BRIEFING / WEEK 04
Understand the Mechanism
Distinguish mechanism faults using selected inspections, predict motion and verify a targeted repair.
Read, then try it
This briefing explains the week's idea and shows a worked example. Read the objectives and example, then open the lab for the actual controls, three practice configurations and saved fieldwork record.
The week’s question: A carriage does not behave as required. Identify the failed dependency, choose a test that distinguishes it from an alternative and verify the repaired motion.
Forcing the handle would make something happen. Understanding the mechanism lets you choose what happens.
What you will learn
- Predict gear direction and movement from the published relation.
- Use inspections to distinguish causes before changing apparatus.
- Verify a targeted repair against the whole required motion and changed target.
The briefing
Start with the causal chain
The crank turns a driver, which turns an externally meshing follower in the opposite direction. Follower turns equal driver teeth divided by follower teeth, multiplied by input turns. Write the expected direction and amount before operating.
The gear pair is one dependency. The interlock must allow motion, the cam must meet the required condition and the return spring must be attached. A wrong ratio can produce the wrong movement; a blocked input and missing return connection can prevent the intended cycle for different reasons.
Select a discriminating inspection
List two candidate faults. Predict what an interlock inspection, cam reading, spring inspection or gear inspection would show under each. Choose a test that separates candidates before changing apparatus. Repairing every part removes information about which fault explained the symptom.
The phases use one initial fault each. Discover it from evidence rather than a phase-to-answer list. Once diagnosed, configure any changed target independently: a new output requirement is a design condition, not necessarily another failure.
Verify the required behaviour
After the repair, test predicted turns, direction and the return condition. “It moves” is weaker than “it produces the required movement.” Record an unrelated condition you deliberately retained. This explains why the repair was bounded rather than a lucky set of adjustments. The apparatus is an original educational mechanism; no commercial lock or bypass procedure is involved.
Worked example · a different scenario
The separate conservatory lift has an 18-tooth driver and needs three output turns from five input turns. A 30-tooth follower satisfies 18 ÷ 30 × 5 = 3, in the opposite direction. The correct ratio still cannot move a blocked mechanism: the demonstrator releases the interlock, sets the cam to 270 degrees and attaches the spring before testing. A later requirement of two output turns from four input turns needs a 36-tooth follower. The valid readiness conditions remain, while the ratio is recalculated. Before blaming the gear ratio for a stall, the demonstrator inspects the interlock. That inspection distinguishes a blocked mechanism from an incorrect movement ratio; the recorded test precedes the adjustment.
Watch this separate example and inspect its finished record.
A plausible mistake
Swapping parts until movement appears may reach a working state without explaining the fault. It also destroys the evidence of what mattered. Change one variable, state a prediction and preserve the before/after observations.
Supplied rule sheet
ME-01 gives the mechanism rules and inspection options. ME-02 gives the target and initial inspection cards for each phase.
- A 12-tooth driver externally meshes with a selectable 12-, 24- or 36-tooth follower. Output turns = 12 ÷ follower teeth × input turns; direction is opposite.
- Motion requires a released interlock, attached return spring and specified cam angle. An engaged interlock blocks cam adjustment.
- Practice: four input turns must produce two outputs; cam datum 180 degrees.
- Skill check: four input turns must produce four outputs; datum 180 degrees.
- Transfer: six input turns must produce two outputs; datum 90 degrees.
- Choose inspections of brake/interlock, return spring, cam datum or gear teeth. Record evidence and a diagnosis before using adjustment controls.
- One initial fault exists in each phase. Its identity is not supplied in the task; compare the revealed conditions with the rules.
- After a targeted correction, verify movement, direction and the required return. This is an educational mechanism, not a commercial lock.
Before the lab
Read the labelled ME-01 parts and trace its input-to-output chain (15 minutes). Predict the output after two input turns (5 minutes).
What happens next
A1 combines mechanism diagnosis with observation and spatial modelling. Physical recovery and stabilisation can need a support mechanism; digital recovery need not repeat an unrelated cradle exercise.
Keep mechanism-diagnosis from this week’s lab. Download the campus pack.
SLOP UNIVERSITY · THE ACADEMY OF IMPOSSIBLE SKILLS
An original fictional course. Progress records practice, not academic certification.