19-06-2022, 06:29 PM
Hi Denis
The 1938 handbook, which covers semi-girling braked cars like yours, says "The front wheel brake cam spindle is lubricated from the swivel pin". I believe this to be untrue, and a carry over from the older design where there was a passage to allow grease flow.
The Austin Magazine for November 1936 says "The actual braking mechanism of each axle requires no lubrication, being packed with grease when first assembled which should last indefinitely" Such confidence !
Personally, although I assembled my brake cam shafts with a smear of high temperature grease, I also give the occasional squirt of engine oil to the felt washer which sits in the recess of the brake cam operating lever. This ensures that things are free enough to allow the external pull off spring (on the lever) to do its job and return the lever such that there is no effort on the shoes with the brakes off and the cables slightly slack. This enables the upper adjuster alone to establish the necessary small clearance between shoe and drum with the brakes off.
With semi-girling brakes there is more leverage than the previous designs, partly by virtue of the smaller brake cam heads. The downside is that brake wear has a bigger effect on brake pedal height, so convenient adjusters were used on each wheel to enable wear to be compensated for. Unlike the earlier arrangment, the cables should not need adjustment for a very long time once properly set up.
Bearing in mind the tremendous forces involved, I doubt if your "dry" bush would much impair braking effort unless it were really tight. However, if the brakes drag and heat up, it could easily further dry out the grease and exacerbate the problem.
The shoes are pretty firmly held sideways to the backplate by curved spring tabs riveted to the backplate, which should establish "square on" alignment It would be worth checking that these are still in good shape, and haven't been bent by some long-ago owner trying to remove the shoes.
The 1938 handbook, which covers semi-girling braked cars like yours, says "The front wheel brake cam spindle is lubricated from the swivel pin". I believe this to be untrue, and a carry over from the older design where there was a passage to allow grease flow.
The Austin Magazine for November 1936 says "The actual braking mechanism of each axle requires no lubrication, being packed with grease when first assembled which should last indefinitely" Such confidence !
Personally, although I assembled my brake cam shafts with a smear of high temperature grease, I also give the occasional squirt of engine oil to the felt washer which sits in the recess of the brake cam operating lever. This ensures that things are free enough to allow the external pull off spring (on the lever) to do its job and return the lever such that there is no effort on the shoes with the brakes off and the cables slightly slack. This enables the upper adjuster alone to establish the necessary small clearance between shoe and drum with the brakes off.
With semi-girling brakes there is more leverage than the previous designs, partly by virtue of the smaller brake cam heads. The downside is that brake wear has a bigger effect on brake pedal height, so convenient adjusters were used on each wheel to enable wear to be compensated for. Unlike the earlier arrangment, the cables should not need adjustment for a very long time once properly set up.
Bearing in mind the tremendous forces involved, I doubt if your "dry" bush would much impair braking effort unless it were really tight. However, if the brakes drag and heat up, it could easily further dry out the grease and exacerbate the problem.
The shoes are pretty firmly held sideways to the backplate by curved spring tabs riveted to the backplate, which should establish "square on" alignment It would be worth checking that these are still in good shape, and haven't been bent by some long-ago owner trying to remove the shoes.