how about this
mount the two pistons in a twin setup, oposite each other in the same bore,
bingo, same force exerted each side as a single piston in a floating bore!
-----Original Message-----
From: [EMAIL PROTECTED]
[mailto:[EMAIL PROTECTED]]On Behalf Of Andrew
Greenbury
Sent: Monday, January 08, 2001 12:09 PM
To: [EMAIL PROTECTED]
Subject: RE: Brakes - Long
I agree with zac: if you exert force on one side obviously there will
be an equal and opposite force on the other side - this doesnt
equate to twice the effective force/pressure.
if you put scales on a table with 10kg on them, do the scales show
20kg because the table is exerting a 10kg reaction on the scales
too??
andrew
> imagine the disk was "u" shaped so that the a brake piston acted inside
the
> "u" shaped disk, a single piston could be aranged to operate internally,
> pushing outwards against the inside of the "u" and thus the effective
> pressure would indeed be doubled, the piston pushes against one side and
the
> floating cylender pushes on the other side.
> in real life it works the same way but with "levers and brackets" used to
> transfer the pressures against the outside of a disk.
> make sence?
>
>
> -----Original Message-----
> From: [EMAIL PROTECTED]
> [mailto:[EMAIL PROTECTED]]On Behalf Of Zac Campbell
> Sent: Sunday, January 07, 2001 8:43 PM
> To: [EMAIL PROTECTED]
> Subject: Re: Brakes - Long
>
>
> I'm not entirely convinced that one piston can create the pressure of two
> pistons just by having it push two pads. To me this would mean the
opposite.
> I think that it would then create only a percentage of it's full potential
> pressure on each pad, whereas an opposing twin piston caliper would be
able
> to push 100% on each side.
> Also are we taking into account even pad pressure from both sides created
by
> an opposing piston setup?
> What about pad area!?
> I'm not doubting Terry's setup his obviously works a charm for the reasons
> that Brad Hallett pointed out.
>
> zac
>
> ----- Original Message -----
> From: Ken Abraham <[EMAIL PROTECTED]>
> To: <[EMAIL PROTECTED]>
> Sent: Saturday, January 06, 2001 5:52 PM
> Subject: Brakes - Long
>
>
> > Errol, Terry, Trevor et. al.
> >
> > Some Notes and questions about brakes resulting from my field trip to
the
> > Wreckers,
> > (some of my recent posts on this have been rejected by the server, so I
> > don't know how much has already got through).
> >
> > 1. Sumitomo twin piston calipers
> > Readily available (i.e choose a good pair and don't pay more than $20
> each)
> > on some Toyota Corona's and Mark 2's (6 cylinder sports coupe), all have
> > braided lines.
> > There are 3 main types, they differ in where the brake line attaches to
> the
> > caliper.
> > The Sumitomo caliper bolts straight onto an early 200b Strut, and I
assume
> > it goes straight onto the 270mm brake-disc 240K struts.
> >
> > 2. Single piston versus twin piston, and four piston - IMPORTANT
> > Previously, we have calculated the effective piston area of a single
> piston
> > caliper as the area of the piston. However, actually the effective area
is
> > slightly more than double the area of the piston since the force exerted
> on
> > the medial chamber wall (the inner face, opposite the piston) is used to
> > press the lateral (outside) pad against the disc.
> > With this new view, compare various calipers below...
> > (Note the greater the effective piston area - the greater the force on
the
> > pads for a given brake line pressure, Pressure=Force/Area)
> > Porsche 993 Turbo caliper has 2x 44mm pistons and 2x 36mm pistons giving
a
> > total area of 50.7681cm sq.
> > By my reckoning the stock 1600 caliper would have 2x 20.43cm sq. =
40.86cm
> > sq.
> > The big 200B caliper would have 45.80cm sq.
> > The poor old Sumitomo would have 36.19cm sq.
> > The Rover 3500/AP Twin pot would have 51.04cm sq.
> > Volvo & Hilux 4 spots 28.27cm sq.
> >
> > As I see it there is no difference in the surface area to volume ratio
> i.e
> > caliper cooling ability) between 1, 2 or 4 or even 10 piston calipers.
> > Perhaps the advantage of 4 spots is that they distribute the clamping
> force
> > over the length of the pad better, hence reducing disc warp and pad hot
> > spots.
> > Perhaps single piston sliding calipers are more prone to flex and pad
> knock
> > off than the opposed-piston fixed type caliper.
> >
> > 3. Sources for brake mods and further research,
> > The Nissan Urvan has large single piston sliding calipers on vented
> rotors,
> > the calipers have the Datto 90mm bolt spacing, but with ~M20 (i.e
large)
> > bolts, and would fit on Bluebird or R31 Struts with slight modification.
> > Approx piston size is 55mm, eff. area = 47.51cm sq.
> > BMW 3.0S calipers are 4 spot vented at the front and twin piston vented
at
> > the rear have 90mm spacing and may fit on Datto 200b, 1600 etc... strut,
> > don't know what type of disc to use though. E28 also has 4 spots and
twin
> > spots. E30 has twin spots up front.
> >
> > 4. Bluebirds/R31
> > The Bluebird is not an 'orphan' or black sheep as people have suggested,
> > parts from it can be good for swaps.
> > The disc brake rear (TRX, LX) is an early version of the R31 rear and
the
> > calipers are interchangeable (internal handbrake on Bluey though),
> similarly
> > up front, the Bluebird brakes are just non-vented R31's
> > There are DBA sport rotors available for the R31.
> > The disc brake rear is basically what is fitted to the VN Commodore!
> > I would like to find a swap for the rear caliper though. I hoped to fit
> > Bluebird front calipers to the rear and fit a Mini pressure regulator,
> > however the bolt and pin spacing is different, any ideas?
> >
> > 5. I made a tactical decision and went for the R31 250mm vented front
> > struts, rather than the 270mm solid 240K struts, I'll just hang onto the
> > Sumitomo's until The brake issue is resolved.
> > I will have to change the spring seat though, or swap all the bits into
my
> > Bluey struts.
> > BTW the R31 struts with vented rotors and finned calipers look SWEET.
> > What car did I get the struts from, it was an R31 skyline, but it was a
> > sports model in Two-tone grey - Not a GTS, they have 270mm discs. A
> > silhouette maybe?
> >
> > Regards,
> > Nick
> >
> >
> >
> >
> >
>
>
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