Water gun structures

[Silence]

Wow, that looks quite professional!

I'd imagine building a water gun nozzle selector would be easy for you now that you have access to a drill press and the like, so you can create a fine groove for the O-ring at the end of the bore. Even a dremel tool might be able to do the job, but not as evenly.

My previous suggestion was to stick an O-ring right in the end of the barrel, then line the seam with epoxy from the inner side of the assembly. It would work a lot better with a groove. And either way, the normal force from the rotation disc should be able to hold the O-ring in place.

In your Nerf turret, I don't see exactly how the disc rotates. Is there a piece in the center that can spin? (A bolt with threads can't really spin...) My solution, in the absence of any other, would be to use telescoping/nested copper tubing.

[Ben]

To rotate the barrels, just grab the disc and turn it. That's all. It's exactly like most rotating barrel assemblies/rotating nozzle assemblies.

Also, if you were wondering about the lack of an O-ring in the barrel rotator, I've noticed that Nerf guns don't have O-rings there. The pressure isn't high enough. The plastic on plastic seal is decent enough for this.

Edit: I'm actually pretty amazed the barrel assembly turned out this well. It wasn't hard to build at all. The procedure was tedious because of the pilot holes, alignment checks, alignment lines drawn, etc., but it worked. I made up the procedure as I went along, and some parts aren't perfect, but they're close enough. I know what to do for my next barrel assembly and nozzle assembly now.

The first thing I would suggest would be using PVC for the rotating holes part, especially with Nerf guns. PVC is easier to machine, epoxies stick better to it, and you can use PVC cement on it to stick things to it. Note that I used a PVC plug with a hole in it cemented to the grey PVC sheet (some of the little PVC I had) to plug into a coupler on the gun.

Other than that, try to duplicate other rotating nozzle selectors if you want to make one of these before I get a guide up. That's all I tried to do, and it worked.

[sbell25]

The barrel assembly is really well done. Good job.

Does the fact that you don't have a spring in the locking mechanism affect it at all? Or is the plastic ever so flexible enough that it just 'rides' over the screw with a click?

[Ben]

The spring is there so that the disc can lift over the screw when turning, while it pushes the disc down for a seal. The screw is there to align the holes, which is helpful because you can't mess up the alignment now. I haven't seen any homemade rotating barrel assembly with a locking mechanism like this.

If you need some more help understanding my mechanism, examine a rotating nozzle assembly. It's exactly the same mechanism. I ripped off my CPS 2700's nozzle assembly very well.

The plastic isn't very flexible. In the 4 inch diameter circle it's in, I couldn't bend it without a lot of effort.

[sbell25]

I don't see a spring. Can you point it out to me please?

I understand how nozzle selectors work. I was under the impression that you didn't have a spring to let your locking knob thing (the one at 6 o'clock position, I should have mentioned that) get pushed down by the disc, and then lock back into place.

[Silence]

I think sbell25 was asking why there was no spring on the catch itself. It looks like a spring on the entire disc is used instead.

My question about rotation actually concerned the piece in the middle. It looked like you just had a large bolt there. But now I see it's a rod with a spring over it, and the rod allows for spinning.

Once again, I like the simply design, and good luck in your wars!

EDIT, addressing the latest post: The spring was slid right over the big bolt in the middle. When you spin the disc, the entire piece can rise just a bit thanks to that spring. Of course, in a water gun, that wouldn't work - the pressure would blow the disc right off.

[sbell25]

My question about rotation actually concerned the piece in the middle. It looked like you just had a large bolt there. But now I see it's a rod with a spring over it, and the rod allows for spinning.

Hahahaha! I thought it was a large threaded bolt too. I stared at that picture for ages trying to figure out what you were talking about. I see how it works now, thanks for clearing that up. So another question: is the side facing the camera the side that attaches to the gun? If so, how will you actually attach it?

[Ben]

Perhaps I should have taken some pictures from other angles. I just took a quick one. It's late right now so I'll take some more tomorrow (or actually, later today in EST).

The side facing the camera will have a bunch of barrels attached to the holes in a few days. The other side has a PVC plug with a hole drilled in it cemented to the grey PVC sheet.

[Silence]

Here's a picture of a common turret Nerf gun (I found the image through Google):

Homemades tend to have much longer barrels.

Ben's picture shows the turret from where you'd see it outside the gun.

[Ben]

I finished the turret for the most part two days ago. Below are some images from different angles of it.











As you can see, I don't have every barrel on there. I used only barrels that I had, which was one piece of brass and a three foot piece of aluminum. The aluminum is better for this turret than the brass because the OD is 5/8 inches, which is the diameter of the holes I drilled. So, the aluminum can be stuck into the holes as is. That was too weird of a coincidence.

