I picked up a Nerf Vulcan last year soon after they went on sale, and it faithfully protected my cubicle and me for a few months. The Vulcan’s reign over the office came to an abrupt end when one of our MechEs rebuilt a Nerf Rocket launcher to shoot darts with 120 psi of compressed air. His gun was similar to this one, only red. Dubbed the law bringer, its reign was only briefly interrupted by my newly modified Vulcan.
Knowing that I couldn’t beat his velocity or range (over 100 yards), I decided to concentrate on rate of fire. A few people were reporting 500 rpm, and I managed to hit that easily with three 9.6V batteries wired in series. You can see a brief video of what 500 rpm looks like after the jump.
500 rpm wasn’t enough they said. The voices kept telling me I could go faster. One more battery won’t hurt they said. I pushed it to four batteries for a total of 38 volts or about 4x the stock battery pack. Nerf’s little toy motor managed to squeeze off exactly two chains of 25 darts in just over two seconds each. I’d attained 666 rpm. Then the smell hit me and I glanced down to see wisps of blue smoke coming from the gun.
As the photo shows, the generic toy motor didn’t care so much for the extra power and literally came unglued. The top of the motor twisted enough to make it loose, and there were bits of copper wire and carbon brushes rattling around inside the gun. I was slightly disappointed, but figured that it would be a good learning experience and a great excuse to shop on some online electronic surplus stores.
After carefully measuring the motor and scouring the web I ordered about a dozen toy motors of similar sizes from a few different surplus stores. For those interested, the motor is 32mm long, 27.6mm in diameter, and has a shaft diameter of 2.4mm. Electronic Goldmine and American Surplus both had good selections. In the end I picked the Molon CMO-1237. It’s a pretty standard motor and the only one to have clear markings on it. American Surplus has a pair of them for sale for $3.95. At 9V it is roughly 3/4 the speed of the stock motor, but it is strong enough and appears to handle the power better.
To compensate for a slightly slower motor I built a battery pack for three, and possibly four 9.6V batteries. I estimate the current rate of fire around 300 rpm. I’ll eventually get back up over 600 rpm and then I’m sure something else will break.
The VEX batteries are standard 9.6V NiCd RC batteries and you can find similar ones in most hobby stores. The connector is also standard and you can find both male and female ends cheap online.
There are a couple more photos of the gun, mod, and the like on this Flickr set: Nerf Vulcan