Bench tools

These tools stay on the bench. They are not airframe parts, so the print hold does not apply to them (Ryan, 2026-10-11). The procedure that uses them is Make the keel antennas, step by step; the short form is step 8, cassette tuning, in Place the antennas.

The coil winder turns a LoRa coil former so that the wire goes into its groove at the same pitch on each turn. It also counts the turns. The dipole gauge cuts and bends each ELRS dipole arm to the same length. Before, the turn spacing and the arm length came from the hand, and these changed the tuning from one antenna to the next.

The coil winder Mk2

Ryan approved th-blender’s coil winder Mk2 on 2026-10-12 (tools/make_coil_winder_mk2.py, 3d4565d9). It replaces the Mk1 cradle.

Two 4 mm steel frame rods join the two cheeks at the back. The Turns Scale joins them at the front, and the Base Beam below. The beam slides up into dovetail sockets in both cheeks (Ryan, 2026-10-14). The frame rods also carry the carriage.

A spring beam cut in the head cheek presses a nub into four notches on the Head Hub. The crank clicks at each quarter turn. One click is one tick on the former.

Part	Quantity	Function	Print face
Head Cheek	1	Holds the Head Hub and the detent spring beam. The turn directions are moulded on it: PORT counter-clockwise, STBD clockwise, seen from the head end	Inner face
Tail Cheek	1	Holds the Tail Hub, and the spring beam that presses the brake pad on the Spool Drum	Inner face
Head Hub	1	The cup, and a half key that fills the lower half of the former’s anchor slot. The wire end goes in the upper half. The four detent notches are on its sleeve	Square end
Tail Hub	1	The same cup and half key on a longer sleeve. Its key goes in above the axis. It slides 4.5 mm back on its knob, so that you can put in a former and remove it	Square end
Crank Wheel	1	Turns the Head Hub. It goes on the hub’s square end in one position only, so “0” under the pointer always means the half key is upright, below the axis. A knurled rim and four dial ticks	Inner face
Crank Handle	1	Turns freely on an M3 x 20 pin in the Crank Wheel	Standing on an end
Tail Knob	1	Pulls the Tail Hub back to load a former	Inner face
Carriage	1	Slides on the two frame rods and stays where you leave it. Its brass-tube eyelet feeds the wire at the height of the axis, and its pointer reads the turns laid on the scale	Head end face (a face override in the slicer)
Turns Scale	1	0 to 4.8 turns, a tick at each quarter turn from the anchor end, and FEED GAP at 4.8 turns (49.5 mm). FEED GAP and TURNS are raised, in a second colour (Ryan, 2026-10-13)	Underside, on its own plate
Base Beam	1	Joins the two cheeks from below. Its dovetail ends slide up into the cheeks’ sockets, and four M3 x 16 screws go up through it into the cheeks	Underside (the counterbores down)
Spool Cone	2	Hold the wire spool on the spool rod	Large end
Spool Collar	1	On the spool rod against the inner face of the tail cheek. With the Spool Drum it stops the spool rod in both directions, so you can pull the spool rod out to change a spool	An end face
Spool Drum	1	On the tail end of the spool rod, against the brake pad	Outer face
Foot (TPU)	4, and 2 spares	Snaps up into a 3.5 mm hole in a foot flange, two under each cheek. Pinch the barb to remove it	Underside of its pad, the barb up
Brake Pad (TPU)	2	Snaps over the brake tab. The Spool Drum presses its sprung skin	Cheek-side end face (a face override in the slicer)
Brake Pad +0.4 (TPU)	2	The same pad, 0.4 mm thicker, for more drag on the wire	Cheek-side end face (a face override in the slicer)

Item	Value
Plates	pla-Coil Winder Mk2 for the PLA parts, pla-Coil Winder Mk2 Turns Scale (2 colour) for the scale (one filament change, so stay at the printer), and tpu-Coil Winder Mk2 Feet and Brake Pads for the six feet and four brake pads, each with its bed plan
Material	Plain PLA on the second Core One+ (Gen 2); the feet and brake pads in TPU 95A on the same printer. All PLA types are satisfactory, because the tools do not fly
Bought parts	Three 4 mm steel rods (two 128 mm, one 142 mm; cut 7 mm off a 135 mm rod you already have), a brass tube 1.5 mm OD x 1.0 mm ID x 6.5 mm, two M3 x 12 hub screws, four M3 x 16 beam screws, and an M3 x 20 screw and nut. A self-adhesive felt pad (6 x 8 x 1.6 mm) is optional, in place of the TPU brake pad if the spool jerks. They are in the parts list
Estimates	About 4.6 N on the detent nub between clicks, about 0.6 N to slide the carriage, about 0.2 to 0.6 N of wire tension from the standard brake pad, and about 1 to 3 N to snap a foot in. These come from beam formulas (th-blender) and are not measured

The ELRS dipole gauge

Tool	Quantity	Function	Print face
ELRS Dipole Gauge	1	Two 1.15 mm channels hold the two 18 AWG arms: 27.4 mm each, plus 2.0 mm for trim. A 1.6 mm feed gap is between the channels, with a shoulder at each feed end to bend the wire over and a step to cut the tail flush against (no kerf since W18), end stops at the tips and 1 mm marks over the trim length	Underside

The gauge is from tools/make_coil_tools.py (th-blender, 6dc7468). It was printed on the plate pla-Coil Winding Tools (job 22), with the Mk1 cradle.

The groove coupons are test prints and the coil formers are flight parts, both in PETG. Test prints are also exempt from the print hold, but the formers wait for Ryan’s go (Ryan, 2026-10-11). Print the Antenna Groove Coupons first and find the narrowest groove width that holds the 20 AWG wire. Do not print the formers before th-blender sets them to that width (step 2 of Make the keel antennas).

The winder and the gauge in 3D

The 3D view shows the winder assembled, with a port LoRa Coil Former on the axis and two turns laid. Drag to turn the model.

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Parts

Coil winder Mk2, assembled

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Parts

ELRS Dipole Gauge

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Withdrawn tools

These files are still in parts/. Do not print them.

Tool	Withdrawn	Reason
Coil Winding Cradle Base, two Coil Winding Thumbwheels and Coil Winding Wire Guide (the Mk1 cradle)	2026-10-12	Replaced by the coil winder Mk2 (Ryan). They were printed as job 22. The ELRS Dipole Gauge from the same job stays in use
Channel Drill Guide, port and starboard	2026-10-10	The guide aimed a drill at a bore that is the seat of the 8 mm wing spar, not a wire channel. The motor wires use the wire channels ahead of the front spar
Strobe Window Jig Base and Strobe Window Jig Press	2026-10-11	The keel strobe windows are now flat pieces cut from 1 mm clear sheet, so no bending is necessary (Lights)