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I want to build a custom power rack to safely perform heavy barbell exercises in my home. Commercial racks are too tall for my basement.

Others have done this before: http://www.home-gym-bodybuilding.com/homemade-power-rack.html

One aspect I'm unsure about is how much space between holes in the upright posts I need to safely support the weight.

For those unfamiliar, a set of safety bars (1" solid steel bars) goes through the holes on each side. If you fail to complete a lift, you set the barbell on the safety bars and wriggle out from underneath.

500lbs would be a generous upper limit for the combined weight of the barbell and weight plates. It's fathomable that this weight may be dropped from let's say a foot above the safeties. Generally, I expect to be able to set the bar down gently, but that might not always be the case.

Placing the holes closer together allows for better placement of the safety bars and barbell holders. Several people will be using the rack, so I cannot simply place holes where they are best for just me.

I threw together a SketchUp model of what I'm planning. The holes will be 1 1/8" diameter (need to check actual diameter of some pipe to be sure). Currently, I have them spaced 3" on center. The holes are also be a bit off center, moved out towards the edges of the uprights, so that they are spaced far enough apart.

Can anyone help me to understand how I could calculate if this is structurally solid?

I understand wood is rated in compressive strength by psi. I'd be grabbing the best 2x6's I can find at a big box store, which looks like top choice hem-fir. I find some calculators, like this - https://courses.cit.cornell.edu/arch264/calculators/example7.1/index.html. That shows 840lbs for a 2x6, but 3846lbs for two 2x6's (I will be gluing two 2x6's together for each upright).

I'm not totally sure how to calculate the surface area. Obviously it's 3" through the board, but with a round pipe in a round whole, would I use half the diameter of the hole (3"*1&1/16*π = 10 sq in), or less? What's the effective area in contact with the pipe to determine the psi applied to the uprights?

I also don't know how the holes in the board affect the compressive strength.. I would assume it lowered it, but when I search about it I don't see length/height of board taken into account.

Any help would be greatly appreciated. Here's the sketchup

rack from front

rack from rear

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I have a 7 piece metal cage that is about 75 inches high. It supports up to 600 pounds easy. If you are doing heavy lifting I would not trust 2x6s unless this was a last resort. (my cage cost me $150 on craigslist) –  DMoore Jun 3 at 17:58
    
@DMoore I've been searching CL for weeks with no luck yet. Many people have built wooden racks with 2x6's or 4x4's, even ones with additional plate storage on the side. –  qes Jun 3 at 19:08
    
I will try to take a picture of mine. I know it is so old that there is no name on it. But it is 2 front supports and one back (middle support) that has a pulley. Bar sits out of cage which I prefer anyway. I would really really be concerned about bench pressing. If you are doing 300 and a support snap right after you set it... You might be dead - even with a spotter. –  DMoore Jun 3 at 19:44
    
@DMoore But what's going to happen if it does fail? The wood between two holes will split. I really doubt the bar is going to fall all the way, splitting through every hole. Nor would the uprights crack right in half and fall over or anything. The bar won't be over my neck anyways, I'll be pushing it down towards my legs and sliding up as if I were failing with no safeties on an open bench. I do 5x5 sets, I'm not putting up a weight that's going to come crashing down suddenly. –  qes Jun 3 at 19:50
    
What is keeping the peg system adjustable and attached to the holes? What I am saying is your fail point isn't really the rack itself it is the support pegs that you sit the bar on. I used to work out in a gym where we had wood racks but these were 4x4s with a step system. –  DMoore Jun 3 at 20:03
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