I have been trying to calculate some Gold Tip Traditional Classic XTs on the DSC. The DSC doesn't have it stored. So the "other" option has to be selected. That means ASTM has to be converted to AMO, which is done by dividing the ASTM static spine by .825. For example, a .500 spine divided by .825 gives you .606 AMO static spine.

So whether I plug in .606 or 60.6 or 606 they all give equally funky dynamic spine numbers.

For example, I go to the Gold Tip site. Go to the Trad Classic XT and then to the spine selector. I plug in the following: Recurve, 31" arrow length, DW 50-54 lbs, point weight 125 gr and IBO recurve. It recommends a 340 spine.

Now back to the DSC. Click on Other (arrow shaft size) and enter the AMO static spine 41.2 (.340/.825), shaft diameter .286, BOP 31, point weight 125, insert weight 15 (ballistic collar), footing "yes" 80 gr, nock end 20 gr, and fletching type "other" 44 gr.

The result for the dynamic spine (pounds) comes out to 19.6. If the AMO static spine is changed to .412, the DS(lbs) becomes -17.8 and if introduced as 412 comes out to 359.6.

Obviously, that arrow set up is way stiff and not any of those listed final numbers.

How do you get an accurate calculation under the "other" section?

(if you want the bow input as well its a BL TD Recurve, 52#@28, 29.5" DL, CC Strike plate position .125, FF 16 strands which comes out to 70.3)

Way too much splainin Lucy. lol Go to: 3riversarchery Click on the calculator and enter your data. If you already did that and it doesn't work, well....don't know what to say. Start shooting wood? I know it works with wood arrows. lol

It doesn't work for me either. Personally what I do is take the deflection of the carbon arrow and multiply by .85. That lets me convert the carbon spine to approximately what it would be if it were a wooden arrow. Then I use that deflection number. For example, a .600 carbon comes to .510. Which when converted to AMO spine is 51lbs..

I've found that if you keep a test kit in .400, .500, and .600, it will cover about 95% of your tuning needs. You can put the kit together over time and you won't have a huge investment.

From there it's a simple matter to get the arrow you want.

Your strike plate measurement, is that .125 PAST center?

FDP,

I have test kits. That's not the issue. I haven't chrono the arrows, but can safely assume my current carbon express 250s are at about 180ish fps.

I want to mess around with a new selection of arrows that will up the speed.

The .125 is automatic. With the strike plate it would come to 0.

So I guess I don't follow. In it's simplest form it sound as if ( all it sounds like you want is increased speed) is to go to a lighter physical weight of arrow. You should be able to do that using either an arrow of the same spine you are using now, or by using an arrow with a softer spine, and lighter overall weight and adjusting the center shot measurement to accommodate the change.

FDP,

That is essentially correct. However, I would also like to know how to correctly input the arrow specs in the DSC for arrows that are not stored.

Understood. I can't help with that. Like I said, I can't get it to work either.

Thanks.

How about just using the listing for a GT shaft that is listed? MP

MPDH,

That is what I have done as an alternative, but I was wondering about the input in the event I happen to come across an arrow not on the list.

You're applying the conversion factor .825 incorrectly

AMO = ASTM x .825

You can always mentally double check yourself on this conversion process by knowing that when given a shaft with an ASTM spec, if you were to throw that shaft on to an AMO spine tester, the shaft would bend LESS because the support points are 2" closer to each other.

So, your ASTM .500 shaft is a .412 AMO shaft. And at that measurement, that is a 63# shaft.

Although long, this blog does address this as well some other aspects:

http://blog.ohlonearchery.com/going-low-tech/

Thank you Bender. You are correct. I just finished exchanging a series of PMs with Rick Barbee.

So in sum once the deflection is figured out use a Spine Deflection Chart to convert and get the poundage that gets plugged in.

Wow. It didn't come out sideways....

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