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Counter Crane

Short answer: 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.

VideoWrite-up4 sources

In collections:Everyday Physics

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What should you know about Counter Crane?

Quick facts. Each one stands alone and has a stable ID you can cite.

  1. A crane tips when the overturning moment exceeds the stabilizing moment.

    DD-687-F01 · Write-up · Exhibit A (Moments, not just weight)

  2. Too much counterweight can tip a crane backward when it's unloaded.

    DD-687-F02 · Write-up · Exhibit C (Backward tipping)

Video transcript: Counter Crane: Balance Is the Real Lift

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!

Burned-in captions, read frame by frame (see transcript.md) · 19.0s Reel ·

Video coming soonCounter Crane · Instagram Reel
Counter Crane: Balance Is the Real Lift Instagram Reel · · 19.0s

The write-up

Balance is the real lift. Counterweights fight the tipping moment of every load.

  1. Exhibit A

    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. Exhibit B

    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. Exhibit C

    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. Exhibit D

    Outriggers

    Outriggers widen the base, which moves the tipping line out and greatly increases capacity.

  5. Exhibit E

    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.

Questions people ask about Counter Crane

When does a crane tip over?

It's a balance of moments.

Source: Write-up · Exhibit A (Moments, not just weight) · WorkSafe Queensland: Mobile crane code of practice 2024

What do the '10 t' slabs in the footage show?

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

What hazard can too much counterweight cause?

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)

What do outriggers do?

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

What sets a crane's safe capacity?

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

Test Your Knowledge

All quizzes →

5 questions, all from this case file. Answers are revealed instantly.

  1. When does a crane tip over?

    1. When overturning moment exceeds stabilizing moment
    2. When the load is over 10 t
    3. When the boom is vertical
    4. When the engine stalls
    Show the answer

    Answer: A. When overturning moment exceeds stabilizing moment It's a balance of moments. Source: Write-up · Exhibit A (Moments, not just weight) · WorkSafe Queensland: Mobile crane code of practice 2024

  2. What do the '10 t' slabs in the footage show?

    1. Counterweight mass
    2. Boom length
    3. Fuel capacity
    4. Hook speed
    Show the answer

    Answer: A. Counterweight mass 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

  3. What hazard can too much counterweight cause?

    1. Tipping backward
    2. Faster lifting
    3. Boom overheating
    4. Lower fuel use
    Show the answer

    Answer: A. Tipping backward 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)

  4. What do outriggers do?

    1. Widen the support base
    2. Add engine power
    3. Lengthen the boom
    4. Cool the hydraulics
    Show the answer

    Answer: A. Widen the support base 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

  5. What sets a crane's safe capacity?

    1. The manufacturer's load chart
    2. The operator's estimate
    3. The boom's color
    4. The weather forecast
    Show the answer

    Answer: A. The manufacturer's load chart 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

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/

Permalink: https://detailenjoyer.com/case/counter-crane/ · Last updated

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