Revision Topic - Prisms and Cylinders

Today we revised prisms and cylinders.

First we had to construct the front elevation.  I would start with the hexagonal base and then tackle the cylinder.  This proved not too much of a problem for the class as a whole, but we missed out some hidden detail.

Remember that numbering will aid your construction.  You should number the hexagon starting at the shortest side and going round the shape.  You should use clockface construction on the cylinder and therefore number it like a clock.  It will then be much easier to follow your construction lines and plot the points you need.

(Note that the bottom of the cylinder is also a slope and therefore you will need to plot this circle also)

From this image you can also see the start of the construction for the true shape.  Remember that the angle between the sloping surface and the construction lines must be 90 degrees as if you are looking straight onto the slope.

Using these construction lines and projecting them onto the center line (or drawing your own center line) you can use the distances from the center line to outline of the slope from either the front elevation or the plan.

The Surface development is drawn along the "ground".  You must draw the ground first to know that your sizes are correct.  From the plan use a compass to transfer the sizes between points.  As this is a hexagon, all the distances will be the same. Number these points as you have your plan. From each of these points project horizontally away from the ground.  These are the height lines.  From the elevation or end elevation mark the height of each line along the height lines.  Fill in the outline of the top by joining all the heights together and draw your fold lines.

These stages are the same for all prisms and cylinders,  the only difference being that if it is a cylinder you have to create your own points using the clockface construction, and if it is a prism you will have the points from the edges and you must use these.