H bracket for an electric hoist

I am building an “H” shaped bracket to support an electric hoist. The bracket will be mounted between two “Z” beams that run lengthwise supporting the roof. I am making this out of black pipe and fittings. The sides of the H will each consist of a 24” piece of pipe connecting to a 36” piece of pipe with a Tee fitting. The two Tees will be joined with an 18” piece of pipe, making the “H”.

The four corners will each have a floor flange screwed on. The flanges will be bolted to the “Z” beams. In case it matters, the roof has a 4/12 pitch thus the bracket will be so tilted.

The maximum weight that will ever be supported by this bracket (including hoist and load) would be under 475 pounds. My question is what is the smallest black pipe I can use to make this work safely? The bracket for the hoist could be mounted on a pipe with an OD of up to 1 ½ inches but I was figuring on using ½ inch (or even ⅜ inch) pipe if that is strong enough.

I’m not an engineer or student and have been unable to find any info about the strength of black pipe. Also, I wonder, if I found it, would there be a weakening where the connections are?

Thanks for any help anyone can provide.

As much that I want to help you an answer would require significant amount of effort. First, I would need to model your frame in a 3D CAD software or break out each subframe element into my FEA software. I would need to calculate the area moment of inertia and estimate the material engineering properties. Additionally, I would need to design a welded connection and calculate the strain, strain and deflections.

You're asking for a full engineering and design analysis - 20 hours of effort?

Here's my best suggestion.. If available, look at similar structural frames and understand the loads which they carry. When a suitable example is found - reproduce the structural details.

If you cannot find suitable design example - go big and strong with the pipe selection. Over engineer it and you'll likely be good.

Of course you could also pay somebody (engineer) to design it for you as well.

Kelly,

Thanks for the reply. However you might as well have replied in a foreign language as I understood little of what you wrote. I thought someone would have some idea of what type of weight an H frame as I described would hold depending on the size of the pipe used.

I guess not.

I did get the concept of over engineering and will likely do so.

Derby