Primitive Archer
Main Discussion Area => Arrows => Topic started by: D. Tiller on August 15, 2006, 12:09:29 am
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Anyone know how to make a home made spine checking tool and how to go about making one?
D. Tiller
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I have one that uses a dial indicator that was very simple to make. Send me an e-mail or PM and I'll send you a pic. Basically it's a board with two uprights, 28" apart and the dial indicator in the middle, and with a 2# weight suppended in the middle the deflection is measured in thousanths(.00) and compared with a chart that gives the spine weight. Pat
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Pat, wasn't there a web site and article showing how to do this with the dial indicator?
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The website you are talking about is: http://www.jamesmhill.com/spine_tester.html
I'll have to scan ta pic of the one Art Butner made. It is simular to Hill's but done with more wood and easier for me to make. I'll get it scanned in a bit and post a pic. I'll also scan and post the deflection chart that goes with it. Pat
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Someone send me an e-mail address so I can e-mail this to you. I can't get it to come up as an attachment. Pat marciaandpat@citcom.net
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on that site it says the distance between them is 26 inches and you guys say you measure spine at 28 ????
im confused ???
Brandon
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Brandon, I have mine set up at 28". That's the way I was tought. Pat
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Let's see if this works. Pat
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Well, I sure can't post decent pics. Maybe the one I sent to Justin came out better. Pat
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Lets try this Pat. I cut and deleted all the non pertinant info from the page then resized. Here is Pats spine tester. Justin
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Thanks Justin, Actually that's Art's spine tester but mine is a poor copy of his.
Here is a link to Art's discussion and pics of his tested:
http://primitivearcher.com/dc/dcboard.php?az=show_topic&forum=7&topic_id=14679&m
Boy I hope that's right. I just got writers cramps in my hand...and my brain. lol
Pat
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That spiner has wheels on the end where the arrow sets so it should double as a arrow spinner or a hand spun crester. Save us all a lot of space. Justin
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Justin, I got my roller bearings from a skateboard shop for only a few dollars. They work very well for this application. Pat
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i have mine set up to 26 inches and on his site he constantly says 26 inches ??? should i change it to 28???
Thanks Brandon
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Brandon, Those 2" will make a heck of a differance. Test a arrow with a known spine and adjust your spine chart to that. I'm not an expert on this. I just go by what was told to me. Pat
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i guesse i have to make a trip to my archery shop then i only have shafts ive made and shafts ive been givin ...have no clue to the spine of any of them...
Thanks Brandon
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on that site it says the distance between them is 26 inches and you guys say you measure spine at 28 ????
im confused ???
Brandon
Well the standard length for shafts is 28 inches, so most commercial spine testers are set up at 28 inches. If you shoot a 31 inch arrow though, your spine you get on your spine tester will actually be 15 pounds heavy because of the extra flexibility the longer shaft gives you. (5 pounds an inch) If you shoot 31 inch shafts then I would set it up at 31 inches. If you are making shorter shafts then I would set it up at the actual length so you can get the most accurate spine reading that you can. This is just me though, other people may like to stick to the standard 28.
Matt
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I have been contemplating this since I saw that site with the 26" spine tester. I think I would change it to 28 if its not to much work. Even a 26 inch draw would have a 28 inch arrow because you dont want to draw a broadhead to the back of the bow. Its probably not a huge deal on parallel shafting but if you get into tapered or barrel shafts the center will be stronger than the end. So the more shaft you get between the posts the better. Justin
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how would i convert the spine tester to the 28 inch ...because there is a whole chart i would have to do so would i switch the 26 to 28 (or what ever length) in the equation to get the proper delfection for the right spine???
Brandon
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A spine tester is set up for 28". If your arrow is 31" it will still spine the same but when you shoot the arrow it will shoot like an arrow with 15# lighter spine. the extra length( 3") will reduce the arrow spine by 5# per inch over 28". At 31", it in still spineing between the 2 post set at 28" apart.
Now, I'll bet you are really confused!!! LOL Pat
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OHHHH so just move my posts 1 inch farther on either side and it will spine lower but more acurastely????lol i think thats what i have to do...this is the one i have built... http://www.jamesmhill.com/Spine_Tester.html
Thanks Brandon
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I'm a very practical person. I just hang a crescent wrench from one end of a shaft suspended in the center on a nail, and held at the other end similarly. Calibrate using shafting of known deflection. I used aluminum shafting, being careful to place the center consistenty. I haven't found bows to be so sensitive to spine that a couple of pounds one way or the other made any difference.
