Texas Star Build
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  1. #1
    Join Date
    Apr 2009
    Posts
    173

    Texas Star Build

    Hoping someone can help me out with some math. I'm building a Texas Star (Range Target) with five pedals that swing on arms. I am using 90 degree angle iron to protect the arms. I want to join the five pieces of angle iron and weld them together at the tips. They need to be cut and positioned so if the angle is up (opening flat), five pieces of angle iron join and can be welded up without overlap. My first thought was pentagram, so I cut out five pentagrams, folded them at 90 degrees and put them together. I can only fit three together. Help. Math was not my strong point.

  2. #2
    Join Date
    Sep 2011
    Location
    Jasper TX
    Posts
    1,471

    Re: Texas Star Build

    I know the tips of a 5 pointed star are 72° apart from each other. So draw a circle and place the first point at the very top, 360°. Then place each point after that 72° from the last point.
    Owner of Fast Leroy's Bar and Grill
    Liquor up Front, Poker in the Rear

  3. #3
    Join Date
    Apr 2009
    Posts
    173

    Re: Texas Star Build

    Quote Originally Posted by Fast Leroy View Post
    I know the tips of a 5 pointed star are 72° apart from each other. So draw a circle and place the first point at the very top, 360°. Then place each point after that 72° from the last point.
    Yep. I got to thinking about this after I posted. Really talking about a 360 circle. So if I make each side of the angle iron 36 degrees, give me 72 degrees per point times 5. Gonna cut it out and make sure it works tonight.

  4. #4
    Join Date
    Apr 2009
    Posts
    173

    Re: Texas Star Build

    Did a layout using paper. 72 degrees did not work. The 90 angle threw everything off.

  5. #5
    Join Date
    Dec 2018
    Location
    Southern California
    Posts
    630

    Re: Texas Star Build

    Using the angle iron adds a third dimension and changes all the angles as the center point falls on one plane and the corners on another. Can't use simple "circle" math, and must take height into account which changes every angle.

    First draw 3 lines at 36 degrees radiating from a center point (1 center lines for the star and 2 for the bisecting line for the legs), lay the angle iron down with the corner on the center point following one line and mark where the two adjacent radiating lines intersect the edge, Cut line will be from point on leg to tip of the corner. Rinse and repeat 5 times and they should fit pretty well. If the angle iron is thicker you will want to think about the edge (cut) angle of as well.

    Paper mockups in this case will be difficult, corner bead for drywall (or any cheap angle iron shaped material) is a good option, plastic or metal available at any hardware store cheaply.

    Sorry had to look over my notes and had the technique wrong! edited for that reason
    Last edited by SlowBlues; 09-18-2019 at 03:30 PM. Reason: Looked over my notes and had it wrong!

  6. #6
    Join Date
    Dec 2007
    Location
    Los Angeles
    Posts
    7,657

    Re: Texas Star Build

    Compound miter cut is needed. Same as cutting molding angles in wood.

    paper will work for this.

    print out a star and then cut out one of the points. Fold over and place on the angle iron. Trace the angle on both legs of the Angle iron.

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    Ed Conley
    http://www.screamingbroccoli.com/
    MM252
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  7. #7
    Join Date
    Dec 2007
    Location
    Los Angeles
    Posts
    7,657

    Re: Texas Star Build

    Crap- my bad.

    Only makes a 6 point starName:  IMG_2870.jpg
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    Ed Conley
    http://www.screamingbroccoli.com/
    MM252
    MM211 (Sold)
    Passport Plus & Spool gun
    Lincoln SP135 Plus- (Gone to a good home)
    Miller 125c Plasma 120v
    SO 2020 bender
    Beer in the fridge

  8. #8

    Re: Texas Star Build

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    Since CAD is cheating, you can also do the math in 3 planes (top, front, side plane) and use trigonometry and right triangles.
    You will eventually end up with arctan( sqrt(2)/tan((180-72)/2) )
    Last edited by droktharr; 09-24-2019 at 08:41 PM.

  9. #9
    Join Date
    Sep 2011
    Location
    Jasper TX
    Posts
    1,471

    Re: Texas Star Build

    Here you go...

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    Owner of Fast Leroy's Bar and Grill
    Liquor up Front, Poker in the Rear

  10. #10
    Join Date
    Dec 2007
    Location
    Los Angeles
    Posts
    7,657

    Re: Texas Star Build

    that is to draw one.

    To make it 3-d the angle iron can not be 90 degree.

    Cardboard kept springing back towards 90 so I had to hold it down for the demo.

    ** these are the same pieces used when I had the "iron angle" at 90 degree. No new angle cuts made- just spread out the angle past 90 degree.


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    Last edited by Broccoli1; 09-25-2019 at 04:59 PM.
    Ed Conley
    http://www.screamingbroccoli.com/
    MM252
    MM211 (Sold)
    Passport Plus & Spool gun
    Lincoln SP135 Plus- (Gone to a good home)
    Miller 125c Plasma 120v
    SO 2020 bender
    Beer in the fridge

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