Hey all, I'm trying to figure out what my force to press the pedal needs to be to disengage the clutch. I have an 8BA coupled to a T5 with a 1950 car bellhousing. I have the speedway 10" long style (1800#) pressure plate. I'm pretty sure I'm going to have to use a bell crank to gear down the force but I have no idea what an acceptable or target force should be. If I have a clutch ratio setup like the attached picture, I can get the pressure plate force from 1800# down to about 36# at the pedal. 1800# x (1.5/11.5) x (1/3) x (2.5/5.5) = 36# Is this reasonable? I'd like to have a general idea of what to shoot for before I get to far into making everything and find out I'm way too light or to heavy. Thanks!
You need to include in the calculations the distance the pedal has to move and the distance the throw out bearing needs to move.
That 1800 lbs....is that rating at the pressure plate itself, or at the ends of the release fingers? They are also levers, eh?
I'll have about 10" to press the clutch pedal before it bottoms out. Geared per the drawing I'd get a throw out bearing displacement of a little less than .25", assuming no slack or slop. It's there a rule of thumb for the bearing displacement? Sent from my SM-T590 using The H.A.M.B. mobile app
Manufacture said it's 1800# clamping force. I can't access the plate at the moment but found a spec that said the fingers are about 4.7:1 Sent from my SM-T590 using The H.A.M.B. mobile app
I don't know if this helps but my clutch is rated at 2000# clamping force , the LINKAGE ( not counting the clutch fork in) is 7:1 and is pretty easy to depress for my 72 year old knees . Because you have mech advantage at the fingers ( levers) , the clutch fork and then the linkage , plus the way the linkage is designed , figuring how much pedal pressure is iffy at best IMO....
IMO... set up your belcrank with different [distance from the fulcrum] holes to let you adjust your mechanical advantage... if the holes would be too close to each other then make side by side levers with the holes slightly different... I let my pedals pull not push... I run a 46" shaft [red] that is threaded at each end... then a belcrank that changes pull to push at the booster/cylinder... clevis' on each end make adjusting the brakes or the brake light switch easy... this raises the cylinder so no need for residual valves, it also puts the master under the trunk floor [trap door] no carpet "flap" in front of the drivers seat... . lousy pic but it shows the set up, pinto m/c booster with '34 pedal...
There is a huge amount of relative information here http://www.novak-adapt.com/knowledge/clutches-etc
I think an easy way to do this without all the calculations is to replicate what was in a stock Ford. I did my own clutch set up only to find I couldn't push the pedal with both feet! Some of the brethren here enlightened me to pedal ratios and all that but I looked at what a stock setup looked like as a guide. Got a couple setups from 46/47 Fords, a pedal box from an early F1 and then shortened the pivot width to fit the area I needed it in leaving the levers and the rest of the assembly as close to stock as possible. I did make up my own pivot mounts. I did add a lever to the inside of the clutch arm, same position as stock, to move the rod away from the frame. Works very well.
Thanks 2fast. I've seen a bunch of posts from guys who reference a 6:1 or 7:1 linkage ratio (without the clutch fork). My pedal is 11.5":1.5" which gives me a 7.666:1 ratio, without any bell crank. I think this is where I'm confused because I tried connecting this pedal radio directly to the clutch fork and could barely push it. So I figured I needed an intermediary bell crank to gear it down. I guess I need to just mock all this up with a bunch of adjustment holes and see what works. I was hoping to get something close without having to weld and grind a bunch of times.
What I have done in the past is to bolt my clutch, pressure plate and flywheel together while not bolted to the engine. I then took it over to my press and with a socket or release bearing that can ride on all the clutch fingers in place, measure the static height. Applying pressure with the press, I determine how much travel is required to fully release the pressure plate. Now you have a target to achieve with your pedal and linkages.
I used approximately 7:1 ratio for my clutch pedal. Works well Sent from my moto g(6) play using The H.A.M.B. mobile app
My setup is similar to GordonC above , I'm wondering if you ( Magnus) have a faulty PP or binding in the linkage ???
