The "race pedal box"

[Lee]

So. After testing a first set-up. Leaving it there for a few months. I came back with a few more ideas to make the system much simpler to fabricate.

Instead of the two-line aluminum MC, I elected to use a very short Tilton serie 75 master cylinder. It is not only shorter, but it also has vertical mounting holes. Great for clearance.

Basically, you need a stock pedal box. Then cut the upright. Drill a 1-3/8" hole with a holesaw at the same horizontal level as the clutch MC hole, and vertical to the upper losange hole that is where the brake rod used to go. Both previous measurements will ensure that you are aligned with the brake pedal and at the proper pivot point level.

The brake pedal's pivot point will be drilled at the same height as on the clutch. Which will yeld a 6.1:1 lever from the original boosted 4.3:1

Cut the extra length in the input rod. Drill the clevis and use an helicoil to adapt its M8x1.25 thread to the rod's 5/16" UNF

When the test fit is done. Then simply weld a reinforcement plate on the cluster, and cover the oval hole at the same time.

Al that is left to do is to weld a tab to adjust the brake pedal height and an inline hydraulic switch for the brake light. What you see on the picture below is basically as you need to fabricate a racing pedal box. I went with a 1" MC as the same MC feeds 4 calipers. I may go bigger...

To eliminate any play, I will mount both pedals on needle bearings, and use a rod end for the brake MC.

[Tommy]

Is that still dual circuit? Single circuit brakes would sound a bit hazardous. Just curious.

Tommy

[Lee]

Is that still dual circuit? Single circuit brakes would sound a bit hazardous. Just curious.

Tommy

Dual circuits are vintage systems from the 1960s to the late 70s. The common current masters use two outlets, each one pushing fluid to the front, or the rear. But if either front or rear line fails, the whole system fails.

Therefore I absolutely no problem using a master feeding the whole system.

Lee

[Mike_B]

Very nice work, Lee!

If you email Tilton with the specs of your brake system and car, they will spec a master cylinder free of charge. It may be a bit easier than trial and error...

[Lee]

Very nice work, Lee!

If you email Tilton with the specs of your brake system and car, they will spec a master cylinder free of charge. It may be a bit easier than trial and error...

Thanks for the info.

I know of a few people who have entrusted Tilton and Wilwood for sizing "proper" MCs. In all cases they were sized for gorillas. Therefore I prefer using my own judgement.

[TobyB]

Yup- Tilton's pedal feel is very very aggressive-

as in, if you don't stomp on it, it don't stop.

That's actually great on a race car, especially when

you go to real racing pads that tend to be very aggressive.

Not so good for anything else.

My sanction requires a dual braking circuit for any racing car.

I dunno about the SCCA.

t

[Lee]

My sanction requires a dual braking circuit for any racing car.

I dunno about the SCCA.

By dual circuits, I suppose you mean the original system as found on 2002s and e12s. Because if a master cylinder has two outlets, it is still a standard single circuit with no back-up. With car on jackstands, press the brake pedal and have somebody open any bleeder. The brake pedal will depress while the whole system is down and won't brake at all. No back-up circuit. So, weither the master cylinder has one or two outlets, it remains the same.

[Mike_B]

Email me Lee and I'll give you my contact.

IIRC, he stated that they typical Tilton calculation is based on a 100lbs of force, while a typical stock setup with a booster is around 40lbs. I always ask him for a calc with around 65lbs.

[Lee]

Email me Lee and I'll give you my contact.

IIRC, he stated that they typical Tilton calculation is based on a 100lbs of force, while a typical stock setup with a booster is around 40lbs. I always ask him for a calc with around 65lbs.

I will stick to stock force if possible. Masters are cheap and easy to replace. Therefore I will experiment.

[Mike_B]

Cool... I'm very interested to see what size you end up with.

[TobyB]

Actually, no, they specifically allow split masters

front/rear with a bias bar. Or any stock system. The

requirement is that when one master bottoms, the

other can still apply braking force on the wheels.

Now, flying down the hill at SIR into 3a, just about the

last thing I would want is only rear brakes... but the

rule's there....

t

[Lee]

A new small plate to hold the MC has been drafted and sent for laser cutting - 20 units done from mild steel. It will make installing the MC very easy. In the meanwhile I have started drafting an excentric throttle cam that will be located either inside the box, or on the side. I have to verify the linear pull for the S14 throttle lever and see if it matches the throttle cam. Then will make a few mock-ups to verify pedal movement.

[Lee]

Here are a few shots with paper mock-ups.

[Lee]

Twin chamber MC also available. Same mounting specs.

[Harv]

That's the way to go Lee. Just imagine, hard on the go in the down hill right at LRP just creeping up on that (whatever...) and no brakes for Big Bend. Gotta at least stop at some point without hitting something hard.

Pedal box looks great!

John