Gravity + Weight + Angle= Failure?

"Del the cat" Yes I agree 27 ton jack stands would definitely hold a 27 ton vehicle. However, that's not the answer that I'm looking for. Mainly due to the fact the 27 ton (30 ton) jack stands would be too heavy for single individual to maneuver. In this case, human factors would come into play, as the individual would not utilize the 30 ton stands and revert back to the 10 ton stands due to them being significantly lighter in weight.

Again thanks, but I am looking for an engineering answer. These guys have enough to worry about rather than jack stands collapsing.

then you might use 3 x 10 ton stands.

the formula is 10 + 10 + 10 = 30

30 > 27, therefore adequate.

_{^{Del made me do it}}

JD, my thoughts exactly. I agree it would be > half the rear vehicle weight. The absence of positive vertical lift and even weight distribution actually would increase the weight to a single point due to the negative angle.

Thanks Again

A great and correct answer, the first one to correctly explain why the jacks are collapsing!!!

To the OP.

In reality, depending upon the way the truck is loaded, there could be anything up to around 18 tons on that one jack.

Furthermore, why are they being jacked up 18 inches? just enough to get the wheel off the ground is enough and before working on the wheel, a chock that can withstand at least 20 tons needs to be inserted in case the jack collapses.

I always use the spare wheel when working on a car, buying a new spare wheel would be cheaper than a new arm or leg.......Remember, something expensive will "cost you an arm or a leg!!"

Tornado, it collapsed...bent in half. I'll post a pick soon. Thanks for the info.

Could you use two 10 tons?

I would still like to see a pic of the bent jack...

Maybe you can double up with two 10-ton jack stands, making sure to advance them equally.

Yeah, that's what I'd suggest also; use two jackstands. And thoroughly brace the opposite side of the vehicle to make sure it can't roll or shift (forward or backward) when you apply torque to the hub you're working on.

Nope, two jack stands won't work because the axle will be at an angle and only one jack stand will contact it until it begins to buckle at which point the second jack stand will take the full load plus whatever momentum it may have acquired when the first jack buckled.it will buckle even faster than the first one did as a result. bottom line they won't share loads equally so this is not a workable solution.

What are you doing with the jack that you used to raise the vehicle?

Can you leave the vehicle up on the jack and place the jack stand along side it as a backup?

The weight, combined with the angle is too much. You may want to raise the entire rear of the truck and put both left and right side on jack stands. This will have the weight pushing straight down, rather than on an angle. Whichever side you are working on, also place the jack itself with slight pressure against the axle to double the support on that side.

I don't know what the formula is, but if you have a stick and try to break it by placing the end on the ground and pushing straight down, it's almost impossible. Take the same stick, put an angle on it and apply fairly slight pressure to the center and it will snap in two.

Also, I'm assuming you have limited resources.

The trick here is to keep that rear axle straight and parallel to the ground while raised.

You can take advantage of the geography of the land under the vehicle to achieve this, by either parking the truck with the left rear tire on a small hill or digging a shallow depression and parking the truck with the right rear tire in the depression, leaving enough room to get the jack under the axle, so that it will be parallel when raised. This will allow you to get by with one jack stand.

This should work. That said, I would never recommend working on a raised vehicle and depending one just one jack stand for support............you need a backup. This can be as simple as sand bags piled up along the length of the axle on the side you are working on. The extra time it takes beats the hell out of having the guy working on it get crushed.

Re: Can you leave the vehicle up on the jack and place the jack stand along side it as a backup?

Hmm, I would never use a jack for a support, backup and especially not primary, especially if the jack is hydraulic. (I think this would even be an OSHA violation in the US.)

Hmm, I have a professional heavy duty floor jack. These are used regularly alone. I assume that it is not an OSHA violation since this practice is routine at garages and tire places here in the US in full view........I've never heard of anyone getting written up for it.

If the OP is attempting to use a cheap jack to raise a 27 ton vehicle, that is not rated to do the job, he is looking for trouble from the start.

My jack is fully capable of both raising.......and holding my truck off the ground. I use a jack stand against the axle as a back up, just in case a hydraulic seal decides to bust loose on the jack.

Go outside and take a look at the jack that was supplied with your vehicle that supposedly is designed to hold it up by itself, while you change a tire on the side of the road and tell me some more about OSHA rules.

deleted--basically duplicate of next comment (not sure how I accomplished that--must have fat fingered something)

Re: Hmm, I have a professional heavy duty floor jack. These are used regularly alone. I assume that it is not an OSHA violation since this practice is routine at garages and tire places here in the US in full view........I've never heard of anyone getting written up for it.

