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#358907 Caliburn: Mag-fed Pump-action Springer

Posted by dskippy on 30 March 2017 - 09:23 AM in Homemades

It's going to stick out if you've got a square - it'd need to interface with the catch throughout the whole cycle, and the catch is basically also the stock buttplate here. It needs to be an omni-catch because it's also a floating catch, and it's tough to make a floating square PR. Even if you did, you might still need to omni-catch as you can't control the PR rotating in the cylinder if it's floating.

 

Oh right I forgot that the whole plunger is free to rotate.




#358901 Caliburn: Mag-fed Pump-action Springer

Posted by dskippy on 30 March 2017 - 12:15 AM in Homemades

An omni-directional floating plunger rod cannot be made from square stock because rotation would prevent it from fitting through a square hole. And you don't need a machine lathe for the plunger rod (but you do for the ramrod and bolt core), you just need to cut the ends squarely.

 

Yes an omni-directional floating plunger rod cannot be made from square stock... but if your plunger rod is square, and thus unable to rotate, it doesn't need to be omni directional, right?




#358886 Caliburn: Mag-fed Pump-action Springer

Posted by dskippy on 29 March 2017 - 04:02 PM in Homemades

This is amazing, CaptainSlug. Well done. I've been wanting to build a mag-fed, pump-action blaster for a while. Thanks for the great write up. I might try to implement this.

 

I have a question about the plunger rod. I notice you're goal is to reduce inner cuts with the scroll saw. Effectively reducing the difficulty in making the blaster. Inner cuts can definitely be pretty annoying to accomplish. But the rod plunger rod is also tricky because you need access to a machine lathe. I like to use square plunger rods because they're easier to make. They can be cut with a scroll saw and they don't rotate so they only need a notch on one side. I wonder if you've ever considered a reuleaux triangle drill bit. They allow you to drill square holes. Since the plunger rod is only one size, you'd only need one special reuleaux bit for the whole project. This might enable you to use a square rod and eliminate the machine lathe process.

 

I ask this mostly because I am considering doing just just if I duplicate your design. Not necessarily to try to sway you toward square rods yourself. I'm wondering if you have thought of this and think there's some reason to go with the round rod anyway or was it just not considered?

 

The reuleaux bit is a really nice solution that I think should be more well known in the NerfHaven community. There's a lot of square holes out there being cut with scroll saws. In general, most plunger rods are the same size too, so most nerfers would only need one bit total in their shop. I actually use an X-Carve CNC for my templated cuts so square is really not a big deal for me anyway.

 

Well thanks for the great write up! Looking forward to seeing any tweaks you make to it.




#350010 Air cylinder for pushing darts through clips.

Posted by dskippy on 15 December 2015 - 12:13 AM in Homemades

Hey guys,

 

I made some progress this weekend. Here's the printed out mag well.

 

magwell_zpsa9cxjqnb.png

 

The printed part came out alright, though it definitely needs some adjustments. The space for the magazine's directional tab is too small and the holes for the bolts too big. It will do just fine for the first round though.

 

I've also gotten the air cylinder, QEV, and DCV in the mail. Here's the basic setup for the first test.

 

setup_zps2ibwd65w.png

 

I need to make the inside of the chamber (the PVC tee joint) as laid out in this thread. I also need to machine the ram rod that I just got in the mail today. It's 9/16" Derlin rod that will go on the end of the air cylinder. Hopefully I'll have a video demonstration of the whole this working next weekend.




#349958 Air cylinder for pushing darts through clips.

Posted by dskippy on 11 December 2015 - 06:04 PM in Homemades

But, thinking about it more, friction takes over sometime before pressure equilibrium is reached let alone a vacuum is formed. Therefore, an ideal length barrel would never form a vacuum and opening/venting the chamber would do nothing.

 

Yes but in the context we were discussing this, we did not have an ideal barrel. We had a barrel that was too long and we were planning to put a measuring stick down the barrel to see how far it got. So the statement that a lack of a vacuum could potentially increase performance is valid. Though I definitely don't know how the lack of a vacuum vs. the friction would play out.

 

One thing I can do is find the ideal barrel length first by firmly sealing the back of the barrel and not allowing the ram to retract. After that is done, I could test performance in an ideal length barrel and see if performance is affected. 




#349923 Air cylinder for pushing darts through clips.

Posted by dskippy on 09 December 2015 - 10:51 AM in Homemades

Doing that should also give you a pretty good idea how long your real barrel should be for maximum efficiency.

 

And great work so far dskippy. You're putting a lot more quality and time into your build than I did. It should have a much better chance of succeeding than my attempt did.

 

Thanks for laying out that test plan. That sounds great, I'll do that. If I end up with an ideal barrel length that's way too short, I either need to increase my blast chamber volume or the ram is pulling out too quickly. So with an arbitrarily large blast chamber I'll be able to see exactly how long of a barrel my ram can handle.

 

Also thanks a bunch. I'm looking forward to it. I'm working on getting the prototype printed up and then bolted on to the air cylinder for a test. I'll be making the tee joint chamber fairly soon.




#349917 Air cylinder for pushing darts through clips.

Posted by dskippy on 09 December 2015 - 03:28 AM in Homemades

Picts? Sounds like you've got significant progress.

 

Here's a picture of the design. I got this finished tonight. I still haven't gotten it to a printer yet but I will pretty soon.

 

It should accept a 1/2" Sched-40 PVC tee joint (or really any 1/2" female joint) into that big hole in the top. There are four holes in the side for #6-32 screws which I'll use to mount this to some polycarb plates that I'll machine for the body. You can notice the little cutout on the inside in this photo for the directional indexing tab on N-Strike magazines. I have a print of an earlier draft which I'll try to find and post a picture of tomorrow.

 

magwell_zpso5ohgu6n.png




#349913 Air cylinder for pushing darts through clips.

