A different way to anchor a 2 post lift

[camnick]

I am purchasing a used Forward 12000lb 2 post lift. The current owner has it mounted on 4" of concrete. It would scare the hell out of me to mount the
lift in my barn on just 4" 4000psi concrete. The current owner said he used to install lifts. He said I could get a 1/2"-3/4" steel plate to put under the each post leg. The plate would be much larger than the posts and the edges of the plates would be anchored to the concrete also. Has anyone ever done or seen this performed?

 

[nehog]

As always, contacting the lift maker is the best answer to such a question, but IMHO that would work well. Plates would have to be large enough to give a good footprint, say 2x2 or larger.

 

[skyking]

I have installed several 2 post lifts. I try to mount them in 5" but that is not always possible.
i dont worry because the beam across the top gives it strength in that direction ,and if you are loading your vehicles properly they are applying the force straight down. Just one bolt anchored in concrete is strong enough to nearly lift the building. Those are usually 3/4" .
To set your mind at ease think of hanging your truck from a chain suspended by one 3/4" bolt. That is one hell of a bolt ,it would have no problem holding your truck up.Lifts usually have 10 bolts. I have Never heard of a lift failure due to installation.

 

[wssix99]

If you put a 12,000 lb vehicle on a lift with each stock base plate on the bottom of the lift posts being 10" X 10", that would give you 200 square inches of bearing surface. That translates to 60 psi of force on the concrete. Your existing slab won't even know the lift is there...

The biggest issue for a two post lift is the depth of the concrete, which will resist bending when a load is slightly off center. As long as you have 4 full inches of depth, you'll be fine.

 

[camnick]

I really appreciate the input. That does make me feel a little better. I may make the plates long enough, maybe 3 feet long, to help resist it from tipping

 

[Zeke]

I really appreciate the input. That does make me feel a little better. I may make the plates long enough, maybe 3 feet long, to help resist it from tipping

I agree. How does anyone really know the center point of any vehicle? It's not like they place an arrow along the rocker.

 

[mk3cn4]

I respectively disagree, the 2-post lift acts as a lever against the outer bolts at a multiple of the vehicle weight, likely several times the vehicle weight. Especially true if it's a baseplate lift. I would expect an UPWARD pressure on outermost bolts to share each more than 10,000 lbs. in heavy lifting.

Think of the lift post like a crowbar levering against the outermost anchor bolts, lever has several feet on one side and mere inches on the other. Lots of leverage lots of force. You're still probably OK but this thread seems to discount the amount of force on this lift, don't underestimate the risk.

 

[Zeke]

By "respectfully" disagreeing, I think you and I are on the same page.

 

[mk3cn4]

I was disagreeing with the post 3 messages up, where it's stated that the concrete will barely know the lift is there. Literally tons of "upward" pressure on that concrete, and DOWNWARD as well as the inside takes almost all of the brunt of the load, not the entire plate. Sorry should have quoted, sort of a newbie here.

Found this link for another thread that shows forces:

http://www.maxjaxusa.com/faqs/common-concerns.html

 

[nehog]

I agree. How does anyone really know the center point of any vehicle? It's not like they place an arrow along the rocker.

There is a booklet published each year listing cars, where to lift from, and such. My lift came with the book, and you can order updated copies (IIRC, about $10 to $20) as you need. Since all what I lift is older, my book (two years old) is still fully adequate. But, I also find that after a while you get a good feel for where the center of balance is for the vehicles you lift the most.

 

[skyking]

I was disagreeing with the post 3 messages up, where it's stated that the concrete will barely know the lift is there. Literally tons of "upward" pressure on that concrete, and DOWNWARD as well as the inside takes almost all of the brunt of the load, not the entire plate. Sorry should have quoted, sort of a newbie here.

Found this link for another thread that shows forces:

http://www.maxjaxusa.com/faqs/common-concerns.html

Doesn't matter ......niether of you know what you are talking about.

 

[Zeke]

Doesn't matter ......niether of you know what you are talking about.

It is true that I don't have a lift and have never used a 2 post lift. mck3cn4 and I are making statements in the inquiring sense. At least I hope that is how mine looks since it has a question mark.

The dynamics of load have to be an interesting consideration. Just how does one know the weight distribution once the car is on the arms? I mean if it isn't obvious as the car leaves the ground. There has to be some fore and aft load. Perhaps even if they are not equal, there is never a negative load on one side.

But since you brought it up, explain it.

