The pressure is set by a stack of washers on a relief valve inside the pump.
On Packards, the instructions are to set the pressure at 240-260 PSI.
Another way to think about it is to estimate the force required to raise a
window or a top. Consider that the lever arm in the mechanism is such that
the cylinder has to put out about 3 times the strength of the spring, plus
the weight of the window and frame, plus the friction. I think you get to
that kind of pressure pretty quick! The cylinder has a piston diameter of
about 1 1/2 inches, right? So the area is 3.14 X 1.5 X 1.5, /4= 1.8 Sq
In, giving a theoretical max force of around 400#. If the spring is around
100# strength, and I think the Packard ones are just about that (it takes a
come-along to stretch them out!), you've just about got the requirement.
You can put a pressure gauge on your system and measure it easily enough.
Remember you have to measure it with everything blocked, as would happen if
the up switch was held for a second after the window was all the way up.
Dick Benjamin
----- Original Message -----
From: KerryPinkerton <pinkertonk@xxxxxxxxx>
To: <mailing-list@xxxxxxxxxxxxxxxx>
Sent: Tuesday, June 25, 2002 10:30 AM
Subject: Re: IML: Fire possibility from 6V solenoid??
> Dick are you sure about the 300psi. The original
> cylinders and hoses don't look like much. Much less
> robust than brake lines. In fact, an early repair
> used compression fittings to splice a line in. It was
> holding fine and due to the condition of the line, had
> been in place for quite a few years?????
>
> Kerry
>
> --- Dick Benjamin <DickB@xxxxxxxxx> wrote:
> > I wouldn't worry too much about it, as there should
> > be no spark created
> > within the device (the only spark is at the switch
> > contacts). If the
> > solenoid should stick on for some reason, it could
> > get warm, but without
> > knowing the current draw, I couldn't guess at how
> > warm.
> >
> > The solenoids are not the usual failure point for
> > these cylinders, the usual
> > failure is leakage past the piston cup. I have
> > peeled the crimp open and
> > replaced the piston seals on these, for a cheap and
> > easy, if somewhat messy
> > looking repair. I have also converted all my cars
> > with hydraulic cylinders
> > to the use of Dexron/Mercon fluid, to avoid the
> > damage caused by brake fluid
> > leaking on painted or upholstered surfaces. One
> > must replace all the
> > system's rubber parts when making this changeover,
> > though, as the old rubber
> > parts will have swelled up somewhat from the alcohol
> > in the brake fluid.
> > When that is gone, they start leaking. Don't change
> > to Dot-5 fluid, by the
> > way, as that has no lubricity and will ruin the
> > hydraulic pump in short
> > order.
> >
> > The solenoid must be capable of resisting fluid
> > pressure of 300PSI, because
> > when the pump is running, there is pressure to all
> > cylinders; only those
> > with the solenoid energized must allow fluid to
> > flow. Then when the pump is
> > not running (for instance when the window is being
> > lowered), the solenoid
> > must present a low resistance to flow back to the
> > pump, so that the spring
> > can pull the window down.
> >
> > Dick Benjamin
> > ----- Original Message -----
> > From: KerryPinkerton <pinkertonk@xxxxxxxxx>
> > To: IML <mailing-list@xxxxxxxxxxxxxxxx>
> > Sent: Tuesday, June 25, 2002 5:54 AM
> > Subject: IML: Fire possibility from 6V solenoid??
> >
> >
> > > Ok, all you EE types, I have a serious question.
> > > Steve Charette found a 6V solenoid in the
> > > McMaster-Carr catalog. Thanks Steve, I missed it.
> > >
> > > http://www.mcmaster.com/
> > >
> > > Go to item # 4916K11
> > >
> > > This is a Pnuematic valve with Buna-N seals. It
> > is
> > > NOT designed for brake fluid. Here is the
> > question.
> > > If this thing were to leak, is there any danger of
> > > fire from the solenoid energizing? I'd hate to
> > burn
> > > the Crown down.... Is there a non flammable fluid
> > > that would subsitute?
> > >
> > > I'd THINK that if it will hold air, it will hold
> > > fluid. This thing is only 24 bucks and I can
> > build
> > > the cylinder for next to nothing so it could be a
> > good
> > > solution for all of us with these hydralic windows
> > > lifts.
> > >
> > > Your thoughts please.
> > >
> > > Kerry
> > >
> > >
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