A load slides when braking plus slope exceeds friction, and friction on wet planks is low: a 200 kg load with a friction coefficient of 0.15 (assumed) going down a 10% slope needs 491 N of restraint to survive a hard stop of 0.3 g, which is 2-3 ropes of 10 mm used at their 5:1 working load, and a 600 kg load needs 5-8. Block the load against a headboard or chocks so that no rope has to hold it by squeezing it down, tie each item separately, and test the friction of your own planks by tilting a board.
Part of Logistics & Load Planning
Holding cargo in place on a cart or pack animal with ropes, lashings, chocks and dunnage, and sizing the restraint to the forces a stop and a slope produce.
A Load Needs Blocking First And Ropes Second
The parent article says unsecured loads shift, and shifted loads break, fall off, unbalance the vehicle and injure animals. It lists five techniques: roping, a rope thrown over the load, looped under the bed and tied off, with at least two ropes per load, one at the front and one at the rear; chocking, wedging blocks of wood between items and the wagon sides; dunnage, lumber or poles placed between cargo layers to separate them and add friction; lashing, each barrel, crate or bundle tied separately to the bed; and a net or tarp to keep small items from bouncing out.
The parent gives no loads for the ropes. The arithmetic below shows that two ropes is a minimum for a light load and not a rule for any load.
What You Need
- Rope of known strength. Testing and Storage gives a 10 mm rope as breaking at 150-250 kg with a working load of 30-50 kg at 5:1. See also Rope Strength Testing.
- Chocks, a headboard and side boards to block movement.
- Dunnage for separating layers.
- A tilting board — to measure friction.
Method: Secure A Load
Step 1: Weigh the load and find the friction Place a sample item on a plank of the same wood as the bed and tilt the plank until the item just slides. The coefficient of friction is the tangent of that angle. Do it dry and wet.
Step 2: Block against forward movement Put the load against the headboard. Put chocks between items and the sides.
Step 3: Tie each item Lash each barrel, crate or bundle to the bed separately; then rope the whole load.
Step 4: Pull ropes against the movement, not just down A rope that runs from the load’s top forward to the bed’s front resists sliding directly. A rope over the top only adds friction.
Step 5: Re-check after the first kilometre Loads settle and ropes slacken. Re-tension.
Worked Example: What A Hard Stop On A Slope Demands
Inputs, mine: load of 200 kg; friction coefficients 0.3 for dry wood on wood and 0.15 for wet, both assumed, so measure yours with the tilt test (a coefficient of 0.15 is a tilt of 8.5 degrees, and 0.3 is 16.7 degrees); a hard stop of a = 0.3 g, which is 2.9 m/s²; a descent of 10%, so sin θ = 0.0995 and cos θ = 0.995. For scale, a cart at 5 km/h (1.39 m/s) stopping within 1 m decelerates at 1.39² / 2 = 0.97 m/s², or 0.10 g, and at 7 km/h (1.94 m/s) in 1 m at 0.19 g.
Forward force the load wants to move with = m × (g sin θ + a), and friction available = μ × m × g × cos θ.
200 kg load.
- Level, dry: demand 200 × 0.3 × 9.81 = 589 N; friction 0.3 × 200 × 9.81 = 589 N; no margin at all.
- Level, wet: demand 589 N; friction 294 N; shortfall 294 N (30 kgf).
- Down 10%, dry: demand 200 × (9.81 × 0.0995 + 2.94) = 784 N; friction 586 N; shortfall 198 N.
- Down 10%, wet: demand 784 N; friction 0.15 × 200 × 9.81 × 0.995 = 293 N; shortfall 491 N, which is 491 / 9.81 = 50 kgf.
Ropes for the wet descent. A 10 mm rope’s working load is 30-50 kgf, which is 294-490 N. A rope tied at 45 degrees to the bed gives a horizontal restraint of 0.707 times its tension: 30 × 0.707 = 21 kgf to 50 × 0.707 = 35 kgf. Number needed: 50 / 35 = 1.4 up to 50 / 21 = 2.4, so 2-3 ropes. For a 600 kg load the shortfall in the same case is 1,473 N = 150 kgf, which needs 150 / 35 = 4.2 up to 150 / 21 = 7.1, so 5-8 ropes. Two ropes per load, as the parent says, is the minimum for a load of this order and is not enough for 600 kg.
Why not just press the load down? To hold the 200 kg load by friction alone, the ropes would need a vertical tension T with 0.15 × (200 × 9.81 × 0.995 + T) = 784 N, so T = 5,227 − 1,952 = 3,273 N, or 334 kgf. No rope pulled by hand will give that. Blocking works instead: a headboard or chock takes the full 784 N directly.
Common Mistakes
- Relying on two ropes for a heavy load — see the arithmetic.
- Tying over the top only — it adds little friction. Run ropes against the direction of movement and block the load.
- Wet planks — friction halves in this example; wet loads and wet beds slide.
- One rope for a whole stack — if it fails, everything goes. Tie items separately.
- Using rope at its breaking strength — the 5:1 working load is the limit. Natural-fibre rope loses strength when wet or old.
- Not re-tightening — loads settle, and slack ropes let the load shift.
Safety
A sliding load can crush the animal or driver
On a descent a load that breaks loose slides forward into the animal and drives the cart onto it. Block the load, test every rope, keep braking gentle on slopes, and walk the animal down the steepest sections. Never stand in front of a load being untied; cut slack ropes from the side.
What’s Next
- Learn next: Terrain Assessment — the grades and surfaces that set the braking demand
- Combine with: Cart & Wagon Loading — balance before securing