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I still haven't figured out who makes the 'best' stand.... certainly NOT my Harbor Freight stands, of course... but I'm not clear on where to spend the 'quality jack stand money'....
Dan
Wow. The weld on those jacks in that post do look bad. That's pretty disappointing that they would have let those through QA. Made me go inspect my jacks. My welds look fine. All sides on all 4 jacks look like this.
I still really like these jacks and in fact all the other recommendations on Garage Journal is why I bought them.
Also, pits are not legal in many residential areas. Gasoline and other hydrocarbon fumes are heavier than air and can settle in a pit, with possible ignition consequences.
As well those hydocarbon fumes and CO can cause asphyxiation hazard.
I note that no one has posted here who has actually been crushed by a falling car. Is it really such a concern?
Originally Posted by polecat702
With all the money some of you guys have, why not just buy a lift, and be done with it?
I did, but I'm still nervous. Max Jax says 5" of concrete are needed, but is OK with 4", which is what I have, nominally. It is common to slope the slab downwards towards the door for drainage. Is the bottom sloped down, or just the top meaning it is thinner near the door? Is the bottom of the slab nicely compacted, or wonky? Is a bolt near a bit of the steel mesh weaker? Doesn't the top of the slab need this mesh the most - the tension side of this beam - when it is actually near the bottom? And, by God, I'm a metallurgist, familiar with various failure modes, including the statistical nature of the strength of brittle materials in tension.
(I'm fine with the lift itself, good honest metal, even if Chinese.)
This is what I'm thinking about while laying under 3500 lbs. I also try to think of something to support the car if the car falls. If it were to come straight down, easy. But one side will collapse first, twisting the car wildly on the way down. An elegant solution has eluded me so far. Except:
I've started preparing a site for a new garage, which will have grossly over-designed concrete and bolts, in the finest Porsche tradition. I'll move the Max Jax out there, and I think I'll get a 4-post lift, too.
Collapsing jackstands is not a myth. So you are doing the right thing.
Not a myth, but the video you linked to did point out it took considerable force to cause a collapse. Not something you are going to do accidentally with your foot or even a blow with a hammer. He had to pry it up with a lever and the more weight on the stand, the more leverage it will take.
Here is just the video in that link, very interesting:
Way more people die in their bathrooms than ever get killed by terrorists but so far no one has decided to bomb bathrooms out of existence!
Jackstands are and remain a very safe way of supporting loads. As I said earlier if you are supporting the car evenly on 4 stands should one fail the car will not collapse on you. Back up the jackstands at whatever end of the car you are working on for additional assurance and forget about it.
People die in cars but that does not stop folks from driving them does it? As for things like quality of welding and Chinese steel again put things into perspective. Jack stands are typically fabricated from mild steel plate about 5mm thick - agreed? Compressive strength is close to the tensile value in the region of 20k psi for mild steel. Assume total load spread over 3 jack stands and you end up with 550kg per stand- put this on a 3 tonne unit and the thing is barely stressed and that before one consider the over design inherent in the thing that willprobably carry over twice the rated load before it fails. Welds on structural steel are generally poor quality but are still more than adequate- compared to pressure vessel welds they look like pideon sh*t.
By all means be concerned but not paranoid about these things. Worst failure I have experienced was at the local dealers- my 928 was on a 4 poster, I was lowering the car but not paying attention and the mechanic screamed at me to stop the descent- the release dogs on one side had not worked and the thing was dropping on one side only and the car was at a silly angle like 45 degrees or so it seemed. Thus professional kit can have problems never mind DIY made in China crap.
We are probably far enough into the thread to air stupid confessions:
I was doing the tranny mounts last year, using the floor jack to raise the transmission. I worked under that car for an hour, wrestling things around-- and then realized that I had raised the whole rear if the car off the jack stands, lift bars and all...
could have been a case of natural selection right there.
05-09-2017, 05:56 PM
