just got out of another intro to metal sculpture class.
i discussed with the teacher how to make the rake spacer block, which i've made once but i think i'll re-do. this time i'm going to precisely control the alignment of the two holes drilled in it, which secure the angle iron bits to its top and the whole assembly to the backboard.
i was thinking about the way this design works last night. it breaks down the directions in which motion needs to be controlled and controls each one with a different mechanism.
1. the dropouts need to be held apart 100 mm
2. they must be suspended above the backboard top by the rake amount + the steerer's radius
3. they must be aligned perpendicular to the steerer axis
4. they must be secured a specific distance from the crown
the arrangement is made somewhat clearer by looking at the Talbot jig drawings, upon which all this is based.
anyways, by replacing talbot's pine axle block i'm able to independently control each variable. the pine block controls 2 and 3 with one function: the hole drilled through it. if the hole gets drilled at all off, everything is outta whack.
so i seperated the two functions into two parts: a spacer block to control #2, and two angle iron bits on top to control #3. they each depend on the other, but now i have more control over the dummy axle's position.
i suppose this is all part of rudimentary jig/fixture design, but i've had no schooling so i'm playing it by ear.