Corvette rear end - parking brake problems

[Texrodder]

My 33 Chevy rod has an early Corvette rear end installed that has disk brakes for normal braking.  It has drum type brake shoes mounted inside the rotors to serve as emergency/parking brake.  I am using a Lokar floor mounted brake lever to actuate these shoes but cannot get the parking brake to hold.  Problem seems to be that the short handle on the Lokar brake lever does not give enough leverage to give enough force to set the brake shoes.  Someone has suggested installing a bell crank mechanism to increase braking force.  I'm sure that others using Corvette rears may have had the same problem and I would like to hear how they solved this problem.  Thanks in advance for any suggestions.
Don

[58 Yeoman]

Okay Don, let's try this again.  This is how Pontiac did it in 41. Crude, but original. Maybe you could design something similar to give you more leverage? This one is just a simple lever through the frame on one side, hangs on the other end. The rear cables connect in the middle, and the front cable connects to the hanging side.

[Bob Paulin]

My 33 Chevy rod has an early Corvette rear end installed that has disk brakes for normal braking.  It has drum type brake shoes mounted inside the rotors to serve as emergency/parking brake.  I am using a Lokar floor mounted brake lever to actuate these shoes but cannot get the parking brake to hold.  Problem seems to be that the short handle on the Lokar brake lever does not give enough leverage to give enough force to set the brake shoes.  Someone has suggested installing a bell crank mechanism to increase braking force.  I'm sure that others using Corvette rears may have had the same problem and I would like to hear how they solved this problem.  Thanks in advance for any suggestions.
Don

It is likely that your hand-brake lever cannot supply enough leverage to apply the e-brake shoes with enough force.

I believe what Phil's post illustrated is a simple Class "B" lever....which provides a mechanical increase of force, while keeping things all moving in the same direction as opposed to a Class "A" lever which reverses the direction of the input force.

That would be, basically, a flat bar with three holes.

The hole at one end would serve as the fulcrum for the lever, while the force from the hand-brake lever would be applied to the hole at the opposite end.

The hole in between would be attached to the cable going back to the rear wheels to supply the "work".

You could move the hole in the middle closer to the fulcrum and/or closer to the force to provide more/less mechanical advantage and/or more/less cable travel.

The closer the "work" load is attached to the fulcrum, the more force you will apply through leverage for a given hand brake lever "force" input, but, also, the closer the "work" output is to the fulcrum, the further the input "force" will need to travel for the same amount of "work" output cable movement.

You should be able to find a happy medium there somewhere.

Start with the "work" output hole in the center and move it towards the fulcrum for more leverage and e-brake application force or towards the "input force" end for less hand brake lever movement.

You might need to lengthen the hand-lever bar to accommodate more travel distance....but, maybe not.

Bob Paulin

[Bruce Dorsi]

Yes, you may have a leverage problem in that your set-up does not provide enough FORCE to properly activate the e-brake.

Or, is it that the Lokar handle does not provide enough TRAVEL to fully activate the e-brake?

If your handle pulls all the way, but the brakes do not hold, you probably do not have enough travel, or throw,  if they are properly adjusted.  ....If your handle moves only part way, but the brakes do not hold, then more force needs to be applied.   Pulling harder on the handle should allow the brakes to hold, and prove if this is the problem.

Have you checked to be sure that the brake linings are not glazed or worn excessively?  .....Is the surface inside the drum too smooth?  .....Is there enough contact area between the linings and drums?

CRS  :oops: prevents my remembering, but I don't think these e-brakes are self-energizing.  Or are they?  ....If they're not, they will require more force to hold.

[Texrodder]

Thanks guys for your comments.  I have checked the shoes and they look like new - even scuffed them up a bit to make sure that glazing was not a problem.  The drum surface that the shoes mate with is clean with a good surface so don't think that is a problem.  The lever apparently actuates the brakes OK since I have adjusted the cables to the point that you can see that the outer covering of the cables is compressing.  I have come to the same conclusion that you all have that there is just not enough force to apply the brakes.  (problem is aggravated since the diameter of the parking brake shoes is only 5 - 6").  Have already started thinking through a solution similar to what 58 Yeoman shows.  Looking in some old Corvette parts catalogs and may be able to come up with some ready made pieces to get this done.

[model a vette]

The stock vette setup (at least on the '68 I'm familiar with) has a compound action built into the brake handle. Basically it takes up the slack fast, at the start of the action, and then slows to multiply the action to apply the shoes at the end of the travel. I've used Gennie Shifter cables on my setup and it is just barely good enough to stop the car. My handle is an old Toyota floor mounted one. I may have to try using the bar method shown above to pass inspection in New Jersey.