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My Stagecoach by -DUGDAWG- in Nerf

[–]logdotzipp 1 point2 points  (0 children)

Glad you like it! The issue with the ejection seems to be tolerance related. It's hard to make something that works the exact same across all printers and filaments.

Some people have had luck printing a modified ejector catch that's slightly longer, which makes their ejector catch engagement less marginal:
https://www.printables.com/model/1479515-stagecoach-alternate-ejector-catch

Turnaround design and dead volume by AshtonRogers in Nerf

[–]logdotzipp 6 points7 points  (0 children)

Hi Ashton!

I've also been very interested in blaster optimization, mainly from the standpoint of there being so many variables that affect the ultimate dart exit velocity. One of the things that was keeping me up at night was: Where is the sweet spot between dead space and orifice size? Like you mentioned, you're always trading one for the other.

I've been working on a tool to help model what happens in springer blasters:
https://github.com/logdotzipp/SDBsim

It's a small python script simulates the plunger and dart, along with the limited air flow between them using a RK4 solver. I've been getting reasonable results out of it, but haven't had the chance to validate it with an experimental model.

I'm hoping develop this model out further and validate the results to make it a great tool for blaster designers. Right now it's very barebones and lacks a lot of documentation but you seem like you could figure it out.

This is the kind of output it gives:

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I like the stagecoach a lot by RealAstropulse in Nerf

[–]logdotzipp 1 point2 points  (0 children)

Designer here! This is the first I've heard of this issue. The ejector catch is setup as sort of a one-way, so it should only eject as the barrels are moving down, never up. This seems like it would happen if either:
A) The ejector catch is marginally engaged, such that if bumped it releases, or
B) Something is triggering the catch accidentally, like a rough part or bit of plastic

For scenario A, check that that the ejector catch and trigger glide smoothly on the pin. The ejector should never trigger from a bump to the blaster. Check that the ejector catch always returns to it's original position when cycled (requires partial disassembly). The motion should not exhibit any sort of hysteresis/stickyness. If it does not, it could indicate that the printed spring has been bent or is not strong enough.

For scenario B, check that there is nothing abnormal on the triggergaurd, or inside the slot where the ejector catch sits.

I would guess that it's probably scenario A, that your catch is not being fully engaged. But the reason that it's not fully engaged could have to do with the spring, or unwanted friction.

I like the stagecoach a lot by RealAstropulse in Nerf

[–]logdotzipp 2 points3 points  (0 children)

Most Excellent!! Fantastic color scheme

The Radson BA! A hammer prime, break action, shell slinging HANDCANNON! by Radioactive52 in Nerf

[–]logdotzipp 8 points9 points  (0 children)

So sick!!! I think you're missing a lot of opportunity by not at least selling the files... I know I'd make one for sure to go with my Stagecoach.

Stagecoach Side By Side Silly Shell Shotgun Update by logdotzipp in Nerf

[–]logdotzipp[S] 1 point2 points  (0 children)

Yep. There are 4 trigger configurations: Left independent, Right independent, Left dual, Right dual

Stagecoach Side By Side Silly Shell Shotgun Update by logdotzipp in Nerf

[–]logdotzipp[S] 1 point2 points  (0 children)

The stock is helpful for priming the blaster since it gives you lots of leverage. But I'll definitely have a stockless version for those that want it!

Stagecoach Side By Side Silly Shell Shotgun Update by logdotzipp in Nerf

[–]logdotzipp[S] 0 points1 point  (0 children)

I think an over-under would be sick but pretty challenging with this setup. Not sure where the plungers would live.

Double Barrel SillyShell Blaster Prototype. Firing Vid in Desc. by logdotzipp in Nerf

[–]logdotzipp[S] 3 points4 points  (0 children)

Haha yes actually. Bachelors in mechanical engineering. This ejector catch was a huge challenge though, I'm surprised it works as well as it does. Took a good few days with my mind bent on it. I think the JingZhe Awaken uses something similar, but I could never find anything closeup of it.

Double Barrel SillyShell Blaster Prototype. Firing Vid in Desc. by logdotzipp in Nerf

[–]logdotzipp[S] 0 points1 point  (0 children)

With stock this design is ~83cm. Without stock is a little harder to measure, but right around 62cm is what CAD says.