It was a good proof of concept. I learned a few things I could apply to nozzle selectors, but more things about Nerf guns. One thing you should notice is that I added a much stronger spring to keep the seal better. When the Max Shot shoots, it recoils because the plunger slams into the end of the tube. That would break the seal in the turret, so I upgraded to a stronger spring, which is a good idea all around.

When I make a water gun nozzle selector, I might use a rubber sheet with holes in it instead of O-rings. It would be easier to set up and seal just as well.

[Silence]

With Nerf guns especially, is it really necessary to have the barrel and the hole line up perfectly? Flow might be reduced a little bit otherwise, but if you don't need perfect alignment, then you may not need a spring and catch at all.

I want to take a look at how commercial Nerf guns spin the turrets automatically. They do use catches to keep the turret aligned, but I want to replicate the little gears that do the spinning.

A rubber sheet may have friction. Or maybe not if you lubricate it well. It does sound like an easier type of seal to implement. Good luck!

[Ben]

The alignment with this isn't perfect because it doesn't have to be. The darts I use have an OD of about 0.525 inches. The aluminum has an ID of 0.527 inches and the brass has an ID of 0.533 inches. The PVC pipe has an ID of 0.625 inches. So yes, even with a little bit of clipping, the area is still more than it needs to be.

With that being said, I would like to keep the spring and catch because that makes alignment dead simple by locking in place. I designed it to work within a wide tolerance because there was little precision in my measurements. I tested it out with just a nut tightened with a bolt, and to get a good seal, you couldn't turn it. So at least the spring is necessary.

Nerf guns use different mechanisms to turn the turret automatically. One Lanard gun I have disassembled uses something linked to the pull of the spring. Air pressure ones have something linked to the trigger. There's no gears from the ones I've looked at. They basically have a piece that turns when something is pulled back on them. I can't think of another way to describe it, so I might have to give it more thought or draw a picture if you'd like to know. Disassemble a Nerf gun with rotating barrels and you'll see, too.

As for the rubber sheet, it probably will have a good deal of friction without lubrication, so I'll have to lubricate it or use a different idea. I'd like to try a rubber sheet because it would be easier to attach than an O-ring with notches, mainly. My plan is to attach it with a small screw and nut.

[Silence]

I guess I was freaking out about alignment and rotation since I had been planning a single that all the turret lengths fed into. That won't work so well no matter what. Oh well, aluminum barrels are cheap.

I figured Nerf turrets use levers, pulleys, and the like, but without gears, I'm wondering how things stay aligned indefinitely. If the spinning mechanism is off by even one degree per rotation, then the entire alignment could be off quickly. I guess that's what the catch is for.

How large a rubber sheet are you using for your rotating nozzle selector? At first I thought the sheet covered the entire surface area of the plate, but that's not really necessary. Doesn't matter though because the friction should be about the same.

[Ben]

I figured Nerf turrets use levers, pulleys, and the like, but without gears, I'm wondering how things stay aligned indefinitely. If the spinning mechanism is off by even one degree per rotation, then the entire alignment could be off quickly. I guess that's what the catch is for.

Well, I have read much about rotating turrets breaking, so the old methods might not be the best. I admittedly don't know much about it.

How large a rubber sheet are you using for your rotating nozzle selector? At first I thought the sheet covered the entire surface area of the plate, but that's not really necessary. Doesn't matter though because the friction should be about the same.

I want to try a rectangular piece covering the catch and the pipe opening. That's all that is necessary. Of course, I'm sure experimentation will be necessary to get it right. O-rings in a notch might be the best way.

[Silence]

Boltsniper's Bullpup Tactical Rifle has a rather simple system to connect the rotation system to the trigger. A guide is attached to the trigger and it slides through the channel on the turret. All you need is a spring holding the guide to one side so that it doesn't reverse and go through the groove is just left.

Notes:
1) Each channel has a "vertical" part before the fork. That gives the trigger some leeway to release all the air before actually spinning the turret.
2) That's assuming the turret spins on the trigger pull, not on the return. If you have the guide go down the diagonal when the spring returns the trigger, then the "vertical" part before the fork isn't necessary. That does require a stronger spring though.
3) I would make the "vertical" part before the fork much longer, just to give the dart(s) and air extra time to exit the barrel before spinning. You may think the angle at the fork would be too steep for the guide to follow; but if you have eight barrels per turret, not four, then the angle is shallower than pictured.
4) The overall design is pretty haphazard. The turret guide is very far from the actual trigger and the air flow is rather convoluted. Still, the rotator design is neat.

You could probably add a second trigger to a water gun simply to rotate the nozzle selector in this fashion. That would require a tall cylinder rather than a thin disk, though. (EDIT: Note the desperate attempt to make this post relevant to SSC.)