Ben Wil two post mod

[EVOLVO]

I installed a used GPO-9 in my fab shop last year for my own use. Trouble is the lift arms are always in my way. I'm 6'2" tall and the arms don't go that high so I always have to flip them around so I don't bang my head. Having them at floor level is an unnecessary trip hazard. So I came up with this modification. I think I might get slammed pretty hard for this, but I'll take my chances!
I tried to get the pics in order, hopefully you'll understand what I'm doing.

 

[LXCam]

The safety nazi's are rallying now. I hope you have your fire suit on

 

[EVOLVO]

Let em' fire away!! Yesterday I couldn't spell engineer, now I are one!!

 

[JohnnyK8]

Subscribing for a good read later!!

Sent from my Moto G (5) Plus using Tapatalk

 

[maxpat82]

so you replace a 1/4" thick square tubing by a 1/8" rolled over the pin hinges.


Look safe to me....


should read scary..but that's just me :|

 

[quadrcr87]

Can't see it from my garage

 

[EVOLVO]

Yes, I did. I also replaced the 3/8" angle strap with 1/2" thick stuff to make up for it. Not really the way that would work, I know. But the arm, where I cut it is in compression and the hinge is reinforced by the strap. Do you think I should put bolt on reinforcement plates that span over the cut? I don't!

 

[EVOLVO]

Can't see it from my garage

Exactly!!

 

[LXCam]

Let em' fire away!! Yesterday I couldn't spell engineer, now I are one!!

Lol

I have a four post but the cars I focus on for the most part all require you lift the body of the subframe to do a motor swap. 10-11 years ago I built a support system that cantilevers off the ramps and supports the unibody frame. It works like a rockstar but for some reason seems to scare the living **** out of anyone watching

 

[Movover]

I guess my only thing is that 1/2" plate do you bolt it on and off every time you need to flip it up? If so then why not just make a quick way to remove the arms all together with a pin or something, obviously you took them off to cut and weld them?

 

[EVOLVO]

I guess my only thing is that 1/2" plate do you bolt it on and off every time you need to flip it up? If so then why not just make a quick way to remove the arms all together with a pin or something, obviously you took them off to cut and weld them?

They're pretty damn heavy so taking them on and off every time would leave me too tired to do any more work. With the plate I can just hit the bolts with my rattle gun, ezpz. With the ability to raise them to a comfortable height I can use leverage to easily flip them up out of the way.

Next?

 

[landlord30]

I like it.

 

[kelpaso1]

That's seems pretty dicey if you ask me. I hope you don't use it to hoist a 5000 pound car and stand underneath of it

 

[EVOLVO]

That's seems pretty dicey if you ask me. I hope you don't use it to hoist a 5000 pound car and stand underneath of it

My hot rod weighs #3000, my 1937 Austin 7 weighs #850. I'm willing to roll the dice, but after I complete the other 3 arms and test it out if you don't hear from me you'll know I rolled snake eyes!

 

[86turbodsl]

Can't say i'm a fan of that one. Would you like me to run a few calculations on relative bending strengths of the assemblies? Send me some dimensions if so.

 

[firebirdparts]

I have had my lift almost 20 years and it never occurred to me to trip over the arms. I've sure hit my head a bunch, while a car is on it, but never tripped of them even once. FWIW.

I could remove the arms in about 1 second per arm but I never bothered. they are held on by a pin that is just dropped in and sits there with nothing holding it down but gravity.

 

[Falcon67]

I trip on mine occasionally. The internal response is more "watch your step *******" than "I need to fix that"

 

[EVOLVO]

I trip on mine occasionally. The internal response is more "watch your step *******" than "I need to fix that"

Back in 2007 I had an accident at work which pinched the nerves running down the right side of my body and required me to have a cervical fusion of my neck. C4-5-6 have a titanium plate screwed in place. Because of this I drag my right foot and tripping is a constant issue for me and I fall a lot. I am a *******, too!

