General => Douglas Motorcycles - General Discussion => Topic started by: handgun on 08 Nov 2015 at 13:29

Title: 1937 Aero Brakes
Post by: handgun on 08 Nov 2015 at 13:29
Servo/band brakes as fitted to 1937 Aero 600. I believe that the majority of Servo/band Front brakes were fitted to Douglas models on the off side of the front forks. and on the Aero's on the near side.
From Heathcote's book the operating cam/bobbin must turn the same direction as the wheel. Did Douglas make CW and CCW cams ?

I believe my front brake is the wrong way round, the cam bobbin rotates the opposite way to the wheel.
Is it possible to re-possition the pins that hold the brake band (mirror image) So that when assembled the wheel and cam/bobbin rotate in the same direction ?

Attached photo of my Brake (note the hole in the plate is for a speedo drive)

Title: Re: 1937 Aero Brakes
Post by: eddie on 08 Nov 2015 at 18:23
    Yes, there were left and right handed brake bands. You can make the band the opposite hand by drilling out the 2 pins in the bobbin, make 2 new pins, then reassemble it as the opposite hand.
Title: Re: 1937 Aero Brakes
Post by: Doug on 08 Nov 2015 at 18:24
Presumably you have already read this post:

Yes, Douglas did make CW and CCW bobbins (or band assemblies). However it does not matter which side the brake was fitted to. All machines after, say, 1926 had the front brake arm pointing forward. So regardless of the side the brake was fitted, the bobbin rotated in the opposite direction of the wheel and was non-servo.

You gain a slight mechanical advantage by having the fixed end of the band be the leading edge, and the link end the trailing edge. Your band is already setup this way. In practice, I do not think it makes an appreciable difference. This is because the link end is more compliant and more readily takes up contact with the drum surface. So you could argue the cause for either!


[fix typo. 22Aug19  -Doug]
Title: Re: 1937 Aero Brakes
Post by: handgun on 09 Nov 2015 at 18:45
Thank you Eddie and Doug for your prompt, and informative reply
I will Modify the bobbin assy to the other hand and try again.