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RV-8 rudder pedal mods

billdianne

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I know of two mods for the problem of applying a little brake when wanting only rudder deflection.

One is to replace the the pedal attachment bolts with one long bolt across the face of the pedal.

The other is to add small extensions to the bottom of the pedals.

For people who have done one or the other, how has this worked out? And would you prefer one method over the other?
 
Hi Bill,
I might get corrected on this but in my very very humble opinion, I would leave the pedals stock. I have never had a issue with inadvertent braking but I have had a time or too when I needed brakes NOW, and I personally like being able to quickly give a tap or two of brakes in a strong crosswind. I have overheard conversations where ground loops have happened and the pilots have quietly wondered if they had had better access to the brakes the ground loops might have been avoided???
Its all personal choice All the Best
 
I know of two mods for the problem of applying a little brake when wanting only rudder deflection.

One is to replace the the pedal attachment bolts with one long bolt across the face of the pedal.

Actually, the long bolt is a fix for the brakes sticking. The long bolt forces the pivot holes to all align up on a single axis----and the two bolt set up can have the axises at a slightly different position, causing binding in the pedal motion.

The master cylinder return spring is pretty weak, and a little binding can prevent total return of the piston, which is needed to un-port the pressure relief.
 
Leave them stock

I agree with Kirk Groves. I have over 500 hours on my RV-8 with stock rudder peddles and I have had no problems applying brake when I just want rudder. I think that stock peddles work very well. I wouldn't change a thing about them.

Dan Miller
 
Actually, the long bolt is a fix for the brakes sticking. The long bolt forces the pivot holes to all align up on a single axis----and the two bolt set up can have the axises at a slightly different position, causing binding in the pedal motion.

While this is a true benefit of the single bolt mod, most people that do the mod (as I understand it) are trying to prevent the inadvertent braking that can come from pressing on the pedals with the factory geometry.

I have pedal extensions which I installed before I flew an -8 (based on Randy Lervold's design). I have also flown -8's with stock pedals. I like my pedal extensions because they fit the geometry of my ankles and feet - I fly with my heels on the floor, and the tips of my toes on the extensions. I have no problems with sliding my feet up to tap the brakes when I need them - but again, this is very, very dependent on your personal foot geometry.

Fortunately, the rudder pedals can removed with about an hour's work through the forward baggage compartment, so you aren't stuck with how you do them if you decide to change later on. Experiment until you get them right!

Paul
 
While this is a true benefit of the single bolt mod, most people that do the mod (as I understand it) are trying to prevent the inadvertent braking that can come from pressing on the pedals with the factory geometry.

Paul

Paul, the geometry does not change when going to a long bolt. Same pivot point, same throw, ETC.

Just corrects any misalignment that may have crept in due to two bolts being used.
 
Bill:

My 2 cents is the issue is the master cylinders not the pedals. Some (like me) have had master cylinders that tend not to fully release and thus drag the brakes. Most posters seem to agree that it is due to weak return springs on the Matco cylinders. No matter how I positioned my feet on the pedals including tips of my toes only on the lowest point of the rudder bar, I still had the problem. I changed to the Grove replacement cylinders and haven't even thought about it since.

Chris
 
O.K., perhaps I spoke too soon---------should know better than to disagree with Paul:rolleyes:

I was looking around in the archives for photos of the long bolt fix. (scroll down to post 3). And I ran across another thread that shows a -8 setup.

It appears that the 8 is not like the units posted in the above link.

Is the pivot bolt/bolts in front of the pedal in the 8, or is this just a weird angle that makes it look like it is in front???

http://img147.echo.cx/img147/8898/rv8pedmodwithrollerbarmockup2t.jpg
 
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It appears that the 8 is not like the units posted in the above link.

Is the pivot bolt/bolts in front of the pedal in the 8, or is this just a weird angle that makes it look like it is in front???

You're correct. In the RV-8, the pivot bolts are on the front side of the pedals. A long bolt doesn't change the pivot point, and doesn't significantly change the way your foot sits on the pedal. According to some people, it may help prevent "stickiness" of the pedal.

This a completely separate issue from the "inadvertent braking" / geometry issue.
 
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Thanks Buck.

You're correct. In the RV-8, the pivot bolts are on the front side of the pedals. A long bolt doesn't change the pivot point, and doesn't significantly change the way your foot sits on the pedal.

