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CookbookLabs and workshopsNo. 27

A mechanical engineering design notebookevery calculation worked, every choice recorded

Recipe No. 27 · Labs and workshops

For: A mechanical engineering student on a capstone design

You get: A document per design problem, calculations worked, choices recorded

Time: An evening to set up, then weekly

See it in know.sh

A design problem as a document. Try the caliper: press the pedal and read the clamp force, then check it against the hand calculation below.

Capstone — brakes for a city carNo. 4

Front brakespedal to tyre, worked by hand

6 sections, 1,870 words, about 8 minutes, revised 24 September

Design problem 4: size the front calipers so a 1,400 kg car can stop at 1 g with under 200 N on the pedal. Every figure is worked by hand in section 3; the caliper below is there to check them.

At 100 N, booster on, the hand working gives 31.6 bar, 7.23 kN of clamp and 752 N·m a wheel; the caliper reads 32 bar, 7.2 kN and 752 N·m. Press to 180 N and the wheels lock: 177 N was the answer.

Sections

  1. 1The requirementObservationA 1 g stop with under 200 N at the pedal, booster working.
  2. 2AssumptionsEvidence4:1 pedal, 3:1 booster, 22 mm master cylinder, μ = 0.4, 130 mm effective radius, 0.31 m tyre.
  3. 3The hydraulic lever, by handInsight, keyPedal to pad in six steps: 100 N at the foot becomes 7.23 kN on each pad.
  4. 4Choosing the caliperDecisionOne 54 mm floating piston: 177 N for 1 g, inside the limit.

and 2 more sections

The calculation as a steps element: each stage its formula, numbers and units, then the requirement worked backwards to a pedal force.

Capstone — brakes for a city carFront brakes

3of 6

The hydraulic lever, by hand

Insight, key section, 1 note, 486 words

One stop, followed from the driver’s foot to the tyre: 100 N at the pedal, booster on, a floating caliper with one 54 mm piston.

Turned round. A 1 g stop needs 1,400 × 9.81 × 0.31 / 3.2 = 1,330 N·m at each front wheel. Worked back up the chain, that is 177 N at the pedal: inside the 200 N limit, with 23 N to spare.

The options as a table with the pick marked, and a decisions register that keeps the first choice the calculation overturned.

Capstone — brakes for a city carFront brakes

4of 6

Choosing the caliper

Decision, 2 sources, 358 words

Three calipers that fit inside a 15-inch wheel, each worked through section 3 for the pedal force a 1 g stop needs.

How it works

Your capstone notebook, done properly: a document for each design problem, every calculation worked step by step with its units, the options side by side with the pick marked, and a working brake caliper to squeeze, so the hydraulic lever you worked by hand moves on the page.

  1. A document per design problem

    Give your assistant the project brief and your lecture notes. Ask for a document per design problem, with sections for the requirement, the assumptions, each calculation, the options and the decision.

  2. Work it by hand, then set it out

    Work each calculation yourself first. Then ask for it as a steps element, one stage per step with the formula, the numbers and the units, and check it line by line against yours.

  3. Put the mechanism beside the numbers

    Ask for a widget element that models the part, such as a caliper with a pedal to press. View source shows its code; its figures should agree with your hand working.

  4. Record every choice, and why

    Ask for the options as a table element with the pick marked, and a decisions element that keeps every choice, including the ones you later replaced.

Try this prompt

Your assistant, connected to know.sh (Claude, ChatGPT or a local model):

Using know.sh, add a section to Front brakes called The hydraulic lever, by hand, holding a steps element: one step per stage from pedal to deceleration, for 100 N at the pedal, a 4:1 pedal, a 3:1 booster, a 22 mm master cylinder, a 54 mm piston, μ = 0.4, a 130 mm effective radius, a 0.31 m tyre and a 1,400 kg car. Show every formula with its units.

Your assistant, connected to know.sh (Claude, ChatGPT or a local model):

Using know.sh, read Front brakes and add to Choosing the caliper a table element of the three calipers with the pick marked, and a decisions element: one decision per choice so far, the reason in figures, the options rejected, and the 48 mm caliper marked as superseded.

Made with

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See also