On the Reverse Engineering of Big Old Machines

(Well, mostly big.)

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When you want to know how things really work, study them when they're coming apart. - William Gibson. Zero History.

1. Introduction

"Reverse Engineering" is an important (if controversial [1]) field today, but it seems mostly to be practiced by industry for profit - with corresponding access to fancy tools. I've found very little information about reverse engineering the kind of old machinery I like (Linotypes, typecasters, etc.) using tools commonly available in the home hobby machine shop. I haven't even found much information on the underlying principles which might illuminate such an undertaking. It seems that actually attempting to rebuild the 19th century industrial base in the home workshop is a relatively rare pastime.

See also:

[IMPORTANT NOTE: Actually, there isn't much here yet. It's a difficult subject that hasn't really been addressed in any literature. I'm still trying to figure it out. As I learn stuff, I'll record it here - but mostly it isn't here yet.]

2. General Thoughts

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Intellectual Habits

On becoming an engineer of 1886. Documenting why you think you know something. Admit that you don't know.

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Levels and Kinds of Models

3. Background Knowledge

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Detail Practices

[NOT DONE] Today a young person can go through life without ever being exposed to an actual mechanical device. (It is significant that even well-educated and well-intentioned 21st century persons such as the founders of the Open Hardware Association chose for their logo a "gear" with teeth which could never work.) It's useful, then, to understand beforehand some of the no-longer familiar constructional details of old machinery.

[NOT DONE] The threaded stud and nut. Locating by dowels and taper pins. Cams working against springs (e.g., in the Linotype; counterexamples in the Thompson).

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Estimating Your Uncertainty

An ad hoc scale.

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Historical Fits

[NOT DONE] (No - not any of the various jokes which might be made upon such a title.) How have standard practices varied over the years for default tolerances for various kinds of fits between machine parts? If you have to make a guess when reverse-engineering a fit, it should be based on the practices of the original builder, not a modern handbook.

4. Topics

"The only way by which the patternmaker can definitely know what he is to make is by a drawing or sketch. Sometimes an old broken casting is placed on his bench and he is told to make a pattern from it. The fact is that one of the worst things to make a pattern from is an old casting. There are no centers or figure to work to, but the pattern-maker has to measure the casting with a common rule and do more or less guessing to obtain the dimensions. Even then, when the he has the pattern made, he is not absolutely sure that he has the thing exact." (Willard, G. H. Pattern-Making. (Chicago: Popular Mechanics Company, 1910): pp. 100-101.)

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The single biggest difficulty encountered when reverse engineering old machine parts is the tolerancing of dimensions. The core of the problem is that there are actually two kinds of tolerances involved, and they aren't easily reconcilable.

5. Case Studies

These are some of my own shop projects which, to some greater or lesser degree, have involved the reverse engineering of old machinery. (These are links over to other Notebooks at CircuitousRoot which deal with these particular machines.)

[NOTE: As of 2015, many of these projects are in their very early stages. If a link is broken, that's because the thing it links to isn't ready for publication yet.]

Typecasting & Linecasting Machinery:

Machine Tools:

Technical Horology:

6. Bibliography

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7. Notes

1. As a quick note to put the matter aside: Reverse engineering today is a field fraught with issues from so-called "intellectual property." This is regrettable, since modern IP law is nothing more than a land grab of the mind by the powerful. Despite a well-funded mythology to the contrary, intellectual property, from its origins in early copyright and patents to the present, has always been the enemy of the little guy (if you believe otherwise, you probably don't even remember taking the blue pill). Fortunately, the machines that I will be reverse engineering in my own hobby work are all antique. IP issues are no longer relevant to them.