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My 56 tri-pacer has the drum brakes on it and I am wondering how do I adjust them up. I know automotive brakes but I have never seen pipers. I have hunted around the internet and have not been able to find pictures and explainations.
On my drum brakes there is an adjustment , eccentric (sp?). On the left wheel its near the top of the backing plate and on the right wheel its near the bottom of the backing plate. Loosen the stop nut and turn the adjustment screw. It doesn't take much turning to make a big difference. Its been a while since I had mine apart but if I remember correctly, the head end of the adjustment screw is oblong shaped which expands or contracts the drake shoes, depending on how much you turn it.
There is an external adjuster bolt on the backing plate - just jack it up the axle to spin the wheel and loosen the jam nut and turn the adjuster bolt which is a cam internally until you get a slight drag on the shoes.
You should also check your hydraulic fluid level in the master cylinder below the pilot's seat.
If you have the original Bendix M/C, just fill to capacity with hydraulic fluid (NOT automotive brake fluid!) and secure the filler cap.
If you have a North River or Steve's Aircraft boosted M/C (you will see it is different) follow the manufacturer's instructions.
I clciked Advanced Search above and entered Hydraulic Fluid and got this: http://www.shortwingpipers.org/forum...earchid=251049
Plenty of discussion on brakes there! For most of our stock Post WWII Shortwings, use petroleum based 5606 hydraulic oil.
Aeroshell Fluid 4 and Fluid 41 meet the spec, and there are other brands as well.
Here's a random vendor Google found that shows several different brands, provided for educational purposes.
Bob,
this is one of those operations where it is best to first removed your wheel to both clean and inspect the drum and pad assemblies. I like to polish/deglaze the drum with a fresh red scotchbrite pad.
If it hasn't been done in a while I will disassemble the adjuster cams, clean, lube, then reassemble replacing the lock/jam nut if it has been wrench raped by the ham fisted.
If the pads have any oil contamination I will clean with white gas, don't use anything else, and then smooth with the red scotchbrite.
If the brake cylinders have been leaking replace the o-rings with ***known to be fresh*** ones and not ones that have been laying around the shop forever. I assemble with silicone grease.
Adjusting the pads should be done with a multiple cycling of the brakes to get them all sitting where the are happy. Go out and do about two or three days of flying and then adjust them again.
When mine are tuned up nice I can hold the plane at 1500 rpm for my run up and that is with 8:50 tires which reduce the effective braking do to the increased diameters mechanical advantage. On gravel I can lock them up while landing without pulling too hard on the Johnson bar and probably could on the black stuff although I usually don't need to try with five thousand feet in front of me.
Bob, on my '56 T-P, I have an eccentric adjuster cam for each brake shoe, four in all. If you need new ones, Preferred Airparts is far more reasonable than Univair. Here are some pics; note that the cams are mirror-imaged: to adjust shoes outward, one turns CCW while the other turns CW; each wheel has one of each, one on the top and one on the bottom.
Walt thanks for the pictures. I figured they were similar to old drum brakes on cars. now that I see exactly what they are doing it more like a semi with twin cams. I did adjust them the other day and I will do it again next time I am out at the airport. Just to be sure. To day it looked like my oil cooler is starting to weep. I was a little oily when I landed. sprayed it down with carb cleaner and will check it next time I am up. we will see. Anyways thanks for the lesson on brakes, how everyone had a nice holiday
You might notice, in pic #3, the lower cam has a different shape, much more rounded…. turns out it had almost 1/8" LESS at max diameter; each wheel had one of those. No, it wasn't just because it was worn. Made it impossible to adjust two of the shoes (they're worn but serviceable) so they'd begin to contact the drums' inner surfaces. Not sure what plane they came from, but I don't think they were PA-22 parts. PA-22 parts book shows all four as being the same shape, just mirrored pairs. As most adjusters were also well rusted, I replaced all four.
That flat little hex nut in the last pic is meant to be staked onto the adjuster stem after it's been inserted through its hole, where the end of the threaded stem has been ground with two flats. I just left them off and used a small adjustable to hold the stem while adjusting, as three of them had been missing from the existing set-up anyway. Less air resistance, too!
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How do I adjust drum brakes
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