What do you do when you?re building an airplane with your wife, you have promised not to do anything major without her, and she?s out of town on a business trip? Well?.you work on components, of course! There are lots and lots of components that have to be fabricated ? such as the brake pedals. The Van?s design is pretty simple ? a couple of flat plates of 1/8? aluminum joined to a couple of side flanges made up of aluminum angle. But nothing is completely simple ? the two sides are made differently because one side has to have a bell crank arm to actuate the brake cylinder. And the width is set by the pre-welded rudder pedals. OK, so build it pr plans, and you?re set, right? Well?..not exactly. First, the plans don?t actually work for the brake cylinder bell crank ? either the outline or the measurements are wrong. Secondly, we had these COOL ?RV? brake pedal blanks we?d gotten on VAF that looked much nicer than flat blanks of aluminum. But ? they were 3/8? narrower than the stock design.
Van?s ?Stock? RV-3 Brake Pedal Drawing:
Since the pre-welded rudder pedals defined the minimum width for the flanges of the brake pedal, I would have to accommodate the loss of width somehow. My first thought was that I could simply make the pedals as designed, and bolt the nice looking ones on the front of them. It would require making sure that I didn?t put rivets where the screws would go (since the fancy pedals had milled holes for screws). It also would be twice as heavy as necessary ? and being that this is an RV-3, I am trying to at least salute the idea of building it sorta? light. So doubling things up didn?t seem to make much sense (I didn?t need a brake pedal appropriate for a tractor?)
So how about redesigning the side flanges to bolt directly to the fancy pedal blanks? Looking at the aluminum angle that I had in stock, an easy way to do it was with some 1 ?? x 1 ?? by 1/8? angle stock on both sides to form the flanges, with a plate to form the brake cylinder arm riveted n the side. Making the two side flanges symmetrical just ?looked good? from a design standpoint, and fabrication would be easy because I could make them back to back. It might be just a touch heavier than the Van?s design, but since the actual brake pedal plate was smaller, I figured it would be a wash ? or at least measured in grams.
I started the first side flange by making it to plans. Mockign that up with the plate and the rudder pedal, I found a few modifications were required, so the second prototype was produced. Once this fit well, I made a mirror image ? and then duplicated each of those (two pedals?..). I had to do a little minor radius gringin on the rudder pedals to allow good action, and the basic pedals were complete. The last piece I needed was the bell crank arm. I traced the outline off the drawings and cut it out ? but when it came time to drill holes, I discovered that the measurements simply didn?t add up. There was no way I was going to get the specified ?arm? of 2 1/8? as called out on the drawings. Now, of course, I had a dilemma ? which was right - the outline of the part on the drawing, or the measurement? Hmmm?.I have seen both things in error at various times on the RV-3 drawing. Using a little engineering logic, I decided that I would rather have more leverage on the brakes than less, so I?d go with the length measurement, and remake the plate to give me that arm. Out came the 1/8? stock again, and I sketched a pleasing shape to give me what I wanted. Of course, I had to make two of them (one for each side)?.
With those two plates cut, I had all the pieces, and could mock them up using cleco clamps and bolts. Everything seemed to fit together pretty well, and I only had to do a little filing of the flanges to get a nice smooth swing of the pedal. From there, it was a simple matter of laying out rivets to attach the ?arm? plates, full-size the holes, and oh yes, decide how I want to do the rivets ? round-heads, flushes, or double flush? Decisions, decisions?.. Following that, everything has to come apart for edge finishing, riveting, scotchbriting, priming and painting (followed by baking in the oven) and then assembly. Piece of cake ? all it takes is time.
?Custom? Brake Pedals (short of riveting and finish):
This RV-3 building is fun!
Paul
Van?s ?Stock? RV-3 Brake Pedal Drawing:
Since the pre-welded rudder pedals defined the minimum width for the flanges of the brake pedal, I would have to accommodate the loss of width somehow. My first thought was that I could simply make the pedals as designed, and bolt the nice looking ones on the front of them. It would require making sure that I didn?t put rivets where the screws would go (since the fancy pedals had milled holes for screws). It also would be twice as heavy as necessary ? and being that this is an RV-3, I am trying to at least salute the idea of building it sorta? light. So doubling things up didn?t seem to make much sense (I didn?t need a brake pedal appropriate for a tractor?)
So how about redesigning the side flanges to bolt directly to the fancy pedal blanks? Looking at the aluminum angle that I had in stock, an easy way to do it was with some 1 ?? x 1 ?? by 1/8? angle stock on both sides to form the flanges, with a plate to form the brake cylinder arm riveted n the side. Making the two side flanges symmetrical just ?looked good? from a design standpoint, and fabrication would be easy because I could make them back to back. It might be just a touch heavier than the Van?s design, but since the actual brake pedal plate was smaller, I figured it would be a wash ? or at least measured in grams.
I started the first side flange by making it to plans. Mockign that up with the plate and the rudder pedal, I found a few modifications were required, so the second prototype was produced. Once this fit well, I made a mirror image ? and then duplicated each of those (two pedals?..). I had to do a little minor radius gringin on the rudder pedals to allow good action, and the basic pedals were complete. The last piece I needed was the bell crank arm. I traced the outline off the drawings and cut it out ? but when it came time to drill holes, I discovered that the measurements simply didn?t add up. There was no way I was going to get the specified ?arm? of 2 1/8? as called out on the drawings. Now, of course, I had a dilemma ? which was right - the outline of the part on the drawing, or the measurement? Hmmm?.I have seen both things in error at various times on the RV-3 drawing. Using a little engineering logic, I decided that I would rather have more leverage on the brakes than less, so I?d go with the length measurement, and remake the plate to give me that arm. Out came the 1/8? stock again, and I sketched a pleasing shape to give me what I wanted. Of course, I had to make two of them (one for each side)?.
With those two plates cut, I had all the pieces, and could mock them up using cleco clamps and bolts. Everything seemed to fit together pretty well, and I only had to do a little filing of the flanges to get a nice smooth swing of the pedal. From there, it was a simple matter of laying out rivets to attach the ?arm? plates, full-size the holes, and oh yes, decide how I want to do the rivets ? round-heads, flushes, or double flush? Decisions, decisions?.. Following that, everything has to come apart for edge finishing, riveting, scotchbriting, priming and painting (followed by baking in the oven) and then assembly. Piece of cake ? all it takes is time.
?Custom? Brake Pedals (short of riveting and finish):
This RV-3 building is fun!
Paul
