20 replies to this topic

[Azrael0987]

Been a while since ive put any brain power towards Nerf and got itchy with an idea a few days ago. I worked through a few of the shortcomings of my previous design until I had a solid enough thing in my head to spill onto paper and this is where im at so far. Its evolved into a full function blaster with loading and an improved trigger and tank seal mechanism. The seal is placed outside the tank with a spring to control the max pressure as an OPRV, maximum pressure would depend on how strong said spring is. Spring loaded check valves for the rear tank seal and inside the pump head to maximise pump efficiency.

Expected operation as follows:
(1) Pump 2-3 times until seal cracks
(2) Pull front trigger and actuate breech
(3) Pull rear trigger to fire

Overall I think it is an improvement in function and aesthetics, as well as safety with a proper way to regulate pressures now. The new seal allows use of an ordinary trigger that should provide consistent valve openings (unlike 1.0's ball valve).

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Edited by Azrael0987, 11 March 2018 - 04:15 AM.

[Elithenerficorn]

Good work man, I’ve been waiting for a rival air blaster for a while and this is a much better design than I could’ve come up with

[Azrael0987]

Thankyou! Im going to the hardware store soon to get supplies and start prototyping so update pending. I made this art project gone wrong to get a good idea of 1:1 size and how much pump id have. Overall length roughly 24-26in, 6in tank length, 8in pump draw. Redesigned amd simplified the tank seal and trigger mechanism so its all internal in the cross fitting.
Picture 1: Pump in
Picture 2: Pump out
Picture 3: Breech open
Picture 4: Breech closed

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[Elithenerficorn]

You may want to widen the air release hole so that you get enough power to clear the barrel.

Also, rifling will stabilize the hirs at high velocities. The main reason no rival air blasters have been made is because the rounds become unstable past 130 FPS. an air blaster with a tank that big would pass 200 FPS, thus the need for a rifled barrel. I suggest making your breach brass sheathed in whatever material youre using so you can Dremel rifling into the brass while still keeping it airtight, this would also allow you to notch it so the pump+breach operator idea you have will work well



Sorry for my shitty drawing skills

Edited by Elithenerficorn, 13 March 2018 - 10:55 AM.

[Meaker VI]

Also, rifling will stabilize the hirs at high velocities. The main reason no rival air blasters have been made is because the rounds become unstable past 130 FPS.

I do not know that anyone knows that rifling will do anything for HIRs. All/most of the official blasters already use hopup to stabilize them. I am not sure if rifling would do anything hopup does not do already.

[Elithenerficorn]

Spin stabilization works for rivals ammo because they are a consistent density, as a posed to darts, which are forward heavy and Are already stable. Hop-up adds backspin which, because of the Magnus effect, increases range. It doesn’t do anything to make it more accurate. Rifling creates sidespin around the center axis, which gyroscopically stabilizes a projectile. This doesn’t affect darts very much becuase they, being forward-heavy, are already very stable, inaccuracy in darts is caused by either irregular head shape alla elite darts, or muzzle blast. Spin stabilization only greatly affects projectiles that are back-heavy (like bullets), or balanced (like hirs).

I’m pretty sure you can’t have a system with both hopup and rifling because backspin and side spin together would create diagonal spin, which would throw the round off because of the Magnus effect. And before anyone asks “why isn’t spin stabilization affected by the Magnus effect?”, the Magnus effect only applies when the spin is parallel to the plane of travel, the sidespin created by rifling is perpendicular to the plane of travel, so the Magnus effect doesn’t apply

[Meaker VI]

Spin stabilization works for rivals ammo because they are a consistent density, as a posed to darts, which are forward heavy and Are already stable. Hop-up adds backspin which, because of the Magnus effect, increases range. It doesn’t do anything to make it more accurate. Rifling creates sidespin around the center axis, which gyroscopically stabilizes a projectile.

 

I'm aware of this, however I thought the problem with HIRs was that they don't want to go faster than ~130 FPS no matter what you do. Hopup, smooth bore; I haven't seen reports from anybody using rifling but I suspect the result is the same: the things won't go much past 130 FPS. My point was also that we're stabilizing them already somehow (via hopup), so it's possible that no amount of stabilization will make them go faster. They're not especially dense, that's probably the issue.