Posted by dskippy on 08 December 2015 - 04:38 PM in Homemades

Instead of putting a single piece of PVC straight through the T, requiring you to bore out the T in the process, put 2 pieces in, one on either side of the parts you'd need to bore out. The piece towards the front of the blaster would be a few inches long to support the barrel and provide anchoring points for the T, the piece toward the rear wouldn't be more than 1" to just fill the hole in the T and attach to the mag well.

 

It sounds like you've got the design hammered out, how's physical progress coming? Have you ordered parts yet?

 

Ah! The two questions are related and I get you now. Okay so that would be a pretty straight-forward way to do this just with parts from the hardware store. Thanks for the tip. That might be the best chamber to mate with my mag well. There are some other interesting options. Machining a chamber out of a block of Delrin or PVC is actually pretty easy to do and might be the nicest final product. It's basically just three holes of different sizes drill from each end. Then one gets tapped for NPT and one gets chamfered. The other competing idea would be, as I said, to 3D print those parts all connected to the mag well. It's possible that I'll try all of these things. I'm going to try to make the PVC tee joint you guys are suggesting tonight though. Assuming I can find some thin-wall PVC. If not, as soon as I get some.

 

As for physical progress, things are going well. I have a prototype of the 3D printed mag well and it mates very nicely with the magazine and the dart pushes through beautifully. I'm quite happy with it so far. I order the air cylinder and it's in the mail, due very soon. I need to add a feature to the back of my mag well that mates with it ones I can play around with it physically.

 

 Sorry for the horrendous piant diagram:

Edit: Actually, I just remembered you are probably using Sch80 for your barrel...but hopefully you get the idea.
 
No, I'm the one that missed something. My idea won't work with a blowback design (which is what you are making).
 
If it comes to the point that you need to delay ram retraction, maybe look at thisfor some ideas.

 

Thank you for the horrendous paint diagram. ;) Yes, I understand this now. I may very well end up doing this for the chamber. I get the idea and I can adapt this to work with Sched-80 PVC for sure.

 

Glad we're on the same page with the blowback. I think that is all going to be considered after I have a prototype build and can see how well it functions including some range tests and maybe, if I'm lucky, some high-speed camera tests. Anyone have a better idea on how to test whether I'm getting enough overlap with the ram into the barrel without a high-speed camera?

 

Also, I've realized the ram is going to have an issue as I've designed it. The rod that extends out from the air cylinder is very skinny. It's a rod that's threaded at the tip. It will obviously need to have a ram that has the outer diameter of the chamber's inner diameter attached to it. If I make this ram only the length of the overlap, then it's going to allow a dart to pop up while the chamber is loaded. When the ram retracts it's going to hit that next dart on its way back. So clearly the ram needs to be the same diameter for the entire length of the ram's trip through the mag well. This width of ram cannot retract into the cylinder. So that means that I'm going to need to have a rather long ram and seat the air cylinder that distance back from the mag well. That will make the length of the gun in the back rather long. Possibly not that bad really. The other solution is to mount it above the mag well, and have it extend to push the ram backwards. In this design the ram is shaped like a J. I'm not sure which I want to do just yet. I gather it's really not important just as long as I can retract it and extend it reliably.




#349899 Air cylinder for pushing darts through clips.

Posted by dskippy on 08 December 2015 - 12:42 AM in Homemades

Yes. You'd probably need to sand/smooth the printed part anyway unless you've got a high end printer. And PVC really is easy to chamfer - I usually use a regular pair of scissors. Beside that, you can seal with the manufactured PVC part easily, sealing with the printed ABS could be hit and miss, unless you design in an O-ring seal somewhere which just adds parts.

 

It's really easy to chamfer PVC, yes. I do this with my RSCBs and hoppers. However what I'm interested in avoiding with printing the chamfered part and making it stick into the tee joint is having to bore out the inside of the tee joint. How would you do that? I would use a boring bar on a lathe but it might be easier, if I'm making a few of these, to print that part. Well of course it's easier I guess. You're saying it might jam more. Quite possible. Those little rubber heads on darts are sticky.

 

Agree - for simplicity, 2 pieces of PVC would be easier and faster.

 

I'm unclear on what you guys mean by 2 pieces of PVC here. Could you clarify?

 

The design I have laid out has a seal between a cylindrical ram and a tubular chamber, and would probably have at least 0.25 up to0.5inches of overlap, like your average slide breech.

In any case I would think that the air cylinder would hold fast against the pressure emitted from the firing valve. You may be totally right that bounce is an issue, but personally I'd be more worried about premature retraction in Dskippy's blaster. In a springer you're right, bounce would be an issue and some sort of lockup would be needed.

Actually, for both Dskippy's semi-auto air blaster or for a springer: perhaps a simple catch could be designed. When the trigger is depressed, it notches into the ram to keep it closed. When the trigger is released, the ram may retract (by air spring, etc).

 

I agree, I really don't see how bounce could be an issue here. Premature retraction, however, has to be an issue to some degree. Whether or not it's enough to matter might be just a matter of testing. My original proposal is similar to what you're talking about jwasko. Which is to have the ram slide into the chamber a little bit. Hopefully it will reach the point of exiting the back of the chamber after the dart leaves the barrel. There's definitely an amount of overlap, length of barrel, and pressure of air that can make that work out. I might have to find a high speed camera I can borrow. :)

 

As for your simple catch idea, I don't see how this could work. You're suggesting that the ram can't retract until the trigger is released. This run counter to the mechanism I've proposed. Perhaps your design and mine are really not all that similar. I've never been completely explicit about my plan so I'll do that now. I had been considering two of them. One where a ram pushes the dart into the chamber and one where the barrel slides back over the dart. I have abandoned the latter based on this thread. Here's the former in detail.

 

---------

Design elements:

The mag well is a 3D printed part that mates nicely with N-Strike magazines and has a rounded ceiling that keeps the dart at the right height.

There's a hole in the back of the mag well where a ram can be extended to push a dart out the front of the mag well.

The ram has a tip on it that be pushed into the back of the barrel maybe a half inch to an inch and it seals the back of the barrel

The dart slides out the front of the mag well into the barrel.

The back of the barrel in cone shaped to make this as easy as possible.

