I will be there.

Nice work!

However, I think it could be simplified by using a design like this. All you would need to do is switch around a few tubing sizes, to make it nerf-sized, and hook that up to your valve, in place of your existing mechanism.

EDIT: I noticed that air is being released as long as the trigger is held down. Adding a semi-auto valve, like Zero's could lead to greater efficiency.

Hey, look, I'm the first one to comment.

Anyways, I like it. It kinda reminds me of a giraffe...

UPDATE
Upon further testing I realized sometimes the balster wouldn't fire and the problem was the O-ring got stuck in the PVC and was just sliding around on the well nut. The solution to this is to superglue your o-ring on.

I really don't suggest using super glue on an O-ring, it tends to shorten the life of the rubber. I'd suggest something more rubbery, like silicone, or even hot glue. I'm sure Goop/E-6000 would work just as well.

You're welcome! I like the overall simplicity of the system.

You should do an animal poll.

Sorry for the tangent, but it just struck me as a giraffe, for some reason. Apparently, other people agree with me, because "Giraffe" is winning by two votes. I think it would look more like a giraffe if the distance from the tee to the elbow was increased, but I digress.

Back on topic, I'd really like to see some pictures of a completed blaster with a pump...

The prices reflect the labor rate of a typical prototype shop. They do not (and cannot) run large-volume production, so individual unit costs are relatively high due to the lack of automation and need for a lot of hand-finishing. I do not agree with the design of their metal boltsleds, because they're literally designed to fail above certain spring loads. They're also designed to be as cheap as possible to manufacture, which is why they come in multiple pieces that are screwed together.


I do not agree with all of the production methods they use, because there are definitely more efficient and less expensive ways to produce higher quality parts on the scale that they're currently doing. They are still pretty much the only mod kit supplier that is capable of doing all of their production in-house, and they're one of the only ones that offers machined metal parts. OMW's metal parts are die cast, which significantly reduces the overall strength due to the materials available for the process and an inconsistent grain structure as a result of multiple production factors. Mine are currently outsourced to a machine shop in China because I'm too busy with school to do the machining myself (but they have faster machines than I do anyway).

I've heard their shotgun grips have been dropping in quality because their molds are wearing out, causing flashing and poor finish on the parts. You'd think they'd just make another mold set, but I guess Heng doesn't want to do that...

I don't mean to hijack the thread, but since the Big Salvo was mentioned from the start, I'd like to know if there is any significant body of work here on NH on the topic of piston type homemade valves. Like the valves used in SSPB, TS, Hornet, BigSalvo, SMDTG, etc., etc.

I'd really appreciate a few links or even suggestions what to search for, rather than to divert this thread away from sleeved-pin valves. I too was unable to solve the sleeve sealing problem in a way suitable for regular folks to make copies. But I still hope someone can.

By the way, I did build one where the sleeve was eliminated by using a solenoid to pull the valve open. Really cool, very effective, and at that time, the parts could easily be bought mail-order. Anyone who likes spending $50 and carrying around six D-cells (e.g., a Vulcan) might like my idea ... yeah, exactly my conclusion -- maybe for spudguns, but not practical for nerf.

I think this might be what you're looking for. The inline valve could probably be built for $20-30, and it would have a much better flow rate than a QEV. I think there was a thread on spudfiles about making an inline piston valve from an empty deodorant can. While that may be a little big for nerf guns, it could certainly be scaled down to the size you need.

I don't think anyone has mentioned it on this forum, but a few months ago, I discovered thickwall PETG in 4' lengths on Mcmaster, in the packing and shipping section. I posted it on NRev, but I don't think too many people noticed it.

It's part number 2044T43, and is slightly less expensive per foot than it is from members of the NIC. The 4' length is useful for applications where barrels greater than 12" long are necessary.

I know the Marshmallow Blaster is like that, but I thought the Mazooka was an inverted swing check valve. There's only a little plastic nub sticking off the trigger in front of the chamber, and when you pull that, the pressure beats the small torsion spring and forces it open.

That's still the same concept; it just uses a flap instead of a piston.

That is identical in function to my SCUNBAG. So yes, it can be made pretty easily.

I like the way it seals. I might have to alter my design, since it seems that a sealing face like that would be easier to make.

EDIT: Of course, if you really wanted one like that, I could definitely make you something out of aluminum or Delrin. The main advantage of a SCUNBAG is that it can be made without a lathe. I only used mine when I made it to clean up some faces, just so it would look slightly nicer.

Well then I need to re-read is a few more times, because I still don't get it.

You don't get how to assemble it, or you don't get how it works? The CAD model at the bottom shows a cutaway of all the parts installed.

I like how the scunbag can be made without a lathe, but it seems alot more complex than this in terms of number of steps to build it.

No, it's really not - I just broke it down into many steps, so that people could better understand how to put it together, since it's something that hasn't really been done in the homemade world before.

