Saturday, December 16, 2017

T19 Prototype Build

I have rather insufficiently documented the progress of the Hy-Con flywheel system and its greater role in me going to clean-sheet blaster designs and exploring new tools like 3D printing, but that is in fact what is happening with me as of late. The main project here is called T19, following on from a T18 design that was put aside for later.

The key elements coming together here:

  • AC direct drive pusher, using a NEMA17 stepper motor, covered in the last post, as the drivetrain component.
  • the Hy-Con System as the ballistic component, including its associated motor/drive pairs.
  • My software package for integrated control of exactly such blasters.
  • A single-board modular controller architecture that just sort of designed itself as this project progressed.
  • A distinct design philosophy in terms of human factors/layout aspects that I found lacking or shoved aside in prior art. Examples are having a very tactile and consistent real trigger, a full length monolithic top rail, a trigger guard, conventional firearm-style trigger logic as opposed to FDL logic, etc.
  • A distinct feature/functionality philosophy best summarized as "You turn it on, you shoot it, and you turn it off". Rather than overcome varied roles with lots of options, controls and settings, I prefer versatility be inherent and all the software intelligence be buried under the hood. You shouldn't need, for example, selective fire. A combination of full auto mode only, superior trigger logic, good trigger hardware, and easily learned operator skill renders it one hundred percent objectively pointless.
Layouts vacillated for a while. T18 was to be akin to a "giant mutant alien Stryfe" - vertical plane cage and vertical plane drivetrain. It is still in the works... eventually. I just decided not to prototype and do Hy-Con field testing with it, but to design a simpler, cruder test-mule, and that, is T19.

The inspirations are:
  • The FDL series (the horizontal flywheel orientation).
  • Old school electropneumatic paintball markers, like the PVI "shoebox" Shocker and ICD Bushmaster 2000, for the packaging approach used to accommodate the NEMA 17 bolt motor and the electronics package while maintaining a clean top profile:

So I got CADding. Here are some models for printed parts (note magwell is a dummy part and is not used):

I had 3DK print these for me, since I am a lazy SOB and haven't built my own printer yet. That's next.

And it came together, with a bunch of handmade PVC buildup parts. I have referred to this design as "Model Pandora" for quite some time and it is unique as a testbed and meant only for that more or less. I'll just let the images talk for the most part.

Trivia: This magwell takes ONLY Worker 22-round mags. I wasn't about to iterate a design to fit multiple brands of mag for a handmade prototype.

This grip frame is derived from the one used on Prometheus. The frame is one solid piece, the trigger loads through a slot in the top, and the panels/scales are separable, much like firearm and paintball grips. The trigger switch is a full-size microswitch enclosed in a cavity under the panels, which also provides the trigger restoring force. Very short travel, perfect weight, great feel, and consistent trip point. I consider this one of my best achievements of the Prometheus project although it was at the time an afterthought.

SNW people, do not worry, I am not changing this grip at all. I am converting it to CAD models with accommodations for printing and assembly.

The battery setup on the Model Pandora is likely to remain a prototype thing. Production will have a stick pack in the tube.

I fielded it at the December 13, 2017 Tampa Bay Nerf Club match.

It did very well running waffle and accufake at 160-175 ish fps. Hy-Cons have some real snap to them, it is the "poppiest" flywheel system I know, and it's a lot of fun to shoot.

Overall malfunctions were only 1 during the whole day, but that was a SHREDDED dart resulting a flywheel lockup. Of note, this exact incident also happened again to me with 3DK's FDL-2X+ when I was running it in a round. I have a few theories as to what happened and it was probably either my fault (shot my own bunker at pointblank because there isn't anything on the front after the cage) or it was just shitty darts, but I will be doing a bit of work on the cage designs in the future to smooth-out the bore intersections to the fly cavities and reduce the potential for this type of malfunction anyway.

The Hy-Con/T19 system also proved itself capable of some great accuracy. It is hampered by poorly glued cheap darts, especially used ones, which can get decapitated or cause off shots (this is a nearly insoluble problem with 160+ fps singlestage systems by pure physics, aside from better tip bonding) but it generally shoots good/new darts very straight. After playing both blasters in this game, the T19 was doing slightly better despite its extra velocity than the FDL with 9.2 wheels at 155fps max which tends to have some veering going on downrange with waffle. The Hy-Con control bore is very slightly longer than the FDL, and the breech guide design also enforces the dart's coaxial position more rigidly than the larger FDL breech which might be doing something. Some people have theories about flywheel concavity, I don't know about that. Maybe.

Overall success! Next step is to redraw everything, convert all handmade bits to printables, convert the hand-wired controller backplane to an open source PCB, etc. and of course at the same time tuning will continue and behaviors of the blaster will only improve.


  1. Been waiting for this post for so long now! Absolutely blown away, but what's up with those ergos? Looks kinda funky, super high bore axis relative to the grip and stock, but maybe that's just me.

  2. Been waiting for this post for long now! Looks absolutely amazing. Bore axis looks very high, but maybe that's just me.

  3. Been waiting for a T19 blog post! Looks absolutely amazing, nice to see you’re cadding the T19/Prometheus grip. The bore axis feels kinda high but maybe that’s just me.

    1. This project is a severe departure from my past milsim-like approaches to layout and general blaster design in a number of ways, I expect *someone* will think it is weird as hell or be surprised that I designed it. This is a purpose designed original blaster. It isn't meant to imitate or carry on any artifice from anything else.

      The spatial relationship of the grip and the bore axis are set by the bolt motor and electronics package being under the drivetrain (see the old school paintball inspiration comment) to get these elements out of the way. The stock is positioned relative to the grip.

      You have probably heard me rant about bore axis. It's generally not about it being too high though, but too low (which is a VERY oddball nerf-specific thing, associated with Stryfes/Stryfoids, that just feels/handles/looks super strange and wrong). High bore axis, or in other words a stock that has substantial drop, is neither unprecedented nor inherently an ergo blunder. It would be a pre-modern way to design a firearm, but this is because modern firearms moved away from dropped stocks and toward inline ones to prevent recoil force from creating a torque that tends to make the muzzle rise when fired. Dart blasters don't recoil as much as firearms, obviously, and here the drop on the stock works out in another way, which is sight/optics positioning for comfortable aiming within the range and techniques used in tag sports. Note that the top rail on this horizontal-cage device is less than an inch over the bore. If the stock were inline, you would need a riser or other wasted height under sights.