Semi-Auto Longshot 2

Some of you reading this may remember my last shenanigan, there were some issues with the design and I decided to scrap the pneumatic bolt altogether for my second attempt. I honestly have no idea how much the last longshot cost, I kinda just stopped counting after a while. This blaster is still a work in progress, attempting to juggle this project /school/ HvZ/ Senior design is rather difficult. This instructable will be updated several times in the coming weeks, but I hoped that the progress so far would be enough to enter the Epilog contest. Alright enough about this... on to the technical details!

• Raw materials you'll need:
• 3/8" thick acrylic sheet (Mcmaster P/N-8774K41)
• 5/8 Diameter metal rod, I'll explain later
• #10-32 Soc Hd cap screws (Mcmaster P/N-90128A940)
• 1/4-20 Soc Hd set scr (Mcmaster P/N-91375A533)
• #5-40 Soc Hd cap screws (Mcmaster P/N-91251A130)
• 0.5" DIA X 12" Lg PVC pipe (98 cents at Home depot)
• .5" x .5" x 1" piece of aluminum/CRS
• .25 x .25 x 2" piece of aluminum/CRS

This is all necessary to begin the mechanical fabrication, feel free to substitute any or all the fasteners to suit whatever you have on hand as these are just the sizes I used on mine. Just to give you an idea of what we will be constructing see the images below. Next up, manufacturing!

Oh and to give you a taste of the firing rate check this video out, it misfired a few times but that is just because the stepper motor limit switches weren't wired up yet. 

This build was really inspired by Mass Effect 2, I've always loved how the LS resembled the M-15 vindicator style gun from ME2. I know there are definitive visual differences between the Long shot and the M15-Vindicator but I hope that once completed they will look very similar. As the organizer for my universities HvZ game I play as the Commander NPC "Commander Shepard," so i felt that an M-15 vindicator would be a worthy blaster to wield =). 

Here is an update video, the motors are running at 1/4 power which is why the dart velocity is a bit low. Once the boost converter is finished I'll take a video showing it operating at full power.  Enjoy!

Step 1: Flywheel assembly

So you got all your parts together and scrounged for material, whats next? Manufacturing! The key to this blaster being a success is to take your time, when you start to make mistakes stop and take a break. It's better to stop and pick it up another day than to ruin all your hard work and have to start over. 

Below you will find a zipped folder containing bother .iges files as well as 1:1 PDFs. All you really have to do is print them out, stick them on, and start cutting/drilling. But DON'T FORGET THE SAFETY GLASSES.... seriously, hot plastic/metal will permanently injure your eyes. 

You will NEED the following tools:

• A cutting device (Ie. Table saw, band saw, dremel, hacksaw... etc)
• A drill press or drill (drill press is preferred)
• #10-32 tap and tap drill
• 1/4-20 tap and tap drill
• Sand paper

The following tools are what I used:

• Band saw
• Standard 3 axis manual milling machine
• Standard engine lathe
• Dremel
• #10-32 tap and tap drill
• 1/4-20 tap and tap drill
• 1/2 DIA drill bit
• 27/32 DIA drill bit
• Sand paper

1. Begin by cutting out all your blanks, Check the drawings provided. Make sure to make everything as accurate as possible, this will drastically reduce your headaches later on. See the images below of assembly and reference. The PVC breech was cut by hand using a Dremel (Abrasive cutoff wheel and grinding wheel)  and adjusted to fit the magazine and flywheels. The pockets in the carrier plate were designed for these motors (Tamiya Torque tuned motor) but any small rc motor will do. I would suggest that you drill and tap all the holes in the barrel mounts (with the exclusion of the hole for the barrel). Next, drill and counterbore the holes in the main carrier plate.Once everything is drilled and lined up, screw the assembly together and drill/cut the main bore for the barrel to sit in. 
2. The second phase is to manufacture the flywheels, the reason they are metallic is because you will need to install set screws to keep the shaft of the motor from spinning freely, and unless you are careful you will strip the threads out. I used #3-48 set screws, you could also glue the wheels on if you don't feel comfortable working with small taps. If you do not have access to a lathe you can use the  5/8" diameter rod as it is, and simply use a drill press to drill the hole (It won't be accurate, but it will work). The only issue with using the rod without turning it down is that you will have to alter the barrel more. You don't really need to rough the wheels up or add any e-tape/rubber, they will grab the dart just fine. 
3. The third step is to make the loading mechanism. This will be slightly more tricky as you will need to machine the OD of the rod down to properly fit inside of the barrel, or simply scrounge for material that fits. The crank and linkage are very simple to manufacture, but the entire assembly will need to be sanded to ensure that all the parts slide freely. Once again, these parts are most easily made from aluminum, but plastic could be used if you can't get your hands on anything else. 

Comments

[Nuvasuper]

Why do you use a stepper motor instead of a setup where the motor lines up with the piston and can run continuously? I don't know the proper term, but something like this: http://www.botskool.com/images/mech/mech19.jpg

[wcavanagh]

I would imagine using a push-type solonoid actuator would be easier / cheaper (and easier to fit inside the case better) than the stepper motor.

[Philysteak527]

Depends on the force required, not to mention solenoids generally have a very short stroke.

[Quertyman]

I've been looking around for a dremal, would this one work and what tip do I need for it to cut PVC. http://www.amazon.com/Dremel-7300-N-MiniMite-4-8-Volt-Two-Speed/dp/B003TU0XFU

[curious youth]

really any rotary tool will work. all you need to cut pvc is a cut off wheel. but try to stay at a low/medium speed for pvc. only because its a plastic and melts at a high speed

[Philysteak527]

Like curious said, PVC melts very easily so you will want to get a feel for how fast you can cut with things like abrasive discs. Although at times it is beneficial that it melts, much easier to clean up a bit of melted plastic off your part with a utility knife than drag out a vacuum cleaner (In my opinion at least).