In an actual silencer, there is a baffle to slow down the escaping gases from the gun. This would make it impractical for nerf guns, since the pneumatics are almost silent, and it wouldn't do much to a springer. There is a silencer design in the "homemades" directory by Zero. This may help. However, we aren't dealing with noise in the first place, so it probably would be just for aesthetic appeal. You really don't need a silencer for anything other than an air cannon, unless you have huge amounts of air exiting your barrel at a very high speed.

EDIT: You might want to fix your spelling and grammar before the mods get here.

What kind of batteries does it use? I'm assuming gell-cells, but I could be, and most likely am wrong. The new lithium A123 cells would make this thing so much lighter, and you would be able to go farther on a single charge.

Won't be able to make it this time around. Robotics competitions for the next two weeks.

I'll try to be at this one. I think my dad wants to have a barbeque or something, but I'll see if he can move it to the next day.

Oh if you bring the tanks we talked about, I can buy them there. If I can convince my buddy to come with, that is haha.

I'll see if I can have them ready by then.

I'm coming.

Should be there, and ready to unveil a new game type that Mr.Apollo and I have been working on.

Ooh, sounds fun!

this may be because i've only moded my scout

If you've only modded your Scout, then it probably isn't a good idea to jump in and mod your Vulcan.

I was hopeing to increase some range because im only getting some were around 15'' (eye balled it so it may be more or less) with stock.

15" doesn't sound right for a Vulcan. Mine gets around 35 ft right out of the box!

Dude, don't tape it down. That tape will never hold. It only takes a couple of minutes to clip the wires off of the switch, twist them together, and solder them. Then, you can tape the wires to the inside of the shell so they don't get caught in the mech.

Actually, this is pretty cool. Do you have an end date in mind? Even though it's not at all nerf, I really want to see a video of it shooting. How long will the charge time be for the capacitor bank? Are you running this off of a 220V outlet, or are you stepping the voltage up from the battery pack, and if so, will the pack be able to supply enough current for sustained firing?

EDIT: Just noticed the "100% Portable" note at the top.

It would really help me if the image was bigger - I can't read the text around it.
From what you've said, your problem could stem from the grommet not being tight enough around the pin. You probably need to make the counterbore where the grommet goes slightly smaller, which means that you'll most likely have to re-make the entire thing. A lathe would be quite helpful.

I guess that as long as you can see the picture, I can fill you in on the problem area (the rest doesn't matter.) Basically the main valve ID is 7/16in then it tapers to 1/4in and then it expands to 1/2in to fit in the grommet. It has friction between the firing pin and the grommet already, and the surface area of the ID of the grommet is about an 1/8in deep. I don't have access to a lathe, and I don't really want to have to spend alot of money to get it custom made. I know you do custom work for a relatively cheap price, but it's still an expense I'd like to avoid.

I see. If I correctly understand what Ricochet is saying, he's suggesting a second set of o-rings on the stem. This a a really good idea, as it is easier to implement, especially if you've used a bolt and standoff as your pin. All you'd need to do is make another o-ring "sandwich," like you did before, and install it on the other end of the rod. This would necessitate the removal of the area that normally holds the grommet in place, but should make the valve much easier to produce, should you ever need to make another.

(I hope I put up the image the right way.) (why is this so hard?)

I'm having trouble with the grommet's seal on the valve I'm making. I epoxied it into place and the seal will hold up to 20 psi. After that, it leaks from the area between the standoff and the ID of the grommet. How can I fix this? I'm out of delrin so I hope to fix this without having to remachine the whole thing. Perhaps the trouble is because I made this on a drill press instead of a lathe, possibly causing a slight misalignment.

[IMG]http://i1208.photobucket.com/albums/cc374/lighthawk2/ValveDiagram.jpg[/IMG]

Copy/paste that in place of the broken image code in your post.

It would really help me if the image was bigger - I can't read the text around it.
From what you've said, your problem could stem from the grommet not being tight enough around the pin. You probably need to make the counterbore where the grommet goes slightly smaller, which means that you'll most likely have to re-make the entire thing. A lathe would be quite helpful.

For the record, the protected cells have circuitry inside of them to limit the maximum current output of each cell - this is done because lithium batteries can explode or catch on fire if they're discharged too quickly. For our purposes, it's fine to use the unprotected cells, because the protection has a fairly high safety factor built into it, which limits the maximum current draw to less than a desirable level for electric blasters. The protection also limits the minimum cell voltage, so you don't permanently damage your batteries (or cause a fire) by taking the cell voltage below the absolute minimum for the battery chemistry. Lithium batteries are very picky and can tend to be volatile, but if you're reasonably careful, you'll be fine.

I'm down to go if I can figure out how to get there (basically dependent on how much money I have for a train/bus ticket at that point in time). I would need lodging if you guys are willing to provide it to me.

