Wednesday, March 25, 2015

Gateway (76)

Post 76 in an ongoing series describing the design and construction of a kabukimon, a type of Japanese gate. This is a project for the Museum of Fine Arts in Boston. Post 1 in this series can be found here if you'd like to start at the beginning. Each post links to the next at the bottom of the page. Recent installments also to be found in the 'Blog archive' index to the right of the page.

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The last two days have been a continuation of the push to complete all the mark out and fitting associated to the copper parts, so that I could get them in for powder coating in time. Today especially was go-go-go, like some sort of race.

To that end, the kabuki/magusa assembly was joined to the main posts, a tight squeeze in my shop but do-able. A 1-ton ratchet strap and a 1-ton come-along were sufficiently persuasive to draw the parts together, with additional coaxing, I might add, coming in the form of a 15-lb. sledgehammer.:


The joints drew up fairly well-  here's the right hand side post, inside face intersection:


And the left hand side:


The left hand side joint is a hair open in the above view - though the photo doesn't show that especially well - and I will need to flatten the post face a little bit with the plane and then all should be tickety-boo. The point of assembling the main posts and cross-members was to check the fits of the joints and to mark out the points where the sheet copper top on the beam meets the post faces. I was pleased to see that the front face joint lines are nice and tight.

I decided not to assemble to nose pieces onto this assembly. I have already fit them onto the kabuki, and am fairly sure they will go through the post. I was concerned that if I put the works together then I might have difficulty getting one side apart again. The joints are snug and there is a fair amount of surface area involved, so I judged that it was better not to risk things getting stuck when it isn't absolutely necessary. I'll do an assembly of the nose pieces onto the post tomorrow to check those fits.

Speaking of the nose pieces, I fitted the copper onto those:


A view from the side-  this copper work consists of four parts, one wraps around the timber, two are clips for the top, one is the slightly pyramidal end grain cover, and then there is the top panel, which overhangs slightly on three sides:


The main cap portion is let into the post's side and underside faces with a dado.

Here is a look at those two aforementioned clips - these will be nailed onto the timber:


Some surfaces will also be receiving a layer of ice and water shield.

While the main frame was assembled, I also fitted the main doors so I could be sure they fit and then could mark out for the hinges. These hinges are quite tricky to fit:


The lower hinge pin slightly interferes with the copper sheet foot, however there is an escutcheon yet to be fitted as well. Given the hinge mortise, the mortise for placing the nut onto the threaded rod hold-down, and the nuki mortise above that, there wasn't a lot of real estate to play with. I wanted the sheet copper to be as tall as I could make it, and wanted to keep to the traditional pattern of rail/batten spacing on the door, so the hinges ended up where they ended up. I think the fact that the hinge escutcheon and, on the other face, the fixing pin escutcheon, overlap the copper slightly is not a significant negative. To have zero overlap would have meant reducing the height of the copper feet to 8" or so, at which point their usefulness in functional terms (protecting the lower end of the post from the weather) diminishes quite a bit.

Open sesame:


The doors were a 'dead nuts' fit in their opening, which was a relief. One of those things that keeps me up at nights sometimes is imagining that the doors were an inch or two wider or narrower than they are supposed to be.... I still have to plane the outer edges of the hanging stiles, and seeing how the doors fit together was helpful in figuring out exactly how I will need to tune those surfaces.

This afternoon the remaining copper work was delivered. I think the business gurus call it 'just in time delivery'  - whatever, I was glad it was done before the deadline. All good as far as the part quality too, though the fabricator was pushed hard by the difficulty of soldering the 4 post caps with silver solder, the high heat tending to easily warp the copper. It would have been much easier to use regular solder, however then I would have had to find a metal finisher who could chemically treat the copper black (as the powder coating process would melt regular solder), and I couldn't find companies in the Northeast who wanted to tackle that. Things you learn as you go....

Next, the main posts, now separated from the kabuki and magusa, had their upper faces rebated to fit their copper caps:


The cap slides on - getting these to fit well took a while longer than I expected, and lots of planing cross-grain:


Now you know why my kneecaps are always coated in sawdust. If the fit was too tight, I risked the copper getting stuck on there and being hard to remove. I really, really wanted to avoid that situation.

All the way on:


Looks tidy enough I hope:


Last task was the fitting of the copper caps to the kasagi. First, the kasagi were fitted to the main posts:


Then the copper 'roof' could be placed and the end scribed to the post face:


So, by the end of the day I had completed the copper-related tasks and shlepped the parts down to Springfield where the powder coating company is located. I have the work on 'rush' so they may have it done in a couple of days, three at the most. Their oven accepts parts up to 8' long, so I just squeeze in there with the kabuki ridge cap. Good to be lucky sometimes.

A myriad of minor tasks to be completed yet. I'll be revising my punch list this evening. I have 5 full days left to complete those tasks and package the parts for transport.

All for today- thanks for dropping by and hope to see you next time. Post 77 is up next.

