MaxJax New Slab Pads - How Big?

[RecceDG]

So my wife got me a MaxJax.

Today the rotary hammer showed up, and I went forth and started drilling anchor holes - only to find that the slab is maybe 3" thick.

I tried setting an anchor anyway, and no joy - it hasn't pulled tight by the time it is flush to the floor.

So I guess I'm going to join the "cut out holes and pour new pads" club.

Questions:

1. What's the recommended size for the new pads?

2. Is there any advantage to pouring a single pad that spans both posts?

I'm going to have to start calling contractors and speccing the job - any advice all y'all can provide will be very helpful.

DG

 

[Jvvmusme]

1. Keep your wife
2 . The bigger the better
3. The last ones I made (I moved) are 40 x 40 x 40 cms.
4. I soldered the anchors between them with steel rods and with a flat surface pushed them into the fresh concrete. There is a very good thread about this from a guy that has a yellow Porsche....I cant remember his name. Great thread. He did a single pad spanning both post.
5. I did a pad with 11 anchors for multiple widths. From an MG TC, a classic Mini to a Jaguar E Type. I ll post a picture this afternoon.

 

[Jvvmusme]

http://www.garagejournal.com/forum/showthread.php?t=181935

Great thread from the guy with the yellow Porsche

 

[Jvvmusme]

If you look carefully at the left post you will see in the concrete pad some black dots. They are the extra anchors for different widths.

 

[Jvvmusme]

Here I have 3 different widths.

 

[RecceDG]

14-15" deep seems like overkill...

I'll buy the idea of spanning the posts with a single slab, so the rebar can tie the whole thing together. And I get that wider offers a better base to resist tippping. So a 4' x 12' plan form dimension makes sense.

But I'd think that 8" should be more than thick enough - that's double the spec that Danmar wants for the slab.

Why so thick?

 

[Jvvmusme]

9" thick . Conversions made me make a mistake. 22 cms thick.

 

[Vegaman_Dan]

If I were to do this again, I'd cut out a channel between the new pads for a passageway for the hoses between towers. It would also let you tie the two posts together below for an even stronger connection than independent pads.

Extra mounting points outside in your driveway would be an excellent addition. My garage roof is too low to get a full lift even with the MaxJax, so I hope to cut and add new mountings outside for temporary use.

 

[RecceDG]

So I did it.

Getting any contractor to return my calls was a serious PITA. Only two did; one quoted me $1400 or so, where the other (very professional, did up a full quote) quoted $3400.

But my neighbour knew a guy - he did the floors in his shop. He's 84 years old and had been pouring concrete for most of those years. He offered to coach me, arrange for the concrete delivery, and do the final finishing - for $120.

So I cut out a channel 4' x 12' and dug it down to 9.5" deep (+/- 0.5"). 1/2" rebar was pounded 8" under the existing slab on both x and y. The pour took a little over a cubic metre of concrete and was finished with a power trowel.

I'm just waiting for the pad to fully cure, and I'll start drilling in anchors.

Some tips:

- The concrete saw will throw more dust than you can possibly imagine. I had the garaged partitioned using plastic sheet, and it did absolutely nothing. Everything in the garage was covered with a fine layer of dust that I'm *still* cleaning up. I should have completely emptied the garage before cutting anything.

- The diamond wheel is the way to go - the abrasive cutoff wheels are junk.

- I started breaking the slab with a 10lb sledge and a pry bar. That worked fine, but it is slow going. When I switched to a medium jackhammer to assist breaking the slab, it went *way* quicker.

Pics later.

DG

 

[saceone]

you mean you did NOT use water with the diamond wheel? no wonder it made a mess!!!!!

 

[RecceDG]

I used water; it did very little to mitigate the dust.

 

[70runner]

I poured 4x4 pads, 15" deep, 4K psi mix, with rebar cage for 7K lift. Keyed under existing slab (3.5"). Waited a month to drill the holes for epoxy anchors. Diamond wheel only way to go. Yea, the dust...ugh. Fortunately my garage was empty since I was doing an epoxy floor.

 

[RecceDG]

It's in!

All the fittings are holding tight, save one - the "long L" at the lowering valve (bottom of the short hose) is leaking, and isn't responding to attempts to solve it. It's a weird fitting too; no flare, and it isn't NPT. Is there supposed to be an O ring in there?

Is there a torque spec for the floor bolts?

I used the Wedj-Its and had no problems.

 

[RecceDG]

And here's the results:

http://imgur.com/a/Mf6Na

 

[Jvvmusme]

Great pictures
Nice results

 

[c4cruiser]

I had the same problem with my garage floor. The original garage specs called for a minimum of 4" thick with 3000psi mix. When I started to drill anchor holes, I found spots that were just over 2-1/2" thick.

I had a local company cut out two 4'x4' openings and poured 12" thick pads in the two openings using 5000psi mix. Rebar was used in the pads and tied in to the existing floor.

I used 7" epoxy anchors rather than the wedge-style anchors that were provided with my MaxJax.

 

[RecceDG]

The "long L" fitting is indeed supposed to have an O-ring. Mine did not. What I thought was a crush washer deformed into the o-ring groove and trashed the fitting - although happily, not the valve body.

A new fitting from Parker solved the problem. I'm now leak free.

I was seeing a little asymmetry in the lift pads, but further bleeding and greasing the slider blocks seems to have fixed that.

What I'm seeing now are lift securing bolts not staying torqued. I've set them to 80 ft-lbs, but 2 or 3 per side will relax once the car goes up. Not much - maybe a wrench flat to retorque. But I can't help wonder what is going on there.

 

[Jvvmusme]

The "long L" fitting is indeed supposed to have an O-ring. Mine did not. What I thought was a crush washer deformed into the o-ring groove and trashed the fitting - although happily, not the valve body.

A new fitting from Parker solved the problem. I'm now leak free.

I was seeing a little asymmetry in the lift pads, but further bleeding and greasing the slider blocks seems to have fixed that.

What I'm seeing now are lift securing bolts not staying torqued. I've set them to 80 ft-lbs, but 2 or 3 per side will relax once the car goes up. Not much - maybe a wrench flat to retorque. But I can't help wonder what is going on there.

1. Always the same bolts relax ?
2. Use epoxy in all anchors
3. Play safe