loading
Simple way to measure fps using a camera and cardboard. your video camera takes a picture several times per second, if you know how fast id dose this then you can calculate speed my camera takes a picture 30 times per second (30 frames per second) if your camera is slower it will be less accurate and might not see projectile.
I shot my 180 fps airsoft gun and my camera got only 1frame of it. My 270 fps gun the camera did not see.
this is not to be judged in the launch it competition, its for the many people that could use this to improve their instructables
video on step 5

using some gestimation (fired sling shot and half way pulled back) i estimated the speed of my sling shot at 72 miles per hour (at full speed the camera didnt see any thing so i just multiplied by 2 i know its not accurate but it dosent have to be.)

the pics below:
it spent 4 frames on the lined part of board. after crunching the numbers the 14 gram projectile averaged 7.5fps (this is one of 5 tests) it was fired from my 7 gram torsion spring catapult

Step 1: Gather Materials

you will need:
a camera (at least 20 frames per second)
flat cardboard ( around 2 feet long 1 foot tall)
ruler (as long as cardboard is tall)
tape or thick marker (tape: blue scotch painters tape 1inch think)
pencil
calculator (recommended not needed)
tripod recommended
}}}

Step 2: Board Set Up

using a pencil and ruler mark 1 inch along the board
do the same for opposite side.

then draw a strait line across.

if using tape, tape right between the lines.

if using marker color between lines

if your board has little bit left over just put "spots" so you know its not a full inch

Step 3: Set Up.

I used a table vice to help hold card board in place (I didnt use the vice part of it through)
You could tape the board to a wall
I had to put a bucket of putt behind the board so it wouldnt tip over (I used putty because it was right sitting on the bench behind vice)

Keep in mind the angle of trajectory, catapults tend to fire at a high angle, sling shots k'nex guns airsoft guns Ect. Go relatively strait (duh)

Step 4: Set Up Camera and Projectile

you will need a tri-pod to get a good video

i used a heavy weight (2x as much as the catapult its self) this way it would go slower and would be easier to document for instructable.

Step 5: Fire/lanch/shoot/setoff/throw

After setting up tripod, set up the camera make sure its set to the highest frame rate possible.
Zoom in so you only see the board.
Get ready load/cock your weapon
Start filming, quickly fire your weapon into a safe backstop stop the camera
REPEAT 4+ times to rule out anomalies


Step 6: Computation

After you have taken the videos record the data
Go frame by frame in video,
1Count the number of frames the projectile flew over the board not the entire time its visible only when its on the marked part of board # will be referred to as A
2Record the distance the projectile flew over the board it should go strait across but the first test mine didnt # will be referred to as B
3And last, record how many inches it traveled in the fist frame # will be referred to as C

Now average every thing up so youre just working with the 1 set of what you did above. So you have one A, one B and, one C
The speed the camera records will be referred to D

The simple way I did this was CXD/12=Feet per second
EXSAMPLE 3X30=90 90/12=7.5=feetpersecond

So know you know approximately how fast it was traveling

Want to convert FPS to MPH?
Heres how
just multiply the fps by 0.6818 and your done!
want to convert to something else
check this out
lol my hand writing is just as bad all the time Someone who understands my language yay! lol
I can read that too.
someone has infiltrated my code....<br/><br/>i shall <em>destroy</em> you!<br/><br/>lol jk<br/>
No,I shall destroy <strong>you</strong><br/>
touche or however the hell you spell that... what with the accent and stuff...
The conversion isn't too hard, once you get one or the other side. Multiply f/s by 0.3048 to get m/s. Easy as pi.
Ha ha. pi
hey dude im trying to come up with a "standard" firepower idea that might be usefull to finding out the true power of a gun, what would you say the adverage of a normal blue rod shooting gun?, and one that fires through papper?
If yoy wanted this to be for cm pper second or km per second would you just make the gaps 1 cm wide ir is there something else? great instructable
Wow, I also wondered how the mythbusters do it. Although i'm too lazy to take the measurements and figure it out by my self. It's not all that hard.
this would work great with a high speed camera
yep it would i<strong>think</strong> they cost a couple hundred each, the idea here is you can do this with a digital camera with at least 30framspersec <br/><a rel="nofollow" href="http://www.photron.com/content.cfm?n=products&id=Mega%5FPixel%5Fat%5F1000%5Ffps%5Ffor%5Fthe%5FPC">here</a> are some hi-speed cameras<br/>
yeah i no did you get this idea from mythbusters because they use it alot
o, thats were i got it, i had this dream that i was using it to test some gun thing i made. next day i made this and i knew id seen it in the real world i just couldn't remember where. so yeah i guess i subconsciouly (sp) i did
whoa cool
no, that is too low, I think more like a thousand
Yeah, I agree with oinkoinkzoopals, it really should be done with a high-speed camera, that way when you are done you can take a whole bunch of cool high-speed footage afterwards, like popping a water balloon, or dropping a water droplet. And don't you know that you are supposed to do math in pencil?
that was pencil. origanly i had no plans of making an instructable so i didnt use a graph or bother with erasing cause it was for my dyslexic eyes only
that was pencil, it looks like pen to me.
i use dark .5 lead (graphite) the florescent lights above are making it look bluish
oh, I use .2, cause that is what the scantrons read
Well technically 1 frame is 29.97 FPS. So next time maybe crunch with that to get an exact. But it's a really good instructable.
iknow thats the standard but my camera has a 15 and a 30 setting. this isnt data used by nasa or any body elce but me and the few (10,000max) people that will read this. so i dont think its that big of a deal.
The video is hard to see - do you <em>have</em> to have the caption in the middle?<br/><br/>If it's the result of using a free version of some software, why not just use something like Windows Movie Maker?<br/>
yes unfortunately thats the only free software i have. mylaptop should have came with free software, it didnt i should be able to download it offline i cant i need to have an old version which i dont. thats the best i could do sorry
awsome instuctable i plan to try to use it on my next science project
lol a manual poor mans cronograph :-\

About This Instructable

9,734views

13favorites

License:

More by i make shooting things:Cleaning/Sharpening A folding knife A short clip to Critique: Helimax Novus Fp helicopter Test video. Rc plane basics 
Add instructable to: