"Jim Wilkins" wrote in message ...

The recommendation I've seen is to load a qualification test sample to 4X
but proof the identical working model(s) to 2X. For example 3/8" Grade 70
chain has a WLL 0f 6600 Lbs, proof test of 13,200 and minimum breaking
force of 26,400.
http://www.nacm.info/Downloads/NACM%20_Welded_Specs.pdf

But first you need a load cell. Mine, from an auction, was still expensive
at 5% of list price. The dial indicator readout makes it almost too fragile
to survive field use. Do NOT ask to borrow it.

HF seems to have discontinued the 440 Lb Big Game Scale. Maybe you could
rework the sensors and display from a bathroom scale???

jsw

Cable, wire rope, seems to have a wll of 1/5th the breaking strength, rope
about 1/10 because of knots weakening the rope. Hoists are recommended to
be tested at 110% per multiple documents I've found on websites.

I'm curious about your load cell, what capacity? What price at 5% of list.
I've saw new 20,000lb load cells on eBay for the $150 range IIRC. Is yours
mechanical or does it have strain gauges for electronic scale readers? You
can make your own load cells but the scale needs to be calibrated. I was
the project tech for a machine with 35 load cells so I got pretty familiar
with load cells, testing, troubleshooting, how to make them work when you
have no replacements, etc. So, if I so desire I can machine some load
cells, Omega sells the strain gauges, I can take them to work for
calibration, they have calibration weights in thousands of pounds for their
silo's and truck scales.

Anyway, proper testing of a crane is definitely within my reach, and I like
the idea of around a 4.0 design factor and a 110% or more test. With the
$20 load cell chip I have I can create a million pound scale with ounce
resolution, though it realistically wouldn't be that accurate, it would be
plenty good for testing 110% of a known load. I can make a plenty good
enough scale using a voltmeter and an instrumentation amplifier.

If I get time in the near future I hope to test, I plan to try to lift the
rear of my truck (4X4 Ford Ranger 4.0) with a crane constructed of a two
2X4"s.

RogerN