By James A. Morikawa
Before I can begin mitering the tubes and stays, I need to adjust the frame jig to the customer's desired frame specifications.
Once adjusted, I get all the actual mitering angles, and lengths directly from the jig. I once did, but no longer use full size drawings or formulas for mitering tubes.
So, the need of "Setting Up The Fame-Jig" . . . I will briefly describe my process.
I use a modified Henry James frame-jig. Modifications were made to better suit my building procedures.
Pictured above, is the use of jig's protractor to set the seat-tube angle.
I do write frame specs on the jig for easy reference, using a red or black felt-tip pen. This makes the specs readily availiable. They can be easily erased by wiping with a cloth and lacquer thinner.
In the above picture, I've set up the Head-tube angle.
Here, I'm checking and will adjust for the vitual Top-tube Length.
Here, I'm checking and marking off where the bottom of the Head-tube will be. Note the horizontal bar, a wheelbase line reference. I use this to aid in measuring out the "Wheelbase Line to Bottom of Headtube length". The rear-triangle dimensions have already been adjusted — in relation to bottom-bracket-drop, and chain-stay length.
Knowing where the bottom of the headtube is an important reference point for me, and is marked on the frame-jig.
Here's a typical "adjusted to specs" frame jig. I will be getting all mitering angles and lengths directly off the jig.
Anyway, the idea is to adjust the frame-jig to the desired dimensions, which will contain all the mitering angles, and lengths — an actual plan to work with.
That's it for this page. Have a great day.