sgraber
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| posted on 25/2/04 at 12:17 AM |
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Parking-Brake - Any reason this wouldn't work?
Curious to know what you think about using this type of brake device as a parking brake. Assuming that one could get enough clamping force on the
disc, it looks like the width between the pads could be adjusted with some spacers...
Disc Brake from a
GoKart
Not that I need one, simply thinking out loud. 
Graber
Steve Graber
http://www.grabercars.com/
"Quickness through lightness"
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Julian B
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| posted on 25/2/04 at 08:19 AM |
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I can see a couple of problems. First of all you would need to "pack Out " the caliper to fit a vented/standard car disk. Secondly how
would you mount it to the upright?
I don't know how tough your vehicle scrutineers are when you submit a kitcar for road going test, but here they realy do put the handbrake/park
brake through some tough tests . They check its efficiency on a rolling road and i was wondering how only having a very small pad area would stand up
to the tests?
Cheers
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ned
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| posted on 25/2/04 at 09:29 AM |
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Steve,
This looks very similar to the 'spot caliper' that wilwood make, for parking brakes, go karts etc i think is how its listed on
raldes.co.uk
Image deleted by owner
Ned.
[Edited on 25/2/04 by ned]
beware, I've got yellow skin
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flak monkey
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 posted on 25/2/04 at 10:25 AM |
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I see you got hold of a copy of the Rally Design catalogue then Ned 
Cheers
David
Sera
http://www.motosera.com
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ed_crouch
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| posted on 25/2/04 at 10:44 AM |
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If you want some help sizing the brake let me know: i have designed aircraft brakes before and can assist with the calcs.
Ed.
I-iii-iii-iii-ts ME!
Hurrah.
www.wings-and-wheels.net
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Spyderman
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| posted on 25/2/04 at 12:06 PM |
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Steve,
I don't see any reason it wouldn't work as long as you say you can get enough clamping force.
I do know that the rules for secondary braking/park brakes are different in the USA, but am not sure about your regional variances.
The big problem with putting a park brake onto a disc is the expansion of the disc when hot. As it cools down it contracts the clamping force is
reduced. As this is not an option with four wheel discs you have to make do.
Why are you thinking of this?
Is the MR2 brake not sufficient or siezed?
Terry
Spyderman
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ed_crouch
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| posted on 25/2/04 at 01:26 PM |
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Brake torque = Clamping force * Mean Friction Radius * Mu * Number of pairs of rubbing faces [2 in this case]
Mu will depend on a lot of things. Take a worst case scenario.
Mean friction radius = 2/3 * ((Ro^3 - Ri^3) / (Ro^2 - Ri^2)), IIRC!
You can get at the clamping force by looking at leverage on the lever, and the area of the master cylinder piston, get at the system pressure, then
calculate the slave piston area, and from pressure and slave piston area, you can get at the clamping force.
Energy absorbance matters if the parking brake is required to stop the vehicle: it wouldnt normally be used in this way.
Try calculating the energy stored in a 700 kg car doing 120 mph. KE = 1/2 MV^2. Assume all of this kinetic energy is transformed into heat in the
parking brake. therefore 1/2MV^2 = m*Cp*deltaT
where M is car mass, m is brake heat pack mass, Cp is specific heat capacity (IIRC), and deltaT is change in temperature of the heat pack (the brake),
V is the cars speed.
I wil be looking at brake systems in my Locost work, so check out my website http://www.wings-and-wheels.net for more on this: it will be written
soon.
Hope this helps,
Ed. P.S. U2U me if you want.
I-iii-iii-iii-ts ME!
Hurrah.
www.wings-and-wheels.net
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ed_crouch
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| posted on 25/2/04 at 01:33 PM |
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Just realised that the Ebay item is a screw and nut type device: I will have to dig out my degree notes on these devices, as they are a little more
complex to analyse than hydraulics.
Also, I wouldn't want to dissipate too much energy into one of those: not much "meat" to soak up the heat!.
