pjfl59

Hello,

I searched - if there is a post or thread please post the link, thank you.

Can some one post or explain one or two clear examples of how the data in the body checking dimensions section of the manual is used?

I'm referring to the pages that show the car on a grid from the side view with all kinds of data like FOD, Line A,B,C etc etc.

For example, the very first line... no 1, body line h, c line 21.17, o line fod -40, height 21.69

I'm putting a car back together and it would be helpful to have this data in a form that I understand.

Thank you

Greg Hollowaty

What year was your body manufactured?

Vettrocious

Think of those grids as three dimensional, not two. The lines of the body move in three dimensions and the side view and top view of those grids combine to describe where a given line is in 3d space at any time.

pjfl59

I'm putting together a roadster 65 from many pieces.

pjfl59

OK Thank you. So knowing that, lets say I want the simple dimension for a roadster door opening.

End of front fender lip (basically where it bonds to the A pillar glass) to beginning of rear 1/4 lip (where it bonds to b pillar glass). Or, imagine your inserting a tape measure tab into the front door gap, and reading it and the rear door gap.

Explain to me how to calculate that off that grid. I can post it if needed.

Thanks!

Vettrocious

I did it once to locate some side emblems. Its not easy and I was once a GM body designer who worked with that grid daily.

My suggestion is to set up reference planes. A very flat floor can be one, if you locate the bottom of both rockers exactly parallel to it at an accurately measured height. Since the bottom of the rockers are parallel to the horizontal lines of the grid, you now can measure any location relative to the floor and know where it is on the grid.

Similarly, two pieces of plywood can be set up vertically, one in front of the car, the other beside it. Once you locate one known point on the body relative to those two planes (ie: boards) you can then measure to the plywood and do the math.

John BX NY

In the analog days and even now any point on a vehicle exists in an X,Y,Z reference space . X=fore/aft, Y=in/out, Z=up/down. FOD stands for a reference point "front of dash" ahead of the dash panel. Back then it was inches today it's millimeters.
Measurements were taken on check fixtures and surface plates. Later it was coordinate measurement machines and laser online body measuring. Using these reference points from the AIM outside of a gage or other measurement system is nearly impossible.

Vettrocious

Not really that hard, if you know what you’re doing, just time consuming and very exacting.

Vettrocious

Hockey references aside, I might add that the surface plates GM used back in the day had very fine lines etched onto them, whereas the drawings in the AIM have lines about a hundred times as thick. Doesn’t lend itself to accurate measurements