 

[skyking]

I started work as an auto mech. when Kennedy was humpin Monroe .I have lifted thousands of cars and trucks. you get a sense of where to place them.You also get in the habit of pushing up and down on the vehicle front or rear to see that it is stable before you take it all the way up .I have seen a lot of cars fall off lifts over the years, but never because of the lift.
The true danger of a lift is the fact that they are SOLID. My poor old head takes a beating under a lift. I am 6'2" and finally bought me one of those biker skull helmets to avoid anymore scars. A lot less bleeding. I did not want to sound so kurt before ,I just wish everyone had a lift .....they are great.

Also they now make roll around lifts. These have the same base size and you can roll each post against the wall. As a fleet manager for a school district (168 school buses and service vehicles. I considered buying some for my shop , but they were cost prohibitive.$$$$$$$$$

 

[mk3cn4]

Doesn't matter ......niether of you know what you are talking about.

How about instead of making a rude statement like that you instead just talk facts and make your arguement?

Here are the facts that I am basing my opinion on. If you disagree with this, how about attacking the facts or ideas instead of personal attacks against the person (me)?

http://www.maxjaxusa.com/faqs/common-concerns.html

"The concrete anchors actually secure the lift to the floor and keep it from tipping over. And, believe it or not, this is the way that most two-post lifts do it. The top crossbar found on most commercial two-post lifts is not intended to be load bearing. It's just a simple, elegant way to route the equalizing cables and hydraulic hoses. Although clear-floor style two-post lifts do have a crossbar, many popular floor-plate or base-plate styles are void of one."

I have decided that I am erroring on side of caution. I've never seen one of those supporting overhead bars crushed, but you're willing to tell someone don't worry about the bolts? I'd never advise someone don't worry about the anchors because your overhead bar takes all the brunt. Those bolts are there for a reason.

You might be right, I might be right, but statements like "you don't know what you are talking about" are uncalled for.

 

[cyamaha2007]

If you add a plate below the lift the lowest point will raise. So the arms might clear a vette or trans am originally but now they probably wont due to the plate. If you are worried about the install just cut a rectangle where you want your lift lets say 1.5 feet longer and wider than the lift floor contact points. Bust up the floor and dig a 12in hole epoxy some dowels into the old slab and pour new crete. It would be cheap and legit. Just be sure that a anchor doesnt land within 5x the diameter of the anchor hole. Heres a article on the matter. Generally, the spacing requirements used by the concrete anchor industry are that the anchors should be spaced a minimum of 10 anchor diameters away from each other and a minimum of 5 anchors from an unsupported edge of concrete. Spacing closer will cause a decrease in holding values or there may not be any holding values at all.
The thickness of the concrete that the wedge anchor is placed into is critical because each diameter of wedge anchor requires a minimum embedment. For the wedge anchor to reach its minimum holding values in concrete, it must be set in the concrete at a minimum distance below the surface of the concrete. The thickness of the concrete is thick enough to allow the anchor to be placed so that minimum embedment is reached. The wedge anchor must also be placed so that it is no closer than 1.5 diameters from the unsupported side of the concrete.

 

[ZRX61]

I agree. How does anyone really know the center point of any vehicle? It's not like they place an arrow along the rocker.

You'l soon get the hang of it, just raise it up a foot & give it a jiggle. If it falls off the back of the lift, you should have parked a bit further forward

 

[alan camby]

If i had a 2 post lift (dreaming) and only had 4" concrete to mount it on. I would consider busting up a square section where each post will set, Something like 4'x4', and make a foundation for each post that is a foot or better thick. This way the anchors would be mounted deep in the concrete and there would be no worry of them coming out. I don't think this would be very difficult to do. Just use a abrasive concrete saw to cut out the sections.

This is just a quick thought of mine. Would do a little more research on how to make this foundation. Could study the plans for a small floor mounted Jib crane for example. Most jibs over 2000lbs require a foundation.

Seems easier then pouring a new garage floor, or worrying about the floor you have.

Just thinking out loud, I am not claiming to know the right answer to your question.

 

[camnick]

I'll have to think this one over for awhile.
Where is the best place to get the anchors?

 

[cyamaha2007]

hilti anchors are great we use them all the time. I would do it to the lift manufactures specs. No need to worry about it. I would think they would call for 6+ in of concrete at 4000psi. No anchors within 1ft from a crack, expansion joint, or control joint. MY lift came with specs for on a floor or on a footing. If you cant find specs for your lift look at mohawk they are pretty stout. pouring a footing for it would be pretty easy and wouldnt cost but 500-1000 max.

