August 10, 2009

Installed Long Bolts on Brake Pedals - 1.0 hrs.

Today, since I was unable to round up some help with riveting, I took care of a matter that has been on my mind for some time. A while back, when I posted some pictures online about my anodized brake pedals, some people commented in the forums that I should consider using one long bolt instead of the two short bolts indicated in the plans, to hold the brake pedals in place. I hadn't heard of this and I didn't know a thing about it, so I did some reading and research.

There have been reports of some RV's that have had problems with sticky brakes. Can you imagine what sticky brakes can do? At the very least, you will wear out brake pads and tires much faster than normal, and at worst, think of landing with one brake or the other being stuck. That's a disaster I don't need! This can be caused by several things. One thing I don't want to do is torque these bolts down to 25 inch/lbs, which is standard for AN3 bolts. I was tempted to do that when I installed the brake pedals, but these bolts serve a different function here. They aren't used so much to hold things tightly together as they are intended to become an axis that the brake pedal rotates around. That's why we use castle nuts and cotter pins instead of standard nylock nuts on the brake components. They need to remain somewhat loose and definitely free to rotate. Another possible cause can be slight misalignments in the two short bolts that hold the brake pedals in place. If they aren't exactly parallel, you don't have one axis for them to rotate around. Even if they're okay now, I can see how over time the little ears that hold the bolts might be bent slightly, especially if you really step hard on the brakes from time to time. So I am now thoroughly convinced that using one long bolt is the way to go. This insures having one straight axis so you don't get any binding, pinching, or stickiness. Here's the thread on the VansAirForce forums that I started with when I read all about this: sticky brakes. Check it out. Some guys are even installing springs to the master cylinders for a more positive force to return the brake pedal. For now, I'll go this route and watch it carefully when I begin flying. I can always add springs later if necessary.

So I measured carefully and then shopped around for a pair of AN3-56 bolts. I ended up buying them here, from Genuine Aircraft Hardware.

Here are my brake pedals as I originally installed them, as seen from the back side with the two short bolts holding each one to the rudder pedal. Below is a close-up shot.

Here are the two AN3-56 bolts as they came from Genuine Aircraft Hardware. Very well packaged.

These suckers aren't cheap. They cost a little over $15 each, and with shipping costs included, it was over $40 for the pair. You can double that if you're installing duel brakes. Ouch! Aircraft hardware can be so expensive. But do I want to risk sticky brakes? Not for saving a lousy 40 bucks I don't! In the grand scheme of things, considering the cost of the whole aircraft and the money I could save on brake pads and tires, it's not a big deal. You just have to get 'em and move on.

Here they are, about an hour later. I ran my #12 reamer through both holes at the same time on each pedal, to make sure I had a nice straight hole and one continuous axis before installing the bolt. The length was perfect. Below is a close-up shot as seen from the back side of the pedal.

UPDATE: A reader noticed a BIG mistake I was making here and straightened me out before I install the rudder pedals for good in the plane. Think about this for a minute... did you notice my mistake here? Look at the direction I put the bolt in. If I leave the left pedals' bolt installed in this direction (remember, this is the back side of the pedal) then I will never be able to get it out for maintenance, or whatever. It would run into the side skin of the fuselage before being completely removed. The solution is to remember to put the bolts in so that the heads of the bolts are on the inboard side of the pedal. That way, if you have to remove the bolt, you can swing the pedal ahead of the other one and pull the bolt out toward the center of the cabin and it won't run into the side skin. Thanks, my unknown friend! Once again, the RV community and the online forums have done me a great service. It always helps to have experienced eyes looking at your work.

And here's what they look like from the front side. Nice!

It really feels good to have this done. I haven't installed the cotter pins yet. I'll do the final tweaking and put the cotter pins in before installing this in the fuse. I want to make sure the rest of the bolts, on the master cylinders, etc. aren't too tight either.

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