Southern Brisbane Nerf Club

Thursday, 2 January 2014

FPS vs. Range

We all know FPS is a better measure of a blaster's performance... on paper. But in a war or HvZ game, it'll be the real world range of a blaster that saves you, not FPS... but why?

For reference, 1 FPS = 1.09728 Kph.

So, on paper, FPS is a much more accurate way of measuring a blaster's performance. But in a war, no-one is going to be afraid of your FPS, it'll be how far it shoots.

A chronograph will measure the speed of a dart as it leaves the muzzle (muzzle velocity) but when the dart passes through the sensors, it hasn't yet been greatly affected by wind, humidity, air density etc etc. The reason a range test is not a very good measure of a blaster's performance is because there are many variables that can greatly alter the results such as (on top of those previously mentioned) dart metrics (weight, aerodynamics, balance),dart accuracy and turbulence.

Let's look at dart metrics and how it can affect range:

1. Weight ("We" - we'll work with 1g for weight as it works ok for Elites. So 1g = 0 in this measurement, the lower the number the better)

A heavy dart will have more kinetic energy to punch through the air however, will drop to the ground sooner. While a light dart will not drop as fast but will not have the energy to penetrate the air.

2. Aerodynamics ("Ae" - we'll look at drag co-efficient, the lower the better)

Say you have two darts of equal balance and weight and the blaster performs equally for each shot and the atmospheric conditions were identical, but, one of the darts has a tapered head while the other has a flat head. The tapered head will perform better because the air will flow around the dart instead of being pushed out of the way by the flat headed one. How worn/damaged a dart might be can affect aerodynamics.

3. Balance ("Ba" - the further away from the head of the dart the weight is the higher the score, so the lower the better)

A dart with the weight toward the head will travel straighter and therefor have a better trajectory. If the weight was centred or biased to the rear, then the dart's flight would be hap hazard and the kinetic energy will be spent quicker than if the dart flew straight.

4. Accuracy ("Ac" - difficult to measure because it varies so much, let's just say that a straight line is 0)

If a dart fish-tails or curves off to the left or right, then that will use kinetic energy that could've been used to make the dart travel further.

Now the atmospheric conditions that can affect range:

1. Wind. ("Wi" - any wind will give an inaccurate measure of a blaster's performance, so the lower the better)

Can greatly affect ranges.

2. Thermal Up-drafts. ("TU" - for the same reason as wind, the lower the better)

Not likely to affect range by much, but can't be ruled out entirely. What happens is, the sun heats the earth and the radiating heat from the earth heats the air causing it to rise. This might improve ranges giving a false reading.

3. Air Density. ("AD" - another that's tricky to measure because it varies from country to country, region to region, find out what the yearly average temperature is for you and make that 0)

When fluids cool (air is a fluid) they become more dense. And the more dense the air, the quicker the dart will decelerate. Just like swimming through a pool filled with custard would be harder than swimming thorough a pool filled with water. Warmer air is less dense and therefore the dart's kinetic energy will not dissipate as quickly.

4. Humidity. ("Hu" - measure the same way as air density)

Any extra moisture in the air makes the air more dense.

5. Blaster Angle ("BA" rated from 0-45 degrees, the higher the number the better the rage)

I shouldn't have to explain this, should I?

Now, some of what I mentioned will greatly affect a dart's trajectory, some will barely affect it at all but it is a combination of all these factors that contribute to a dart's range and all of them variable. Now lets try maths.

We + Ae - Ba - Ac = "Y"
Wi - TU + AD + Hu + BA = "Z"

Range = Y + Z

Now if that makes sense to anyone or I'm wrong, please explain it to me.

So as you can see, there are a lot of factors that can affect the range of a dart and they are all variable. Even the dart itself is a variable as there are different types of darts (Elite, Streamliner, Stefan, stinger, etc).

But, with FPS, the blaster is generally placed right in front of the Chronograph with the sensors at 30cm (1 foot) apart. At (e.g.) 96fps muzzle velocity the dart spends 0.0104 seconds in the air, too little a time for the atmospheric conditions or dart metrics (unless it was made of cotton wool) to have a severe effect on the speed of the shot. Therefor, FPS is a more accurate way of measuring a blaster's performance because the dart spends less time in the air before we get a result.

So... why range test at all?

Because a range is what we're given on the blaster's box and I like to see if the range quoted is accurate. Also, I like to see how much the range has been increased over the box quote. Also, I'm too cheap to buy a chronograph and there are others that do that any way (look for a guy called Old Noob on GoogleTube for that).

In conclusion, FPS is a more accurate measure of a blaster's performance, but, I still think there is a place in Nerf for range tests because it's what we get on the box. And we all call Nerf mags "clips" because of what's on the box too.

~ Rob

4 comments:

  1. I think it boils down to how pedantic one is with the data obtained using a range test. The biggest problem with range tests is the trajectory of the dart itself - they are quite unpredictable. Furthermore, new darts will nearly always perform better than used darts, when compared with the same letter coded darts. Test parameters such as user height and true "parallel-to-the-ground" shots, or angle, are often ignored and rarely stated.

    Given the flight trajectory of darts there is always the issue of statistical significance. How many is enough? The problem at the moment is that some people claim that their mods will yield +X feet with a quick range test but the details of the test usually remains a mystery. This often leads to controversy when someone performs the mod and discovers that it doesn't really affect the range at all; or in some cases... hinder it. One such mod would be the Venturi effect mod for the Firestrike. In theory it sounds like it would work but the pressure and velocity involved seems like that the difference in performance is not noticed in real world tests,

    It is unlikely that we'll see people switching from range tests to chronographs anytime soon. They are simply too expensive (around 100USD I believe?) for most and some may find that they don't need the accuracy of a chronograph. After all, what is the real world difference between 90fps and 93fps?

    Perhaps standardizing the range test may help with comparing different blasters/mods...

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  2. I'm too cheap to buy a chrony also, I usually shoot targets around 30 to 40ft to see how fast and accurate the dart is. Some of my blasters sail and you could dodge it or even catch it with your hands, and other blasters zing to 40+ft with no drop with no chance of dodging it, using elite streamlines of course. I also pain/welt test my blasters, being shot around 10ft away to make sure im not hurting anyone, cause I do war with my nephews and nieces sometimes and I don't wanna hurt little kids.

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  3. I think if one can test FPS they should. At shoulder height a dart will take the exact amount of time to hit the ground regardless of FPS so you can calculate the best possible range the blaster can get with no outside variables affecting it. Disks kind of need range test because the range comes from gliding not velocity with them.

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  4. If you don't have a chrono, and are in Europe I offer a testing service for any blaster, from £3 excluding rtn postage. Range tests are not comparative, you simply cannot create exactly the same conditions all over the world. Chrono testing is basically the same wherever you are, provided you use the same ammo (we are standardised on the production Elite) and shoot a good sized sample (30 darts plus) you can compare with other modders without cheating, as well as properly testing aftermarket parts.

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