BH Motion Base Interactive

01 — Platform parameters

Base structure

Total platform weight (tonnes)26 t

Half-width from ridge (ft)12 ft

Ridge height (ft)3 ft

Number of winches4

Safety factor2.0×

02 — Load imbalance

Right-side pre-load

Extra weight on right side. 0% = perfectly balanced · 100% = right side tips to floor on its own.

Pre-load level29%

Rest tilt angle 4.2°

Extra torque 6,895 kgf·m

Left-side counterweight

Counter-torque on left side. 100% = exactly cancels the pre-load. Can go up to 150%.

Counterweight level0%

Net tilt at rest 4.2° (right)

Torque cancelled 0 kgf·m

Torque balance — right vs left

Right torque

30,669 kgf·m

Left torque

23,774 kgf·m

Net imbalance

+6,895 kgf·m

RIGHT-HEAVYNet imbalance: 29% of base torque still tips right. Increase counterweight to reduce winch demand.

03 — Pulley rig configuration

Floor-mounted winch + redirect pulley

Rig type

Pulley anchor height above floor (ft)15 ft

Pulley horiz. offset from platform edge (ft)0 ft

Cable friction loss per sheave (%)3%

⚠ Cable angle is critical. Pulley should be directly above the platform edge (0 ft offset) for maximum efficiency. Any horizontal offset reduces the vertical pull component.

04 — Results

14.5°Max tilt angle (full travel)

4.2°Platform rest angle (pre-winch)

97%Rig efficiency (angle + friction)

6,701 kgfBaseline force (balanced)

+1,943 kgfExtra due to net imbalance

8,644 kgfTotal winch force required

2,161 kgfPer winch (bare)

4,322 kgfPer winch (with SF)

9,529 lbPer winch (lb)

5,000 kgRecommended rating

Pre-load active with no counterweight. Winches working at 129% of baseline.

05 — Live diagram

Platform cross-section · side view (not to scale)

06 — How it works

Platform geometry & tilt mechanics

The platform is a steel base plate (24 ft wide × 40 ft long) balanced on a central steel ridge 3 ft high. The ridge runs along the full 40 ft length, dividing the width equally — 12 ft on each side. When perfectly balanced, no force is needed to hold the platform level.

When a force tilts the platform, the right side descends and the left side rises. Maximum tilt occurs when the right edge touches the floor. This angle is determined by: sin θ = ridge height ÷ half-width. For the default setup: sin θ = 3 ÷ 12 → θ = 14.5°.

The key insight: for a uniformly loaded, balanced platform, the winch force required is constant regardless of tilt angle — the cosine terms cancel out in the torque equation.

Pre-load & counterweight torque balance

Pre-load represents extra weight added to the right side of the platform. It creates an additional clockwise torque about the ridge. At 100% pre-load, the right side would naturally rest on the floor without any winch force — the extra weight alone tips the platform fully.

A counterweight on the left side creates opposing (anti-clockwise) torque. The counterweight percentage is relative to the pre-load torque: 100% counterweight exactly cancels 100% of the pre-load. Setting counterweight above 100% over-compensates and the platform tips left at rest.

The optimal strategy: match counterweight to pre-load (set both to the same effective torque), returning the platform to a balanced state. This reduces winch requirements back to baseline, potentially saving you from needing larger-capacity winches.

Floor-mounted winch & pulley rig

The 4 winches are bolted to the floor and use steel cables routed through overhead pulleys to lift the right side of the platform. A single redirect pulley provides no mechanical advantage — it only changes the cable direction. Block and tackle arrangements (2:1, 3:1, 4:1) reduce the force each winch must apply, but require proportionally more cable to be wound.

Cable angle is the most critical rig variable. The pulley should be positioned directly above the platform edge (0 ft horizontal offset). Any horizontal drift reduces the vertical pull component — a cable 30° from vertical delivers only 87% effective vertical force, requiring the winch to work 15% harder.

Each pulley contact point introduces friction losses (typically 3–5% per sheave for well-maintained steel wire rope on a lubricated sheave). This loss compounds: a 4:1 block and tackle with 4% friction per sheave delivers about 85% efficiency overall.