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spine tester plans

12K views 11 replies 5 participants last post by  Nick 
#1 ·
#2 ·
Thank you!!!! I really like that first one, very simple to construct, set up and operate. I think I'll turn the bolt down to a polished rounded point where it contacts the arrow shaft.
Are his tables considered accurate?
How do Spine/deflection numbers correlate?
I note that the Easton Redlines I purchased recently are marked .410, Is that a deflection number? do the coding numbers on the ACC shafts indicate spine rating?

the other DWS
 
#3 ·
yeah thats the deflection in .xxx of an inch on the redlines. im pretty sure the accs have a spine rating on them as well. the 3-29 etc is not a spine indication. the "3" is the wraps of carbon that is on the shaft the '29' (in this case) is the diameter of the diameter of the aluminum core tube , in thousandths of an inch,e.g. 29= 0.229 or 39=0.239 or 49=0.249.

just know that easton and most modern arrow manufactures obtain their deflection measurements with an 880gm (apx 2lb) weight that is placed in the middle of a shaft that is on 28" centers and most trad shafting is measured on 26" centers.

it really doesnt matter how you calibrate your tester--just that you can consistantly match arrows. i would recommend using an easton aluminum of known deflection then you can calibrate off of that.

the weight you use also doesnt matter unless you are trying to obtain identical results with an exisiting tester. does that make sense?

ill try and find some charts to see what deflection corresponds with what poundage of bow. just remember there are a lot of variables--degree of center shot, draw length, point weight, bow efficiency(which relates to string type), release, and so on.

the best use of a spine tester is to match arrows once a suitable arrow is found. you know.. say you have a bunch of woodies and 3 of them fly great--just throw these on your tester and then match to the good shafts.
 
#4 ·
I'll make a defletion gauge when I get back off the road this week. It seemeth to me that deflection is a more precise measurement that spine ratings. I figure that if I can get a standardized deflection (2# weight, 28" centers) figure for these older shafts sizes, anyone can figure what deflection works best on their bows and see if there is a matchup.
Do you think that the final 3 numbers on the Easton ACC shafts 304-680, 3L-750, 3-18-560, 3-18-620, and PC 5.0-830,5.4-630, 5.5-550 etc are deflection numbers. Nah, they wouldn't make it that easy for us now, would they?
 
#10 ·
I built one of the spine testers using a dial indiactor. In order to calibrate it I re-set the rests at 28" and used and Easton 1816 shaft. In order to get a .756" deflection (Easton spec for this shaft) I had to add 3 3/4 oz of wt to the 2# weight to overcome the spring tension in the dial indiator. I found that it would take about 1/2 oz wt to start the dial indicator to move and the weight requirement would increase as the indicator was depressed more. I also found that taping the arrow would vary the reading up to .040".

I plan on re-doing the spine tester and eliminating the dial indiactor. I will use the dial indicator to calibrate the scale and hopefully will then have and accurate spine stester.
 
#11 ·
TTT for phil.


nick commented that the dial indicator he was using would give skewed readings because of the spring tension in the dial indicator itself.

to remedy this simply hang the weight and let the arrow flex, then depress the indicator arm and let it "raise up" to meet the arrow. no problems with spring tension that way.

hope that helps.

good shooting,
ryan b.
 
#12 ·
That's the way I do it now. I reset my wt back to 2#. I place the arrow in place and with my fingers carefully depress the stem on the dial indicator untill it barely touches the shaft. I them zero the indiactor and the add the weight. I then again depress the stem of the indiactor until it barely touches the shaft. Now and accurate reading.
 
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