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My DIY Arrow Spine Tester

41910 Views 131 Replies 57 Participants Last post by  dw'struth
Product Electronics Electronic instrument Machine


Machine Machine tool




1 dial gauge = $12
1 pack of roller blade ABEC 7 roller bearings from Dick's Sporting Goods = $30
1 four foot long 1x4 pine board cut to 28" = $3
Miscellaneous steel brackets, bolts, kotter pin, nuts, washers , etc. = $55
5 hours of my time and labor putting this thing together = Free
Years and years of arrows tuned to perfection = Priceless
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could you do the same thing with an arrow straightner? just roll the shaft and read the gage.
Yes you can if you attach a weight to the arrow shaft.
 

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I'm not sure that an arrow straightener would work that well.

When finding the stiff side of the arrow you would want the bearings to be as far apart as possible to get the most accurate reading.

An arrow straightener usually has the bearings placed fairly close together.
 

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I'm not sure that an arrow straightener would work that well.

When finding the stiff side of the arrow you would want the bearings to be as far apart as possible to get the most accurate reading.

An arrow straightener usually has the bearings placed fairly close together.
It's just simple Fizzics to determine the proper weight for the distance between bearings. You would need a higher weight directly proportional with the loss of distance between bearings for the same amount of measured deflection.

On the plus side you could use the reduced distance to determine where along the shaft a weak spot might be. Don't know what you'd do with that info.
 

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A question for y'all:

About how much difference do you see between the weak side and the strong side of the shaft?

After spending $30 and a couple hours, I built a tester similar to this, but mounted vertically on a 2 X 10 board.

I did the 3 eyebolts trick with the 5/8 x 7" bolt with stacked washers coming down through the eyebolts. Shaft is held at the ends with eyebolts coming horizontally through the wood. After not being impressed by the results, I hung the weight by a wire on the shaft. I even clamped on a pair of vise grips (as extra weight) to see if that made a difference.

I could care less if actual spine = manufacturers stated spine, but simply wanted to find strong/weak side in order to index and fletch arrows.

Long story short, I saw about .003" difference between strong and weak side. (Easton ACC)

Are you kidding me? Time and money to find out a meaningless .003?

WHat results do you get?
 

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Discussion Starter · #49 ·
A question for y'all:

About how much difference do you see between the weak side and the strong side of the shaft?

After spending $30 and a couple hours, I built a tester similar to this, but mounted vertically on a 2 X 10 board.

I did the 3 eyebolts trick with the 5/8 x 7" bolt with stacked washers coming down through the eyebolts. Shaft is held at the ends with eyebolts coming horizontally through the wood. After not being impressed by the results, I hung the weight by a wire on the shaft. I even clamped on a pair of vise grips (as extra weight) to see if that made a difference.

I could care less if actual spine = manufacturers stated spine, but simply wanted to find strong/weak side in order to index and fletch arrows.

Long story short, I saw about .003" difference between strong and weak side. (Easton ACC)

Are you kidding me? Time and money to find out a meaningless .003?

WHat results do you get?
.003" makes a huge difference at 40, 50 & 60 yards. If you index your arrows all the same way, they'll group much better.
 

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If you are using it to find the stiff side and have free wheeling bearings all you have to do is put the shaft on the end bearings and press down in the center of the shaft with the third set and the high side will roll to the top, no need for a gauge or weights.
 

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Discussion Starter · #51 ·
If you are using it to find the stiff side and have free wheeling bearings all you have to do is put the shaft on the end bearings and press down in the center of the shaft with the third set and the high side will roll to the top, no need for a gauge or weights.
Yeaaaaaahhhhhhh...no. Roller bearings don't roll as easily as you may think.
 

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Yeaaaaaahhhhhhh...no. Roller bearings don't roll as easily as you may think.
Man everything people post that you dont like you just love to take stabs back at them dont you???? Nice pile of washers and metal!!!! quit being such a smart azz if you dont like what someone says, guy was just trying to point out another option, it may not be totally intended for you and your piece of whatever but maybe for someone else and their ideas. did you ever think about that???? Prolly not cause you think your little contraption is the best eh????

.003" makes a huge difference at 40, 50 & 60 yards. If you index your arrows all the same way, they'll group much better.
and you can simiply rotate arrows while shooting and index arrows also, but maybe youve never done that???? the difference in .003 straightness and the difference in his test under load and only difference of .003 is a big difference!! its not .003 on a resting shaft
 

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I'll give someone a trail camera if they want to build me one
 

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Guys I am not sure I understand the need for the spine deflection charts. If your dial indicator measures in thousandths, why do you need a conversion chart? If it deflects .400 is it not a 400 spine arrow? What am I missing here?
 

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Discussion Starter · #58 ·
Guys I am not sure I understand the need for the spine deflection charts. If your dial indicator measures in thousandths, why do you need a conversion chart? If it deflects .400 is it not a 400 spine arrow? What am I missing here?
An arrow won't deflect uniformly across it's entire circumference. One side may be stiffer than the other side due to the overlap of material when the carbon fibers are rolled into a tube. In order to get all your arrows to fly consistently from your bow, they should all have their stiff side oriented the same way.
 

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LI, I am aware of the differing deflection around the circumference of the arrow shaft. I was refering to your post number 19 that was reffering to post #18. I dont understand why you would need the "spine-deflection chart" that is in the thread link in post #18. Thanks for your response but that "spine-deflection chart" still doesnt make any sense to me.
 

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Nice work... I've been pressing my arrows to locate the spine. this looks like it may be easier to do...Thanks for posting it up...JW
 
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