Drum brake improvement

[peter anson]

I have the original Azusa drum brakes, complete with the pressed steel drums. They were never great although when they were new reached the dizzying height of adequate, but lately they have become very ineffective. An engine run-up at 1900 rpm was about their limit, and after the run-up the right hand brake was tending to stick on. I assumed well worn linings but what I found was that they were badly glazed and one of the liners had half separated from the shoe. New shoes from Azusa plus freight and an unfavourable exchange rate meant that a new set would cost well over A$100 so I decided to see what was available locally. A local automotive brakes specialist was able to get the shoes relined for A$70. This sort of repair used to be common but there is apparently now only one business in Melbourne (I guess that makes it in the whole of the state) that can still rebind brake linings. I machined the new linings to match the drums and also took some care centering the drums on the wheels.

I took very fine cuts because it's only springs holding the shoes in place.
The end result was a dramatic improvement in the braking. I feel that they are much more effective than the original shoes when new, possibly due to having really good fitting shoes but could also be different lining material. I guess time will tell if the improvement is permanent.

Peter

[Corby202]

On the Azusa brakes I have had over the years, I have always elongated the shoe pivot hole to try and get the shoes to seat better and to work on the part that turns (cant remember what its called) because one shoe always seems to start moving before the other one. Mine will hold at full power, just, but that is only 80hp. (machined drums) They are crap brakes but I don't like the way the Sonex disc brakes work so I have stuck with them.
Phil

[peter anson]

I have done a bit more flying and obviously a few more landings since my original post and one of the most dramatic differences I have noticed with the improved braking is how easily I can do short landings now. My landing distances have gone from around 350 to 400 metres (1150 to 1300 feet) to easily under 300 metres (1000 feet). It used to be that I was braking hard to get slow enough for the next taxiway. Now I find that I am releasing the brakes early so that I can coast up to the next taxiway. This is without any change to my flying technique and I am certainly not trying to do short landings.

Peter
Sonex 894, 440 hours and still learning things

[LarryEWaiex121]

If its any consolation, the Aero Conversions hyd. brakes aren't the wonderful solution that many had hoped for. I get air in the lines no matter how many times I bleed them. It doesn't stop them from working, it just requires one pump to get some power and another to actually brake.
As far as durability..............well there isn't much. I've had them on now I believe 4 yrs and at each condition inspection, I've been replacing both pucks and rotors. The steel rotors just wear incredibly fast in my opinion. To the point the bolt heads holding the wheels together are flush with the disk surface. That's a lot of wear in only 100-120 hrs. I think the one side push is pretty questionable vs. pinching a floating rotor.
Now brake durability is a very subjective thing and I get that. But to put perspective to the matter, my Azusa brakes where pretty decent stopping power and I never replaced a shoe or a drum in over 400 hrs. These hydraulic brakes are requiring a complete replacement of the rotors and pucks every 120 hrs. And its not cheap. The pucks are like $14 each x 4 and the rotors are like $35 if I remember correctly? Honestly I can't remember, I just pay the bill and move on.
As for the Azusa shoes hanging up, you can stop that by grinding the approach on the cam ever so slightly. And a touch of grease. Careful not to get too much so it gets into the shoes. Then your cooked.
I had brake hang on run up several times before I figured out the approach was too steep and wouldn't allow the cam to rotate back on handle release. In essence, I'd say don't throw rocks at the Azusa brakes. With a bit of wear in to get surface to surface contact and a bit of figgity work, they perform quite well. And compared to the hydraulics from Aero-Conversions at least, the Azusa's are comparatively in-expensive.
Lastly, I'm not bashing Aero-Conversions brakes, but there is room for improvement in most all of these offerings. Simply put the more you fly, the more these shortcomings rear their ugly heads. Folks that only push their plane out of the hanger a dozen times a year got nothing to worry about. LOL
Take care and Merry Christmas to all.

Larry
Waiex121YX, Camit 3300, Dynon Skyview, 769 TT airframe hrs.