhting around, cuz that would be dangerous going from my Hot Rod to my daily driven turd! Thanks for the good read..... James
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