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I made a wood balance beam for my daughter out of a fir 4x4 and some compression joints. Which direction should the grain be? Should the grain run parallel or perpendicular to the top of the beam?

  • By compression joint, do you mean a plumbing fitting to attach a supporting iron pipe to the beam? or are you meaning a woodworking joint of some type? – scanny Dec 5 '16 at 4:20
  • The textbook answer is vertical, but since it's extremely likely that your fir 4x4 is not quartersawn wood (with grain lines running parallel or nearly parallel to two sides) it won't neatly fit into that recommendation. We really need to see a photo of the wood to advise appropriately — both end grain surfaces, and some shots of the length wouldn't hurt to check for runout. – Graphus Dec 5 '16 at 9:42
  • @scanny maybe there's a different word for it. I mean the woodworking joint that's like a dado slightly too small, so the joint is held together by it's own tightness. – Scribblemacher Dec 5 '16 at 10:40
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You want the grain/growth lines to be oriented vertically to maximize strength. Most 4x4 posts will have curved annual growth lines. Choose the orientation that is most vertical. As a caution, note that professional balance beams are made from laminated wood and are much deeper than the 3 1/2" in a 4x4 post. If your daughter is going to do any gymnastics on the beam a pine 4x4 may not be rigid enough especially if you make it any longer than 8'.

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  • She's 3 years old, so she's using it to play and practice balancing. This is low to the ground, which is just right for her size. If she were doing something more trying, you are right, I'd need to re-think this design. – Scribblemacher Dec 5 '16 at 10:32
  • @Scribblemacher If she's only 3 I don't think you need to worry about strength. Even a 4x4 with poor grain structure is going to be more than strong enough for anything she can throw at it. I'm over 100kg (220lb) and I've stood on pallet-size lengths of 1x4s (on edge) that deflected barely enough to notice! – Graphus Dec 5 '16 at 11:11
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    @Graphus Oh, I'm not worried about my 28 lb kid breaking it. This question was to improve my knowledge so I make the correct decision when it does matter. – Scribblemacher Dec 5 '16 at 12:29

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