Projects Let’s Redesign A Brake Pedal Arm or Not?

Not exactly what I call ideal. Let’s correct the lower over centered push rod lever then increase upper pedal arm ratio from 5:1 to 6.5:1 and make this follow the toe board a little better.

 

Is the pivot rod the pedal turns on even parallel to the master mounting plate? Looking from above? Doesn’t seem so in the pic, but may be an optical dillusion.

 

Move the pedal pivot forward.
That way the pedal will be pointing back at you & not up to the sky.
That will correct the over center problem too.
When I do pedals & floors in '32's I elevate the toe board.
I just put a 1 1/2" or 2" spacer (what ever works best) on the toe board ramps & then build the floor.
This does a couple of things for you.
It improves that little toe board "pocket" area between the kick panel & the trans hump,
where the pedals live.
Makes locating & operating the throttle pedal a lot nicer.
Makes the trans hump smaller too.
Basically it gives you more toe board & less trans hump.
And that 2 inches your giving up . . . you'll never notice the difference, but your pedals will be happier, and so will you.
My 2 cents worth . . .

 

It all lines up fine. It’s just the way the photo came out. Also that’s just a 1/4” plywood push rod as mock up.

Not moving it, I’ve cut and relocated enough stuff as it is due to interference.

 

Got angle of frame to toe board settled. Here’s the lay out.

 

Johnny Gee
At least look at elevating the toe board .
I think you'll see it gives a better result.

 

Why would I want to make truck cab even tighter?

 

Much better.

 

That’s it for now. Only a profile design and check. When cab final goes back down on the frame and steering column is set will I modify the arm. It may need a Z bend to get pedal from left to right in the proper position.

 

What's that done to the pedal ratio?

 

Just makes it easier to apply the brakes. It’s still within spec (5:1 to 7:1) for manual brakes with a 1” bore master. But that’s not the reason for doing it. I did however take advantage of it since pedal pad would be too low down the toe board because pivot point/shaft was welded in the wrong location (by someone else) to begin with.

 

Looks great now. Should be a much easier pedal ratio to push with. Are you going to adjust pedal angle more vertical to get the pad pointed more towards the driver's foot?

 

Have you checked the stroke of the master cylinder, so that you get full travel just before the pedal hits the floor?

 

Vertical? I will most likely move it horizontally to the right as I’ve already mentioned 3 comments above your like.

 

Once I get a proper push rod I will be checking that.

 

Not saying you have done anything wrong .. the opposite is true. Many miss pedal ratio as friendly and the correct thing to do. That said a 7/8” will be even less foot pressure and not throw you thru the windshield even at 7-1.

 

return spring
brake light switch

 

On loan from the part’s store. Which will it be?

 

Look’s like SLS40 wins over the SLS43.

 

Push rod still has not arrived but I did some number crunching. Master cylinder has 1 1/8” of travel until it bottom’s. That will make for more travel than what the arch on the lever can handle especially when I factor in floor thickness. So it’s back to 5:1 ratio but will still retain 13” radius that 6.5:1 cardboard pattern gave me. To compensate I’ll increase the radius of lower lever from 2” to 2.600”.
2.600”x 5 = 13”
1.1875”(lower lever travel) x 5 = 5.9375”(of upper lever travel). Arch has 7.25” of travel available.

 

^^^^^ So, can a push rod handle .600” of droop over an approximate length of 8.875”? Or do I lower the master cylinder by .600”?

 

Johnny
Does the MC piston have a shallow pushrod seat, if so, I don't think .600 is too bad.

 

@DDDenny no, it’s a manual unit with a deep socket.

 

With a deep socket the push rod may hit the edge of the piston at the end of the stroke. I would drop it to try to keep the pushrod as centered as possible. This will also cut down on wear of the master cylinder bore.

 

How high will the pedal pad actually be above the floor when its all the way up? Friend stopped by yesterday to show me his 56 Chevy truck. He had converted to a hydrostop brake setup and put an aftermarket pedal in it. It worked great, but the pedal ended up being too far from the floor and uncomfortable for normal driving. Its a simple fix, as all he has to do is remove the pedal and bend it so its lower. Most brake pedals don't use the floor as a reference as to when to stop....but stop maybe an inch or two above the floor. I'd look at having your pedal stop a little further from the floor, but also check how it "feels" when its all the way up and you are in the seat.
I think Pete Eastwoods suggestion to move the pivot forward is worth considering, and it looks to me like moving it down slightly would correct the over center problem, and lower the pedal closer to the floor. Anyway, I may be wrong but I think you are solving one problem but maybe creating another one.
Looks like you are doing a nice job fabbing things up, just looked like your pedal may be kinda high.......but might just be how it looks in the picture.

 

I used a brake switch similar to yours from a company called Preco. The part number was SW-3 and the lever was a spring that gave it some "forgiveness" so that you did not to be exact. Anyone know if they are still available? I searched for the name but nothing comes up so Preco might have been bought out by someone. Those switches came in handy, but the Standard switches you show will work out great.

 

p.s. yo know you can get a 'long' 3/8ths clevis
so IF you have more meat about the fulcrum it clears

 

Moving the pivot shaft won’t get pedal pad up higher on the toe board which is goal #1.

 

And there is all this tubular X structure in the way to deal with as well. Which would mean if pivot were moved forward a 12”-13” push rod would be required. No deal

 

Easy switches to use.