True Shapes

True Shapes: In The Exam

(could be a Post It note or piece of paper). To identify a True Shape for both X-X and Y-Y in the drawing below, you will need a trammel or compass. Trammel (could be a Post It note or piece of paper).

To work out the True Shape for X-X in the orthographic drawing below, you will first need to work out the true length for your true shape. Use your trammel to mark this length. The True Length of surface X-X can only be taken from the End Elevation in this drawing. This is because surface X-X is sloping away from you in the plan, so the length appears shorter.

The height is therefore this: Use the marks on your trammel to see if the height of any of the options below match up. Option 1 Option 2 Option 3 Option 4 So far, option 2 and option 4 have the right height.

Next, we will need to work out the width of X-X. Use your trammel to mark the width. You can find this on the Plan or the Elevation (as shown).

The width is therefore this: Use the marks on your trammel to see if the width of any of the options below match up. Option 2 Option 4 Therefore, the correct true shape for X-X is Option 4 since it has right height and width.

To work out Y-Y in the orthographic drawing below, you will first need to get the true length for our true shape. Use your trammel to mark this length. You can find the height on the End Elevation (as shown).

The height is therefore this: Use the marks on your trammel to see if the height of any of the options below match up. Option 1 Option 2 Option 3 Option 4 So far, option 1 and option 2 have the right height.

Next, we will need to work out the width of Y-Y. Use your trammel to mark this width. You can find the width on the Plan (as shown).

The width is therefore this: Use the marks on your trammel to see if the width of any of the options below match up. Option 1 Option 2 Therefore, the correct true shape is Option 1 since it has right height and width.

True Shapes: Drawing True Shapes

Line of Symmetry To work out a “true shape”, draw a horizontal line of symmetry going through the plan of the shape (this can be done to cones, cylinders hexagonal, triangular pyramids & prisms). We can then use the Horizontal line of Symmetry as the Datum Line to make it easier to draw the True Shape. Datum Line PLAN Projection Lines ELEVATION

Number each corner of the Plan before projecting the corners / numbers down to the End Elevation. Project these numbers at a Right Angle from the Cut Shape on the Elevation. PLAN ELEVATION

Add in a Datum Line drawn parallel to the Elevation’s Cut Surface which represents the Horizontal Line of Symmetry in the Plan. Since we know Number 2 lies at the end of the Horizontal Line of Symmetry, it will also lie at the end of the Datum Line. Therefore, this point could be added in. 2 PLAN 2 Next, to work out where numbers 1 and 3 will lie, we will need to use a compass or trammel to transfer the distance from the Horizontal line of symmetry to number 1 first. ELEVATION

2 1 Transfer the size distance between the Horizontal Line of Symmetry and Number 1 onto the projected line from the Datum Line shown. PLAN 2 ELEVATION

Repeat the last stage on the other side for distance 3. 2 1 Repeat the last stage on the other side for distance 3. PLAN 2 ELEVATION

You should then be left with this True Shape as shown. 2 1 PLAN 2 ELEVATION