2 post lift on different slabs?

[Dr.HairyOlds]

Just ought a house with a 25'x26' detached and 30' x 40' detached (Sorry, pics to come). Trying to figure out where to put my Mohawk lift. The floor is either jointed into (9) approximately 10'x13' sections. Where I want to put the lift will keep away from the joints but will require each post to be on a separate section. Not the optimum but what is everyone's opinion on this?

Shop is less that 2 years old. The guy who built it lives next door. Haven't spoken to him yet to find out thickness and quality of the concrete. Any questions you think I should ask would be helpful also. Thanks

 

[Makoto]

a drawing might help. this will probably depend on the depth and size of the two slabs if its possible.

 

[ccoorreeyy]

Prob just a cut and not separate parts.

 

[rburke65]

My Mohawk is like yours.....I think. But it's just a saw cut on my slab. I think you will be ok if you have the thickness. Your going to like or lift.

 

[sberry]

It will be fine, rigged right up a Mohawk will lift a car without being bolted to the floor. As long as the slabs are not moving what difference would it make?

 

[Dr.HairyOlds]

Thanks everyone. I wanted to believe it would be fine. I've had to lift for a while but just moved down to SC. The rest of the shop should be following me. Real excited to start setting everything up.

 

[Shadowdog500]

It will be fine, rigged right up a Mohawk will lift a car without being bolted to the floor. As long as the slabs are not moving what difference would it make?

You must be thinking of a different lift!

I can't think of any 2 post lift that would lift a car without being bolted down.

Chris

 

[Shadowdog500]

Here are the slab requirements for a mohawk lift. http://www.mohawklifts.com/consumer/library/Slab_Req-Reco_2-2010.pdf

It says both posts have to be on the same slab.
and that all anchor bolts must be at least 6" from an expansion seam

 

[Dr.HairyOlds]

Thanks shadowdog. I have seen that and am far enough away from the expansion seams. But realistically, I want to know what the potential issues are with this. After a little research, rotary and the like don't mention anything other than keeping holes away from the expansion seems and even when new pads would need to be poured, they allow for two separate pads. So I'm curious about more critical it is that they be on the same pads. Each column will still be well anchored to a large (10'x13' minimum slab).

 

[killahog]

Pictures would help determine if you are dealing with what you are referring to as (expansion seams) or if they are control joints.

 

[sberry]

How fussy can this be in the fact that they bolt them down to uncontrolled concrete by the 1000's by relatively semi skilled people with no inspection.

 

[sberry]

I can't think of any 2 post lift that would lift a car without being bolted down.

Not every 2 post will but you can do it on a Mohawk. Well you might be able to do it on some others but they have an awful small foot print and front to back loading would have to be about perfect

 

[Shadowdog500]

Not every 2 post will but you can do it on a Mohawk. Well you might be able to do it on some others but they have an awful small foot print and front to back loading would have to be about perfect

I respectfully disagree. Those columns would justs fall onto the car if you tried to lift the car without it being bolted to the floor.

Here is a photo of my wife's toyota on my Mohawk lift taken a few minutes after the lift install was complete. I put the photo in force effect and scaled everything to the Mohawk blueprints. Under full load the outside bolts have over 16,000lb of tension on them.

Chris

 

[sberry]

The pads have cleats on them. if they are dogged on to the frame it keeps the posts from falling inward. You would be correct if you measured every arm individual without chocking the spread but if you put a be4am between the top of the posts there would be relativly no stress on the bolts. You can rig the arms in the same fashion.

The thing is designed and mounted so the bolts are adequate for any rated load on it regardless of the basic rigging, rigged right there is almost no load.
(

 

[wssix99]

It says both posts have to be on the same slab.

If the joints we are talking about here are just saw-cut or troweled control joints, then it is a continuous slab. These just control the shrinkage cracks that happen in every slab and the cracks should not be wide enough for the cracked sections to come apart or move differentially.

If the joints are expansion or isolation joints where the two sides are isolated, then that's a problem.


The posts still need to be kept away a certain distance from control joints, but they should be able to straddle them just fine.

 

[Shadowdog500]

The pads have cleats on them. if they are dogged on to the frame it keeps the posts from falling inward. You would be correct if you measured every arm individual without chocking the spread but if you put a be4am between the top of the posts there would be relativly no stress on the bolts. You can rig the arms in the same fashion.

The thing is designed and mounted so the bolts are adequate for any rated load on it regardless of the basic rigging, rigged right there is almost no load.
(

I have a system one, and the plates don't have cleats that would stop the arms from tilting in. Do you have a photo of what you are talking about. With enough modification, like using the beams you suggested, I imagine any lift could be made to support a load without being bolted down.

Mohawk does make a portable heavy equipment lift for servicing heavy vehicles while on the road that don't need to be bolted down(see photo below). Is this the one you are thinking about??

Chris

 

[Dr.HairyOlds]

I've slid the posts around the shop myself. There is no way this type of lift would support a vehicle not bolted down. Even if there was some sort of cleating. Ever walked on pavement or concrete wearing cleats? Not much grip.

I would love to send some pictures but my camera battery has died. Out of curiosity, what is the issue if the joint is an expansion joint and the bolts are far enough from the edge. To understand this is to understand how it is supposed to be supported:

Either the support depends on a big enough weight of concrete to more than counteract the weight of a vehicle, then as long as the separate slabs are large enough no problem

Or do the two posts need to be on the same piece in order to have tension and compression on that piece to between the posts to keep everything together.

I could see either way other than that other 2 posts lifts allow separate footings

 

[lt1driver]

your life but I would not until I called mohawk and had concrete depth and psi checked, mohawks are heavier and better than other lifts imo, however your life so do what you are comfortable with and good luck.

 

[wssix99]

Out of curiosity, what is the issue if the joint is an expansion joint and the bolts are far enough from the edge. To understand this is to understand how it is supposed to be supported:

The best way to envision this is to look at the post from the size and cut a cross section of the slab. The slab and the post form an upside-down "T" shape and the legs of that "T" give you the stability vs. tipping and counteract the leverage that a car at height on the lift would create around the base of the lift.

Either the support depends on a big enough weight of concrete to more than counteract the weight of a vehicle, then as long as the separate slabs are large enough no problem

In order for this "gravity" system to work, you'd need an impractical amount of concrete in a "footing." By the time you got to that point, you'd have so much concrete that the thing would work more like extending the post of the lift and it would be buried deep enough to work like sinking a telephone pole in the ground. In short, this could work but its expensive and impractical.

Or do the two posts need to be on the same piece in order to have tension and compression on that piece to between the posts to keep everything together.

This is correct. When you look at the lift head on, the "T" shapes meet in the middle and need to be joined together. If those "T" supports are not joined, the lift could have a tendency to sway side to side - or both columns could tip inwards.

Even if you follow the lift manufacturer's recommendation for pouring new pads, they require that the pads be keyed to the slab (with pins or a keyed shape) so that you still get the continuous connection.

 

[Dr.HairyOlds]

Update for anyone interested:

Talked to the previous owner/builder. They are just saw cuts, no issues there thankfully

Now about to truss above limiting my lift height...

 

[sberry]

You can rig the arms to the vehicle so the posts don't tip together, but,,,,,,,,,,,,,,,,,, because it will stand there doesn't mean its safe, the point being is that its not as fuzzy critical as one may think.
The Mohawk is huge, look at the footprint of a Bendpack and it spec the same concrete. You don't need reinforced, lifts a big ole truck on 2 skiny poles n 4 inch home owner concrete.