Engineering & Robotics · Project 5 of 12

The Thing That Keeps Breaking

What the thing that keeps breaking really costs

Count what one latch, strap or bracket costs your household a year in rupees and lost hours.

The calendar this needs: Two fourteen-day tally periods that cannot be shortened or overlapped — fourteen days of logging before the change and fourteen days after — plus a hundred-use test day at each end, so the baseline fortnight has to start in the first week of the project.

Six weeksNo equipment on the paper route 20 written stepsMarked out of 20Free forever
The question

Which small object in your house, shop or classroom fails most often, what does each failure cost in rupees and minutes, and does one reinforcement stop it failing?

Every factory, fleet, hospital and building runs on somebody counting how often a part fails and what each failure costs, and that counting has a name in industry: reliability and maintenance engineering. Manufacturers pay for failure data because a warranty claim, a stopped line or a callout costs many times what the part cost. The method here is the industry method at household scale: define one use, count the failures, find where the load concentrates, change one thing, and count again under identical conditions.

Two acts. Find, then fix.

Every EAD project runs the same shape. The first act produces a number nobody in the room could previously state. The second act changes exactly one thing and proves whether that number moved.

Act 1 · Find
You find the object that actually fails most — a gate latch, a bag strap, a shelf bracket, a tap washer, a door handle, a drawer runner, a broom head, a chair joint — and you build the case from evidence rather than memory: three people asked how often it fails, the physical repair scars photographed and counted, and the failure produced on purpose in a controlled test you can repeat. Then you cost it: what a repair costs, what a replacement costs, how many minutes each failure eats, and how often it happens, which together give rupees and hours per year.

A one-page costed problem statement carrying five lines: whose problem this is, failures per hundred uses in the controlled test, failures per fortnight in ordinary use, rupees per year and hours per year. Beside it sit a photograph of the failure point, an annotated drawing showing where the load concentrates, and the arithmetic behind every rupee figure with its source.

Act 2 · Fix
You change one thing about the object using only what is already in the house or the shop — a second fixing, a packing plate under a bracket, a stop that limits travel, a doubled strap, a washer at the wear point — and you fit it. Then you run the identical hundred-use test and log the identical fortnight of ordinary use, with the same tester, the same load and the same definition of one use.

Two charts of two bars each, because a rate per use and a rate per unit of time share no scale and must never sit on one axis: one chart of failures per hundred uses before and after, one chart of failures per fortnight before and after, each with its own stated unit. Beside them, the new rupees and hours per year, a named list of confounders, and a photograph of the fitted change taken from the same standing position as the before photograph.

What actually gets measured

The numberfailures of one object per hundred identical uses, and failures per fortnight in ordinary use, in failures per 100 uses
BeforeTwo counts taken before anything is changed: failures in a controlled test of one hundred identical uses, tallied by hand and filmed, with the load and the definition of one use written down first; and failures logged on a tally card in ordinary use across fourteen days, each with the date, the user, the minutes lost and the rupees spent.
AfterThe identical hundred-use test on the changed object, run by the same person in the same place with the same load and the same speed, plus fourteen more days of ordinary-use logging on a fresh tally card in the same place, using the same definition of a failure.
The honest partA well-measured failure scores higher than an unmeasured success. If the number did not move, say so and explain why.

If your household cannot run this

Run the whole method on school property with a member of staff. A classroom door handle, a cupboard latch, a desk joint, a gate bolt or a store-room shelf bracket fails often enough to count, and the staff member holds the keys, the tally card and the test load. This is for the learner with no co-operative household, no object they are allowed to alter, no safe place to run a hundred uses, and no street they can be sent along. It is the same twenty steps, the same two fortnights and the same twenty marks. It is not a reduced version and it is not marked as one.

Every step, written out

Twenty steps in total — ten to find the number, ten to fix it. Pick the route that matches what your school actually has.

