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Main Boards => PowWow => Topic started by: Wheels2 on March 19, 2014, 10:43:00 AM

Title: Specs for DIY spine tester?
Post by: Wheels2 on March 19, 2014, 10:43:00 AM
I am looking at building my own spine tester.
How far apart should I make the blocks?  26" or 28"
What weight is correct for each span distance?
What is the formula for converting a digital reading to poundage?  (.500 + ?#)

Thanks,
Title: Re: Specs for DIY spine tester?
Post by: Matty on March 19, 2014, 11:49:00 AM
Do a google search. There's quite a few good builds out there.
I think there may be one in our "how to" section take a peek there. Either way to answer your question.
26" and 2#
Title: Re: Specs for DIY spine tester?
Post by: Wheels2 on March 19, 2014, 06:44:00 PM
I got the answer on another sight.  Based on the calculation equasion, the 26" span and 2# weight is the way to go.
The 28" span and 1.94# requires constant reference to a chart as the math is not as neat and I have yet to identify the required constant.
Title: Re: Specs for DIY spine tester?
Post by: Stumpkiller on March 19, 2014, 09:21:00 PM
I built mine into the edge of a shelf over one of my workbenchs with two dowels 26" apart and a 2# weight.

 (http://img.photobucket.com/albums/v169/Stumpkiller/Bowhunting/HPIM2043.jpg)

 (http://img.photobucket.com/albums/v169/Stumpkiller/Bowhunting/HPIM2040.jpg)

 (http://img.photobucket.com/albums/v169/Stumpkiller/Bowhunting/HPIM2047.jpg)

Rose City has a chart you can download with the AMO deflections.

 (http://img.photobucket.com/albums/v169/Stumpkiller/Bowhunting/AMOSpineDeflectionChart_zps19c2c59e.jpg)
Title: Re: Specs for DIY spine tester?
Post by: Fletcher on March 19, 2014, 10:01:00 PM
The chart above is the easy way to go to convert deflection to spine.  The formula is: 26 divided by the deflection in inches = spine.  Example, 26/.500=52#
Title: Re: Specs for DIY spine tester?
Post by: BAPilot2 on March 19, 2014, 11:54:00 PM
Stumpkiller,

Cool idea!!!  I may have to steal that one and call it my own!
Nice set up.
Title: Re: Specs for DIY spine tester?
Post by: chall on March 20, 2014, 08:02:00 AM
Good info thanks for the post