Lifting Bars - What Gauge/Thickness?

[CB700SC]

Hi, all - been lurking for a bit as I'm helping an older friend of mine with a tractor project and been getting info we need. However, I'm trying to figure out how best to accomplish something and would like materials advice.
Recently, I came into possession of a mid-rise lift. Specifically this one:

While it has the weight capacity for the vehicles I want to lift with it, the lifting surfaces are too short for a couple vehicles to be lifted safely. Specifically, the lift deck is 53 inches long, while the car has jacking hardpoints that are 77 inches apart and there are no other closer points at which it can be lifted or supported without damaging it. These hard points have hard pads with locating pins that stick down below the rest of the vehicle; the pins are such that they will fit in a 1" hole. The car weighs about 4500 pounds.

What I want to do is make a pair of bars from square tube to place under the car longitudinally, such that the car can be safely lifted by the hoist's lifting surfaces. Something similar to these, which are made by liftbars.com for Porsches (they won't make custom stuff):

I propose to make them out of 2"x2" or 2"x3" (longer side parallel to the lifting surface) square steel tubing, but I'm uncertain what wall thickness to use to safely support the weight of the car without coming into contact outside of the four hardpoints. I have had some people tell me 1/4" wall tube is best, but I have had some people tell me 1/8" wall tube will work just fine in this application. Any opinions would be appreciated.

 

[newbury]

Have you looked at just modifying a couple of pallet rack beams?

 

[CB700SC]

No, but I don't have easy access to those. I do have access to some 2x2 1/8" wall fence posts (8' long) and I can get ahold of other 2x2 square tubes in various wall thickness.

 

[Rustyiron]

1/8" wall is not enough. Do you plan on using these lifting bars with that lift you pictured?
Balancing 77" on top of a 53" support distance does not sound very safe. I'd be looking for 5/16-3/8 wall and if you can scrounge up some 2x3 tube, orient the 3" dimension in a vertical direction.

 

[GreyhawkUSA30340]

With those porsche lifting bars, they are lifting one side of the vehicle with a single jack in the center, and you can see the bar flex (note that with no load, the bars appear to be designed with a dip in them to accommodate that flexure).

In your case, using your 53" lift under the 77" bars, presumably you would be lifting the whole vehicle at once, with 12" of overhang off each end between your lift and the lifting points on the vehicle (here assuming the vehicle's balance point is centered between those lifting points).

At 4500 pounds, that means each or your extension bars is cantilevering about 1125 pounds that 12" out from your lift. I think you will want a thicker wall tube than 1/8"....

 

[CB700SC]

Another item I forgot to mention - when the vehicle is sitting on top of the fully-collapsed lift, there's only enough space to fit a 4x4 between the lift top and the car's jack points and even that is barely possible. I had also had the idea of possibly being able to also able to use the bars without the lift, just as the Porsche-intended product is.

I'm somewhat sure that the balance point is more forward biased, to the point where I was half-suspecting the safest way to use the bars would be to put the end under the front jack points onto the lifting surface so that the overhang would only be off one end.

A quick check of one local welding steel provider shows that the thickest 2x2 they offer is 5/16, 2.5x2.5 goes up to 3/8. Would either of these work?

 

[WranglerX]

Never really liked the idea of a mid point lift.... To easy to screw up ballance and to easy to crush under working of vehicle ... and if you have to start making adapters to make it work it jest even squirrlier... Guess that is why I use old skool floor jack and jack stands....

 

[CB700SC]

To be fair, mostly this would be used for tire rotations and brake work with safety stands under it. The occasional oil change as well - but again, safety stands. It also works fine for most of my other vehicles in terms of size. My available work space is pretty constrained so a conventional jack has to be worked at an angle to the wall so this actually frees up space. I was actually hoping to get some QuickJacks cheap (which have the same problem with a lot of cars when trying to lift longitudinally, but they offer lift extension tray things - not quite long enough to be used here, alas - or they can be rotated to lift the vehicle transversely) but someone literally gave me this thing so the price was right.

 

[4570Man]

Have you looked at just modifying a couple of pallet rack beams?

Those beams are pretty light duty. Most of them aren’t even 1/8” wall. I’d trust some 1/4” wall tubing a lot more than those.

 

[CB700SC]

These are the QuickJack 'frame extensions' - they're 66" long, intended to be used on the 7000lb hoist version, so they're not long enough for my application.

Frame Extensions

QuickJack’s TL frame extension kit increases the lift point spread of the 5000TL, 7000TL, BL-5000SLX and BL-7000SLX by 6 inches. Sold as a pair, these easy-to-use, removable adapters require no setup whatsoever. They’re rugged, lightweight and give a TL or older SLX model the same reach as an...

quickjack.com