How to make a door that rotates around a column

[Hobnob]

Hi there

I'm a complete novice about this kind of thing, but I've decided to fulfil a long dream of mine and make a bookcase with a secret door in it :)

I've thought about various methods, but eventually I've figured that the best system would be to make it rotate around a spindle on one side, so it ends up folded to the side rather than coming all the way out - that avoids having to have big load-bearing hinges on the side. But I'm trying to work out how best to get a smooth rotating action, especially if it is loaded with books. I don't want it to get all squeaky!

My current thinking is to use a solid inner spindle, then attach the bookcase to it with two radial ball bearings, and to the top and bottom with two thrust bearings. Does that sound sensible or is it overkill? Is there a simpler solution?

Thanks for any thoughts

 

[Danger]

I agree that a full-height spindle will be better than hinges, although in either case you would want to have some kind of wheel or roller on the outlying edge for additional support. My personal approach would be to put the spindle down the centre of the case, rather than near the edge, so the case simply rotates in place. That would eliminate balance issues.

 

[chayced]

Your idea sounds quite a bit like an ellison door. You might even be able to use off the shelf hardware.

 

[Hobnob]

My personal approach would be to put the spindle down the centre of the case, rather than near the edge, so the case simply rotates in place. That would eliminate balance issues.

Thanks for the suggestion. The only problem with that is practical use - anyone wanting to go through the door has less than half the actual door width to play with. But you're right, that would make is easier.

Re Ellison doors - oooh :) That looks interesting. I'll have to do a bit of research on that but it's certainly promising.

Thanks again
Hob

 

[DaveC426913]

I should show you some pix of my friend's wine cellar which is accessed via a secret door he built himself. It is a DVD rack/bookcase that opens like a door.

 

[Hobnob]

I should show you some pix of my friend's wine cellar which is accessed via a secret door he built himself. It is a DVD rack/bookcase that opens like a door.

Can you ask him if that would be ok? I found a couple of examples online, but one of them is built around a bloody great welded steel frame, which is a bit beyond me, and the other one seems to have been removed, leaving only some ghostly references...

Ellison doors look interesting but I'm not sure they'll work in my case because they seem to rely on precise balance, which sounds a bit specialised.

Hob

 

[BoilinMidnite]

Bearings are unnecessary and it's nonsense that you need "some kind of wheel or roller on the outlying edge for additional support." Casters will leave marks on floors and furrows in carpets, thus utterly defeating the "secret" aspect of your not-so-secret door. You don't want long spindles, you want pivots, specifically, two; one on top, and one underneath. Pivoted doors are as silent as the grave and can support unearthly mass as the bookcase's weight is transferred to the floor, not to a rickety doorframe.

You'll need to reinforce the bottom by sandwiching 1/2" steel rods between two 3/4" boards, then gluing and screwing them together (you'll need to rout channels in the boards to fit the rods. You have a router, right...?) And don't use stainless, it's not as strong as simple steel.

Additionally, you can place the pivot wherever the heck you want, it doesn't have to be in the center of the doorway, or crammed close to the doorframe. You just need to make sure the bookcase swings free and clear of hitting the doorframe. Simple trig will tell you the width and maximum depth of the bookcase based upon the position of the bottom pivot.

You'll need to mortise the top pivot into the doorframe's header (or lintel) and make sure it's lined up with the bottom pivot by using a laser plumb. This part is critical, but easy. After that just build the bookcase (use solid hardwood, NOT pine or ply) and hide it with attached mouldings.

 

[Hobnob]

Thanks so much, that's exactly the kind of advice I was looking for! (And incidentally, this sounds like my original idea, before I panicked about the weight, so I'm pleased to hear it)

Could you just clarify this bit - I can't quite picture in my head what you're talking about. Are you just describing how to make the base of the door stronger? Or does this have something to do with the rotation aspect as well?

You'll need to reinforce the bottom by sandwiching 1/2" steel rods between two 3/4" boards, then gluing and screwing them together (you'll need to rout channels in the boards to fit the rods. You have a router, right...?) And don't use stainless, it's not as strong as simple steel.

One last thing: for the pivots themselves, is this something I would buy as an actual piece of hardware, or are we just talking about two bits of metal slotted into holes?

 

[DaveC426913]

Can you ask him if that would be ok? I found a couple of examples online, but one of them is built around a bloody great welded steel frame, which is a bit beyond me, and the other one seems to have been removed, leaving only some ghostly references...

Ellison doors look interesting but I'm not sure they'll work in my case because they seem to rely on precise balance, which sounds a bit specialised.

Hob

His door is a simple 3-hinge design, pivoting inwards along one edge. I'll get pix the next time I'm over there.

 

[BoilinMidnite]

Steel-reinforced Base
Cut a piece of maple to the size of the base of your intended bookcase. Now cut another piece identical to it. Using a ½" roundover bit rout two channels into the face of each, along the long axis, approaching no closer than 1" of the sides. The channels should be equidistant and parallel.

Cut a 1"-diameter steel rod to fit the length of each channel. Now cut another rod identical to it. Put the rods in the channels then put the other board on top, making a steel-rod sandwich. Check for fit. If the boards won't meet at the edges, re-rout the channels a bit wider and recheck. Adjust till the rods are tightly held but still allow the boards to meet.

Screw and glue the base together. Use Titebond III, it's the best wood glue.

Pivots
You would buy the pivots. The top pivot, for example, comes with a receiver (mortised into the bookcase top) and a protruding pivot that comes down from the lintel. The bottom pivot is similar, with a cup-like receiver you mortise into the bottom of the bookcase and a pivot that comes up from the floor. Use the http://www.epivots.com/rixson-model-370.aspx" . It can accommodate up to 500 lbs so it's ideal for a single bookcase. If you have an option regarding which side to place the pivot, measure how level your lintel is and mount the pivot on the higher side. This will match any natural slant of the bookcase under load. Make sure both the pivots and the receivers are plumb! Otherwise you'll get a creaky carousel ride of crappy carpentry.

The top Rixson pivot (the part that goes into the lintel) looks intimidating and unnecessarily complicated. It is not. This pivot is not fixed, but can be raised and lowered by turning a screw. This is needed so you can fit the bookcase into the opening. If the pivot could not be raised you'd never be able sqeeze the bookcase into the doorway. The screw raises and lowers an armature which retracts the pivot into a recessed sleeve. You'll need to mortise the full height of this armature into the lintel, but it's a breeze with a trim router and a homemade template.

Twist
Don't think however that weight is just an issue for the doorframe. Solidly-built bookcases weith 80-100 lbs and books are heavy; the full set of Encyclopedia Britainica weighs 130lbs. It's likely you'll hit 250lbs before you realize it. This will rack or "twist" a bookcase. Twist occurs because the pivots aren't at the bookcase centerline. They act as mini fulcrums using the case's own weight to warp the frame. Twist affects even the stiffest build and worsens with load.

The weight of the bookcase makes it want to droop at the base. But it can't since the embedded steel rods provide rigidity. The base thus acts as a see-saw with the bottom pivot as the fulcrum. The pivot transforms the downward force at the strike side to an upward force at the hinge side.

Now the top is fixed at the hinge side because of the top pivot. But the pivot isn't centered; it's closer to the front. This allows the back to be more affected by an upward force. The back begins to twist up, and the pivot acts as a fulcrum causing the front to twist down. The effect is slight on the hinge-side but pronounced on the strike-side. There you'll see the bookcase twist noticeably out at the top and in at the bottom. Thick shelves anchored with glue and screws may reduce twisting but won't eliminate it. The solution? Angle iron.