Thanks, learned something here.

Even with 60+ trips around the sun, still learning.
 
I think it may depend on which style of pedal you're using. I had this discussion with Danny King a couple of years ago and it seems to me that this problem of inadvertent brake application is more pronounced on the ground adjustable pedals. I have the ground adjustable (floor mounted) pedals on my -8 and they exhibit the exact same problem I had with my very early -6 which had floor mounted pedals. The geometry between the pivot point of the pedal and the base pivot point of the master cylinder allows for inadvertent brake when you apply rudder. The brake pedal is forced by the master cylinder to articulate back towards your foot. The more rudder input the further the brake pedal articulates back. Your foot is not able to bend back enough to avert applying brake pressure.

I installed Randy's extensions and like Paul I keep my heels on the floor. I can push the extensions with the balls of my feet and not apply any brake. However, it is quite easy to roll my toes forward and apply brake pressure if necessary. I agree with Paul, if you don't like the extensions they're very easy to remove.
 
Hey Rick!!! Laura saw your post and wanted to tell you hello from Bahama Mama:D



I think it may depend on which style of pedal you're using. I had this discussion with Danny King a couple of years ago and it seems to me that this problem of inadvertent brake application is more pronounced on the ground adjustable pedals. I have the ground adjustable (floor mounted) pedals on my -8 and they exhibit the exact same problem I had with my very early -6 which had floor mounted pedals. The geometry between the pivot point of the pedal and the base pivot point of the master cylinder allows for inadvertent brake when you apply rudder. The brake pedal is forced by the master cylinder to articulate back towards your foot. The more rudder input the further the brake pedal articulates back. Your foot is not able to bend back enough to avert applying brake pressure.

I installed Randy's extensions and like Paul I keep my heels on the floor. I can push the extensions with the balls of my feet and not apply any brake. However, it is quite easy to roll my toes forward and apply brake pressure if necessary. I agree with Paul, if you don't like the extensions they're very easy to remove.
 
Off topic....sorry

Hey Rick!!! Laura saw your post and wanted to tell you hello from Bahama Mama:D

Hi to Laura. You need to get that airplane of yours painted so we can head South. Winter's getting cold. Plus, I want to see you kiss your spinner again after flying over all that open water.

kirkandlauraonthegroundfw4.jpg
 
Mods

I have pedal extensions which I installed before I flew an -8 (based on Randy Lervold's design). I have also flown -8's with stock pedals. I like my pedal extensions because they fit the geometry of my ankles and feet - I fly with my heels on the floor, and the tips of my toes on the extensions. I have no problems with sliding my feet up to tap the brakes when I need them - but again, this is very, very dependent on your personal foot geometry.

Fortunately, the rudder pedals can removed with about an hour's work through the forward baggage compartment, so you aren't stuck with how you do them if you decide to change later on. Experiment until you get them right!

Paul

Ditto on Paul's thoughts on Randy Lervold's mod. I installed the extensions on my -8 before I first flew it.

You never accidentally get on the brakes. If you need 'em; they're right there. If you don't like them take them off.

I think you will like them tho.
 
Unintended consequences

If you put lower brake pedal extensions on your RV-8 pedals, you will not be able to stick your feet through the holes below the pedals, and stretch out your legs on those long flights. Before you do this mod, sit in your plane and put your feet through the pedals and rest your heals on the tubes.
I have flown three RV-8s with extensions including Iron's. I vote to not modify Van's design.
 
Bill,

Six years ago during the test period I noticed that the aircraft would almost come to a complete stop when I attempted to do a 180 on the runway. During subsequent flights I noticed that the aircraft accelerated when I took my foot completely off the opposite pedal during the turn. My big feet were causing the brakes to drag. I put a 1X1X1/8" aluminum angle on the bottom of the pedal with two bolts, so the arch of my foot would push on the horizontal portion of the angle. This meant that the force was applied below the fulcrum of the pedal and the brake rod was pulled up, not down. I believe the different opinions are the result of the fact that the standard geomerty works for some and some not. The angle works great for me. If interested email me at [email protected] and I'll send you a picture.

