Dual Circuit Master Cylinder conversion for TR-4
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This arrangement uses the stock, unaltered pedals.
Bracket and Linkage
Here's some overview pictures:
Here's a couple of closeup shots of the front support bracket. This is needed to hold the linkage up while the brakes are not engaged. What's interesting about this setup is that when the brake pedal is pressed, the linkage rises up off of the support and is suspended in mid-air.
Here's some detail shots of the linkage. The clutch is just a chunk of pipe cut to length with a long bolt. I worried that there would be flex in this setup, but it's rock solid.
Here's a couple of shots of "balance bar" pieces. I've got several with the center hole in different places. The closer the center hole is to a given master cylinder, the more force goes to that cylinder. This seems much more in the vintage spirit than the cockpit adjustable arrangements. The shot from above is out of focus, but you can see the difference in the center hole. Changing balance bars takes less than 5 minutes.
The brake master cylinders are Girling remote reservoir 5/8" (0.625") units, sourced from DRE (the Formula Vee folks) at the time. The clutch master cylinder is a stock type unit. Firewall clearance is an issue, so they need to be short. Since I made this setup, Tilton came out with "shorty" cylinders that would probably work too. The 5/8" cylinders give good pedal feel - I don't have to stand on them TOO hard to lock wheels, and the brake pedal moves an appropriate distance - I can still heel and toe. Going larger on the master cylinders will make the pedal "harder" - it reduces your mechanical advantage. So the pedal doesn't move as far and feels harder - it should be harder to lock a wheel that way, but it will also reduce the "feel". I used remote reservoirs left over from a Tilton pedal installation.
The master cylinders I used are now available at Pegasus here (Pegasus part number 3502-.62, although you could go with the -.70 or -.75 if you desire). Clevis pin bracket is here (Pegasus part number 3576).
It looks like either this Tilton (Pegasus P/N 3506-.62) or this Tilton (Pegasus P/N 3507-.62) master cylinder would work, although clearance between those master cylinders and the stock clutch master cylinder may be an issue.
Remote reservoir parts are here and here (Pegasus P/N's 3557 and 3558-SMALL). I used the small tank. I forget where I got the barb fitting for the inlet on the master cylinder, but this one from Pegasus (part number 3207) looks like the ticket - pricey, so you may want to shop around. It needs this or this sealing washer (P/N's 3245-7/16 and 3241-7/16).
The brake light switch is from a Honda (don't remember the part number). Went through a couple of Chevy ones, the Honda part has been rock solid. Go figure.