The back part of the barrel has a hole in the bottom where air flows in from the blast chamber when triggered.

 

Operation:

State 1: The trigger is being held down. The ram is fully retracted. The barrel is empty. The magazine has a round pushed to the top.

 

State 2: The trigger has been let up. The DCV now allows air to flow from the tank to the blast chamber which includes filling the air cylinder. The ram now extends. A dart is pushed into the barrel. The ram seals the back of the barrel.

 

State 3: The trigger is pressed. The DCV seals off flow from the tank. The blast chamber is open to the barrel through the QEV now. Air pushes the dart out of the barrel. The ram also is retracting at this time. All of the air leaves the blast chamber causing the dart to leave the barrel. All of the air leaves the cylinder as well, causing the ram to retract all the way. Another dart pops up to the top of the magazine. The trigger is still depressed and we're now back to State 1.

--------------

 

So I think, unless I'm missing something, that this is totally incompatible with your idea to restrict the ram from leaving the barrel until the trigger is let up. What happens in the various stages of your design?




#349875 Air cylinder for pushing darts through clips.

Posted by dskippy on 07 December 2015 - 04:14 PM in Homemades

Yes, this. I am thinking of not only a chamfer, but basically a one-dart-long RSCB clip (that is, an oversized tube that does not create an air-tight seal on the dart) that is reloaded after every shot. At the front of this RSCB/chamber would be your chamfer that seals around the very tip of the dart (again, like an RSCB). Depending on the location of the air outlet into the chamber, the oversized chamber would only facilitate airflow to the back of the dart, allowing the dart to be pushed out of the barrel.

I made a ~3-dart-long RSCB like this a while ago by modifying Zorn's n-strike breech. I think I used 19/32 brass as the chamber/RSCB clip, which also functions to support and guide the dart as you mention in A). A 9/16" brass ram was then created. The ram was manually operated, and never jammed on me in spite of the fact that the N-strike mag was held in solely by snapping the feed lips over the 19/32" brass half-pipe. If I knew where it was at the moment, I would simply post pictures and/or a video.

 

I'd really love to see a picture or even a video. I'm wondering how the loading of the clip-fed RSCB worked. After you manually bulled the ram back and pushed it forward did you then need to aim the gun down to reload it? I would imagine the ram would do the job in a one-dart RSCB that had a clip feed but what about in your three-dart version? I assume you pulled back the ram three times in a row, then fired, then aimed down, fired, aimed down, repeat. Am I getting that right? Any chance there's already a thread or picture of it up on the net now? I'd happily search your posts on the forums if I thought it'd be worth it.

 

 

Putting the 1/2" straight through it as Ice said would improve the system. Set your 3d printed part up as a female connection for the PVC T so you can just plug it in. 

 

I'm now a fan of the McMaster PETG, I think it's this number 2044T43. FYI - shipping is like $20 for that long stick, so buy a bunch or buy shorter lengths if you use it)

PVC is super easy to chamfer, and will feed better than the 3d printed part. Just stick it through and chamfer it; only really worrying about chamfering the 3d printed magwell if it is between the dart and the PVC for some reason.

Look at Boltsniper's SCAR-N:

 

Yep, I think I'll be doing this. The only thing is that I'm considering printing the beginning of the 1/2" PVC that goes straight through the PVC tee as part of the magwell. The reason for this is that I'll be able to avoid having to bore out the inside of the tee joint since I can print this extension to exactly fit the two stages of width inside the tee joint. I will obviously also print a hole that allows the air to come up from the bottom threaded piece of the tee.

 

As for the barrel, I am considering 1/2" Sched-80 PVC. When it comes to compressed air guns, I find that a tight seal on the barrel like 1/2" CPVC will give you doesn't improve my ranges. I'll have a slightly tighter fit in the cone come right out of the magwell to ensure that nothing that gets pushed through can easily just fall out of the barrel if aimed downward. That's generally not even a problem with my Sched-80 actually. It has an 0.52 ID and when I seal one end a dart will not fall out even when shaken a little bit. Letting the seal (usually my thumb) up allows the dart to fall right out quickly though. I think that's probably a great seal for compressed air since air compression doesn't need to build up like in a spring gun.

 

You say that it will feed better than a printed part. Why do you think this? Smoothness of PVC vs printed ABS?

 

Boltsniper's SCAR-N looks awesome. I may, very well, try to copy this design on version two of this gun but for now I'm going to try to keep the complications down and go for ensuring it loads properly without jamming.




#349857 Air cylinder for pushing darts through clips.

Posted by dskippy on 06 December 2015 - 12:51 PM in Homemades

Emphasis mine. I'd be a bit leery of 3d printing the breach. By all means, 3d print all the complex parts of it (the magwell, any moving parts), but the operable, sealing, breech parts that hold the darts should be purchased from standard stock.
 
I may be misreading you and that's exactly in line with what you're doing.

 

Yes exactly. I'm not sure I'd say you're misreading me so much as I'd suspect I'm using the word breach inappropriately but yes that's my plan.

 

I will be 3D printing the magwell I guess it's called. It will hold the magazine in place as well as provide a connection on the back side for the air cylinder to firmly and reliably be placed exactly where it needs to be and also hold the barrel in place on the front. The 3D printed piece will also be responsible for having a cone in front for the dart to be guided into. So basically the 3D printed magwell will be for any fine tuned shaping that needs to be right in order for the darts not to jam, but will not be doing any air tight sealing.

 

Based on this thread I think I've decided to do push the dart in from the back of the magwell into the barrel rather than move the barrel back over the dart. I will be loading the dart into a barrel that has a QEV mounted at 90 degrees feeding air in from the bottom. I could potentially achieve this with a simple 1/2" PVC tee-joint. It would be press fit on the barrel and inlet side with a threaded female connection to the QEV on the bottom. The 1/2" PVC tee-joint might be quite a bit too large and have too much empty space for the dart to move around in though. If that's the case I might machine something out of a Derlin rod.

