Osaka Castle Gate Repair

[Stanley Covington]

This picture is of a repair made to one of the large columns supporting the gate to the Osaka Castle in Osaka Japan. I am not sure of the size, but it is in excess of 2 feet square. The base of the column was replaced at some point with new wood using the interesting connection shown. The same dovetail shape appears on the backside of the column.

The solution can be seen in the sketch in the following post. Try to figure it out before you look at the next post.

Stan

[Stanley Covington]

The solution to the connection can be seen in the attached sketch.

Stan

[Metod Alif]

Stanley,
Thanks for sharing. A nice example of Japanese joinery.
I would like to know of examples how such 'large scale' joinery can be utilized in furniture (small scale') situation. Getting good at such joinery would mean high level skills - in laying out and execution.
Best wishes,
Metod

[Harlan Barnhart]

What would be the purpose of the "button"?

[Stanley Covington]

Here are links to a couple of pages with more pics.

The square plug at the top of the dovetail hides the end of a bolt connecting the beam to the column.

http://blogs.yahoo.co.jp/warenabee/57225499.html

http://galleryimpossible.com/outemontugite.htm

Stan

[Stanley Covington]

For those of you that enjoy strange joints I found a better diagram with ratio dimensions.

Stan

[Peter Pedisich]

Brilliant stuff, thanks for sharing. If I was 20 again (1985!) I'd change my major and study these techniques.

[Pat Barry]

How exactly does it go together? It looks impossible based on those drawings

[Andrae Covington]

How exactly does it go together? It looks impossible based on those drawings

This is cool! Thanks Stanley for sharing. Here's a page with some pics of a small folded-paper version (http://sysplan.nams.kyushu-u.ac.jp/gen/hobby/puzzle/Joint/index.html) that might make it easier to see how it slides in place.

[Pat Barry]

Oh, I see now. Didn't notice the dovetail orientation wasn't exactly the same for each side. Thats very crafty

[David Wong]

Here are three pictures of the joint that I took at the Takenaka Carpentry Museum (http://www.dougukan.jp/contents-en/), in Kobe. The third picture shows the joint sliding together.

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[Kesh Ikuma]

This is pretty cool. For those of you who can't read Japanese, the writeup in Stan's links says that this joint has been a mystery for years. A newspaper featured this joinery in 1979 as a mystery joinery. They received a number of "solutions" from readers and ran a followup article the next day to share them to the readers. The actual construction of the joint was not revealed until Dec. 1983 when they took an X-ray photo of the joint. Apparently, there are at least 2 alternative ways to cut the joinery and get the same outside look.

FYI, I've read somewhere that Japanese carpenters are known to use a tricky joinery for a handful places in their job to passive-aggressively show off their skill (while using simpler joinery for the majority of joints).

[Bryan Ericson]

A while back, I found a scan of a book called "Wood Joints in Classical Japanese Architecture". It was linked to from a Japanese woodworking forum, and you can read a copy here: http://www.scribd.com/doc/37922205/Wood-Joints-in-Classical-Japanese-Architecture (I don't think this is an illegal link, but if it is, a moderator can edit this post). The book is amazing - it analyzes dozens of joints that are similar in nature to the joint above, and the authors then go on to analyze the joint's strength and typical failure modes. It's well worth your time to check out the link and read the book, even if you're not particularly interested in Japanese joinery.

[Jim Matthews]

I can't decide if it's a Mensa intake challenge puzzle or one of those "Betcha can't unscrew this" noob traps at a bar.

I get the feeling somebody really clever had way too much time on their hands.
Perhaps it was a way to slow people down at the gate, so the guards had more time to check ID?

[Stanley Covington]

This is cool! Thanks Stanley for sharing. Here's a page with some pics of a small folded-paper version (http://sysplan.nams.kyushu-u.ac.jp/gen/hobby/puzzle/Joint/index.html) that might make it easier to see how it slides in place.

Thanks, Andrae. The paper model makes it very clear. Good to hear from another Covington!