With that said I still don't think this mod will be a problem. If it makes you all happy it occurred to me that I could weld a 1/4" plate on the bottom of the now liftable portion of the arm. This plate would span over the cut and further prevent the arm from tipping down under load.

 

[garagelogician]

I'm not sure I would feel comfortable working under that. But...you do you. As long as you are the only one working under it, and you have adequate life insurance...send it.

 

[86turbodsl]

Back in 2007 I had an accident at work which pinched the nerves running down the right side of my body and required me to have a cervical fusion of my neck. C4-5-6 have a titanium plate screwed in place. Because of this I drag my right foot and tripping is a constant issue for me and I fall a lot. I am a *******, too!

With that said I still don't think this mod will be a problem. If it makes you all happy it occurred to me that I could weld a 1/4" plate on the bottom of the now liftable portion of the arm. This plate would span over the cut and further prevent the arm from tipping down under load.

The trouble with that is, you have removed the tensile capability of the brace and replaced it with 4 bolts in single shear, and really only 2 bolts because you aren't 4 across to spread the loads. You have also removed the bending resistance of the 4" 1/2 wall box section and replaced it with a hinge that has a single pin in shear.

As a mechanical engineer, that mod has red flags popping out all over the place for me. My advice is worth what you paid for it, but i would be VERY uncomfortable getting under that lift arm without some solid design margin calculations completed and maybe even an FEA.

I would exercise extreme caution on that!

 

[Buckgnarly]

This looks like a really, really bad idea. 16 (really 8 as mentioned) bolts holding the weight of the car, all to solve a problem that does not exist.
Kind of hoping this is a joke, but much like a scene of an accident, subscribed!.....

 

[moreover]

The trouble with that is, you have removed the tensile capability of the brace and replaced it with 4 bolts in single shear, and really only 2 bolts because you aren't 4 across to spread the loads. You have also removed the bending resistance of the 4" 1/2 wall box section and replaced it with a hinge that has a single pin in shear.

As a mechanical engineer, that mod has red flags popping out all over the place for me. My advice is worth what you paid for it, but i would be VERY uncomfortable getting under that lift arm without some solid design margin calculations completed and maybe even an FEA.

I would exercise extreme caution on that!

All this^^^ That square tube was doing quite a bit in the strength department. I bet if you didn't bolt that piece of strap steel in there, you could hang 300lbs off the end of the arm and open that hinge right up.

 

[kingchevy]

I'm no engineer, but it looks like a terrible idea. If the load isn't centered on the lift pad, it will want to twist the lift arm. I guess you could weld tabs in the sides of one tube or the other to help with that.

 

[EVOLVO]

The trouble with that is, you have removed the tensile capability of the brace and replaced it with 4 bolts in single shear, and really only 2 bolts because you aren't 4 across to spread the loads. You have also removed the bending resistance of the 4" 1/2 wall box section and replaced it with a hinge that has a single pin in shear.

As a mechanical engineer, that mod has red flags popping out all over the place for me. My advice is worth what you paid for it, but i would be VERY uncomfortable getting under that lift arm without some solid design margin calculations completed and maybe even an FEA.

I would exercise extreme caution on that!

OK, you got me on your four bolts in shear statement. I always thought that if you had one bolt with a shear capacity of, say 75,000 psi than four bolts working in conjunction would give you 300,000 psi of shear. I'm probably wrong about that. Don't forget that there are four arms that will be sharing a load of no more than 3300 lbs. As I said earlier I think I will be adding a 1/4" plate welded to the up-swinging arm that covers the cut. This will alleviate any tendency for the arm to lift upwards at the cut. This mod in addition to the bolted plate should take almost all the shear force off the hinge pin. Right?

