On 2011-11-05, DoN. Nichols wrote:
On 2011-11-04, Ignoramus8802 wrote:
I am thinking, that when the forklift holds a weight on the forks, the
pressure in the main lift cylinder should be a linear function of
weight:

P = A + B * W

Does anyone make a product or some such that I can hook into the
hydraulic line somehow, that would tell me the pressure and the weight
of the item being lifted?

There are liquid-filled (often glycerine) hydraulic pressure
gauges. You would need to know the diameter of the piston to calculate
the load from that, and of course subtract the empty load pressure from
the pressure with an actual load in place.

I think that the gauges go at least to 10,000 PSI.

Here is one (3,000 PSI) on eBay for only $9.95: # 250921080861

Here is a 10,000 PSI one: # 250796780436

Don't worry about the air bubbles in there. That is needed to
allow expansion when under pressure. (The bubble should get smaller as
the needle goes upscale.)

This one is a different design, and goes to 3,000 PSI: 280595831572

Do a search on:

Hydraulic pressure gauge

and there are a little over two pages of them.

Or -- if you want to buy *new* -- check out Enerpac as a good
maker.

I would suggest starting with the piston diameter, and
calculating the likely pressure range (multiply by two if the piston
pushes a roller chain gear up) before ordering a gauge. I suspect that
the lift does (or certainly *should*) not go to 10,000 PSI for example.

Don. thanks. I believe that I do not need to do any calculations. If I
assume that P = A + B * W, then all I need to know to find A and B is
the pressure with nothing on the forks, and the pressure with, say, 2
tons on the forks. Once I know A and B, I can make a little table on a
card and put it next to the gauge.

For hydraulics, I would rather buy something new at McMaster for $40,
than something unknown on ebay for $9.95 plus $8 shipping.

Thanks, though, for confirming that it is doable.

i