Spiral Development

Spiral developments
Spiral developments are usually considered the most awesome and difficult developments but are in actual fact quite simple to develop . It is once again important to note that accuracy in the layout is accuracy in the development.
Spiral facts
-Horizontal spirals have no bend lines but are pulled or pressed over a jig to form the complete article
-vertical spirals have bend lines and can also be rolled
-on spiral developments , accuracy is of the utmost importance , therefore ,all circumferential and diagonal dimensions have to be calculated.
-The pitch of a spiral is the height of rise. A spiral has 360 degrees.
Drawing the spiral (horizontal plane)
draw the pitch line to length as the center line of the spiral and at the bottom , draw the half plan of the spiral (both inside and outside diameter ).
NB: it is advisable to first complete the outer diameter spiral and then only project up the inner diameter spiral as will lead to less errors due to all the projection lines that can be confusing .
For more information go to :
http://www.dtic.mil/cgi-bin/GetTRDoc?AD=ADA382590