How much weight can an m24 (4.8) threaded rod support?

[Filletj]

Hello!
How do I calculate how much weight an m24 4.8 graded threaded rod can withstand?

The rod is 1 meter long, and the weight will be approximately in the middle of the rod. The rod will act as a safety together with an identical threaded rod in a homemade barbell rack. The weight will be about 75-100 kg per threaded rod. Should they be able to handle this?

 

[pjkw]

If I understand you correctly, you should be able to drop/shed the barbell on this bar... Then I think you need to go up a bit in dimension, why do you want a threaded rod and not a steel profile?

 

[Filletj]

If I understand you correctly, you should be able to drop/discard the barbell on this rod... Then I think you need to increase the dimensions, why are you specifically using a threaded rod and not a steel profile?

Thanks for the reply!
Yes, exactly, if some kind of accident occurs during a lift, I want the safety to withstand a drop from at least 0.5-1 meter height. Under normal use, significantly less/gentler stress.

By steel profile, do you mean something like a steel tube? The reason for the threaded rod is that it's convenient and cheap to just go to Biltema to buy one. Also, the diameter is quite small, which is good because it needs to be threaded through two holes in two horizontal 95x95 beams!

 

[SSlangen]

About 15 tons to break... but maybe you are strong, read again, 15 tons is if you pull on the threaded rod. Probably strong enough but I wouldn't have chosen a threaded rod for that purpose.

 

[Filletj]

About 15 tons to break... but maybe you're strong, read again, 15 tons is if you pull on the threaded rod. Probably enough but I would not have chosen a threaded rod for that purpose.

Thanks for the response! 15 tons sounds more than sufficient. What would you have chosen instead?

I was also considering buying 2 Galv threaded pipes DN25 (33.7x3.2mm). Should that work better?

 

[Bjober]

Sounds like you're going to bend the bar?
Then it doesn't handle many kilos.

 

[Filletj]

Thanks for the reply! 15 tons sounds more than enough. What would you have chosen instead?

It sounds like you're going to bend the bar?
Then it can't handle many kilos.

No, I don't intend to bend the bar, I preferably want something that doesn't bend at all under the load!

 

[gbgustaf]

Perhaps you should draw a sketch to avoid misunderstandings? There is quite a difference if the force is acting along the rod or across it. And where the rod is attached also matters.

 

[Filletj]

Maybe you should draw a sketch to avoid misunderstandings? There is quite a difference if the force acts along the rod or across it. And where the rod is attached also matters.

Hope this is understandable! The frame is seen from the side and will consist of two identical ones as shown in the sketch. The load will, therefore, occur on 2 identical threaded rods if I need to release/drop the barbell during a lift!

 

[Bjober]

Hope this can be understood! The frame is seen from the side and will consist of two identical ones according to the sketch. The load will therefore occur on 2 identical threaded rods in case I need to quit/drop the barbell in a lift!

Hope this can be understood! The frame is seen from the side and will consist of two identical ones according to the sketch. The load will therefore occur on 2 identical threaded rods in case I need to quit/drop the barbell in a lift!

Yes, that's how I perceived it. You are going to subject the rod to a bending moment. Then it can't handle many kilos. Why not take a piece of wood that stands on edge if you are building everything else in wood anyway? Or are you going to have several holes so it becomes adjustable in height?

 

[Filletj]

Yes, that's how I perceived it.
You are subjecting the bar to a bending moment. It can't handle many kilos like that.
Why not use a piece of lumber set on its edge if you're building everything else from wood anyway?
Or are you planning to have multiple holes to make it adjustable in height?

Yes, exactly, I plan to have multiple holes to make it adjustable!

Okay, thanks for the important input. Maybe it's better to go for galvanized pipes instead?

 

[cpalm]

Maybe it's better to go for galvanized pipes instead?

Yes, some form of profile provides a lot more bending stiffness/strength per kg of material (= per kronor) compared to a solid rod.

 

[z_bumbi]

In certain constructions, you want deformation of the safety bars to protect the rod and prevent bouncing. Then it also depends on the weights involved, if you routinely bend 250, it requires more than 150, etc.
With that out of the way, you can go for a substantial design, but it's possible to construct in other ways than a continuous steel rod.

 

[Filletj]

In certain constructions, you want deformation of the safety bars to protect the rod and prevent bouncing. It also depends on the weights involved; if you routinely bend 250, it requires more than 150, etc.
With that out of the way, you can go big, but it is possible to construct in a different way than using a solid steel rod.

Thanks for the response!
How would you have solved it instead of using a solid rod/pipe?

 

[Thomas_Blekinge]

Yes, exactly should have several holes to make it adjustable!

Okay, thanks for the important input. Maybe it's better to go for galvanized pipes instead?

It's not possible to calculate. You can quite easily calculate the static load and what the bar can handle (depending on the bending you accept). But calculating dynamic loads like when weights are dropped is quite impossible because the input data is not known. For example, do both bars hit exactly at the same time? From what height? Angle?