Rudder pedal placement

[DBeaulieu]

I'm a bit short-legged and likely will have to move the pedals or extend the rudder/brake pedal system further aft. I was wondering how much leeway there is for relocating when starting from the QB kit. Thanks so much any insight and comments regarding the question.

Dave

[jaredyates]

Hi Dave, in years past, some folks encountered a problem with the rudder pedals when they were installed contrary to the plans. It was possible to create an over-center condition with the brake system. The key takeaway is that the ruder pedal position as drawn on the plans isn't negotiable. Here is some text from a 2010 discussion:

A couple weeks ago I tried to bring to your attention a possible problem that results from locating your rudder pedals further aft than what the plans show without moving the attach point for the master cylinders aft also. Basically, you can end up with an "over center" brake pedal that is difficult to get out of a "locked" position of full pedal. The geometry of all this has to be right.

FYI - the plans show the rudder pedal assy to be 4" aft of the center/bottom firewall tube. If you placed your pedals close to the four inches, this should not be a concern for you. But if you moved the pedals aft intending to be able to reach the rudder pedals better (if you are shorter), then this is important.

Attached are two pictures. One shows the brake pedal locked in an over center condition. The other picture shows a super simple fix to prevent it from happening by placing a clamp to limit travel somewhat of the brake pedal.

This was investigated by scratch builder Kevin Deutcher in Phoenix who takes an engineers approach to investigating and solving problems. Bob Barrows reviewed what Kevin came up with and thought it was a good easy fix. Thanks Kevin for your time and effort. Mark

The problem is that if you move the rudder pedal attachment aft, the brake cylinders still attach at the same tabs, and that alters the geometry of how all of those parts go together.
There are some solutions to prevent this condition, including moving the brake cylinder attach points aft, and the clamp method mentioned in Mark's text above. Sadly I don't have access to the attachment that he references.

This is one of those cases where a deviation from the plans warrants a discussion with Bob.

[Mark Goldberg]

While there is a LITTLE flexibility in positioning the rudder pedals - it works to make the seats in your plane the best way to position yourself to best push the pedals. By the amount of foam you use on the seat bottom and seat back. Mark

[DBeaulieu]

Thanks for the quick response. and replies...I was assuming everything would have to be moved as a system (pedals and brakes) to maintain geometry. Would rather use seat cushioning as a solution if possible, but also don't want my "face to panel" distance decreased significatly either

[kestrel]

I don't know how mine might be different, but at full rudder pedal deflection, if the brake on the "rearward" pedal was pushed, you could create an "over center" condition. Following someone else's idea, I put a worm gear clamp around the shaft of each rudder pedal. The big fat worm gear was placed so that it limited how far the brake pedal could be pushed and prevented the problem. It doesn't effect normal operation. It would be very strange to push full right rudder and full left brake at the same time.

[Bcone1381]

Would rather use seat cushioning as a solution if possible, but also don't want my "face to panel" distance decreased significatly either

SO, if you wanted to move yourself closer to the rudder pedals, but the instrument panel is too close to yourself consider pushing the panel forward towards the firewall. That would be a simple task. There is a structural steel tube that goes across the fuselage at the base of the panel, and moving the panel face a few inches forward would give you a wider "shelf" at the base of the instrument panel. That would be a plus.

[DBeaulieu]

I like the idea of moving the panel closer to the firewall. Thanks!

[stinger]

Dave, I suggest you look at Van's aircraft . I built a RV8 of which I installed moveable peddles. Van's sold these as an option and they worked GREAT. If I wanted to I could slide the assembly forward or aft, take a look at them. Stinger IMG_0179 (2).jpg

[kestrel]

I can't seem to see the rudder pedals in that RV-8 picture...