[rescue] Sun Netra = Ultra 2?

Francois Dion francois.dion at gmail.com
Sat Dec 9 18:40:32 CST 2006

On 12/9/06, Sheldon T. Hall <shel at tandem.artell.net> wrote:
> C Fernandez ...
> > Sheldon T. Hall wrote:
> > > Yep.  A rubber-covered button on the floor, instead of a
> > > pedal.  It didn't
> > > move perceptably; instead of applying more brakes when you
> > > pushed farther,
> > > it applied more brakes when you pushed harder.
> >
> > Any idea how that worked?
> Not really.
> If I were doing it, though, I'd have a dual-chanbered valve body connected
> to both the the control (low-pressure) side of the hydraulic system, and the
> working (high-pressure) side.  The top part of the valve body would modulate
> the control flow, while the lower part of the body would provide
> backpressure from the working flow.  The valve would move a little bit, but
> the main sensation would be its pressing back against your foot more
> strongly as you pressed against it more strongly.

I think you are pretty close. The hydraulic system was comprised of
many spheres, giving a certain reserve of high pressure fluid. The
hydraulic system high pressure fluid went to a braking system with
feedback as you describe, the pressurised liquid in the accumulator is
sent to the mobile calliper, precursor of modern disk brakes, with 2
jaws and pads, the fluid moves a piston which moves the first pad to
contact the disk and in turns as pressure increases causes the caliper
to contact the second pad. The system included a compensation system
to maintain a constant distance between the disc and pads, no matter
the thickness of the disk or the pads. On top of that, with too much
pressure (locking the wheels) you would feel a pulsing, not unlike an
ATE antilock braking system (sans sensors). This was all designed and
tested by 1953.

Beside the hydraulics doing the braking (there was a handbrake in case
the hydraulics died), it also was used to level the suspension,
assisted the clutch and was used for the power steering. Front wheel
drive and disk brakes. Imagine buying such a car in 1955.

> I've never owned one, though I've always wanted to.  I used to know a chap
> in Atanta who had several of them.  At one point, I think he had "one of
> each" of the big ones running, i.e. an ID, a DS, and an SM.

There are always many of them showing up at Carlisle (import show in
PA, USA). My neighbor owned 2. I dont own any, but wouldn't mind an
early DS in black. Or an SM. Or a CX turbo. Or the XM V6 (I'm very
familiar with that engine). None of the subsequent models (such as the
1G capable Xantia hydractive) made it to the US.


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