Making a swing Joint Load Bearing, Engineering Question

egan007

I'm making a swing joint to attach to a bed so i can store it upright and lower it when needed.

Here is a diagram of one piece.



A: Is a piece of metal that the load of the bed will be bearing down on from directions 2 + 3 when the bed is lying flat.

B: Is a piece of metal that is screwed rigid to the wall.

C: Is a Bolt joining both bits of metal.

A and B have a nylon washer between them and are tightened with a Nyloc nut.

Piece A will be lose enough to swing in direction 1 This will give the bed the ability to pivot.

There is one of these joint each side at the head of the bed.

My questions.
I'm trying to work out if the joint will be strong enough to hold the bed.
It's light weight pine but I'm not sure how much load will be generated when it swings.

I'm not looking for may maths, just opinions on how thick I should make A+B
and How thick a bolt should C be.

Thanks:o

renko

If you have one of these on each side of the head of the bed, then the load on the 2 bolts (C) will vary from 1/2 the weight of the bed when the bed is down to all the weight of the bed when the bed is upright. Of course when the bed is down you have to add on for the weight of the occupants.

I'd say an M12 (12mm dia) bolt should suffice for the load but a larger bolt will give a smoother action, and stand up to repeated cycles for a longer period of time.

The distance between the plates A and B which is the length of the bolt, should also be kept as short as possible. 6mm steel plates should be fine.

Renko.

renko

If you have one of these on each side of the head of the bed, then the load on the 2 bolts (C) will vary from 1/2 the weight of the bed when the bed is down to all the weight of the bed when the bed is upright. Of course when the bed is down you have to add on for the weight of the occupants.

I'd say an M12 (12mm dia) bolt should suffice for the load but a larger bolt will give a smoother action, and stand up to repeated cycles for a longer period of time.

The distance between the plates A and B which is the length of the bolt, should also be kept as short as possible. 6mm steel plates should be fine.

Renko.

dave2pvd

Renko,

I was going to post on this last night, but didn't want to do the math to verify shear strength for the bolt. My gut said 1/2" on the bolt, thru 1/4 plates. Spot on!

Now what's the shear strength of a 1/2" bolt....? ~1,000lbs? Should do the trick. Go for a shoulder bolt though, far better as a pivot. I wouldn't worry about the nylon spacer. Size the shoulder bolt a little long and use a washer/washers as necessary.