Donald,
I agree that concrete has very little tensil strength. If the picture of
the lift in the reference is accurate, it seems that the load will be
balanced side to side & that there would be no overturning moment on the
base plates. The cross rail spreader at the top also helps in this
respect. If there were a significant overturning moment, I doubt that
the tensil strength of four inch vs eight inch concrete would make much
difference. I suspect that there are stringent safeguards built into the
system to prevent unbalanced loads, both side to side & fore & aft.
"Heavy-Duty Dual 3/8 Equalizer Cables, Dual Hydraulic Direct-Drive
Cylinders". In the event that the safety load balancing systems were to
fail the whole thing might come crashing down.BTW, can someone tell me
what an "assymetric lift" means? Everything looks symetrical to me.
Dave Russell
Donald H Locker wrote:
> But realise that an unbalanced load on those 17x17 base plates would
> only have to have the CG 8-1/2 inches to one end of the centerline of
> the base plate to place a load varying from 40 psi at the one end to 0
> psi at the other. Just a little further and the concrete at one end
> goes into tension, which it likes very little. The concrete won't
> fail in compression, but in tension and torsion. I'm not a civil
> engineer, but I'd check with one before loading a vehicle onto such a
> lift.
>
> JMO.
> Donald.
>
>
>>Date: Wed, 20 Aug 2003 19:06:39 -0600
>>From: Dave & Marlene <rusd@velocitus.net>
>>
>>
>>Wayne,
>>
>>I agree with Derek on the pad height definition. As for the needed
>>concrete thickness, with the two 17 inch square base plates & a total
>>weight of 11,325 pounds (lift weight plus max capacity) there would only
>>be about 20 pounds per square inch load on the concrete floor. If there
>>were only one 17 x 17 base plate the load would still only be 40 psi.
>>
>>For a comparison, a 8,000 pound vehicle sitting on a four by four inch
>>tire contact patch would apply about 125 pounds per square inch to the
>>concrete. A four inch slab should be more than adequate.
>>
>>Dave Russell
>>
>>Derek wrote:
>>
>>>Wayne
>>>The specs on the web page you reference state -
>>> - "Minimum pad height 4"/102mm"
>>>Isn't that the minimum height of the steel arms (and pads)
>>>that need to go under the vehicle before lifting?
>>>
>>>I don't think there is any concrete "pad" spec called put -
>>>at least not on that page. I agree that 4" concrete seems
>>>too little - but I'm not a concrete engineer.
>>>
>>>Derek
>>>--- Wayne Farrington <w.farrington@verizon.net> wrote:
>>>
>>>
>>>>Well, I've come to the end of my rope regarding not
>>>>having a lift in my shop,
>>>>so I'm going to buy one. Thinking about this one:
>>>>
>>>
>>>http://www.gesforless.com/product_info.isg?products_id=343
/// unsubscribe/change address requests to majordomo@autox.team.net or try
/// http://www.team.net/mailman/listinfo
/// Archives at http://www.team.net/archive/shop-talk
|