 

We'll see though; Slug is working on the Rival Caliburn and if anybody can break the FPS limit it'll be him. So far, he reported that using either the [k25] or 26 resulted in 135 FPS, which is odd.

[TantumBull]

I thought the problem with HIRs was that they don't want to go faster than ~130 FPS no matter what you do. Hopup, smooth bore; I haven't seen reports from anybody using rifling but I suspect the result is the same: the things won't go much past 130 FPS. 

Keep in mind that I think we, as a community, have yet to see anyone use a propulsion method other than springer or flywheel on HIR. In Slugs rivalburn post on reddit there was some back and forth about ballistic limits, and I think someone referenced an air blaster shooting rival. I didn't follow through and don't recall if the commenter's reference had chrono data or was more of an anecdote.

 

Assuming we can put enough energy into the ball, as long as it doesn't destroy the ball itself (looking at you people shooting nerf with shotgun primer), there isn't really any limit to the muzzle velocity. That's not to say the drop off will be insane, but we should be able to get higher muzzle velocities if we put enough energy into the rounds.

[Azrael0987]

I was thinking brass for the inner barrel for the availability to nest. I could use a short piece glued into the pvc barrel for the seal to the inner barrel and make it slide smooth. As far as stabilization I wanted to test what scar strings in the pvc barrel past the movement of the inner barrel would do . Also just a hop up tab at the end of the barrel. I remember seeing a paintball barrel that had a curve in it that produced backspin by making the ball go over the hump before exiting the barrel. So far its fairly inspired by a paintball setup but nerf made it so easy so I dont see why not. Ive also thought about using a wye sitting in a cup made from the top of the cross. I dont see why it cant be adapted to shoot half lengths or maybe even rival if the wye was big enough.

[Azrael0987]

Its called the Flatline Barrel System. Ive seen it used at a paintball game and he was outranging everything and its shorter than my 22" barrel. I know rivals have a velocity cap due to low mass but Id assume they'd accept some of the same characteristics. I want to see what I can make with heated pvc to mimick the flatline barrel. It gives a weird flight pattern where it curves down and essentially magnus effects back upward. Its not a pop shot but its consistent enough to shoot around trees so its fairly useful.

Edited by Azrael0987, 13 March 2018 - 05:11 PM.

[shmmee]

Its called the Flatline Barrel System. Ive seen it used at a paintball game and he was outranging everything and its shorter than my 22" barrel. I know rivals have a velocity cap due to low mass but Id assume they'd accept some of the same characteristics. I want to see what I can make with heated pvc to mimick the flatline barrel. It gives a weird flight pattern where it curves down and essentially magnus effects back upward. Its not a pop shot but its consistent enough to shoot around trees so its fairly useful. 140-2__59317.1444332281.500.659.jpg

I've heard of an old pipe fitters trick i've been meaning to try someday. If you pack a tube full of sand you can heat and bend it without collapsing the tube I.D. I've been meaning to try it with cpvc to make a choppered feed tube but it might work with your DIY flatline barrel as well. Though, to be honest, I really don't understand how the droopy barrel is supposed to help with range.

Edited by shmmee, 14 March 2018 - 08:30 AM.

[Elithenerficorn]

It increases range because it forces the ball to roll against the top of the barrel, which creates backspin

[stuck by stefan]

Do yourself a favor and start learning how to design with CAD. Programs like Fusion 360 are free and are immensely capable. It's like an unlimited sandbox where you can build and troubleshoot digitally in hours what would usually take weeks of trial and error in the real world.

Also, I don't know if Fusion 360 has this, but in the program I use (SolidWorks) There's a very detailed simulation system that would allow you to input the material you are using along with your planned pressure, and it will be able to tell you if the system is safe of not. 

Also: I'm not sure if you're using PVC for the air tank, or how high the pressure is, but I would be sure to cover everything that is pressurized with Kevlar reinforced tape so that in the unlikely event that is does explode, you won't get shrapnel in your face.

[Azrael0987]

Do yourself a favor and start learning how to design with CAD. Programs like Fusion 360 are free and are immensely capable. It's like an unlimited sandbox where you can build and troubleshoot digitally in hours what would usually take weeks of trial and error in the real world.

