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I'd be afraid of a crack with a span that wide but then I don't see why you couldn't make the span less with a narrower jack or even add small side strips on top to help support the load some, like he did for stops either side of the tire.
edit: even a strip of metal angle iron on either side would make me feel a bit better.
edit: or even a thin metal plate on the under side so some jacks wouldn't damage the wood and add potential fail points and strengthen. Still I'm no wood expert and you would have to consider more holes as the same chance for failure points.
Making a set of wood cribs, ones that you can add/stack-on to for when you need a lot of room under a car has been on my to-do-list. I had planed on making a base to put under the jack to get the height needed for the 2nd step but may try to adapt the jack under crib method shown here.
Tall jack stands to reach a suv/truck frame may not be available in his area or ridiculously priced.
I wouldn't lift on something that could rotate so easily. If it did it would spit that jack out.
I hadn't thought about this, If the jack is off center on the wheel there is a chance that it could happen. You'd have to be pretty far off center though I would think. The stands could easily be designed to center the wheel and jack together. I'm seeing some other things I don't like about this method now that I watch the video again. I still don't see it as being more unsafe than any other jacking method.
[QUOTE=Tom400CFI]How do you figure that? Jack stands were engineered specifically for that purpose. Note that I said "purpose"...not capacity. Both can have way more than enough capacity (it would seem from your calcs) but the car can still roll on wood, the wood can topple...it all depends on how someone built their cribbing...which is a variable. Stands are engineered for both capacity and purpose. You put them under the car in the proper location, on level ground....it's pretty hard to mess it up.[QUOTE]
Sure. I'm guessing that you could google just about anything and find a failure. That doesn't make "jack stands unsafe"....nor does it make "contraptions-home-made-from-wood", more safe than jack stands. I looked at that thread...the stands he was using look like garbage to me.
What are the statistics for failed jack stands vs. failed home-made jigs? That would be more meaningful data (to me, at least).