[rickkix]

This stuff is awesome. Not to be rude, but why waste your time making a semi? You should try something like making a minigun out of a Vulcan or something like that.

[Philysteak527]

This isn't just a semi-automatic blaster, being it is fed with a motor it can fire in full auto or burst modes.

Check out one of the demo videos, you'll see it isn't strictly semi-auto.

[Madmartigan95]

This is amazing. I am totally adding flywheels to mine.
(i have a spectre so this may be pretty odd, but I think it will work out.)
Keep up the ideas, they're awesome!

[jumpingcat]

i like it pwns

[joh54]

You should make a full auto recon
That would pwn

[jongscx]

Just got a recon shell from a friend, I'm workin on that now...

[joh54]

awsome

[Philysteak527]

This system will fit into pretty much any clip system blaster =)

[nicwitzke]

Do you really need an arduino? Couldn't you just make it have a series of hinges, and only use one micro switch for the trigger

[jongscx]

An arduino seems like overkill for this project...I guess it's a necessity for the stepper motor, but jeez. Maybe add an ammo-counter that resets when a new clip is added.

I've never been a fan of flywheel systems. I think a nerf gun should use air... but that's just me. How long do you need to wait for the wheels to spool to firing speed? is there where the 4 rps figure comes from? In any case, I love that you have the two variants of longshots, very cool work!

[TSC]

Thanks for makeing theses there so cool! I would like to build one some time!

[Musicman41]

I think I understand your firing mechanism but I am not sure. It looks to me like you feed the darts through two powered wheels. It looks like the turning of these wheels is what propels the dart out of the barrel. Is this correct, or am I missing something, or is something not included yet?

[cowscankill]

From what I can see also, that seems correct...

[Philysteak527]

That is correct, it works on a similar principal to a baseball launcher.

[cowscankill]

Thought so, it's a very good design, great write up. Actually, after seeing this I whipped out my Recon CS-6. I think I'm going to more mods than I did before ;)

[taowyman]

what do you think is the hardest nerf gun to mod

[Philysteak527]

Good to hear it cows, you would be surprised at the useful things you can come up with when modifying these toys. Not to mention you can use the skills you learn and apply them to a multitude of projects.

If I had to pick one i'd say the new dart tag line with the built in mags, they are incredibly complicated to even disassemble.

[Morte_Moya]

Windcalmer from the forum here. This is a really great write-up. I love the flywheel design. Simple and looks to be VERY strong.

[taowyman]

would you sell this and how much

[Philysteak527]

I'd like to offer some hobby services if I win the Epolog laser cutter. I'd be willing to sell the mechanical portion of this blaster in a kit for about $20-$25, as well as a few other assorted robotics kits.

Other than the mechanical part you should expect to spend around 40-50 on the electronics.

[taowyman]

cool ill think about getting this and hopefully i can find some more money:P

[Iridium7]

Just a little FYI but, This would be fully automatic. "semi-auto" is actually called 3-round burst or just burst. Real semi-auto is just the way it comes stock, can also be called single shot. Not meaning to be rude, there's just a bit of a difference.

[l3owzaaaah]

I'm pretty sure with semi auto it's just as fast as you pull the trigger. A single shot is different as you need to prime the gun bolt between each shot. Hence the name bolt action.

[zippydaspinhead]

I agree with you in principle... but the accepted 'slang' if you will is that it is originally considered a bolt action or single shot, semi automatic is what you would call an auto-loader, or a weapon that fires every time you pull the trigger, without having to cycle a bullet into the chamber, with automatic meaning to be able to hold the trigger for continuous fire.

Since this is the normal 'slang' I would accept his use of it since 90% of the populace thinks like that instead of the 'proper' way.

If it looks, thinks, and acts like a duck, its probably a duck.

[ilpug]

or maybe its a brant, and the observer doesn't know that.

[Philysteak527]

I agree that this would realistically be considered "full auto," but if you google "semi auto longshot" you'll find my mods. I'm really just trying to get people to see this.

[taowyman]

this is epic how much would u say it would cost if i have the gun?

[ilpug]

Amazing gun. I have been thinking along the lines of pneumatics for a nerf mod, but not a flywheel system. I personally think the longstrike is the best gun to mod, because it has a MASSIVE interior space to cram in all kinds of parts.

[Philysteak527]

Got ya covered ;)

http://www.instructables.com/id/Semi-Automatic-NERF-Longshot/

[ilpug]

I saw that one. very nicely done, but a bit out of my price range, and i don't like dabbling with C02, because i have never had good luck with it. I might mod my lonestrike to use your flywheel system

[Philysteak527]

Flywheels are infinitely easier/cheaper to pull off than that CO2 system, not to mention there is alot of room for improvement and performance upgrades are easily installed.

[ilpug]

yeah, definetely going to do this, but what is the purpose of all the electronics? it seems that the whole system could operate with just a few switches. also, what is the range of this gun?

[Philysteak527]

I've only run the motors at 5v right now, once the boost converter is installed I can run it off of the 8v NiCad packs. Even at 5v it gets 30-32 feet average with stock streamlines, filling the tips with silicone increases range by about 8-10 feet. Can't wait to crank this baby up to full power.

[Electroinnovation]

I dont mean to be a grammer nazi but just so you know at the bottom of step four your wrote patients. I think you may have meant patience. Anyway I love this idea and hope you win the contest! 5* and sub!