 

Also, just a quick note to anyone discussing hoppers. That is definitely not what this thread is about. I'm not going to use a hopper for this project even if it's better. This is about making a magazine fed pneumatic with an air cylinder. We can discuss the differences between them in another thread if you'd like.




#349824 Air cylinder for pushing darts through clips.

Posted by dskippy on 04 December 2015 - 11:02 AM in Homemades

rego,

 

Thanks. I have extensively read Captain Slug's stuff and it's all great. Especially the ARB5K. I'm basically trying to make that gun for myself with two difference.

 

Primarily, I want to 3D print the clip retainer and breach. I think I can get much more reliable loading out of a 3D printed part that fits the stock elite clips perfectly and pushes the bolt sled or brass tube into exactly the right place. Rather than sawing brass tube and hanging it at the right height above it the clip and trying to hot glue some bs onto it to push the dart down the right way. It's finicky enough that I think if I put enough design into it now, I can 3D print something that a lot people can use in future designs.

 

Secondly I'm just going to use off-the-shelf DCV and QEV combo rather than machining my own valve. His is badass and I might copy that design one day but not on this build.

 

Rego you seem to be advocating for pushing the dart in from the back of the clip into the barrel and feeding air in 90 degrees (likely from the bottom) which is one design I'm debating. The other is the one that shmmee pushed for in his post just above yours, which slides the barrel over the dart and seals to the back of the clip chamber where the air comes in. Do you have any reasons for choosing one or the other? Any information is helpful. I really don't know what I'm going to do on that front.

 

As for using a double acting cylinder and an air spring, I do intend to try what you suggested. I was going to pump air in the back and leave an intake valve on it. I actually hadn't considered that just plain old sealing it (while the piston is fully extended) might actually be enough. That's pretty cool and I'll try that as soon as it comes in a couple of days.

 

For the record I ordered McMaster-Carr part #6498K849




#349814 Air cylinder for pushing darts through clips.

Posted by dskippy on 03 December 2015 - 05:35 PM in Homemades

Since you're planning on utilizing a 3d printer, it should also be possible to engineer a longer sealed section between the tank and the mag well so the piston can begin it's return travel and still remain sealed. It would be adding dead space as the piston retracted, but at least the air in the piston would be feeding back into the tank and out to the barrel at it's fullest velocity.  I'd guess it wouldn't take more than a quarter inch or two of seal to give the dart enough time to exit the barrel, but that's yet to be proven.

 

I'd suggest looking for a piston with 4" to 4 1/2" of travel. That should give you your 3" for the dart and another inch or so to play with in seal and return clearances.

 

It's also worth noting that even an efficient semi auto system with a small tank will use a ton of air. 

 

So, what are you planning on doing for air? Bladder, small hand filled hard tank/regulator , large compressor filled hard tank/regulator, single shot pump to prime?

 

This is why I plan to do based off this discussion and also what I've seen from Doom and Captain Slug's work. As for the tank, it'll be a modular quick connect that I'll connect to a few different things, I imagine. Primarily will be a large, high-pressure tank with a regulator. I might get a paintball tank + regulator and have it filled so that I can actually have a decent amount of air life time. However I also plan to make a backpack sized 100psi tank that I can clamp a bike pump to and pump up myself. The tanks will be connected via hose to a quick connect on the back of the gun, which of course has its own, must smaller, blast chamber on it and will operate and about 30-40psi with a controlled volume. Pretty standard for this kind of blaster, really.

 

Also, after doing a lot of reading on the forums. This one a SpudFiles I've actually ordered an air cylinder.

 

I didn't order a single-acting, spring return cylinder like you suggested. Doom came to the conclusion that he wanted to switch from his existing single-acting to a double acting because the single acting was really long and bulky. The double acting requires that you create your own return mechanism, so I was pretty torn on which to go with. But I ultimately went with the double. I am considering using an air spring for the return. It's hard to buy air springs that are small enough though. Most of them are meant for car suspension. If anyone knows a good solution let me know. I am considering just filling one side of the piston with some low pressure and seeing if that works for me. Otherwise, I might end up using an external spring attached to the mechanism that the piston is moving to return it.

 

Another decision I need to make now is whether to push the dart into the back of the barrel or if I want to pull the barrel back over the dart. Pull seems to have less dead space and makes machining the blast hole must simpler. Pushing seems to be less prone to jamming.




#349813 Air cylinder for pushing darts through clips.

Posted by dskippy on 03 December 2015 - 04:49 PM in Homemades

I see that you'd prefer to use stock darts and clips, but have you considered doing a (much easier) QEV Airgun by Ice Nine (who is posting RIGHT HERE, so you can easily ask him questions directly) instead? You can use an RSCB or as Ice says, a low-angle custom Y for stock darts, and you won't need all the complex (and jam prone) clip parts. You can even use an RSCB as a clip by swapping out the 1/2" PVC tube-mag.

 

A semi-auto breech-loaded compressed air NERF gun is still a kind of bleeding-edge blaster. NERF doesn't make one, only a few scattered homemade prototypes exist built by our top designers, and even very well built they'll still be prone to jamming. If you build one it'll be awesome,but it's a lot more work than is necessary to be very competitive.

 

No sorry, I'm not interested. I have already built stuff like that. The fact that the air cylinder design is bleeding edge is exactly why I'm interested. And I'm not trying to be competitive in nerf wars. I'm trying to impress my nephew with cool stuff. I'm also trying to challenge myself to make something new and different and potentially contribute to the body of knowledge of the community. So, yeah, hoppers and RSCBs are out. I have a bunch of them.




#349793 Air cylinder for pushing darts through clips.

Posted by dskippy on 02 December 2015 - 07:21 PM in Homemades

This is great, thanks for finding the video. You did something similar to what Doom seems to be convinced he wanted to do. Which was to use an external extension spring (in your case, rubber band) to return the piston. This reduces the length that the cylinder need to be in order to have a 4" stroke. It's a rather interesting idea, I must say. It does require a decent amount of extra work in some designs to accomplish this though. It really depends on whether you can handle the cylinder being 10" long instead of 6" long.

