Maradona
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| posted on 26/5/11 at 03:18 AM |
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Hydraulic Handbrake
I need to install in my locost a hydraulik handbrake to pass the bloody inspection , anydody have one installed ? any pictures will be very
helpful.
Thanks !!
[Edited on 26/5/11 by Maradona]
[Edited on 26/5/11 by Maradona]
Diego,
The locost builder from Argentina
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snapper
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| posted on 26/5/11 at 06:09 AM |
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Interesting deviation from the UK IVA test where we must have a mechanical parking brake.
The hydraulic hand brakes as used in rally cars is a simple fit, will bolt to a similar position as the standard brake ans simply connected in the
middle of the rear brake line.
Another option would be a line lock leaver.
Rally Design have the hydraulic handbrakes.
I eat to survive
I drink to forget
I breath to pi55 my ex wife off (and now my ex partner)
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voucht
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| posted on 26/5/11 at 06:28 AM |
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Hello,
I don't understand if you already have you hydraulic handbrake, and don't know how to install it, or if you need to know what to buy.
The important thing to know is if you have separated front and rear master cylinders in your pedal box, or just one master cylinder as on regular
street car. If you have just one master cylinder, you certainly have a rear brake limiter, either the mechanic one from the donor car, ether an
adjustable one (lever type or knob type) as on the rally cars.
I've uploaded two 3D drawings I've done myself for the catalogue of the company I'm working for, and they show the installation of
the hydraulic circuit (what to connect to the in and the out of the hand brake master cylinder).
http://www.locostbuilders.co.uk/photos.php?action=gal&user=voucht&folder=HydraulicHandBrake
The "in" is the rear port, at the end of the M/C, where you usually connect the brake fluid reservoir, and it should be connected to the
M/C of your pedal box.
The "out" is the front port, in the middle of the M/C, and should be connected to the rear brake. Wilwood or Girling make such M/C, and a
0.625 inch (5/8'' - 15.875mm) diameter is enough for a hydraulic hand brake.
Hope it will help, if you need more info, don't hesitate to ask.
Good luck.
Regards.
S.
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Ham
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| posted on 26/5/11 at 07:35 AM |
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Looking at doing the same, however, I am looking at using a small clutch slave cylinder attached to the handbrake lever.It is only a single output
cylinder which will be "teed" into the rear brake line.
I am concerned that nobody has gone this route. Can anyone see any possible pittfalls?
Cheers
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ReMan
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| posted on 26/5/11 at 07:42 AM |
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As said a hydralic one is easy enough to get, and fit.
But this is an odd requirement as opposed to an independant mechanical one?
One of our better ideas methinks!
www.plusnine.co.uk
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voucht
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| posted on 26/5/11 at 07:53 AM |
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Hi !
Well, a slave cylinder is supposed to be receiving fluid from a master cylinder, and it is not supposed to emit fluid to another cylinder (in your
case, either the rear drum cylinders or the rear callipers). But as it is just reversing the movement, to me, there are no mechanical reasons that is
shouldn't work.
The only problem to me is that your slave cylinder will have to be "out" in the non-used position, if you want to "push" it
when you use the hand brake, and I don't know how you can manage to do that.
As said above, I also think it is a bit too complicated if you compare to using a more "classical" hydraulic hand brake, well proven for
having been used for decades, and easily available.
Cheers.
S.
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Ham
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| posted on 26/5/11 at 08:16 AM |
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Yup correct , in the non used position it will be in the "out" position.It will be connected to my handbrake lever via a push rod, when
the handbrake is pulled the rod will push the piston in, compressing the fluid and applying the rear brakes. My only concern is that the pressure will
be applied both ways i.e. to the brakes and back and to the master cylinder, I feel this shouldn't be an issue as the master cylinder obviously
has a non return valve built in to prevent fluid bieng pushed into the resevour?
The reason for going this route is that I have minimal space availabe and the slave cylinder option is way smaller than the traditional units.
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voucht
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| posted on 26/5/11 at 08:41 AM |
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Hmmm, not sure about the non return in the main M/C. A lot of M/C have the fluid being able to circulate both ways, even "through" the
M/C, like it is the case for the M/C used for hydraulic hand brake. Wouldn't bet on it. Look, for example, if you push the pistons of your brake
calliper to put new brake pads, the fluid comes back in the reservoir, no ? So I would not bet on it.
If your problem is just available space, AP racing makes very small and compact Master Cylinder (body = 70,54mm for the CP2623 series), but the cost
might be too high. Otherwise, Wilwood makes a compact M/C, 50mm shorter than the classic ones, it is available at Rally Design (I had one between my
hands once and it is a very nice part). Though, to use it as a hand brake M/C, you might have problem to adapt a threaded brake fitting on the push-on
inlet, it would have to be checked.
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Ham
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| posted on 26/5/11 at 08:48 AM |
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I never thought of it that way....you are of course correct, when pushing the pads back the level in the resevoir does rise, therefore the slave
cylinder would just push fluid into the resevior instead of the rear brakes.
My next option will probably be a simple line lock using a quarter turn valve.
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voucht
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| posted on 26/5/11 at 08:57 AM |
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Yep ! The 1/4 turn valve will do the job for sure.
Good luck !
Cheers.
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MikeRJ
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| posted on 26/5/11 at 01:31 PM |
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quote:
Originally posted by Ham
I never thought of it that way....you are of course correct, when pushing the pads back the level in the resevoir does rise, therefore the slave
cylinder would just push fluid into the resevior instead of the rear brakes.
My next option will probably be a simple line lock using a quarter turn valve.
Not only will the fluid get pushed back into the master cylinder reservoir, when you apply the foot brake the pressure in the rear brake lines would
also cause the slave cylinder to apply your handbrake. Probably not a great idea!
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Maradona
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| posted on 26/5/11 at 08:54 PM |
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quote:
Originally posted by voucht
Yep ! The 1/4 turn valve will do the job for sure.
Good luck !
Cheers.
Thanks guys !! .
Diego,
The locost builder from Argentina
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indykid
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| posted on 26/5/11 at 10:38 PM |
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I got a bit lost in the middle, but you need to run the master cylinder in line as per voucht's diagram, not tee'd into the rear line.
Just like a normal master cylinder, fluid flows into it from the front line, effectively acting as the fluid reservoir. When you pull on the
handbrake, the reservoir port is closed off and pressure is applied to the brake line (only to the rear - because the 'reservoir' port
gets closed off, no fluid goes back to the front master cylinder). When you release the handbrake, the reservoir port is reopened and fluid can flow
back to the front line.
The main issue is that when you apply the foot brake, the piston in the handbrake master cylinder gets pushed out with the same line pressure as the
caliper pistons, so you need an additional mechanical stop to hold the MC piston in, not just the circlip in the master cylinder.
As an emergency brake, an actual handbrake lever makes far more sense than a line lock.
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