Friday, July 15, 2016

La Menuiserie Study (I)

Menuiserie is a term which translates into English as 'joiner's work', an almost meaningless term in the US these days, or as (finish) carpentry, or cabinetmaking, and furniture making. Like finish carpentry compares to rough carpentry, menuiserie compares to charpente. In charpente there is some joinery, but a lot of the work is spiked together, and timbers are generally not backed to conform to a plane but are rotated to present one face to the plane and leave the other one out of plane. In menuiserie, the timbers are joined and are shaped to conform properly to the planes they meet or define, and in this respect menuiserie shares a commonality with Japanese carpentry. To say that menuiserie is simply cabinetmaking or carpentry is a little misleading in english, given the types of work suggested by those terms these days. Menuiserie overlaps a number of areas of woodwork and is probably best understood as joiner's work - highly finished framed and joined structures, including furniture, built-ins, interior millwork, doors and windows.

One of the classic texts in menuiserie is L'Enseignement Professionel Du Menuisier, by Léon Jamin, dating from the mid-1800's. Comprising 3 volumes, it remains on my wish list. What I do have as a reference on hand is a volume from an encyclopedia on the topic, put out by Les Compagnons Du Devoirs, entitled La Menuiserie. Volume 3 comprises a text book, of large format, and a separate folio of plates:


I've had this book for some time, and yet hadn't made a dedicated study of the material. With a newborn, I now find myself at home a lot more, and with the occasional hour here and there to spend as I might like. So, when not trying to catch up on sleep I have delved in to this modern text, starting at page 1 and drawing every exercise in the order they are presented.  La Menuiserie presents a fairly systematic path through the material, beginning with basic geometry exercises like drawing parallel lines, drawing perpendicular lines, triangles, angles, polygons, etc. Thought that material fas already familiar to me, I drew the examples, using SketchUp instead of paper, compass, etc.

From the most basic stuff, La Menuiserie moves into drawings of ovals and various curves, then to ellipses, including a cool method that I had also noticed previously in my Mazerolle text but had never explored:


It's a very easy-to-remember and accurate method to produce ellipses, and if anyone is interested I'd be happy to show how to do it step by step.

After ellipses the study moves to curves developed on slopes, like this one for example:


An application for this sort of thing would be laying out a domed roof underneath a pent roof - as the following example on the right shows:


Next the text deals with drawing the line of the 'policeman's hat' (chapeaux de gendarme) - here are two methods:


Next, the volume deals with spirals of various types:


Archimedean spiral on top, two-point spiral below.

Spirals on three points, four points, and six:


And extension on the theme of spirals are volutes. Here are four different types:


All of the above exercises are merely a preamble to the sections to come. The first part of the more involved study is titled Éléments de géométrie dans l'espace. In that chapter the exploration commences with a consideration of the basics of descriptive geometry,  orthogonal planes and the forms of the basic solids like prisms, cylinders, cones, pyramids, and so forth. At this juncture, the supplemental box of plates still hasn't been cracked yet.

There are a series of exercises to develop the surfaces of cones, and then truncated cones. 

Here's the development of a right cone with sloped truncation:


And this is the development of an oblique cone with sloped truncation:


Notice the characteristic shapes of the developed surfaces in the above two examples? With a right cone, an oblique cut of the cone produces a developed surface which has a horseshoe-shaped cut. With an oblique (or scalene) cone similarly cut, the developed surface has an 'M'-shaped cut line.

Now, as I worked my way through the above two exercises, there would be times when I would refer to the text, which of course is in French. At least it is not 19th century French like the Mazerolle book, but it still exercises me a bit to translate. I did, after all, flunk out of French 11 in high school. At one point I decided to look on the web to see what else I might find on the same topic of developing conical surfaces -perhaps there were other methods worth looking at - and I came across a French Wikibooks page on the topic, titled Traçage en chaudronnerie et tuyauterie, which I translate as 'Templates for Boiler and Pipe Work'. Developing surfaces like cones and cylinders is a standard sort of thing for fabrication of pipes and ducts.