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Actually your chart might be off by 2# if you switch to 28". You would need a new chart I think. Probably should leave it alone unless you are going to use tapered or barrel shafts. Spine according to Jim is length/deflection. 26/.565=46# subtract 10# for 2 additional inches=36# 28/.777=36# according to the chart .777 deflection =33-34# OR I could be all screwed up... Justin
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Well Pat you didn't confuse me... I know what you mean. If you are going to shoot a 31 inch shaft just make your arrows spine 15 pounds higher... The deflection will still be the same even if the posts are farther apart. If it pulls down .565 then it will still be 50#, the length of the shaft doesn't matter.
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oh i finally get it lol ...ill just make it to 28 considering it will be the same also i will put a piece of dowel on top of the dial indicator to make it so the shaft doesnt need to be PERFECTLY straight...thanks for the help guys...
Brandon
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The deflection will still be the same even if the posts are farther apart. If it pulls down .565 then it will still be 50#, the length of the shaft doesn't matter.
No the deflection will be farther. It will be around .72 which will be 36 #. The 26 deflection was .565 which was 46# but when you compensate for the two inches of extra arrow outside the posts you subtract 10# which makes the true spine 36#. I shoot 31 inch arrows spined at 28 inches so with three extra inches over 28 I have to subtract 15#. Justin
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No what I mean is if you put the posts further apart... If your posts are set at 30 inches and it pulls down .565 then it is a 46# spine. Sorry bout the confusion. ;D
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No the deflection will not be the same. the deflection will be slightly more for posts 28" apart. If your posts are 30 inches apart and it pulls down .565 then you divide 30 by .565, 30/.565=53.09 so the spine is 53-54. If you spine the same arrow with the posts 26 apart the deflection will be around .278, 26/.278=93.5 so 93-94#. But this arrow has 4 more inches so we subtract 40# ending with the same 53-54# as when the posts were 30". The formula is Space between posts divided by deflection. Then you must compensate for other factors such as longer arrows or heavier tips. I'm sorry I confused you. It really is in your best intrest to just use the chart Jim Hill provided and build with the posts 26" apart, unless you are using tapered shafts. Maybe even then the difference will be minimal. Justin
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well heres a chart i made up last night for the 28" posts ... i hope its right...
(http://i16.photobucket.com/albums/b47/mj_23_rocks/Spinechart.jpg)
Brandon
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"PERFECT" ;D ;D ;D Good job That is just what you needed for a 28 inch space between posts. You can see there is only a couple pounds difference but thats the whole point to spining. Justin
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What I was trying to say above was no matter how far apart the posts are, if you set a shaft that is the same as the distance of your posts on there and it pulls down .565 then your spine will be 50#. That shaft will not show the same deflection if you move the posts in, but a completely different shaft of a smaller diameter might show the same deflection and still be the same spine.
In other words a 28" 11/32 POC shaft can theoretically have the same spine as a broomstick, given that the broomstick was long enough to be that flexible. But, cut it shorter and the spine raises. Same as piking a bow. Sorry for the confusion everyone. ::)
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Guys, all this confusion comes from the AMO standards. Bows are usually measured by weight at 28" drawlength, but arrows are spined between 26" centres. As long as you use the same measurement every time for your own personal arrows then you could have it any length you want. The idea of hanging a wrench off the end of the shaft is just as accurate as long as the wrench is place the same distance from the fixed end everytime.
Graham
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Interresting designs and ideas guys! How about just hanging the arrow between two uprights and then suspending a 2# fishing weight from the center and eyeballing it against a white peice of paper behind it. If you have one shaft of a given weight then you can compare the two and you should have a good enogh idea of what the spine is.
D. Tiller
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Unless I missed the explanation for tapered/barrelled shafts? I barrell taper mine...how will that change my setup? I made a maple spinner which I use for shaft straightening that I want to make into a 'spine tester'. I shoot 31" barrelled tapered arrows with a 26" draw length (and yes, I luv'em that way)...so how do I proceed? The other item of consideration is how much your bow/string is aligned to 'true' bow center...I usually make my bows lined up to the left (I'm a right handed shot) so spine hasn't been too much of a problem. I would still like to know and measure...and want to do it right the first time. Any suggestions? Thanks...
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Guys, all this confusion comes from the AMO standards. Bows are usually measured by weight at 28" drawlength, but arrows are spined between 26" centres. As long as you use the same measurement every time for your own personal arrows then you could have it any length you want. The idea of hanging a wrench off the end of the shaft is just as accurate as long as the wrench is place the same distance from the fixed end everytime.
Graham
After you posted this I looked up AMO standards. CONFUSING ??? They can even pervert the draw length and bow length issues. So basically what I understand is that they measure between 26" centers but it is calculated for a 28" arrow.
