Bruce SEA 993

WHB Porsche: You are not quite thinking right here...the lift weight is 1300 lbs and the load is 3100 lbs or so for the 993. So the total is 1300 for the dead weight of the lift + 3100 for the car for a load of 4400 lbs. I was looking at 8000 lbs which would allow me a "car" weight of 6700 lbs...mebbe if I lifted a Hummer.

You are right...the capacity is 8000 lbs plus the dead loada of the lift....9300 lbs. My heaviest car is the SL500 at 4100 lbs so I am under the calculated load at 8000...

Ciao

Garth S

My two post lift is sitting on 4" min ( 4.5" max) of 4500 psi concrete - no issues. I poured the slab when still in 'jack stand' mode, so had not anticipated a lift: had it been the other way around, I would have poured 6" .... just to make me feel good

4X4SCHE

Bruce,

Want to see if we can get a good price on two delivered to the Seattle area???

John

97C2s911

I purchased a 2 post lift from Greg Smith a few months ago at a good price but the shipping was $ 400 to Seattle . Still it was only around $ 2000 .
Garage slabs are typically 4" deep the one thing you want to be sure having done plenty of concrete drilling is that when drilling the parabolt imbedded in the concrete that you don't drill thru to the dirt
it happens . So set the roto hammer to the imbedment you want . If the concrete is 3" or less that would be pretty thin. Simpson has a new strong bolt that is a really good imbed bolt

4X4SCHE

My concern is the twisting moment if the weight is to the front or the back of the lift. Why not saw cut an 18" square hole in the concrete for the post base and dig down a couple of feet and put in a footing? You could embed J bolts. I would trust this more than bolts into a few inches of concrete slab. You could drill into the side of the slab and epoxy in some rebar to tie the footing to the slab.

John.

Bruce SEA 993

Hey John,

Did you drive your car into work this morning....I think I saw you on 405 at about 85th or getting off at 85th?

I am rethinking the lift type that I want. I would really like a two post but I don't really have the room in a normal or slightly larger than normal garage both in width and height.

A scissors will do what I need and hide under the car when not in use. I can only raise about 48 - 56 inches anyhow. I just thought it would be nice to have a clear area under the car. I don't think there is much to get at in the area covered by the scissors lift anyhow.

So that is my yhoughts for now...thanks for all the great replys!

autobonrun

I assume that concrete ratings are taken at a particular spot. So if my math is correct, it's really not the entire 3000 lbs that is exerted on a given spot, but the weight divided by four since the weight is spread over each of the tire contact points. A 3200 lb car with an 1800 lb lift is more like 5000 lbs / 4 or 1250 lbs on a given spot. If my assumption is correct, a 4" thick floor with a 3000 lb rating is more than sufficient.

Now if my assumption about how a floor is tested is incorrect, the statements go out the window.

Edit; I think my above assumptions are correct. The rating of 3000 lbs is actually pounds/sq in. Since the four contact surfaces over which a car/lift has it's weight spread is more like 36 sq inches per leg (assuming 6" square feet), I don't see a problem. See the description "what is 3000 lb concrete" in the attached link.

http://www.cement.org/basics/concretebasics_faqs.asp

Bruce SEA 993

From the Ase Bend pak web site:
Large 17" x 17" A36 base plates. (for a 2 post lift)
Large Baseplates - 12" x 12" baseplates provide solid stability (4 post lift)

So the square inches are a bit more as the load is spread aout over more area.

Ron

I had a geotek engineering firm work on my project and a house addition.


I don't know what technique or process was use to test the concrete samples. All I can tell you is the technitcian was on the site when the trucks were pouring the concrete and he filled a number of tubes with concrete. He left them on the site for about three days then came back and picked them up. They gave me written reports as the psi at 1 week and then at 28 days. The 28 day rating was 4640 psi. I specified minumum psi to be 4000.

WHB Porsche

Yup. The concrete is poured into lubed up rubberish cylinders and allowed to dry. Normally three samples are taken, and they can be tested anywhere from 1 week to 28 days. The rubber casing is chipped away before the test, revealing the concrete cylinder. This is measured very carefully to determine it's height and diameter, the latter of which will be used to determine the surface area of the top of the concrete. This cylinder is then placed in a hydraulic press and weight is added until the concrete fails. This weight, divided by the SA of the cylinder, is the concrete's PSI.

Bruce - when you said 16 or 18 it seemed like you were off just because those values are so low, but even using 9300lbs it comes out to ~16psi. I didn't realize the feet were so large (17" x 17").

matt777

I would think that the preparation of the pad prior to pouring would be the most important part.

Colin 90 C2

to ease your fears, I installed a two post lift about six years ago. it was installed on a standard poured concrete floor that looked like it ranged from 3.5" to 6" thick. I used Hilti stainless steel 3/4" drop in anchors.
I added an extra 2 1/2 feet of garage door rail to the bottoms of my existing rails and have the garage door opening up to almost the ceiling height. I also raised up the opener. My garage height is about 10 1/2 feet and the opener hangs down about 8".

My car has been sitting on the lift for over a year with no issues, except that I own a Porsche and I can't drive it without an engine and transmission installed.

I am considering getting a mid rise lift for another bay.

I am sure that your slab will hold the weight.

Good luck

luvmy356

Bruce, I plan to order a few lifts from Greg Smith in the next month or two depending on how quickly my construction goes...let me know if you want to piggy back if it will save on freight or costs. Maybe they could give us a "group buy" rate.

Bruce SEA 993

Thanks Perry...just what I needed to kick me into gear!

FisterD

Just installed Greg Smith Atlas Nine lift Yesterday, woohoo!