A tape measure, a tally card and squared paper produce the same failure rate; the counting is done by hand, the drawing is done with a ruler, and the witnesses sign what they saw.
You need: A notebook ruled into columns with a pen and a ruler: object, times per month, minutes lost, rupees, tally · A tape measure or a ruler for the dimensions at the failure point, and a card taped beside the object for the fourteen-day tally · A known test load already in the house — a one-litre bottle of water weighs one kilogram, a sealed bag of rice is marked with its weight · Squared paper for the load-path drawing, the redesign drawn to a stated scale, and the two before-and-after charts of two bars each, drawn on separate axes · Repair material already in the house: string, wire, a spare screw, a washer, an offcut of wood, glue, tape, a strip of old rubber · The household's receipts, or a card carrying prices copied at the hardware shop counter on a trip a named adult makes with you

  1. Find the thing

    45 minutes
    Walk your house, shop or classroom and list every object that has failed more than once, then choose one.
    • Walk one lap of each room with the notebook open and write down every object that has been repaired, tied, taped, glued, wired or propped.
    • Ask three people who use these things daily how often each one fails, and write their answers as times per month, never as the word 'often'.
    • Sketch each candidate on its own line, marking the joint or the point that gives.
    • Rule three columns beside the list: times per month, minutes lost per failure, and safe to test yes or no, against electrical, gas, structural or above your reach.
    • Choose the highest-scoring object that passes the safety column and write one sentence saying why you chose it over the runner-up.
    Write down: The ruled candidate table with three people's frequency answers, the safety column, the chosen object and the written reason.
    Finished when: One object is named, sketched and defended in writing against at least four rejected candidates.
    Commonest mistake: Choosing the object that annoys you most rather than the one that fails most. Let the table decide; if the annoying one wins on numbers, keep it, but it has to win.

  2. Read the scars

    40 minutes
    Collect physical evidence that this object has failed before, instead of trusting anybody's memory.
    • Draw the object large on one page and mark every repair on the drawing: old glue, a second screw hole, wire, tape, a replaced part, a worn groove.
    • Count the separate repair marks and write the count down, because each mark is a past failure somebody already paid for.
    • Ask the three users when each repair happened and write the nearest month against each mark on the drawing.
    • Ask whoever fixed it last what they used and what it cost, and note whether the receipt or leftover material still exists.
    • Measure the object with a tape and write the dimensions on the drawing: thickness at the failure point, length of the arm, diameter of the fixing.
    Write down: The annotated drawing with dimensions in millimetres, and a dated repair history with one line per mark.
    Finished when: Your count of past failures comes from marks you drew and people you asked, not from one person's recollection.
    Commonest mistake: Accepting 'it breaks all the time' as data. Convert every statement into a count and a month, and write down who said it.

  3. Count it failing

    60 minutes for the test, plus 10 minutes a day for 14 days of tallying
    Produce the failure on purpose in a controlled test, and start a fourteen-day log of failures in ordinary use.
    • Write down the definition of one use — one full open and close, one lift with the bag loaded to its usual weight, one turn of the handle — and keep that definition for the rest of the project.
    • Run one hundred of those identical uses at a steady, ordinary speed with the same load, and have a second person mark a tally every time it slips, jams, loosens, tears or comes apart.
    • Use a known load you can hold in one hand, such as filled bottles counted as one kilogram each, placed so it can only fall onto bare floor, with feet and hands clear and your face turned away.
    • Draw the exact point that gives, large, immediately after the test, and have your counter sign and date the tally sheet.
    • Count how many failures those hundred uses actually produced, because a rate out of a hundred moves in steps of one whole failure and two or three failures cannot be told apart from chance; if the before-count is under about five failures, either extend the test to two or three hundred uses at the same speed and load until at least five are counted, or report the plain count instead of the rate and write on the page why you did.
    • Tape a tally card beside the object and begin a fourteen-day count of failures in ordinary use, one line per failure with date, time and who was using it.
    Write down: The written definition of one use, the load in kilograms, the failures-per-hundred-uses figure, and the signed tally sheet.
    Finished when: A failures-per-hundred-uses number exists, the fourteen-day log has begun, and a stranger could repeat your test from your written definition alone.
    Commonest mistake: Cycling it faster and harder than real use to force a failure. A test that does not look like ordinary use tells you nothing about ordinary use, so match the speed and the load and write both down.

