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I'm designing a modification to existent brake calipers that doesn't come with parking/hand brake. One method that comes to my mind is to add a lever with a lobe, anchored to the caliper body, that can actuate underneath the pad. The way to let the piston travel freely up and down, or in and out :) is by having a notch on its head, so the lever can be inside.

Why not pushing the piston itself? It requires drilling the calipers and adding retainers, which may be adding weak points to the design.

Please see the following diagram I have made, any comments are welcome!

p.s. This is a DIY challenge/experiment I want to try and recycle old spares, please do not answer with references to parts I can buy instead. I know they exist.

enter image description here

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You assume that the piston fully retracts into the caliper when you release the brake. But that's not true.

When the pad wears, it becomes thinner, and the piston moves out to compensate. But when the brake is released, the piston retracts only a little, just enough to remove the pressure from the pad. You can't even see it.

When the pads are replaced, the pistons have to be pushed in first to make room for the new, thick pads. As last step, the pedal has to be pressed several times to "pump out" the piston until it pushes the pad to the disk.

Your lever would push the piston in as much as it can, or until the piston touches the back side. In the first case, the piston would move in a little more, and there is no braking power at all. Only in the second case, your system could be able to hold the vehicle.

And when one wants to drive, this parking brake must be released first, and the pedal must be pressed may be 10-20 times to the floor until it becomes hard again. During this time, your car has no working brakes!

Here is a related question, for which I found this animation:

enter image description here

And two more points:

The force applied onto the piston when pressing the pedal is very high. You should not weaken the piston by cutting out parts for your mechanism, and your mechanism should be able to withstand the force if someone presses the pedal while your system is active.

Next, there is almost no space to mount anything to the piston from the side, it would be challenging to develop such a system for an existing brake.

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  • In my design: when the system is "idle" lets assume it is ready for action. If you press the pedal, it will work as expected. When releasing the pedal the piston will release the pressure as expected. When the lever is applied, the piston remains in the same place as it was, the lever will apply force only to the pad. When releasing the lever, it releases the pad to the point it was before. So if piston is doesn't move while levering in/out the pad, why it will need pumping to reset the piston position? Dec 2 '16 at 18:04
  • I have two kind of pistons: ones are solid cylinders, others are hollow cylinders. I plan to create the knotch in the solid ones. As much as I can remove material from it, it won't compare with a hollow design. I'm talking about a width-wise knotch of 5 mm deep x 5 mm width... Dec 2 '16 at 18:06
  • @sweber I love that animated gif. It's good. Dec 3 '16 at 20:41

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