[Spridgets] Steel grades

[Tim Collins]

When I was teaching at the U I purchased 2 muffler type jack stands 
to test to failure. We had a 120,000 universal test machine (big 
press).to test them on. The jacks were made of muffler tubing (that 
style) with the base circumference cut into thirds and then splayed 
out to make the three feet or legs of the jack. Those legs were held 
together at the very bottom by metal straps welded between legs. The 
upper part of the base had holes at various heights for adjustments. 
The second part that slides inside the base pipe was just a pipe with 
holes for the adjustment and an upper most saddle onto which the axle sits.

We loaded the jack up to 6000lbs - the rated capacity - with no 
problem. We kept going until failure. I wish I remembered all the 
numbers, but that was a long time ago. What I do remember is that the 
jack legs failed first - they buckled. However there was plenty of 
warning that the jack was being crushed and the jack still was 
holding an appreciable load. Now remember that there was a slow 
steady load applied - no impact and the load was applied 
perpendicular to the support surface. No crazy offset loading or 
impact loads. All in all the jacks performed within the specs and 
well beyond. Now don't be silly and use muffler pipe jacks to support 
your D9 dozer just because they can carry more than 6000 lbs. OK? And 
don't even think of using a concrete block!!


At 08:59 PM 11/12/2012, dwoerpel at wi.net wrote:
>OK, metallurgists.  I'm looking at a set of jack stands and the pins
>are made of #20 steel.  What does that mean?  I've determined
>it's probably a China grading but haven't been able to find anything (that
>I could understand).  How does the numbering system show strength,
>etc.?
>
>Just curious,
>Dave W.
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Tim Collins