Jim
 
to all
many years ago I installed spacers (two inch nylon rod,drilled,split, then clamped to the rudder pedals) with much success,, when building my 7 I went with a set of the Cleveland pedals,,, I like them but they have two drawbacks, one, they are heavy, second and the worst, one can get a toe stuck in part of the pedal just when you need to get on the brake . don't ask.... but that was one ugly landing at 52f... thanks Rod I'm glad you a CFI
 
Bolt and tube

To each his own Mickey, but I like the single bolt set-up I went with very much. Keeps the area free to slide my feet under the pedals as some have commented, but in my case only to make it easier to push them back when resetting from my "short legged" partner. :) When I hit the pattern slide my feet up to allow quick brake access.

I installed a piece of stainless tubing just larger ID to allow the tube to spin.
 
To each his own Mickey, but I like the single bolt set-up I went with very much. Keeps the area free to slide my feet under the pedals as some have commented, but in my case only to make it easier to push them back when resetting from my "short legged" partner. :) When I hit the pattern slide my feet up to allow quick brake access.

I installed a piece of stainless tubing just larger ID to allow the tube to spin.
Thanks Wade - the bolt/tubing doesn't bother you too much when you have your feet up and need braking?
 
As someone that's also got the dragging brakes when using the rudder pedals on my RV-8 with the "adjustable" rudder pedals, is this still the current "best" way to fix the problem?

http://romeolima.com/rv8/IdeasProducts.htm#IDEA: Rudder Pedal Extensions

View attachment 17226

I built the Val’s pedals that way and flew it without issues for years. When Louise started flying the airplane, she didn’t like the extensions (didn’t;t work well with her foot geometry), so I just switched to standard pedals, standard mounting, and they have been that way ever since. To be honest, I don’t even notice the difference.

But remember…I fly so many different airplanes and types that I pretty quickly adapt to just about anything.
 
I built the Val’s pedals that way and flew it without issues for years. When Louise started flying the airplane, she didn’t like the extensions (didn’t;t work well with her foot geometry), so I just switched to standard pedals, standard mounting, and they have been that way ever since. To be honest, I don’t even notice the difference...

Thanks Paul - I thought I could adapt to ensure I was not pushing on the brakes as well, and perhaps I just have pedals mounted at too much of a rearward angle.

I've recently taken the time to "play" with the pedals a bit more and see if there is drag - and there is. I could not find a way to keep my feet "tight" on the pedals and not press on the brakes. Looking at the geometry, you will be putting force in the braking direction on the pedal except the very bottom edge of the 0.125" thick pedal.

I removed and checked the brake pad thickness, and they are at 0.1095" according to my trusty micrometer. Seems surprising to me that they would have worn so much with only 250 landings, and that tells me I am probably dragging them.
 
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The pedal geometry issue is different for various leg lengths and foot sizes. What works for Paul can't be expected for me; he's a sports car and I'm a pickup truck ;)

Long legs and size 14's mean (1) the knees are higher, (2) heels are more aft on the floor, and (3) the ball of the foot is higher on the pedal assembly. It does become difficult to stay off the brakes.

I've played with a few things, and the best Bigfoot Mod seems to be a short length of thinwall aluminum tube across the pedal, at the pivot line or a little below. Three pop rivets hold it from the back, so the mod is easily removable. The trick is to crush the tube into an oval shape to adjust offset thickness to accommodate your own ankle angle at rest. See the photo.

This mod does not interfere with sliding the feet through the pedal for leg extension during cruise.

While on the subject of pedals, I noted interference in the stock assembly at the lower mount for the brake cylinder. To eliminate interference at full pedal travel, the slot needs to be clearanced as shown, or the tab on the pedal mount needs modified. The inspection telltale is the paint chip at "A" because it hits in position "B".
 

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Another solution

This easy mod has worked well for me for ~20, 21 years. Drill out the outboard connection to .250+". Cut and install a section of .250" steel rod through the inner and outer connections. Use a locking shaft collar to restrain on each end. Add some thread locker to each for a little insurance. Sorry for the pic. It's the best I could find in my collection of on-hand photos.

Before - lots of dragging brakes and low pad life. With mod - no more dragging brakes. Very easy to feel the bar and know you're not applying brakes. Scoot your feet up to get more brake application "leverage."
 

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just another data point

just to add another data point, I made lower extensions similar to what Randy Lervold did. I bent them aft so that it changes the effective angle of the pedal to be less upright.

To me, this changed the pedal geometry from one that felt awkward, always feeling like my chin muscles had to keep pulling my toes back, to a geometry that feels totally natural. Braking when you need it, never by accident, totally comfortable for cruising.