Ed.
I-iii-iii-iii-ts ME!
Hurrah.
www.wings-and-wheels.net
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mangogrooveworkshop
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| posted on 25/2/04 at 02:23 PM |
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Hi All
I use a mechanical disc brake set on my mountian bike. My experiance is that the brakes are ok but cable stretch is a major problem. In the gocarts
they use solid rods that counter the elastic propertys in cable systems. I cant wait till I can upgrade to hope hydralics and ditch the cable based
system. (My bike is a lot lighter than a 7 and they are crap)
In that Rally design cat they have hydralic handbrake levers for fly apps perhaps you could mod that.
Cheers
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stephen_gusterson
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| posted on 25/2/04 at 02:50 PM |
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I think eds basically saying that if used as an emergency brake, as is required in he UK, it would be shagged.
little brake + big load to stop = no stop
atb
steve
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andkilde
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| posted on 25/2/04 at 03:26 PM |
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Hmmn, on the original question, for the money I'd buy the eBay item try it and chalk it up to experience if it isn't suitable. FWIW, in
Canada the parking brake is not subjected to a "functional test" as in the SVA, don't know about the states Steve.
Then of course there is the "Parking Brake" vs "Emergency Brake" debate. The only car I've ever owned with an effective
handbrake was a Mini (though it was mostly only effective for goofing off in empty parking lots) any other handbrake I've tried was either
pathetic or frightening.
As an aside, Ned should get a job working for rally design, his quick pic of the Wilwood page is 100 times more legible than the raldes website using
the same technology .
Cheers, Ted
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stephen_gusterson
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| posted on 25/2/04 at 03:39 PM |
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I put a mini down the road sideways when I was 18 with my mates as passengers.
One suggested a handbrake turn. I ripped up the handbrake without holding the button in.
that was exciting.
a mini has about 80 / 20 distribution, so even a crap brake at rear would lock wheels.
A jag DOES have a seperate disk on the rear axle for the parking brake. However, IIRC its not easy to get at or remove.
Like most things on an xj-s. Exhaust and steering has to come off to get the starter out, for example
atb
steve
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sgraber
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| posted on 25/2/04 at 04:30 PM |
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Hehe, a little heated debate. That's good. 
I specifically called it a Parking brake because I fully understand that that little P.O.S. would not have to serve as an emergency brake. Simply has
to hold the car. (see included text below for details).
Terry, I do indeed already have provision for parking/e-brake on my current calipers. And that's fine for la Bala MKI. However, my desire is to
use readily available FWD drivetrains. These normally don't include p-brake on the front calipers. And another reason is if I ever want to
upgrade to Wilwoods or Baer lightweights, I would be looking at inexpensive means of adding P-brake capabilities.
Graber
If you want to see a full list of requirements for building a street legal automobile in Arizona
Click Here. (Disclaimer: This is my own interpretation of the ARS and may not include all
items required by law. So put a leash on yer filthy lawyers if it don't work for you!  )
And the text regarding brakes:
Arizona Motor Vehicle Statute 28-952
A motor vehicle and combination of vehicles manufactured or sold in this state after July 1, 1964, except motorcycles, all-terrain vehicles and motor
driven cycles, shall be equipped with parking brakes that are:
(a) Adequate to hold the vehicle on any grade on which it is operated under all conditions of loading on a surface free from snow, ice or loose
material.
(b) Capable of being applied in conformance with the requirements of subdivision (a) of this paragraph by the driver's muscular effort, by
spring action or by equivalent means. The operation of the parking brakes may be assisted by the service brakes or other source of power, if failure
of the service brake actuation system or other power assisting mechanism will not prevent the parking brakes from being applied in conformance with
the foregoing requirements.
(c) Designed so that when the brakes are applied they shall remain applied with the required effectiveness despite exhaustion of any source of energy
or leakage of any kind.
