1

I have a pull bar. It is 48 inches in-width and spans out 32 inches with the "pullup" portion of the bar located 30 inches into the spanned out end portion.

I would like to know how deep should I make the post hole. How wide? Should I use rebar? I would like the 4x4 to be 48 inches apart and 7.5 feet above ground. I would like to keep the post deflection at a minimum (if none at all). The pullup bar will be used by someone who is 300lbs so the post must be able to withstand the force of 300lbs muscle up and clap pullups (basically a 300lb man hanging from it and swinging) (the pullup bar is capable, the only questions are the post)

My plan was to make each post hole (2 post) 15 inch diameter by 48 inch deep, and on the 4x4 in-ground portion drill out some holes to friction place some rebar through the post so that it protrudes on each side a few inches in a attempt to help the concrete bond to the post better and better "stabilize" the post.

FlexBendDeflect
  • 13
  • 3
  • 1
    Your plans sounds solid, I would over-engineer it and go with 6x6 posts. – JD74 Apr 18 '23 at 01:20
  • 2
    Where are you located and what type of soil/ground will you be digging into? – UnhandledExcepSean Apr 18 '23 at 01:36
  • @UnhandledExcepSean Southern California and the soil is regular loam. – FlexBendDeflect Apr 18 '23 at 03:44
  • @JD74 I need to keep the dimension 3.5 inch width for other purposes so for that reason If I do move up it will be a 4x6 which I am not opposed to either and might be the better fit however I also don't need this to last 20 years my main concerns are post deflections. – FlexBendDeflect Apr 18 '23 at 03:48
  • Or this? What is the formula for fence height and fence post length? – isherwood Apr 18 '23 at 13:28
  • 1
    You might think that fence post discussions are not relevant to something designed to carry human weight, but wind force can be at least as great as anything you're likely to impart. I'd follow the same rules. – isherwood Apr 18 '23 at 13:29
  • @isherwood The main concern is deflection which I edited the title of my question to better reflect. One of those links deal with a postmaster post not a wood post and the other link does not factor in the wind force as stated by the guy who answered that question. – FlexBendDeflect Apr 18 '23 at 19:24
  • You don't think fence builders are concerned with deflection? I addressed that in my comment. You will not impart more force on the thing than an 8ft. by 6ft. fence panel in a stiff wind would incur. You're not breaking new ground here. :) – isherwood Apr 18 '23 at 19:27
  • Aesthetically and psychologically (even though that was not your question) if I were a 300lb person doing clap pullups I would very much enjoy 6x6 posts even if your planned ones (actual 3.5x) are technically strong enough. Build it so you will not have to say "don't worry, I looked it up, you'll be fine". – jay613 Apr 18 '23 at 19:37
  • @isherwood well I just went to those two links you provide and in the accepted answer the guy who answered the question commented that he did not factor in wind force into his answer. Now in your original reply to me you compared my cantilever pull up to be the same as wind force, so... accepted answer said he did not factor in windforce. I just relayed that back to you. I know theirs different formulas for cantilever installation vs fence post installation and I am just seeking the correct way to install my setup not a "good enough" type of approach. – FlexBendDeflect Apr 18 '23 at 19:40

1 Answers1

0

Since you've eliminated 6"x6"s as an option and you are concerned about deflection of the posts, my suggestion is to use 4"x6"x12' posts. The 4" face should be oriented towards the pullup bar. The rest of your plan sounds very robust for installation.

The depth of the install you suggested was 48" which is very deep, but the deflection isn't based on the depth of the beam into the ground. The entire thing overturning is the reason to burial depth when you have a 0" frost depth area like southern California. Loam soil doesn't pack very well, so a 48" depth in a 15" wide hole filled with concrete will work very well.

UnhandledExcepSean
  • 8,744
  • 5
  • 34
  • 43