Lotus Elan

Park brake springs???

PostPost by: billwill » Fri Jan 15, 2016 3:42 pm

nomad wrote:The Springs on my adjuster bolts seem very "factory" folk's.

I got to thinking and looking over the whole assembly and I'm not very impressed by the design. As I see it there is no way to keep the compensater tree from flopping to one side or another and forcing one pad or another against the disc. Similarly, they need adjustable rod's as SM offer's. I wish I had noticed this while I was welding on the chassis. One could fit something to the frame to solidly locate the compensater lever when in the released position so that with adjustable rod's the pads would stay off the disc's. Of course this wouldn't take into account the changing geometry as the wheels move through their arc but could be adjusted for normal running.

On second thought, that wouldn't work either....wouldn't account for one wheel moving more than the other. Really would need something to centralize the assembly at the brake disc. As is just the weight of the lever arm and cable is going to bias the wear. If I still had a drawing board I could perhaps come up with a compromise but I guess its a matter of living with the design for now.


Kurt.


That is what the L shaped lifters do when properly adjusted. they are just springy enough to lift the pads off the disc.

De-centering of the whole caliper doesn't really seem to happen much.
Bill Williams

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PostPost by: TroonSprint » Sat Jan 16, 2016 12:25 pm

This is not an original idea of mine, but is one I installed on my Sprint following something I read elsewhere. A tension spring strapped round the chassis to pull the tree to the fully off position.. See photo. Seems a good idea and keeps the mechanism right off. I also have compression springs around the adjustment bolts to keep the pads apart. You can't feel any extra weight when pulling the handle because of the springs. My parking brake is very secure with minimal effort.

Mike
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PostPost by: RogerFrench » Sat Jan 16, 2016 12:43 pm

Kurt, if you solidly located the tree it would no longer compensate. As designed, if it's all lubricated and free to move, the tension applied to each side is equalised so you dont get uneven braking.

Mike, I've been thinki g of something like your return spring, but with a helical spring around the upright of the tree so there's no sideways pull.
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PostPost by: nomad » Mon Jan 18, 2016 12:41 am

RogerFrench wrote:Kurt, if you solidly located the tree it would no longer compensate. As designed, if it's all lubricated and free to move, the tension applied to each side is equalised so you dont get uneven braking.

Mike, I've been thinki g of something like your return spring, but with a helical spring around the upright of the tree so there's no sideways pull.


Roger, as I was typing I realized I was all wet on my original idea. I was thinking just a method of holding the lever when the brake was released so that the unequal weight bias of the lever and cable could be alleviated. I then realized the campensater has to be able to move back and forth according to what the rear wheels are doing in relation to each other. About the only thing that would work is a spring on the calipers to keep them centralized but still able to move a bit. I'm sure all modern rear disc set ups work in that way.

Mike, I like your system since the spring looks as if its not doing anything in the straight and equal mode but I agree with Roger that a helical spring like you would find on a mouse trap would be a better arrangement.

Kurt.
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PostPost by: nomad » Wed Jan 20, 2016 2:54 am

Having only the early "tree" on my hand brake mechanism I believe I will endeavor to manufacture a tree similar to the later tree but with maybe a little wider distance between the lever pivot points that attach to the pull rod's. I believe that putting a turnbuckle in one of the actuating rods would be enough adjustment. Opinion's???
Am I correct in thinking that the thing that holds the assembly together is a threaded sleeve on the upright bolt??

Or, is my early "tree" sufficient? From my reading of the archives, probably not. I do know that the mechanism was froze up on the upright pin. I would definitely expect it to get "draggy" again in short order.

Kurt.
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PostPost by: holywood3645 » Wed Jan 20, 2016 3:08 am

I have a problem with hearing the pad rubbing the disc when I corner hard,
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