  4. Cost one failure

    50 minutes
    Work out what a single failure costs and turn it into rupees and hours per year.
    • Go to the hardware shop with a named adult who walks there with you and stays within sight the whole time, and copy the price of the material, the part and the tradesman's callout charge onto a card with the shop name.
    • On the same trip, with the same adult beside you, ask at two shops what a full replacement of the object costs and write both prices down.
    • Sit with the people involved and time the last failure end to end: minutes to notice, to find tools, to fix, to walk to the shop, and the minutes the thing was unusable.
    • Do the arithmetic longhand in the margin: failures per year times rupees per failure, and failures per year times minutes per failure divided by sixty. A failures-per-year figure projected from a fourteen-day tally assumes that fortnight was typical of the whole year, and it may not be — the object gets used harder in one season than another, in wet weather, in term time, or in a month when the house is full — so write that assumption and one named reason it might fail directly beside the figure.
    • Where you convert between periods, use 4.33 as the number of weeks in a month: your fortnight is two weeks, so multiply a fortnight count by 2.165 for a month and by 26 for a year, and use twelve months for the users' times-per-month answers.
    • Repeat the arithmetic twice, once with the users' failure rate and once with the rate your own tally implies, and leave both on the page.
    Write down: Rupees per failure, minutes per failure, failures per year from two sources, and rupees and hours per year with the longhand working left visible.
    Finished when: Two independent rupees-per-year figures sit on the page and you can say which is the more conservative and why.
    Commonest mistake: Counting only the part you bought. The trip to the shop, the waiting and the thing being unusable are usually larger than the part, so count the minutes.

  5. Find the weak point

    50 minutes
    Work out where the load concentrates and why the same point gives every time.
    • Draw the object large on squared paper and draw arrows along the path the force takes, from where the hand or the weight pushes to where the object is held.
    • Mark three places on the drawing: the narrowest section, the sharpest corner, and the single fixing carrying most of the load, because failures start at those three.
    • Write plainly whether the material gave or the joint gave, since a fixing working loose is a different problem from a bar bending.
    • Compare with the repair marks from step two and write yes or no against the question: did it fail at the same place every time.
    • Put the one question you cannot answer yourself into the five your teacher sends to the professional, and write their answer down word for word when it comes back.
    Write down: The arrowed load-path drawing, one paragraph naming the weak point in plain language, and the expert's answer as spoken.
    Finished when: You can point at one place on the object and explain, in a sentence a stranger follows, why the load ends up there.
    Commonest mistake: Blaming the material because that is easier to say. Most household failures are a fixing loosening, a sharp corner concentrating load, or a part hammering against a stop, so look at the joint before the metal.

  6. Name the cost

    50 minutes
    Finish the costed problem statement on one page and choose the single change you will make.
    • Write five lines: whose problem this is, failures per hundred uses, failures per fortnight, rupees per year, hours per year.
    • Draw a bar chart on squared paper to a stated scale, rupees per year for your object beside the two runners-up from step one, with the finding as the title.
    • List three possible fixes using only what is already in the house or the shop: a second fixing, a packing plate, a stop that limits travel, a doubled strap, a washer at the wear point.
    • Choose one and write: 'I will change X to Y and expect failures per hundred uses to fall from A to B and failures per fortnight from C to D.'
    • Read the page aloud to whoever owns the object and have them sign and date it if they agree to the change.
    Write down: The one-page costed problem statement, the three candidate fixes with the failure each would prevent, and the chosen fix as one testable sentence.
    Finished when: Somebody who was not there reads the page once and repeats your rupees-per-year figure back correctly.
    Commonest mistake: Choosing a fix that needs something bought. Nothing bought is the rule, so cost the shop fix honestly on paper and reinforce with what is already there, or you will have nothing to measure.