 

Your design's problem was not sealing properly. Do you know if it ever seals or if the seal pulls apart too quickly? What problem I have with the design is that intuition tells me that if firing the gun pulls the seal back out of the back of the barrel, you are likely to never have a sealed barrel while firing. This is solved if the seal slides into the barrel so far that it doesn't escape until the dart is out of the barrel. So I'm wondering, how much overlap do you need? It of course depends on how fast your cylinder empties. One could place a flow restricter on the connection between the blast chamber and the cylinder to ensure that this goes pretty slowly.

 

Does your model pull out too quickly and thus destroy the seal it created or did it never really move far enough forward to seal?

 

Thanks again for posting your video. Where did you get that piston?




#349780 Air cylinder for pushing darts through clips.

Posted by dskippy on 01 December 2015 - 11:53 PM in Homemades

Check out Slug's ARR as well. It's in the homemades directory. 

 

Yeah I did already. He machines his own. I'm hoping to just buy this part.




#349769 Air cylinder for pushing darts through clips.

Posted by dskippy on 01 December 2015 - 03:54 PM in Homemades

Yes, I'll probably email Doom directly at some point. I wanted to start up a thread for the community first to see what everyone else has had success with and record it for posterity. If Doom doesn't chime in though, perhaps I'll email and just ask which specific cylinders he's had the most luck with.

 

As for my project, I am pretty set on using stock darts and stock clips. For starters, I like using stock darts because they are interchangeable with the ammo of my arch nemesis (nephew) and I can thus return fire sent my way. Also I'm not really into making darts. The standard clips are just boxes with springs that work perfectly well too so I don't think I can do any better than nerf has ever done on that front. So yeah, for this project, I'm using all stock darts and clips. 

 

I measure the stock dart and clip and found that in required something just shy of 4" to make the trip through the clip. 4" might be more than I need, but not by much.

 

I've read Slugs page too, in researching this project. Definitely a good read. Oddly enough he also does not mention which off-the-shelf air cylinder he used.




#349767 Air cylinder for pushing darts through clips.

Posted by dskippy on 01 December 2015 - 02:44 PM in Homemades

Hello everyone, and in particular Doom (btrettel)

 

I'm interested in making a pneumatic semi-auto similar to Doom's FANG. I've created a 3D printed part that mates with the standard Nerf-band clip that I'm pretty happen with. I just need to figure out which air cylinder I'll be using to feed the darts through.

 

I'm hoping to get exact specs or part numbers on the air cylinder that was used on FANG upgrades. I've done some reading on the original FANG post here.

 

http://nerfhaven.com...un-prototype-1/

 

It was found in the parts bin so he didn't have a part number. He also said this: 

 

After some discussion at Spudfiles, I've already decided on one major change from prototype 1 to 2. I used a spring-return air cylinder here. The air cylinder seems to be designed to move the rod at once rather than gradually, so the spring is prestressed. To keep the force increase small, the spring doesn't travel much and has a low spring constant. And to keep the force sufficiently high to return, the spring must be rather long. All that combines to make a long air cylinder. My cylinder was about 8 or 9 inches long when it only had a 4 inch stroke.

The solution is to use a dual action air cylinder and make one side contain compressed air, with a small air chamber attached to the opening. This will still allow the spring to return all at once, but the energy can be stored in a dimension other than length.

 

So simply put, what have people had the most success with? The task is pretty simple but buying several air cylinders and using trial and error could be pretty expensive.

 

Based on my measurements and Doom's being 4" I'm tentatively looking at the smallest and cheapest McMaster-Carr air cylinder with a 4" stroke. 6498K114 with a or 6498K516 which is 3/4" longer.

 

Does anyone have any opinions on these? Does anyone have any experience with others that they recommend or would suggest avoiding? Does anyone use regulators to restrict airflow to slow down the movement of the cylinder? I've considered doing that but I haven't had my hands on one yet so I don't know if the speed will be too fast anyway.

 

Thanks for the help. One I get enough into on this thread to make a decision I'll put together a test and get my 3D printed part and McMaster-Carr parts list up here on Nerf Haven. 




#335350 Best homemade for stock darts?

Posted by dskippy on 12 November 2013 - 01:36 PM in Homemades

Hey everyone,

I just recently finished a pretty standard Rainbow with a 1-1/4" PVC plunger tube, [k26] spring, 6" of draw, and 11" CPVC barrel. I'm getting about 110 feet on elite darts with it but they are rather inaccurate and fishtail a lot. I've been told that this is a limitation of the stock darts that I'm up against. For the time being I'm not interested in making my own darts and I'd like to stick to the stock darts. I'm wondering if anyone knows of a configuration that will give me good performance but not over power the darts.

I'm considering a Rainbow Pistol with 1-1/4" plunger tube and half of a [k26] spring but I'm not really sure since I haven't tried it.

I'm also interested in what configuration folks are using for darts with larger heads, like the suction cup darts or the velcro taggers. I'm interested in making a front loader for these, probably a pistol-sized gun, and I'm wondering what kind of air volumes and barrel tightness people are using for these as well.

Thanks,
-mike



#335310 How to make plungers with perfect seals.

Posted by dskippy on 09 November 2013 - 09:33 PM in Homemades

Maybe we should talk about the benefits of Stretch-to-fit shaft seals (aka skirt seals), ucups, and neoprene washers. What are the relative pros and cons of each?

-mike



#335290 Help with a barrel for elite darts in my rainbow

Posted by dskippy on 07 November 2013 - 10:08 PM in Darts and Barrels

If your not using a too tight barrel, it might have become tighter when you hammered it into PVC. To avoid this, use a 5/8" spade bit in the 1/2" pvc, then slide and glue them together.

...

Hope this helps.

~SG


It did. That was my problem. I got myself a spade bit instead of a normal drill bit and it bad the slip in much easier. As a result my CPVC is not being squished too much and the fit is much better. Thanks. I'm getting 100 feet regularly now but the direction is very unpredictable indeed. Guess the elite darts are just crap.

