Bed Side Rail Join

Dave Richards

Dave
Senior User

My son and I have been looking at bed designs in preparation for building him a bed. He likes the design of the day bed in the background of this image. It's a design by a French furniture designed from the mid to late 1940's. I modeled it up and quickly modified it for a standard mattress.

I'm looking for opinions on how to attach the side rails to the legs. The side rails are 1-1/4 in. thick by 2-7/8 in. high with a 1-1/4 in. thick cleat glued on the bottom edge. I don't want to use conventional bed bolts and I don't think standard hooks will work. I was thinking of steel dowels and a bolt into a cross dowel set into the posts. Another thought is to use those joiners designed for counter tops.


I could revised the design to make the rail taller and just add the cleat on the inside which is more common but I'm trying to adhere to the original design as much as I can.
 

Hmerkle

Board of Directors, Development Director
Hank
Staff member
Corporate Member
Dave the rail fasteners that Nick is showing are a good option - another option is bed rail bolts:

 

Dave Richards

Dave
Senior User
Thanks guys.

Nick, I thought about those hooks like you show but the rails aren't tall enough.

Hank, I'd forgotten about that sort of connector system. I expect that'll do the job, though. Thank you.
 

chris_goris

Chris
Senior User
Dave,
The reason most bed side rails are taller is a structural integrity issue, I think 2.75" tall is insufficient for "dynamic" loads... I will not elaborate.
 

JimD

Jim
Senior User
My gut feeling is that 2 7/8 isn't tall enough for the rails but I did the math and I think it would work, provided you use a clear piece of a good hardwood. The formula for deflection of a simple beam with a uniform load is just weight times the length (of the rail in this case) cubed divided by 384 times the young's modulus (about 1.5 million psi for hardwoods) times the area moment of intertia. The latter is the thickness times the height cubed divided by 12 for a rectangle. I get less than 1/64 deflection for 200 lbs on one rail. There are a lot of simplfications in that calculation and I only did it to see what ballpark we are in. If it said an inch, I would be worried. At nearly no deflection I think structurally you are OK. Assuming I didn't mess up the calculation. If a person is seated near the mid span, the loading is worse than I assumed. But if they were in the middle of the bed laying down, the two rails would support them.

I would still want to use my normal rail connector, however, and the smallest I saw was 4 inches high. I don't think that would totally mess up the design but it's up to you and your son.

The only time I've done a narrow rail like this was for an old bunk bed made of 2x4 frames and I bolted them to the posts. Crude. But it worked. The kids used them for years and there was never the hint of a structural problem That is another check that you probably do not really have to increase the height.
 

Dave Richards

Dave
Senior User
Thanks for that Jim. (I almost lost you at "My gut feeling." :p Then I caught up again.)

The bed would be made of old, northern-grown white oak. The cleats glued to the bottom of the rails are 1-1/4 in. thick so I would expect you could treat the rail as if it is 4-1/8 inch tall. Based on your numbers, I'm thinking it should be OK.

Thanks again.
 

chris_goris

Chris
Senior User
My gut feeling is that 2 7/8 isn't tall enough for the rails but I did the math and I think it would work, provided you use a clear piece of a good hardwood. The formula for deflection of a simple beam with a uniform load is just weight times the length (of the rail in this case) cubed divided by 384 times the young's modulus (about 1.5 million psi for hardwoods) times the area moment of intertia. The latter is the thickness times the height cubed divided by 12 for a rectangle. I get less than 1/64 deflection for 200 lbs on one rail. There are a lot of simplfications in that calculation and I only did it to see what ballpark we are in. If it said an inch, I would be worried. At nearly no deflection I think structurally you are OK. Assuming I didn't mess up the calculation. If a person is seated near the mid span, the loading is worse than I assumed. But if they were in the middle of the bed laying down, the two rails would support them.

I would still want to use my normal rail connector, however, and the smallest I saw was 4 inches high. I don't think that would totally mess up the design but it's up to you and your son.

The only time I've done a narrow rail like this was for an old bunk bed made of 2x4 frames and I bolted them to the posts. Crude. But it worked. The kids used them for years and there was never the hint of a structural problem That is another check that you probably do not really have to increase the height.
Its not the strength of the rail Im talking about, its the bearing surface at the joint.
 

McRabbet

Rob
Corporate Member
I would recommend making a shallow mortise in each bed post and add a tenon to fit in the ends of the side rails. Then secure the side rails using bed bolts with cross dowels like these from Lee Valley Tools.
 

Dave Richards

Dave
Senior User
I would recommend making a shallow mortise in each bed post and add a tenon to fit in the ends of the side rails. Then secure the side rails using bed bolts with cross dowels like these from Lee Valley Tools.

The shallow mortise and short tenon were planned but as I indicated in my first post, I want to avoid bed bolts like the ones in your link. I don't want them to show on the outside of the bed.
 

zdorsch

Zach
Corporate Member
How are your metal working skills?

What about making or modifying something like these:


Another thought is mounting two button head bolts in the rails and mortise one of these into the head board and footboard stile:


I realize the above is too tall but what about a steel stud on top and one keyhole plate on the bottom (hopefully that makes sense):


 

JimD

Jim
Senior User
If you want a joint that doesn't show from the outside, you could do the short tenon you describe but put a hanger bolt inside it with the nut accessed from the inside of the rail. Here is a link to hanger bolts:Steel Hanger Bolts-Steel Hanger Bolts

The wood screw thread part would go in the leg and project out into the rail. A hole would be needed along the rail for the joint and an intersecting hole for the nut. The intersecting hole should probably be made flat on the end towards the leg. It would not be a through hole so it would not show on the outside.

The short tenon would take the weight, all the hanger bolt has to do is keep the joint tight.
 

Dave Richards

Dave
Senior User
Thanks Jim,

Hanger bolts crossed my mind, too. I might do a sort of hybrid thing. A piece of threaded rod into an insert in the leg and hex nut with flat washer in the rail. Of course it's probably less mucking about to use the bed rail connector thing Hank linked to.
 

Jeff

New User
Jeff
The shallow mortise and short tenon were planned but as I indicated in my first post, I want to avoid bed bolts like the ones in your link. I don't want them to show on the outside of the bed.

The cross dowels shown in the Lee Valley link don't look to be very long and your bed rail is 1.25" thick. Couldn't the hole be drilled from the inside of the rail. No cover is needed.

The bed bolts that Hank linked to also appear to have the hole drilled on the inside of the bed rail but not all of the way through the rail.
 

Dave Richards

Dave
Senior User
The cross dowels shown in the Lee Valley link don't look to be very long and your bed rail is 1.25" thick. Couldn't the hole be drilled from the inside of the rail. No cover is needed.

Look at the link again, Jeff. The cross dowel goes into a hole in the rail and of course it doesn't need to go through. The bed bolt goes into a through hole in the leg. That's what I want to avoid.

The bed bolts that Hank linked to also appear to have the hole drilled on the inside of the bed rail but not all of the way through the rail.

Yes. If you look at the installation instructions you can see that the 35mm diameter hole in the rail does not need to go through. Since the bolt is headless and screws into an insert in the leg, this is a more desirable option for us.
 

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