Wow. I had no idea so many people would PM about this. So I figured I would just start a new thread. I'm going to attempt some pics, I hope they come out.
You will need:
1. Three 8" metal shelf brackets.
2. Two pieces of wood, one for the base at least 26" long by 5" inches wide ( longer than 26" is ok ) and one 9" long by 1 1/2" wide to mount your protractor and zero indicator on.
3. A protractor. A 360 degree one is best but a 180 will also work. I took two 180s and taped them together.
4. A strip of card board or plastic 9" long by 1/2" wide. This is the white strip behind the protractor in my pic. I used plastic, but strip of cardboard will work well if you cant find plastic. This strip will be your zeroing indicator.
5. a roofing nail
The shaft supports are the 8" shelf brackets from the local hardware store. Take a hacksaw and saw the top screwholes in half on two of them, making a groove on each one for the arrow shaft to sit in. You may have to smooth these out with a round file later on. Mount these on your board with the slots you just sawed exactly 26" apart, facing each other and even with the edge of the board. pics...
http://i99.photobucket.com/albums/l282/poekoelan/IMGP0111.jpg http://i99.photobucket.com/albums/l282/poekoelan/IMGP0113.jpg Now get a protractor and drill out the center hole a little at a time to prevent cracking. Make the hole big enough for a 1" wood screw. It should be a loose fit. You want the protractor to be able to move freely on the screw. Now exactly one inch to the left of the center of that hole, drill another small hole big enough for a roofing nail to fit through. Put your roofing nail through it and glue in place. This is the arm that your arrow will rest against when the weight is applied.
Now get your piece of cardboard or plastic. Draw a vertical line down the center of it and make a hole on the center of that line 3" down from the top. pic...
http://i99.photobucket.com/albums/l282/poekoelan/IMGP0120.jpg Now get your 1 1/2 by 9 peice of wood. Measure down 2" from the top and drill a hole in its center. take your protractor and put the 1" wood screw through the hole in it's center. Put your strip of cardboard or plastic on the screw behind the protractor and screw this screw in the hole you just drilled on your piece of wood. Again, the screw should be loose enough to allow the protractor and the zero indicator to spin freely. I put a large washer between the head of the screw and the protractor but I don't think it's absolutely neccessary. Tape a dime on the far right of your protractor. This is a counterweight to make sure the roofing nail will be resting against the bottom of your arrow shaft. pic...
http://i99.photobucket.com/albums/l282/poekoelan/IMGP0121.jpg Now mount this contraption to your base board, three inches from the back edge of the board. IMPORTANT....the roofing nail has to be exactly 13" from each of your shaft supports. I used a third shelf support mounted to the back of the 1 1/2x9 piece of wood to accomplish this and I sawed off the over hang. pics...
http://i99.photobucket.com/albums/l282/poekoelan/IMGP0122.jpg http://i99.photobucket.com/albums/l282/poekoelan/IMGP0123.jpg To make my two pound weight, I got two pounds worth of split shot sinkers and melted them in a tuna can. After it cooled overnight, I cut the can away with tin snips and put a small screw hook in it. I took it to the post office to have it weighed. An exact two pounds is important to the accuracy of the spine tester.
To use this: put an arrow shaft on the on the slots you sawed on the brackets. The roofing nail should be touching the the bottom of your shaft. With your right hand, move the cardboard or plastic so that the line down the center of it is even with a degree mark on your protractor. I usually line mine up on the 70 degree mark. Hold the the strip in place at your chosen degree mark with your right hand, and with your left hand, place the two pound weight on your shaft to the left of the roofing nail, as close as possbile to the nail. Your zero indicator will now be at some other degree mark to right of the one you lined up on. Now you just have to know how to read this thing. Here is the chart:
30/35lbs = 60 to 48 dgrs
35/40lbs = 48 to 40.5 dgrs
40/45lbs = 40.5 to 35.25 dgrs
45/50lbs = 35.25 to 31.25 dgrs
50/55lbs = 31.25 to 28.25 dgrs
55/60lbs = 28.25 to 25.75 dgrs
60/65lbs = 25.75 to 23.5 dgrs
65/70lbs = 23.5 to 21.75 dgrs
70/75lbs = 21.75 to 20.25 dgrs
75/80lbs = 20.25 to 19 dgrs
80/85lbs = 19 to 17.75 dgrs
85/90lbs = 17.75 to 16.75 dgrs
90/95lbs = 16.75 to 16 dgrs
95/100lbs = 16 to 15 dgrs
Let's say you held the line on your zero indicator at 70dgrs. After you placed your weight on the shaft and moved the protractor, the line on your zero indicator was now at 99.5 dgrs. That's a difference of 29.5 dgrs. That puts this arrow in the 50/55 spine group. I taped this chart to the base of my spine tester.
If you have any questions feel free to email me at
[email protected] Be sure to put "spine tester" in the subject line as I delete a lot of mail without looking at it.
Topic: cheap, easy , accurate spine tester (Read 1498 times)