-mike



#335159 How to make plungers with perfect seals.

Posted by dskippy on 03 November 2013 - 01:44 PM in Homemades

If your design and printer settings are sensible, 3d-printed plunger heads won't be a problem strength-wise. At this scale, there's no reason not to print them solid, and if you're extrusion multiplier is high enough the strength difference between this and solid ABS won't be too large. I have thousands of dry fires using a 3d printed ABS plunger head without signs of wear, although the responsible thing would be to glue a bit of rubber on top anyways.


Yeah I know, itś plenty strong. I just conceded the point because I it's likely strong enough and I didn't want to delrail this thread, which is much more about the shape. I plan to 3D print these just because it's so easy and cheap for me as I have access to a couple printers. I might switch to machining them from aluminum as well, if they ever break or I just want to try it. But that's not really what this is about.

Getting a perfect seal with them is another story, and it may or may not be possible. I don't know exactly how yours is printed, but you want to use the flat bottom from your printing surface to seal against the bottom of the skirt, and then squeeze it against that (yes, this plunger head needs multiple parts). Even then, the printing process may have left tiny, invisible channels through which air can pass. Increasing the 7/8"-ish holding diameter may or may not have an impact on your seal, I'm really not sure. If you're willing to sacrifice/dedicate the skirt to this project, you might also try supergluing the base of the skirt to the aforementioned flat surface.


Squeezing seems like the big peice of advice from this thread that keeps coming up and I had never really considered. Roboman's don't squeeze, so it's worth trying that out but I think I'm also going to try a squeezing technique as well. Basically I will take the design that I've posted to thingiverse and make the shaft that goes inside the seal slightly shorter. Then I'm going to cap it off with a rubber fender washer as well as a metal fender washer. I think this should be pretty good.

-mike



#335125 Help with a barrel for elite darts in my rainbow

Posted by dskippy on 01 November 2013 - 06:20 PM in Darts and Barrels

Hey everyone,

I am having some trouble making a decent barrel for my new rainbow with a full [k26] inside a 1-1/4" pvc plunger tube using a skirt seal.

I have read a lot of the posts and tried to follow the conventional wisdom of cpvc and brass but it's not working.

I made one barrel, very standard, of 11" of 1/2" cpvc and hammered it into pvc that I drilled out. I cannot push my darts into the back in at all a reasonable amount of time. I reamed out the back to try to help loading but still it's very very tight. Firing actually works okay once it's I'm there but it fish tails.

I then tried 17/32" brass inside 9/16" brass inside pvc. this is okay. Not as tight and I can load it. this barrel however fish tails like mad. I mean our banks off at right angles and his the ceiling. sometimes I get a really long strait shot. mostly fish tailing.

my brand new, first rainbow is far from perfect too. the Aral it's weak and needs to be corrected but even a is seems like way to much power for my barrels.

I tried putting 4 inches of pvc with no brass at the end of my barrel made of brass to give it more length, telescoping, just to straighten it out but no luck.

I know a lot of the write ups here are for home made darts and they fly much better. I really need to use elites though since I play in a setting with shared darts and they are our standard. is anything going to work?

Are homemades just too much power for stock darts?

- Mike



#335088 How to make plungers with perfect seals.

Posted by dskippy on 30 October 2013 - 01:06 PM in Homemades

Really just a simple sandwhich will do, it must be tightened down to the correct force. Not that it matters much. If you scroll down in my writeup I show how I make a good looking (opinion) plunger head with just 2 circles of polycarb. Here's a nice clear pic of how I did it. The screw size in the middle doesn't matter as long as it is 1" or longer. It seals absolutely perfectly and is (opinion) low friction.


Oh it looks like you don't even have anything on the inside diameter of this skirt seal, is that correct? Do you ever have problems with it either sliding side to side or getting it lined up so that it's exactly concentric with the polycarb disks?


They are indeed. You can't really make one without a lathe, which I'm assuming you don't have. If you do have one, they're not terribly difficult to make, and take about 30 minutes once you get good at it.
Here's a drawing that isn't to any particular standard but should be good enough for anyone's purposes here.


Oh thank Roboman. This is quite helpful, I do have access to a lathe. I made a 3D model of your part for reference: http://www.thingiver...om/thing:174234

I have a couple of questions to clarify about this.

1) It looks like this is one whole piece. It doesn't come apart does it? If so I guess you can't adjust how much the seal is being clamped down. 0.325 height compared to 0.375 height on the seal is squishing it a little bit. Did you play with that height to improve the seal or does it not matter?
2) I assume you just stretch the seal over the head and to put it on, right?
3) Why is there so much distance behind the seal's backstop? You have half of an inch behind it. Is this to keep it stable and concentric with the plunger rod?
4) What is the diameter of the cone's widest part? I couldn't figure that out. Is it documented in there? I just guess 0.9*1.25

-mike



#335067 How to make plungers with perfect seals.

Posted by dskippy on 29 October 2013 - 04:14 PM in Homemades

Printed ABS is not that strong.
I have a significant amount of experience with different filaments, and it is definitely not in any way impact resistant.

I'll second the thought that it could break.


Alright, perhaps 3D printing this isn't the way to go. So I'll try another material for the next one and see how the current one holds up. But assuming the materials hold up, is there a better shape to use to make the seal? It seems like the current best suggestion is to put a circle of polycarb inside the skirt seal and sandwich it between fender washers. I'm looking for suggestions on the diameter and thickness of that sheet of poly carb. What makes the best seal? Or does it not even matter because the sandwiching action of the washers is going to do that work for me?

-mike



#335061 How to make plungers with perfect seals.

Posted by dskippy on 29 October 2013 - 02:31 PM in Homemades

Depending on how you printed it, that plunger head may just break. You may just want to replace the whole part with polycarb and do a regular washer sandwich that stretches the skirt as it gets tighter.

Also, perfect seals aren't really necessary. So long as your darts and barrel are a good match, you'll still get around the same performance. In some blasters it turns out that a perfect seal is actually harmful. In most cases it's about e-peen, rather than actual necessity.


