Shop Towel Roll Holder - Backstage cart lip (one piece, strongest)
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What it holds: Shop towel roll up to 130 mm across, via end caps; thumbscrew required; full roll 134 out / 140 down

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
  - clip_OC_L_towel_arm.stl  (supports: no)
  - clip_OC_R_towel_arm.stl  (supports: no)
  - clip_OC_L_towel_arm_hood.stl  (supports: no)
  - clip_OC_R_towel_arm_hood.stl  (supports: no)
  - clip_OC_cap38_towel_end_cap.stl  (supports: no)
  - clip_OC_cap44_towel_end_cap.stl  (supports: no)

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: One piece, strongest: native Magliner/Backstage 3.4 mm cart lip mount, REQUIRED M5 heat-set insert + nylon-tipped M5 thumbscrew. Arms: print the left and right (plain, or the hood pair for rain). End caps: print TWO of the one that fits your core (cap38 for 1.5-1.6 in, cap44 for 1.75 in).

HOW IT WORKS
  Spills, wet cases and greasy grip hands: a roll on the shelf rolls off or gets dirty. This holder hangs a blue shop-towel or paper-towel roll along the cart side, below the deck, out of the dirt.
  Parts: print a left and a right arm (plain or with the rain hood) and two end caps of the size that fits your core.

  - Arms: each drops onto the lip on its own mount block and locks with an M5 thumbscrew (required here, see below).
  - End caps, two sizes: cap38 for 1.5 in and 1.6 in cores (37.5-41 mm inside), cap44 for 1.75 in cores (41.5-46 mm). Scott shop towels come on 1.5 in or 1.75 in cores; measure yours across the inside with a ruler.
  - Each cap is a slotted collet: eight 1.6 mm fingers with a grip band near the tip flex in as you push the cap into the core, and the core then stops on a 45 degree shoulder. So the cap always sits at the same depth (within about 2 mm), however hard you push it.
  - No loose rod to bounce out.
  Setting up (once): push a cap into each end of the roll. Drop the left arm onto the lip and tighten its thumbscrew. Hang the roll's left stub in the left arm's hook, slide the right arm along the lip until its hook takes the right stub with the cap discs just touching the arm plates, then tighten the right thumbscrew. For a 250-280 mm roll the arms' outer faces end up about 276-314 mm apart.
  Changing the roll: hold the roll level, line the two cap stubs up with the arms' front openings and push it toward the cart. The stubs click past a sprung detent (0.7 mm) and then drop 4.5 mm into a closed seat. To take it off, lift slightly and pull it out past the detent. Move the caps to the new roll.
  Why it stays on: the roll's weight sits in a closed hook. A bump that lifts the roll only pushes the stub up against the detent. To escape, it would have to rise 4.5 mm, move 15 mm straight out from the cart past the detent, then clear the arm. The arms are separate clips, so the thumbscrews are what keep them from walking apart along the lip on a rough push. With both tightened, the spacing cannot change and the caps cannot pull out of the core.
  Light drag: each stub rests in a 50 degree V seat, so the roll's own weight presses it onto two flanks. The V seat adds a little drag, most noticeable on a full roll (it fades as the roll gets lighter). That keeps a full roll from free-spinning on a bump. Tear a sheet with a quick downward snap; a slow pull just unrolls more paper. Not yet tested with a real roll, so check the drag on your first print.
  Rain hood (optional): the hood arms carry a curved hood half each, 178 mm long. The right half is slightly larger, so the two halves telescope over each other and overlap for any spacing between the arms' outer faces from about 190 to 336 mm, which covers every roll the caps fit. The hood keeps rain off the top and back of the roll. Its front edge is set back so the roll still slides in.
  Takes rolls up to 130 mm across (blue shop-towel rolls and standard paper towels; jumbo paper towel rolls over 130 mm will not fit), about 279 mm long. A full 130 mm roll clears the arm's own mount block by 3 mm while you load it.
  Cart facts

  - Arms stick out 102 mm from the cart side (hood arms 122 mm). A full 130 mm roll sticks out 134 mm
  - Arms hang 90 mm below the deck; a full 130 mm roll hangs 140 mm below the deck
  - Needs 45 mm of flat cart side below the lip at each arm (30 mm wide). Anything lower is set 2.5 mm back from the cart
  - Nothing of the arm sits higher than the 42 mm mount block (the hood top is about 15 mm above deck level, outside the cart)
  Retention: held by gravity unless you fit the M5 thumbscrew. For this holder the thumbscrew is required on both arms, because it is the only thing that locks the spacing between the two separate arms. Press a short M5 heat-set insert (6.4 mm hole, 9 deep) into the deck-side face of each arm's inner flange (one per arm), and use a nylon-tipped M5 thumbscrew to clamp the lip. Check first that your lip is at least 16 mm tall.
  Fits: Backstage Equipment and Magliner-style carts with a 3.4 mm upright shelf lip. The mount drops onto the lip from above: 3.7 mm slot (0.3 mm clearance), 26.6 mm deep with a round end, 0.5 mm chamfers at both slot ends.

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/#oc-l-towel-arm

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.
