Engineering logbook template

The template

# Engineering log entry

**Date:** YYYY-MM-DD
**Project:** Client · Project · Work package
**Engineer:** Name

## Work completed
- What you did today: analysis, testing, meetings, reviews.

## Design decisions
- **Decision:** One sentence a non-specialist could follow.

## Rationale
- The requirement, constraint, calculation or result that drove it.

## Alternatives considered
- Option: why it was rejected.

## Calculations / evidence
- Inline working, or the file name and revision of the calculation.

## Files / references
- Drawings, datasheets, standards, emails, with revision or date.

## Risks / unresolved issues
- Assumptions still to verify, and what happens if they are wrong.

## Next actions
- [ ] Action · owner · due date

How to fill in each section

Date, project, engineer

One entry per project per day. If you work on three jobs, write three short entries rather than one long one. That way each project's history reads properly on its own.

Work completed

Facts, briefly. "Ran modal analysis on bracket rev C" is enough. It is also the record behind your hours.

Design decisions

Only real decisions: choices someone could reasonably have made differently. One sentence each. See what counts as a design decision.

Rationale

The most important section. Name the requirement, constraint or result that drove the decision. If you can't fill this in, you may not have decided yet.

Alternatives considered

What else you looked at and the specific reason it lost. This stops the next engineer re-running your analysis.

Calculations / evidence

The working itself, or the file it lives in. A spreadsheet or calc file listed here counts as evidence. Name it precisely enough to find again: file name, revision, sheet.

Files / references

Drawings, standards, datasheets and correspondence, with revision letters or dates, because they change.

Risks / unresolved issues

Assumptions you haven't verified yet. Once they are written down, someone can check them.

Next actions

What, who, when. Tomorrow's entry starts by closing these.

Filled-in example: mechanical engineering

A drive-frame check after a client upgrades a conveyor gearmotor.

# Engineering log entry

**Date:** 2026-05-14
**Project:** Harbour Foods · Pallet conveyor upgrade · Drive frame
**Engineer:** A. Engineer

## Work completed
- Hand-checked drive frame cross-member for new 5.5 kW gearmotor (was 3 kW).
- Site visit: measured existing bolt pattern; photographed corroded base plate.

## Design decisions
- **Decision:** Replace the 50 × 50 × 3 SHS cross-member with 65 × 65 × 4 SHS.
- **Decision:** Keep the existing M16 8.8 hold-down bolts.

## Rationale
- Gearmotor reaction torque rises from 2.1 kN·m to 3.9 kN·m at the new rating.
- Conservatively taking the full reaction torque as bending in the cross-member:
  50 × 50 × 3 SHS φMs ≈ 3.2 kN·m → utilisation 1.22 (fails; was 0.66 at 3 kW).
  65 × 65 × 4 SHS φMs ≈ 7.1 kN·m → utilisation 0.55.
- Hold-down bolts at 3.9 kN·m: shear utilisation 0.41, no change needed.

## Alternatives considered
- Stiffen the existing 50 SHS with a welded plate. Rejected: clashes with the guard mounting, and site welding near food contact surfaces needs a permit window we don't have.
- Torque arm to the floor. Rejected: client does not want new floor fixings in the wash-down zone.

## Calculations / evidence
- Section capacities from the supplier's SHS tables, grade C350.
- Reaction torque from the gearmotor datasheet: 5.5 kW at 13.5 rpm output ≈ 3.9 kN·m.
- Site photos 2026-05-14 (IMG_2231 to IMG_2236).

## Files / references
- Gearmotor datasheet rev C.
- Drawing HF-CV-102 rev B (existing frame).

## Risks / unresolved issues
- Base plate corrosion: thickness not measured; assumed 10 mm nominal is still sound.
- Assumes the client confirms 5.5 kW is final (quoted alternative was 7.5 kW).

## Next actions
- [ ] Ultrasonic thickness check of base plate · workshop · 21 May
- [ ] Confirm motor rating in writing · client PM · 16 May
- [ ] Update HF-CV-102 to rev C · A. Engineer · 23 May

Values in this example are illustrative, not design data.

Using the template in FactaLog

FactaLog is engineering logbook software built around this same structure. Each entry is already dated and filed to a client and project, so the header fills itself in. Calculations can be written as live math blocks with units, images and links sit with the entry, and Ctrl+K searches every entry you have ever written. Paste the template into an entry and start writing. FactaLog is free for individuals.

Read next: How to record engineering design decisions properly.