Texas Star Build

[hp246]

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.

[Fast Leroy]

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.

[hp246]

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.

[hp246]

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

[SlowBlues]

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

[Broccoli1]

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.

[Broccoli1]

Crap- my bad.

Only makes a 6 point star

[droktharr]

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) )

[Fast Leroy]

Here you go...

[Broccoli1]

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.






Attachment 1705717

[torres14073]

Fusion 360 is a cad program that can help you design anything before making it.


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