Sonex Drum Brakes

 
 
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The Sonex is designed to use cable actuated drum brakes by Azusa. These brakes have taken a lot of flak in the sonex community. Sonex now sells machined drums to replace the stamped drums. These reportedly improve effectiveness and reduce the fading effect. Before getting started, you should have a look at the Instruction Sheet Sonex put together.
According to the included sonex instructions, the brake cams need to be modified by filing off the sharp corners on the cam.
This modification gives a smoother feel to the brakes, and they don't seem to require as much effort to engage.
To remove the cam, you must fight the springs, and they are very stiff. To get around any problems when I re-assembled the brakes, I made some wood wedges to hold the springs open. It worked very well, but the wood did crush from the spring pressure. Aluminum might have made a better wedge.
This picture shows how the bolt head has very little clearance due to the axle socket. There is not enough clearance to get a socket on, and an open wrench can only make 1/4 turns at a time.
The recommended AN3-5A bolt to attach the brakes to the axles was too long, and rubbed on the brake return springs inside. Switching to a AN3-4A bolt solved this.
The cable guides need one end drilled out to accept the housings.
Cable guide bolted on the gear leg.
A little tweaking with a screw driver got things lined up nicely.
Although the axle spacers are simple to make, they are easy to overlook in the plans. They are not included in the welded components kit (as they are not welded...), and don't appear on the Wicks hardware kit for the taildragger. This meant another order for 1 ft of 4130 tubing.
Axle spacers finished and primed.
Azusa wheels assembled and mated with the optional machined drums from Sonex.
Wheels, brakes, and gear completely assembled.

 

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Updated: 9 May 05