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Transportation Alterations
October 5, 2023
In the old days, before 3-D CAD, the task of turning the study layout into detail parts drawings was delegated to the “drafting department.” As an apprentice drafter, you might be tasked with drawing end covers, seal retainers, spacers, keys, inspection covers, and other minor items. Your supervisor would come over to your workstation with a copy of the layout and note which parts on it were “yours.”
On a section view very little would be seen of some of these parts; in the case of keys, for example, they might not appear at all. How many bolts, what size bolts, and the “fits” on a seal retainer would be controlled by the company’s “book of knowledge.” There would be reference charts, lists of purchased part numbers, and usually reference drawings for the newbie to mimic.
As you gained experience, your assignments would change to more complex parts. That “book of knowledge” was always close at hand and you never got too far away from the representations shown in the “similar to” drawings your boss would point you towards.
Only designers were allowed to be “creative,” and even they had to make sure the results fit the layout. Very senior team members served as “checkers” to critique each drawing and make sure all the dimensions on it were compatible with the other components. Tolerance “stack-ups” were religiously noted in the margins of the study layout. The goal was “no reworks at assembly” and it took teamwork and discipline to do that.
At this point you might be expecting an old curmudgeon like me to start ranting about the loss of this time-proven methodology. Sorry to disappoint you, but I greatly admire the ability to render a complex mechanism in 3-D and explode it into individual components with a few keystrokes. There was nothing fun about needing dozens of people to complete even a relatively simple design. Not everyone in the drafting room saw things the same way; few of them had the commitment needed to make world class products.
Today’s methodology eliminates many of the “middle men” but also reduces the number of eyes on the design. The traditional “garbage in, garbage out” problem of all computer programs is always present. More about that next time.
