AGD, All - Finally can chrono 10+ BPS and more!!!

[cledford]

All,

A while back I made the following post regarding the chronographing of shot strings in the 10BPS range and up. The link to my previous post is:

http://www.automags.org/forums/showthread.php?s=&threadid=22430

I am interested in determining the consistency between shots with modern electro guns, especially under rapid-fire conditions. (In my opinion the true root of all paintgun accuracy or inaccuracy.)

After some research it appeared that standard chronos were incapable of recording shot-strings from modern paintguns, especially at sub-second spit times.

I found (actually had already) a computer controlled chronograph, but wasn't sure if it would be able to record the strings I wanted to test, and living in an urban area it is also a pain to get out and setup everything for a test - since I have to drive 45 minutes to a field. (keep in mind that usually you must do chrongraphing outside because sunlight is needed for the instrument.) The manufacturer claimed to be able to record M-16 strings when firing on full-auto –which would be at east 10 shots per second.

I never ended up conducting a test until this weekend, as it’s just been too much of a pain to drag everything down to Pev’s. It turns out that my chronograph manufacture has produced an infrared light adapter kit for the system (to allow use indoors), which allowed my to setup a test site in the privacy of my garage. Last week I purchased the kit.

I have been testing this weekend with my Bob Long Timmy, and the chronograph is recording accurately the shot count (and presumably the velocities) of 3 and 6 round bursts at 14Bps. It has not missed a single ball out of a single string, and has even caught a couple of breaks.

I think a great tool is on hand for finally getting a better idea of consistency with paintguns - let the testing begin! On of the cool things about the chrono is that it can data-link to a PC, and there is even a Windows app for easy downloading of the information.

I'll post more about the setup (and photos) in the near future, for now checkout my previous post, or email me at cledford@cw.net.

-Calvin

[manike]

I wonder if they do mail order...? :D

Does it also give you the time between shots? or is just giving you a list of velocities?

If you got the time between shots as well and then could relate that to the velocities it would be very interesting and I see limitless experiments on the horizon... :)

manike

[cledford]

Manike,

Checked it yesterday - sorry it doesn't do split-times, or times between shots. I guess this is so that the system doesn't compete with their timer product.

It does do a great job of recording the shot strings, and will hold up to 200 in memory - even after being turned off.

It has a review button, a standard deviation calculator, and will tell you the low/high/average velocities of a string. Also it will allow you to omit shots from a string once, or delete them from memory, and even has a voice that will audibly call out the FPS of a shot! All in all it's a great product, the only problems I'm finding are:

1. It's telling me things I'm not too crazy about. I.e. I figure I can do +/- 10bps with my finger on semi. I've be chronoing strings from the Timmy on full-auto (actually 6rnd burst to insure that I’m catching all the shots and not missing any) at 10bps and even with a Palmer Stab the consistency sucks. (I'm shooting Inferno with a matched Freak) Sometimes you'll see standard deviations of 2-4 FPS, but at rapid fire, it's usually 8 - which equals a big spread in velocities. I’m switching back and forth between 10Bps and 14 – with no apparent change in performance of the gun, or the chrono – it keeps up!

2. Mess. Chronoing indoors is just plain messy. Even with a trap that shreds the balls, any break or chop sprays paint everywhere. You don't notice it at all outside, but it becomes apparent indoors - even in a garage. I’m kinda proud of my trap – I took a square plastic garbage can and filled the bottom 16 inches with absorbent material (old towels), then took half-inch screen and stapled it to a 2x4 frame that can be pushed down into the can and friction fits just above the fill. When the balls hit the screen they practically vaporize, and I’ve had no bounce back, fling, or spray from the trap it’s self – only slop from the breaks/chops that occur before the mass of the ball enters the trap.

Where in the UK are you living? I'll be back in London at the end of May for work - it might be cool to hook up if you’re up for it.

