landry
Well-known member
Just to work on your paranoia, link to a recent Utube video on a Corvette being rescued from a 4 post lift whose “latch” on one post seems to not have latched…
Four post lift failure…
- Thread starter landry
- Start date
racecougar
Well-known member
My understanding is that the root cause here was a cable failure.
rjacobs
Well-known member
cable failure on a lift on the locks should not cause this. NOW if it wasnt quite on the locks yet then yea sure.
My lift has dual locks and one is a cable lock if the cable loses tension the secondary lock will engage. At least thats how I understand the secondary lock works.
racecougar
Well-known member
Well yeah. Based upon what we can see in the video, namely the height at which the runways are on the other three posts, I would venture a guess that the cable failure occurred during up/down travel. The runways were awfully low for the exhaust installation that was intended here.
Same here. From what I've gathered, this was a cheap lift provided by the fairgrounds (note the little concrete pads poured in the middle of the show field for it). Who knows what brand it was, how it was cared for/inspected, etc.
c39er
Well-known member
***Improper setup/assembly on uneven mud slabs in car corral.
***Improper operator error while lowering runways.
***Improper operator error while lowering runways.
Buckgnarly
Well-known member
Only close calls I have had with students and lifts were with the 4 post. They get complacent and dont watch all four posts. Just had this happen Monday actually, one of the 4 locks hung up.
finn
Well-known member
Piss poor video. Mostly the back of someone’s head. Why bother?
They say the cable broke, but no pictures or evidence to support that. A separated cable should result in the safety latch grabbing the next slot and minimizing the drop, unless the lift was somehow installed improperly. The cables only come into play when the lift is being raised or lowered. The catches are what support the runways when the lift isn’t in motion, so there’s no static tension on the cables.
They say the cable broke, but no pictures or evidence to support that. A separated cable should result in the safety latch grabbing the next slot and minimizing the drop, unless the lift was somehow installed improperly. The cables only come into play when the lift is being raised or lowered. The catches are what support the runways when the lift isn’t in motion, so there’s no static tension on the cables.
I wonder if the lift was stopped at or cable failed between “catches” or lock points and one post failed to catch fast enough on the way down?
I “grew up” (father had one in his shop) using the old style 4 post lift that had a single external cylinder mounted on top of two posts with chains, the cylinder had a “lock“ and each post had a single rod and catch mechanism that was supposed to lock the rack in “any position” if a chain broke or cylinder failed (kinda like an elevator, tension on chain kept lock mechanism open, preventing the catch from gripping-locking down on the rod on each post). The carriage of the lift was only supported by the chains as only the single lock on the cylinder was locked during normal use.
Thankfully we never saw the catch mechanism “tested” in all the years of use, but I thought the newer system of catches “locked” on more modern lifts would be more robust and safer? Guess it is still defeated while lifting or lowering the vehicle…
I “grew up” (father had one in his shop) using the old style 4 post lift that had a single external cylinder mounted on top of two posts with chains, the cylinder had a “lock“ and each post had a single rod and catch mechanism that was supposed to lock the rack in “any position” if a chain broke or cylinder failed (kinda like an elevator, tension on chain kept lock mechanism open, preventing the catch from gripping-locking down on the rod on each post). The carriage of the lift was only supported by the chains as only the single lock on the cylinder was locked during normal use.
Thankfully we never saw the catch mechanism “tested” in all the years of use, but I thought the newer system of catches “locked” on more modern lifts would be more robust and safer? Guess it is still defeated while lifting or lowering the vehicle…
racecougar
Well-known member
On most modern 4-post lifts, there are two sets of catches for the locks. One set is defeated via the operator handle when lowering, but is otherwise spring-loaded/functional. You'll hear this set "clunk" as you raise the lift. The other set is defeated by cable tension, but is spring-loaded into action should a cable become slack/fail.