Interesting. I wonder if the wax would help prevent the oxidation on my aluminum barrels...

That looks quite nice. Does the wax lubricate the brass?

I think it's expanded PVC (Sintra), or polycarbonate.

Wow, I'm glad you all liked it so much. It really has been a very fun project to work on.


roboman


The piston motor must have a motor brake in order to stop fast enough that you only fire 1 dart. I did some testing to see just how effective the brake was. I ran the motor at full speed for 1 revolution, and then let it coast. After that single revolution, it coasted 2 and a half more without power.

So far I have been using a micro relay to engage the motor brake, and a MOSFETT to control the speed of the motor. I'm going to experiment with an H-Bridge for two reasons. First, it has a built in braking system that unlike the micro relay, will not interfere with communications between the Arduino and the Max7219 LED controller. Second, I am considering using reverse to stop the motor even faster than the motor brake could. (Yes, I know this will put a lot of stress on the motor.)


Both Bee-Ri & roboman



Code code code... I'm really thinking about it guys. On the one hand, I love to help others and explain everything away. But on the other, I'm hoping to sell this, and hopefully pay for my Nerf/electrical hobby. If I can bring in enough income, I'll keep modding more blasters.

I'll let you guys know what I decide on. As an alternative, I might make an in-depth article about programming though.

Good news though, my H-Bridges came in today, so I'll be experimenting with them shortly! Thank you all for your compliments and input. Like I said, I think Nerf and I will have a bright and fun future together.

I guess that makes sense. I was planning on retaining the original piston reset switch so I don't have to worry about braking or anything, since it shorts the motor contacts and does the same thing that you're doing with an H-bridge. The reverse is an interesting idea, though it will be interesting to see how you wind up applying it during the firing cycle, because if it's wrong, it obviously just won't work right.

As for the code, I understand where you're coming from, but keep in mind that your code will only work on your setup unless someone manages to exactly copy what you did, and the people who are willing to put the time and effort into building one of these or even something similar generally aren't going to be interested in paying you to do it, so releasing your code just helps the community build cooler stuff and improve on what you did. Besides, you're gonna have competition from me in about a month or so in the form of drop-in modular kits, regardless of whether your code is public or not, since I don't even work in the same language that you used; I'm just interested in seeing what you did because I like reading through that kind of thing.

Damn, you beat me to it. This is pretty much exactly what I've been (very slowly) working on for quite some time, though I'm planning on going with the custom PCB route to entirely replace the trigger assembly and eliminate most of the wires you have running through the shell. Why are you planning on replacing the power transistors with an H-bridge? You shouldn't ever have to reverse any of the motors, so a power transistor should work just fine.

Would you mind posting your code or a link to Github or something? I'm interested to see how you did it.

I used the #62 spring in my SNAPs, and a 5 year old could prime it (not kidding!). Unless your brother is weaker than a kindergartener, I think he'll be able to cock it.

BTW: You can take the AT2K up to 7 pumps. I do that regularly, and have not had any problems.

[ If you decide to use the bow arms , you must reinforce the part where they go into the main body of the gun.

Why would you need to do that? They're not load-bearing structures... They're only there for aesthetics.

There are no gears in an AT2K. I'm assuming, by "gear," that you're referencing the knurled shaft that runs through the center of the turret.

Basically, you can't buy that part. If you own or have access to a decent lathe, you could make your own with a knurling tool. Seeing as most people don't, I'm going to make the assumption that you can be lumped into the "lathe-less" category, as well.

Also, that shaft appears to be made of stainless steel, which is very difficult to machine without proper tooling. I highly doubt you could find/make a replacement part for less than the cost of a new turret.

Nice writeup! Having seen (and been shot by) this before, I can attest to its power.

I like the cleanliness of the mod quite a bit.

All of the Nerf attachments rely on spring-loaded clips to hold their attachments to the rails. This removes the need for a truly standardized system, since their attachments can account for slight variations between blasters.

Dammit Matt, this couldn't be a week later? I'll actually be in town for this one, but I'll be at an archery competition through that weekend, so there's about a 99% chance I won't be making it. Any idea if there'll be an official SCUN event before 'geddon (or has South Pas finally been thrown into the 'official' war site rotation)?

You do have a motor controller for that thing, right (unless there's a built-in controller that the trigger switch just activates)? If there isn't one in there, the arduino can only source something like 20mA from the I/O pins, which is not nearly enough to drive that motor. You'll need a power transistor or a relay to drive that thing, most likely.

You might also want to consider a switch to detect the position of the plunger at the extremes of its travel, so you don't have to rely on timing to get the cycle correct.

I've done something similar with an arduino, using a push button as a mode switch of sorts. You're definitely going to want to set up that button as an interrupt, so that it stops the program and executes the section of code that changes the mode from safe to shoot. Otherwise, it'll be very hit-or-miss, so to speak, and may not reliably switch modes.