Underfloor pedal of past member

[AltBantam]

I was searching past posts on underfloor brake and clutch pedals as I was wondering if they would give me a little more foot room. I found an old post from Hotrod46 from 2016. It was one of the last posts by Hotrod. He posted a photo of a homemade brake pedal which appeared to be made using a curved steel rod or tubing. He stated the rod traveled through a hole drilled into the floor. The fact he has no posts after Jan. 2016 troubles me. The question I have, and maybe someone else knows, how to calculate the arc of the bend of the rod so the rod passes though a hole slightly larger than the diameter of the rod? At first I thought if might have to do with the arm length the curved pedal is welded to. But the arm appears longer in the photo. Perhaps it's an illusion. Any thoughts?

 

[HenrysT]

The arc's radius would be determined by the pedal's pivot point being used as the center point. The length of the straight section of the pedal and the length of "arm" coming off the the pivot point to the link going to the MC will determine your ratio.

 

[AltBantam]

That doesn’t sound like English but I understood it. Thanks.

 

[Spanky]

 

[thebearded1]

I like that idea! I guess the important thing is to make sure the curve portion of the pedal is perfectly curved but that would be really neat to only have a small hole in the floor versus a slot.

 

[thebearded1]

Also important that the straight part of the pedal is welded at a 90 degree angle to the end of the curved part. You could always test it by clamping a screwdriver to the frame and have it pointing at the curved arm then depress the brake pedal to ensure the screwdriver is always lined up with it through the range of travel. That way you could just tack it and test it without a floor

 

[HenrysT]

you can lay it all out on a piece of plywood, then use the plywood as a pattern to assemble and weld the pieces together on.

 

[Gerry]

A few more pics.
Brake pedal was made from 8mm thick sheet and worked with a power file. I have a ratio of around 9:1 as a servo increases the preassure by around 1.4 times.
The normal ration of 6:1 x 1.4 gave me the lenghts. Thats one reason fro the 8mm plate and the welded foot plate. Works just great.
G

 

[AltBantam]

Thanks. I did plan to make a mockup using cardboard but I have some 1/4" plywood, that would be sturdier. Last night I calculated pedal length for ratio using a 1 1/2" m/c rod mount for both a 6 to 1 and 7 to 1 setup. I also attempted to calculate pedal travel with up to 1 1/2" of m/c piston travel. Not sure if my numbers were correct. The mockup should answer that... The bending of the pedal so it has a constant arc will be the hardest part. I don't have a bender. There are some at work though. I'm not sure whether to use tubing or round stock. Either way, I am thinking 3/8" thickness. 1/4" sounds too thin. Or I could use plate. If I have find some 3/8" x 3" or 4" wide plate, I can cut out curved sections with my plasma cutter then weld it together. Little grinding and it would appear one piece. I was thinking about whether or not to run the pedal through the floor or firewall. Through the firewall might interfere with the steering more than the floor.

 

[LongJohn]

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Brake Pedal Kits