It is far more robust/safer than the old way, like this one: https://www.garagejournal.com/forum/threads/older-4-post-lift-safety-suggestions.536769/
racecougar
Well-known member
Agreed that the video was terrible. As far as the cable failure, you can make it out briefly in the video. This is one of the cheaper lifts with the cable outside the columns. The cable is clearly in place on the right side of the photo, and it does appear to be snapped on the left side of the photo. I put a little red arrow where the cable is sticking out from the column.
firebirdparts
Well-known member
it is what it is. You should be able to look at a 4 post lift from across the street and say to yourself "that's an inherently weak design." Having done that you really should be careful. Fear will help you a ton here. That's what I think. I always cringe when people talk about putting wheels on them, as this obviously makes it a lot harder for the sliding moment connections to withstand any deviation in the universe. on the other hand, if that gives you terror instead of fear you might be able to pay even more attention.
I don't know if user attention and the locks would have done any better than this or not. Looks like the car didn't get busted up.
I don't know if user attention and the locks would have done any better than this or not. Looks like the car didn't get busted up.
finn
Well-known member
Still not clear that the cable separated. Both my Advantage lifts are set up like that. If the lock linkage isn’t set up properly by the installer, I could see issues potentially arising. If set up correctly, though, the dogs will lock in the slots in the improbable event of any sort of cable separation . The operator has to hold the lock lever when lowering the lift, or it stops when the dog reaches the next slot.Agreed that the video was terrible. As far as the cable failure, you can make it out briefly in the video. This is one of the cheaper lifts with the cable outside the columns. The cable is clearly in place on the right side of the photo, and it does appear to be snapped on the left side of the photo. I put a little red arrow where the cable is sticking out from the column.
In any event, the cable likely isn’t going to break unexpectedly., barring a visually worn and frayed cable, failure of the crimp holding the cable end, or failure to install / tighten the jamb nut holding the end of the cable. The cables are pretty lightly loaded ( at least mine are), especially with a relatively light car like a Corvette. I think that in general, the lightest duty lift is around 7000lb rating, probably about double the weight of a Corvette.
The whole deal here shouts setup error or operator error rather than “he should have bought a $20k Mohawk because anything less is Chinese junk”.
Viper98912
Well-known member
On my 4 post, the cable itself (under lifting tension) has to push a roller out of the way which is what's moving the sprung lock out of the way. That way, if the cable snaps, the sprung lock snaps back in and should theoretically engage the next slot 6" down.
Now of course, this is all in theory.
Those fairgrounds are probably fairly limited in supplies, but I would've tried to find a tall jack to get that corner back up as much as possible before trying to remove the car
Now of course, this is all in theory.
Those fairgrounds are probably fairly limited in supplies, but I would've tried to find a tall jack to get that corner back up as much as possible before trying to remove the car
racecougar
Well-known member
That screenshot is the clearest image I was able to find. Going from what is visible there, plus the comments from those in attendance at Corvettes at Carlisle, it sure appears that it was a cable failure.
kbuhagiar
Well-known member
All due respect, but one person in the background saying "I heard it was a cable failure" doesn't make it a cable failure.
It may very well be, but I've been around car guys all my life; all it takes is for one clown to say the first Corvettes had steel bodies, or that his friend's buddy's uncle has a rare 1983 Corvette, etc. etc. before everyone starts repeating it.
And Corvette wannabees are the most gullible.
ZRX61
Well-known member
Didn't occur to one person there to stick a floor jack with a piece of 6x6 on it under the low corner & raise it up level with the other 3 corners so they could just drive the car straight back...
racecougar
Well-known member
I get that. I'm just going off of what I'm reading on the forums from the guys who were present. I wasn't there myself.All due respect, but one person in the background saying "I heard it was a cable failure" doesn't make it a cable failure.
It may very well be, but I've been around car guys all my life; all it takes is for one clown to say the first Corvettes had steel bodies, or that his friend's buddy's uncle has a rare 1983 Corvette, etc. etc. before everyone starts repeating it.
And Corvette wannabees are the most gullible.
racecougar
Well-known member
My understanding is that a vendor at Corvettes at Carlisle was doing an exhaust install.
To each his own, but I sure as hell wouldn't have someone work on my car on grass under a tent. And I would be suspect of any shop or vendor that thought it was a good idea... but that's me
I've also seen catastrophic dyno failures at these kinds of events by people who had no clue about what they were doing.
