Parallel Line Development

Pipe with Angle Cut

Draw the elevation as shown , divide pipe into 12 equal parts and number 1,2,3 etc . always starting at the shortest side then project division lines through the whole length of the pipe . Now project the points of the projection lines out normal to the pipe centre line and number these lines as well .(You will notice that at the top where the pipe is cut normal, all the points fall on the same line)


Now calculate and measure the circumferance along the projection line to give us points 1.1 which is the length of the plate required to roll the pipe .The following step is to divide this length 1.1 into 12 equal parts and number these divisions 1 2 etc then project them down to intersect the projection lines drawm across from the elevation. Where the like numbered projection lines cross , we have the points of our development .Complete the development by joining these points with a continous caved line


NB: on right pipes the circumference must always be measured along line normal to axis of the pipe
For more information on parallel line development visit : http://jwilson.coe.uga.edu/EMAT6680/Parsons/MVP6690/Essay2/round.html

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

Introduction to Triangulation

The triangulation method used for developing is the most versatile , as it is possible to do any development with triangulation , and in fact , as there are many developments that can only be done by triangulation .It is therefore of the utmost importance to understand the basic principles of triangulation
Triangulation theorem
Rule:To obtain the true length of a line , take the plan length and place , normal to the wertical height between the points considered
example:
(a) Draw a vertical line with height corresponding to vertical height of the other shape eg cone
(b)Take plan length of XY and place normal to the vertical line drawn to represent the vertical height
(c)Now set compass to the length across the hypotenuse of the triangle formed thus .This will represent the true length x.y (check with front elevation )
We can summarise this rule as follows :THE PLAN LENGTH AGAINST THE VERTICAL HEIGHT AND MEASURE THER SLANT LENGTH WHICH IS THE TRUE LENGTH
THE MAIN POINTS TO OBSERVE
(a)Draw neatly and accurately
(b)Plan view is of most importance
(c)Draw front elevation (d)Determine the bend lines
(e)Number each plane differently ir bottom plane A,B,C etc and top plave 1,2,3 etc
(f)Calculate the circumference and obtain unit length (circumference+12)
(g) Obtain true lengths
(h)Start developing on the opposite side of the required joiint and work symmetrical about the starting points
(i)As you complete each seccesive triangle mark the points and draw the appropriate lines
NOTE :by numbering the two planes different ly , you immediately know which dimensions taken from the plan are true and for which we should find the true lengths .Measuring between A , B, Cetc and 1,2,3 etc , will be true lengths , whereas if we measure from the letters to numbers we have to find the true lengths
For more information on triangulation visit
http://www.craftsmanspace.com/free-books/triangulation-applied-to-sheet-metal-pattern-cutting.html

Table of Contents / Home Page

Chapter I
Radial Line Development
TOPICS INVOLVED
-Divisions and numbers
-True lengths
-Central ball theorem

Chapter II
Triangulation
TOPICS INVOLVED
-Triangulation theorem
-Determining the bend lines
-Square to round on the parallel planes (centrally placed)
-Square to square on parallel lines (centrally placed)

Chapter III
Parallel line development
TOPICS INVOLVED
-Pipe with a cut
-division and numbers
.