How much weight can safely be suspended from center of 2"x2" square tube 9' long?

[LD1]

Re: How much weight can safely be suspended from center of 2"x2" square tube 9' long?

Tubing is usually ASTM A-500. Tensil and yield depend on grade A, grade B or grade C.
A=39ksi yield 45ksi tensil
B=46ksi yield 58ksi tensil
C=50ksi yield 62ksi tensil

For my number's earlier, I used 50,000 psi for max allowable stress at the loads listed. A 40ksi steel would be allowed to lift 80% of my figures.

5:1 SF is a good thing when working with unknown steel. Stay within that, and even if calls were for a grade C and you use grade a...you should be fine

 

[Streetcar]

Re: How much weight can safely be suspended from center of 2"x2" square tube 9' long?

Tubing is usually ASTM A-500. Tensil and yield depend on grade A, grade B or grade C.
A=39ksi yield 45ksi tensil
B=46ksi yield 58ksi tensil
C=50ksi yield 62ksi tensil

For my number's earlier, I used 50,000 psi for max allowable stress at the loads listed. A 40ksi steel would be allowed to lift 80% of my figures.

5:1 SF is a good thing when working with unknown steel. Stay within that, and even if calls were for a grade C and you use grade a...you should be fine

The factor of safety is because of the uncertainty in determining the stress from a dynamic load, not for over estimating the strength steel. For unknown material 36ksi is typicall strength assumed

 

[LD1]

Re: How much weight can safely be suspended from center of 2"x2" square tube 9' long?

Engineering a nuclear reactor, 1000t crane, battleship, sky scraper ....i agree.

But we are talking a home shop. How many would just do it and not even ask. And if it bends, try again with something heavier.

I have NEVER seen grade A tube. B is the most common.

And remember yield is Not the failure point. That's just the point of bending beyond return. Exceeding Tensil is failure

 

[Will S]

Re: How much weight can safely be suspended from center of 2"x2" square tube 9' long?

Here's an update:

I got hold of a 2 ton portable shop crane today, so I'm going to use that and do the work here. I was going to have to move the boat to a friends home-shop, but the boat is nearly as wide as the OHD opening, and would be a real PITA to move it there.

Since I already welded up this thing, I decided to add a 1.5"x3/16"x6' flat bar, welded to the bottom of the 9' beam, with a 4" bridge spacer at the center, forming a V-truss, in case we ever want to use the lift to pick up something with a hook from that lift.

May never use it, but this has been a fun and educational project to me. Thanks to all who contributed.

 

[Streetcar]

Re: How much weight can safely be suspended from center of 2"x2" square tube 9' long?

1000 t falling on you will kill you, several hundred pound could kill you. Same design methods.
Yielding of the steel can cause buckling and failure.
It is fine to cut corners on personal safety, recommend it on forum is another matter

 

[jenkinsph]

Re: How much weight can safely be suspended from center of 2"x2" square tube 9' long?

Here's an update:

I got hold of a 2 ton portable shop crane today, so I'm going to use that and do the work here. I was going to have to move the boat to a friends home-shop, but the boat is nearly as wide as the OHD opening, and would be a real PITA to move it there.


Since I already welded up this thing, I decided to add a 1.5"x3/16"x6' flat bar, welded to the bottom of the 9' beam, with a 4" bridge spacer at the center, forming a V-truss, in case we ever want to use the lift to pick up something with a hook from that lift.

May never use it, but this has been a fun and educational project to me. Thanks to all who contributed.

I have a similar shop crane and that is what I would use to lift my outboard. Much better to use to reposition the motor when you want to put it back in place too.

 

[LD1]

Re: How much weight can safely be suspended from center of 2"x2" square tube 9' long?

1000 t falling on you will kill you, several hundred pound could kill you. Same design methods.
Yielding of the steel can cause buckling and failure.
It is fine to cut corners on personal safety, recommend it on forum is another matter

I didnt recommend anything. Its simple math and numbers. I laid out the facts, grades, capacities, and what I based it on. Take the info and do with as you please. THAT I am not responsible for. And I am not trying to mis-lead anyone.

If the setup you has allows an 800# SWL at a 5:1 capacity, and you want to push it to 900# and may only leave yourself with a 4:1 safety....I aint gonna stop you. Just give you the appropriate info as I have done.

 

[Renze]

Re: How much weight can safely be suspended from center of 2"x2" square tube 9' long?

If the setup you has allows an 800# SWL at a 5:1 capacity, and you want to push it to 900# and may only leave yourself with a 4:1 safety....I aint gonna stop you. Just give you the appropriate info as I have done.

Indeed. You gave outputs based on certain conditions, but did not give a judgement on if those conditions were met. You cant see that from behind a computer screen, and you cant know if the one reading it is capable of making the judgemental decision based on the info you provide. So that leaves the decision, as well as liability, at anyone who uses the info you provide.

I usually ignore the posts about "who can calculate this and that load for me" because those who know enough to judge the condition of pre-used materials, and if all conditions are taken into account, dont ask and just do. Those who will overlook a certain condition that is essential to the outcome, are usually the theorists who asks for calculations on forums.

Whenever i calculate a load for someone, i go there to look at the situation personally. If a person isnt able to estimate nor calculate the load, he/she isnt capable of correct judgement of the circumstances and conditions either, so i dont give a false sense of security of a correct calculation based on incorrectly supplied data and conditions

 

[jenkinsph]

Re: How much weight can safely be suspended from center of 2"x2" square tube 9' long?

Will,
I hope you got your motor fixed for the holiday.

This thread reminds me why I like to go fishing alone. I can see you guys arguing about the forces on a fish hook in another boat (hopefully).:laughing:

 

[Will S]

Re: How much weight can safely be suspended from center of 2"x2" square tube 9' long?

Will,
I hope you got your motor fixed for the holiday.

This thread reminds me why I like to go fishing alone. I can see you guys arguing about the forces on a fish hook in another boat (hopefully).:laughing:

No arguments from me, , I just asked a question. Lots of things to consider, for those who want to discuss it, but I just wanted to see if using material I had, could work with my friends lift, to safely lift a 400# motor.

In the end, I got a 2T HF shop crane, and we did the job, but it took longer than anticipated, (don't it always). When I got the motor off the boat, I saw a corrosion problem with the trim-tilt motor, and had to take care of that, since I already had access to it. That's all done now, and everything is back together. Shop crane was perfect for the job, and I didn't have to tie up a lift for 2 days.

Never bothered finishing up the original project for the auto lift, and now that we have a shop crane, no need for it.