Main Discussion Area > Arrows
New Spine Tester
recurve shooter:
mr. keith, is yer link one of them new invisible ones?
Pat B:
Piper, Here is my version of a James Hill spine tester, also made with scrap wood. As per Art Butner I used a large diameter bolt for the weight. As you can see it pushes down through eye bolts rather than pulls down like a suspended weight. I'm not sure if the direction of deflection matters or not. ::) Also from Art, the adjustable upright. The one on the right has a slot in the wood where the bolt goes through and a wing nut for quick adjustment. I think I got my dial indicator from Grizzly.
The drop bolt weight has a copper plumbing sweat fitting forced over the hex head with lead added inside to make up the 2#. I weighed the components using lead shot until I had the 2# then melted the lead shot and poured it into the copper fitting.
I used skateboard bearings for the arrow shaft to rest on when spine testing.
I also have a suspended weight that I use. It is a small metal PVC pipe cleaner can with a cup hook in the lid. I added lead shot to it to make up the 2#.
islandpiper:
http://www.jamesmhill.com/Spine_Tester.html
Pat B:
I guess the bolt was Hill's idea. ;D I couldn't get enough washers on my bolt to make weight so I went with the copper fitting and lead shot. Actually having the bolt come down directly over the dial indicator would give a more accurate reading than a weight that is hung off center.
possum:
I have one similar to Pat's although I went the washers on the bolt route. As far as adjustable I put two wood screws in the notches where the arrow rests, on both sides. Also, because I spine unstraightened bamboo shafts I have the dial indicater on a swinging arm kinda thing in case the shaft bows out I can still move the indicator under the shaft to get a truer reading.
possum
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