Catalogue study & calculation method
CAT Performance Handbook Edition 50: vibratory rollers, printed 10-18–10-19 (PDF 151–152); dozing, 16-9 and 16-18 (PDF 228 and 237); soil compactors, 19-8–19-9 (PDF 293–294).
Open the local CAT handbook ↗ · Read the study notes ↗
Spreading capacity = loose lot-layer volume ÷ total strip-cycle time. Strip volume = strip width × run length × loose layer thickness; cycles per strip are rounded up from strip volume ÷ effective blade load. Every cycle includes push, return and fixed time. Thin or narrow strips may use partial blade loads. This assumes separate blade-load cycles across each strip, and should be calibrated against actual placement operation. Loose output converts to compacted output using loose density ÷ compacted density. CAT’s dozing curves concern carrying and dumping blade loads; this calculator uses an editable cycle estimate for placement, not a transcription of those curves.
Rolling capacity uses whole lanes, layer volume, speed, passes and turning time. CAT’s underlying compaction formula is working width × speed × compacted thickness ÷ passes. An 815/825 performing two duties has combined capacity = the lower of spreading capacity and primary-compaction capacity. Roller work is then a separate stage.
Daily output allows for material supply, spreading, compaction and testing holds. Each lot layer is width × length × compacted thickness. Spreading and rolling use staged work fronts within a layer; the entire placement fleet stops for the entered compaction testing time before the next layer starts. The first layer has no initial hold. A final layer does not need an extra test hold to count its placed tonnes. If the shift ends while waiting for the next layer, no further tonnes are produced. No spreading or compaction occurs during testing holds. All machine hire costs continue. Testing holds are clock hours, separate from rest and work efficiency.
Available supply is tonnes for the full shift and is not reduced again by crew efficiency. Available material is assumed equal to the daily placement target. The three bottlenecks are material supply, spreading and compaction; compaction includes testing. A supply tie is labelled material supply. Otherwise rolling and testing are compared with the placement duty time, and primary compaction plus testing is compared with spreading for a shared-duty 815/825.
The model excludes delivery timing within the shift, watering, retesting and failed-test rework, trimming rework and interference between work fronts unless allowed for in efficiency. Layers/day are equivalent layers over the entered lot; the lot area is reused for successive lifts. Output includes a partially placed/compacted layer; it does not mean all reported tonnes have received a passing test result.
Costs use a full billed shift and all crew machines. Capacity cost per tonne = shift cost ÷ potential daily tonnes. Cost per target tonne = shift cost ÷ daily target, shown for crews that meet it. Blank or zero rates are unpriced. Rates should include fuel and operators; other site costs are excluded.
Pass counts and thickness must achieve the specified density in a site trial. The calculator estimates production for those inputs; it does not predict density or certify compaction. Roller size labels are rounded classes, and padfoot configurations require confirmation of actual width and fitted machine.
