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Rant on nerf modding

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Unread postAuthor: JDP12 » Fri Nov 13, 2009 12:54 pm

sorry. I mean they would be great if you had to punch through a wall to get at a zombie... but not too much good for anything else.

I thought about opening it up to all ammo, but if we are keeping this a strict nerf contest, it has to fire nerf darts.
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Unread postAuthor: btrettel » Fri Nov 13, 2009 1:32 pm

Sounds good ilovetoblowthingsup. Feel free to create a thread in the appropriate place.

As far as I can tell the only pertinent guidelines from the HvZ rules are 1) guns can not be realistic, and 2) darts can not hurt on impact. Unfortunately their criteria for determining if something hurts is likely to hurt regardless of what sort of gun is used. I get the picture though--don't make something that'll hurt.

As far as the final submission date goes, March 1 sounds reasonable. Hopefully that will give everyone plenty of time.

And thanks for the compliments on FANG 2. I'm not going that exact route any longer but it was an interesting experiment.
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Unread postAuthor: iknowmy3tables » Fri Nov 13, 2009 1:51 pm

1) I don't think the guns have to be safe for HvZ just nerf wars because HvZ is almost entirely close quarters and it some cases it's alright to have a long range gun exclusively for long range
2)of course, are there any other modes of firing? this is obvious you don't have to state it
3)again obvious
4)of course they're nerf guns, however darts need some weight at the tip otherwise they don't work for example the rubber in the tip of Nerf darts acts as the weight, lets just ask for comparison approximate range with normal store darts
5)Nerf modders widely use the term for moding they even completely replace the internals of one gun for no obvious reason.

we should point out what contestants are up against, for example: your gun ought be able to fire more than 1 dart in 1.5 seconds and have ranges of at least 40ft
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Unread postAuthor: Ragnarok » Fri Nov 13, 2009 2:09 pm

btrettel wrote:Unfortunately their criteria for determining if something hurts is likely to hurt regardless of what sort of gun is used.

Given the way it's phrased, that'll be a deliberate "if you have to ask if it's too powerful, it's too powerful" answer.
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Unread postAuthor: JDP12 » Fri Nov 13, 2009 2:24 pm

ok thanks for the input. I will create a thread when I get home.

Sorry for some of the obvious stuff.

I know that they ahve to have some weight- i more meant overkill weight- i.e. heavy fishing sinkers. Perhaps we could set a standard front weight that would be allowed for this?

Opinions on what that should be? I agree they have to have some weight


I will create a thread in the Website discussion and PM PCGUY when i get home tonight
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Unread postAuthor: Ragnarok » Fri Nov 13, 2009 2:55 pm

ilovetoblowthingsup wrote:Perhaps we could set a standard front weight that would be allowed for this?

You might be best off defining it as "no hard tips".
If someone can build a dart which has weight in the nose, but in such a way that whoever is hit isn't hit by anything hard (The nose is covered in foam, or whatever) - then... well, I wouldn't be too fussed to be hit by something like that.
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Unread postAuthor: blackhawk13 » Fri Nov 13, 2009 3:51 pm

Ragnarok wrote:You might be best off defining it as "no hard tips".
If someone can build a dart which has weight in the nose, but in such a way that whoever is hit isn't hit by anything hard (The nose is covered in foam, or whatever) - then... well, I wouldn't be too fussed to be hit by something like that.


i dont think you would want to be hit by my target shooting darts. its a marble (about 3/8inch) jammed in the foam of a nerf dart that has had the tip ripped off then covered in duct tape. from my sprinkler valve smg at 100psi it will rip through 2 layers of cardboard and then continue another 20 feet
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Unread postAuthor: Ragnarok » Fri Nov 13, 2009 4:36 pm

@blackhawk13: Can we be sensible here? Rule 1 already dictates that they shouldn't hurt, so obviously, if you think your "target darts" will hurt, they're already ruled out by those criteria.

I'm saying that weighted darts shouldn't be ruled out as long as they can be made in such a fashion that they don't violate Rule 1 - hard tips are an obvious violation.
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Unread postAuthor: btrettel » Fri Nov 13, 2009 5:07 pm

No hard tips is a good guideline. "How hard is hard?" is the important question though...

Weight alone isn't a safety problem. Kinetic energy (KE) is, specifically, kinetic energy density. For example, you could have a really heavy slow dart that has less kinetic energy density (KED) than a normal weight fast dart... in fact that is likely as the velocity is squared in the kinetic energy equation. Also, consider one wide dart with the same KE as a thinner dart. The thinner dart obviously has more penetration power.

Here's the equation for KED of a dart:

KED = KE / area of dart nose

The dart nose area is what matters... if you have a head on your dart and it tapers you have to put in the thinnest part. If it tapers down to nothing you have a problem. Most Nerf darts don't have real noses so this isn't a big problem here. For really soft nose cones you might as well ignore this and put in only the area where the front weight is.

As you can see this does what you expect... higher KEs are bad as are smaller diameter darts.

Using KED is not only the correct way to do this--it also would make us stand out against the ignorant Nerf forum goons.

