Mowerpan
Well-known member
That lift looks much too small for that truck. Our 18k rotary we use for medium duty ambulances and cutaway class c motorhomes looks Huge compared to that one.
All Worth 2 and 4 Post Lifts and rolling jacks are MADE IN THE USA.
Thank you!
Maybe next time you'll check the door placard for the gross weight instead of guessing?
so you don't put something too heavy on it? maybe? perhaps?
Good thing no one got hurt.

And I still say that the truck may very well have been a safe weight for that lift but if it was positioned wrong so as to put the majority of the weight towards the front something has to give. I'm no engineer (I've only ridden the train) but if you put most of the weight on one side of the carriage to the point of it binding in the lift post and then try to lift it even more something IS going to give out. This would not be the fault of the lift or the hardening or lack of to the hydraulic cylinder. It would be simply the fault of the guy who positioned the truck on the lift much too far forward. The pictures "appear" to me to have way too much weight towards the front. I was hoping Mr Worth would address this possibility but he seems to have left the building. With all the guys here buying lifts or contemplating lifts in the future I would think it would be the perfect place to comment. Maybe "Mr Worth" is the lawyer for the Worth company ?Bottom line is the lift's safety (pressure) valve should have limited the lift to a safe weight.![]()
I do want to compliment sberry on his return to coherent posting. I guess that bite from the poison spider wasn't fatal. It's nice to have you back. 
Now that cylinder had been seeping a little for a while and the lift does raise a little bit unevenly. I wonder if that side had been doing more work than the other side for a while, since that side leaked and the other side did not....What happened was it raised fine and we set it on the locks with the large jackstands on either end of the truck....went to raise the lift to get it off the locks and the truck started to go down as the pump was running....that's when I saw what was happening to the ram....We have tried to adjust the cables to get it to lift evenly and set the locks evenly but it doesn't work, we can do one, than the other and it does not help it. Im wondering if the columns are a little uneven causing that side to work too hard....
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again, gvwr has nothing to do with what the vehicle weighs. A 4700 will weight right at 12k lbs curb weight, give or take depending on options and accessories.
Your engineering was sound on the recovery - and good idea with the chain around the cylinder. However, an uneven lift is not likely the culprit. For the most part, both sides will be supporting the same weight unless the vehicle is severely tilted and then the low side will be carrying slightly more. An uneven lift is usually the fault of an uneven flow of hydraulic fluid or something wrong with the equalization system. If one side were literally lifting more weight, the vehicle would be incredibly off balance and the lift would be unusable.
What does surprise me a little is that that hydraulic cylinder shaft bent that far and didn't break (thankfully). I don't have much of a hydraulic background but I thought the rod should be a thoroughly hardened shaft...if it were hardened, it should break before it bent that far. If it wasn't properly hardened, it would be considerably weaker.
Hydraulic cylinder rods are case hardened(only the surface), chrome plated and have a soft core. If you look closely at that rod the surface should be cracked. I've seen cylinder rods bend more than that and not break. Now it is possible that it wasn't properly case hardened or was bad metal but that is a part Worth would have purchased from a supplier.
Exactly. The hydraulic pressure is directly related to the weight being lifted. The same premise Mohawk uses to do their "weight" gauge could be used with a relief valve to prevent lifting more than rated capacity.
A bent ram like that looks to me like the carriage bound and stop raising. Or the buckling moment became too great as the ram became long.
Either way, if the overall weight of the truck was too great a simple blow off valve would have saved a lot of hassle before the truck was even off the ground.
ac
You could abuse below ground lifts but above ground, not so much. A sliding front post, fixed rear post below ground lift is what you want for larger PUs from what I've seen. Its what most fleet outfits used, telephone company, electric company etc
My BP XPR-10 has the cylinders mounted the other way. Piston/rod pushes the body up with the load.
R,
HAP
Cylinder rods are not normally case hardened. The hard chrome is used as the wear and corrosion resistance barrier. At least that's what I used when I designed cylinders.
GVWR has nothing to do with what a vehicle weighs.
Actually it does, its just not an exact weight of only the truck. GVWR includes the weight of the truck plus extras. It gets you in the ball park instead of guessing where the ball park might be. As mentioned earlier, these things are all over the place depending on accessories. And from what I have noticed, trucks are not rated to carry that much weight so its usually closer than an educated guess. If nothing else, it gives you a margin of safety because you know its not higher than that.