 

[abstamaria]

I am not sure what purpose the steel plate will serve, Camnick. The plate will spread the load on the floor I suppose, but it will be the bolts holding on to the concrete that will keep the posts from tilting. I am not an engineer and not an expert by any means, but am just passing on the little I learned (probably incorrectly) from reading. I have a MaxJax.

The Wej-it anchors that come with the MaxJax work with a minimum 4" concrete depth, and you may find a similar mechanical anchor that will work with your lift's load requirements.

I also thought about epoxy or chemical anchors, which I think are superior (although mechanical anchor are good enough). I checked with Hilti and they did an analysis of the requirements and recommended the appropriate anchors. They even sent me a graph showing their analysis. In the end, I used the WejIts that came with the MaxJax.

Good luck.

Andy

 

[mrobins297aaa]

I'd be careful about adding any plates to the bottom of the lift, like cy said that will raise your lifting arms and could be a real pia if they won't fit under the vehicle your trying to lift. whats wrong with the base plates that are on there?

mk3 I have to disagree with your statement about the top plate connecting the two post being just a elegant way to hide the cables........on the two bendpak lifts I've had and installed that plate is quite stout and more than adequate to hold those columns apart even if there were no anchors in the floor.

 

[mrobins297aaa]

I have installed several 2 post lifts. I try to mount them in 5" but that is not always possible.
i dont worry because the beam across the top gives it strength in that direction ,and if you are loading your vehicles properly they are applying the force straight down. Just one bolt anchored in concrete is strong enough to nearly lift the building. Those are usually 3/4" .
To set your mind at ease think of hanging your truck from a chain suspended by one 3/4" bolt. That is one hell of a bolt ,it would have no problem holding your truck up.Lifts usually have 10 bolts. I have Never heard of a lift failure due to installation.

best answer........most people don't give these anchors enough credit, there super strong and don't pull out. we use to hang ac units that weighted as much as your truck from the ceiling on 4 of them.

One thing thats not even taken into consideration on the charts of the strength of these anchors is that when you have multiple anchors thru a plate they all will not be drill perfectly straight so they end up being in the concrete at different angles. which makes them extremely difficult to pull out.

 

[mk3cn4]

mk3 I have to disagree with your statement about the top plate connecting the two post being just a elegant way to hide the cables........on the two bendpak lifts I've had and installed that plate is quite stout and more than adequate to hold those columns apart even if there were no anchors in the floor.

ok, I was going by that page I linked showing all the forces in play. When I spec'd mine I eliminated the top crossbar ones because it burned 6" from the lift height, and my baseplate one still goes low enough for any car. My arms fit under a 68 vette fine.

when I lift my grand cherokee to the ceiling the front bumper is 6'7" off the ground! being over 6' tall that 6" means a lot.

I like the reinforcing plate idea but I would not do it personally because the minimum pad height was important to me, lots of sports cars.

I'd still qualify this by saying to people to make sure your crossbar lift is one that has load bearing crossbar. That linked site with the engineering math sure sounded like they knew what they were talking about.

 

[cj7jeep81]

I'd make sure to check with the manufacturer before you put a plate under it. I'm sure they have a lot of really smart people engineer these things, and you wouldn't want to void a warranty or something by not following their directions (not saying it would, but I'd check first).

With as sue happy as people are now-adays, I'm sure the minimum specs for concrete thickness, base plate size, etc is already way overkill. They aren't going to spec minimum requirements that are even remotely likely to fail.

 

[wssix99]

I respectively disagree, the 2-post lift acts as a lever against the outer bolts at a multiple of the vehicle weight, likely several times the vehicle weight. Especially true if it's a baseplate lift. I would expect an UPWARD pressure on outermost bolts to share each more than 10,000 lbs. in heavy lifting.

Think of the lift post like a crowbar levering against the outermost anchor bolts, lever has several feet on one side and mere inches on the other. Lots of leverage lots of force. You're still probably OK but this thread seems to discount the amount of force on this lift, don't underestimate the risk.

Most people when thinking about the dynamics of a lift are worried that concentrating the load of the car on two posts will create a punch-through force on the slab. The common misconception is that the thickness of the slab is required to counteract this bearing and punch-through force.

Most people don't consider that the base plates on a lift are typically larger than the cumulative contact patch area of a car's tires and the vertical force on the slab is along the lines of a car just sitting on the slab without a lift involved.

The slab thickness is most important for bending. The pull-out force of the bolts is also insignificant. You can calculate that by taking the pull-out force and dividing it by the surface area of the bolt hole that is in contact with the anchor. So, if you had a 5/8" bolt hole with 3" of depth contact seeing one ton of pull-out force, the concrete would only experience 340 psi of stress.

