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Thread: "turntable"/bearing for rotating diffraction (line) mirrors?

  1. #1
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    Default "turntable"/bearing for rotating diffraction (line) mirrors?

    Hi all

    One issue I've been having recently is that when using LINE diffraction mirrors mounted on holders around venues there's no easy way to align the mirrors in terms of the rotation. The holder is fine for the "up/down, left/right" alignment but with a diffraction grating mirror you really need to be able to rotate the grid so that you get the correct visual effect.

    Typically with a LINE grid I want to align the grid so that the lines are in the horizontal plane. This is because I use them around the venue to simulate additional projectors when doing a "laser grid" kind of effect above the crowd. It's important to get pretty decent alignment when doing this.

    Does anyone know of a suitable tool or method for aligning the mirrors? Currently I use velco (!) and pretty much just get it roughly correct and then stick it on and try to make final adjustments by twisting the holder a bit. This is OK but a bit fiddly and slow. Plus I always worry that the force needed to pull the mirror from the holder will break it.

    I was thinking of some kind of simple bearing thing. You glue the bearing to the holder and the mirror to the bearing then you can just rotate the mirror whenever you like.
    I suppose I could get some circular metal discs made up and fit a countersunk bolt through the middle and into the existing holder with a spring washer and nylock nut but was wondering if anyone knew of something ready-made first before I start messing about with the DIY route?

    Cheers,
    John

  2. #2
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    Sounds like you want a ball-head mount, commonly used for still and video cameras on tripods. Lots of different implementations available... cellphone car mounts often have these as well. You get x, y, and rotation thanks to the ball.

  3. #3
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    If you don't want to actually motor drive the bearing, woodworkers use low cost "lazy susan" bearings for slow rotation. You will need to add a clamp to the LS to fix it in place.. My experience with LS bearings indicates if you actually want to power the bearing to spin during a show you are better off with something smoother. The bearing is stamped out of steel sheet, its not high quality. For a fixed grating you'll be happy with a small one.



    Steve
    Last edited by mixedgas; 10-09-2014 at 08:43.
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  4. #4
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    Quote Originally Posted by tribble View Post
    Sounds like you want a ball-head mount, commonly used for still and video cameras on tripods. Lots of different implementations available... cellphone car mounts often have these as well. You get x, y, and rotation thanks to the ball.
    Yep that could work. The problem is finding something that's the right kind of size and not "consumer grade crap". I'll have a look around and see what I can find. Might even find something that could replace the entire holder... So the base would attach to a standard half-coupler etc. and the movable section would hold the mirror. Would be very handy!

    Quote Originally Posted by mixedgas View Post
    If you don't want to actually motor drive the bearing, woodworkers use low cost "lazy susan" bearings for slow rotation. You will need to add a clamp to the LS to fix it in place.. My experience with LS bearings indicates if you actually want to power the bearing to spin during a show you are better off with something smoother. The bearing is stamped out of steel sheet, its not high quality.
    Ahhhhhh that looks like exactly what I need.
    Now I at least know what to type into Google/eBay!
    Thanks!

  5. #5
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    " 15 characters"
    Last edited by Laser Wizardry; 11-13-2015 at 12:21.

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