Home made jacking tray

[steam_mill]

So, I have a direct lift 4 post. I took 2 2x12's, laminated them together with screws and construction adhesive.

I'm going to use this as a area to put my car on jacks.

I tried it, worked well. Is this dangerous. Car is a 3300 lbs. mustang

 

[ghnl]

Wood is fairly strong in compression. (think a vertical 2X4 stud bearing the weight of the roof.) But it is not strong in tension. (imagine putting an eye bolt in the ends of a 2X4 and trying to restrain a pick up truck pulling on it.)

I don't think your wood jacking bridge is in compression with the weight of the car on it. I'd worry it is not the right engineering.

 

[e-tek]

How much are you going to overlap the ramps and how far apart will the jacks and/or stands be? that is the question!

 

[DGC15]

I made mine from some 8" steel channel. Welded a 4x4x3/8 angle on each end to set on the lift runners. Works great. Real easy to slide back & forth.

 

[DARK AGE 53]

Is this dangerous.

In my opinion you answered your own question.

 

[ket-tek]

Uh, you shelled out for a lift, but won't buy a $99 jack tray?

Wood is strong, but should be on edge not flat for maximum strength and minimal deflection.

I can't say if it is safe or not, but I would never stand under it that's for sure.

 

[holdover]

make it out of steel or buy one made for the job, too much is resting (no pun implied) on it.

 

[stingry]

Wood is fairly strong in compression. (think a vertical 2X4 stud bearing the weight of the roof.) But it is not strong in tension. (imagine putting an eye bolt in the ends of a 2X4 and trying to restrain a pick up truck pulling on it.)I don't think your wood jacking bridge is in compression with the weight of the car on it. I'd worry it is not the right engineering.

Actually this is not true, wood is stronger in tension (parallel to the grain) than compression. Doug Fir is approx. 11,000 psi tension parallel to the grain and is approx 7400 psi compression, also parallel to the grain. I got the values from here:

http://www.worldwideflood.com/ark/design_calculations/wood_strength.htm

As to the original post, personally I'd feel more comfortable with steel.


Cheers
Steve

 

[On1Wheel]

I'd be scared of it but on edge, I'd think you'd get ample warning before it gave way. The only thing that would worry me is with it on edge, it wouldn't be as stable since it is fairly top-heavy.

I think I'd add 4 more 2x12s so that it's 12x12. That's going to be a huge beam, and definitely overkill and possibly impractical, but much safer IMO.

 

[dirttracker18]

I have no engineering to back it up but I would not do it. I also disagree that you wold have warning. I think if it fail it would be dramatic and fast. Byt he time you heard the crack it would be dropping.

Spend the money for the $99 jack tray. Your life is worth at least that much right?

 

[Falcon67]

I would at least frame the lower edges longways with 2x2 angle iron. 2x12 on edge is damn stout. 2x12 on the side I can break into dual 2x6s with my foot. I've had 2x12x12 wood pads snap in half under a jack stand while the back side was supported by the floor.

 

[Daniel Dudley]

If you show us a picture, we would be much more capable of giving you an informed opinion.

 

[Zeke]

If he used plank grade (no knots and good grain) I would think OK if the stands weren't out in the middle. The ultimate strength would depend on how the 2 boards were oriented. I believe epoxy would have been better as an adhesive.

But my question is if these are laying on the ramps, aren't they just about touching the bottom of the car? If this car is going to be suspended up above the ramp height on boards it's gonna rock around like Elvis.

I need pics.

 

[dirttracker18]

i think so are misunderstanding here.

If he wants to put stands on them he must be using them flat and not standing on there edge.

If you used them upright, yes no problem but you cannot put stands on them like that.

If you are using them flat and putting stands on them, you couldn't pay me to get under there.

 

[ghnl]

Actually this is not true, wood is stronger in tension (parallel to the grain) than compression.

Sorry, my descriptions were not the best. A wood beam with a load sitting on it has wood both in tension & compression. IIRC, if overloaded the beam will usually fail in the area under tension.

A 2X12 laying flat (like a shelf supported only on its ends) has a very small amount of material in either compression or tension. I don't know if doubling it (even with glue/screws/etc) will double the load capacity or not.

Angle iron along the sides should add some much needed stength.

 

[haugy]

I'm having the hardest time even figuring out what you are trying to do.

 

[mad57]

You can build one from steel way cheaper than $100 the wood might hold for a bit but id use only steel.

 

[ibedayank]

Todays Headlines read...... Man was crushed by car that fell off a lift because he was to cheap to use the lift safely. News at 11


Metal bends when over streessed .......
wood just goes SNAP
buy the jacking tray made to be used for your lift

 

[Falcon67]

Just a note to add that I handled $1000 worth of #2 grade or better 2x12s building my new shop. Wood these days is **** - laid flat, no way I'd use two layers as a jack tray. Period. My door beam is 16 1/2' dual 2x12s with a 1/2" ply center, built with construction glue. It's on edge and still the minimum for the span.