Infernal BCAR - A Hardware Free Modular BCAR

A cheaper, fully printable, modular alternative to the Celestial BCAR. All the original angle and crush options are here as well as some additional angles that wouldn't error out my timeline. The customizable shroud designs return and a new 2 part roller design enables a drop in roller that mimics the flanged form of metal bearings. In place of fixed bearing arrangements are labeled individual segments with helical stepping to allow you to create helical arrangements or stagger them in other ways. A dart zone adapter is also provided, but using some barrel will greatly improve the durability.

Segments are named by degree, crush (lower, low, med, m-h, high, higher, ultra, u+, u++), and step in a helical configuration (segment-2step, segment-1step, segment0, segment+1step, segment+2step)

Using step -2 or +2 on angles higher than 12 not recommended.

Use either the V rollers or the 2-part flanged rollers (marked inner and outer) and test print for a proper fit

Tuning Tips:

Make sure the rollers are free to spin on the axle and against the standoffs. Use lower angles and higher crush for higher fps. Try staggering the bearings differently to most effectively spin the dart. Use porting segments to vent muzzle blast, space apart progressive twist setups to avoid twisting the foam at different rates, and to reduce friction from twisting while the dart is still exiting the barrel. Try 6 degrees or higher as a start for 200fps and below, or lower for above 200fps.

Printing:

All parts are printable without supports. Ironing and scarf seams can improve the finish on the rollers. Make sure to keep a clean plate or use adhesive when printing the rollers. 

The tighter versions of the rollers will be more precise, but use the looser ones if your printer isn't able to hold tolerances for it. If neither work, try increasing the x-y hole compensation just enough such that the roller can move about its axle (0.05mm increments). Check using only the rollers.

Assembly:

Fairly intuitive:

Use short segments of filament to fix the rollers into each segment. Check that they can move without inconsistent friction and sand the roller standoffs in the slot if they don't (pre 1.5). Press them into the shroud and secure with the cap. Print the shims and place them between the cap and stack if necessary.

For removing segments, use the provided tool or get 3 long 3mm pins and press them through the holes in the base.

Also check out the Celestial BCAR if you have f683zz bearings: https://www.printables.com/model/1317354-celestial-bcar

Extensions:

Each segment is 1cm tall, so just stretch the shroud to your desired length by scaling/copying/extruding the middle.

Updates:

-misc fixes day 1

-10-27-25: added cleaner shrouds

-10-28-25: Fixed issue with standoffs fillets not generating properly on certain angles.

-10-29-25: Fixed issue with slot width being inconsistent widths.

-10-30-25: Added looser fit mounts denoted L in 1.3 and even looser ones in 1.3.1

-10-31-25: Changed segment geometry (rev 1.5) to constrain rollers by the slot walls instead of by unreliably printed standoffs

-11-6-25: added small nubs to shrouds to better retain caps