# Counter Crane (DD-687) > A crane tips over when the overturning moment (the load's weight times its distance from the tipping line, plus wind and slope effects) exceeds the stabilizing moment from the crane's own weight and counterweight. Counterweights sit behind the slewing center to add stabilizing moment. On mobile cranes they're usually stackable cast-iron or steel slabs, like the '10 t' plates in the footage. Tower cranes often use concrete blocks. Counterweight isn't free stability, though. With the boom raised steeply and no load, too much counterweight can tip a crane backward, so standards such as ISO 4305 require backward-stability checks. Outriggers widen the support base. A crane's safe capacity comes from the manufacturer's load chart for its exact counterweight, boom length, radius and outrigger setup, and capacity falls fast as the load moves farther out. - Department: Tech (also Science) - First published: 2026-01-01 - Last updated: 2026-01-01 - Permalink: https://detailenjoyer.com/case/counter-crane/ - Author: Marcus Easterling (DetailEnjoyer), The Detail Department ## Quick facts - **DD-687-F01**: A crane tips when the overturning moment exceeds the stabilizing moment. _(Write-up · Exhibit A (Moments, not just weight))_ - **DD-687-F02**: Too much counterweight can tip a crane backward when it's unloaded. _(Write-up · Exhibit C (Backward tipping))_ ## Write-up Balance is the real lift. Counterweights fight the tipping moment of every load. 1. **Moments, not just weight**: A crane tips when the overturning moment from the load (weight times radius), wind and slope exceeds the stabilizing moment from the crane and its counterweight. 2. **Counterweights**: Counterweights behind the slewing center add stabilizing moment. Mobile cranes use stackable metal slabs, often marked with their mass, like the 10 t plates in the footage. 3. **Backward tipping**: Too much counterweight is also a hazard. With a steep boom and no load, a crane can tip backward, and ISO 4305 requires checking backward stability with the crane unloaded. 4. **Outriggers**: Outriggers widen the base, which moves the tipping line out and greatly increases capacity. 5. **The load chart rules**: Safe lifting capacity comes from the manufacturer's load chart for the exact counterweight, boom, radius and outrigger setup, and it drops as the radius grows. ## Related case files - [Lingshan Lift (DD-707)](https://detailenjoyer.com/case/lingshan-lift/): Another machine built to lift - [Vertical Parking II (DD-009)](https://detailenjoyer.com/case/vertical-parking-ii/): Another mechanical lifting system - [Construction Covers (DD-631)](https://detailenjoyer.com/case/construction-covers/): Another case about construction-site safety - [Walking Floors (DD-665)](https://detailenjoyer.com/case/walking-floors/): Another case about moving heavy loads safely ## Reel vs. record - **Oversimplified**: counterweight doesn't simply 'shift the center of gravity back'. It adds stabilizing moment, and the crane's tipping line, set by its tracks or outriggers, is just as important. - **Missing hazard**: too much counterweight can tip a crane backward when the boom is steep and there's no load, so standards require backward-stability checks. - **Materials**: mobile cranes mostly use cast-iron or steel slabs, as in the footage. Concrete blocks are more typical on tower cranes. - **Missing**: outriggers widen the base and are central to stability. Most lifting capacity depends on how far they're extended. - **Missing limit**: capacity comes from the load chart and falls quickly with radius, so counterweights don't make any load 'safe'. ## Video: Counter Crane: Balance Is the Real Lift - Duration: 19.0 s · Published: 2026-01-01 - File: https://detailenjoyer.com/assets/videos/DS-2hC0kiuY.mp4 ### Transcript DID YOU KNOW? Cranes use counterweights to safely lift heavy loads by balancing the enormous forces involved. When a crane hoists something extremely heavy the load creates a tipping moment that would cause the machine to fall forward, so engineers add massive counterweights, often made of steel or concrete, on the opposite side of the boom to shift the center of gravity back towards the crane's base. NOW YOU KNOW! ## Questions & answers **Q: When does a crane tip over?** A: It's a balance of moments. _(Source: Write-up · Exhibit A (Moments, not just weight) · WorkSafe Queensland: Mobile crane code of practice 2024)_ **Q: What do the '10 t' slabs in the footage show?** A: Each counterweight slab's mass. _(Source: Write-up · Exhibit B (Counterweights) · WorkSafe Queensland: Mobile crane code of practice 2024; SANY Group: How to read a crane load chart)_ **Q: What hazard can too much counterweight cause?** A: Backward tipping when unloaded. _(Source: Write-up · Exhibit C (Backward tipping) · WorkSafe Queensland: Mobile crane code of practice 2024; ISO 4305:2014, Cranes: Stability: Mobile cranes (sample))_ **Q: What do outriggers do?** A: They widen the base. _(Source: Write-up · Exhibit D (Outriggers) · American Crane School: How to read a crane load chart; WorkSafe Queensland: Mobile crane code of practice 2024)_ **Q: What sets a crane's safe capacity?** A: The load chart for that exact setup. _(Source: Write-up · Exhibit E (The load chart rules) · American Crane School: How to read a crane load chart; SANY Group: How to read a crane load chart)_ ## Sources - [WorkSafe Queensland: Mobile crane code of practice 2024](https://www.worksafe.qld.gov.au/__data/assets/pdf_file/0018/130950/mobile-crane-code-of-practice-2024.pdf) - [ISO 4305:2014, Cranes: Stability: Mobile cranes (sample)](https://cdn.standards.iteh.ai/samples/57220/7626f8f3af2e413d8eab4eaf8b1ebf0f/ISO-4305-2014.pdf) - [American Crane School: How to read a crane load chart](https://americancraneschool.com/how-to-read-a-crane-load-chart/2021/instructional/) - [SANY Group: How to read a crane load chart](https://www.sanyglobal.com/blog/how-to-read-a-crane-load-chart/) ## Cite this case file Easterling, Marcus. "Counter Crane." The Detail Department (DetailEnjoyer), case file DD-687, last updated Jan 1, 2026. https://detailenjoyer.com/case/counter-crane/