Cart Cooling-Towel Bar with Gravity Ball Wind Locks and Snap-On Pinch - Backstage cart lip (one piece, strongest)
======================================================================

What it holds: Keeps a cooling towel wet, aired and on the cart. Hang it open from two marble locks, or drape it and snap the pinch clip on: either way the wind can't take it.

PRINT SETTINGS
  Filament:  PETG
  Walls:     5
  Infill:    35% gyroid
  Orientation: the files are already oriented for printing. Put them on the plate as they load;
               don't rotate them.

FILES AND SUPPORTS
  - H_QC_towel_bar_lip.stl  (supports: no (unless your slicer warns))
  - QC_bar.stl  (supports: no)
      how it lies on the plate: lying on its flat (the file is oriented), no supports
  - QC_cap.stl  (supports: no)
      how it lies on the plate: head down, print 2, no supports
  - QC_pinch.stl  (supports: no)
      how it lies on the plate: on its side (profile on the bed, the file is oriented), print 1-2, no supports

HOW IT MOUNTS
  BACKSTAGE CART LIP (ONE PIECE, STRONGEST)
    The cart-lip slot is printed into the holder, so it is one piece and as strong as it gets.
    Hold it tilted, hook the slot over the upright lip on the edge of a Magliner / Backstage-style cart
    shelf, and rock it down until it sits flat against the side.

    Notes for this holder: Strongest: one piece with the Magliner / cart-lip block, the holder fused to an 8 mm back plate that bears on the cart side down to the holder bottom. Sits at the same height as the swappable version on the Magliner adapter, 7 mm closer to the cart. Fit 2 M5 heat-set inserts + M5 thumbscrews. Prints upright, floor down like the swappable version; use build-plate-only supports under the 14 mm deck-side flange of the lip block only. Bar, marble-port caps and pinch clip are the same for every version.

HOW IT WORKS
  An evaporative cooling towel only works if it's kept wet and open to the air. Wadded in a bin, it dries out or goes sour. Left on a cart rail, it blows away. This bar holds it open, standing 57 mm off the cart so air gets all the way round, and locks it against the wind in both ways of hanging it.
  Two ways to hang it, both locked:

  - Banner: push the two top corners up into the ball locks and let it hang fully open. This is the best airflow, and the towel drips straight down, clear of the cart.
  - Draped: fold the towel over the 182 mm bar with the long side hanging outboard (away from the cart, so the wet tail doesn't soak the cart side), then push the QC_pinch clip straight down over it at mid-bar. It snaps under the bar's widest point and squeezes both sides of the towel against the bar. When no towel is on, the clip parks on the bare bar.
  The ball lock (the fun part): each pod under the bar holds a 16 mm glass marble on a ramp. Push a fold of towel up through the slot: the marble rolls up out of the way. Let go: it rolls back down and pinches the towel. The harder the wind (or anyone) pulls down, the tighter it grips. To release, push up and slide the towel out sideways through the tall side slot.
  Parts: `H_QC_towel_bar` (spine, arms and two lock pods), `QC_bar` (a D-shaped bar: slide it in through the right arm and it snaps out of the left arm with a click; the flat stops it turning), `QC_cap` (print 2) and `QC_pinch` (print 1 or 2). Drop a 16 mm marble (or a 5/8 in steel ball) into each pod through the round port on the outside of each arm, then press a cap in, point up.
  Small parts: the marbles are a choking hazard for small children. Keep the caps pressed fully home; a drop of glue makes them permanent.
  Different from our shop-towel roll holder: this one is for one towel kept wet and open.
  Mount: a DOCK tongue on the back (a 38 mm, 45 degree dovetail with a click latch). It drops into any DOCK carrier adapter in this collection: the Magliner/Backstage 3.4 mm shelf-lip adapter (A_MLN_lip), the ToughBuilt bar adapters (A_TBB_bar) or the 19-32 mm tube adapter (A_TUBE). Push the latch pad and lift to swap holders one-handed. Nothing on the holder rises over the latch pad or the lock screw. The adapters are a separate download.
  Cart facts (on the Magliner lip adapter)

  - Sticks out 96 mm from the cart side
  - Hangs 11 mm below the deck; the holder top is 47 mm above it; the bar and arms rise 13 mm higher at the ends, 90 mm or more off the centreline
  - Part size 88.0 x 200.0 x 58.0 mm (out x along x up)
  - Bar about 23 g, caps and pinch clip about 2 g each
  - Hardware: 2 x 16 mm glass marbles or 5/8 in steel balls

OTHER MOUNTS
  The same holder also comes ToughBuilt bar (one piece), Dock (swap between mounts), Mountless (desk, shelf, case or screw to a panel). Pick the mount on the site: https://cart-tools.sdos-placeholder.workers.dev/#qc-towel-bar

TEST THE FIT FIRST
  Carts, bars and tape rolls vary a little. Before a long print, print the small fit test from the
  Test pieces section of the site (or this part at low infill) and check it on your own gear.

Not affiliated with or endorsed by Magliner, Backstage Equipment, ToughBuilt, Milwaukee, Hollyland, Eartec, Sekonic, Inovativ, Matthews or Manfrotto. Brand names only say what a holder fits.
