Question: If you are building a chopper frame, how do you know if your backbone is a standard size or stretched 2 or more inches over? If you are also wanting to purchase a tubing bender, how do you know what CLR (center line radius)die to purchase? What determines your neck height when building a frame in a jig? These questions are what is keeping me from getting started.
someone please advise, Thank you.
Answered by Rick Hedrick (see his cusotm chopper frame blue prints)...
Answer: All stretch measurements are based off of stock measurements. For example if you have a frame that is 6 up and 4 out this simply means that the neck is now re-located 6 inches up on a vertical plane and forward 4 inches horizontally from the stock location. The rake will be the angle of the neck tube in degrees.
Arriving at the CLR for a tubing bender is usually not too difficult. The Centerline Radius is the measurement from the center of the tubing. The most common specification for the arc of a tube bend. Physically, it is the location of the crown of bend; geometrically, it is the continuation of the vertical centerline of the tube into the arc.
An easy way to determine the Centerline Radius is to trace the tube that you would like to bend onto a large piece of cardboard or paper, continuing the pattern until you have made a full circle with the tubing that you are working with. Measure from the center of the tubing to the enter of your drawn circle. This straight line measurement to the tubing is the centerline radius.
Bend dies are available in several different styles. The style chosen will depend on the tube outside diameter (OD) and the centerline radius of the bend as well as the configuration of the machine to be used. The different types of dies are: Spool, One piece, Partial platform, Full platform and Flange.