Also, I don't know if Fusion 360 has this, but in the program I use (SolidWorks) There's a very detailed simulation system that would allow you to input the material you are using along with your planned pressure, and it will be able to tell you if the system is safe of not. 

Also: I'm not sure if you're using PVC for the air tank, or how high the pressure is, but I would be sure to cover everything that is pressurized with Kevlar reinforced tape so that in the unlikely event that is does explode, you won't get shrapnel in your face.

Ive used autocad before for a class but didn't get to use it much outside of that. I need a computer though to take any good use it of that. I had planned on wrapping the exposed pvc with gorilla tape until it was smooth with the fittings. Probably using thick walled grey conduit for the pressure chamber as well.

[Azrael0987]

The flatline barrel rolls the ball along the upper edge of the barrel down the curve causing it to roll backwards. Once it exits the barrel it spins and has a magnus effect flight pattern lifting the ball back up and flying further. I just dont know how theyll perform due to lower mass. Either not really take any advantage of the system or magnus too much to the point that theyre flying more sideways than forward.

[Meaker VI]

The flatline barrel rolls the ball along the upper edge of the barrel down the curve causing it to roll backwards. Once it exits the barrel it spins and has a magnus effect flight pattern lifting the ball back up and flying further. I just dont know how theyll perform due to lower mass. Either not really take any advantage of the system or magnus too much to the point that theyre flying more sideways than forward.

This is done already in airsoft and Rival with a hopup system. Paintball does not use it (AFAIK) because it would likely pop the balls.

[Azrael0987]

I didnt know how it didnt pop balls either but it was really freaking cool. I thought hopup was a tab of sorts at the end of the barrel. It interfered with the balls exit and made it spin towards whatever side of the barrel the tab is on. The flatline was a truly bent barrel that managed the same effect. A friend from highschool had one and it was wicked. In my opinion it made a smoother backspin than the abrupt hopup tab and made more of a floating shot that kept going like a laser until it lost spin. Basically it was a 100ft laser not a 100ft arch shaped shot.

Edited by Azrael0987, 14 March 2018 - 09:43 PM.

[Elithenerficorn]

Hmmm,


I dont think it would work quite the same way with rival, because of the lower mass. The lower mass means friction has a greater affect, and the friction from having the barrel bent would significantly decrease the velocities, which is kind of the point of using a breached air blaster, to get higher velocities. A hop-up tab focuses the friction into a single point, instead of spreading it out. The instant friction doesnt affect the rounds as much and thus you retain most of your energy. The hirs are already stable because of the dimpling, which creates stabilizing drag, which is part of the reason they dont like going faster than 130 FPS. Once you overcome that FPS barrier, however, the rounds become unstable because the same drag that made them stable at lower velocities now throws them off at higher velocities. You fix this by adding rifling to the barrel so that you have spin stabilization. Of course I could be completely wrong and you just need to put a fuckload of power into it. Somebody should expirement with a drainblaster singled for hirs to force them past 130 FPS so observation of the flight characteristics can happen. I cant do it because I dont have a drain blaster

Edited by Elithenerficorn, 15 March 2018 - 10:53 AM.

[Azrael0987]

I have a singled titan I can do some testing with but theyre not as good imhp. I was really hoping to have something new here but I think rifling ala scar would still do a lot. Possibly enough to not need the hopup tab. Im hoping the blaster Ive devised will make a good all around of decent performance for rival, as clean and ergonomic as pvc can be, and not have nightmarish pump/load times. Im thinking of using the 1" pump and 1 1/4" pump tube from my original design to decrease the number of pumps it takes to fill the tank. Id assume the roughly 2:1 volume difference would equate to half as many pumps. I really have no idea how many a 1:1 setup would take until I make one but the fewer the better

[Elithenerficorn]

You’re right about the ratios. Since a pum is forcing air into the tank, having a pump with twice the volume of the tank would fill it up twice as fast

[Elithenerficorn]

Found an outofdarts video( )were he had a drainblaster singled for rival and he was getting about 200 FPS out of like an 11 inch loose fit barrel. It’s definitely posible to blow past the 130 FPS with enough power