MaxJax idea - Additional baseplate to help spread load?

[Viper98912]

I'm preparing to buy a small lift so I can do maintenance work on my vehicles. Heaviest car is 4,500 lbs. Work area would be a standard 2-car garage space with the lift in the middle (already put up a jackshaft opener for more overhead clearance).

Still debating whether a 2 post (MaxJax) or a 4 post with casters and center jacks. I prefer the 4 poster due to stability and spread of the load, but size is a little bit prohibitive (to roll it into the "work" area of the garage), as well as the ramps would be fairly difficult for one of my vehicles (2" of clearance on the front bumper).

I asked the builder of my home for the specs on the garage concrete and I got the following response:

3.5 to 4" thick
3,000 psi with wire mesh

Looks like a standard "code" answer to me. They're building a house with my same floorplan down the street and in poking around I measured 6-8" in the garage area in the unfinished house. But regardless, I don't exactly trust it without seeing it myself, and I don't exactly want to start drilling random holes into my garage searching for dirt.

I was wondering if anyone has bolted any additional baseplates to their concrete where the MaxJax posts would sit? I figure some 1/2" steel plate (maybe 2' x 2'? Slightly bigger?) to help spread the load in the area where each post would sit. This would sit permanently on the floor, and just drive over it when parking both cars in the garage.

Thoughts?

 

[c4cruiser]

I think the thing to watch when the concrete is poured is that you do get a 4" slab. When I bought my house, I got a copy of the plans that spec'd a 4" pour. When I started to drill the anchor holes for my MaxJax, the floor thickness in the area was not much over 2-1/2"

I wound up having a concrete guy come in and cut out two 4'x4' pieces of the floor and then dug down 12". We added rebar into the new pads and made sure they were clear of where the anchors would go. The new pads were also tied into the existing floor.

The company used a 5000 psi mix and I specified that the pads be finished to match the existing floor and that the pour be level and not match the existing grade.

I used 7" epoxy anchors instead of the 4" WejIt anchors that came with the MaxJax.

There are a couple of threads describing MaxJax installs with some excellent pics of how installs were done. Do a search on "MaxJax" and they will come up in the results.

 

[tcianci]

One thing that you haven't mentioned is the pull out forces exerted on the anchors. The MaxJax is a 2 post lift, therefore there is a very substantial uplift force on the column bases due to the cantilevered load on the column. So what you need is a floor that meets the manufacturers specifications or a truly engineered solution. Your concern for load bearing is only part of the situation you're dealing with. If indeed you don't have sufficient concrete, you may well need to pour new pads or get a 4 poster.

As mentioned, there are numerous install threads on GJ but, you really need to be working with the manufacturer as well, it's their product, and they specify what type of installation is acceptable.

 

[wssix99]

I was wondering if anyone has bolted any additional baseplates to their concrete where the MaxJax posts would sit?

This is really unnecessary and I am sure the manufacturer will tell you that it is definitely not a safe thing to do.

You should not be concerned about the "load" of a lift on your floor. The vertical load is insignificant. -> The math is easy to do:

Pressure of a car parked on a pad = <Weight of Car> / (4 Tires * Tire Contact Patch Area)

Pressure of a car on a 2 post lift = <Weight of Car and Lift> / (2 Posts * Base Plate Area)

If you do the math, you'll see it's a really small force. As noted above, your biggest concern is the tipping/pull-out force on the anchors.


IMO - The best thing you can do is show up on the day your pad is getting poured, give the concrete supervisor a $100 and a case of beer, tell him that you need a full 4-5" of concrete in the areas where your posts will go. Then sit there and watch them and make sure it happens.

 

[wssix99]

one of my vehicles (2" of clearance on the front bumper).

... That's really tight for any lift. For the Max Jax, I assume you won't be able to escape having the vehicle stick out of the door to get it centered on the lift?

For something this tight, have you looked at a scissor jack setup?

 

[honEXduner]

I think the thing to watch when the concrete is poured is that you do get a 4" slab. When I bought my house, I got a copy of the plans that spec'd a 4" pour. When I started to drill the anchor holes for my MaxJax, the floor thickness in the area was not much over 2-1/2"

IMO - The best thing you can do is show up on the day your pad is getting poured, give the concrete supervisor a $100 and a case of beer, tell him that you need a full 4-5" of concrete in the areas where your posts will go. Then sit there and watch them and make sure it happens.

Unfortunately it sounds like his garage is already poured and looking at new construction down the street for clues about his existing slab.

As mentioned previously, the tension loads on the outer anchors are the big thing to worry about with a two post setup. First worry would be the anchors pulling or concrete failing due to lack of thickness surrounding the posts.

Probably time to figure out exactly what you have vs manufacturer's specs or re-pour specific locations with reinforcement for the posts to rest on.

 

[Viper98912]

Yes, my house is already complete and been so for about 8 months. I wasn't here when the pour happened, if so I would've done things specific....this includes many things in the garage, which I've been working on upgrading for months now.

Front bumper center is pretty low, but I've got about 3" on the side of the bumper, and underneath the car I've got a little more room. Most scissorjack specs I've seen give me a problem with the front bumper clearance (rolling over the jack to get into position). A recessed pit-style would be nice, of course.

Also, I'm looking for an "open" bottom so I can do things like a rear main seal and pan drops. A 4 poster would work alright, I'd just end up getting the additional center jacks. But I do have a problem of "moving" the 4 poster around the garage to get it into working position.

But then again, having space for another vehicle would be nice...

The thing I'll probably end up doing is just start drilling holes in the concrete where I plan on placing the posts for the MaxJax. If I hit dirt before 4", then I know I've got a problem. From there I'll figure out whether I cut out the slab and redo the concrete, or I do some other type of custom solution.

Figures, I've just finished doing the epoxy coating about 3 hours ago.

 

[boobag]

i'm not sure if you're a diy'er, but to install a couple thick pads is not that big of a deal.
just saw cut out a couple squares. bust out old concrete, set rebar, then repour.

 

[Viper98912]

Definitely a diy guy, just never done it before