Well I guess perfect might not be necessary but it's still worth having the discussion of how to understand how to get a seal to function properly and what things to consider. What exactly is this washer sandwich that you're talking about? When you sandwich the seal between two fender washers are you putting anything inside the seal to match the ID? If not, how do you ensure it's centered? Just eyeballing it and clamp tight enough to ensure it stays? I tried this method first, before I got my part printed. I didn't like how wobbly it felt and the 3D part feels really secure. Also I can't imagine this breaking at all. It's very solid. It's probably similar to the shape of Nom's lathed aluminum plunger heads but I haven't seen a write up where he explains exactly how he does those.

So to sum up you suggest A fender washer, a circular piece of polycarb (1/4" thick?) with a #6 bolt hole in the middle, and another fender washer. Then put this whole thing on top of the square rod. What diameter would you suggest for that circle of polycarb?

My design is fairly similar but the rear fender washer and circular piece of polycarb are one piece and they are printed together out of ABS. I could achieve the sandwich pressing effect that you're talking about simply by making the shaft part of my piece slightly too short. I that's a great idea, I'll try that.

-mike



#335055 How to make plungers with perfect seals.

Posted by dskippy on 29 October 2013 - 11:33 AM in Homemades

Hey everyone,

I just made my first homemade spring-loaded gun (my second homemade). It's a Rainbow. First I'd just like to say thanks to this community for inspiring and helping me with all the great tutorials.

Now on to the issue. The seal is not perfect. When I hold my hand over the front of the gun and fire, air clearly is leaking back out of the holes in the back of the gun, so it's slipping past the plunger when compressed. It's not terrible, it does compress air and it doesn't dry fire when my hand is over it, but I want to make the seal perfect so that the plunger stops dead like I have seen in so many of your videos.

I'm open to any suggestions or descriptions of any other things people have done that has worked. I am hoping that this thread can become a discussion of all the ways to make a really good seal and debug an imperfect one. Mostly, though, I'm hoping to figure out how to fix my own.

My current setup is using a 3D printed plunger head along with a skirt seal (aka shaft seal) from McMaster-Carr and a fender washer to hold the seal on the front. Then I used plenty of silicon grease to lube it up. I put the plunger head up on Thingiverse incase anyone wants to duplicate my design. I'll be updating it based on feedback from this thread.

Plunger head: http://www.thingiver...om/thing:173486
Shaft Seal: http://www.mcmaster....9562k46/=p5bvgg
Fender washer and silicon grease from the hardware store.

I suspect that in order to improve my seal, I would need to increase the diameter of the cylinder that the seal wraps around. This would cause the seal to stretch to fit and press against the inside to the PVC a little harder.

For those of you using the same McMaster-Carr stretch-to-fit shaft seal, what is the exact diameter of the piece your seal's inner diameter is fit around? Mine is 0.894 inches, at the moment. McMaster-Carr suggests that this is for a shaft with diameter 0.95"-1.07". In the Rainbow-Pump writeup that I followed for this design, he used polyester tube that is 7/8" in diameter. This is 0.875. Unless polyester 7/8" tube is actually bigger than 7/8". I am not sure if his seal is much better than mine though but I suspect it is.

Anyone have any tips? Should I just keep incrementing by 100th's of an and print this plunger head again? Can anyone give me the outer diameter of your plunger heads for use with a skirt seal? Is is possible that using a polycarbonate plunger tube is better because the insides are precisely measured and I wouldn't have to worry about deviations in the plunger tube?

Thanks for all the help,
-mike



#335022 Homemade flywheel gun

Posted by dskippy on 28 October 2013 - 04:52 PM in Homemades

Hobbyking Donkey 730kv 35A 11.1-14.8v brushless motors. They are a good choice, the only problem seems to be that they use bushings, so I'll probably have to replace them with ball races. For comparison, the Hailfire's motors are (i think) 130 size motors, which run at 6 volts and draw 800ma at stall. So basically the Donkeys are close to 3x the voltage and over 40x the current.


I have some questions about your setup. First of all did you find any other motors that are better for this than the Hobbyking Donkey? Secondly do you have a list of the other parts that are in this build? You have two motor controllers I think and some kind of inductor coils going into the Arduino it looks like. Do you have a parts list? Finally what diameter are your flywheels and what hardware are you using to connect them to the motor shaft?

Thanks a bunch,

-mike

Please check the last post date in a thread before posting, and just PM the OP with questions if it's more than a month or so since the thread has seen activity.



#334780 Barrel advice for a compressed air gun

Posted by dskippy on 14 October 2013 - 10:55 AM in Darts and Barrels

Curses. Full circle to what I started with accidentally. They did fly pretty damn far at an angled firing position at 120 psi. I'll go back to them and start playing with barrel length to experiment. Thanks everyone.

-mike



#334736 Barrel advice for a compressed air gun

Posted by dskippy on 13 October 2013 - 12:01 AM in Darts and Barrels

As basically everyone else in this thread has said so far, stock elites aren't really that great for what you're trying to do. At 120 psi, it's impressive that you actually managed to get them to fire!
It sounds like you wanna keep the stock-dart firing capability; what you could try instead of using elites and brass, is just a piece of standard 1/2" with taggers and whistlers. Basically a blow-gun, I used to use one, they're quite accurate. If you decided to give it a shot, I'd use about 3-5', or whatever feels like the right size.


That fits with what I've found. Basically what I want to know is this:

What stock Nerf dart can travel the furthest? What setup achieves this goal?

Also regarding the firing angle comment from another post, I am firing at 45 degrees when I am getting near 200'. I didn't realize there was a standard for reporting firing distance horizontally but naturally that makes sense. Anyway. I just want to know how far I can get a stock dart to go. 1/2" schedule 40 with taggers has been my best so far but that was just convenience. I figured I must be able to do better but perhaps I just got lucky.



