These change elbow fittings will save time, space and material. It will also give you a more professional look on the completed job. We show this fitting 60 Degrees but use the same method for any angle and size. The inside throat radius is 2", however we do show the same fitting near the end with a 1 to 1 radius to width ratio.
Draw your base line, leaving enough length for the fitting and the inside throat. Using a protractor or speed square draw a reference line intersecting the base line at 60 degrees.
Set your dividers at the throat distance of 2" (or the distance you choose for your throat)
Placing one end of your dividers on the (A) draw an arc to meet the 60-degree reference line. This establishes your inside throat.
From (B) measure up 4" and make a reference mark. At that point (C) draw a line perpendicular to your 60-degree line as we did with the red dashed line. This establishes your 4" side of the fitting.
On the baseline make a reference mark 6" to the left of your throat. From that point (D) draw a perpendicular line until it intersects with line C. At point (E). Set your dividers at the distance of point (E) to (D), and place one end on (E) and draw an arc up to line C,E.
From (F) draw a line perpendicular until it intersects with your base line.
Here we are setting up the point for the final arc.
Now set your dividers at the distance of point (G) to Point (D). Place one end on point (G) and the other end on Point (D). Draw an arc from (D) to (F).
(Not Shown) but by placing your dividers on point (G) and (D) and extending the distance 1/4" draw an arc for your lock. This measurement may be different depending on the machine you use.
Add the 1" on both sides for your s-slips & drives.
2 Required (Cheeks)
(1) heel and (1) throat required.
Width + allowance for Pitts. / Total length which would be distance (D to F) + (F to C) + allowance for s and drives which normally are 1" each side.
Here is an example of the same fitting with the exception we used a 1 to 1 radius to width ratio. The Layout for these and any change elbow are all basically the same. It's a matter of learning where to find your points for drawing the arcs.
Copyright 2001 TheSheetmetalShop.Com