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Pedal Mod

DanH

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The -8 is different in many ways, including the pedals. Note how the master cylinder rod is attached. It's an AN-3 cantilevered through a .125" thick tab on the pedal. It can't be tightened, as that would lock rotation when the brake was used. So, the only thing keeping it 90 degrees to the rod is the hole through the rod itself.

Master Cylinder Bolt.jpg

The combination of forces is hard on the hole in the pedal. And the material is soft; welding turned the 6061-T6 into 6061-0. So over time, the hole can get elongated..."wallered out", as we say in the South. It still works, but it adds slop to the system.

Brake Bolt Holes.jpg

Here's an easy fix. I used a length of 3/4 x 3/4 x 1/8" 6061-T6 channel from the scrap bin. Principle is spreading the bolt bearing load onto more and stronger material, at points farther apart. A solid block 3/4" thick would also work, attached with two tapped screws where you see rivets here.

ScreenHunter_2557 Dec. 07 21.26.jpg
 
The -8 is different in many ways, including the pedals. Note how the master cylinder rod is attached. It's an AN-3 cantilevered through a .125" thick tab on the pedal. It can't be tightened, as that would lock rotation when the brake was used. So, the only thing keeping it 90 degrees to the rod is the hole through the rod itself.

View attachment 75937

The combination of forces is hard on the hole in the pedal. And the material is soft; welding turned the 6061-T6 into 6061-0. So over time, the hole can get elongated..."wallered out", as we say in the South. It still works, but it adds slop to the system.

View attachment 75940

Here's an easy fix. I used a length of 3/4 x 3/4 x 1/8" 6061-T6 channel from the scrap bin. Principle is spreading the bolt bearing load onto more and stronger material, at points farther apart. A solid block 3/4" thick would also work, attached with two tapped screws where you see rivets here.

View attachment 75943
Besides the hole getting wallered out, the condition is what leads to master cylinder wear and scoring and ultimately failure. Great fix Dan!
 
Problem noted. My fix used a jam nut and thin washer to replace the 3 washers in the picture. Whatever the fix, the goal is to make the bolt a fixed axle rather than a floppy one. No more master cylinder repacking...yeah!
 
Great fix. I did something with a similar outcome when I built my 6A as I didn't like the pivot bolt not being held tightly by one member. I don't have any pictures, but I used small bronze bushings in such a way that I could tighten the bolt down onto the bushing, leaving the pedal free to rotate on the pair of bushings. Still trouble free after 1850 hours.
 
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