Brake pedals are sticky

[KitfoxDave]

I am building an SS7. I have been working on the brake pedals. When I torque them down to 20 in-lbs, they are very hard to move and the master cylinder spring is at its max in returning them to the brakes off position, if it even can. Is this normal? The bolt is free in the bearing. It seems there is too much friction between the brake pedal and the end of the bearing. Is there a special lubricant that is used? Is it ok to not torque them to 20 in-lbs? When I loosen up the nuts, they move just fine. The bearing is tight in the "t" tube at the top of the rudder pedal assembly.

Would appreciate your feedback.

thanks,

Dave

[Jerrytex]

There is a ton of threads on this that you can search and get some good pointers. I think you'll find that it's just a case of sanding, and fitting to make it all work smoothly. The Derlin rods have to stick out slightly to get squeezed by the pedals. The Pedals then rotate on the Derlin rod/bearing. If the bearing/rods are binding in the "T" then they won't rotate freely. If you look at the "T" where it's welded, at least on mine, it was slightly curved from welding. I did a lot of sanding in this "T" to average out the curve. Also sanded derlin rod to make it rotate smoothly. I used a little never seize as well since this is mostly sealed and protected from getting much exposure to dirt and sand.

Hope this helps.

[Dave S]

Jerrytex is spot on on this. If the delrin rod is too short so the pedal frame tightens up on "T" tube with the bolt at the proper torque, an easy fix is to stack a washer on the end of the rod where the washer is small enough in diameter to avoid contact with the "T" tube - a light washer might be enough to do the job.

[efwd]

This may not be the consensus among this forum or AIs for that matter, But, save yourself a lot of grief in trying to sand and polish until it works, that is if you agree with me. If you are comfortable tightening up your single, castellated nut on your wheels and tires, to only finger tight, then what would be wrong with loosening up your nut in this application. Of course it would require replacing the nyloc nut with a castellated one. 25in/lb torque was too much for mine as well. You will note that it takes about 1/4 turn to loosen things up enough and a cotter pin will ensure it remains assembled just like your wheels. You should ensure that the bushing is doing the rotating and not the bolt turning inside the bushing. Your pedal flanges should be gripping the bushing not the metal T portion. If someone has information why this is ill advised, I suppose I will need to do some more work.

[KitfoxDave]

Thanks for the feedback. I didn't understand the Derlin rods rotate in the rudder "T". I thought the bearing action was the bolt rotating inside the Derlin rods. I have some sanding to do.

[Jerrytex]

Yeah the manual is not really clear on this. I just kept sanding the derlin rod and the "T" until I got it buttery smooth. Then put the bolt in and as Dave mentioned, I think I had to add a washer on one side so the pedal squeezed on the Derlin rod and not on the "T".

[KitfoxDave]

What methods did you use to sand the derlin rod and the "T"?

[Jerrytex]

Put the Derlin rod in the chuck of the drill and spin while grabbing it with sand paper. Then flip it and do the other side. For the "T" I used small dowel rod wrapped in sand paper and also in a drill. Sand a little and then check fit.

[Jez]

This may not be the consensus among this forum or AIs for that matter, But, save yourself a lot of grief in trying to sand and polish until it works, that is if you agree with me. If you are comfortable tightening up your single, castellated nut on your wheels and tires, to only finger tight, then what would be wrong with loosening up your nut in this application. Of course it would require replacing the nyloc nut with a castellated one. 25in/lb torque was too much for mine as well. You will note that it takes about 1/4 turn to loosen things up enough and a cotter pin will ensure it remains assembled just like your wheels. You should ensure that the bushing is doing the rotating and not the bolt turning inside the bushing. Your pedal flanges should be gripping the bushing not the metal T portion. If someone has information why this is ill advised, I suppose I will need to do some more work.

Hi Eddie, why would it matter if the bolt turned inside? That’s pretty much what happens with the bell cranks. And is it ok to use the existing bolt and drill a hole in it to except the cotter pin. Also, what size would the castle nut have to be? I am on this part of the build now

[efwd]

Hi Jez, I guess your right. I should defer to the A&P/AIs but, bolts that are free to rotate become scored and therefore their integrity would be comprimised. Consider the application. Also, if that bushing is fixed and the bolt rotates within, that would mean the rudder pedal flanges are rotating about the bushing ends. That means the bushing is going to wear on the ends that are in contact with the pedal flange. Your working with far less contact surface area under the circumstances than the entire length of a bolt shank. Eventually that bushing may become shorter than when first installed and you may end up with the metal flange of the pedal dragging against the metal where it is attached. Im no engineer just an Army trained helicopter mechanic that replaced bolts that had mars in them and or corrosion protection worn through. Hope your only using my thoughts as a consideration. That all might be horse manuer since you have already provided a contradiction.
You can definetly drill your own hole in the threaded end or through the bolt head when needed. Whatever size your teflon nut is, there is a castelated nut of the same dimension.