Nerf Gun Mod

You probably know Nerf Guns, every part is plastic (except for springs, motors... duh). I've decided that I want to modify a Nerf blaster I bought to be more powerful. Currently it fires about 20-30 feet... if you're lucky and if you're waiting for the motors to all the way back up (it uses a "flywheel" system to semi-automatically fire darts). Honestly, I never really bothered to look much at Shapeways until I got done with the parts, so I guess this is more or less an explanation of what I've done thus far.

I've taken my gun blaster apart and have stripped out the motor and wheel assembly pictured here (minus the wheels, I seem to have lost one..)

Motor mount as assembled in the blaster



What I plan on doing with Shapeways is to print a new version of the mount for the motors so that it accepts some larger motors I've purchased. Additionally, I plan on having a pair of new wheels printed for this because I had to change the spacing of the motors so that they would fit, not to mention the original wheels were too small to fit around the motor like the original placement.

Motor mount and wheel with new motor (left) and original motor (right).


Size of new motor compared to original motors in assembly


So far I've modeled the original mount (to make an accurate replacement) in Autodesk Inventor (the software I use for school) and used that to make the replacement. It's taken me a few weeks of on and off hobby work on it, but I have it finished.

Motor mount models side-by-side

After making that and easily making models of the motors, I used the replacement mount to then produce a set of wheels that would work in the assembly the same way the old wheels would, and from there I have my final assembly model.

Motors are in blue. Mount is in white. Wheels are in orange. Dart (being launched) is in cyan.



I am hoping to send the order in soon to get these (three) parts made, but converting the models seems to be giving me quite a bit of trouble, whenever I upload it, the dimensions turn out to be something absurd like a volume of 90.83cm^3 for one of the wheels when in Inventor I get a more moderate (and correct) volume of .338 in^3 (5.539 cm^3). I've tried uploading in multiple formats like .stl, .wrl, and .dae (via the recommended converter) and still none of them gives me the dimensions which I used in the design of each model. So at this point I guess I'm stuck and would really appreciate any help at all.

Get a copy of http://www.netfabb.com/basic.php
Export your model as STL
Open in Netfabb where you can check, measure, scale and repair your model.
WYSIWYG
If you change anything go to part - export part as STL

Thanks for the help. I got all of the confusing shenanigans worked out and everything seems to be correct involving dimensions between Inventor and Shapeway's system. All the parts are ordered and I'm excited to get to work on my project.

Glad to help. Nice modeling
Here's a freebie for you. Till April on Windows, no limit on a Mac
http://labs.autodesk.com/technologies/fusion

Cab one hallow out a tail with nettfabb? I really need help with that.

What are you trying to do exactly? It depends on what you mean by hollow out.

Oh, but you shouldn't answer here though, you should make a new thread about it so this thread can continue to stay on subject since the author will probably make updates when he receives the parts. Just post up a new thread with a description of what you're trying to do exactly and we can come see what you're up to.

College student kills man with augmented Nerf gun using 3D printed parts printed at Shapeways! NEWS AT ELEVEN! HAHAHA!!! :laughing:

Just kidding!

Nice mod! One thing I thought of while looking at your mod was, what if you angled the motors slightly, so that in addition to ejecting the dart, they also impart some spin to make the dart fly more accurately on its intended trajectory.

The thought crossed my mind at one point, but it would be difficult to get it perfectly right and not send the dart into the barrel. I was intending to up the range/power of the darts, I figured adding rifling/spin of any kind would merely complicate the project.

Yeah, you'd need at least three motors or idler wheels to facilitate alignment, so that would complicate things a bit. On the other hand, being that the darts weigh very little there would be minimal benefit provided by centrifugal forces.

maybe putting a rough texture on the wheels would allow them to grip the darts better for cancelling any slip. also using high power brushless motors would give higher speed. something like a 9000kv would really spit them out!... or even using several smaller gears (instead of one big wheel) to create more torque.

I'm using two Banebots RS 380 motors. They're 7.2v motors with a maximum RPM of 16,200 (with no load; 13,900 RPM peak efficiency) with a stall torque of 11.51 oz-in (1.92 oz-in peak efficiency). Considering the darts and comparing with the original motors (which I have no solid numbers for), these are much more powerful and should never slow down even with rapid firing (trigger pulling), whereas the originals would slow down significantly after the first shot. I don't think it would be necessary to use gears to slow down to increase the torque of the motors, no to mention how much more complex it would make the project.

Perhaps you could get a similar effect by using drive wheels with diagonal bars on? As in helical gears.

Very true, but there might be some drag reduction from the spin, giving increased speed/distance. I don't know what type of projectiles you use, but if they are un-aerodynamic, low-density foam cylinders you might get some good gains from relatively low rates of spin. An interesting line of enquiry.

Looking forward to seeing how this turns out.

I know you stick w/ the flywheel designs for semiauto firing, but have you played with the new NERF Retaliator blasters? I have one of those and the darts are wicked fast out of that thing, downside is at that speed they curve and are fairly inaccurate. fun nonetheless.

It's here.
*Meager attempt at villainous laugh*






I'm excited.

Will post update soon! I have a test to study for.

I'm excited too!

Danggg! Look at that! I can see the polygon facets on those cylinders! Amazing resolution!

Makes me want to make something mechanical in polyamide.

Yes looks good.
Now i want to see it asembled in the nerf!

Alright: I actually messed around with all of this yesterday, I just didn't get around to posting it like I wanted to. In other news I think I rocked that test I was studying for instead....


So anyway: I have yet to get a 7.2v (RC car, charges to roughly 8.5v) battery to put in the gun, so everything I've done has been off of four AA batteries (1.5~1.8v each, in series 6~7.2v). Additionally, I need to get screws to secure the motors in the mount, because currently they are only a snug fit in the opening I made for the motor's bearing.

Motor bearing snugly fits into the part, with some shaving of the material around the hole.

There's a few minor issues with the part I would want to point out if I ever make this public so long as it works:

Some of the box shapes on the bottom (that meet with the bottom part of the assembly), two of them are strangely inverted. The holes where the top part meets the bottom are a bit out of alignment, but these two aren't big deals, as you'll see later. The holes for the screws to mount the motors are almost non-existent, I had to punch them out from the small divots that they were. Finally, the holes for the motor bearings are just a smidge too small, I had to open them up a little bit with a small knife, no big deal.


After basically press-fitting the wheels onto the motor shafts (tight as they should be, albeit a little tough to get on), I found that the bottom piece of the motor assembly won't fit with the new wheels on, and the wheels have very little clearance and are nearly touching the outer shell, so I'll have to do without the bottom piece, which seems like no big deal.

The clearance between the two wheels is just enough to pinch the dart a little bit, so for that, I'm happy. On another note: the white strong and flexible material seems a tad bit abrasive to use against the darts, it's already skinned a bit off of one dart thus far.


So I've got the motors mounted and everything seems pretty lined up and I've tested the motors and they do work, so that won't be an issue. So for now, I'm just waiting on screws and a proper battery.





So for next time, I'll have all the wiring done, give the motors a good running test and I'll probably be evaluating the results of any testing I do.

Alright, so here's the pictures of the wiring done with it, I'll see about getting a video of it working up soon, but I'm having some issues with it shaking without having the screws I need so it's been firing a little awkwardly. I'll probably just take a video of the assembly I made shooting a dart, which I must say has been pretty impressive.





On another note: I've added electrical tape to the flywheels to increase grip and decrease abrasion.

This is awesome! You'll have to post some video of it!

Love this. nice little idea.
good design of the part also. well done. look forward to seeing more.