kaymccampbell
Well-known member
Have you put your heaviest vehicle on it yet, raised it up n given it a good shake?
Any pics loaded?
Any pics loaded?
Ben Wil two post mod
- Thread starter EVOLVO
- Start date
Lotek
Well-known member
I've worked under hoists for my entire career, I own one of those hoists for my personal shop. That's beyond sketchy. The forces on those arms can be uuuge, When you pick something up, they don't just sag, they also twist, look at the wear marks on the pivot pins. As someone suggested, a far better solution would have been to fab up a couple dollies to drop the arms on, pull the pins and roll out of the way. On another note, I don't see any evidence of the arm restraints being installed. That's a second major fail. If I had to do something like this, I would have put a far more substantial hinge on the top bar instead of what looks like a gate hinge on the main arm, and sleeved the arm with a pin retaining it. I wouldn't stand under that with a go cart lifted on it.
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lakeroadster
Well-known member
Please.... don't use the lift in the as modified configuration.
The tensile loads on the top strut plate you cut are extremely high. No way your idea of using bolts in single shear can be adequate. 86turbodsl is a brave man jumping into this mix.... lot's of liability on his part.
Do I still see paint on the arms in the area where you are going to weld?
Did you even grind the mill slag and torch residue off the hinges in the areas you are planning to weld?
Holy Schnikeys... Maybe follow your own advice, the one in your avatar?
The tensile loads on the top strut plate you cut are extremely high. No way your idea of using bolts in single shear can be adequate. 86turbodsl is a brave man jumping into this mix.... lot's of liability on his part.
Do I still see paint on the arms in the area where you are going to weld?
Did you even grind the mill slag and torch residue off the hinges in the areas you are planning to weld?
Holy Schnikeys... Maybe follow your own advice, the one in your avatar?
Attachments
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Have not put my truck on it yet, will do soon.
Please.... don't use the lift in the as modified configuration.
The tensile loads on the top strut plate you cut are extremely high. No way your idea of using bolts in single shear can be adequate. 86turbodsl is a brave man jumping into this mix.... lot's of liability on his part.
Do I still see paint on the arms in the area where you are going to weld?
Did you even grind the mill slag and torch residue off the hinges in the areas you are planning to weld?
Holy Schnikeys... Maybe follow your own advice, the one in your avatar?
All areas to be welded have been thoroughly prepped. I love my avatar!
86turbodsl
Well-known member
Ok, so you're loading it up with your heaviest vehicle. I sent you my bolt calculations. When it fails, it'll fail catastrophically. Your vehicle will be on the concrete faster than you can imagine. As i mentioned in my PM, i DO NOT RECOMMEND this modification. You are stressing those bolts very close to their yield limit. when i'm using the post hole digger with the shear bolts in the shaft, it doesn't give me any warning it's going. It just snaps and i have to replace them. it doesn't fall on my head though.
86turbodsl
Well-known member
I ran the bolt calculations for shear on the top member. It said it was marginal at best. I recommended he NOT do this modification. I told him i wasn't responsible and that he shouldn't make this modfication. I don't believe i'm liable if he doesn't follow my advice and does it anyway.
FWIW. I told him i would do an FEA on the assembly, but i don't think i'm going any further with this.
EVOLVO, for the love of GOD, please put some high jackstands under all 4 of the corners of your vehicles before you stand under it. If you HAVE to go down this road, use something to hold the vehicle up and don't stand under it while it is being unsupported.
Buckgnarly
Well-known member
Fixed it. I really hope no one runs with this idea that may stumble on this thread.
lakeroadster
Well-known member
Well said sir.
Evolvo... Don't use the lift arms you modified.
I did a quick FEA on my Rotary lifts short arms, but modified the model using your hinged method.
In addition to 86turbodsl concerns detailed above, if there is just a slight amount of torsion on the arm, the lower tube twists and folds at the hinge.
And as 86turbodsl pointed out, there won't be any warning signs.
Don't be fooled by thinking that lifting a 4,500 lbs vehicle with your 9,000 lbs rated lift with modified arms is testing anything.
Again, Don't use the lift arms you modified.
We have no skin in the game sir, we're merely looking out for your safety.
Lotek
Well-known member
I showed a pic to the guys installing 6 new hoists at the shop today, they've seen a lot, but nothing like that...
Super Mech
Well-known member
There is a guy on here that made a rain barrel stand with similar weight calculations. Maybe he can help you. I wouldn't get under that. Good luck though.
like2wheel
Well-known member
Haha, this reminded me of that thread too. He was in total denial tho. This OP is a much better sport.
Lotek
Well-known member
There's a company in San Diego that might have replacement arms, I can get the number from my hoist guys if the o/p's interested...
n20junkie
Well-known member
Hell to the ****** no. That damn thing is a ****** death trap.
OP has no clue what he is doing, and WILL hurt someone with that thing.
Bolts in single sheer, a ******* hinge under tension. Sure, it picked a truck up. Lift that truck up about 12” and start rocking it by the rear bumper. That thing will fail like a long distance relationship.
OP has no clue what he is doing, and WILL hurt someone with that thing.
Bolts in single sheer, a ******* hinge under tension. Sure, it picked a truck up. Lift that truck up about 12” and start rocking it by the rear bumper. That thing will fail like a long distance relationship.
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n20junkie
Well-known member
If you were going to attempt to use any sort of engineering, the hinge would be for folding only. The lift side stub should have at a MINIMUM a boxed socket with a properly rated pin that went into a sleeved hole to tie the arm back together.
If ANY part on that contraption fails, the absolute lack of any redundancy will cause a cascading failure faster than a person could react.
JFC people do some dumb **** sometimes.
