Introduction: Nerf - Motorized Buzzsaw

This is a guide I wrote a few years ago for NerfHaven. I also wanted to share it here.

So I bought a Buzzsaw. I was pretty excited about it, it looked like a pretty cool gun. Turns out it wasn't as cool as I thought. I assumed that it was motorized, but you have to crank the thing to get it going. And you have to crank it ALOT to get any kind of decent range. And it's noisy as all hell. So, I decided to retire it to a good idea/poor execution kind of thing. Then I was digging through my closet and I found an old Tamiya R/C Car that hasn't seen use for a few years. IDEA!!

First things first, take apart the Buzzsaw. Do this by removing the twelve screws on the case. Lift off the case, and reveal the internals. Your next step is to remove the light blue crank rod thingy, and throw it away. We don't need it anymore.

Next, unscrew the two screws on the orange gearbox and expose the gears. It should look like the first image.

Now let's talk about how this gun works. It's actually pretty cool.

When you pull back the crank handle, teeth on the bottom catch on gear one. Gear one spins gear two, and the force of gear two spinning forces gear three down to engage the main gear which directly spins the drive wheel, which is what propels the balls out of the gun. When you stop pulling, a little spring pushes gear three out of contact with the drive gear, acting as a clutch and allowing you to pump back and forth while the drive wheel only spins one way. Pretty Sweet.

Step 1: Gears

Then I tore the motor out of the R/C car. Unfortunately, the pinion gear on the motor does not mesh with the nerf gears, so I had to find a substitute. Some might call it coincidence that a Lego gear meshes perfectly with the nerf gears. I call desitiny. Now I had to cut out the middle of the lego gear and kind of squish it onto the pinion gear, which works fine, for now, but I’m working on a more permanent solution. 

Next I mounted the motor to the orange panel that we removed earlier, lining up my new gear to mesh with gear two (I chose to remove gear one. Keeping it in might have increased the speed of the drive wheel, but it would also reduce torque. It was also easier to work without it). Take care to get these aligned and centered. If you don’t, you’ll generate a lot more friction, which will steal power from the gun. My motor has screw-mounting holes built in, so I just drilled three holes in the orange panel, two for screws and one for the drive shaft of the motor. Finished, it looks like Image 4.

Step 2: Mounting the Motor

I had to trim the orange panel to make space for the screws, but it was no big deal. Now on the main gearbox you have to cut out a space for your new gear to sit. Check out Image 1. 

Now, re-attach the orange panel with the newly mounted motor. Make sure that your gears will spin freely with as little grinding as possible. You may have to adjust your mounting holes. I know I did. Check Image 2 and 3.

Next, you have to cut a whole in the exterior case to accommodate the motor. I used a dremel for this. Dremels are invaluable. You should go buy one right now. Check Image 5. Then screw the shell back together.

Step 3: Finish!

Okay, so right now it’s pretty complicated and cumbersome. I need the speed controller to adjust the throttle of the motor. If I went from a dead stop to full speed the gears might grind and fly apart. I’m going to replace the electronic speed controller with a mechanical one so I won’t need the receiver. I will mount that to the gun along with the battery. I think that might make the gun a little more practical, but not by much. The thing feels like a gyroscope at full speed. Ranges are greatly increased. In fact the balls get so much backspin that they curve up at about twelve feet, so it’s not very accurate.

It is a lot of fun, though. Search Youtube users 'psyk' and 'JShoemaker97.' They've tackled this same project and have some really nice integration solutions. Thanks!