#334701 Barrel advice for a compressed air gun

Posted by dskippy on 11 October 2013 - 07:39 PM in Darts and Barrels

You'll probably be disappointed. Stock darts tend not to have the combination of mass and low wind resistance needed to achieve that kind of range. And if they do? Almost never where you were pointing. Honestly, at pressure like that, I would not be surprised of every dart you put in that thing shreds on the way out. Especially stock darts. If the pressure remaining in the barrel when the dart exits exceeds the maximum pressure that the foam tube can handle, it will explode. For the new MEGA darts, this pressure is about 20PSI.


Well perhaps I shouldn't have quoted a random number. Maybe 200' is not possible. But what is possible? That's what I want to find out. Also accuracy is not what I'm going for here. Just distance. Other projects I'll go for reasonable. This gun is impractical for reasons beyond the scope of this article.

But other folks on this forum have achieved distances nearing 200' by their reports. Also I've gotten a not of luck getting velcro headed darts to go upward of 175' with just a 2' schedule 40 barrel. This speaks to BuffDaddy's point that looser fits are better for compressed air guns. Having had better luck with that and getting BuffDaddy's feed back I will try much looser fits.

-mike



#334689 Barrel advice for a compressed air gun

Posted by dskippy on 11 October 2013 - 05:33 PM in Darts and Barrels

What, pray tell, are you planning to shoot with this? Because if it breathes prior, it is unlikely to continue after.


I'm firing them off into the park at work. I'm going for distance. So... I'm shooting a very unlucky piece of grass. Hopefully about 200' away.

-mike

p.s. You're not really going to kill anything with a any stock Nerf dart, even if you max out at 120 psi. Sure it can hurt a lot but it's similar to a paint ball gun.



#334686 Barrel advice for a compressed air gun

Posted by dskippy on 11 October 2013 - 04:49 PM in Darts and Barrels

Hey, thanks for much for the reply. The reason I'm using the elites is that I wanted a long barrel to give me a long acceleration period and they are standard darts that are all around my office. I guess if these guys can't fly well that well, I might try the velcro or the suction cup ones. Would either of these be any better? I'll try a lose barrel but 9/16 is honestly pretty lose. I can use it very effectively as a blow gun. The barrel alone that is. Perhaps I should get some schedule 80 or just 40 and try that. It seems like the darts with large heads like the velcro or the suction would have a hard time being back-loaded into a very long barrel.

So if I'm open to changing up my darts and my barrel, what setup would you suggest for launching a dart as far as possible? I know I could launched them ungodly far if they are, for example, made of wood, or have metal inserts. I've done this. But I'm interested in maxing out the range of off-the-shelf darts here.

Thanks for the feed back,
-mike



#334684 Barrel advice for a compressed air gun

Posted by dskippy on 11 October 2013 - 03:00 PM in Darts and Barrels

I have been reading the barrels and darts form for a while and I have been having a hard time figuring out what I should do to make an optimal barrel for my compressed air gun. The gun is a typical 3/4" sprinkler valve gun. I have made two barrels and two chambers for it. The first a 1' long barrel with a small chamber 4x the volume and the second is a 3' long barrel again with a chamber 4x the size. I am compressing my air to about 30 psi, 60psi, and 120psi. Both barrels are 9/16" brass nested inside 1/2" schedule 40 PVC.

With the 1' barrel I get decent shots, 150' at max psi. With the 3' barrel I get varying behavior. Sometimes 200', sometimes the dart stays in the barrel bunched up, sometimes the tip blows off in the barrel and the foam flops out, sometimes the dart dove tails, sometimes I get a weakish shot off target (probably a minor dove tail).

I am wondering if people have an recommendations. I am using standard Nerf Stefans bought off the shelves and I'd like to stick to that ammo.

I have considered making a telescoping barrel based on what I have read. The disadvantage of a telescoping barrel is that pressure cannot build up behind the dart long enough if you make the tight-fit portion too small. However, if your reading comprehension is good you'll remember that I'm using a compressed air gun. :) So perhaps telescoping is a good way to go? Perhaps even just a loose-fit barrel. I could do schedule 80, schedule 40 even, I have not tried CPVC, that seems way too tight. Has anyone experimented with compressed air cannon barrels? Basically, I want to make the dart go as far as possible. This is not for a war so I don't care if it would hurt some one if I hit them. I have other guns for actually shooting humans. This is just for show.

Thanks a bunch,
-mike



#334142 I'm Hoping to Avoid Feeling Overwhelmed

Posted by dskippy on 19 September 2013 - 01:59 PM in Homemades

Hey,

Welcome to the community, and don't feel overwhelmed. You definitely don't need an engineering or physics degree. In fact, I think if you're not an engineer, getting involved in the DIY Nerf Blaster community is a really great way to learn some basic engineering/maker techniques and it's a really helpful community. Here's some basic advice and info that I found helpful:

There are three majorly popular spring-based designs on this form that people seem to be copying:

Snap by Caron:
http://nerfhaven.com...?showtopic=5767
There's a highly regarded tutorial on a derivative by Rork:
http://nerfhaven.com...showtopic=20296
These are probably the easiest to make (though others may disagree) and a great place to start.

+bow by Mad Scientist:
http://nerfhaven.com...showtopic=10521
Derivatives include the L+L (Lock and load) as many call it which is a pistol sized version. He has a great instructional thread. These are beautiful but also very complicated to make and require a lot more material than the Rainbow.

Rainbow by Stark, Beaver, and Paul:
http://nerfhaven.com...showtopic=20330
Designed as a simpler, more compacted version of the +bow catch. This thread is amazing and my personal favorite of the three designs.

Go ahead and just get started. You'd be surprised how easy it is to just get something working. After all it's just air rushing through a tube with a dart in it. From there, you'll learn a lot and be able to refine your design and improve your building skills.

-mike



#327136 Interesting 1" CPVC coupler find.

Posted by dskippy on 21 February 2013 - 10:12 AM in Homemades

Does anyone use these?

http://www.pexsupply...-Socket-Bushing

I order one for a 1-1/4" plunger tube gun I'm in the process of making and I'm wondering if this connecter makeitgo has created has any advantages I should know about.

-mike