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backwaterdogs 07-04-2014 08:24 AM

question about 2 post lift
 
Hey everyone, been reading a few threads about installing a two post lift and thot I'd better ask some specific question for my situation as it is a big safety concern.

I have 40x60 quanset type shop, mostly unheadted. There is a an existing 20 x 60 slab, 4" think that is in great shape, litterally not a crack, been there for years.

The rest of the area is gravel. I plan to make several more 10 x 40 pours (as that is what I feel is managable for me. On the first 10 x 40 section I'm pouring am planning on putting a 2 post lift.

Current plan (until I read further here) was pouring this slab 5+ inches of 4000psi fiber reinforced concrete and then bolting the lift.

The current slab and the entire gravel area is surrounded by a good and stable stem wall that will serve as the outside form for these new slabs. I intended to tie the new slab to the existing by drilling and dowelling 1/2 rebar(but no expoxy) to the existing slab.

From my research, I believe the plans I have to pour against and attach to the existing slab are sufficient, but after reading here am concerned about plans for the 2 post lift.

Do i need to perhaps have say a 3x3' section where the post will go 8", 10", 12" thick with rebar?

In the new 10x40 section, the use of dowels to existing slab is there just for shear strength as I understand to prevent new slab from dropping. Does having a lift affect that greatly? If the 3x3 extra thick pads are required, should they be indenpendent of the new slab for tied in with rebar?

last question, is it better to say f-it and put in a 4 post lift?!?!

thanks!

64SS327 07-04-2014 08:36 AM

A two post lift is the only way to go. The two post offers full access to the suspension and underside of the car. A four post isn't a whole lot better than working on the floor with jacks imho.

As far as tying in with your current slab I think you have the right idea. I would contact the manufacturer of the lift to see what they recommend as far as how thick the slab should be.

lakeroadster 07-04-2014 09:06 AM

I have a 2 post and a 4 post. I prefer the 2 post 95% of the time.

As for slab requirements... don't take advice from a bunch of folks with no skin in the game. Pick a lift and follow their specifications.... spec's. change based on lift capacity and design.

Hope that helps.

John

OneMoreTime 07-04-2014 09:38 AM

There is not such thing as too much concrete and re-bar when putting one of those things in in my book.. Remember you are likely to have a full size pickup or a large car up on that thing and there is a large overturn moment when you do that.. it is not the downthrust of the weight it is the over turn of an unbalanced load on the lift.

Get the specs from the maker of the lift and do that at the minimum on your footing for the lift..

Sam

timothale 07-04-2014 12:39 PM

post anchors
 
I made a plywood template to match the bottom of the lift posts. I dug the areas about a foot deep and leveled and set the bolts about with adjuster nuts about 2 in below the finish floor, and enough threads above the finished floor level for final attachment. That is the way we did large steel columns for schools, warehouses, etc. after we poured the concrete I installed the lift. I had a gap under the steel plate and couldn't find my bag of NON_SHRINK grout. I had the roadster up a few times working on it. everything was ok. then I raised my 4 door F350 dually dump truck and the base plates bent, I carefully got the truck down, re=set the adjuster nuts to plumb- level the steel lift posts then went and bought a new bag of the grout, mixed it to a dry pack. and rammed it under the steel base plates..That is what I should have done the first time. Mosts lifts say they can be installed on a 4 in slab with 1/2 anchor redhead bolts. When we built schools, the bolts all had to be pull tested. that is why I went with 12 in long L type anchor bolts. My 2 post lift does not have a cross bar at the top between the posts. I have the cables in a recessed pan so the floor is flat. I have thought I could add some more steel go higher and tie the top of the posts together, I have 16 ft side walls . plenty of head room.

59 wagon man 07-04-2014 08:56 PM

had a 2 post lift and sold that to buy my 4 post and i'm glad i did. i will be the first to admit it is easier to work on the car on a 2 post lift but i bought a harbor freight air jack and with the tray between the ramps i have no problem lifting the car. mind you that most of the time i use my lift to allow me to store 2 cars in my garage. i used to hate having to get out and set the posts, especially on my mustang as if i wasnt parked just right i couldn't get the arms under the car. so i would have to get back in and move the car now i just pull in ,get out and hit the button. As in life everything is a comprimise

