Not considering how much juice your blaster pulls and having the alarm go off mid HVZ mission

Dude! use out-runners for the first stage!  Dropping to 2s wont help anything to be honest, i run my outrunner demolisher at 4s.

Good point about the closed cell foam, I hadn't even considered that. The plan was to just use the PVC pipe as the barrel with mylar over the ends. I will need to test this and might have to move to boomco straws if the closed cell foam is a problem. Someone mentioned that rival balls might hold up better so I will be testing those too once I finish hacking together a vacuum pump.
On a related note, turning a dart into foam confetti would definitely be interesting to watch...

I've been a spud gunner for 15 years. Those are pressures though, the goal of this is to evacuate the air from the chamber to avoid having to deal with air resistance. The pressures actually shouldn't be as dangerous since schedule 40 < 2" should be fine from what I've seen at a 27" vacuum which is where I'm going to limit it. I look forwatd to hearing what the other tato pumpkin guys have to say.

 

This is drawing inspiration from and from the Purdue University supersonic project https://youtu.be/YYNCGZCul1Q
 

In the never ending quest for more FPS, I've been toying with the idea of a vacuum cannon for firing nerf darts (possibly megas). I haven't been able to find anything solid about anyone having tried this so I'm looking for any experiences you guys may have.

I'm shooting for Mach 0.5 if I can pull a good enough vacuum and fit it in my Jeep so I'm aware that 500 fps darts are WAY beyond anything I could use during a war so this will be an exhibition peice.

Thoughts/comments/horror stories?

I looked around a bit and i dont know exactly yet.  I will probably pick up a rapid strike sometime soon and see what can fit in there.

Its available off github and that version is more current anyways. So for the rapidstrike, there are some interesting challenges with that.  If going with stock brushed motors, it will need to go through a relay board to control the flywheels and a separate controller to run a stepper motor to ensure the selct fire works correctly (just calling different numbers of steps depending on the mode)  I will try to whip up the code tomorrow and see how that goes.

Yes, it will require the use of a stepper motor though since continuous rotation servos are not terribly accurate and your won't get full auto out of a standard servo. I will update the github when I have time to write the code

I thought I would share some code I have cobbled together for controlling my brushless Stryfe with an arduino controller.  This allows for push button spin-up and you don't need to use a servo tester to control the motors which is always good.  Any suggestions are always welcome.   There is code included that allows you to hook a servo up to feed ammo into the flywheels for those of you who want to replace the pusher motors in your rapidstrikes with a servo.

 

Feel free to modify this like crazy and do all sorts of strange things with it.  This can be easily incorporated into ammo counters as well to have a single controller do both (any Arduino board is more than powerful enough to not blink at the task).

 

Latest version of code can always be found here: https://github.com/u...er/ArduNerf.ino

 

Code as of now:

 

//Arduino program to control a nerf blaster with brushless flywheels and a servo for feeding darts into the flywheels
//The pushbuttons I'm using in this example are OSEPP Push Button Modules  http://osepp.com/pro...-button-module/
//Arduino controller used during this development is an Intel Curie powered Arduino 101 https://www.arduino....ArduinoBoard101with an OSEPP SensorShield on top of it http://osepp.com/products/shield-arduino-compatible/sensor-shield/.  You will need to use OPTO ESCs and a seperate power feed for this setup!
//Also tested wih an ATMEGA2560 based Multiwii Flight Controller i had laying around http://www.readytoflyquads.com/multiwii-pro-2-0-flight-controller. To use this you will need to make sure one of your ESCs has a BEC built in.
//ESCs utilized here are http://www.hobbyking..._Firmware_.html.  


#include <Servo.h> //nice and simple, we are only utilizing one library for this project.  Servo handles everything we need it to

//declare servo objects that will be used throughout the rest of the project.
Servo ESC1;
Servo ESC2;
Servo feedServo;
//arm esc
// constants won't change. They're used here to
// set pin numbers:
const int spinButtonPin = 8;  // the number of the pin where the spin button is connected
const int feedButtonPin = 7;  // the number of the pin where the feed button is connected
const int ledPin = 13;      // the number of the LED pin
const int ESC1Pin = 5;      //piuninumber of the first ESC
const int ESC2Pin = 6;     //pin number of the second ESC
const int feedServoPin=9;  //pin number for the servo that will be pushing darts into the flywheels


// Variables will change:
int ledState = LOW;         // the current state of the output pin
int spinButtonState;             // used for storing the current reading from the spin input pin
int feedButtonState;             // used for storing the current reading from the feed input pin
int lastSpinButtonState = HIGH;   // the previous reading from the spin input pin - we instantiate it to the non-firing position to start the program
int lastFeedButtonState = HIGH;   // the previous reading from the feed input pin - we instantiate it to the non-firing position to start the program

//if not all your ESCs are the same, you may need an additonal variable but that shouldnt be necessary here.
int ESCMinSpeed = 1000;   //this varies by ESC.  Min speed must be low enough to arm.  Refer to speec controller's documentation for this
int ESCMaxSpeed = 1800;   //this varries by ESC.  You may want to set it slightly lower than the max supported to avoid overheating issues


void setup() {
  //setup the pins so we can use them for reading the button state.
  pinMode(spinButtonPin, INPUT);
  pinMode(feedButtonPin, INPUT);
  //set ledPin to output power to the LED
  pinMode(ledPin, OUTPUT);
  //set initial LED state
  digitalWrite(ledPin, ledState);
  //attach servos
  ESC1.attach(ESC1Pin);  
  ESC2.attach(ESC2Pin);
  feedServo.attach(feedServoPin);
  //write minimum speed to ESCs so they arm
  ESC1.writeMicroseconds(ESCMinSpeed);
  ESC2.writeMicroseconds(ESCMinSpeed);
  //wait 1 second for ESCs to arm
  delay(1000);
}

void loop() {
 
  // read the state of the switchs into a local variable:
  int spinReading = digitalRead(spinButtonPin);
  int feedReading = digitalRead(feedButtonPin);
 
      // check to see if you just pressed the button
      //only change speed if button state has changed
      if (spinReading != lastSpinButtonState) {
        if (spinReading == LOW) {
           ledState = HIGH;
           ESC1.writeMicroseconds(ESCMaxSpeed);
           ESC2.writeMicroseconds(ESCMaxSpeed);
        }
       if (spinReading == HIGH) {
          ledState = LOW;
          ESC1.writeMicroseconds(ESCMinSpeed);
          ESC2.writeMicroseconds(ESCMinSpeed);
        }
      }

      //if feed button has been pressed, start pushing darts out
      //What you write to the servos will vary greatly depending how you setup the feed mechanism.  
      //This example has the servo pushing a dart in when you push the button and then moving back to get ready to push the next one when yo let up on it.
      //In a rapidstrike or similar, you can just set ti to keep spinning while the button is pressed
      
      if (feedReading != lastFeedButtonState) {
        //if button is pressed, feed a dart in
        if (feedReading == LOW) {
          feedServo.write(180); //writes the server to full rotation
          }
        //return servo to the withdrawn state when button is released  
        if (feedReading == HIGH) {
          feedServo.write(0);
        }
      }
   
 
    // save the reading.  Next time through the loop,
    // it'll be the lastButtonState:
    lastSpinButtonState = spinReading;
    lastFeedButtonState = feedReading;
 
  // set the LED:
  digitalWrite(ledPin, ledState);

}

 

I attempted to attach the .ino file but the forums don't seem to be a big fan