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Quick answer: A 60-ton crawler crane undercarriage was revised from 210 mm to 175 mm chain pitch with nine rollers per side instead of seven, cutting peak outrigger reaction 24 percent and cyclic reaction 71 percent. Outrigger jack seal failures went from four across the fleet to zero.
A crawler crane's undercarriage is not asked to do the lifting. It is asked to keep the machine from tipping while the boom does the lifting, and to survive the transfer of a very large load from a moving hook to four outriggers. For a 60-ton machine, the second of those is where the design is most demanding.
This is how MAGEON worked with a crane manufacturer on an undercarriage revision for a 60-ton crawler crane whose outrigger reaction was causing failures in the outrigger jacks.
The customer's position
The manufacturer was experiencing a specific, well-defined failure: on lifts above roughly 40 tons, the outrigger jacks on the front of the machine were experiencing elevated seal pressures and, in a minority of cases, jack seal failure. The machine was not failing in service. The outriggers were failing, and the failure was forcing the crane to limit its capacity.
That last point is the commercially significant one. A crane that cannot safely reach its rated capacity at full outreach is a crane that customers rate lower, and the manufacturer was losing tenders on specification alone.
Understanding the load path
The first step was to establish where the outrigger reaction was coming from, because the intuitive explanation — the ground is soft, the machine sinks, the jacks take more load — was not the whole of it.
Instrumented testing on a customer's machine in a quarry confirmed the ground sinkage contribution, but also revealed a second, larger factor that the manufacturer had not identified: the track chain's longitudinal rigidity.
When the outriggers are loaded, the machine is supported at four corners. The upward reaction at the outriggers lifts the machine off the tracks at the front or rear, and the load is carried partly through the track chain's links in bending. A chain with a longer pitch and larger link section resists this bending more, and passes a greater share of the reaction directly to the outrigger without transmitting it into the jack's structure.
Instrumentation showed that approximately 30% of the outrigger reaction was being carried as a bending load in the track chain rather than directly to the ground. That bending load was cycling with every load hoist movement, and it was the cycle, not the static load, that was damaging the jack seals.
The revised specification
| Item | Original | Revised | Reason |
|---|---|---|---|
| Track chain pitch | 210 mm | 175 mm | Shorter pitch gives 20% more articulation points over the same chain length, distributing the bending load into more, smaller deflections |
| Track roller count | 7 per side | 9 per side | Closer roller spacing reduces the span each roller must bridge, lowering the chain's bending amplitude at the support points |
| Idler and roller diameter | Standard | +12% diameter | Larger diameter reduces contact stress on the chain's inner surface under the increased articulation rate |
| Track chain material | Standard alloy | Higher-strength alloy, same section | Allows the reduced chain section to carry the same load, which offsets some of the chain mass increase |
| Roller seal | Open | Sealed and factory-lubricated | The revised chain articulates more frequently, increasing the rate of lubricant consumption at the roller pivots |
Why the pitch change is the key move
Shortening the chain pitch is counterintuitive at first, because shorter pitch means more links for the same chain length, and therefore more weight. But the chain's resistance to out-of-plane bending scales with the number of articulation points, and the cyclic bending that was damaging the outriggers is what the change eliminates.
The engineering trade was: accept a small mass increase at the chain, offset it with a higher-strength alloy in a reduced section, and gain a substantial reduction in outrigger reaction cycling. The result was a net mass increase of approximately 90 kg on a 60-ton machine — 0.15% of the machine weight — for the removal of a failure mode that was capping the crane's usable capacity.
Results
Three cranes were built with the revised chassis and put into comparative testing against the original configuration, on the same machine, with load instrumentation on all four outriggers and all eight track rollers.
| Metric | Original | Revised | Change |
|---|---|---|---|
| Peak outrigger reaction, full 60 t lift at 18 m radius | Baseline | Down 24% | 24% reduction |
| Cyclic component of outrigger reaction | Baseline | Down 71% | The dominant failure driver, effectively removed |
| Outrigger jack seal failures in 18 months | 4 across the fleet | 0 | Eliminated |
| Machine mass increase | — | +90 kg | 0.15% |
| Track chain wear rate | Baseline | Up 9% | The cost of the shorter pitch, accepted |
The manufacturer restored the crane's full rated capacity at 18 m radius without restriction, and reported that the outrigger jack failures had ceased entirely across the test fleet. The 9% increase in chain wear rate was accepted as a reasonable exchange and is included in the published service schedule.
What this project illustrates
The single most useful thing the manufacturer took from the project was not the revised specification. It was the realisation that the outrigger failure and the undercarriage were the same problem, and that the undercarriage was the correct place to solve it.
This is the argument for treating a crawler undercarriage as an engineered system rather than a purchased assembly. A chain pitch change in a catalogue chassis is not available. A pitch change in a custom crawler undercarriage is an ordinary engineering decision, and it is the only route to a 71% reduction in a failure driver.
Programme status
The revised chassis is in production for the manufacturer's 60-ton model and is being developed for the 80-ton variant, where the outrigger reaction and the chain bending problem are proportionally more severe.
MAGEON product lines and how they map to this topic
The engineering principles in this article apply across the full MAGEON product range. Each custom undercarriage order starts from one of four chassis families, and the selection logic above determines which one fits your machine.
| MAGEON product line | Typical tonnage | Best suited to |
|---|---|---|
| Customized steel track chassis | 3-60 T | Quarry, mining, crushing, demolition, heavy lifting and drilling rigs, where abrasive rock and impact loading drive the wear pattern |
| Customized rubber track chassis | 0.5-30 T | Urban construction, utility trenching, landscaping, agriculture and any finished-surface work where noise, surface protection and low ground pressure matter |
| Customized steel track undercarriage | 5-120 T | Continuous-duty mining and screening plant, large crawler cranes and heavy equipment carriers running extended shifts in abrasive conditions |
| Customized rubber track undercarriage | 1-20 T | Compact and mini excavators, tracked dumpers, harvesters and municipal plant, where a custom undercarriage is specified to meet ground pressure and noise requirements on the same machine |
Whether you are specifying a custom undercarriage from first principles, comparing a customized steel track chassis against a customized rubber track chassis, or reviewing the service life of a customized steel track undercarriage in abrasive service, MAGEON can size, engineer and support the build. Every crawler undercarriage project begins with your machine's weight distribution, working conditions and interface drawing, and the quotation is backed by a written calculation. Contact our engineering team with your host model, working conditions and mounting interface, and we will respond with a configuration recommendation within one working day.