Celestial BCAR

About:

BCAR with aggressive venting and lots of options. Inspired by the Flag and Armor CNC BCAR and drawing ideas from Thantacles' RIPPCAR theory.

Recommendations:

>7 degrees low for up to 180fps, 6 degree med/high at 200, 5 degree high for 250, 4 degree high for 300. Use Ultra crush only on especially tight bore configurations.

I personally use Countertwist, M-H/High crush, 5-6 degrees on most of my blasters. The straight bearing ones offer more porting but less varied points of contact on darts.

Printing: 

Printable without supports. Print muzzle down for helical, straight, and ripjaw versions; Print muzzle up base down for countertwist versions to save on filament, muzzle down with supports for slightly better accuracy on the bearing standoffs. Try sanding the standoffs if bearings don't sit straight.

V7:

Easier to print and assemble. chamfers on the pillars should help prevent warping on corners and the bores should take very little resistance to screw into.

Some labels were initially exported incorrectly but they should be fixed now. Let me know if there is an error.

Shrouds:

Print muzzle down without support. Glue/brims or turn on support if your printer struggles. 

Use the tight rear cap unless your printer has weak tolerances. Try to align the venting with the core so it vents easier and offers the pillars a little protection.

Step provided for customization, whether you recombine existing parts or deboss your own details. Includes extra elements I wasn't satisfied with.

BOM:

• 12+ f683zz bearings

• 12+ m3x8-10 flat head screws (flexible. can take other m3 screws lengths and head types as long as they secure the bearing. flat head recommended for optimal centering since the threading isn't always tight enough)

• 2-3 016 o rings (optional)

Assembly notes:

-2 o rings is sufficient and much easier to mount. use a twisting motion to ease it off barrels.

-Take some care to screw straight because plastic is soft and can let the screw go slightly off. Should be less of a problem in V7 now that the bore isn't comically tight and doesn't force you to tap all of it.

-Don't crank the screw in. Turn until you feel the resistance jump and stop so you don't mash the standoff flat or jam the outer race of the bearing into the print.

Updates:

• 6-4-2025: added V5 with labels and low/high crush, angled variants

• 6-9-2025: added progressive twist variant

• 6-26-2025: V6; increased pillar width to reduce bridging challenges and increase strength; increased low crush versions slightly to have reasonable contact; added a few more angles and a higher crush option

• 7-16-2025: added misc and 24 degree progressive variants

• 8-5-2025: added 0 degree variants, longer straight variants, lynx keyed variants

• 8-15-2025: added more variants and countertwist

• 8-17-2025: added V7 (More reliable printing, wider bearing standoffs, easier assembly/looser screw holes) and more exhaustive combinations

• 8-20-2025: added Ripjaw Rev 2 (Progressive twist)

• 8-21-2025: added shrouds

• 2-28-2025: found an error in the helix formation of helical variants. fix WIP

B.S. theory:

1. Spinning helps mitigate asymmetry in our cheap darts, worn or not.

2. Slipping of darts against rifling causes fishtailing, not strictly the angle of rifling, as evidenced by Andromeda (or maybe not? Horrible fishtailing with it on used darts. Maybe a helical issue?). Increasing crush helps reduce slipping with more aggressive angles. However, past a certain point, it seems to destabilize darts if they aren't exiting an especially tight bore, possibly perturbing the foam too much.

3. Friction from darts partially in the barrel or from a tight bcar bore also facilitate slip against the bearings, so spacing bearings out and using a loose bore should help.

4. Darts engaging with the barrel and bearings or different angled stages of bearings at the same time introduces friction and potential for slipping because the foam can only accommodate so much twisting on its body, so progressive rifling needs to be spaced to reduce engagement with multiple stages at the same time while ensuring the dart is constrained. This can take up a lot of space, so several closely packed stages with the same angle is adequate in a small form factor.

5. Helical vs Straight/Inline: Inline bearings engage with more varied parts of the dart's body and are more effective for spinning and handling uneven darts. Helical may have reduced potential for slip by digging an initial path for bearing to follow and only pressing on the dart along those paths whereas inline may leave foam pressed near subsequent bearing paths, which may facilitate slip, especially in the failure case where the dart completely slips against the first stage. Countertwist attempts to address both by arranging bearings in a reverse helical configuration such that each stage grabs new foam while being spaced away from where previous stages have already disturbed.

6. Muzzle blasts destabilize darts, so it should be vented before the dart exits the device.

Misc notes:

• Bore is 14mm to ensure darts aren't expanded by air to drag along the walls like in a GFZ BCAR or Andromeda

• Countertwist's reverse staggering is fixed rather than angle dependent in part for ease of designing/exporting and partially to ensure each successive stage is offset a minimum number of degrees in reverse regardless of whether the previous effectively spun the dart.

• V5/6 is denoted by helical/straight bearing arrangement, tension if printed friction fit, high/med/low crush, and angle.

• V6 or earlier: Slow print speeds as it builds the 45 degree overhangs by the top of pillars if it fails there on PETG, or turn on supports. Take care in assembly to keep the screw straight. You’ll feel less resistance the straighter it is.