spine tester?

[ks_stickbow]

I am making a spine tester as shown on Jim Hill's page (http://www.jamesmhill.com/Spine_Tester.html).

my question about the weight used. 2 lbs seems like a lot of weight. If I use a 1 lb weight do I just cut the deflection chart in half. So according to Jim's chart .232 is a spine of 112 lbs. he is using a 2 lb weight. if I use a 1 lb weight does that mean it's not 112 but rather 56 (half of 112)?

[fyrfyter43]

I'm building the same spine tester...in fact, I'm just about done with it.

The 2 lb. weight is not a problem, but if you really wanted to use a 1 lb. weight, it should work out the way you explained it. Probably the easiest thing to do is try it out with a few arrows with known spine.

[Bjorn]

Probably true but not nearly as accurate; you need the weight to get the shaft bending sufficiently for a good reading. And 2 pounds is a bit of a standard too for what ever that's worth. Don't forget that even a crooked shaft can give you an inaccurate reading.

[ks_stickbow]

problem is I have no know spined shafts....LMAO.....I know hard to believe....problem is my digital scale only goes up to 1 lb. and I have a perfect one pound weight...guess I can go to the post office and have them weight for me

[TexMex]

http://homepage.ntlworld.com/joetapley/

[Bjorn]

I sold my home made tester by the way......it was OK but not nearly as nice, accurate, or user friendly as the one I bought from cupcake!
There is another thread on the page right now about it. Check it out.

[TexMex]

http://homepage.ntlworld.com/joetapley/

[Cupcake]

Jeff,
If you can make accurate 1lb. weights just make two and hook them together somehow.  If you have aluminum shafts for known standards just multiply the manufacturers deflection by .825 and that will be the deflection with 2lbs. at 26 inches.
Kevin

[foudarme]

does someone has the spine correspondance between 0 and 0.170 deflection (it lacks on my ACE spine tester)...I have spine tested my grizzly safaris and got a .125 deflection and would like to know what is the spine for that...

[fyrfyter43]

Spine = 26/deflection

So at 0.125" deflection, that would be a spine of 208#.   :eek:  

This is assuming a 2 lb. weight, hung in the center of an arrow supported at 26".

[foudarme]

Originally posted by fyrfyter43:
Spine = 26/deflection

So at 0.125" deflection, that would be a spine of 208#.     :eek:    

This is assuming a 2 lb. weight, hung in the center of an arrow supported at 26".

I have another friend who find exactly the same deflection with another spine tester on those shafts..
thanks for this rule (26/deflection) I ignored it...