MaxJax - unusual problem with dedicated foundation

[Daedalus]

and what's all this talk about using "glue". Come on now you're going to be under a car beating and shaking an 8000# hunk of death above you. Cut the bad stuff out with a concrete saw and drill rebar into the sides of the slab and dig a hole 3 feet down and repour with some real concrete. Any less and you won't catch me under it. No such thing as overkill when it will be over my head.

Do you re-engineer airplanes and elevators before getting in them too?

 

[skulldrinker]

Do you re-engineer airplanes and elevators before getting in them too?

Just being paranoid and if the elevator was installed by a non union company or the landlord I would take the stairs.

 

[mercury26]

When I got my MaxJax lift, I fully expected to have my garage floor match what is listed on the plans: 3000psi mix with a minimum of 4" slab. My house is just over 20 years old and at the time I bought, I had never considered a lift.

What I found when I drilled the first hole was that the floor thickness at that point was just under 2.5" Drilled another hole and found a 3" thick area. I knew at that point the existing floor was not going to work with the supplied Wej-It anchors.

So I got a local concrete company to come in and they cut out two 4'x4' sections of the floor. Sure enough, the pieces that came out were anywhere from 2" thick to 4" thick. They dug down 12" and poured a 6-sack mix and leveled the surface. They also used rebar to connect the old floor to the new pour. The new sections were located so that each post of the lift was centered on the new concrete.

Because the new sections were 12" deep, I decided to go with the Wej-It Epoxy anchors. I let the new concrete cure for something like 60 days. Drilling the holes was easy and I made sure the holes were vertical and very clean. My lift is now up and working and the bolts are torqued to 80 ft-lbs.

Both types of the Wej-It anchors (the wedge style included or the epoxy equivalent) require a 7/8" hole to be drilled. I would think that Dannmar has done their research and engineering to come up with a anchor size that far exceeds the strength requirements for their 6000 lb. load capacity of the MaxJax so going to a smaller diameter anchor doesn't sound like a good idea.

I had to buy a hammer-drill bit from Amazon as HD and Lowe's do not carry that size. Paid about $30 for it but worth the money.

I had the exact some problem with concrete poured about two years ago for my new garage. Also, I did the exact same thing for the solution, new 4'x4"x12" footings with epoxy anchors from Wej-It. Everything torqued up great and is working as expected. I much prefer the epoxy over mechanical anchors. I cleaned the holes very well also, lots of compressed air, wire hole brush attached to drill, more compressed air, vacuum, more wire brush, more compressed air, more vacuum. Essentially till there was no more dust.

 

[bcradio]

Never heard... did you get this solved?

 

[PatL]

I did finish the job and have lifted several heavy vehicles recently. I ended up rigging up a hydraulic puller to remove the anchor bolts from the concrete. 12 of the 13 anchor bolts tensiled at the right angle bend and 1 of them actually nearly broke my hydraulic set up because it did not tensile, it straightened out the bolt by pulling it around the 90 deg bend. Amazing.

I then purchased the PowerSerts from Wej-it (purchased from Gabe at GES) a, filled the bottom of the holes with quickcrete, drilled the holes to 7/8" for the recommended 6" depth and epoxied them in. Worked great and now I have my flush female threads 1/16 below the surface of the concrete so when the lift is not installed, I install my custome made SS washers welded to a SS 5/8" -11 short piece of all thread to keep water and dirt out of the holes.

 

[BITRBO]

c4cruiser,

Quick question to see if your situation ios similar to my planned set up.

Do you know of the tops of the epoxied anchors are contacting the bottom of the base plate or if there is a gap? The reason I ask is if they are not contacting the plate, then the 80 ft lbs of torque is putting shear stress on the epoxy joint and the additional load when a car is liffted will add to the axial load on the system and therefore adds to the shear load on the epoxy/concrete interface. On the other hand, if the insert is contacting the base plate during torquing, then the 80 ft lbs is not loading the epoxy/concrete in shear until a car is lifted and the total shear in use will be much less.