I ended up mocking up the linkage and it seems to feel pretty good now on the clutch pedal. I'm not sure what the force is, but it feels similar to other cars I've driven. Ended up with a 8.9:1 ratio not including the fork. I was able to turn the trans output shaft to verify disengagement of the clutch and also could feel it engage. Now I just need to break it all down and make a cleaner version of it, probably with a couple adjustment holes in case I want to change it later. Do you guys include a hard stop somewhere in let the pressure plate limit the pedal? Sent from my SAMSUNG-SM-G891A using The H.A.M.B. mobile app
Looks like you do nice work. I'd put a pivot of some kind where it attaches to the clutch lever. In picture 2, I'd weld a tab on the cross member tubing that sticks out over the bracket behind the pedal pivot. Then I'd drill and tap a hole to bolt them together and give additional support to the pedal pivot.
31 Vicky, there's a lot of info in that article from Novak that you provided the link to, I ran off a print to keep!
I'll definitely tie the ends to the frame or trans on both the pedal shaft and bell crank shaft to make sure it doesn't move. Sent from my SAMSUNG-SM-G891A using The H.A.M.B. mobile app
I'm no engineer but it appears to me that the angle of the pedal to bell crank rod is causing some of your problem ...can you not go forward to the front of the bell housing to a bellcrank then back to the clutch fork ??? That's how most stock setups were ...
Archimedes Quotes. Give me a lever long enough and a fulcrum on which to place it, and I shall move the world.
Another observation , see how the fork is towards the rear of the bell housing hole , most are towards the front of the hole when engaged ....
The vertical distance between the pedals and the clutch fork is about 8". I can't go straight to the fork otherwise it's too big of an angle. My understanding of levers is that as long as the rods are roughly 90* to the pivot lever and the levers are roughly parallel to each other, it'll be fine. I'd like to keep this all under the body as much as possible. I want to keep any long rods in tension if possible I made a mistake and ran my exhaust almost right through here so it makes the bell crank a bit of a challenge. If I can't get a good solid setup I'll rethink the exhaust to locate somewhere else. Sent from my SAMSUNG-SM-G891A using The H.A.M.B. mobile app
The clutch fork came loose from the bearing and I forgot to fix it before shooting the picts. Here it is engaged. Side question: other than those two little U shaped springs on the bearing, what holds the fork in place? Sent from my SAMSUNG-SM-G891A using The H.A.M.B. mobile app
U-shaped spring( fingers) hold fork to pivot ball , flat springs hold in bearing groove , typical Chev.. if the bell crank lever was parallel to the lever on the pedal shaft , the other bellcrank arm forward of vertical......just thinking , bout all I can do anymore....sorry....
This looks all ass backwards Start here Put your clutch pedal tab on top 180ish Z bar 1 up 1 down Work out draw up your degree radians so yo don’t go over center Not quite sure how this current mock up can work,,, But you said it works better so maybe I’m FOS
If this sketch shows how the linkage looks at half pedal travel then it should work ok. I understand the constraints of space....the tab on the pedal goes down so it won't it the floor, the Z bar is in back so it will be out of the way of the exhaust manifold. I'm not too keen on the cantilevered pivots, adding a brace across them will help, but it would also help to something solid. Perhaps the pivot shafts are large enough that they don't deflect noticeably.
I've done some calculations and both shafts shouldn't deflect more than a few thousands of an inch. Even so, I'll tie the ends to a fixed point so everything is in tension when pushing, so it's not cantilevered. Sent from my SAMSUNG-SM-G891A using The H.A.M.B. mobile app
For the mock up, I was more concerned about pedal force than getting the angles exact. Now that I know what works in terms of ratios, I can clean it up to get everything at right angles. I have to keep both tabs on the same side (can't be 180* from each other) because I need a pushing movement from the pedal and pulling on the fork. Sent from my SAMSUNG-SM-G891A using The H.A.M.B. mobile app
I was thinking a heim end with a pin going thru two holes would prevent bind and increase adjustment. Don't think I explained it well so here is a modified picture. I think you are doing a really nice job working your way thru this and finding what "can" work and "how" well it can work. I wouldn't attach the clutch linkage pivot to the tranny, I'd just support the outer end back to the frame. Then if you ever have to pull the trans, you don't have to deal with the bracket on the trans. I'd moch the exhaust before you finalize the bracketry just in case you need to change something. Wondering why your clutch arm is so close to rear of bellhousing opening. Maybe a longer pivot ball inside the housing might increase the clearance, and maybe add leverage.
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