Wednesday, February 3, 2010

Tréteau XVI

The work on layout for the mortises on the two rotated legs continues. The French call such legs 'faces aplomb', which refers to the fact that the side faces of the legs, like a hip rafter, are plumb to the ground. Two of the legs in this sawhorse are thus configured, and they are located on diagonally-opposite corners. Conveniently, they are identical in every respect so sorting out the layout issues on one serves for both. The other two legs on the 'horse however are each unique.

Sorting out the layout took quite a while - here is an overview of the lines laid down just for this one leg - one the 'floor' is the same leg, as constructed from the 2D development lines:


In the last installment I completed the layout of the through mortise for the long side brace. What remained were the mortises for the short side braces - the lower of which is a blind oblique mortise and I will have to take some special measures to effect the cut out:


I don't believe that the original by Mazerolle had a mortise and tenon connection at the lower position - it was probably spiked in place. I notice that a lot of these sorts of splayed structures with interconnecting braces of various arrangements tend to employ nails more often than not. Probably due to assembly issues or the difficulty inherent in cutting certain kinds of mortises. I'm going to try and do it purely with joinery, though it will hardly be convenient. And I still harbour worries about how the piece will assemble....

Speaking of further examples of this sort of splayed-leg work in the French tradition, I came across some pictures recently of various carpentry masterpieces, which invariably feature this sort of construction at the base:


The next two are similar in some respects:


A little less overwhelming complexity with this one, the base of which is similar to a cross (no pun intended) between the tréteau I'm building here in this thread and the trépied établi (three-legged joiner's bench):


And one more:

I really wish I could have seen that exhibit of carpentry masterpieces, which occurred in 2002. Did I ever mention I really like turrets and domes?

Anyway, with mine, after the layout was gone over again in detail, it was time to mark out on the wood for those two faces aplomb legs. Here are two legs side by side showing the blind mortise openings:


The dotted line indicates the rear portion of the mortise where the slope from the face terminates.

The is the mortise for the upper tenon, which is a through tenon, albeit compound-angled and tapered:


Then tenon enters at the lower part of the photo, and emerges on the adjacent face above. It's not too acutely angled, so cut out should be relatively straightforward. For the lower blind mortise, I will be making a special guide jig to aid in cutting and paring.

More to come - thanks for your visit today. --> Go to post XVII

2 comments:

  1. I keep wondering how you will assembly the whole thing in the end. I think will be a bit of a challenge.

    ReplyDelete
  2. Charlie,

    it's a splayed structure, so the assembly will be a gradual one, tightening up section by section in a series of rounds. The x-braces of course are pre-assembled units within the structure.

    I'm a bit uncertain about the assembly myself, as I have had to make guesses about how much to diminish various tenons in relation to assembly directions. Now, I am planning to wedge many of the tenons, so the opening up of the various mortises at their outlets will help the issue I imagine. I guess we'll have to see how it goes - hopefully if I have miscalculated anything it won't be an irrecoverable situation, as each piece in this puzzle requires lots of hours to make.

    Wish me luck at least!

    ~Chris

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