Rudder pedal sanity check

I was building up my in-flight adjustable pedals and ran across an issue I wanted to run by those who have gone before me.

Drew the center point for the brake master attach point on each brake.
Set the pedals up so they were even and upright.
Put a steel rod through the two inner pedal mounts that goes through both pedals so the steel weldments are even and true to each other.
Set a large square against the table and clamped the lower pedals to it.
Using another square I set the upper pedals and clamped them as a set with a thick piece of wood.


When I mark where the brake master holes should go in relation to the desired 5/16" mark I was getting some strange results.

This is the left pedal. The black line is the desired 5/16" location. The red line is where the left master wants to be if I drilled the right pedal at 5/16"


No surprise the right pedal is exactly opposite. The black line is the desired 5/16" and the red line is where the right master wants to be if the left pedal was drilled at 5/16"


I scratched my head over this trying to figure out how that could happen. I measure and checked the pedals, brake masters, lower pedals etc trying to find what was out of whack. Turns out the brake master attach tabs on the WD-816 rudder slide are not even.




So now I know what the problem is. The question is how to proceed.
My gut reaction is to drill the left pedal at the stock 5/16" so the right pedal gets drilled slightly higher up. Going the other way with the right pedal stock and the left pedal down leaves I believe an insufficient edge distance. My question about that is will there be any strange brake force issues? I can't imagine there would be enough of a difference to notice but that is why I am asking.
Thoughts?

Your gut reaction is fine

If you drill them as you propose, it will be fine. You will have slightly different pedal effort for the same braking, but you will automatically compensate when braking - doing what is needed to go straight while slowing down.

Also, if you drill them both at 5/16, and the two pedals are then not quite in plane, I think that would be fine too. I don't think you'll be able to tell with your feet.

Or, you could split the difference -- make them slightly out of plane, and have just the smallest difference in braking geometry.

As an example of how insensitive we are to slight asymmetries, I have a little bit of air in my right brake circuit so it is just a tad spongy. The left one is hard as a rock. In operation, I can not feel the difference.

weld & redrill

Can't disagree with Steve's analysis. 3/32 sounds like a small difference, but may be noticeable.

Do you have a granite slab to repeat the measurements on? How true is the wood benchtop?

TIG weld the low hole closed, grind bead flush, drill undersized hole in correct location, use chainsaw file to adjust location if needed, up-drill to final size..
Important to keep both moment arm lengths equal when redrilling, not just the vertical height.

OK

It has been a while, but as I recall ours was not quite this far out of true. So all we did was put the tab in a vice an gently bring the high one down to match the low one, then stop and put the master cylinder back on then drill to the peddles so they both matched at the longest travel of the cylinders.
No big deal either way you will be fine. Hope this helps. Yours as always.
R.E.A. III #80888

Just drill them on your red marks...... Edge distance is not an issue here. Load and wear on the holes will be on the top of the hole.

I'm a noob to RV's but would think also that it doesn't matter where the holes land on the peddle.

That said, if you go with the pre-determined 5/16th measurement, one cylinder will not have full travel (difference between black and red tick marks), which should be no problem once the lines are bled out. You will likely only use 50 % of the overall travel for either pedal for full braking.

Welcome to VAF!

Raymo said:

I'm a noob to RV's

Click to expand...

Ray, welcome aboard the good ship VAF

Mike S said:

Ray, welcome aboard the good ship VAF

Click to expand...

Thanks! Should have an RV7A in the near future. Just needs assembled and finishing kit. Can't wait!

Rudder Pedals

I just replaced my pedals after 1400 hours of flight when I found the holes in question worn vertically 3/16 of an inch. I couldn't tell the difference when flying the Doll. The new pedals corrected the worn holes and I still can't tell the difference.

If you split the difference between left and right, I'd bet you won't be able to tell the difference.

And if you want to, you can buy Grove adjustable master cylinders, and you can adjust out any difference, and make the pedal angle to your liking.

Love my adjustable Grove cylinders!

I thought I read somewhere that the Groves are good stuff but they are larger and thus you end up not being able to have the pedals full forward. That is not an option for my long legs.

Interesting observation Danny, Thanks.