With the brake caliper, the first question to be clarified was, whether I would place the caliper over or under the swing arm and how I would support the braking torque.
The easiest way would have been to use a pull or push rod and attach the caliper to a plate that presses onto the thru axle and hangs from a pull rod on the opposite side.
I didn't like this solution from a visual and also from technical point of view.
As well under tension as also under push the strut would only make technical sense if it supported itself on the frame. But she doesn't. It only directs the force from the brake caliper forward and thereby generates an additional torque.
Another problem that had to be considered was that the brake should be as easy to remove as possible to remove the rear wheel, since the rear wheel cannot simply be removed to the rear or down, as with a chain drive, but to the left Must pull the swing arm down from the final drive.
A torque-free support is only given, if the brake calliper is supported as close as possible to the axle, directly on the swingarm.
That's why I decided to attach the braking torque support directly to the swing arm and simply hang in the adapter plate instead of screwing it on.
For this, it was ideal to position the brake calliper all the way forward, directly above the swing arm.
A tip from the Cafe Racer Forum made me aware of the small Brembo P2 F05, which should be ideal for it due to its shape. In terms of the size of the pads, it also matched the brake disc very well and has 32 mm pistons.
This it should be!
First, a bolt was welded into the swing arm. Due to the all-round weld seam on both sides, the strength of the fork is not weakened by the hole!
The arrangement of the bolt in the neutral zone of the fork avoids any distortion caused by the introduction of heat during welding.
I drilled the bolt itself hollow for weight reasons. The pin on the inside of the swing arm has remained solid.
To find out the position of the calliper, a cardboard template was made and the shape and dimensions of the adapter plate were determined.
...then it went to the milling machine
When choosing the material, I opted for AlMg 4.5 (AW-5083) and a plate thickness of 12 mm. This is completely sufficient in terms of strength and, in contrast to AW-7075, can be anodized well.
It started with the two holes for guiding the plate on the axle and the braking torque support (position of the pin in the swing arm)
Then the hole for the pin was milled out towards the edge so that the plate can be pushed on:
And this is how the roughly sketched plate sits behind the swing arm:
The next step is to mill out the outer shape and mill the radii:
How this works quickly and easily on a conventional machine can be seen in this video:
...At the end a bit of fine work with a strip of emery cloth and the radius is round.
... continued in the next post
