2 Drop Branch Fitting
- Draw a complete elevation view of a flat cheek of the fitting
- Calculate the true length (height) of the sloped cheek using Pythagoras, A2 + B2 = C2
- Calculate the amount of drop at the crotch. This can be done by percentage. If “the vertical distance to the crotch” is divided by “the total vertical distance”, a percentage of drop can be found. Vert. at crotch / total vert. = % of drop
- Using the % of drop, calculate the actual amount of drop at the crotch
- Bisect the remaining heel section. The remainder of the drop will occur evenly between the crotch and the end of the heel. Divide the remainder of drop in half to find the amount at the heel bisection point
- Bisect the throat section and label this point 50% drop
- label the flat cheek at all points and draw in the element lines. Also label each point with the actual amount of drop at that point. We will use the difference in drop in the True Length Diagram
- Create a True Length Diagram (TLD) with the “difference in drop” between each element line, as the vertical measurements. In this example we have 5 different “drops” within the branch, 0″, 2″, 2 1/4″, 3 1/8″, and 4″. If we look at line C-E, the drops are indicated as 2 1/4″ and 3 1/8″, which is a difference of 7/8″
- Start the pattern with baseline B-A. Make sure you are laying out the inside of the cheek
- Pick up the true length of A-C and swing it from A
- Pick up the true length of B-C and swing it from B, to complete point C
- Pick up the true length of line C-D and swing it from C
- Pick up the true length of line B-D and swing it from B, to complete point D
- Continue building triangles in this manner until the branch is complete
- Complete the straight section of the branch with the calculated sloped length and the given open size
- Use geometric construction, arc through 3 points, to complete the arc