alternative weapons

[War Wolf]

I was reading some posts and came across a few on different weapons that people had posed or suggested and found it interesting. Most people seem to only want to compete in the air soft league, sadly all the creativity that people seem to have governing weapons design is stifled by their desire to only compete in this division. If reasonable safety precautions were taken to ensure the absolute security of these alternative weapons wouldn't it be feasible that these weapons be allowed in competition and not only allowed in hardcore class? Being that there is no mech warfare competition this year it would seem and there seems to be a lack of location for the competition as a whole , wouldn't a revision of the current rules be a help towards creating an improved event that would appeal to a larger audience so as to improve the hobby as a whole? This is just a thought there's no need to comment really. I just thought that a DC pump could safely fire bb's at another robot and that son people are more adept at making weapons than they are at making robots.

[jwatte]

I don't know about you, but I would not put $5,000 of servos into an arena with explosives or other physically-damaging weapons.

[artans]

There is quite a bit of a design challenge with designing a gun and shooting BBs at other mechs. Challenges include accuracy, weight, and loading of BBs. It may not give us a lot of creative freedom but from a engineering perspective, we (R-Team robotics club) enjoy the design challenge. In the couple of years that we've competed in the airsoft league, our resident gun expert in our club has been through many prototypes of different feeding and firing mechanisms.

[Th232]

Stepping back a bit, what kind of alternate weapons do you propose, and how do you plan to integrate them into scoring?

[tician]

If you are using airsoft BBs, there is not really any limit on how you propel them except that it cannot involve combustion and should not be so powerful as to damage the BB before it leaves the barrel. One of those weird projects I will probably never finish is using a little 12V (32psi, 12L/min.) diaphragm air/vacuum pump to power an airsoft revolver cannon. The hope was to also use that pump to control a few actuators for moving the mech, but most electronically controlled valves are still large, heavy and expensive.

[War Wolf]

This hobby can get overly expensive at times. Though cutting corners on cost for some people would be a sin.lord forbid that its a hobby for fun I would still hope and winning though yes is fun is not the name of the game. If I had the disposable income some of the other well to do competitors had available I would likely waste it on expensive parts . I do specifically mentioning reasonable safety precautions being implemented in the new weapon construction. The idea I was thinking about would in solve a DC fish tank pump feeding into a tank or directly as per a pneumatic tool in theory. This nay or nay not be feasible but as the title of the thread suggests it is an alternate weapon. I appreciate the feedback from all members who have posted.

[War Wolf]

To add if anyone knows of and lower cost entry level alternatives to allow beginners or newbies to be able to compete in the 2015 competition please message me the info would be greatly appreciated.

[War Wolf]

Forgive the poor spelling auto correct has a way with words lol

[ArduTank]

Compression like that would likely end in a DQ. (the pump alone may be fine, but not the air tank) Cheapest way I've found for weapons, is the crosman m74dp. You can find them at multiple places, and I know that my Meijer has them for $20 a piece. Cheap, simple. two wires and a little disassembly/reassembly.

[tician]

Compression like that would likely end in a DQ. (the pump alone may be fine, but not the air tank)

How do you figure that? Rules only prohibit CO2/N2 gas systems outside hardcore. CO2/N2 systems operate at hundreds to thousands of psi. Small aquarium pumps (which cannot safely run dry...) are lucky to get tens of psi as they are much like other water circulation pumps in operating at low pressure and high volume flow rates. The diaphragm air pump I have is rated 12W electric, so 50~70% efficiency in the cheap brushed DC motor+gearhead and 60~90% efficiency in the pump gives maybe 6W of power in compressed air. 6W = 6J/s, so in a perfect system, the pump would produce enough air power to accelerate six 0.2g BBs to 100m/s every second (far less if also using the pump to power the mech actuators).

And to ramble a bit more...
Assuming the air pump can actually maintain 30psi at all flow rates (hah!), the pump would provide enough air mass to maintain a constant pressure while the volume changes as the BB progresses down the barrel. If so, there would be a constant force acting on the 6mm BB of ~4N and, under perfect conditions, the maximum energy possibly imbued to a pellet in a 10" barrel would be about 1J (force acting over distance; 4N*.25m=1J). Actual energy is a bit less because of losses from displacing air in the barrel in front of the BB, friction from contact between the BB and barrel, and gas escaping around the BB. The mass of air propelling the BB is constant in a spring-loaded piston system, so the pressure (thus, force on the BB) varies with the volume of the mass of air between the moving piston head and the BB in the barrel. Since the air in the piston is at ambient pressure before firing and the BB is held in place with some force in the hopup, there is further energy loss to slight heating of the gas during compression before the pressure on the BB is sufficient to start propelling it down the barrel (temperature increases when compressed and some of the heat may be absorbed by piston and barrel before expansion can cause temperature to drop again).