Bearing Life to Calendar Years¶
Run the Bearing Life to Calendar Years MicroSim Fullscreen
This sketch is built on the FanPedia MicroSim kit. To run it in the
p5.js editor, add the ../shared-libs/ files it loads
(fanpedia-sim.css, fanpedia-core.js, fanpedia-p5.js, fan-models.js),
or their published URLs, to the editor's index.html before pasting
ch17-bearing-life-calendar-years.js.
About This MicroSim¶
A bearing's L-10 life is the number of operating hours at which 10% of a population of identical bearings is expected to fail; its L-50 (average) life is five times as long. Both are hours of running, not calendar time. This MicroSim converts a rating to years for a stated duty schedule, the way Chapter 17 does:
- Annual hours = hours per day × days per week × 365/7
- Years = rated hours ÷ annual hours, rounded to 0.1 year
- L-50 hours = 5 × L-10 hours
The sim starts with five challenges, in this order. Each asks for one number, in years:
| # | Rating | Schedule | Model answer |
|---|---|---|---|
| 1 | L-10 40,000 h | 24 h/day, 7 days/week | 4.6 years |
| 2 | L-10 40,000 h | 8 h/day, 5 days/week | 19.2 years |
| 3 | L-50 of a bearing rated L-10 20,000 h | 24 h/day, 7 days/week | 11.4 years |
| 4 | L-10 60,000 h | 16 h/day, 5 days/week | 14.4 years |
| 5 | L-10 100,000 h | 12 h/day, 6 days/week (illustrative schedule) | 26.6 years |
An answer is correct when it is within 2% of the model answer. You get two attempts. A wrong first answer gets a hint that names the slip or the step (no numbers); a second wrong answer shows the model answer and the worked conversion, and the challenge counts as missed. Once a challenge is resolved, the sim shows the annual operating hours, the model answer and your answer side by side, writes out the calculation, and fills in bars comparing the L-10 and L-50 years of the same bearing. A week grid (7 days by 24 hours) shades the hours the fan runs.
Mastery is 4 of 5 challenges correct on the first attempt. After challenge 5, Explore mode unlocks the four inputs (L-10 rating 20,000 to 100,000 hours in 20,000-hour steps, 1 to 24 hours per day, 1 to 7 days per week, and the rating shown, L-10 or L-50), and a table compares FanPedia's published years (p. 90) with the model. The model lands within 2% of every published cell; the small differences come from rounding and from FanPedia counting some cells with a 52-week year. Explore mode is never scored.
How to Use¶
- Read challenge 1, type the number of years in Your answer and press Check (or Enter).
- A correct answer reads "✓ Correct: n years." in a solid green box. A wrong one reads "✗ Not quite." with a hint in a dashed red box; use the second attempt.
- Press Next challenge (or Enter) and repeat for challenges 2 to 5. Challenge 3 asks for an L-50 life from an L-10 rating, so multiply by five first. "Challenges correct: n of 5" keeps the running score.
- After challenge 5, press Start exploring. The panel shows the first-attempt score and the mastery line. Move the sliders and switch Rating shown between L-10 and L-50: the hours and years update at once. Notice that switching to L-50 multiplies the years by exactly five while the bearing is unchanged, and that cutting the hours per day changes the calendar life as much as a different rating does. Start over clears the score and returns to challenge 1.
Keyboard: Enter checks the answer, and Enter again goes to the next challenge. Tab reaches the answer box, every button, the rating selector and the three sliders; the arrow keys move a focused slider.
Data label: "Source: FanPedia p. 90 · 365/7 weeks per year" (challenge 5 reads "Illustrative schedule · Source: FanPedia p. 90"), at the bottom left of the drawing.
Iframe Embed Code¶
You can add this MicroSim to any web page by adding this to your HTML:
<iframe src="https://moroshek.github.io/FanTASTIC-textbook/sims/ch17-bearing-life-calendar-years/main.html"
height="687px"
width="100%"
scrolling="no"></iframe>
Lesson Plan¶
Learning Objective¶
The learner will calculate the expected calendar life in years of an L-10 or L-50 bearing rating for a stated daily and weekly duty schedule, to within 2% of the model value (Bloom: Apply, verb: calculate).
Audience¶
Adult professional development: new application engineers, sales staff, representatives and facilities staff.
Duration¶
10-15 minutes
Prerequisites¶
- Bearing life as a statistical estimate (Chapter 17)
- L-10 and L-50 bearing life, and the L-50 = 5 × L-10 conversion (Chapter 17)
- The years formula (Chapter 17, "Bearing Life: L-10 and L-50")
Activities¶
- Challenges (5-7 min): Work each challenge with a calculator before pressing Check. Write down the annual hours for each schedule.
- Review (2 min): Compare your annual hours with the sim's, and redo any missed challenge by hand from the worked calculation.
- Explore (3-5 min): Keep the rating at L-10 40,000 hours and move hours per day from 24 to 8. Then switch Rating shown to L-50. Find the FanPedia table row that matches the inputs (it is highlighted) and compare its published years with the model.
Common Misconceptions Addressed¶
- L-50 is a better or longer-lived bearing than L-10: the sim shows both bars for the same bearing, and switching the rating changes the years by exactly five times while the L-10 rating is unchanged.
- L-10 hours equal calendar hours whatever the schedule: challenges 1 and 2 use the same bearing and get 4.6 and 19.2 years.
- L-10 is the time at which every bearing fails: every prompt and the L-10 definition speak of 10% of a population.
Assessment¶
- The running line "Challenges correct: n of 5" counts challenges solved on either attempt. At the end the sim shows "First-attempt score: n of 5" and the mastery line; mastery is 4 of 5 challenges within 2% of the model value on the first attempt.
- Changing the inputs in Explore mode is not evidence of mastery. Ask the learner to explain to a customer why "200,000-hour average life" and "L-10 40,000 hours" may describe the same bearing.
References¶
- FanPedia: The Fan & Blower Encyclopedia - Twin City Fan's reference; p. 90 (Bearing Life Overview) gives the L-10 and L-50 definitions, the five-times rule and the published year tables.
- Rolling-element bearing: life - Wikipedia overview of bearing fatigue life and the L10 rating.
- Twin City Fan & Blower - current product catalogs, which state the L-10 life offered on each fan model.