How to draw exhaust pipes the good old way.

First use a welding rod to determine the route of the expansion chamber round the engine and other obstacles.

Then take each of the cone sections and decide how to place the angled bends on it and draw the cone on a piece of cardboard.

Then draw the top halfcircle and use the same radius to divide it into 6 segments and draw the 5 degree angles on each  en

Use a really long Compass to take the contact points and transfer them to the unfolded cone.