[Spridgets] Jackstands

[Tim Collins]

Many, many years ago - maybe decades ago - I purchased a set of 
"muffler pipe" style jack stands with the specific intent of testing 
them to failure. At the university I had access to a 120,000 Lb 
Tinius Olsen universal test machine (http://www.tiniusolsen.com/) to 
run the test. Think of this machine as a BIG bearing press with 
instrumentation. The jack stands were the type made of muffler tubing 
- splayed legs held with a small strap of steel to keep them from 
spreading. An inner pipe has a cradle on top and usually 3 height 
adjustments holes through which a pin is placed to make the 
adjustment. Something like these - only these are better 
http://www.danoland.com/nsxgarage/tools/jackstand.jpg. The ones I 
tested had the base strap installed about 1" above the floor and the 
3 legs weren't beveled to sit flat on the floor.

Here's what I found.
1) The jacks were able to hold their rated capacity with no problem.
2) They exceeded their rated capacity - I can't remember by how much.
3) When they began to fail, the failure was not catastrophic. There 
was plenty of warning that the load was too great. The jacks slowly 
buckled when they did fail. The spotwelds held. The adjustment (which 
was in double shear) did not fail. The holes in the tubing did begin 
to elongate - another warning of excessive load.
4) The jacks rested on 6 points on the legs since the legs weren't 
beveled to sit flat on the floor. Those points buckled early in the 
failure - a sign of excessive load.
Overall there was plenty of warning that failure was about to happen.

SAFE BUT . . .
1) The load on the jack was applied slowly - no sudden impact which 
could have changed how they failed.
2) I only tested 2 jacks out of the thousands made and the 
considerable number of variations on how they were built.
3) The Tinius Olsen machine held the jacks squarely - no uneven floor 
to introduce odd ball loading.

Conclusion.
These were about the cheapest jacks made in the day yet they did the job.
Just now I had a hard time finding a picture of the jacks - the 
danoland.com site above. All the jack stands that came up had better 
design features than did the muffler tubing jack stands. This doesn't 
mean the materials or workmanship is OK - just that the basic designs 
today look better to me.

Finally, don't ever use a concrete block as a jack stand. Concrete is 
very weak in tension and will fail suddenly under a relatively small 
load. When loaded on the face of the block the concrete is in tension.

Tim Collins
http://www.flickr.com/photos/12702006@N07/