  7. Draw and fit it

    60 minutes
    Draw the change to real dimensions, fit it, and write the protocol that keeps the after-test identical to the before-test.
    • Draw the reinforcement on squared paper to a stated scale, using the dimensions measured in step two, with the new fixing or plate shown in position.
    • Write what stays fixed: same definition of one use, same load, same tester, same counter, same place, same speed, same hundred-count.
    • Fit the change with what is already in the house; if a hand tool is needed, an adult holds the work, and nothing is cut, drilled or heated by you alone.
    • Draw or photograph the object before fitting and after fitting from the same position, with the same item beside it for scale.
    • Write your prediction on the page, date it, and have one person witness it with their signature before any after-data exists.
    Write down: The scaled drawing, the fixed protocol as a numbered list, the two matched pictures and the witnessed, dated prediction.
    Finished when: The change is fitted, the protocol is written down, and a signed prediction predates the first after-test.
    Commonest mistake: Improving three things at once because you already have the tools out. One change only, or you can never say which one worked.

  8. Test it again

    60 minutes
    Run the identical hundred-use test on the changed object and count failures exactly as before.
    • Read the protocol aloud before starting and check the load, the speed, the tester and the definition of one use line by line.
    • Have the same counter mark the tally, and have them sign and date the sheet at the end.
    • Record separately anything new that started going wrong because of the change, in its own column.
    • Inspect the change afterwards and draw it: has it loosened, bent, worn or shifted position.
    • Write down what went wrong on the day: a distracted count, a load that slipped, a helper who joined in halfway.
    Write down: Failures per hundred uses after the change on a signed tally sheet, the inspection drawing, and a dated failure-log entry naming every deviation.
    Finished when: The after-test used the same load, speed and use-definition as the before-test, and the failure log holds at least one honest entry.
    Commonest mistake: Testing gently because you want the fix to work. Count out loud and let the witness watch the last twenty uses.

  9. Fourteen days again

    10 minutes a day for 14 days, plus 45 minutes for the two charts and the arithmetic
    Log failures in ordinary use for fourteen more days and compare like with like.
    • Tape a fresh tally card in the same place and log every failure with date, time, user and minutes lost, exactly as in the baseline fortnight.
    • Check the object once a week for the change working loose, and write down what you find each time.
    • Draw two separate charts on squared paper, two bars each, never four bars on one axis, because failures per hundred uses and failures per fortnight are different units and share no scale: one chart to its own stated scale for failures per hundred uses before and after, one chart to its own stated scale for failures per fortnight before and after, each labelled with its unit.
    • List every confounder you can name: colder or wetter weather, a lighter user, the object being used less because everybody knows it is being watched, a second repair somebody made without telling you.
    • Redo the rupees and hours arithmetic longhand with the new failure rate and state whether the fix saved more than the time it took to make; the new per-year figure is again a fourteen-day tally stretched over a year, so repeat beside it that this assumes the fortnight was typical and name the season, the weather or the change in who is at home that could make it untypical.
    • Check the after-count as you checked the before-count: if either fortnight or either hundred-use test produced under about five failures, report the counts themselves rather than the rates, and say plainly that a difference that small cannot be told from chance.
    Write down: The two charts of two bars each, on their own axes and units, the new rupees and hours per year, the confounder list and the weekly inspection notes.
    Finished when: You can state the before figures, the after figures, and at least two reasons the difference might not be your doing.
    Commonest mistake: Reporting the hundred-use test and quietly dropping the fortnight log because it disagreed. Report both, and where they disagree, say so, because that disagreement is itself the finding.

  10. Share and reflect

    60 minutes
    Publish the finding, defend it to real people, and record whether the change stays on the object.
    • Stand the defence live: ten to twelve minutes of unseen questions put to you by two witnesses who sign and date the page, covering the object, the failure point, the definition of one use, both before-counts, the change fitted, both after-counts and the limits you accept without argument. On this route nothing is recorded.
    • Read the one-page explainer to three people who use the object and write down what each of them said.
    • Ask your teacher to send the two charts and the drawing from the school address to the professional they contacted, with one question: what would you have reinforced that I did not.
    • Ask the owner of the object, in front of a witness, whether the change stays and why, and write the answer word for word.
    • Complete the relations ledger with ten codes, roles, dates and what each person replied.
    Write down: The defence, signed and dated by its two witnesses, the one-page explainer, and the relations ledger holding ten coded relationships.
    Finished when: Ten relationships are logged by code with dates and replies, and the owner has said on record whether the reinforcement stays.
    Commonest mistake: Calling it a success because the object feels sturdier. The metric is failures counted, rupees and hours, so report those first and opinions second.