I did bring it up about a foot off the ground and using the materials rack on the truck rocked it from side to side and fore and aft until the whole rack was swaying. That's the reason I stopped rocking it, it didn't fail. I've only done the two arms on one side, so after all my best attempts to get it to fail I compared the arms from one side to the other. All four arms show some sag, caused by the clearance of the trolleys that slide up and down the posts. All arms measured within .3* of each other. It's for my own personal use, it's NOT going to fail!
Lotek
Well-known member
86turbodsl
Well-known member
Bring it a foot up and fully loaded with your heaviest stuff, then let it sit there for a week. If it isn't on the ground by then, pull the bolts and look at the plastic deformation. You're on borrowed time, i hate to say it.
R. Deschain
Well-known member
nope, nope, nope... Up your life insurance. Seriously.
mike93lx
ALLIANCE MEMBER
Subscribing just for the chance of an update when it does fail
Old Man Roger
Well-known member
If he isn't under it when it fails.
n20junkie
Well-known member
At least the lawyers for the lift company have a solid defense when he gets squished under this future darwin award winner.
Aahz
Well-known member
That lift company has been out of business for years! I am going to print these pics and hand them over to my ALI Certified Lift Inspectors, just so I can watch them go ballistic!
n20junkie
Well-known member
Guaranteed to make the next powerpoint on user mods.
86turbodsl
Well-known member
I would really like to hear what they say when you do!!!
Old Man Roger
Well-known member
A video would be better..lol
I am the guy that started the lift modification thread on this board. I am not one of the engineering nazis. I will tell you that I am greatly concerned for you.
My humble opinion, given solely in hopes that it rings in your head with the rest of them. My opinion is that you should buy replacement arms and never use these ones as you have designed.
Even my crazy brain is telling me that this is just not safe at all.
Its your life though. Just dont let anyone else under it though as they will certainly be in danger.
Sorry man. Good luck
My humble opinion, given solely in hopes that it rings in your head with the rest of them. My opinion is that you should buy replacement arms and never use these ones as you have designed.
Even my crazy brain is telling me that this is just not safe at all.
Its your life though. Just dont let anyone else under it though as they will certainly be in danger.
Sorry man. Good luck
86turbodsl
Well-known member
Back to the top, the OP hasn't been here in almost 2 months. Still ALIVE? I'm wondering!
Buckgnarly
Well-known member
I think he has been busy leading the team that came up with this....
https://www.garagejournal.com/forum/showthread.php?t=411830
86turbodsl
Well-known member
I'd feel better about that thing than the evolvo mod.
Bad00SS
Well-known member
I skipped to the last page after seeing the photos to see if the OP has been to the ER yet or not. This is beyond risky. I don't even know this guy and I feel bad knowing something is going to happen eventually.
SickSpeedMonte
Well-known member
In addition to twist, it's not considering the shear forces in the cantilevered beam (square section). The square section's bending stress and shear stress are eliminated now. It's pretty much in compression only now. The shear stress goes through the hinge.
The forces through that top support are probably at least an order of magnitude higher than the vertical load applied to the pad due to the shallow angle and the leverage of the arm. You have two pairs of bolts in series on the top support. So the force going through the support is only reacted by two bolts, each in single shear, screwed into threads tapped into the existing support.
You have to assume the entire weight of the vehicle is reacted by only TWO of the arms. That's how rigging calculations are done too. I know vehicles aren't infinitely stiff in torsion, but you can imagine if a vehicle was able to rock at all because the lift points weren't coplanar or the pads weren't adjusted properly, you can imagine a scenario where the vehicle could rock like a table that needs a shim under one foot. In that case, the load is really only on two arms. I know you shouldn't get under that anyway, but you don't design for ideal conditions, you design for worst case.
That plate welded under the box section (the "mod" introduced a few posts after the OP) appears to do nothing. If anything, it should have been welded to the other side but that still wouldn't make this safe.
The forces through that top support are probably at least an order of magnitude higher than the vertical load applied to the pad due to the shallow angle and the leverage of the arm. You have two pairs of bolts in series on the top support. So the force going through the support is only reacted by two bolts, each in single shear, screwed into threads tapped into the existing support.
You have to assume the entire weight of the vehicle is reacted by only TWO of the arms. That's how rigging calculations are done too. I know vehicles aren't infinitely stiff in torsion, but you can imagine if a vehicle was able to rock at all because the lift points weren't coplanar or the pads weren't adjusted properly, you can imagine a scenario where the vehicle could rock like a table that needs a shim under one foot. In that case, the load is really only on two arms. I know you shouldn't get under that anyway, but you don't design for ideal conditions, you design for worst case.
That plate welded under the box section (the "mod" introduced a few posts after the OP) appears to do nothing. If anything, it should have been welded to the other side but that still wouldn't make this safe.
finn
Well-known member
Hope his widow is getting the support she needs.
86turbodsl
Well-known member
It's been 6 months since he's been here. When was the funeral?
The lift is still working great, no issues at all. I don't put cars on it very often, just the occasional oil change or brake job.Plastikosmd
Well-known member
- Joined
- Nov 17, 2016
- Messages
- 1,254
Nope, no thanks but I admire your commitment
Maybe add side gussets that interlace and you can drop a hardened pin to support?
That would at least add back some of the sidewall strength lost (top tension/bottom compression)
Maybe add side gussets that interlace and you can drop a hardened pin to support?
That would at least add back some of the sidewall strength lost (top tension/bottom compression)
RWorth
Well-known member
The only issue I have with your mod is that it is easier to just pull the pin and set the arms on the floor in the corner. I'm 66 and I pull mine every time I'm done with it. They're not that heavy.