Ceiling Storage Hoist, Block & Tackle

Splitting the bedroom into three levels — the folding staircase (HW-002) was the first piece of that — freed up floor area, but it also did something less obvious: it freed ceiling area, dead volume above head height that nothing was using. This project is the design for putting that volume to work: a hoist that lifts a storage tray up into the ceiling zone on a rope-and-pulley reeving and locks it there with a ratchet, so the tray hangs out of the way until it’s needed. Unlike HW-002, this one is a design study only — calculated and modelled, not yet built.

OVERVIEW & MOTIVATION

The −1 office level and the level-1 original floor are both tight on storage; the level-2 sleeping platform overhead is still under construction. Between the original ceiling and the new level-2 platform there is a strip of ceiling volume that is only reachable if something can carry a load up into it and hold it there without tying up a hand. A block-and-tackle hoist does that with no motor: the mechanical advantage comes entirely from sharing the load across multiple rope parts, and a ratchet-and-pawl on the hauling side holds the load with zero standing force once it’s up. The tray framing is primary here (bins, off-season stock, tools); a laundry drying rack on the same platform is an equally honest use of the same hardware — see Use Cases.

Design inputs (stated, not measured):

PARAMETER	VALUE	UNIT
TRAY_SIZE	1200 × 600	mm
RATED_LOAD	40	kg
LIFT_HEIGHT	1.6	m
REEVING	4:1	—
SHEAVE_EFF (per sheave, assumed)	0.95	—
ROPE_SF (assumed)	8	—

REEVING & MECHANICAL ADVANTAGE

Block and tackle is energy conservation, nothing more: the load is shared across N supporting rope falls, so the hand only has to supply W/N of the force — but the hand has to move the rope N times farther than the load rises, to pay out that much extra rope through N falls. Force goes down by N, distance goes up by N, and the product (work) is conserved, minus whatever friction the sheaves eat.

Here N = 4: the rope runs fixed-anchor → moving sheave 1 → fixed sheave 1 → moving sheave 2 → fixed sheave 2 → hauling tail → ratchet drum. That routes the rope over four rotating sheaves (the two moving-block sheaves and the two fixed-block sheaves the tail crosses); the anchor end is a dead knot, not a sheave, so it costs no friction.

Ideal hauling force:

F_ideal = W / N = (40 kg × 9.81 m/s²) / 4 = 392.4 N / 4 = 98.1 N

Real hauling force compounds the assumed 0.95 efficiency across all four rotating sheaves:

η_total = 0.95⁴ = 0.815
F_real  = F_ideal / η_total = 98.1 / 0.815 = 120.4 N

Rope travel: the hauling end must pay out N times the lift, always — that’s the same conservation law, and it’s the whole point of the reeving.

QUANTITY	IDEAL	WITH η = 0.815	UNIT
Hauling force, F	98.1	120.4	N
Hauling force	10.0	12.3	kgf
Rope travel per 1.6 m lift (N × lift)	6400	6400	mm

Real input work = F_real × rope_travel = 120.4 N × 6.4 m = 770.6 J against a useful output of W × lift = 392.4 N × 1.6 m = 627.8 J — the 142.8 J gap is friction across the four sheaves, consistent with η_total = 627.8 / 770.6 = 0.814 (rounds to the 0.815 above).

ANCHOR LOAD & RATCHET LOCK

Anchor load. The ceiling block doesn’t just react the 40 kg load — the hauling tail is also anchored back through the fixed block before it reaches the drum, so the ceiling fixing reacts the load plus the real hauling tension:

Anchor load = W + F_real = 392.4 N + 120.4 N = 512.8 N ≈ 52.3 kgf

That’s 30% over the bare load and it’s the number that actually sizes the ceiling fixings — a beginner sizing bolts to “40 kg” alone would undersize the anchor. Size the ceiling plate, lag screws, and joist engagement to 513 N with its own margin on top.

Ratchet-and-pawl. Holding is free once engaged: the pawl geometry must put the pivot such that the tooth’s reaction force at the contact point drives the pawl into the tooth root, not out of it — i.e. the line from pawl pivot through the contact point must fall on the engagement side of the tooth face, so any load spike only seats the pawl harder rather than camming it out. Tooth pitch and drop increment, for a 45 mm drum with 20 teeth:

Pitch angle  = 360° / 20 = 18°
Drop before next tooth catches = 2π × 45 mm / 20 = 14.1 mm

So the worst-case free-fall before the pawl catches is 14.1 mm of drum rotation — small, but real, and it should be stated on the design rather than assumed away.

Rope. Rope is a wear item, and rigging a load-bearing hoist is genuinely over my head as a first attempt — this is a case for buying a rated product, not fabricating one. Minimum spec: a rope rated for at least

Required MBS = RATED_LOAD × SF = 392.4 N × 8 = 3139.2 N ≈ 320 kgf

with visual inspection before every use (fraying, glazing, chafe at the sheaves), a secondary cleat backing up the ratchet so the load is never held by a single mechanism, and a standing rule: never stand under the load, loaded or not.

PARAMETRIC MODEL

build-glb.mjs rebuilds the whole assembly from the same parameter block quoted above (tray size, rated load, lift height, reeving, drum radius, tooth count). Every part is an oriented box passed to the shared writeGLB() helper (../_glb.mjs); the four rope falls and the hauling tail are not placed by eye — each segment’s length and angle are solved with Math.hypot() / Math.atan2() from the live sheave coordinates, the same approach the live SVG animation uses to keep the falls visibly shortening as the tray rises and the tail paying out at 4× tray speed. The exported pose is mid-lift (55% of the 1.6 m travel) with the ratchet mid-cycle. Output: 37 boxes, 444 triangles, validated as a well-formed GLB.

STATUS & NEXT STEPS

Design study only — calculated and modelled, not built. Next steps before any hardware: verify the actual ceiling structure (joist size, spacing, fixing type) can take the computed 513 N anchor load with its own safety margin, then select a rated rope and pulley blocks against the 320 kgf minimum breaking strength and the 4:1 sheave count worked out above. No fabrication has started.

USE CASES & APPLICATIONS

Garage bike and kayak hoists, ceiling-mounted laundry drying racks (same tray, same reeving, different cargo), workshop material handling up to a mezzanine, theatre fly systems, and sailing halyard/tackle systems all use exactly this trade: mechanical advantage buys force at the cost of distance, never energy. Every version of this idea runs into the same two things beginners underestimate — the anchor sees more than the bare load, and the rope is the part that fails first, so it gets the safety factor.

FILES

Source: build-glb.mjs (parametric box model, run with node build-glb.mjs from its own folder) and ceilinghoist.js (live animated front-elevation drawing, registered as the ceilinghoist mechanism builder). The 3D viewport above embeds the exported mid-lift GLB.