I just could not bring myself to paying $100+ for a store bought dowel rod flexer. I believe the pics will explain everything. P.S. add nails or screws to the BBs in order to increase the hanging weight. For wood shafts put the hooks 26" apart, my nail is 3" and the board is 3/4".

Well there Nielbilly, that looks like it will get the job done.

I see how it bends but how do you measure the deflection? Frank

That is nice

I made one my self but not as simple. I wish i had that idea.

good

max

Nice one Neil ... simple and effective ... thanks

Frank, take a look at the center of the board. While nail moves up and down with the flex of the shaft, the carpenter square sets next to the tip of the nail.

here's a better zoom, measure backwards.

what about light spined arrows? i have some small kids shoot with me and there arrows are 25-35#.

Sweet!!

I like it. Cheap folks have the most ingenious minds ;-)...Van

Thanks for a great easy and cheap idea!!!

Cool idea Neil. I like it alot. David

Ingenious!

what difference does it make whether light or stiff arrows??

Thats thinkin Nielbilly. I use something very similar. I like yours even better

Light arrows (under 40# spine) can be a problem because of the extreme amount of deflection. What I do is lower the hanging weight to 1# and then double the defection reading...Van

Its not the light shaft that will be the problem, its the heavy ones. Since there is no magnifaction of the scale, it will be extremely difficult to tell the difference between the higher spines,and how do you zero the scale? even if the shafts are die straight, different diameter shafts will not zero the same, which will effect the reading. Bob

Correct Bob. What I was referring to was running out of scale using a homemade spine tester. In fact one commercial spine tester manufacturer uses this method (1# weight) to make the tester more compact...Van

Good job.. Tho it DOESN'T tell a fellow 'zackly what his arrows are spined in professional AMO terms or recent deflection numbers , such a simple system WILL enable the archer-arrowmaker to DUPLICATE arrows he has found shoot well off his bow..Jim

thanks for advice on light arrows might try making one for me .

You don't have to zero it, as 1/2" of deflection is a 1/2" (or 3/32", or 5/16") of deflection no matter where you take the measurement from. Same thing if you use a dial indicator, it doesn't have to be zeroed for it to show that it has moved however much.

Porkchop, you have to take the measurement from "zero" or your results will not be accurate. But maybe I'm misunderstanding your statement ;-)..Van

BRILLIANT!

zero is whatever it reads without wgt. you dont have to start at a zero reading. If without the wgt it measures say 2" to tip of nail, then you add the wgt it measures 1.5", you have a 500 deflection

I see what you mean TD2 but I can see in the pic how he could zero his scale first and then take the measurement. Less math ;-)...Van

One thing I have always wondered and hopefully there is someone out there that can answer...does grain orientation matter when you are measuring spine? Example: hanging the weight cross grain vs. not cross grain. I know a 2x4 is stiffer laid on its side as opposed to on its face, but maybe a round shaft there is no difference?

Dave, in my experience with quality wood shafts there is hardly any spine difference when rotating the shaft on a spine tester. If there is much difference (2#'s for example) I'd not consider the shaft a good one...Van

I like it! It's simple and functional. Mine's a bit more complicated but easier to read.

For lighter spines either pull the screw eyes tighter to the board or start with a longer nail. ;-)

Rose City Archery has a printable deflection to spine chart.

http://rosecityarchery.com/AMOspine.html

Dave, I pre-rift my arrows so there is only one direction I spine test them in. Growth rings are running horizontal at all times, so thats the orientation of the shaft when adding weight. My runnout grain rift looks like this on the top side of the arrow......Nockend-->>>>>>>---point.....

Stumpkiller I like yours!! Looks like my first prototype ;-) But it was accurate. I kept fooling with them and came up with my final version...Van

Orientation of the grain! The AMO standard is to align the grain on the spine tester so edge grain points up, this will bend the shaft against the grain. I agree with quality shafts, different orientation will not change the reading, however the standard was established so the guy without a tester would know how to orient the nock as there is a small percentage of shafts that will differ as the orientation changes. In the hayday of the wood shaft, ALL shaft manufactures and suppliers oriented the shaft in the described manner, so the end user new how to orient the nock. TD2: I guess if your only doing a couple of dozen shaft you can take your reading from anywhere you wish, however I can guarantee you using all those different numbers you will make more mistakes that using a zero starting point, even there mistakes are made, so why compound the problem.

The problem with the tester described above is the lack of magnification of the reading. Let me give you an example of what I'm saying. the smallest reading you can make on that adjustable square is 1/16" that equals .0625 in thousands. a spine of .520=50# if we add just one 1/16" difference you get a 44# shaft. So your accuracy is at best 6# and this doesn't take into account any errors you might make during the readings, such as the nail doesn't touch a mark its above or below at zero now you error becomes 10#. I guess it depends on how accurate you expect spine to be. Take it from someone who has spined 3 or 400,000 shafts in his life. When I get a shipment of shafts I will spend 2-3 8hr days spinning shafts. Bob

Yep, the magnification part is very important. Mine pictured above is made to a 10 to 1 ratio. If the shaft deflects 1/2" then the pointer moves 5 inches on the scale giving you a very precise measurement...Van

Grain matters with wood. Spine also matters with carbon shafts. Rotate either on a spine tester and you will see the deflection change. Only quality aluminum shafts don't have a variable spine.

With a little care, you can adjust your nail point to the 1" mark on the scale to compensate for different shaft sizes.

Thanks guys for answering my question! Now I know for sure.

Neilbilly, hope you don't have a patent on that tester because I want to make one for myself!

Im wonderign how would you spine test a 32 inch arrow? im new to spine testing, i honestly have n idea, all iknow is the certain deflection of the shaft equals ths strenght bow it can be with, for example the more flex the weaker the shaft, the less the stronger the shaft

Im looking to build a tester and want to mke a needle type but i cannot figure out the mechanism of it, anyone have one that could show me pics of them>

Spine for a 32" shaft is simply mathematical problem. spine is measured between 26" centers and a 2# weight, that will give you a spine number for a28" arrow. To get the spine for a 32" arrow you simply deduct 5# of spine for every 1" longer than 28. As you can quickly see, that will not work with the simple devise that started this thread. There is a reason why spine testers are made the way they are. Bob

Aromkr is right again.Heavier spines really need something akin to a dial indicater or similar.I don,t see a need for actual weights on my spine tester.I know what shoots good out my various bows.I just mark (York tracker ,Skb 50 ,Burwood long bow) etc.Some of those bows are the same draw weight but they require a different spine to shoot good.Thats a good simple tester much like mine.Most of my bows are fairly tollorent of spine variation so 9 times out of 10 I just test my shafts in my hand as I make them.Two bows I own are real particular and I just knock up a tester as required.

OSR

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