-Calvin

[cledford]

Here is a sample output of the shot strings that can be downloaded from the CED chronograph to your PC using the data-link. One of the cool things about the CED is that the data-link port is built into the chronograph, and uses a standard straight DB9 male to DB9 female serial cable that can be had from any electronics store for 10 bucks - this is vs. a lot of electronics vendors that use proprietary cables that require purchase of the over-priced device from them. The windows software app is free, or you can download the info into a hyper terminal session.

The attached strings are 6 round bursts shot at 14Bps from my Timmy with low pressure conversion, Palmer LP Stab, and AA Armageddon air system. The paint was Inferno matched to a SP Freak. As you can see - something ain't looking to good... The cool thing about information like this is that it will allow us a tool for tuning our guns, or demand better quality control from manufacturers. Obviously there will be some discrepancies when cycling anything up to 14 times a second - but I saw similar results at 10Bps - which I think is where most of the faster shooters are at in a game.

-Calvin

<snip>------------


GROUP #1
1) 286.6 8.8
2) 280.6 2.8
3) 264.2 -13.6 ƒ
4) 272.8 -5.0
5) 279.0 1.2
6) 286.8 9.0


7) 279.4 1.6
8) 278.2 0.4
9) 285.0 7.2
10) 272.0 -5.8
11) 285.0 7.2
12) 283.2 5.4


13) 288.6 10.8
14) 270.4 -7.4
15) 266.0 -11.8 ƒ
16) 269.8 -8.0
17) 273.0 -4.8
18) 282.0 4.2

High: 288.6
Low: 264.2
E.S.: 24.4
Ave.: 277.8
S.D.: 7.4

[cledford]

If you look closely at the output above - there are 2 numbers per line. (Sorry I could have made it easier to read if I'd put tabs in each line...) The first is the velocity, the second is the Standard Deviation from the then entire 18 shot group average velocity. Standard deviation is very cool, here is a write up that explains it. The information came from the product manual for the CED chronograph.

-Calvin

Standard Deviation - Based on the universal mathematical equation for uniformity, this function uses
all the data entries in a string to calculate the Standard Deviation of the combined shots / velocities in
that string. The larger the number of data entries in the string, the more accurate the SD becomes. The
CED Millennium requires a minimum of 5 shots / velocities to be received in order to calculate SD.
However, it should be noted that the more data entries used in SD calculations, the more reliable the SD
will actually be. Statisticians usually recommend 20 shots / velocities for the best reliable results. Edited
or omitted entries will not be included in SD calculations.
Standard deviation is very confusing to many people and as such, is not often used. However, in reality,
it is the best textbook measure of velocity uniformity available and when used properly and in conjunction
with other load data will give very meaningful results. Average velocity has been the standard for
years. However, it does not indicate how much the velocities being measured varied above and below
the average. The standard deviation actually measures how close each shot velocity will be to the
"average". The more uniform you can make the ammunition, the better the odds (no guarantees) that it
will produce the exact same results. The mathematical equation for standard deviation is extremely
complex and prior to electronic calculation (computers) it was seldom used by shooters. What it means
though, is that statistically, it has been proven that 68% of all things measured will fall between one
standard deviation above or below the average. Additionally, 95.4% will fall between two standard
deviations above or below, and 99.7% will fall between three standard deviations above or below the
average.

Example = If you have a standard deviation of 10 fps with an average velocity of 1000 fps, then you can
expect that 68% of the shots fired will fall within 990 fps to 1010 fps. Further, it can be determined that
95.4% of the shots fired will fall between 980 fps and 1020 fps and that almost all of the shots fired
(99.7%) will fall between 970 fps and 1030 fps.

[AGD]

Calvin,

Got your email and I have been monitoring this post. The problem here is that the paint varies pretty badly so unless you test multiple guns with the same paint on the same day it's hard to get a feel for what is gun and what is paint. In the shop we shoot nylon balls that are very round. It is not uncommon for us to shoot the same velocity within tenths of a fps for several shots. This is VERY rare when shooing real paint.

Pull up several guns and crono them at full speed with the same paint and post the results.

AGD