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Why does K'nex ammo spin out? Answered

I shoot yellow rods, green rods, blue rods, Oodammo, you name it, and they all are unstable and spin out. WHY IS IT SUDDENLY DOING THIS? It's really bothersome, it's messing up my aim and makes my gun looks bad. I have tried fins, but they only work at short distances. I'm only using 4 #64 bands on a black rod hammer, but why is it so unstable?

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Knex Lego Maniac (author)2011-02-12

fins should look like this
i first wrap a layer of tape around the rod
then i fold a piece of tape leaving the ends to attach to the rod on the layer i just taped on
i tape then as pictured making sure they are evenly spaced and at a correct angle
then i tape from one fin to the other to add a stiffening layer
so right now the fins should be different heights and uneven looking which is ok cause you cut them to size
but first add a piece of tape the the leading edge of each fin so that the leading edge is smooth and strong
now just cut them down to the size i have pictured and your fin ammo should be shooting perfectly straight and forever far with the right gun an bands
i use gold rods which r similar to red rods for the shaft
the gold rods have a line which is where you should start the fins

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user

unfortunately the picture isn't shown with the gold rod lol

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user

Nice, I don't have gold rods though...
I usually make the fins like that, then cut them at a slant so they look more aerodynamic and arrow-ish.

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user

gold and red rods are practically the same thing

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user

don't slant em you need the surface area and it is hard to keep the slants even which if uneven will throw off the accuracy of the round

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Fred the evil puppet (author)2011-02-08

My fins don't work at all! They actually STEER the bullet away from the target
Or in any direction. I need somebody to help with the fin problem,
As everybody gets 50 ft extra with them when I get 50ft less with them.

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user

Give every fin an identical slant to one side (say, when you stand the ammo up on end, and look at one fin, it is leaning 5 degrees to the right - turn the ammo to look at the next fin, and that will also be leaning 5 degrees to the right).

This will make the ammo spin on its long axis, improving stability and accuracy, and potentially increasing range.

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prodo123 (author)Kiteman2011-02-09

I personally sharpen mine in an electric sharpner to make grooves from the sharpening process for the same effect. The fin method could be difficult to accomplish, since the best spin-to-stabiliy ratio is when the fin is pointed at the corners of the rod.

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Kiteman (author)prodo1232011-02-10

But, since you said in the opening topic that your ammo is spinning out, maybe this sharpening isn't enough?

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prodo123 (author)Kiteman2011-02-11

The reason why most rods spin out is because:
a. Their flight pattern is shaky
b. Too much force is applied off-axis during firing
c. Shaky posture while firing
d. Bad gun/ammo
e. Weight balance issue
f. High resistance to air

Oodammo solves the weight balance issue with a heavy tip. It is still unstable. Normal rods are less balanced, more unstable and has a low tolerance for off-axis impact (If the ramrod hits the edge of the rod instead of the center, it spins out). However, it's aerodynamics are much better than Oodammo and the length of the gun barrel may solve the off-axis issue.

Fins, on the other hand, when made correctly, will solve all issues except the weight balance. Tipped fin ammo are the best, but they're a pain to make.

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DJ Radio (author)2010-05-20

Fin ammo should be the best for stable ammo.  If fin ammo is problematic for you, you are making it wrong.

Mind telling me what gun you are using to fire your ammo?

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user

Oh, you say that he is making it wrong well I have fin problems too.
What exactly do you have to do to make it right?

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user

Make sure the fins are straight. Make sure they aren't crooked and that they aren't bent or torn up.

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An Villain (author)2010-12-17

K'nex ammunition will "spin out" for several reasons, the first and most obvious is air resistance, buffeted by air currents caused by its own impetus, it will "kick" slightly off center, and because of air resistance, it will attempt to orient itself facing forward again, creating a larger air current around itself, this process will repeat until the round is turning somersaults in the air, or it hits the ground/wall. The next factor in K'nex ammunition's instability is the shape of the round, they are very long, thin, and light, creating a larger surface area for the air currents to push them around (the grooves in the pieces help this along as well, nearly doubling the overall surface area of the piece.) The lightness of the round is also a problem, being made of only a lightweight polymerase material, they are very susceptible to whatever forces may act upon them during their brief period aloft. The following problem with the round, does not lie with the round itself, it lies in the weapon from which it was fired, the first reason is that they typically have a very inefficient guidance mechanism, which is almost always shorter than the round and is only used to secure it until the round is ejected from the firearm, this is a problem as the round is subject to whatever forces act upon it just a fraction of a second after it is discharged. The final problem lies not in the round, or the weapon, but with the person firing it, for however steady your hand may seem, you will invariably always "jerk" the firearm left, right, up, or down depending on the weight of the firearm, your dominant handedness, and the weight of the round being fired, this is not typically noticed on smaller rounds as they do not possess much inertia due to their light weight, and their small size makes it difficult to notice the spinning, however, the larger the round you are firing the more noticeable it will become as they are typically brightly colored and are much longer, though they retain the diameter of their shorter counterparts, the reason the longer rounds are more adversely affected by the "kick' provided, is their inertia is much higher so they spend a fraction of a second longer in the barrel making it so they are jerked slightly off target while a small amount of the round is still in the barrel, and because the part of the round outside the barrel has higher inertia than the portion in the barrel, it will keep going straight relative to its original path while the portion in the barrel moves to the side causing a vertical spin axis relative to the round, causing it to spin before it has even gone a meter away from the gun.

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TheChemiker (author)2010-05-19

The rounds aren't spinning which you need to be stable, other than fins or a weighted front, because you really can't get a good rifle affect with knex.  If you make finned ammo well, it should stay stable for a long time with a good gun, like the untangle.  Rods and all other ammo spin out because of air resistance, which rifling and fins fix.  Oodammo sometimes spins out, sometimes not.  Hopefully this answers your question.

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rhysc7 (author)prodo1232010-05-20
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DJ Radio (author)rhysc72010-05-20

Problem with that is there aren't that many guns designed for BB's.  Knexsayer can fire 8 BB's at once if you mod the turret though.  That's the best option.

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prodo123 (author)DJ Radio2010-05-23

bbs are shot by air compression. K'nex is mostly fired by an impact.

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TheChemiker (author)prodo1232010-05-23

Too bad this isn't a question, then you could best answer me.

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