^This was my initial concern too (although more for mechanical anchors), and I'm surprised that it wasn't discussed much further...

I purchased a Triumph 2-post instead of a MaxJax, which also recommends tightening the bolts to 3 to 3-3/4 turns past snug (they copied the MaxJax manual, after all), which I think is may too much and basically impossible using the anchors I have (without them pulling out). Furthermore, anyone that has tightened their bolts to 80ft-lbs is going overboard IMO, and is actually reducing the capacity of their lift! I certainly think you can TEST the anchors to that amount (or more if you wish), but by torquing them down by that much for final installation (80ft-lbs is roughly 6,400lb tensile for a 3/4" bolt!) you are preloading the anchor before the lift is even operated, and effectively reducing the ultimate pull-out capacity. My lift was supplied with Powers SmartDI+ anchors, which actually state the maximum tightening torque is 80ft-lbs:

http://www.powers.com/pdfs/mechanical/6312SD.pdf

...However, that doesn't mean the bolts should be tightened to this spec, rather they should not be tightened MORE than that amount. I think folks are confusing the the two.

I think that a 1/2 - 3/4 turn (or even 1-full turn) past 'snug' as suggested (maybe 20-25ft-lbs?) would ensure the column is properly secured, yet not overly tight to where it would basically reduce the loading capacity of the anchors themselves.

p.s. sorry to bump an old thread but I though this was worth mentioning

 

[Cobra96]

^This was my initial concern too (although more for mechanical anchors), and I'm surprised that it wasn't discussed much further...

I purchased a Triumph 2-post instead of a MaxJax, which also recommends tightening the bolts to 3 to 3-3/4 turns past snug (they copied the MaxJax manual, after all), which I think is may too much and basically impossible using the anchors I have (without them pulling out). Furthermore, anyone that has tightened their bolts to 80ft-lbs is going overboard IMO, and is actually reducing the capacity of their lift! I certainly think you can TEST the anchors to that amount (or more if you wish), but by torquing them down by that much for final installation (80ft-lbs is roughly 6,400lb tensile for a 3/4" bolt!) you are preloading the anchor before the lift is even operated, and effectively reducing the ultimate pull-out capacity. My lift was supplied with Powers SmartDI+ anchors, which actually state the maximum tightening torque is 80ft-lbs:



http://www.powers.com/pdfs/mechanical/6312SD.pdf

...However, that doesn't mean the bolts should be tightened to this spec, rather they should not be tightened MORE than that amount. I think folks are confusing the the two.

I think that a 1/2 - 3/4 turn (or even 1-full turn) past 'snug' as suggested (maybe 20-25ft-lbs?) would ensure the column is properly secured, yet not overly tight to where it would basically reduce the loading capacity of the anchors themselves.

p.s. sorry to bump an old thread but I though this was worth mentioning

Great Reply...., makes a lot of sense. I think some of us got caught up with making sure the PD58's were set. I continued to torque he columns at 75.
My first install was outside. Had new footers poured in he garage so I will be using the epoxy anchors for the majority of my anchors.

 

[Milton Shaw]

I am going to ask whether or not the original concrete when you poured the pad was vibrated to get the air bubbles out. I have seen a lot of concrete that did not flow around bolts/rebar etc. unless it has been vibrated during pouring. I bought a HF concrete ******** to use on block filling and it required adding additional concrete everywhere that I used it.

 

[Cobra96]

My pads are 4'x4' 12" deep 4000psi. The contractor I used aerated it without the ********. For this lift, I'm already at overkill. The bolts (holes and anchors) haven't been installed yet still allowing concrete to cure. My original garage floor was 6" deep (sufficient depth) but when I went to set the pd58's the concrete cracked from top to bottom connecting the three back drop ins. As per Danmars instructions, they call for 3'x3' x 12" deep.