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Unistrut Expansion Mounting

I am having an issue with my top bar shrinking. It is a 10 foot long 2x6. It has shrunk about 6 mm so far. It was green wood, not kiln dried (I can’t find KD 2x6s in my area) so this isn’t a complete surprise. Some of this movement may be a one time thing as the wood dries, but some of it is likely to be seasonal.

I would like to get a stable platform and avoid running the calibration process again, so I was thinking of moving to a unistrut top bar. Something like this Unistrut Design, but I don’t want to replace my entire frame.

If I use unistrut as my top bar, I still have to affix it to the wood that is moving. Does anyone know of any expansion mounting that exists for unistrut?

unistrut has nice large holes you can use to mount it

you can also get unistrut L brackets and use short lengths of unistrut for your
forward arms and make the distance away from the backer adjustable.

David Lang

Even if the wood moves it wont’ affect the calibration since the unistrut will keep the motors at the same distance from each other. Unless you need to place projects with in a couple of mm of the edges,the realative movement of the wood wont’ make a difference

I think you are all right.

I was planning on using L brackets attached to the wood which then attached to the unistrut bar that the motors are directly mounted on.

My concern was that movement in the wood could cause the unistrut to bow. The distance between the motors would be constant along the bow, but could be less in a straight line.

As I have thought about it more, I have decided that if that were the case, the weakest link is actually the L bracket and all of its connections, and rather than the unistrut bowing, the L bracket would likely just rotate slightly in the horizontal plane.

Thanks for the help thinking this through.