I'll be referring back to the picture with all the measurements on the previous page quite a lot, so if you click here you should get a pop up window with the picture in it. The damn things have to be good for something after all!

Job No.1 is to set the headstock fixture to the required angle ("D" in the picture). It's always a good idea to make sure the jig is actually level before you do this as someone may have shifted it to sweep underneath it for you.... But having set the fixture to the correct angle the headstock is then fitted to it at the correct height. Now I always work with the top face of the jig as 4" above the ground level (usually 1" less than the ground clearance) so the headstock is fitted to the jig at a height of "C" minus the 4" above the jig face.

That done the axle plate fixture is set up to "F" minus the same 4" to get the height of the axle slots above the jig face, the axle plate fixture is then adjusted along the jig to get the "E" dimension right.

Next up is the motor. This is positioned on the jig with 1" box section under it and chocked up to sit level.This plus the weird 4" will give 5" of ground clearance ("B"), if you want to go lower adjust accordingly. The 1" box section under the motor is going to act as the guide for the bottom of the frame rails. Once the motor is set up it is moved along the jig to get dimension "A" right, the motor sprocket to rear axle measurement. At this point I establish that the motor is true on the jig by using a spirit level across the motor, and straight edge on a machined face (take the points cover off) to check that it's not "skewed" in the jig. The spirit level is used to make sure the straight edge is level and then you "eye" the gap between the edge of the jig and the straght edge for parallel. Once all that's true I check that the motor sprocket is offset from the jig centerline by the amount needed. You really need to get this bit right as the motor is going to act as the jig to position the motor mounts so if you screw it up now.........

Fig.1

Fig.1 shows the jig with the headstock and axle plates all positioned as per the measurements that were taken originally. The next step is to figure out the dimensions of the top tube and seat rails. A good idea at this point is to measure how long the gas tank is as it's a real pain if it doesn't fit because the back bones too short once you've built the fram. Don't forget to leave some clearance for the forks on full lock. With the wheel at the front of the axle slot, you'll need to have enough clearance for the fender so the crosstube in front of the wheel wants to be about "F" plus 1" from the front of the axle slot. Seeing as this will also be the back of the seat you know should have some idea of the seat area try cutting out a piece of MDF or plywood that shape and sitting on it as its not to late to adjust things if you suddenly realise your butt is three sizes larger than you imagined it to be! Once you've got the dimensions down draw them out on another piece of board.

Fig.2

This is where we start cutting tube. Cut the back bone first allowing 2 or 3 inches over length then cut two pieces for the seat rails again allowing surplus for cutting in to the top tube and I like to overhang the axle plates by an inch or two so about 3 inches longer than the "drawing" implies. Next I bend the seat rails so I need the angle for the bend and the position of the bend line. I get the angle by using my home made angle finder as in Fig.3.

Fig.3

Then I need to establish where the bend line is going to be. To do this I use a bend that I've marked to show where the index on the former was prior to bending it, this mark is transferred to the drawing by eye which then lets me measure it up to get a dimension I can use on the seat rails.

Fig.4

The bend line is then transferred to the seat rails and the seat rails and the angle finder are taken to the bender and the first seat rail is set up using the bend line mark which is 16" from the end of the tube in this case.

Fig.5

The angle finder is then positioned with one leg parallel to the tube, and then i hit the button and bend the rail slightly past the other leg of the angle finder to allow for spring back once the pressure is released.

Fig.6

Before the pressure is released though, it is important to mark the bender so the bend can be repeated. On mine I put a felt pen mark across the static and moving sections, like this.

Fig.7

Then I release the bender, and set the auto stop so that I get my pen mark lined up exactly when the bender stops. Then I bend the other rail so I get a matched pair.