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I searched but I couldn't really find this answer. I want to use the linked wooden dowel as a pull-up bar. 1.25" oak (not specified which). Is this gonna be strong enough across a roughly 30" expanse to hold up a 200lb man doing pull-ups?

Lowe's link

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  • It depends on how you intend to do the pullups ^_^ Seriously though, huge difference in the strain on the dowel between a standard wide-grip pullup and doing them with a narrow grip in the centre.
    – Graphus
    May 28 at 23:10
  • That is a really beefy hardwood dowel and it seems like it should support this much weight but the span is a worry, how dynamic you'll be doing the exercise matters, and unfortunately a lot rides on the flow of grain in the dowel. Rather bizarrely the other current Question on orienting the grain in a hammer is highly related. Additionally, I know Lowe's don't specify but the subspecies of oak could actually be quite important (not white v red, more detailed than that). And also how the dowel will be mounted each end could be a factor, so please specify if you know how you plan to do that.
    – Graphus
    May 28 at 23:23
  • You are going to want to select your lumber the same way they do for baseball bats. And just like bats, the direction the "label" is in will matter I suspect. That is, the grain structure, and how the force is applied to that grain is going to matter.
    – jdv
    May 29 at 14:25
  • Not an answer because I don't know for sure, but I suspect that wooden poles used for this sort of thing are going to be more than some machined shaped dowel of some species or another. I suggest you research into how old-time wooden poles were made for gymnasium use. The failure mode of random dowels is probably going to be sudden and violent, and fitness equipment probably needed to be springy and resilient. I further suspect that not only does species matter, but hand selection of candidates was necessary, along with construction techniques.
    – jdv
    May 31 at 13:02
  • I would not be surprised if such equipment was made like fishing poles used to be made, with segments of appropriate wood bonded together into a circular cross-section. I would not trust machined dowels of this size to support the dynamic mass of an unsuspecting athlete. Even if it is strong enough on paper, the failure mode is not going to be kind to the user.
    – jdv
    May 31 at 13:06
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TL;DR: Use a metal pole. Commercial dowels are not a good material to use for pull-up bars. The supports for the metal pole can be wood.

I'm going to take the unpopular opinion and suggest that random oak from a big-box store is not going to work. Or, at least, it'll work until it doesn't, often in a spectacular manner. And it isn't really about the dimensions of the oak.

This Question has prompted discussion about other similar sorts of equipment, but the fact is most gymnastics equipment using lengths of "wood" are neither wood anymore, and don't operate like simple pull-up bars. There are pages of specs for gymnastic equipment that uses bars or poles around flexibility and allowance of movement without falling off. They are not intended to be stiff, and consequently any comparison for simple pull-up bars is not helpful.

On the face of it, maybe being able to select the right dowel created from the right lumber might work, but random dowels machine formed from whatever "oak" has been sourced at competitive prices should not be used for workout equipment meant to support ~100kg dynamic loads (or more; we probably want to design for 50% or more past our expected load).

Stiff and strong means a sudden failure mode, which would be very unpleasant. The main reason is that no one has taken the time to machine the dowel from relatively straight and tight grain without voids or minimizing edge-grain leading to the circumference. These are all failure points.

Think of how wood is used in typical spans. Either we are using nearly entire trunks (in rustic builds) that take advantage of how the tree itself is reasonably strong, or we cut dimension lumber from that (in a variety of ways that can maximize yield or strength) and use it in a manner that minimizes these sorts of failures. If you have access to a reasonably strong and straight pole of hardwood (i.e., not a dowel cut from some cross-section of commercial timber) then maybe you could trust the bar. The comment about how baseball bats are created from wood (and noting which side the label is printed on the bat) is telling us that for some uses wood has to be hand-selected and hand-finished, and has to have force applied to it in the right way.

Wood is a great building material, but carpentry is about working within its natural limitations and designing for its strengths. A pull-up bar with commercially available dowels does neither.

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I don't know how to calculate it, but it passes the sniff test when compared to parallel bars used in gymnastics: These are made of (unspecified) wood, are 11.5ft long and 2 inches thick. They are of course made to support people who weigh more than 200lbs, doing very dynamic movements (literally jumping off of the bar and landing back on it. There are of course two of them but gymnasts often support themselves on one bar along.

Oak (any type as far as I can see) is among the stronger wood species for bending/break resistance like this.

The other thing I could think to compare it to is a longbow. The plans on the page linked say to start with a piece of hickory 1" thick and 1.5" wide, with the bending force in the 1" direction (though the maximum thickness will only be kept in the centre of the bow, at the grip - the ends will be tapered down significantly. Obviously hickory is more flexible and the purpose of this is very different, but it gives you some idea by comparison of the strength and rigidity.

Basically, I think you'll be fine, so long as it's a piece clear of any splits, shakes, knots etc and the bearing portions of the dowel are designed correctly.

Edit: Now with testing! It turns out I have a piece of dowel which is about the right size. It's 31mm diameter (so a little under 1-1/4"), appears to be beech (which according to figures I can find is very similar in strength to red oak), and is 675mm long (25-1/2"). I currently weigh about 198lbs, and I just tried supporting the dowel on two 2x4s and jumping on to the middle, with a single heel, as hard as I can.

The dowel: Dowel

The setup: Setup

The test (click through for video on Imgur - couldn't embed here as it's too large).

From this testing I can tell you with some confidence that with a sound dowel with good grain, you have absolutely no chance of breaking it by using it how you're describing.

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  • "Official" uneven parallels are 4cm diameter, actually. There are older DIY plans for making your own that specify hickory. I'm pretty sure the companies that make the official equipment use multiple components, not just 2.4m of wooden poles. The spec just says they have to have a "natural" wood finish. That is, both even and uneven bars will have a core of some material, and wood is used to cover all of that, or only the tops for even bars.
    – jdv
    Jun 2 at 18:18
  • FWIW this page on SFGate although it can't be taken as definitive (other entries on the site are flawed) states that uneven bars used to be made from red oak, but, with a core of steel. And goes on to say they are now made from composites which other sources online support.
    – Graphus
    Jun 2 at 20:54
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    You might want to edit that third sentence — I'd be shocked if you can find any male gymnast who even weighs close to 200 much less more! Male gymnasts are typically short, like Alan Ladd short (5' 5" or thereabouts). To weight more than 200lb they'd have to be even bigger than Franco Columbu who was ~185 when in competition shape (and incidentally also five-five).
    – Graphus
    Jun 2 at 21:16
  • I weigh ~200lbs and I've used parallel bars, including just hanging/bouncing etc. off of a single bar... didn't break them - there was nothing to indicate they were at all close to breaking. There were also guys bigger than me using them when I was at the gymnastics gym. Granted most gymnasts are under 200lbs but the bars have a fairly significant safety factor built in.
    – WhatEvil
    Jun 4 at 21:23

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