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Quick answer: Thirty 20-ton excavators received new crawler undercarriages during one 12-day quarry shutdown, completed in 11 days. A pre-shutdown inspection of every machine found 11 machines needing full chassis rather than running gear, which is what made the schedule achievable. Track wear life improved 41 percent.
Planning a multi-machine undercarriage replacement is a scheduling problem before it is a mechanical one. The mechanical work is well understood. The scheduling work — getting 30 machines through a 12-day window without losing production, without a spare machine, and without a supplier who cannot deliver 30 chassis on time — is where most projects of this type fail.
This is how a limestone producer in northern France planned and executed the replacement of the undercarriages on its entire 20-ton excavator fleet during a single scheduled shutdown.
The situation
The operation ran 30 20-ton excavators on a hard limestone quarry face with a high steel-to-ore ratio. The site had been operating its original chassis since the fleet was commissioned, and the site manager described the situation plainly: the machines were on their third set of track chains, the third rebuild had been deferred twice, and the next failure would not be scheduled.
Three constraints shaped everything:
- A hard date. The site had a scheduled 12-day shutdown for a crusher reline. No extension was possible, because the downstream plant had its own committed shipping schedule.
- No spare capacity. There was no standby excavator. A machine out of service was production out of service.
- A single failure would end the plan. If one chassis was not delivered on time, the entire sequence stalled, because the removal crew could not be redeployed usefully to another machine.
The approach: sequence first, then specify
We worked backwards from the shutdown date, which is the only way to plan this kind of work.
Phase 1 — Establish the true scope
The initial request was for track chains and rollers. A physical inspection of all 30 machines, completed in the two weeks before the shutdown, found something different: 11 machines required the full chassis assembly, not just the running gear. Frame corrosion at the tensioner mount, which the site had been treating as a cosmetic issue, had progressed to the point where the mount required structural repair on four of them.
Had this been found on day three of the shutdown, the plan would have been dead. The inspection cost two weeks and essentially saved the project.
Phase 2 — Sequence the work around the site's real constraint
The 12 days were not 12 days of available working time. The crusher reline consumed 4 of them, and the site could only run 6 excavators simultaneously without overloading the haul fleet.
The sequence was built as three crews of four machines, running in parallel, with a deliberate overlap of one day between crews so that a delay in one crew did not propagate. Each crew was equipped with a complete set of tooling and a hydraulic track tensioner, and each had a nominated mechanic with previous experience on that machine model.
Phase 3 — Specify the replacement chassis
Eleven complete chassis and 19 running gear kits were specified. Three changes were made against the original specification, all driven by the site data rather than by preference:
| Change | Reason | Effect |
|---|---|---|
| Hardened shoe material, one grade higher | Site analysis showed quartz content in the feed at levels consistent with a 3,500-hour track life on the original grade | Expected life extended to 6,000–7,000 hours |
| Sealed and pre-lubricated track chain bushings | Two machines had bushing failures in the prior period despite the standard grease-fitting maintenance regime | Removed the lubrication task entirely |
| Corrosion-resistant pin and bushing alloy | Water ingress at the quarry floor during the winter drainage cycle | Addressed the observed early-season failures |
Results
The shutdown was completed in 11 days, one day inside the window, with no production loss beyond the scheduled crusher reline.
- All 30 machines returned to production. No machine was left incomplete at the end of the window.
- Zero safety incidents across 90 chassis removals and installations, with the site safety manager noting that the pre-planned sequence and the single dedicated crew structure were the reason.
- Track wear life improved by 41% on the revised specification, verified over the following 12 months against the site's own wear logs.
- Unplanned undercarriage downtime fell 63% over the same period.
The part that surprised the site manager
What the site manager did not expect was the effect on the operating team's routine. Under the previous regime, the maintenance schedule included a weekly tension check and a monthly chain inspection on every machine, performed by the site's own mechanics during shift handover. With sealed and pre-lubricated chain, both tasks disappeared from the schedule.
The site converted that time into a planned condition-monitoring routine — tension measured against a log rather than a feel, roller free-rotation checks, and oil analysis on the drive units — which is a better use of the same hours and is what allows the fleet to predict the next replacement rather than react to it.
The commercial structure that made it work
Three elements of the supply arrangement were as important as the engineering:
- Delivery in tranches tied to the work sequence, not one shipment. Chassis for crew one arrived five days before crew one started. This avoided the working capital of holding 30 chassis on site and spread the delivery risk.
- A written commitment on the non-standard components. Two of the changes required a modified pin and bushing alloy, and the lead time for those was committed in writing at 20 working days from drawing approval. That commitment was what made the shutdown date defensible in the customer's own planning.
- On-site technical support for the full window. MAGEON's engineers were on site for the duration of the shutdown, not on call. With 90 chassis removals in 11 days, the difference between on-call and on-site is the difference between a plan and a scramble.
Why we are publishing this project
Because the most useful part of it is not the engineering. Almost every chassis in this project was dimensionally standard. What made it work was the sequence, the inspection before the shutdown, and the delivery structure.
If you are planning a multi-machine undercarriage programme, the three things worth copying are these: inspect every machine before the window, not during it; sequence the work around your real crew capacity rather than the calendar; and tie deliveries to the work sequence rather than to a single shipment date.
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.