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Classroom activity Grade 11 Art & Music

Brackenhill Filter Section: A Scale Drawing Relay

Teams of four build a large cross-section of a fictional plant's sand filter on butcher paper, adding one layer per round at a single stated scale.

Objectives

  1. Students will convert filter layer thicknesses into drawn thicknesses at one scale.
  2. Students will test two candidate scales against a fixed sheet and reject the one that overruns it.
  3. Students will explain why a section drawing holds one scale across every layer.

Vocabulary

Key words: section, cut plane, scale, live area, freeboard

Teacher overview

A section drawing shows a structure as though it had been cut open, and it is the only view that lets a reader see what a sand filter is made of. This relay has teams of four build one large section of a filter box at the fictional Brackenhill Water Treatment Plant, adding a different part of the drawing in each of four rounds. The relay format carries the lesson, because each round passes the drawing to a different student, and every added layer has to line up with what the previous round drew at the same scale. Once the four rounds are done, a scale marshal from another team audits the sheet, which is when a team finds out whether the scale held from the first round to the last.

Activity Directions

  1. Setup and briefing (8 min). Tape one sheet of butcher paper flat for each team of four and give every student the handout. State the scale the class will use, which is 2 inches of drawing for every 1 foot of the real filter, and the border, which is 3 inches on all four sides. Have each team compute handout items 1 through 3 before drawing anything, then check those three answers at the table.
  2. Round 1, box and under-drain (9 min). The first team member draws the filter floor, the two side walls to full drawn height, and the under-drain layer at its drawn thickness. Nobody else may hold a pencil during the round.
  3. Round 2, gravel and sand (9 min). The second member adds the gravel support layer and the sand media layer above it, measuring up from the top of the under-drain rather than from the floor. Members who spot an error may say so but may not draw.
  4. Round 3, water and freeboard (9 min). The third member draws the water surface at its stated depth above the sand, then the freeboard up to the top of the wall, and shades the water column lightly.
  5. Round 4, annotation (9 min). The fourth member adds the layer labels, three dimension strings, the graphic scale bar, and a title block naming the plant, the view, and the scale. Handout items 9 and 10 govern this round.
  6. Scale marshal audit (6 min). Send one member of each team to audit a different team's sheet. The marshal measures three drawn thicknesses against the handout answers and marks any that miss by more than a quarter inch. The activity ends when every sheet has been audited.
  7. Debrief (10 min). Ask two questions and take answers from at least three teams. First, which round produced the most drift, and what caused it. Second, what a plant operator could read off this drawing that a photograph of the filter would not show.
Brackenhill Filter Section: A Scale Drawing Relay — Grade 11 Art & Music
Name: ____________________________ Date: ______________

Student Handout

The fictional Brackenhill Water Treatment Plant has a rapid sand filter in a rectangular concrete box 12 feet wide. Measured from the floor upward, the contents are an under-drain layer 1.5 feet thick, a gravel support layer 1.0 feet thick, sand media 2.5 feet thick, water standing 4.0 feet above the sand, and 1.0 feet of freeboard to the top of the wall.

The class scale is 2 inches of drawing for every 1 foot of the real filter. Your butcher paper is 36 inches wide and 30 inches tall, with a 3 inch border on all four sides. Use 72 points to the inch.

  1. How tall is the filter wall from the floor to its top?
  2. At the class scale, how tall is the wall on the drawing?
  3. At the class scale, how wide is the box on the drawing?
  4. How thick is the sand media on the drawing?
  5. How thick is the gravel support layer on the drawing?
  6. How deep is the standing water on the drawing?
  7. The 3 inch border leaves a live area 30 inches wide and 24 inches tall. Does the section fit? Give the width and the height left over.
  8. A team proposes 3 inches of drawing for every 1 foot instead. How tall would the wall be, and does that fit the live height?
  9. Layer labels must be at least one quarter of an inch tall. What is that height in points?
  10. The graphic scale bar represents 5 feet. How long is the bar at the class scale?
  11. The under-drain is the thinnest layer on the sheet. Explain why it must still be drawn at the class scale.
  12. Explain what this section shows a reader that a photograph of the filter from above would not.

From Water for Schools (waterforschools.org). This material is in the public domain (CC0) and may be copied, edited, and shared freely.

Answer Key
  1. Answer: 10 feet. Adding 1.5, 1.0, 2.5, 4.0, and 1.0 feet gives 10.0 feet.
  2. Answer: 20 inches. Multiplying the 10 foot wall by 2 inches per foot gives 20 inches.
  3. Answer: 24 inches. Multiplying the 12 foot width by 2 inches per foot gives 24 inches.
  4. Answer: 5 inches. Multiplying the 2.5 foot sand layer by 2 inches per foot gives 5 inches.
  5. Answer: 2 inches. Multiplying the 1.0 foot gravel layer by 2 inches per foot gives 2 inches.
  6. Answer: 8 inches. Multiplying the 4.0 feet of standing water by 2 inches per foot gives 8 inches.
  7. Answer: Yes, with 6 inches of width and 4 inches of height left over. The drawing is 24 inches wide inside a 30 inch live width, and 20 inches tall inside a 24 inch live height.
  8. Answer: 30 inches, which does not fit. Multiplying 10 feet by 3 inches per foot gives 30 inches, which is 6 inches taller than the 24 inch live height, so the proposal is rejected.
  9. Answer: 18 points. Multiplying one quarter of an inch by 72 points per inch gives 18 points.
  10. Answer: 10 inches. Multiplying 5 feet by 2 inches per foot gives 10 inches.
  11. Answer: Every thickness on the sheet is read against the same scale bar, so a layer drawn thicker than its scale states reports a filter that was never built. Enlarging the under-drain to make it easier to letter also pushes every layer above it upward, which throws off the water surface and the freeboard even though nobody redrew them.
  12. Answer: The section shows the order and thickness of the layers below the water surface, which is exactly what a photograph from above hides. A reader can see that the sand sits on graded gravel, that the gravel sits on the under-drain, and how much water stands above the media, none of which is visible from the walkway.

Differentiation

Support

Give the team a conversion strip listing 1.0, 1.5, 2.5, 4.0, and 10.0 feet with their drawn lengths already computed, so the relay rounds spend their time drawing rather than calculating. Pre-mark the border on the butcher paper. Assign the annotation round to a student who wants a defined task, and provide a printed title block to trace.

Extension

Ask a team to redraw the same section on a sheet half as wide, choosing a new scale and proving that both the width and the height fit inside the new live area. They should then add a second, enlarged detail view of the sand and gravel boundary at a larger scale, label that view with its own scale, and write one sentence on why a drawing may carry two scales when each is stated on its own view.

ELL supports

Pre-teach section, cut plane, freeboard, and scale bar against a labeled sample section kept posted for the whole activity. Provide a bilingual card pairing floor, layer, thickness, and surface with a small diagram. Allow items 11 and 12 to be answered with a labeled sketch plus a short phrase, and offer the frame "The drawing must use one scale because a reader measures ___."

Extensions

Have teams add a backwash arrow set to the finished sheet, showing the reversed flow that lifts and cleans the sand, drawn in a lighter weight than the section itself so the arrows do not compete with the structure. Ask each team to write a one-sentence caption for the arrows and to say why the caption belongs beside the drawing rather than inside it. Plant operators read and mark up drawings like these during a filter rebuild, which is worth naming when the sheets go up on the wall.