Scooting 07-04-2014 10:54 PM

If I were pouring a new slab or area and wanting to place a lift, I would get a zonotube for concrete (cardboard tube forms at your lumberyard) 12" or larger in diameter and cut tubes for each post at least 2 feet long, 3 feet being better. Place these tubes where the lift posts are to be located, insert rebar and J bolts for attachment and pour. This is over kill per the manufactures of the lifts. But think of it this way, it is cheap and when you put the weight of a car/truck on the end of a lever arm (your lift post) and push it out of straight for any reason, You have this big counterweight encased in earth to react the force. It would be nice to have the tube a couple of inches higher than the finished floor - that way the lift connection should never get wet and rust nor come into contact with what ever you just spilled all over. Total cost would be minimum considering the pouring of a slab. Total savings from overbuilding when a stop fails on one leg and the whole thing tilts could be large.

crussell85 07-05-2014 01:27 AM

Contact the manufacturer, they pay engineers thousands of dollars every year to answer these questions. I imagine since its overhead hoist the foundation plans will be a 4 to 1 ratio meaning the foundation will be four times the amount that's needed for safety. If the lift fails and causes injuries or worse and the foundation is not what the manufacturer requires (not recommended, requires) then they'll have a quick route out.

toddalin 07-05-2014 12:47 PM

I have the asymmetrical AutoLifter 9000 (9,000# rated/27,000# maximum) two-post for cars and trucks.

The installation manual called for a minimum of a 6" pour of no less than 3,000 psi with wire mesh or rebar reinforcement.

When cured, the pad was drilled and because the garage floor slopes toward the door, shims were added to the low side to level the lift.

35terraplane 07-05-2014 01:10 PM

I know most like a two post, but I have a four post for two reasons. When in high school I saw a car fall off a two post at a service station fell right on another car. Granted the car was more than likely not on the lift right, but never the less it fell off, it is pretty hard for that to happen on a four post. Number two reason I can move my 4 post around, No I don't have the 4 poster bolted down, One reason I have a heated floor, I have had one for years and never bolted them down, and I have wheels to move it that came with the lift. If I do move it I can square it up and I'm good to go.

Bob

ogre 07-07-2014 01:07 PM

there is no need to dowel your slabs together unless your planning on run loaded 18 wheelers at highway speeds
also no need to pour a thicker 10x60 slab for a single hoist, just thicken a 3x3 area under each post or a 12x12 are under the lift
i prefer drop in anchors over j-bolts as locating the bolts can be challenging for an experienced millwright
and this is not a recommended install procedure by the manufacturer
through drill all the anchor bolt holes, this takes no strength from the install and
makes it easy to pound down the anchors if you ever move the lift
use the size and number of anchor bolts as recommended by the manufacturer

we have 4 two post lifts in the shop and have moved the shop 3 times in 10 years.
every shop has had unknown concrete with a min of 5'' concrete to deal with.
the only time i worry about a hoist is lifting my extended cab 8 foot box or the f250 4 door trucks
when we get them up in the air we put a jack stand under the hitch for stability

definitely do not use the sonotube idea that has fail written all over it

backwaterdogs 07-07-2014 03:37 PM

Thanks everyone for all the input

the min spec from rotary is 4." of 300o psi...this where I'm getting things to now:

Overall thickness is about 5", will use 4000 psi with fiber reinforcement. I also done as suggested anc reated 3.5 x 3.5 ft area for each post, with 4" of well compacted ca6 and an additional 4 inches of concrete + rebar. So under the posts, will have about 8" of 4000 psi fiber reinforced plus rebar.

Based on other input, I alredy dowelled it to the other slab...hopfully just overkill and not problematic.

I'll try and post a pic later of the prepped area.

Great forum, btw thanks, all!

hduff 07-16-2014 02:36 PM

I have a 2-post, a 4-post and a Kwick-Lift. All have their uses.

The 2-post is great for suspension/brake work. The 4-post is great for everything else. The Kwick-Lift is great for body work and under-dash work.

For my 2-post lift, I prepared 4'x4'x2' deep footings tied into the surrounding floor with re-bar; I used a 5000-PSI concrete that the pros that installed the lift recommended.

[email protected] 07-16-2014 02:49 PM

I have a 2-post and love it. I installed it on a new, cured 4" slab but had to straddle an expansion joint which is a no-no. Sure enough, one post began to rubbleize the cement, I'm sure because of the weakness of the expansion joint. I cut out the cement a foot around the base of the post, dug it down about 10", jambed rebar under the exissting slab and spanned the new hole and refilled it with QuickCrete. Of course I installed new J-bolts B4 pouring the cement. A Sunday's work and I was back in business. The other post is fine, cement is as good as the day it was poured. I would pour your slab 6" a couple ft around the each post, no expansion joints in the area, put a grid of 1/2" rebar there and you could iift a 747 with no problems.

backwaterdogs 07-16-2014 04:02 PM

Test from phone


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