Hy-Con cage refinements, Gen2 wheel models, etc.

So far what I have been testing and playing nerf with is very nearly the original version of the Hy-Con system. There has been, up to this point, only one 9.5mm gap wheel that has existed completely unchanged from the get go, and the "Beta" cage used by the Model Pandora development gun is basically the Protocage repackaged save for one fillet. I guess I did well enough, but make no mistake, this is far from finished.

Problem one is that I have been having incidences of a specific and aggravating malfunction with this cage, which has been occurring solely with used waffle darts (never anything else, especially not accustrikes). The failure mechanism is the foam being dragged around with the lag side of one of the flywheels after the contact zone and getting sucked into the little gap where the bore re-forms, created by the extremely concave wheel and the cylindrical flywheel cavity in the older Hy-Con cages. The thing then seizes up tight as a rock. Sometimes the dart can be unwound out the breech or muzzle by hand. Other times a rod is required. Not a good situation.

I was aware of this misfeature, as well as potential solutions to it, and it was my greatest uncertainty when I designed the original Hy-Con system. The reason for its persistence is or perhaps was that machined cages are or perhaps were planned down the road, and any internal geometry gnarlier than a cylindrical flywheel cavity would probably result in a significant cost increase and prevent a one-piece cage from being possible to assemble.

Unfortunately, this does not appear to be working out.

This blaster must shoot any common super/ultrastock ammunition, and it must be able to shoot garbage. It's allowed to chop or mutilate garbage in any way, and it is also allowed to have garbage accuracy and consistency with garbage as is the reality of garbage, but it is never allowed to stop firing and require attention to clear, even if the ammo is garbage.

And so the CADding begins again. I am holding off on further work on the Production T19's "Gamma" cage for the moment until I get the internal geometry of the Hy-Con cages nailed down and field tested. To that end, this is what I am calling "Beta Prime", a straightforward addition of the experimental feature to the old Model Pandora cage.

Note those protrusions - they stick down into the flywheel grooves, and fill that stupid little offending gap in so stuff hopefully can't get pinched in there and cause a mess. They have about 0.75mm clearance off the rims of a 9.5 wheel, so there is a bit of room left for the 9.0.

This is actually a feature the PFDL cage has had for a while now. It probably is overkill with the low envelopment there, nor does it seem to be necessary with high-envelopment smaller diameter systems like Eclipse, Ultracage and DrSnikkas cages that generally just have a cylindrical cavity and ignore that gap, but I may have discovered a case (high envelopment AND one of the largest diameter systems ever in practical use) where it is very, very necessary to have that little groove filler doohickey.

I should also mention my suspicion that this troubling malfunction is all the fault of waffle darts all along once they get used and the tips start getting loose - the root cause may be the waffle tip grabbing/sticking in the 14mm barrel and causing the foam to buckle or bunch-up behind at which point the lag sides of the wheels are going to nip the foam. I had the same exact jam happen when I was using TBNC David's FDL for one round and put a couple hundred rounds through it. The difference is that when T19 does this, the dart becomes a mangled, compacted, FUBARed shitshow. When the FDL did it, the dart was still pinched and the motors still locked up, but grabbing the dart and ripping it out, then dryfiring dislodged all the debris and restored functionality. That I am guessing is the limit to the value of the gap-filler doohickeys and the true solution is to not shoot those darts and use something else. I am having massive second thoughts on Accustrikes/clones - they are AWESOME in CQB and HvZ.

Anyway, here's the result when you add wheels:

Note the protrusion is asymmetrical. The motor mount side cuts it a bit closer to the wheel profile with a 45 degree edge there in the hopes of printing more easily.

You can also clearly see another related change - the cage no longer splits straight down the bore axis. The parting line was moved 4mm from the motor mount part toward the cover part. That gap filler protrusion makes assembly impossible if it is not entirely in the motor mount section of the cage. Note it also makes assembly impossible if the guards or anything else are integrated into the motor mount section without sufficient clearance and block the sides of the motor mount. You must be able to mount the wheel to the motor, slide the motor in from the side, and bolt it down to get the wheel rim past the protrusion.

There are also some minor external changes on the Beta Prime cage from the previous Beta. Guards were thinned by about half but are still quite robust, and some edges have fillets. No big deal.

I have also modelled a new series of wheels. Changes include more refined rim backside geometry, 0.5mm larger OD to take better advantage of the standard Hy-Con cage clearances and take the rim-to-rim clearance down to a nominal 0.5mm, a series of gap settings that presently range from 11mm to 9mm, and radiused rims rather than chamfered rims, which are a bit smoother and sacrifice less contact at the edges.

This one is a 10mm, incidentally. I have high hopes for 10mm with this system being quite competitive on velocity but easier on darts than the 9.5.

This cage has Gen 1 wheels. Note what happens with those rim chamfers. Also note what is considered a large rim clearance in this day and age, not a fitting thing for the original "100%" envelopment cage.

This one has Gen 2 - note softer edge provided by the fillet instead of the hard chamfer, and note the closer rims and generally much better fidelity of the hydrostatic compression profiles to the ideal circle.

Finally, since I didn't get any images of the real blaster that show the drivetrain guts of a T19, have a Model Pandora cross-section. Perhaps that will clear up some things.

Specifically, look right above the NEMA 17 mounting pattern and you can see the cavity where the crank web sits, and above that, the bolt guide rails. The bolt is completely 2-D like a sheet part (the proto one IS a PVC sheet part like the crank web), and is about 6mm thick. The limit switch bolts to the little perch behind there. The purple top cover forms the upper rails, capturing the bolt in there, and the rest is just a magwell, a closed breech guide and a cage and that's all there is to it.

The stepper motor's shaft is shortened considerably, before anyone asks.

More updates once I get my Prusa going. That's gonna be fun...