Yes, you're right, I've never heard of anyone getting written up for it. We would never have tried anything like that around the coal mines I worked in. Maybe the difference is whether anybody actually puts any part of their body at risk under the item being held by the jack.

(OT, but BTW, I know that those--hmm what do you call them--floor lifts that raise an entire vehicle have mechanical locking devices to be put in place after a vehicle is raised so the vehicle is not solely supported by the hydraulic system.

See post #17. Duh.................we could all be helping out the enemy. US personnel don't come to CR4 to figure out how to jack up a truck. That question should have been the first one asked.

Kramarat, How many insurgents "you" think own or possess 27 ton vehicles? Don't have time for this. Thanks again JD and Tornado. Signing off and GOD Bless.

My jack is fully capable of both raising.......and holding my truck off the ground. I use a jack stand against the axle as a back up, just in case a hydraulic seal decides to bust loose on the jack.

My post from #15. I use a jack to raise the vehicle, followed by a jack stand under the axle.........using them both in conjunction. Looks a lot like the OSHA rule.

Maybe you just didn't read the entire post. Thanks for reiterating my advice.

Is this a good "back up"?????

I don't think that you would catch me lying under that!!!!

Yes.........it looks like he has a piece of scrap carpet on the ground to prevent his back from getting scratched up. That's exactly what I would do.

"PERFICK"

Aha! "The Darling Buds of May," I like it!!!

Who doesn't like C.Z.J.???

You ain't wrong their chief!!

I didn't know, until recently, that this series actually started her career in acting.

Kramarat, the difference is that in those instances (tire places) nobody gets under the vehicle so a collapse is unlikely to kill anyone. If anyone were to get UNDER the vehicle however a jack stand that can take the entire full load (with a decent margin of safety) would be mandatory. Take it from someone who has had a vehicle fall on them when a jack collapsed.(I was in the process of removing the jack stands when the jack collapsed... )

Good answer. I usually raise both sides on stands rather than one, though if I do use one side I always make sure the stand is secure and that there are two of them rather than one. I place one more forward and the other toward the rear of the vehicle. Another thing is that I always put something under the axle or nearby just in case the stands fail and I am under. Even putting the wheel under just as a back up and I leave the jack in place as well, In this way you have three points of contact with the vehicle and a buffer in case. Perhaps a bit overkill but whey your life is involved, nothing is too much.

Rail road tie or other large timber.

I'm an engineer. I use a 12" x 14" x 30" chunk of solid wood under the axle when I lift something. I first raise with a jack and then lower on the wood. I'm pretty sure it the timber's welds won't fail and the bars won't bend when I am under it.

Sorry, I just take my safety too seriously to trust a jack stand made from welded bars of metal.

Your comment a 30T stand would be of no use, cuts no ice with me. If needs be put a gas axe through the 10T stands. Refusal to use safety is an offence under HSE laws.

By the way.........Are you on our side?

If not, gather up some friends, prop the truck up on an inflatable ball and crawl under it.

If you are, then please accept my sincerest thanks for what you're doing over there. There are millions of us that think about you every day.

I suspect the jackstand collapsed because the load on it was transmitted to only one of its legs, due to this "angle" you're talking about. That said, your attitude stinketh. To excuse poor jacking technique on the basis that the jackstands are too heavy to manipulate is an unfortunately common, and criminal, act. After fifty years of watching people make heavy equipment mistakes, I can only ask: "What were the exact circumstances of the failure?" Were the front wheels solidly blocked, with wedges, or just rocks. (If the truck was free to roll on the front wheels, it could unequally load the jackstand legs.)

Ormondotvos,"attitude checked, thank you sir". Surface: Concrete, Flat and level. All tires blocked/chalked. There was no rolling of vehicle nor shift left to right. Jack stand bent in half. The overpressure was to the left side of the jack stand due to negative left angle. Yes I agree the poor technique was the root cause of the failure. However I must rule out malfunction of equipment (jack stands). This is the reason I ask the question. You have 50 years experience so I know you understand how hard it is to change human work ethics especially in a location or atmosphere where enforcement of safety laws are not predominate nor a priority.

10 or 20 tons is not much to hold up. Given a 10 ton stand would have a 2 to 3 factor of safety as a matter of course, 'vertical load wise', around a square inch of steel would appear to be adequate.

Where the complications enter, is lateral forces - by slope, or applied by people working on the vehicle.

E.g. a burly lad on a 6 foot bar, cracking wheel nuts, exerts a quite a lot of 'destabilizing force' - well enough to distort chocked tyres.

So if the stand is 'rigid' and fixed vertical (by flat base on flat on concrete) - if there is a 'hinge point' in the 'ridgid' riser, such loads will find it.

There are common 'trucking practices' to reduce these forces, such as wooden blocks and hard rubber mats, but as you say it's not a normal situation.

You wrote they "bent in half", which leads me to think what you may have here is 'naive' design regarding these lateral forces and the work environment.

It could also be substandard manufacture, 'grand fathered' specs, the usual 'oversights'.

However; I'd first suspect it's 'naive design', but without a picture of a good one and a failed one, it's just guessing.

The formulae is simple, ALLWAYS keep the vehicle level,ie if you're jacking the rear put stands under both sides, an axle stands strength is straight down through the centre line not sideways. As for which stands to use, the strongest ones you have.

As an after thought as to a safe way to lift the truck with only 10 ton jacks, and I must stress this would have to be proven as follows. (PS I notice this has been touched on above).

The transfer of load from left to right (left still supported), is due to the twist in the trucks frame, when the frames flexibility reaches maximum it starts to transfer load to the jack. So if you only have 10 ton jacks, then it may be possible to lift the rear right in steps, first the left putting support blocks under your lift, then moving to the right side and do the same, the procedure to be done, each side, before the trucks frame starts to transfer load.

NOTE care should be taken when reversing this procedure.

Regards JD

I have noticed this angle change in the jack body as well on much smaller vehicles. I correct this by starting out with an angle in the opposite direction.

Not sure if this meets correct safety standards, but it works with the equipment I have available.

Oh yeah, I all ways put something (like the tire and rim I just took off) between the axle and the ground hoping it will take the weight long enough for me to get out if something fails.I do not trust the seals in my jacks that much.

good luck and thanks.

I'm currently in Afghanistan and have an issue with collapsing jack stands on two occasions; luckily no one has been injured.

I've been giving this thread some more consideration.

Don't take this personally, but my best advice is not to take any of the advice from these posts.

You've got a really heavy truck there and you're online trying to figure out how to jack it up.

My advice is to ignore these posts, go to your superiors, and admit that you're in over your head, before you do manage to get someone injured or killed.

I know a guy that's actively fighting in Afghanistan and a couple of others that work for civilian contractors. They either know how to work on the equipment they're dealing with or have access to the people that do.

You're not the guy for this project.............and there's no shame in that, there's plenty I don't know.

There's far too much risk in this endeavor for someone without intimate knowledge of the tools and techniques to be used, to even attempt it.

I don't doubt that you have the expertise to carry out the repairs once the truck is off the ground. Getting it there requires someone with knowledge specifically in heavy equipment work. Hopefully there's someone there that can lend a hand.

a " x5 " safety factor should be used when it pertains to personal injury. if you're breaking 10 ton stands, use 50 ton stands

if the weight 50 ton jacks difficult to move, then i'ld suggest attaching heavey duty spring loaded casters wheels to the legs that would allow you to easily move the jack stands an enable the legs to settle to the floor as weight is applied

Just a couple quick questions.

Does the truck in question actually weigh 27 tonnes or is it rated to carry 27 tones?

Are you working on it fully loaded?

Most trucks I've seen have the rear axle significantly closer to the center of mass than the front wheels so they would carry much more than half the weight.

Norco Jack Stand with a pin style design and 10-ton capacity (each) features a lift height from 18-1/2" to 30". This unit, made in the USA, is designed to support vehicles in fleet garages, agricultural, and construction maintenance shops where a pin-type height-adjustment

I don't know what kind of stand you are using but once you get to the height you need you can measure the distance under the main support bar...from the bottom of it to the ground and find a machine repair shop at one of the bases that has bar stock or square stock and cut four pieces to fit under the post directly and scrap the locking pin. This will give you more support vertically directly to the pavement or concrete like a solid bar…should work better than the tripod legs will and the legs will still hold it steady for side by side movement.

If you have the jack stands with the flat bottom plate and the support post you can get 1/4 steel tubing with an I.D that fits around the diameter of the main support post ...split it down the middle and get someone to weld a flange on each side of your split tubes drill 3 holes and tap for wing nuts. Attach them around the center post. This will make a sleeve that you can put on quick in between the bottom plate and under the neck of the top resting point and make your 10 ton jack stand into a 15 ton jack stand if not better. Try to get a predetermined height that you know you can work with that touches both the bottom plate and under the neck of top resting point. The wing nuts will hold it in place. This is just an idea that might help you with limited resources you have. Test it first… we had to make some crazy stuff ourselves but you do what you have to...to get the job done. You just need some added reinforcement. Hope this gives you some ideas you can work with. God bless you brother.