7. The same brake drums, brake shoes and lining assemblies, brake shoe anchors and mechanical brake shoe actuation mechanism normally associated with
the wheel brake assemblies may be used for both the service brakes and the parking brakes. If the means of applying the parking brakes and the service
brakes are connected in any way, they shall be constructed so that failure of any one part does not leave the vehicle without operative brakes.
8. The brake shoes operating within or on the drums on the vehicle wheels of a motor vehicle may be used for both service and hand operation.
Steve Graber
http://www.grabercars.com/
"Quickness through lightness"
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Alan B
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| posted on 25/2/04 at 04:54 PM |
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Hey Steve...good thread...
I'm pretty certain I've seen the spot calipers that Ned is showing in some of my catalogues....I'll check them out..
Definitely an issue of interest for both of us...
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Alan B
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| posted on 25/2/04 at 05:00 PM |
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Yep the one Ned is showing seems to be the Wilwood one...#120-2373 (right) or #120-2374 (left)....at around $58..a little less than the 40 quid
shown....
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sgraber
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| posted on 25/2/04 at 05:13 PM |
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So Alan, a total of $108. Whereas my low cost solution (if it works) would be around $30. A substantial savings...
(or IS it?  )
Steve Graber
http://www.grabercars.com/
"Quickness through lightness"
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Alan B
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| posted on 25/2/04 at 05:21 PM |
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Sorry Steve I missed the point completely....yeah the Wilwood stuff aint exactly bargain basement...
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ed_crouch
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| posted on 25/2/04 at 07:47 PM |
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All im saying is be careful on the size of the brake depending on the requirements driving the choice of kit.
If its got to stop the car, consider overheating as a failure mode, otherwise its just a straight clamp-the-bugger-as-hard-as-you-can job.
Ed.
I-iii-iii-iii-ts ME!
Hurrah.
www.wings-and-wheels.net
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stephen_gusterson
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| posted on 25/2/04 at 10:28 PM |
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if there is no requirement to use as a dynamic brake, why cant you use summat like an auot box does - a peg in a disk full of holes, or a pawl in a
toothed gear?
atb
steve
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TheGecko
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| posted on 26/2/04 at 02:06 AM |
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quote:
Originally posted by sgraber
However, my desire is to use readily available FWD drivetrains. These normally don't include p-brake on the front calipers.
Steve,
I have exactly this issue to deal with as I'm using stock FWD Corolla hubs and brakes in the back of my car. I went to the wrecker and picked
up a pair of Subaru front calipers, which include a hand brake mechanism. These are sized to fit over ventilated discs - in this case 18mm thick.
Mine came from a 1987 Brumby (little 2-door pickup - will be called something else outside Oz). I don't know if the later Legacy/Liberty have
front hand-brake as well - they have discs up to 30mm thick!
These are a single piston caliper quite similar to the original Toyota fronts. They'll need an adaptor plate as the mounting holes are
different. I paid AU$60 for the pair. I can post a photo if anyone wants to see them.
Dominic
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Bob C
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| posted on 26/2/04 at 10:07 AM |
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Didn't one of the old alfasuds have the handbrake on the front wheels? I'm probably wrong - anybody?
Bob c
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Kitlooney1000
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| posted on 27/2/04 at 01:55 PM |
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didnt the citreon bx's have hydraulic handbrakes on the front calipers as well
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David Jenkins
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| posted on 27/2/04 at 01:58 PM |
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quote:
Originally posted by Kitlooney1000
didnt the citreon bx's have hydraulic handbrakes on the front calipers as well
No - cable operated to the front calipers. Had a really nice feature - if you stood hard on the brakes with the engine running, then pulled up the
handbrake firmly, then it auto-adjusted. Nice.
Not so nice was driving hard and using the brakes energetically, then stopping on a hill and putting on the handbrake. Fine, until the calipers
cooled and released the brake!
I quite liked my BXs (I've had 2) but I could never quite come to terms with the body roll on corners...
David
[Edited on 27/2/04 by David Jenkins]
[Edited on 27/2/04 by David Jenkins]
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