 

[kaymccampbell]

If I were going to make those arms pivot up, I would use the same size pivot pin as the one that allows the arm to swing sideways. It is designed to take the loads that lift is meant to carry. I would use plates the same thickness as the existing pivot plates to make my hinges, in the same design as the sideways hinge. I would also put a square tube inside the existing square tube to make a mortise and tenon to fully engage both sides of the cut portion of the arm.

 

[gungatim]

LGR!

 

[mmb617]

I gotta agree with gungatim on this one. I've been accused of doing things that others didn't feel were safe from time to time but I wouldn't trust that setup. At all.

 

[stingry]

Let em' fire away!! Yesterday I couldn't spell engineer, now I are one!!

NO, you are not!!! As an ME myself, I can say that this is really a BAD idea! Although your intentions were good, you have inadvertently put a tremendous amount of stress on that hinge point. Yes, bolting on that bar will probably prevent it from failing, but what have you gained?

 

[EVOLVO]

NO, you are not!!! As an ME myself, I can say that this is really a BAD idea! Although your intentions were good, you have inadvertently put a tremendous amount of stress on that hinge point. Yes, bolting on that bar will probably prevent it from failing, but what have you gained?

Stingry, If you agree that the bar will keep this mod from failing than I have gained exactly what I wanted. An easy way to get the arms out of my way and not have to worry about taking up more room in my small shop figuring out where to store them.

 

[finn]

You rarely see things designed like that for another reason that I don’t think was brought up yet: the lift arm has now become a massive pinch point in the event something goes wrong and it drops to the horizontal position.

There’s a big difference between being able to fabricate something and being able to engineer something.

In addition to the mechanical and structural calculations necessary to determine the margin to failure under load, an engineer will generate a fmea to address things like pinch points.

 

[EVOLVO]

The arms will be stored in the upright position and tied together with a piece of line. This will prevent an accidental drop. Although if you look at the pic of the arm in the upright position it is way over center and takes a bit of effort to lower it to working position.

 

[firebirdparts]

. If it makes you all happy it occurred to me that I could weld a 1/4" plate on the bottom of the now liftable portion of the arm. This plate would span over the cut and further prevent the arm from tipping down under load.

I was thinking tube-in-tube would be even better, but your way would be a nice improvement.

 

[SimS]

I must have missed something. Why don't you raise the arms up to the top lock for storage? No one says you have to store the arms on the floor. If you have time to bolt and unbolt arm bracing, you have time to lower the arms before use.

SimS

 

[RWorth]

Just my 2 cents, I'm no engineer but I have learned that my common sense has been pretty good for 65 years. That being said I have nothing against modifying your lift, I have been the target of the engineer nazi's on several occasions as I have extensive mods to my 2 post. However that doesn't look adequate to me. I had the same issue and I just pull the pins and place them on the floor in the corner of the shop, they're not that heavy. No mod needed. I'll bet I just got 2 redemption points from the Engineer Nazi's

 

[EVOLVO]

I must have missed something. Why don't you raise the arms up to the top lock for storage? No one says you have to store the arms on the floor. If you have time to bolt and unbolt arm bracing, you have time to lower the arms before use.

SimS

You did miss something, I'm taller than the arms when they're in the full up position.

For all you naysayers, 86turbodiesel has kindly offered to do an analysis on this mod. I sent him some dimensions last night, I'm patiently waiting for his reply. I'll let you all know what he says as soon as I know.

 

[like2wheel]

Anybody selling a single lift arm for a GPO-9?

 

[EVOLVO]

One won't be enough!

 

[sierradmax]

I'm sure at some point during design, a lift manufacturer ran the design calculations on "folding lift arms" similar to your design. More than likely, they came to the conclusion that it's inadequate after loading to 200%.

I like the idea. But I would make a HSS 3-sided (two side & bottom) spliced connection to bring back some rigidity to the HSS tube.

 

[Old Man Roger]

I think you may have failed to consider twist.

 

[Old Man Roger]

I recommend you weld it all back together, and use the dolly advice given.