BTW - A bolt on a lift would never see 10,000 lbs of pull-out force unless the user was not following instructions or proper lifting technique. (At that point, the welds on the lift would probably crack anyway.) Even if a 5/8" X 3" bolt hole were to see that much force, we still wouldn't be any where near the capacity of cheap concrete. (When calculating forces on this stuff, its also important to remember that the total load is divided evenly between the two posts, so each post only see's 1/2 of the weight being lifted.)


Back to the OP and plates - Plates might help by taking on bending stresses that the concrete would otherwise need to counteract by itself. (Punch-through is not a consideration because it isn't an issue.) However; adding plates or other components beyond what the manufacturer specifies or recommends can have unintended consequences. Adding 1/2" to the depth of the base can increase moment arms, etc. beyond limits or in ways that the engineers didn't intend.

Contacting the manufacturer for guidance is probably the best thing to do.

 

[camnick]

I went back to the guy selling the lift and it's only a 10,000 lb lift. I got the model number and contacted the Manufacturer. They emailed me a manual. Turns out the manual says I only need 4 1/4" of concrete. So as long as my contractor didn't short me, I may OK. I need to pick out the location in the barn and drill a test hole.

 

[samert111]

I've just gone thru the same scenerio on my lift which is a Forward 9000 lb model. What happend to me is when I drilled my test hole, unknowingly the drill popped out the concrete as it broke thru and when we measured the thickness with a pc of wire with a bend on the end it couldn't reach out past the borken out area and measured just over 3" but is was actually closer to
4" but still a litle thin. I ended up cutting out a 6 1/2 ft x 14ft pad and
re-poured it with 8" of steel bar reinforced 4000 lb concrete dowled and into the surrounding concrete.

 

[UPSHIFT]

I am purchasing a used Forward 12000lb 2 post lift. The current owner has it mounted on 4" of concrete. It would scare the hell out of me to mount the
lift in my barn on just 4" 4000psi concrete. The current owner said he used to install lifts. He said I could get a 1/2"-3/4" steel plate to put under the each post leg. The plate would be much larger than the posts and the edges of the plates would be anchored to the concrete also. Has anyone ever done or seen this performed?

camnick,

Any 2 post 12000lb lift will require 6" of concrete and 7" Anchor Bolts as that is standard with a reputable lift like Forward, remember these lifts are designed with the possible static load in mind ( 36000LB ) as there is 3" usually between the locks and if 12000lbs fell 3" and hit the locks our engineer buddies will agree there is a possibility of 36000lbs of force transferring to the anchor bolts.. I feel it is better to pour concrete vs. the calculation of steel plates as that may give you a sense of false hope. If the lift is a floor plate model ( No overhead support bar) these ideas are even more critical as there will be more force on the anchors.)

If the lift is getting installed in a home garage it is rare you would have a 12000lb truck to load on it ? If you can guarantee nothing over 9000lbs will be put on the lift the 4" concrete will be OK. You can change the relief valve setting on the motor to limit the amount of weight it will lift and or get a weight gauge from Mohawk Lifts to let you know what you are lifting. If you question any of the items I suggested you need to pour 2 4'X4'x19" deep pads. (1 under each column.) Good Luck..

Gabe
Dannmar

 

[UPSHIFT]

I went back to the guy selling the lift and it's only a 10,000 lb lift. I got the model number and contacted the Manufacturer. They emailed me a manual. Turns out the manual says I only need 4 1/4" of concrete. So as long as my contractor didn't short me, I may OK. I need to pick out the location in the barn and drill a test hole.

camnick,

Your Golden, just be sure you install the bolts correctly. Also do not push on the drill especially near the end of the hole. Good Luck..

Gabe
Dannmar

 

[UPSHIFT]

Most people when thinking about the dynamics of a lift are worried that concentrating the load of the car on two posts will create a punch-through force on the slab. The common misconception is that the thickness of the slab is required to counteract this bearing and punch-through force.

Most people don't consider that the base plates on a lift are typically larger than the cumulative contact patch area of a car's tires and the vertical force on the slab is along the lines of a car just sitting on the slab without a lift involved.

The slab thickness is most important for bending. The pull-out force of the bolts is also insignificant. You can calculate that by taking the pull-out force and dividing it by the surface area of the bolt hole that is in contact with the anchor. So, if you had a 5/8" bolt hole with 3" of depth contact seeing one ton of pull-out force, the concrete would only experience 340 psi of stress.

