So the concrete block chiselled out in the 3 legged shape of the 'muffler'
jack whose design exceeds the specs isn't much good then?
Darwin Award Finalist
----- Original Message -----
From: "Tim Collins" <thcollin@mtu.edu>
To: <dwoerpel@wi.net>; <spridgets@autox.team.net>
Sent: Tuesday, November 13, 2012 8:00 PM
Subject: Re: [Spridgets] Steel grades
> 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@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
> ------------------------
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> spridgets@autox.team.net
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