Joint design

[simm1701]

Hi all,

I'm wondering if you can help me with a issue of joint design

I'm looking at building a four poster bed frame, with the aim of not having any end pieces, screws or bolts showing - the scale is quite large, I'm going for a medieval look.

My question is regards the joints of the horizontal beams to the vertical posts on the corners. The upright posts will be 200mm*200mm, the beams are 100mm*100mm

I intend to mortice a 65mm deep hole (the depth of my router) for the beams to sit in (the observant will notice that I'll need a 45 degree mitre 15mm in from the corner of each of the 2 beams)

Obviously the joint itself takes care of load bearing, my concern with holding it together for lateral forces.

I have 2 joints to come up with a solution for, the beams near the bottom, with go into the middle of the post (where the inside corner will be hidden by the matress), and the beams at the top which will have the top of the mortice open (and since it will be 2m from the ground, also not visible)

I also want to make this relatively easy to take apart and reassemble, so bolts are of preferance to screws.

My initial thoughts are for the lower joints:

2 furniture bolts from the middle of each beam to the inside corner of the post, obviously offset so they don't collide

The top joints:

A right angle plate sat on the top of the post, at the corner of the plate using furniture bolts into the wood of the post, on each of the arms of the plate the bolts would go into the beams. I was planning to use a tongue on the lower edge of this mortice to give it some hold against upwards force, though I don't expect that to occur through use.

Any thoughts on the above, problems, better ideas? (or let me know if you can't visualise what I'm describing and I'll see about knocking up a sketch)

Thanks

Simon

 

[oddsocks]

Simon - that's a hefty frame and I have been trying to think how I would do it (i have made a bed but used the woodfit BD271 in the link below, but your use of tenons prevents that).

For the bottom consider a wooden triangle, permanently fixed to one rail and then screwed or bolted to the right angled head/foot board once both tenon joints are fitted. You could also notch the upright to allow that triangle to assist in the load taking. For the top your suggestion makes sense, but with good show wood and discreet screws (this would have little load) it would also look good using the triangle

If you haven't made the frame yet, consider the beech ones on the woodfit link - I used these for a queensize matress (almost 6' square) - I made two 'single' frames reasting on a centre rail. The beech slates were the normal single length slightly shortened into the plastic fittings. Having previously had timber slats, this made a huge difference in comfort and keeps each half of the bed 'independantly sprung'. They are dearer than wooden slats but worth it.

http://www.woodfit.com/advanced_sea...&sid=f1e5c7d2bda8d46885c17427b77d9668&x=0&y=0

 

[Dee J]

If you're really going for medieval style, wouldn't pegged mortice/tenon be more in keeping (like a timberframe house), with overlong tapered pegs which could be knocked out from inside the frame for dismantling? Maybe change proportion of the lower rails to 150 high by 75 thick will give easier proportions to the joints.

Dee

 

[Steve Maskery]

If you want a strong, hidden joint that is easy to assemble and disassemble then I woud suggest and umbedded nut in the post, covered by a veneer.

Rout a channel in the rail to take a length of studding, cover it over to make a square tube and rout an access pocket for the washer and nut

A length of studding screws into the leg and is tightened up in the rail.

 

[MikeG.]

Welcome Simon,

a doubt if a mediaeval bed would have had a 100x100 rail. My instinct would be to amend this to 75x100, and to located the joints centrally on the plan of the post. This gives you 62.5mm of post either side of the rail, and I would use this for some draw-bore pegs. You would have the option of doing this from the outside for the really authentic timber-frame-house look, (but a bit crude for furniture to my mind), or from the inside where it would be hidden.

If you do it from the inside, you might consider drilling all the way through to the outside of the post, but leaving your peg short. A knock in pellet, left proud and rounded over (a good look anyway for a chunky bed)....but not glued.......would be removable to allow you to drive out the oak peg if you need to dismantle the bed.

Make sure you leave some good shoulders on your tenon......that is where the racking resistance in the entire bed comes from.

Mike