Jump to content

Maximum safe clearance with jacks.


Hodgepodge
 Share

Recommended Posts

Ok, I'm not new to this.,  I just took inventory and I have 12 different jack stands ranging from 2 to 6 tons each.   I am pretty religious about jack safety and, in addition to setting a 3rd or 5th jack stand, I still push any removed wheels under the car out of habit.  

 

I'm thinking about what I will need, lift-wise to rehab the entire suspension and clean/detail/paint the underside of my 2002 and I would really like to get the maximum safe clearance under the car to be able to do that.  I do not have a lift and don't have the room in my garage to put one....except maybe one of those portable lifts.   I've used chassis jigs, body jacks and rotisserie stands before, but this application doesn't really call for any of that.  Ideally, I want to get the car 30-36 inches or so off the ground lifting from body hard points, not suspension.  Why so high?  Because I don't want to be working on my back the whole time when dealing with drivetrain, exhaust and paint.  The issue with lifting that high, of course, is stability and safety.  My tallest 6-ton jack lifts to about 24 inches on a 9-inch base (and I've never been comfortable using these jacks fully extended).  12-ton jack stands lift to about 30 inches on a 12 inch base.   Now, I've pushed pretty hard on cars to make sure the jack stands are stable, but I don't think I've done that with the stands fully extended.  I'm guessing that there is some geometry and physics involved in determining that safe height-to-footprint ratio..... does anyone know what it is?  

 

I knew one guy in Atlanta who welded 16 inch plates to what were probably 8-ton jacks (at a 45-degree angle to the legs) to maximize the stability.  He would practically tackle a car to show how stable this was but he usually worked on bigger american cars so he still had room to move around underneath them.  Under a 2002, plates that size would practically touch,. leaving little room to move around.      

 

Does anyone have any suggestions?    How comfortable are you working under a car with the jacks fully extended?   

 

Thanks,

 

Scott

 

 

Edited by Hodgepodge
Link to comment
Share on other sites

Personal comfort is one thing but I would imagine that the stands should be good for their rated load at maximum extension.   This, of course, assumes a static load that only bears vertically within the jack stand's base area. If you jack it up and then start tackling seized nuts with a breaker bar and long cheater bar, the forces are no longer solely vertical and risk toppling the stands. The taller the stands then the easier this will be. A small shift may also cause the jack to slip to an inappropriate position to support the load. 

 

If you consider the risks associated with the amount of side wards force you are likely to apply and the chances of the stand slipping (where it touches the body / subframe) you should be good. 

Link to comment
Share on other sites

2 minutes ago, Simeon said:

Personal comfort is one thing but I would imagine that the stands should be good for their rated load at maximum extension.   This, of course, assumes a static load that only bears vertically within the jack stand's base area. If you jack it up and then start tackling seized nuts with a breaker bar and long cheater bar, the forces are no longer solely vertical and risk toppling the stands. The taller the stands then the easier this will be. A small shift may also cause the jack to slip to an inappropriate position to support the load. 

 

If you consider the risks associated with the amount of side wards force you are likely to apply and the chances of the stand slipping (where it touches the body / subframe) you should be good. 

That's exactly my concern.  I have used 4 jacks under a car many times, but the torque required to, say, loosen or tighten a connecting bolt to remove or install an exhaust system is nothing compared to removing a 40-year stuck sub-frame bolt.  I think what I may do is search for some larger 10 or 12 ton stands and back-off a it from maximum height for good measure.   I was hoping that somebody knew of some other shop stand that would fit the bill, but I'm not too optimistic about that.  I do see some fairtrly expensive and highly rated Sunex 1410 10-ton stands that extend to 46 inches, but they look a little too scary for me and I honestly don't know how I would jack my car up that high.   

 

Thanks,

 

Scott

 

Link to comment
Share on other sites

Gotsta say after having the original 02 Red Beast jump a jack and damn near kill me what I just saw scares me. The acceleration speed of a ton of metal doesn't offer a second chance.

I hired my welder, recently he bought a lift. A Benji gets me four hours of lift time and his help. Not looking back, highly recommended. If you organize and prep your chores it's amazing how much you can get done

Rear brake rehab including lines. Mechanical clutch linkage rehab, and finish fab and weld for replacement trunk and quarters are up at next session.

Could never get it done with Jack stands. 

The neighbor pulled my stands out of his pool. Working great for tarp ballast. 

