FANG 2: Prototype 1 fabrication part 2

Posted on 2009-03-18 23:14:25

Filed under fang2

It's been hard to motivate myself to do anything of importance this spring break, but I have seen a good deal of interest in finishing FANG 2 prototype 1 so I'll give it priority.

A few simple things need to be functionally complete:

A wooden handle needs to be made
New polycarbonate pieces holding the valve and air reservoir holder together need to be made. The current ones were meant to get a good idea of the dimensions (Yes, I am making some of this up as I go along).
Polycarbonate pieces to hold the turret front piece onto the tee right above it need to be made.
The turret needs to be lubricated.

When the blaster is functionally complete, it is not yet properly configured. I plan to make a homemade chronograph and set up a range of an arbitrary length with a video camera to determine at what time the dart hits a target. The muzzle velocity measured with the chronograph will determine the blaster's flow coefficient. The range will determine the dart's drag coefficient. This all is very rudimentary, but it should be reasonably accurate for what I intend to do.

From that point I'll decide what range I'd like the blaster to shoot. At the moment I'd like 95% of the shots to beat 100 feet. I don't know the standard deviation of the ranges of the shots I'll take--that'd involve too much to figure out and I wouldn't even be certain of it. cxwq at NerfHaven did however do some statistical analysis after modifying some Nerf blasters and I can use this data to see if there's any correlation between anything. There does seem to be a positive correlation between average range and standard deviation, which makes sense because longer range shots have the opportunity to deviate more. The correlation is rough at best likely due to inconsistencies in the blasters' muzzle velocities, but all I need is an approximate so this is very adequate.

More empirical data will be helpful in the future. This however is plenty adequate for prototype 1. In the future I intend to use significantly more statistics in the design process. Gathering data is dependent on having a prototype.

Solving the quick system of equations, I should shoot for an average range of about 113 feet for 95% of all shots to beat 100 feet.

With the desired range, a simulation can be run to determine the ideal dart mass. The ideal dart mass is the mass where the kinetic energy required to get a certain range is minimized.

That simulation also will provide a target muzzle velocity. Running BAGS I can then determine the best combinations of barrel length, operating pressure, and gas chamber volume. The "best" configuration here is one that gets a high number of shots per tank while being highly energy efficient.

Once the ideal configuration is known the blaster will be modified to those specifications. At this point the blaster will be tested at wars and its shortcomings will be noted and taken into account in a revision or new blaster.