Maybe so but I doubt the chrome plating is .030"+ thick which is what I've run across on the cylinders we use.
Here is a link to a supplier that offers induction hardened rod stock:
http://baileynet.com/hydraulics/bailey_hydraulics_rod_and_tubes/
T-Frost,
Thanks for the well written post!
Actually it does, its just not an exact weight of only the truck. GVWR includes the weight of the truck plus extras. It gets you in the ball park instead of guessing where the ball park might be. As mentioned earlier, these things are all over the place depending on accessories. And from what I have noticed, trucks are not rated to carry that much weight so its usually closer than an educated guess. If nothing else, it gives you a margin of safety because you know its not higher than that.
Don't really see how that makes sense....To put things into prospective, think about a Duece and a half (M35A2) truck.....They are 6x6 so think about the weight of three rockwell axles, transfer case, 10 sets of wheels and tires vs 6, rated for carrying 2.5 ton off road and 5 ton on road, built to military specs and back when things were actually built "heavy".....and they only weigh 13,530 lbs....The truck plus extras? Extras like the load its designed to carry?
GVWR is the rated weight of truck and load. A new F350 DRW, for examply, has a rated GVWR of over 14000lbs. The truck weighs less than 8000lbs. Not even close. The truck in question, as another, has a GVWR of, most likely, 25000 and some change....yet the truck weighs around 12000. Again, not even close.
I stand corrected....the cylinders I designed were huge and induction hardened rods just weren't available in those large sizes.
Below ground lifts use hollow, multi-stage cylinders, which have incredible buckling capacity. Look at dump trucks...they use the same principle.
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The hoist can be almost level and one cylinder could be taking all the load (as appears to have happened here). Also hardness does not factor in buckling loads. Rod diameter, overall length, the modulous of elasticity of the rod material and the end connection design are used to calculate buckling.
Another thought comes...
...if anyone needs further info on Certified Lifts, there is a great Q & A at http://www.autolift.org/
How? You either have a device that equally distributes hydraulic fluid to the two cylinders or an equalization cable that takes up the minor differences in the motion/load between the two cylinders (which is the case here). The equalization cable only takes up a very minor load component to keep the two cylinders in sync and couldn't possibly carry the entire load of the truck to one cylinder without collapsing the entire lift or breaking sheaves. The physics diagram of the truck on the lift simply can't put all of it's weight on one side unless it is an a VERY extreme angle of tilt. I is engineer too.
I've never seen a multistage below ground lift. Must be a new thing if they indeed exist
Even if it's a single stage cylinder,it's still a single acting cylinder where the rod is normally hollow, full of fluid and under pressure. Without boring you with the details, this type of cylinder design has a very large buckling capacity, but requires a large and deep pit to accommodate the large cylinder.
Not necessarily.The system relief set at the correct pressure should have prevented this.
Agreed, like what has been discussed.Something else going on here.
Synchronization of two structures with cables is notoriously difficult because of the many factors that impact the load, movement and synchronization: cable stretch, bearing resistance, post guide resistance, etc... They require constant adjustment and maintenance.
The leaking packing gland seal did not have anything directly to do with this failure but WHY was it leaking may have. Was the rod previously bent and went undetected? Were there small fractures in the surface of the rod that cut the seal?Now "Titanium Frost" I believe has pretty much hit the nail on the head....Both rams are "T"d together before they go into the pump where any kind of pressure relief would be....I did notice then when it tried to come up off the locks that, that side did want to come up first, casing more than 50% of the load to be applied to the left cylinder. One thing I did also notice while looking back on things is the left cylinder had been seeping a little oil once in a while and the right side never did. I wonder how long this had been doing on for....I believe that having a truck larger than we normally would attempt to put on the lift was the straw that broke the camels back.
I will definitely 100% be getting a hold of "Mr. Worth" about the issues he has brought up and to insure that the equalization cables are correctly set and that the lift is operating as it should. I'm very glad he chimed in..
why don't all lifts have a built in scale?
We have tested these lifts to extremes. It appears to have been overloaded and mis loaded as well. Unfortunately short of getting sworn testimony we will never know. The factory has STILL Not been contacted.
We have tested these lifts to extremes. It appears to have been overloaded and mis loaded as well. Unfortunately short of getting sworn testimony we will never know. The factory has STILL Not been contacted.
...it's actually a pretty tame conversation for an internet forum and there is a lot of information that the lift might not be at fault.