This page has some KED figures required before bad things happen: http://www.beemans.net/airgun%20ballistics.htm

the threshold levels for beginning penetration in human tissue are about 0.2 J / mm^2 for bone, 0.1 J / mm^2 for skin, and 0.06 J / mm^2 for eyes


Designing for safe eye shots is a good idea. Now, what safety factor should be we? For a 0.53 inch dart a KE of 8.5 J will cause eye damage (this seems really high). How does a safety factor of 4 sound? That would make the maximum KED be 0.015 J/mm^2. Crunching some numbers, this seems okay, maybe a little high, maybe a little low. A 1.1 g 0.53 inch diameter dart with a velocity of 62 m/s has a KED of slightly less than 0.015 J/mm^2.

It's worth noting that a softer tip will also reduce the energy imparted to a person... so there's an additional factor to take into account. For the sake of safety we'll consider all of the dart's KE goes into what it hits, but this is something to keep in mind.

Edit: If you are using flat tipped darts like "Slug darts" (search NerfHaven for them) the equation below will calculate your KED.

KED = (2 * m * v ^ 2) / (pi * d ^ 2)

where
m is the dart mass
v is the dart velocity
pi is 3.141592...
d is the dart diameter

An example for m = 1.1e-3 kg (1.1 g), v = 62 m / s, and d = 13.46 mm...

KED = [2 * (1.1e-3 kg) * (62 m / s) ^ 2] / [3.141592 * (13.46 mm) ^ 2]

...reduces to...

KED = 0.01485 J / mm^2

Slug style darts with one washer weigh about 1.1 grams and most Nerf darts have a diameter of about 0.53 inches (13.46 mm) so this basically says for Slug style darts the maximum velocity to have a KED lower than 0.015 is 62 m / s.
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Last edited by btrettel on Fri Nov 13, 2009 10:52 pm, edited 1 time in total.
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Unread postAuthor: SEAKING9006 » Fri Nov 13, 2009 5:35 pm

I've already come up with a solution, borrowing from IDPA equipment guidelines.

The power factor.

In IDPA, a gun (or more properly, the ammunition IN the gun) is considered illegal if it fails to meet the require 'power factor', which is a numerical value based on bullet weight and muzzle velocity. For nerf, we can modify it slightly. For the ammo to be legal to use in the gun specified, it must be BELOW the standard power factor. For darts we can expand it to three points of measure. Muzzle velocity, total dart weight, and tip hardness.

Tip hardness is fairly easy to calculate, with a very simple and easy to build test rig. To test the hardness, cut off the tip of the dart being tested (using a dart that of the median weight for the batch used) right at the foam, placing it inside the rig, which is basically a PVC pipe with a rod inside and a weight on top of the rod. Lift the rod, place dart tip inside, lower rod onto dart tip, and measure how far the weight depresses the tip. Would likely be measured in millimeters. Take the standard power-factor, and divide by the depression distance. TO obtain a good baseline for standard rankings, just take a number of stock guns and darts, test them, then test some popular mods with really soft and really hard tips. Velocity measurements can be done at large meets, since it's unlikely that you won't get everyone to pitch in enough money to get a usable chrony, or have someone bring a fairly high speed camera and a measuring board.


Or, you can live in Texas and start an HvZ game there, and just set up the power limits to be along the lines of "They're friggin' darts, grow a pair and take it."
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Unread postAuthor: iknowmy3tables » Sat Nov 14, 2009 1:23 pm

I think it's best to ask for the range with with an unmodified streamline for comparison (it doesn't have to cycle with standard darts if it's a special repeater system that works with other darts)

as for the safety of their other darts lets not inquire shall we, do we really want to take the legal responsibility by making ourselves official safety nazis and also risk violating spudfiles rule #2
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Unread postAuthor: Lentamentalisk » Sat Nov 14, 2009 5:54 pm

or, shot yourself in the arm with it a point blank, and if it hurts, turn down the power... Seriously, this isn't rocket science. As someone earlier put it "if you have to ask if it is too powerful, it is too powerful." Just don't make something dangerous.
There.
Done.
That wasn't too bad was it?

Just be reasonable.

If you submit something that everyone thinks is terribly dangerous, then the judges will probably not go for it.
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Unread postAuthor: JDP12 » Sat Nov 14, 2009 6:21 pm

I had a discussion with pimpann and the contest will not be happening, so it may be best to stop discussion of it
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Unread postAuthor: iknowmy3tables » Sat Nov 14, 2009 7:06 pm

can we at least set a goal to build some good nerf guns by February or later that will be released to the forums that month and on the first day of the next month we make a comparison thread, a full blown contest isn't necessary, what this ought to be is a collective effort (like the community projects) to assemble a compilation of excellent nerf guns first seen on the web here at spudfiles.com. Our efforts may help advance the diy field of homemade nerf guns by showing those who think the so called "wraith system" is an innovation that they are behind

so any one up for a community compilation project?
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Unread postAuthor: Ragnarok » Sat Nov 14, 2009 8:25 pm

ilovetoblowthingsup wrote:I had a discussion with pimpann and the contest will not be happening, so it may be best to stop discussion of it

Nothing to stop a bit of unofficial competition, surely?

If a load of people agree to build Nerf guns for some friendly rivalry and you make it clear it's unofficial with no prize other than bragging rights, then short of it breaching forum rules in some other fashion (and I think Nerf guns are well clear of Rule 2), there should be no issues.

Really, I'd like to see more unofficial contests and head-to-heads, trying to work towards the best design fitting certain criteria. In the end, it'd help develop and test ideas to develop spudding further.

Not that we're wanting for development, but more wouldn't hurt.
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