What the student hands in

Nine pieces. Together they are the folder a parent can sit down and read.

1. Question cardOne card naming the object, where it sits, who uses it, and the question: how often does this fail, what does each failure cost in rupees and minutes, and will one reinforcement stop it.
2. Expert interview packFive written questions for a carpenter, welder, mechanic, tailor or maintenance technician, your load-path drawing and failure count attached, sent by your teacher from the school address with the date and channel of the request logged, and the reply recorded word for word.
3. Evidence logEvery tally sheet with its date and counter, the dimensions in millimetres, a photograph of each repair scar, every price with the shop it came from, and the timed minutes lost per failure.
4. Failure logThe counts you lost track of, the load that slipped, the fortnight interrupted by a holiday, the reinforcement that worked loose in week one, and what each of them did to the comparison, all dated.
5. The buildThe fitted reinforcement itself with its dimensioned drawing, plus the test rig used for the hundred uses, and the two charts of two bars each — failures per hundred uses before and after on one, failures per fortnight before and after on the other, each on its own axis in its own unit, because the two rates share no scale.
6. One-page explainerOne page a neighbour reads in ninety seconds: the object, the failures per hundred uses, the rupees and hours per year, the one change, the after-counts, and what this test cannot tell anybody.
7. Identity cardA name and a one-line promise for the reinforcement, so the household can ask for it by name, plus the single sentence you want repeated when somebody else's latch gives way.
8. Relations ledgerTen coded entries, no names in the folder: E1 the professional who repairs these, A1 to A3 the people affected who use the object daily, P1 to P3 the peers who checked your tally, and R1 to R3 those who were sent the charts and replied. Each entry carries a role, a date and what they said. The single sheet matching codes to names is held by the school and destroyed after moderation. No health, financial-hardship or literacy information about any named person is recorded anywhere in this folder.
9. The defenceTen to twelve minutes of unseen questions, answered live in front of two witnesses who sign and date the page: the object, the failure point close up, the definition of one use, both before-counts, the change fitted, both after-counts, the two separate charts and why the two rates are never put on one axis, and the limits you accept without argument. A recording is optional evidence and never the requirement; on the No-Tech route there is no recording at all.

The expert they have to find

Ten logged relationships are required before this project can be marked. One of them is an expert, and this is who.

A carpenter, welder, motorcycle mechanic, tailor, plumber or building maintenance technician — somebody paid to repair this class of object, who therefore knows which part goes first and how soon it comes back.

How to find one

List the institutions and the roles, not individuals. A furniture workshop, a welding shop, a tailoring business or a hardware supplier; the maintenance technician of a school, hospital, hotel or factory, reached through the office by asking for whoever fixes the doors; a motorcycle or cycle repair business, whose mechanics see the same failure many times a week. Your school's own caretaker or maintenance staff count and are often the easiest to reach. You name the type of business and the role you want; your teacher makes the approach from a school address, and no learner contacts a workplace, searches for a named individual or turns up at a counter to ask.

What to say

Dear [name or role], I teach at [school]. One of my learners has counted how often one small object fails across one hundred identical uses and across a fortnight of ordinary use, and has costed each failure in rupees and minutes. Could you spare fifteen minutes — on a call with me present, or by written reply, whichever suits you? Their five questions are below.

What to ask

  • Of the ones people bring you, which part fails first, and what is it about that part that makes it first?
  • When you repair this, do you put it back exactly as it was, or do you change something, and what do you change?
  • How long does your repair last compared with the original, and how do you know that?
  • What would you have to see to say a thing is genuinely worn out rather than badly fitted?
  • If somebody wanted this to stop failing and could spend nothing at all, what would you tell them to do?

If no reply comes, you submit the questions exactly as your teacher sent them, the dated record of the attempts, and one named published source — a manufacturer's fitting instruction, a maintenance manual, a component standard — in place of the answers. That route scores in full. The gate is met by asking properly and logging it, never by pressing anybody into replying.