To me it's like going up to a carnival and asking a carnie, "HEY would you mind seeing if you could fix my car?"
racecougar
Well-known member
Me either.
I see what you did there... and I also agree with that statementMe either.
cvairwerks
Well-known member
Look closely and you can see that both posts closest to the camera are bent. Doubt you could jack it level without cratering the whole lift.
Buckgnarly makes a good point on the four post lift, if one lock hangs up and the operator is not paying attention the lift will not be happy, I have done it myself....once, well maybe twice, but now I always check as its going down. Maybe a big orange warning sticker by the release for students to remind them. I also never let anybody under the lift or around them when operating them, just in case. Safety first every time. Maybe some of you remember the old two post lifts with the very large cylinders in the floor? The controls where separate in a steel box in the cement floor at the front of the vehicle, one valve for the front post and one for the rear. The rear post had a U bracket that held the rear axle and the front had pads. Remember when first using it I was somehow kneeling on the floor looking up at this chevy impala that some how was almost at a 45 degree angle pointing front down as the rear end was going up way faster than the front. That unit toke some time to get good at those lift valves. Crazy times back then.
Stick-man
Well-known member
Well, I have to admit, it just happened to me, and I got really lucky. I even deliberately positioned the release button so you are most likely to be facing the car as it goes down. I failed to move my head continuously to all four corners. I caught it but it was leaning enough that the hung up lock column actually got bent a bit. Nothing structurally, but the open side where the two ends are rolled in, got bent. It could have been bad because my kids truck was on four bottle jacks!
Again, I got really lucky. Now, I make a point to bounce my eyes on all four corners until it's on the ground.I guess all my younger days of working in shops with no functioning locks made me complacent.
finn
Well-known member
Same thing happens on a two post lift if one of the safety catches hangs up.Well, I have to admit, it just happened to me, and I got really lucky. I even deliberately positioned the release button so you are most likely to be facing the car as it goes down. I failed to move my head continuously to all four corners. I caught it but it was leaning enough that the hung up lock column actually got bent a bit. Nothing structurally, but the open side where the two ends are rolled in, got bent. It could have been bad because my kids truck was on four bottle jacks!
I guess all my younger days of working in shops with no functioning locks made me complacent.
I experienced it myself when I was setting up my two post Bendpac. The left (far side) release cable had a little too much slack and didn’t fully release the dog. That side got hung up.
Easy fix, but I’m sure those cables will stretch with time and use and will have to be readjusted eventually. Seeing one side come down, but not the other made me very attentive any time I lower a car.
That was my thoughts as well.
It may be the picture angle but the pads don't look level with one another.
Secondly, what was the concrete mix used ? Cheap bag mix, cheapest slump load by truck available and was it allowed to cure ? Were the anchors put in correctly ? How thick are those pads ? If those pads had been put in last year, there has been freeze/thaw cycles, I doubt they were still level.
Did the anchors pull out, causing the post to fail and cable to break ?
We had a discussion about simply using some bagged mix and pouring small pads (like in the video) a few months back.
Add a cheap lift into the equation, I see nothing bad bad news written all over that. Luckily, nobody got hurt.
racecougar
Well-known member
What anchors?
Most cable failures happen when raising or lowering the lift. I have had a couple cables break while lowering a vehicle and it's a scary few moments.
With 4 posts most issues I've seen are the locks not releasing properly.
With 4 posts most issues I've seen are the locks not releasing properly.
Now that you point it out, there are none, or doesn't appear to be any.
racecougar
Well-known member
Yup.
Higgins
Well-known member
Going back years ago to the days of Corvette Bloomington Gold there were several vendors that would show up every yr to install muffler systems.To each his own, but I sure as hell wouldn't have someone work on my car on grass under a tent. And I would be suspect of any shop or vendor that thought it was a good idea... but that's me
I've also seen catastrophic dyno failures at these kinds of events by people who had no clue about what they were doing.
To me it's like going up to a carnival and asking a carnie, "HEY would you mind seeing if you could fix my car?"
The individuals performing the job were employees and you would see them yr after yr.
However, time has passed, and things may have changed over the yrs.