Here's what that page showed for the development of a right cone with an oblique truncation:




The developed surface shown was contradicting the La Menuiserie text I had, with an 'M'-shaped development from a right cone instead of the horseshoe-shaped development. Hmmm....

Well, only one of these developments could be correct (or neither - or possibly both somehow). In SketchUp there is no convenient tool with which to unfold curved surfaces flat, so I drew a scalene polygonal cone and unfolded it (which was a tedious task) to see what shape was produced:


There we have it: the 'M'-shaped cut line associates to the scalene cone, as my text showed. That French Wikibook page was incorrect. I went into the history for that web page, and note it has been up for 6 years, the diagrams edited for clarity at different times, and it has apparently been in error on that development the whole time. Funny how things go like that. I hope it hasn't confused too many boilermakers or pipe-fitters in the interim. Someone must have mixed up parts of two sketches, perhaps?

EDIT: A reader pointed out that the shape of the cut line on the developed surface is related to where the cone is cut to be unfolded (i.e., at the longest or shortest length), so my above conclusion about that Wikibook page is in fact erroneous. If I had chosen to unfold the above cone at a different point, I would have concluded differently.

I'll continue this account in some further posts. A series begins. Thanks for visiting the Carpentry Way. Part II is next.

8 comments:

  1. Dear Chris,
    The shape of the development depends on where you cut the cone to unfold it.
    In your first right cone, the cut is along the longest line. On the wiki page, the cut is on the contrary on the shortest line. On the oblique cone, the cut is along the shortest line also.
    Sylvain

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    Replies
    1. Sylvain,

      Ahh - that makes good sense. Clears up a misunderstanding I had formed and give me an insight - thanks! I have amended the above post to reflect this information.

      ~C

      Delete
  2. This takes me back. When I was training as a mechanical engineer, we were still trained as draftsmen on actual drawing tables. We learned lots of tricks like these. Given that engineering students use CAD software from day one now, I doubt if these skills are still being taught.

    Which is kind of a pity. These skills are still useful to me because I often have to translate 3D geometry into 2D patterns for cutting fiberglass and carbon fiber cloth. And our available CAD software is of little help there.

    But instead of a drawing program nowadays I tend to use a programming language called
    "asymptote" for tasks like this. Just today I made an asymptote program for drawing segments of a development of a truncated cone.

    ReplyDelete
    Replies
    1. Roland,

      thanks for the comment!

      My point of view about studying such material, despite having the CAD on hand, is to learn a skill which I can execute in the field (or, more likely, the shop) with the standard layout tools. The 3D capability helps me understand the 2D better, and check that the 2D is correct when I am unsure otherwise.

      I'll check out that link - thanks!

      ~C

      Delete
  3. For what it is worth, I've found copies of the first two volumes freely available to download, no luck for the third though:
    http://gallica.bnf.fr/ark:/12148/bpt6k6566068h/
    http://gallica.bnf.fr/ark:/12148/bpt6k6565447d/

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    Replies
    1. Philip,

      most kind of you to share that and i'm sure some readers here will appreciate it greatly.

      There are a good number of carpentry texts now available online, however I have found that in those cases where the text and the plates are separate, it seems that only the text sections are digitized, especially if the plates are large format. And that's too bad.

      Indeed, the first volume of Jamin's work linked in your comment, after looking through 500 pages of text and seeing that there are some illustrations included on various pages, but the 60 Plates the text is describing are missing entirely from the digitized copy.

      The second link shows plates on other topics like stairs, but these are not the plates mentioned in volume 1. The text seems to be entirely missing from that digitization. And, alas, the digitized copy does not allow much in the way of zooming in, so details are near-impossible to make out.

      I guess I'll have to obtain the books....

      Thanks again for the links though, as it does give some idea what is inside those volumes.

      ~C

      Delete
  4. Are there any similar books written in English that could help one studying this topic? Chris.

    ReplyDelete
    Replies
    1. Chris,

      thanks for the question. I don't know of a book exactly like La Menuiserie in english, however James Newlands' work "The Carpenter's Assistant" looks at the same sort of topics and has some overlap in terms of subject matter.

      ~C

      Delete

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