Homemade Bottle Jack Pressure Gauge

Bottle Jack Pressure Gauge
movindirt on offroadfabnet.com
Homemade bottle jack pressure gauge installation utilizing a formula to convert the pressure reading into weight.
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Nov 24, 2013 11:39 AM
High Pressure Steel Fittings would be wise; however, back when I did not "know any better," I have use Schedule 40 "water pipe" on hydraulic systems generating 3500psi w/o a problem.  The issue today, of course, is that lots of "water pipe" is made "off shore" -- often from "recycled" or other inferior forms of steel.  It's pretty hard to tell the difference, just by looking, between a section of "water pipe" that can withstand 3X its rated pressure and one that can take 20X its rated pressure.  So, particularly when lifting heavy objects it is best to "play it safe." That said, the "weak" part of this project is not the tubing, but the gauge.  The author points out that a jack with a 1-1/8 inch ram will be within "six pounds per thousand" of having the pressure gauge read directly in "weight."  This means the 3000 psi gauge shown in the project should not be coupled to anything beyond a 1.5 ton (3000 pound) jack.  Exceeding that jack size would risk damaging the gauge and possibly even bursting it.  In fact, for a 1.5 ton jack with a 1-1/8 inch ram, I would want *at least* a 3500lb or larger gauge.  Even if the jack is precisely adjusted and will "refuse to lift" more than 3000 pounds, this does not mean that you could not exceed that internal pressure -- because, absent a sophisticated pressure-relief system (or bursting), hydraulic jacks will "hold" a lot more than they will lift.  (Ever jack up the back of your truck to change a tire, then jump up on the load to retrieve the spare?  A couple of 250 pound men crawling on top of a load of firewood to get down the spare tire could take the "held" weight up another 500 pounds in a couple of heartbeats!) I would strongly suggest that you do the "ram-to-pressure" mathematics (using the rated capacity of the jack as the "load") prior to selecting a gauge, then pick a gauge with a maximum pressure of at least 20% over the jack's rating. --Just my $0.02 worth. -101-
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