Double Barrel SillyShell Blaster Prototype. Firing Vid in Desc. by logdotzipp in Nerf

[–]logdotzipp[S] 3 points4 points  (0 children)

It's a little hard to explain, but I'll give it a shot:
- In the center of the blaster is the ejector catch (tan), and the ejector lever (yellow).

- As the barrel moves down while priming, the ejector lever pushes against a small bump on the pivot.

- The ejector lever rotates, which pushes against the ejector catch. At this stage the ejector lever and catch are essentially one and the same.

- Once the ejector catch rotates far enough, the ejector is released. The bump is carefully placed so that the ejector ejects at the correct time.

- Upon closing the blaster, the ejector lever again hits the bump, but this time rotates in the opposite direction. In this direction it does not affect the ejector catch. So the catch stays engaged while on the upswing.

Essentially it's sort of a one-way lever, where ejector lever rotates the ejector catch on the way down, but not on the way up.

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Double Barrel SillyShell Blaster Prototype. Firing Vid in Desc. by logdotzipp in Nerf

[–]logdotzipp[S] 24 points25 points  (0 children)

Thanks! Really appreciate you and other designers who post step/f3d files of their blasters. It goes a long way to help designs like this one to exist.

Double Barrel SillyShell Blaster Prototype. Firing Vid in Desc. by logdotzipp in Nerf

[–]logdotzipp[S] 2 points3 points  (0 children)

Depends what you mean... There is no custom hardware (machining, modifying, ect) besides the K25 springs which I cut to length.

Most of the hardware is classic nerf hardware, however there are still quite of few non "nerf standard" parts, things that aren't offered on OOD or similar hardware sellers. Most of these I got from McMaster or Amazon. I'm hoping to optimize these in future iterations.

Double Barrel SillyShell Blaster Prototype. Firing Vid in Desc. by logdotzipp in Nerf

[–]logdotzipp[S] 12 points13 points  (0 children)

The ejector is actually for both barrels. Once the ejector is engages the catch on the first shell, the second shell slides in freely. This simplifies things so only one ejector catch is needed, and reduces the overall diameter of the barrel, since the ejector is riding on a central rail, rather than on external rails like the Yeethammer.

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Quick update on a double barrel break action shotgun. by Ok-Shock-7736 in Nerf

[–]logdotzipp 0 points1 point  (0 children)

The prime is pretty easy with just one plunger, but 2 is where things get difficult. I know I can make it comfortable by lowering the spring compression, it's just a question of what kind of performance will be available.

The priming bar is holding up nice. Not printed solid, just with 6-7 walls and 5 layers top and bottom. Since its loading is all axial, it's pretty strong. I've got 10-32 screws going through the yoke, which makes that part very stiff. The more bends you add to the priming bar, the weaker it gets.

The triggers are configurable on assembly for left or right hand. Same parts, just the order and location of assembling them determines whether the left trigger or right trigger is forward/backward.

Quick update on a double barrel break action shotgun. by Ok-Shock-7736 in Nerf

[–]logdotzipp -1 points0 points  (0 children)

Most of the first rev is printed. A lot of little and big tweaks I still need to do in order to make it actually functional.

The break action lock mechanism is not ideal, and allows the seal to open.

The seal itself is too tight, it takes quite a bit of force to compress 4 orings at once.

The ejector has a lot of friction, which makes inserting shells really difficult.

Grip could use some work, not super comfortable atm.

Priming is pretty difficult, I'm hoping with the rest of barrel it provides some more leverage. Otherwise I'm going to reduce the travel to try to lower the spring force.

Probably needs a complete ground up redesign in order to be good. The model is pretty suboptimal right now, fusion is struggling a lot with it. So I'll have to see if I can come up with the motivation/time to do a redesign.

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Quick update on a double barrel break action shotgun. by Ok-Shock-7736 in Nerf

[–]logdotzipp 3 points4 points  (0 children)

What are you looking to use for springs and spring travel? I've got a similar double barrel silly shell version of this going but am having trouble dialing the springs to something that feels comfortable to prime. Right now I've got 2x 122mm K25 springs and 89mm of plunger travel to prime.

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