Friday, 15 February 2013

Brakes, cams, springs & other mechanical merriment.

Back from Norway, I find a handy bit of tube on my desk.

So here is a nice new bush:

It is made from 5/8" x 16 SWG seamless tube, pressed into the brake plate. I may put an oil hole in it if I decide there is enough access.

So, now I am assembling the brake I find something I didn't expect.

I replaced the brake lever return spring, because the arm makes an angle of more than 90 degrees with the brake rod - i.e. it leans forwards (the arm is upward on the brake cam)

You can see the old spring is quite weak and would put the arm in the wrong place. So now I have a new spring, the arm points backwards and makes an acute angle with the brake rod and can be moved to near 90 degrees, as the brake comes on.

The thing is, I didn't expect the spring to operate the brake with the brake rod disconnected. Because the lever return spring is quite strong, it turns the cam, overcoming the shoe springs and the brake comes on. It's obviously designed that way.

I guess all my previous biking experience has had the brake lever return spring on the foot pedal, not the brake arm on the cam.

Anyhow, some more pics for Chaz:

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