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jguy

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Posts: 79

Location: United States Conyers, Georgia
Occupation: computer programmer
Age: 64
#1   2013-09-14 03:56          
Our forge item for this month is a traditional triangle dinner bell. There is a lot of information available for working backwards from the desired note to the size of material.

There's also conflicting information out there: tight bends are better, loose bends are better . . .
One interesting point is to hang it from a point 22.4% of the length to maximize the sound (that would be: multiply it's length by 0.224 and bend it there). That's worth experimenting with!

Here's two of the more interesting sites that I found: Please let me know what you find out that works out of all the confusing things out there!

anvilfire discussion (click here)
website on designing wind chimes (click here)
Jim Guy

cal

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Posts: 134

Location: United States Sharpsburg, GA
Occupation: Retired Programer
Age: 70
#2   2013-09-14 11:35          
I made one today out of 1/2 rebar. It looks pretty good and does have a fair sound. One thing I did discover is that if I hang it from a steel ring it tends to deaden the sound. Too bad really cause I went to the trouble to make a ring I even got it to forge weld the joint on the 1st try. When I hang it from a string it rings lots better.

Added 4 minutes later:

One other thing I did was to quench the three corners. I don't know if it makes a difference or not but I'm thinking the harder the steel the more it will vibrate and since it is rebar it is likely that it has a fair amount of carbon in it.
Cal Kohler

dan tull

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Posts: 66

Location: United States
Occupation: blacksmith,full time
Age: 75
#3   2013-09-15 11:47          
Or next to none.

Dietrich Hoecht

us
Posts: 51

Location: United States Clayton, GA
Occupation: piddles in metal, roams the woods
Age: 78
#4   2013-09-17 05:02          
I had never thought much about the geometry, but now it all makes sense. The bend and suspension points are located where the zero nodes of a freely vibrating beam are. That should also lead to the answer of tight vs. larger bend. A larger bend zone sort of restricts the vibration at both sides of the zero node. I knew about the 0.22 factor before. So, when I have a stack of newly cut wooden boards I place two supports at 0.22 times length from the end. That way the natural deflection is identical at both ends and at the center, and the wood dries fairly straight.
Cal's point of the ring not working well: I think there are two issues. One, he may not have it located at the zero point. The other, if it is off the zero point there is vibratory movement at the ring support point, and the friction dampens the motion. A string has less dampening effect.
Personally, I'd harden the whole thing. Drop a hardened chisel on the floor vs. a soft iron one. The chisel rings.
Dietrich
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