Stan

[Stanley Covington]

I can't decide if it's a Mensa intake challenge puzzle or one of those "Betcha can't unscrew this" noob traps at a bar.

I get the feeling somebody really clever had way too much time on their hands.
Perhaps it was a way to slow people down at the gate, so the guards had more time to check ID?

Don't give TSA any ideas! I spend enough time waiting in line at airport security as it is without having to figure out puzzles.:D

[David Weaver]

It's definitely cool. Joints like that for the sake of intellectual satisfaction or curiosity of the maker are nifty.

[Sam Murdoch]

What would be the purpose of the "button"?

I've been wondering the same thing. Seems like a superfluous detail. There is no evidence of a button in the second sketch.
OK - tell me (and Harlan) I am prepared to be embarrassed :confused:.

[Stanley Covington]

Here are few more variations on the theme I found on the web.

The first one is a from the Ichijoji Temple and is called a Benkei Komatsunagi Joint.

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The next one is called a Double Kama Joint. I don't know if there are any tricks involved in assembly.
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I don't know what the next one is called, a kama tsugi of some sort obviously, but it looks like a holy bitch to fit.

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This final one is a joint in the shape of a plum blossom at a column base (probably part of a repair) at the Kitano Tenmangu Shrine in Kyoto.

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[Stanley Covington]

Here are three pictures of the joint that I took at the Takenaka Carpentry Museum (http://www.dougukan.jp/contents-en/), in Kobe. The third picture shows the joint sliding together.

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Thanks, David.

I see a hand in the pic. Were you able to play with the joint? If so, did it strike you as a joint that had practical strength?

Stan

[David Wong]

I see a hand in the pic. Were you able to play with the joint? If so, did it strike you as a joint that had practical strength?

Stan

From what I remember, the joint was quite loose - either by design, or from all the people playing with it. There was very little strength in any orientation other than vertical. Once vertical, the joint was very stable, but I did not try to twist it apart.

The museum is a neat place for woodworkers. They had several other models on display. Here is a slight variation of one of the other scarf joints you showed...

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[Stanley Covington]

From what I remember, the joint was quite loose - either by design, or from all the people playing with it. There was very little strength in any orientation other than vertical. Once vertical, the joint was very stable, but I did not try to twist it apart.

The museum is a neat place for woodworkers. They had several other models on display. Here is a slight variation of one of the other scarf joints you showed...

David:

I have always wanted to go to Takenaka's museum in Kobe, but the chance has never presented itself, and besides, Takenaka is most definitely the enemy in my line of work.

Thanks for the pics. Excellent.

Stan

[Zach Dillinger]

What would be the purpose of the "button"?

Not being a student of Japanese joinery, I can only speculate, but I suspect the "button" is really a wedge. The joint would have to be pretty loose in the Z axis to allow it to sneak together. Driving a wedge in that spot would push the timbers apart until the dovetails prevent the top piece from rising any further. Does that make sense?

[Sam Takeuchi]

Not being a student of Japanese joinery, I can only speculate, but I suspect the "button" is really a wedge. The joint would have to be pretty loose in the Z axis to allow it to sneak together. Driving a wedge in that spot would push the timbers apart until the dovetails prevent the top piece from rising any further. Does that make sense?


It's already been answered. It's just a plug hiding a big bolt inside.

[Zach Dillinger]

It's already been answered. It's just a plug hiding a big bolt inside.

I didn't see a post that answered this question. My apologies for missing it!

[Sam Takeuchi]

I didn't see a post that answered this question. My apologies for missing it!

Sorry Zach, I didn't mean to appear gruff and unfriendly. That was not my intention. My apologies.

[Zach Dillinger]

Sorry Zach, I didn't mean to appear gruff and unfriendly. That was not my intention. My apologies.

I didn't take it that way. No worries.

[Sam Murdoch]

I didn't see a post that answered this question. My apologies for missing it!


Same here, I asked after the question was answered too. Just didn't see the answer even though I was looking - er, I guess - scanning. Sorry.