Load capacity of a homemade jib crane

[mike_sou]

Hello! I am hoping this is an easy problem for the brains in here to solve.

I am designing a jib crane that will go on the roof of a building to hoist air conditioning compressors up 5 stories. The HVAC units are no more than 300 lbs. I will use a steel cable and a hand winch to pull them up.

The crane will be slipped over an existing pipe on the roof. It will be able to swivel around the pipe so we can swing the units in. I am not worried about the strength of the existing support pipe. We'll brace it and cable it to make it strong.

I am wondering about the weight capacity of the arm. How much weight can it carry?
We plan on using steel tubes that will be welded together.

The dimensions in my drawing are to achieve the clearance needed to clear the overhang and swing the units in over the wall.
What do you think?

Thanks in advance!

jib=crane.jpg

[Kelly_Bramble]

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