The defence

Eight of the twenty marks. A student who cannot answer these has not finished, however good the artefact is.

  • Would the failures have dropped anyway without your change, and how do you know?
  • Your hundred-use chart and your fortnight chart point in different directions. Which do you believe, what would settle it, and why can those two rates never be drawn as four bars on one axis?
  • How many failures did your before-count actually contain? If it is under about five, tell me what your rate is worth and what you did about it.
  • You counted for fourteen days before and fourteen days after. Convince me those two fortnights were comparable, and name what was not.
  • If your reinforcement works loose in three months, what was this project worth, in rupees and in hours?

How far a student can take it

starterYou choose one object, ask three users how often it fails, count the repair scars, run one hundred identical uses counting failures, and put your five questions to one professional who repairs these for a living, through your teacher.
practitionerYou define one use yourself and defend that definition, cite every price to the shop it came from, and produce two before-and-after charts, one per unit, that a stranger reads correctly without you explaining the axes.
researcherYou write the test protocol before the first count, justify one hundred uses and fourteen days rather than fewer, and quantify the error your tally, your load and your single tester introduce.
contributorYou set your own measured failure rate against a published component or maintenance standard, printing the figure you counted and the published or rounded figure side by side rather than one in place of the other, defend your method to a maintenance engineer who disagrees, and publish your tally sheets, dimensions and drawings through your school, where your school agrees they may be published, so others can repeat it.

If you want to go further

Fit the same reinforcement to an identical object in a second household and run the identical hundred-use test on both.

When it goes wrong

  • If nobody will talk to you - then ask your teacher to take the next name from the school's brokered contact list and send the same five questions from the school address, accept a written reply as a full answer, or sit in on a call with your teacher present. You do not go to a market, a workshop or a counter to ask on your own.
  • If the household or the site says no - then move to the school version: run the same twenty steps on a school object with a member of staff, and log the refusal as a dated line in the failure log. Nobody is asked twice, and if anyone reacts angrily, stop, leave and write it down. Then tell the adult who knows where you are, the same day, and tell your teacher before the next session.
  • If your before and after look the same - then check first whether the change is still fitted and still tight, count how many times the object was actually used in each fortnight, and report the null result with both use-counts beside it.
  • If you cannot produce the failure in a controlled test - then drop the hundred-use test, say so plainly, extend the ordinary-use log to a fixed longer period before and after, and make that log your only metric.
  • If you run out of time - then shorten both logging periods to the same seven days rather than dropping the baseline, and write the shortened period on the chart itself.

Before you start

Safety and consent.
  • Nothing electrical and nothing gas. A plug top, a switch plate or an extension lead is examined only with it unplugged from the wall and the cover left screwed shut; nothing is opened, stripped, rewired or plugged in to test, and nothing attached to a gas pipe, cylinder, regulator or burner is part of this project.
  • Feet on the floor. No ladders, no stools, no climbing, no roof and no work above your own standing reach; if the object sits out of reach, an adult brings it down or you choose a different object.
  • Test loads fall onto empty floor and nothing else. Load with weight you can hold in one hand — filled bottles, a bag of rice, a bucket half full — hung or placed so that if it drops it lands on bare floor, never over a foot, a hand, a lap, a pet or a phone; stand to one side, and for anything under tension, spring, elastic or wire, wear eye protection or keep your face turned away.
  • Every trip out of the house for this project — the hardware shop, a price check at a second shop, a look at an identical object elsewhere — is made with a named adult who goes with you and stays within sight, not an adult who merely knows where you are. Nothing is done after dark, and no workshop, shop or business is approached by you for the interview; your teacher makes that contact from the school.
  • Out of scope: anything structural or anything holding a person off the ground — a stair tread, a balcony rail, a ladder rung, a swing, a bed frame, a roof or wall fixing. A loose chair joint may be measured and reinforced only with the chair empty on the floor and loaded by hand with weight; no person is ever the test load. No power tools unless an adult is holding the work, and no cutting, drilling or heating on your own.

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