Primitive: just fallow the instructions on the site Pat posted. Set it up at 26". I shoot arrows several inches longer than my draw length because I don't want the broadhead getting to close to the back of the bow and interfearing. Justin
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I got these plans from another site. They seem to be pretty simple, what you see is the dial face but read through the word doc for how to build the rest of it.
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Was looking at dial indicators over on eBay and realized that I had absolutely no idea what deflection range I needed. Would the shaft flex 1/4" or maybe up to 1 1/2"? I suppose I could take some shafts that were factory spined and get somewhat of an idea. These plans look like what I may have been looking for though and are a lot easier to fit in my budget too !!! Thanks skeaterbait, I sure do appreciate it.
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Jim Hill recomends using 1". I got mine at the local Ace Hardware for about $15. Justin
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I think your going to need at least 1" of deflection , carbon redline 600's that work on a 40+# longbow = .6" deflection . some of the carbons that they make are numbered by their deflection in inches ,600,500,460, 350 and so on. but I think they may be measured at 28"you might want to check either the manufacturer or one of the other archery forums.
If you can borrow some various spine carbons or some known spine woodies that will give you a data point to verify yours.
I was looking for that spine tester scale print out, so thanks for that.
Roger
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Went ahead and built the spine tester that Skeaterbait linked the plans to. Was real easy and did the whole thing for less than 5 bucks !!! Had enough scrap wood laying around the shop so that I didn't have to buy any. Making the 2 pound weight was pretty easy too as I had a bunch of #7 1/2 shot and a reloading scale. Just a matter of weighing the empty container and then weighing out enough shot to bring it up to 2 pounds total. The meat counter at my local grocery store confirmed that it was 2.00 pounds right on the button. The most time consuming part of the whole thing was making up a chart showing the various inches of deflection converted to pounds of spine.... a couple hours quality time spent with a calculator. Not a bad Saturday afternoon project.
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Spent the last hour or two verifying the spine weight of about a hundred cedar shafts.... they were from probably 3 different suppliers, some directly from Rose City itself. They were all represented to be 45# (actually 43# to 48#). It was absolutely amazing to me the variation I encountered.... some as low as 40# and some as high as 57#. I went through the entire pile three times and all of the readings repeated themselves. I've no particular reason to doubt the accuracy of this home-built spine tester as all of the readings made were consistent rather than the same shaft giving 3 different readings. Had a dozen come out at exactly 52 pounds and all weighing within a 5 grain spread. Think I will set those aside for my next set of personal arrows.... have a couple of color combinations that I have been wanting to try anyway.
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I built the Jim Hill model and started testing shafts that I had ordered. They had the weight on them 42, 44, 43 not just a 45 group. My tester measured 2 pounds under on all. Then I tested one that said 57 and it was 75. OOPS somebody is dyslexic. Justin
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Like bows, wood arrows gain and lose weight through water absorption or loss. I would think it a difficult task to sell arrow shafts at a particular spine grouping since their arrival in Arizona would read differently from the same spined group arriving in Louisiana after acclimating over a period of time. I also wonder how wet they are (or dry for that matter) when they are measured for spine and are shipped. Come to think of it, the variables to be considered alone with a spined group of wood shafts would scare me away from making any claim; too much to consider! :-X. Porosity/density, grain straightness, length...hats off to those who stabalize enough to even get close! It would be interesting to take a cedar shaft at 45# and put in a 110 degree hot box for a week and measure spine and then put it outside (assuming high humidity) for a week and measure the difference between the two. I would guess that difference would be quite remarkable.
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I'm finishing up a bow from that 'recently felled Ash tree' to go with the arrows from same...it's amazing to me how completely different the spines are from the arrows made from the same log of Ash...it is remarkable...there are some that are bendy as wet noodles and others which are quite stiff (shafts split out, not sawn and dried similarly). I was also wondering, on the ones that are really bendy, if 'heat treating' them would stiffen them up enough if they are close to a particular spine weight (like a bow belly is heat treated). Not sure, but once I finish up the bow I'll get some pics out and start on my spine tester...the neat thing is this bow is squirrely in the alignment department (in a good way) so that it's center shot...you can notice a difference in shooting the 'bendy' arrows however, although they hit in the same spot, but you can watch them 'wiggle' as they go down range; its weird to observe.
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anyone got a pic of the finished spine tester "skeaterbait" linked to?
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A very simple way is along the same thought process as DCM.I use a 20 oz Coke bottle full of water with a little hook for hanging coffee cups.My hangers are 28" apart and I set it with known splined arrows.