New project

enjenjo · July 06, 2011, 10:48:02 PM

My buddy with a body shop sent a truck to me. A 68 to 72 Chevy stepside, chopped, sectioned, and severely modified all around. It's tubbed with 21" tires, and a serious small block in it. He just fixed the front end, it was smashed up when the brakes failed. I am fixing the brakes.

The brake pedal is under the floor. The brake pedal has an old spring eye as a pivot, and the pedal, which is outside the frame, is bent to a lever that is inside the frame, with a bellcrank welded to the other end of the pivot shaft outside the frame, also pivoting on an old spring eye welded to the frame.. There is a rod connected to this lever, about 12" long, that goes to a second bellcrank, on another spring eye, that transfers back to the inside of the frame, to a second rod about 3ft. long, to a third bellcrank that finally transfers to force to the master cylinder. All the ends on the rods have 1/2" holes, and all the pins are 3/8". The pushrod in the booster to the master cylinder was "modified" with a cutting torch. The overall pedal ratio is 2 to 1. There is no proportioning valve, no combo valve, no residual pressure valve.

I wonder why the brakes didn't work. Pics tomorrow.

ragdol · July 06, 2011, 11:58:52 PM

Is the owners name Rube? Build a big motor, customize to the max, & can't do a decent job on the brakes. I'd suspect there are some other things that aren't up to spec too. Some people.

unklian · July 07, 2011, 12:51:46 AM

Did the same guy modify the rest of the truck ?

Charlie Chops 1940 · July 07, 2011, 06:58:50 AM

I'm anxious to see the pics. Sounds like waving a stick in the general direction of the master cylinder might have been just as effective.

Charlie

GPster · July 07, 2011, 08:50:50 AM

I always wondered if you could use the pedal to work a small cylinder to operate a slave cylinder that pushed the rod on the remote mounted power brake diaphram for a normal from that point. Then I'm always behind on this new technology. There's accelerate by wire and power steer by wire, somewhere someone probably has brake by wire. I assume this is the first time you've worked on this vehicle. GPster

kb426 · July 07, 2011, 07:17:07 PM

The brakes failed!!! No S**T!! Wow. I'm sure you'll fix it. Ought to be a good story when you're done.

enjenjo · July 07, 2011, 09:14:50 PM

Ok, here are some of the old brake parts. I'll post pictures of the new stuff as I make it.

jaybee · July 07, 2011, 10:56:49 PM

Great looking truck--from the top side. As far as the brake system is concerned you could probably point just about anyplace and say "don't do that." Ignoring the "workmanship" I can't help but ask--why make it so complicated?

GPster · July 08, 2011, 09:55:18 AM

Quote from: "jaybee"Great looking truck--from the top side. As far as the brake system is concerned you could probably point just about anyplace and say "don't do that." Ignoring the "workmanship" I can't help but ask--why make it so complicated?

I would imagine that when they sectioned the cab it put the stock pedal rubbing on the floor and the power brake diaphramin the valvecover. That and with an under the floor replacement pedal they had no way to get a decent ratio because the sectioned cab brought the bottom of the dash too close to the floor. Maybe this is a place for one of those Kugel sideways-under the dash pedal set-ups. Of course we're only seeing what doesn't work. GPster

jaybee · July 08, 2011, 11:48:26 AM

That makes sense, and some are putting brake m/c under the floor just to get a clean firewall--but why do it with multiple pushrods and 3 bellcranks? Way too complicated for a problem that could have been solved with a pedal, a pushrod of "some" length, a bracket to hold the booster/mc assembly, and a return spring.

wayne petty · July 08, 2011, 12:52:53 PM

some forward thinking.... that might be a big help later..

i would imagine that its still going to have vacuum assist power brakes..

i recall that there is a new style hydroboost type that is self contained.. with a built in electric motor to supply hydraulic pressure for the assist...

my thought is if its vacuum assisted... that a vacuum reserve tank is also needed.. and a few vacuum switches that operate tiny super bright LED warning light indicators on the cluster.. so he knows when there is NOT enough vacuum...

the vacuum switches are set to different pressures. to operate different colors of the LED or different LEDs.

this is all my version of a rube fix...

UGLY OLDS · July 09, 2011, 10:45:46 AM

Like JayBee said..... Great looking truck ....From the top...

Can we start a "What Not To Do" Tech section :?: ( Altho that one bracket seems to be "infinatly adjustable" ....hmmmmm

)

Bob...

enjenjo · July 12, 2011, 11:45:08 PM

Here is what I have done so far. I made a brake pedal pivot out of tool steel This will be bolted to the side of the frame to support the brake pedal with four 3/8" bolts into nut plates.

I then made a new brake pedal out of 3/8" steel, with bronze bushings and a grease fitting to fit the new brake pivot. Pedal ratio is 4.6 to one. Some more work needed on the pedal, drilling for the brake pushrod, and some smoothing out. The top 2" of the pedal came off an old Chevy brake pedal. it's serrated, as is the pedal stem, to keep it from moving. I also have to add a stop bumper for the up position.

I am making a booster bracket that will bolt to the side of the frame, near the rear axle. This has a bellcrank on it that will support the end of the pushrod, and the brake booster rod, so there is no lost motion. This is also bronze bushed. The booster bracket will get some more bracing before it's done.

GPster · July 13, 2011, 08:46:51 AM

I don't think I could turn out work that nice even with an air conditioned shop. Is this vehicle a driver or did he damage the front end because it rolled to far foreward on the trailer? GPster

kb426 · July 13, 2011, 05:35:03 PM

What do you use to cut parts with? Plasma, torch, laser?