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Pedal to Sierra Master Cylinder
James - 24/7/03 at 04:28 PM

Just want to check I'm doing the right thing with getting my brakes to work!

So far my plan is the following:
to mount the MC directly onto the bulkhead. I've extracted the pushrod from the servo. This I will weld to the bracket that is held to the pedal by the clevis pin.

Pushing the pedal pushes the rod and that activates the MC.

Is it really that simple? If it is I'd be surprised as nothing's been simple so far!

What stops the push rod coming 'out' of the hole in the end of the MC when the pedal is released?

I must have forgotten something!

Any info greatfully recieved!

Thanks,

James

bob - 24/7/03 at 05:21 PM

You need to put a stop on the pedal,basically to stop it returning too far.
This will then trap the rod between the M/C and pedal/clevis pin.

macspeedy - 24/7/03 at 06:31 PM

one thing make sure you re-enforce the bulkhead as a person recently failed on that, apart from that about what i did.

Rorty - 25/7/03 at 06:14 AM

James, it might be beter to nab a push rod from a wrecker's. Not only will it have the correct radiused end on it, but will also be threaded for adjustment.
The adjustment is critical to avoid damaging the piston(s)/seals. Also, the piston hitting the end of the cylinder, shouldn't be used in lieu of a strongly welded pedal stop.
As Bob says, there must also be a return stop/spring mount to ensure the pedal is at the correct position in relation to your foot/lined up with the other pedals.

James - 25/7/03 at 10:46 AM

quote:
Originally posted by Rorty
James, it might be beter to nab a push rod from a wrecker's. Not only will it have the correct radiused end on it, but will also be threaded for adjustment.
The adjustment is critical to avoid damaging the piston(s)/seals. Also, the piston hitting the end of the cylinder, shouldn't be used in lieu of a strongly welded pedal stop.
As Bob says, there must also be a return stop/spring mount to ensure the pedal is at the correct position in relation to your foot/lined up with the other pedals.


Thanks for the advice guys!

Bob,

Thinking about it there is a stop- it's got the brake light switch attached to it! Doh!

Macspeedy,
I've used just of sheet steel- it's pretty stiff as it is but I'll weld a 19mm RHS across it- should be enough!

Rorty,
I've got the pushrod from the Sierra itself so that should be ok- the bracket that connects to the pedal still has the threaded end of the Micra pushrod screwed into it (I remember thinking it'd be a good idea to keep it at the time!) so I can use that too!

Cool! Sound like I may be onto a winner for once! Now all I've gotta do is get the actual pedal right to fit the brake!

Thanks again,

James

P.S. Does the pushrod end of the MC need to be sealed/protected from dust etc? Because I can use the butchered Servo casing to do so if need be?

Dick Axtell - 25/7/03 at 02:27 PM

quote:
Originally posted by James - P.S. Does the pushrod end of the MC need to be sealed/protected from dust etc? Because I can use the butchered Servo casing to do so if need be?


Yes - it is advisable to fit a cover on the pushrod end of the mcyl. Usually there are some available at one of the shows e.g. Donny.
Don't forget that with your proposed arrangement, you MUST ensure that the mcyl returns sufficiently to allow full recup flow (i.e. brakes release). Using the pedal & pushrod as a backstop will be critical, so I recommend building some adjustability into your pushrod assy (if it's from a Micra, there should be M10 thread + locknut).
Go carefully.

Jon Bradbury - 25/7/03 at 03:21 PM

James,

On the Robin Hood DOHC kit I am building, I dismantled the servo and extracted the pin and rubber boot. A piece of wire is used to measure through the foot pedal hole where the pin is attached to the inside of the brake cylinder actuating rod, which is hollow. I cut the rod accordingly and ground off the ridge at the end and approximated a radiussed end as Rorty suggests. (I could have welded the radiussed bit off the rod end that used to go into the master cylinder - I found it inside the servo and it looks rather like an engine valve). The rod is then fitted using common sense and the Sierra's original plastic doughnut / spring clip. Works a treat, although I'd love an adjuster.

This procedure works for me, but note that my donor is an "H" reg DOHC Sierra Saphire and your brake might be different.


Regards

JonB

Simon - 25/7/03 at 03:58 PM

James,

In response to Jasper's request late last year, see this:

http://forum.locostbuilders.co.uk/xmb/viewthread.php?tid=1923

ATB

Simon

Peteff - 25/7/03 at 11:27 PM

Put a return spring on the pedal so that you are not relying on the M/cylinder spring to push it back or you may find the brakes don't come off completely and drag on the discs.

yours, Pete.