the Carpentry Way: Tréteau VI                                                          

Tréteau VI

    
Still drawing....

Pffft! It's endless, or seems that way some days. I've had a few sessions of one step forward two back (my favorite game, after Sawing for Teens), however I am now complete through the stage of drawing the short side cross braces (the Saint André crosses) and the interior x-braces. All that remains to sort out now are the legs, and two of those are identical to one another, so I only need to draw developed views of three of them. So that's 'just' three parts to go and I'm done. Bwa-ha-hahahah - I'm not going to make any assumptions about smooth sailing however, as I seem to find innumerable ways to make mistakes in the drawing process and things never seem to go so easy-peasey as they first appear.

It does make it a little more troublesome that I use SketchUp in decimal inch formal, to 0.000000" accuracy. This means that when certain dimensions are off a teeny bit it can be a real hair-puller finding out what has caused the discrepancy. This does help me be absolutely rigorous in the drawing technique however. The software has a few quirks in it and crashes once in a while, even though I have the latest version downloaded. Otherwise, I find the mistakes I am so often making present me with lot of additional opportunities to draw the same parts over and over again.

Take the legs which are rotated 45˚ to the plan. While working on developing the views of the short side braces, I found a little discrepancy in a pair of lines that should have connected, but did not, missing by a few thousandths. That may sound irrelevant, and it most respects it IS, but it did mean something was wrong in the drawing, and in some cases SketchUp won't close a face up into a tidy plane if there is a small discrepancy like that - so I needed to dig into it. I tried re-drawing a few times, to no avail, and after puzzling it out a little while longer, I realized that logically the problem had to lie somehow with the legs. I checked the legs, which are supposed to be 2" wide, and found that both were ever so slightly wider at the back - at 2.000439" or something absurd like that. Enough to cause the beak-like cut on the end of the short brace to have edge lines not quite matching up with the plan development. That meant though that the legs needed to be re-drawn. In trying to redraw the legs, SketchUp got all buggy on me and wouldn't cooperate at all, so I had to start a new drawing. At least I was able to cut and paste quite a bit from the previous one into the new, and the legs were drawable on the new sheet.

I have developed the views of all four short side braces- I have figured the technique out enough now that I can draw both the leg and the sections of post which surround it, as in this example:


In the back ground you can see the two slices of post section. These weren't chopped out of the existing posts on the 3D rendering of the entire sawhorse, but developed from the 2D plan, like the brace.

The section of drawing which pertains to the development of the short side braces looks like this:


Actually, this is one side - on the other end of the tréteau plan and elevation views I have a mirror-image drawing of the same development, different only in respect to the generation of lines from one of the legs.

All four braces, now developed on all four sides into 3D from from the 2D, were rotated into the orientation they needed to be in the sawhorse, and 'tried' for fit. This way I could confirm the 2D drawing method was producing an accurate part. Then the 4 pieces were dimensioned and grouped in a separate area of the drawing so I could easily refer to them for the layout on the wood:


Of the four, the one at the bottom right of the picture has a pretty easy lower tenon to cut, as does the upper tenon on the right side, bottom - the shoulder is simply 90˚ across the face. To compensate for that however, there is the tenon and barbe (= "beard") found at the lower end of the top left brace - bleedin' diabolical!:


The barbe on that unit only about 1/4" thick at the root end and tapers to a fare thee well. It will be a fun one.

Today I had more vexations with Sketchup, but in the end managed to complete the drawing of an interior x-brace. Now, one thing about this entire process is that I have no one to teach me, just the text, so I don't always proceed in the originally intended order. Or in a logical order for that matter - "fools rush in where angels fear to tread" as the cliché goes.

In many cases, the drawing proceeds by determining a slope or dimension in one view, transferring it to another view to produce something else, and then often that development allows you to return to where you started with more information, thus allowing things to proceed further. Back and forth you go, dazed and confused for the most part. These interior x-braces are a case in point, and further demonstration of the fact that I am essentially stumbling around in the dark as I try to decipher the book and the methods it shows. And it does show you what you need to know - the trouble is recognizing that when you see it! Not so easy.

In that case of the interior x-braces, which tie the long side braces together, I had already produced them in the 3D drawing so I thought I had them pretty much licked. Ah, nope. I was having all sorts of problems getting the lines to tie up as I thought they ought to, and have pulled the 3D interior brace assembly out of the model and placed in on the plan to see if I could make sense of it. Things still weren't adding up and I was most perplexed. Then I noticed, through performing a bunch of checks, that while I had indeed drawn the interior braces, I had misunderstood the progression of step to develop them and had in fact drawn braces which were parallelogram in cross section. It was funny how I hadn't noticed all this time, even when I laid the assembly down on the drawing. Anyhow, once I saw that issue, I was forced to re-examine a number of assumptions about the text drawing and ba-ding! a light went on for me and I suddenly had a bunch more insight about the drawing. Struggle struggle struggle, and down a hundred wrong paths, but in the end persevering leads to those 'a-ha' moments often enough. Often enough to keep me going in this demented pursuit anyhow.

At last a couple of curious lines on the drawing, which I had long puzzled over and never understood, were now very clear in purpose. Like I said, everything is there to be seen on the drawing, even with all the little mistakes present, and in time it will reveal itself if you keep at it.

Here's the completed development of one of the interior x-braces - all four are identical so I only needed to develop one:


The tenon on the lower end of that puppy looks a bit troublesome, but not so bad as it was looking when the piece was a parallelogram.

All for today- the end of the drawing stage is nigh. Stay tuned. --> Go to part VII

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