[Spridgets] Jackstands

[Tim Collins]

When you load a concrete block at points "v" in this diagram, the 
underside (points a & b) are in tension. Sprong goes the block, down 
goes the car.

         v               v
|--------------|-------------|
|      a         |     b         |
|                 |               |
|--------------|-------------|



At 10:19 AM 1/11/2010, Dan Dwelley wrote:
>"Concrete is very weak in tension"    Um...the load would be 
>compression not tension. and concrete blocks generally are about 15 
>PSI compression.. (This is not to say they should be used as jack 
>stands...cracks and damage can cause week spots and when concrete 
>fails under load, it's not graceful!) The face of the block has a 
>center supporting perpendicular.... it is weaker than the adjacent 
>face but ... Just palying devil's advocate... :o) Dan ----- Original 
>Message ---- From: David Ramsey <dwramsey at att.net> To: Tim Collins 
><thcollin at mtu.edu> Cc: spridgets at autox.team.net Sent: Sun, January 
>10, 2010 4:55:51 PM Subject: Re: [Spridgets] Jackstands Who cares by 
>the time the cinder blocks fail, you're down the road with your new 
>set of wheels and tires.         Crash 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/ 
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Tim Collins
http://www.flickr.com/photos/12702006@N07/