Link to comment
Share on other sites

How about a heavy metal bar bolted to each of the two jackstands at either end of the car, like a beam between the two jackstands, thereby connecting them together and increasing their stability? It seems they wouldn't be able to simply fall over that way. Or a long metal plate underneath the stands and then weld the stands to the plate? Or both, for that matter, the plate underneath and the beam. It would be similar to a lift made expressly for your car, but your jack would be the lifting mechanism. I had a car come down in just the manner you describe years ago. Fortunately I wasn't underneath it and the wheels were still on the car. Scary, to say the least.

Link to comment
Share on other sites

I just finished doing what you are about to start. (total suspension refresh & painted underside.) in my opinion I think 30-36 might put you at somewhat of an awkward working height, where it's to high to work off your back but to low to sit up under (though I could be wrong). If had as many big stands as you I would have gone up a little higher but not much. Just my .02.
I'm the same as you though, I always slide the tires underneath no matter how secure it is. I saw a guy once that had a tiny scissor /baby jack on top of 2 pieces of firewood and he was half under the car. I had to get out of there as quick as possible because I didn't not want to see him get crushed. 1bec7b30695471659a46b901b62ba78f.jpge94a535ad0560999f5c1b03ab44a752f.jpg

Sent from my SM-G930P using Tapatalk

Link to comment
Share on other sites

Scott,

 

Had you considered a home built tiptisserie?  Something like Raj's tiptisserie.

 

Rehabbing the suspension is easy, because its all carried on subframes which can be easily removed, rehabbed and reinstalled as units.  But with the front subframe out, you're not that far from having the engine out and the shell being ready to tip.  It would sure be easier, safer and turn out 100 times better if you did the paint rehab on the bottom while standing, working on the tipped car.  Just imagine how crappy it'll be lying on your back for days, scrubbing, scraping, sanding, priming, sanding, and painting.  

 

BTW, I'm not convinced that Raj's is the one you should build.  There are a bunch of different designs on the internet.  Google tiptisserie and diy car rotisserie.  

  

Edited by g_force
Link to comment
Share on other sites

Wow, that thing is pretty cool!   I don't quite have room to do this and really don't want to pull the engine if I can help it, though.   Maybe I can make the stand and rollers part and use that.  It looks pretty stable.  

 

Many years ago I bought a 1960 MGA that needed a complete rebuild.  I stripped that car down, pulled the frame off and the engine out and built a wooden jig for the body to sit on.  Work progressed very slowly, but it progressed.  Then my company made me a great offer to move....  I boxed up everything and put in in storage for a while, but I ended up selling the car to a British car specialist/restorer/parts seller and I'm 99% sure it never went back together.   I am retired now and won't be moving for several years, but that restoration I could not finish left an indelible mark on me.   I still enjoy working on and restoring cars, but I try to keep the focus on one or two areas at a time as opposed to completely dismantling a car.   

I'll get over it eventually.  :-)  

 

 

Thanks,

 

Scott

  

Edited by Hodgepodge
  • Like 1
Link to comment
Share on other sites

3 hours ago, Bibm5 said:

I just finished doing what you are about to start. (total suspension refresh & painted underside.) in my opinion I think 30-36 might put you at somewhat of an awkward working height, where it's to high to work off your back but to low to sit up under (though I could be wrong). If had as many big stands as you I would have gone up a little higher but not much. Just my .02.
I'm the same as you though, I always slide the tires underneath no matter how secure it is. I saw a guy once that had a tiny scissor /baby jack on top of 2 pieces of firewood and he was half under the car. I had to get out of there as quick as possible because I didn't not want to see him get crushed.
 

 

Your lift looks very creative and to be honest, before I saw yours and the other images using wood I never thought about just creating box-stands out of 4x6 lumber.  The idea is to create picture frame-like things out of 4x6 boards that are the correct size to hit the hard points.  Then you slide them in one at a time when you are jacking up the car and secure them together with a brace or angled lag bolts.  Technically, the bottom one could even be on locking casters like a regular box jig.   I'll have to think about this a bit.....  Probably overkill.  If I knew I was going to be doing more than one car, I'd seriously consider it, though.  

Link to comment
Share on other sites

Yes the higher you raise the upper portion of any jackstand the wobblier it's going to be, to get my cars onto my rotisserie  I raise the car with one set of jackstands as high as they will go and then switch to my heavier set 6 ton I think set pretty low and set on blocks I made using 2x12's 4 layers high screwed together with each layer 90' to lower one to prevent splitting with a plywood collar on top cut out so the stand base can't slip off, by slowly lifting in stages I get around 30-32" clearance with little or no wobble. Like you I take jackstands as a necessary evil and use extreme caution with them almost a ridicules point.  

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

 Share

  • Upcoming Events

×
×
  • Create New...