12 comments:

  1. Hi Chris

    Silver soldering the copper is a far better solution that using normal soft solder, If you make gutters for the roof out of copper, these are traditionally riveted together because the soft solder can not withstand the movement of the copper as it warms up in the summer and cools down in the winter. But I am pretty sure that silver solder is capable of that.
    Judging by the looks of it, it sure seems as your copper smith knows what he/she is doing. It is really nice work.

    Being married to a physiotherapist, I am constantly reminded to lift properly and not strain my back etc. Since the gate parts look heavy on their own, I am convinced that they are even more awkward to lift while assembled. so please be careful when trying to get the gate out of the workshop.

    Brgds
    Jonas

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    1. Jonas,

      thanks for the comment!

      I'm plenty carful about lifting, and often ask for assistance from my shop neighbors when needing to lift/move heavy awkward things. I give them some of my homemade beer as compensation, so everyone is happy.

      I make a lot of use of levers and the fulcrum principle when lifting. The tricky thing with some of the project pieces is that they combine weight, awkward handling, and very little resistance to mechanical damage. I'm sure I've learned a lot on this project just in terms of handling such materials.

      ~C

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  2. Replies
    1. Me too! Dreaming about having a day or three to just putter around...

      ~C

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  3. With all the copper fitted so nicely, did you make an allowance for the powder coating? Or is that something that won't change the copper dimensions and alter the fit?

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    Replies
    1. Appreciate the question Ralph.

      The powder coating will add a small amount of thickness to the copper. For most of the parts in terms of how they fit the wood, that means that the folded seams which enter the kerfs will be a little tighter. I made those kerfs with enough room, and if the fit is a hair tight I can flatten the copper's folded seam a little. for the caps, I have asked the powder coaters to not put any paint on the inside of the parts. So, I do not anticipate any significant problems in that regard.

      ~C

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  4. Hi Chris,
    Why does the copper need to be coated? I like the natural greening process.
    Peace,
    Harlan Barnhart

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    Replies
    1. Harlan,

      it's not out of 'need' - I gave the museum the choice, and they wanted the replacement gate to adhere to the aesthetics of the old one, which had black metal support shoes and black copper work.

      I also prefer the raw copper being allowed to age naturally, and many japanese gates have raw copper on them, however I will say that the fact that it will be painted black drastically simplifies the fabrication, as the paint hides many flaws, and means I can handle the raw copper without gloves, as there is no concern of fingerprints appearing later.

      Appreciate the question.

      ~C

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  5. How thick is the copper? Is it thin enough to flex somewhat under hand pressure? If so, handling it without causing damage must be quite a challenge... If not, some of these pieces must be quite heavy...

    Amazing work as always. This series is so interesting, I fear I will go through a nasty withdrawal when the gate is completed.

    LD

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    Replies
    1. LD,

      the copper is thin and easily dents, which certainly does add to the handling challenge. The parts which were soldered are of a heavier gauge to better resist the heat during fabrication.

      Thanks for your comment.

      ~C

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  6. Hi Chris,

    I have questions regarding copper end caps and their relations with how to determine the dimensions of the wood pieces they are installed on that I can't seem to get my head around. Specifically, in this image:

    http://blog-imgs-61.fc2.com/t/e/b/tebori1/p1224.jpg

    In this image, we see a close up of a Yakuimon specifically at the junction between the main post and the Kabuki. The metal cap above the main post in this example is installed so as to allow a bit of it to project beyond the sides of the wooden posts. After studying the diagrams in Togashi's book, I observe that there is some proportions which are based on the distance between the interior side of the main posts.
    My first question is therefore does the carpenter need to compensate by resizing the main posts smaller so as to allow that distance (between the interior sides of the main posts) to be measured using the interior side of the metal caps atop the main posts? Or does the dimension of the main post remain unchanged?

    Also, at the end of the kabuki in the image, I observed the same phenomenon. Although in that image I can't see the end of the kabuki, my assumption is that the metal cap on that kabuki adds a wee bit of length due to the projection of the metal cap from the wooden surface. I understand that there are proportions that governs the length of the Kabuki. Therefore, my second question is whether the kabuki should be resized such that its length is shorter to account for the extra length added on by the metal cap?

    Although I have my own assumptions and that maybe the questions above don't have any real answers due to the fact that they are purely design related. However, I would like to hear the opinion of an experienced carpenter such as yourself regarding this matter.

    Thanks and keep up the great work. Your posts have been very inspirational.

    Frank

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    Replies
    1. Frank,

      if the choice is to use a copper cap atop a beam which has such thickness, then yes, the post would need to be sized down, or the beam sized up, so that there is a suitable reveal where the arris of the beam sits atop the copper. you change either post or beam dimension, or split the difference between the two parts. Or choose to use copper which does not have such edge thickness.

      As for proportioning the end of the kabuki (the length) relative to the rest of the structure, with that type of thick copper cap on the end I presume one would have to mark the end in terms of the end of the copper. It's a visual element after all. So, yes, the kabuki end would be a little bit shorter with such a cap fitted than otherwise.

      ~C

      Delete

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