BTW - A bolt on a lift would never see 10,000 lbs of pull-out force unless the user was not following instructions or proper lifting technique. (At that point, the welds on the lift would probably crack anyway.) Even if a 5/8" X 3" bolt hole were to see that much force, we still wouldn't be any where near the capacity of cheap concrete. (When calculating forces on this stuff, its also important to remember that the total load is divided evenly between the two posts, so each post only see's 1/2 of the weight being lifted.)


Back to the OP and plates - Plates might help by taking on bending stresses that the concrete would otherwise need to counteract by itself. (Punch-through is not a consideration because it isn't an issue.) However; adding plates or other components beyond what the manufacturer specifies or recommends can have unintended consequences. Adding 1/2" to the depth of the base can increase moment arms, etc. beyond limits or in ways that the engineers didn't intend.

Contacting the manufacturer for guidance is probably the best thing to do.

All my engineering data on our 10K 2 post show 2816lbs of force on each bolt with the arms extended all the way out under max load. This will vary based on size of base plate and length of arm. The anchors used are Wej-it 3/4"X5" wedge and have a pull out strength of roughly 13330lbs when installed in 4000psi concrete. Anyone who wants to see this data let me know as I can provide it.

Gabe
Dannmar

 

[carpenter383]

My concrete is 4" with wire mesh. I just bought a slightly used 10000 lb forward lift about 1200 less than a new one. When I went to look at it the first time we put a jeep grand cherokee on it and I pushed up and down on the bumper and watched the columns flex! This is only aprox 1/2 capacity! That made me nervous so I looked at a few other lifts and they were the same way. I ended up decideing to get the forward lift with a plan. I am gonna bolt brackets in the 4 corners of my garage at the ceiling and use cables to connect the posts to the corners of the wall. The cables will angle back to the posts which will counteract the post flexing and hopefully make the posts alot more secure. This could be just me being paranoid, but I figure it's better to be safe than sorry. Btw my walls are 2x6x12 with 7/16 osb on both sides, as a carpenter I have a pretty good idea of how strong wood framing is and I'm very confident it wont even come close to moving the walls especially since the cables will be angling off the corners..... Just and idea I thought Id throw out, I can post pics after I get it done

 

[maxspeed96ct]

What you said about adding a plate makes sence, a nice 2'x2' piece of 3/ solid steel or something.

Another idea would be to weld some additional steel to the lift base and maybe add another anchor or two.

But like guys have said. These anchors have some very high ratings If you look them up. a 3/4 drop-in alone could hold thousands in just 2500psi crete



But most important buy a quality lift, because that makes a differance aswell.

 

[galute]

I think you guys are underestimating the strength of concrete. That stuff is tough. I have busted up many slabs. Let me tell you, it aint easy. Especially a slab that has a lot of age on it. I've seen a 4" slab stall out a track hoe with 40000 pounds of break out force lots of times.

 

[VolvoMan]

Reading this thread with interest, couple of things haven't been mentioned in regard to the forces acting on the base plates.

Firstly, even if you have a manual that tells you where to put the vehicle, the balance point will change dramatically if you're doing something major like pulling the motor (especially if it's a cast iron Big Block) or the rear axle. As my Dually weighs in at 6000lbs empty, taking out the motor at around 600lbs still leaves 5400 in the air, which has a COG moved backwards by quite a lot, or the equivalent of 3 big guys standing in the pick up bed. Just going on a simple calculation, that's a change of at least 3,600 foot pounds of force moving from front to rear, at 6' in the air.

Also what hasn't come up, is the rocking moment incurred when working on the vehicle. If what you're doing requires wailing on something with a hammer, prying at something with a bar or torquing up a big nut along the longitudinal axis of the vehicle, you're going to be constantly shifting the COG of the vehicle back and forth against the anchors. As anyone who's ever taken a tough screw out of masonry will know, this rocking motion steadily works away at loosening the hole. Any small offset in the COG of the lift will only magnify this force. Added to this, the height of the vehicle, which is likely to be 6' magnifies the forces being transferred so that a force to 400 foot pounds on the vehicle is transferred to the base as 2400 foot pounds on the Anchor.

I remember a few years ago, all the 2 post lifts I saw had a large H shaped base frame, with legs out from the posts at least as long as the lifting arms. You could actually use these lifts safely without bolting them to the floor as all the forces were counteracted by the arms. they weren't great for low Super cars, but any car that could survive a speed hump without scraping was fine. usually, these were installed into an H shaped cut out in the floor to bring them flush for low vehicles. Are these still available? in the UK, the main manufacturer of these was Laycock I think.