Isometric Drawing - Trammel Method Graphic Communication Department of Technological Education

Isometric Circle – trammel method Department of Technological Education Isometric Circle – trammel method Start the isometric circle by drawing the front elevation and the plan of the cylinder to be drawn.

Locating Lowest Corner + Drawing Isometric Crate Department of Technological Education Locating Lowest Corner + Drawing Isometric Crate Choose a suitable point ‘X’ on the elevation and plan and a suitable position to start the isometric view. x Draw an isometric crate to fit the isometric view into. Use 30o and vertical lines for the angles of the lines. The overall size of the crate should be the exact size of the isometric view to be drawn. x x

Finding Centre for Isometric Circle Department of Technological Education Finding Centre for Isometric Circle Draw centre lines on the isometric view. Use 30o and vertical lines for this. x x

Finding Points on Circumference of Circle Department of Technological Education Finding Points on Circumference of Circle Divide the orthographic circle into sections by drawing random vertical lines. There should be enough lines to be able to construct an ‘accurate’ curve in the isometric so you should aim for a minimum of 4 points for each quarter circle. In the example shown there are 4 points for each part so this shows the minimum standard required. Number each of the lines. x 4 1 2 3 5 6 7 x

Transferring Circumference Points to Isometric (1) Department of Technological Education Transferring Circumference Points to Isometric (1) Each of the random lines need to be transferred to the isometric view. This is done by placing a trammel on the centre line of the front view and marking where each of the random lines passes through the centre line. x 4 1 2 3 5 6 7 trammel 1 2 3 4 5 6 7 Number each of the points. trammel 1 2 3 4 5 6 7 Using the trammel transfer each of the marks to the isometric view. 1 2 3 4 5 6 7 x Draw vertical lines through each of the points found.

Transferring Circumference Points to Isometric (2) Department of Technological Education Transferring Circumference Points to Isometric (2) Using the trammel, measure the vertical distances from the centre line up and down to each of the points on the circumference in turn. x trammel 2 1 2 trammel 3 2 1 2 3 trammel 4 3 2 1 2 3 4 trammel 4 3 2 1 2 3 4 trammel 3 2 1 2 3 4 trammel 4 3/5 2 1 2 3/5 4 1 trammel 2 1 2 2 3 trammel 4 3/5 2 1 2 3/5 4 5 trammel 4 3/5 2/6 1 2/6 3/5 4 trammel 4 3/5 2/6 1/7 2/6 3/5 4 6 7 trammel 4 3/5 2/6 1 2/6 3/5 4 trammel 4 3/5 2/6 1/7 2/6 3/5 4 Transfer each of these dimensions onto the isometric view. 1 2 3 4 5 6 7 x

Drawing Front Isometric Curve Department of Technological Education Drawing Front Isometric Curve Draw a smooth curve through each of the points to show the circumference of the isometric circle. x 4 1 2 3 5 6 7 1 2 3 4 5 6 7 x

Finding Thickness of Cylinder on Isometric Department of Technological Education Finding Thickness of Cylinder on Isometric Project each of the points on the front curve of the isometric back at 30o so that the width of the cylinder can be marked. x 4 1 2 3 5 6 7 Measure the width of the cylinder on the plan using a trammel. Because the thickness of the cylinder in this case is constant only one size needs to be measured, although this may not always be the case. Transfer the size measured onto the isometric and mark each point found with a small dot. 1 2 3 4 5 6 7 x

Finding Tangent Points on Isometric Department of Technological Education Finding Tangent Points on Isometric It is necessary to find two final points – the tangent points. These points are found in the same way as the previous points. By drawing diagonal lines on the elevation and isometric you will be able to find where the corresponding points occur – points A and B. x A 4 1 2 3 5 6 7 A These points can then be projected back and measured as before to find the final positions. 1 2 3 4 5 6 7 B B x Finally, draw a smooth curve through each of the points found.

Drawing Back Isometric Curve and Tangent Edges Department of Technological Education Drawing Back Isometric Curve and Tangent Edges To finish the drawing darken the required part of the outline of the curve. x 1 2 3 4 5 6 7 1 2 3 4 5 6 7 A B Complete the two edges to join the two curves together.

The Final Drawing x This is the final Isometric View of the cylinder. Department of Technological Education The Final Drawing This is the final Isometric View of the cylinder. x

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