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I found that a thick catalogue or a phone book works quite well to measure the strength of a shot (using standard darts). You just count how many pages the dart penetrated. Since most of these already have page numbers, it makes it quite easy.
 

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Great idea if all things are equa, l but all it takes is one dart to be sharper or less sharp than the others and your readings will be outta wack. Your buddy could have a shorter dart flying at twice the speed with dull tips and your longer darts with sharp tips at half the speed might penetrate farther than the lighter darts of your buddy. Not a good measure of speed but certainly could be used as an indicator of penetration.
 

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If you shoot the same dart, or use a given degree angle for the tips... and sharpen them all in the same way...

Actually past a certian point, sharpness doesn't matter.

I cannot tell the difference between a razor blade and an xacto cut. Both are friggin sharp, but the razor(expecially one of the old gillette blued)is bloody sharp while the razor is just razor sharp ;) they both cut about the same.

Realistically, if its sharp enough that it goes right through the skin, and you can't tell....

go for it.

I love the idea, but I lack a phonebook.
 

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If you shoot the same dart, or use a given degree angle for the tips... and sharpen them all in the same way...

Actually past a certian point, sharpness doesn't matter.
On the contrary, it matters a great deal. I can take two identical darts one with a long sharp point and the other with a shallower point. With a good point I can blow that dart through1/2 inch plywood yet the dart with the shallower point will barely get through1/4 -38 plywood.

The post was suggesting a cheap way to determine blow gun speed. Penetration is not always related to speed. Therefore it is not a reliable method of determining anything other than how many pages you punched through that shot.

There is one software program that is free for download around here somewhere that uses sound to determine speed. It apparently gives satisfactory results and is free.
 

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Teach, I respect you a great deal, but in my experiance with different levels of sharpness of various knives, broadheads, spears, and blowgun darts...

two points with the SAME edge angle, both sharp enough to shave off fingernail shavings, even if one is far sharper than the other, will penetrate virtually the same.

AKA one might be sharp enough to shave with easily, one might be barely sharp enough to shave fingernails. There is a vast difference in sharpness, but both are pretty sharp.

They penetrate about the same.

I have found with a spear, it will sometimes go deeper when you don't make it super-crazy-dangerously-friggen sharp, but just use a 200 grit whetstone. It will be slightly serrated.

Seriously.

Sharpen two points to 35 degrees, 3 edges. make them sharp enough to shave little pieces off your fingernail(an 200-400-800-1200 grit works well). then dull one so it will just barely cut into the fingernail, and shoot both with the same power. They will penetrate virtually the same, the sharp one might go a couple pages deeper.

35 deg is pretty dang sharp for a point.

27 is better, but much more fragile.
 

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I appreciate your appearing to tread lightly with your introduction but I can assure you that there is no need to. The beauty of a forum is to exchange ideas. Sometimes we agree and other times we don't. I hope I havn't given you the impression that I'm unwilling to listen to your view. If I have I apologize. But here is the deal, when any of us hears something that is different than that of what our own experiences have been and actually contradicts those experiences we owe it to each other to suggest why. A forum can be a wonderful learning platform that way.

So here is where I am not making the leap of thought with you because you are talking knife blade cutting edges and spears. Both of these edges are designed to cut. I was talking purely about target darts - round wire target darts sharpened to a round point designed to penetrate (totally different) and the greater the angle of that point the greater the penetration providing the point is not damaged during the penetration. I have taken darts side by side, ground to the same angle and merely polished the bevel of the points of half of them and seen time and time again that the polished ones penetrated farther into the plywood than did the darts with the unpolished point bevels.

I'm thinking you were perhaps talking about hunting broadhead type darts when I was talking target type? If so, here in lies our dilemma.
 

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Oh.

Now that you have clarified that you are talking about ROUND point, with a sharp tip, like a needle, this all makes sense.

I was talking about these sort of points, which is what I have always used-

[image]https://encrypted-tbn2.gstatic.com/images?q=tbn:ANd9GcQzq0KQuQsim5AwiGei7vQHa9q5GYajiWw4WaMUwl2Da73T8XGQ[/image]

Therin lies our problem.

I file that sort of points onto my target points because they penetrate much better than rounded points, and last much longer when shooting wood targets before becoming blunt.

They also make a nice little triangle-hole, which is much easier to see when there are a ton of holes in the wood.

I believe you meant the lesser the angle, the more penetration... a 25 deg point will go much deeper than a 70 deg point....

measuring from the axis of the wire...(aka angle from the lengthwise axis of the dart... I don't think I am being very clear here).
 

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It might be free without the cost of a crony, but it will come with the price of ones "efforts to do". But it's a hobby and no hobby comes problem free. This is a VERY ACCURATE way to find the speed of a dart. You just need someone to see where the peak occurs when shooting and a scale.

Ballistic pendulum chronograph

Ballistic Pendulum calculators
http://hyperphysics.phy-astr.gsu.edu/hbase/balpen.html

Extra Food For Your Thoughts: After you find the speed of your dart this will tell you how hi above your target you have to aim at a known distance in order to hit it dead on. This is also VERY ACCURATE if the above is also done correctly.

Ballistic trajectory calculation

Hope this helps !

Cheers my friends ~ GKU
 

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There is also another free way if you already have a lap top that has a sound card and mic, if anyone's interested I'll be more than happy to post.

~ GKU
 

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Yep, a ballistic pendulum is signifigantly more accurate than a cheap chrony... but it is MUCH harder to use.

But I am a cheapie...

lol

i do love ballistic pendulums.

BTW you can simply attach a section of pen ink to the pendulum and it swings... and marks where it swings...

Never try to use a ballistic pendulum for a potato cannon.

It requires a heavy-arse pendulum.
 

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On the subject of speed ... Other than spending a bunch of cash on a Chrony (unless you belong to an Archery range where they have one, and the guy in charge will allow you to set up a target and shoot (Joe "Brokenfeather" Darrah did this for us one time at a competition he hosted near Berwyn, PA several years ago) through it to get an accurate speed ... Mattel has a toy Radar Gun for Hot Wheels that is failrly accurate. Image seen here - http://www.amazon.com/Hot-Wheels-J2358-Radar-Gun/dp/B000EHLB0M You'd have to do a bit of math to convert to FPS, but its doable.
 
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