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Discussion Starter #1
Hello. I want to make some Meditation Benches. One useful posture for meditation uses a special bench. Using this bench, it is possible to sit for many hours with minimal distraction from physical pain. Here is an image that shows what this kind of bench looks like and how it works with the anatomy of our human bodies.

http://www.mro.org/zmm/teachings/images/zazen/benchside.jpg

One problem with these benches is that when the human moves from side to side, the "vertical boards" are subjected to opposing forces; the floor moving one way and the human butt moving the other way. This causes them to tilt from vertical to diagonal. However, the "seat board" stays horizontal. This means that the two joints are no longer perpendicular, but are being stressed rotationally, which they are not usually designed to do.

Usually they feel solid enough, but I want to design a joint that would be VERY druable yet economical. It has to allow space for the legs under the "seat board" and between the "leg boards". Here is a design I came up with. I'm new to woodworking. I got some books from the library, and I've done about 2 very basic woodworking projects in my entire life. Can you give me advice? Will this joint be durable and economical? Will the screws work as shown? Is the grain orientation shown the best option?



To join the "vertical boards" to the "seat board" I was thinking of using dowel-pegs.

Thanks for reading,
-Diego Hemken
 

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I don't want to use man-made wood. I would prefer to use just boards. I don't know much about which wood would be best. Hardwood would be better but more expensive. If there is some sort of Mediumwood, I would like to use that. How do I allow for movement? I think the place where movement might be problematic is the screws holding the joint together. With shrinkage or expansion, the joint might loosen up or tighten up. But I think that this joint should hold up well to that to some degree, because the stress would be a shearing force on the screw, which is metal. Dowel-pegs should be enough to keep the "vertical boards" aligned to the "seat board" and the main force exerted on the bench is gravity on the vertical grain, which is very stable.

Can you tell me where this design is weak and how to make it stronger?
 

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Scotty D
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For solid wood, Poplar would hold up fairly well, and be one of the cheaper hardwoods.

Screws installed through slotted holes in your diagonal braces, into the top will allow it to expand/contract with seasonal changes.

I would also add a tenon to the top of your vertical, that could float inside a longer mortise in bottom of seat board (google... "bread board end")

Multiple dowels will not let the seat move and it would probably crack/split over time. :smile:
 

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Discussion Starter #5
Well I'm considering making dozens of them so I want to minimize the complexity of manufacture.

The screws in this design will be going freely through one board and threading into another board, clamping the two boards together. If I drill the through-hole a little oversized, and counterbore it a little oversized, would this accommodate warping sufficiently?

If I made the dowel holes in the "seat board" oblong, would this be sufficient?
 

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The way your diagram shows the grain direction should mean minimal problems with movement.
Biscuits or splines would be quick and solid.
Pocket screws on the underneath joints might work. I think I would make the braces 1/2 the width to cut down on top weight and possibly look a bit lighter. It would also save on wood.
A shallow dado cut in the bottom for the vertical legs would make the line up of the legs easy and be a bit more solid?
Wood choice:what are they being used for. If camp dining then any good softwood you can find. If they are to be more dressy then an attractive hardwood is worth your work time. Thickness of the wood can change the look, light or heavy
Enough babbling.
 

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Really underground garage
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Probably shouldn't reply.....sigh,oh well

This is JMO.....anybody can make "things" more complicated.You just keep chasing an idea or plan...adding whatever it takes to accomplish necessary safety(in this case)and durability.

The more simple the design is,the more intense the study it takes to accomplish the task.Because you have less ways to "cheat".It seems it should be real simple.....and it is,but you have to understand some basic principals of woods behavior and also some rather complicated engineering ideas.......IOWs you don't have to look at why triangulation works because there ain't none(not directed at OP)....you'd need a thorough understanding of tennon strengths/weakness's.


Google 5 board benches......read with interest,read with an open mind.What pre-dates the 5 bd?Good luck,BW
 
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