I'm tall and there is no place to put feet under the pedals anyway, since they are all the way forward.
 
I riveted an aluminum angle (3/4 or 19mm) on the lower pedal. So the foot pressure is below the tilt axes and I can still rest my feet below the pedals on long flights - works perfect for me.

pmG0otC.jpg
 
My -8 Rudder Pedal Mod

I was flying another persons RV8 for four years and for "me" the rudder extensions were fantastic! So I designed and made up some for my RV8 project. I am not worried about sliding my feet below the pedals as they are fully forward anyway and would hit the firewall - unless I put the Fred Flintstone mod in the -8 :D
 

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You are correct...

I did a similar lower extension that is angled 25 degrees towards the pilot. I would like the extension to reach further aft to conform to the natural foot angle when heels are on the floor - perhaps about another half inch. Some day I'll get around to making it...

http://tondu.com/rv8a/?s=pedals&searchsubmit&paged=4

Hey Walter.....I also bent mine about that amount(don't remember exactly) and put the aluminum round stock at the bottom to get the bump back and as a pivot point. Feet sit comfortably on the floor and get positive rudder control without touching the brakes......works for me!:)
 
I was flying another persons RV8 for four years and for "me" the rudder extensions were fantastic! So I designed and made up some for my RV8 project. I am not worried about sliding my feet below the pedals as they are fully forward anyway and would hit the firewall - unless I put the Fred Flintstone mod in the -8 :D

These are the prettiest extensions I've seen. Very nice finish work. Looks totally professional. Mine are functionally similar, but nowhere near as pretty!
 
Pink Lindy?

These are the prettiest extensions I've seen. Very nice finish work. Looks totally professional. Mine are functionally similar, but nowhere near as pretty!

Hahaha.....thank you for the kind words and compliment Steve:) I am hoping to get a "pink" Lindy someday for the "prettiest" pedals :D
 
I riveted an aluminum angle (3/4 or 19mm) on the lower pedal. So the foot pressure is below the tilt axes and I can still rest my feet below the pedals on long flights - works perfect for me.

pmG0otC.jpg

Danke Herman. I used your method and it worked fine. I'm surprised at how much inadvertent braking I have been doing. Probably reduced my takeoff roll by 100m! :D
 
Things are different with big feet and long legs. Flying yesterday and got two photos for illustration. These are size 14 hiking boots.

The welded-on pedal sideplates are intended to form a bucket of sorts, but if the soles are wider than the pedals, they ride on the edges of the plates, which exacerbates the inadvertent braking problem. If the pedals need to come out in the future, I'll cut down the plate height some more. Note I cut the tops off them too.

Note the relatively acute angle of the ankle. Can't pull the heels rearward much (if at all) because long legs raise the knees, which already splay outward.

This is an -8, but the others are similar, and depending on pedal configuration, the above factors sometimes requires operating RV pedals with the outside edges of my feet near the little toe. The side-by-side models with pedals tipped aft are the worst. Forget boots or good walking shoes. I have some skinny sports shoes for those.

Foot length here means a lower pedal extension would fall in the arch of the boot sole. It might take quite a lot of angle to extend it aft enough to make contact.

The -8's ground adjustable pedals (for the new guys, "ground adjustable" means "bolted in place") are wider near the floor pivot, which allows the toes through them in cruise. No center adjustment tube either, so note the heels can come together. Doesn't really add much legroom, but it sure relaxes the angle. If non-stopping full tanks, I'll remove my shoes, which does pick up another inch of legroom.

Build what fits you best.
-
 

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... These are size 14 hiking boots.

...

Wow - happy to have my little size 9.5 feet! :D I used to fly with topsiders to have a decent feeling for the pedals, but have changed to leather "driving shoes" as you can see in this video - the heel is more comfortable. They are not far from house slippers in terms of comfort and feeling, but not very good for walking. In case of fire, at least they are leather.

https://www.youtube.com/watch?v=vp4lBr0cSnY
 
Lots of similar mods that all work great !

Like Dan... Above... I did "Rudder Rounds"


I also like the simple aluminium angle riveted to the bottom of the pedal.. (Lighter)


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Also Found the stock return springs on the master cylinders a bit weak so added 1/2" spacer.. No issues with brakes not releasing now..

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