According to the AMO (Archery Manufacturers Organization) Standard,
the shaft deflection is measure in inches with shaft supported on 26"
centers and depressed with a two-pound weight. You should be able to
rig something up w/ your gauge. I've attached the AMO chart that
matches the deflection w/ the spine weight.
William of Mann
----- Original Message -----
From: Cian of Storvik <firespiter@...>
Date: Friday, January 12, 2007 8:49 am
Subject: [SCA-Archery] Spine tester
> Does anyone have a plan to make an instrument to measure spine
> I keep getting tempted to buy a spine tester. But the least
> expensive one is almost $100.00. I have an out of round gauge
> and base. And I figure it's just a matter of putting two dowels in
> board and mounting the mic on it.
> The cheap spine tester I've seen looks like it's 2 horizontal
> that the arrow sits in. The first dowel; the arrow rests
> just behind the pile. The second dowel appears to have the arrow
> resting on top of it near the center-point of the arrow, and a
> weight hangs off of the nock side making the arrow deflect, which
> then measured with a compass gauge.
> What weight is placed on the arrow and at what distance? I believe
> that spine = the compression force at which the arrow will deflect
> 1". But how much deflection is this when using an ounce
> to apply lateral force?
> In a related question, how much does a finish like tongue oil
> the spine weight of the arrow? I usually buy arrows "pre-spined"
> wonder how much 3 or 4 liberal coats of tongue oil affects the
> spine. (which is why I am interested in the spine tester to begin
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