Problems hinging a compound curved door

[Harry Jeffery]

Hi all,

I was wondering if there is someone who could help me with hinging a cupboard door which has no hinge points in-line with one another

I'll attach an image of a 3D assembly for you to look at as my descriptive skills are not quite up to scratch...

Any questions about the measurements I'll answer as quickly as I can.

Any advice on manufacture of the doors would be handy as well because my tests of steam bending show that they will require a frame type structure to fix to in order stop the pieces straightening back up again.

Thanks in advance,
Harry

[Jerry Miner]

Harry---

I don't know if this will help you, but here's the way I see it:

You could use a small pair of butt hings (or Soss-type hidden hinges) if you place them in line with each other---with the hinge barrels lined up---but with the upper part of the door projecting out as it does, the door would swing down as it swings out. (Which could maybe be ok if you place the whole thing on a base so there is room for the downward swing).

Another possibility is a pair of pivot hinges (knife hinges) mounted top and bottom, lined up plumb (to give the door a horizontal swing). With this arrangement, though, the top of the door would swing into the cabinet as the door swings open, so you'd have to adjust the joint at cabinet side-to-door to allow for this motion. Could be done, though.

You've certainly created a challenge for yourself. Good luck with this project. Would love to see a pic when it's done.

[Yonak Hawkins]

Tough problem. Even some sort of single-point hinges would be problematic because the doors would tend to fall open. How about if you were to have the top overhang enough to hang the doors from a curved track and wrap around the sides when open ? It would be tricky to accomplish.

[Mel Fulks]

The only double curve things I've done have been some stair fittings . Only dc doors I've seen were in Federal houses . I think they are wood 'bricks' under veneer. The book CIRCULAR WORK IN CARPENTRY AND JOINERY covers some dc things. I would try Italian bending ply for core ,then veneer it. Interesting project.

[Mel Fulks]

Upon review ,I don't think stair work qualifies as double curvature . I do think the book and bending ply would be a help to you.

[Mike Wilkins]

As others have stated, the mis-alignment of the hinge points makes for a difficult solution, if there is one. Is there a way to change the design to allow hinging on the inside, straight side of the door? Just a thought.

[Harry Jeffery]

Firstly, Thanks for all the replies so far, some very useful points and comments raised.

Jerry,
I don't think allowing the doors to swing downward would be suitable for the intended purpose as this would, due to the maximum height of the design, effectively reduce the usable size of the cupboards.

The use of knife hinges might be interesting and maybe I can develop a way of working around the door opening into the cupboard?! But which part do you mean 'cabinet side-to-door'?

I'll try and remember to post photos of this during manufacture and once finished especially.


Yonak,
I too thought about single point hinges but came to the same conclusion...

For the track to run the doors in, do you mean a system which continues the curve of the doors further around the top therefore taking the doors around the back of the design? Because that would be tricky to accomplish, but a good idea none the less.


Mel,
Thanks for the book name, it does sound useful, especially if it does cover some types of compound curved articles.

Is the Italian Bending Ply you mention the same as aircraft ply? Because I can source that, but I've never heard of Italian bending ply before!?


Mike,
There must be a solution!! ...I hope...

Do you mean change the design of the door to have a vertically flat inside face, because that would make initial hinging easier, but would still mean that the top pivots into the cupboards.



Anyway, Thanks again to everyone that has posted, the feedback of possible ideas has been very useful so far.

Harry

[Sam Murdoch]

Not to be a wise guy but why not hinge to the straight edge? Would it be so awkward opening in that direction? Otherwise I think I might build a mock up version or, better yet, draw an operational model in SketchUp and play with where to locate the top and bottom pivot pins. The top could just be a pin and the bottom could be a knife hinge to facilitate the install. Or maybe just use a spring loaded pin on the bottom which could be depressed with a flat knife, again to facilitate the install.

I have used SU to locate Rixson pivots in a few bookcase/doors and the SU models allowed me to get very very close tolerances with complete confidence without the need to build a mock up.

[Mel Fulks]

It's also called Italian bending poplar,used a lot for architectural arches ,etc,and for making things like bow front chests.You can order small pieces mail order .4x8 and 8x4 (it's sold in both directions) available at many better cabinet plywood supply houses. Three ply and just under 1/8 th inch thick . Very smooth.

[Jamie Buxton]

First, as others have said, you want to get your hinge axis vertical. That is, a line from hinge axle to hinge axle on one door should be a vertical line. If you don't do that, the door is going to try to flop open or flop closed -- not the behavior one expects from a door.

Here's a sketch of one way to handle the hinging....

door arms.jpg

This sketch is looking straight down on a curved door. The door is connected to support arms, which are pivoted well back inside the cabinet. The arms have a big break in the middle so that they don't collide with the casework. I show only one arm in this sketch. You'll need to have a longer arm at the top, and a shorter one at the bottom. But if they're pivoted on a vertical line, you'll be okay.

I'd probably put a fixed shelf just above the lower arm, so the lower arm isn't constantly trying to sweep stuff out of the cabinet.

Just in case you haven't figured this out yet, what you're trying to do is very advanced woodworking. It can be done, but it is very challenging.

[Yonak Hawkins]

For the track to run the doors in, do you mean a system which continues the curve of the doors further around the top therefore taking the doors around the back of the design? Because that would be tricky to accomplish, but a good idea none the less.

I couldn't tell from the sketch how much space there was on the side of the unit to, possibly, park the open doors. If the length of the sides is half the width of the doors, maybe each door could be split in half and have two sets of runners, the first door half controling the second when the halves line up. When parked (open), the door halves would be stacked at the side of the unit. Is this clear as mud ?

Another idea I just thought of .. maybe you could fashion some kind of bi-fold doors. I don't know if that would work what with the different travel distances for top and the bottom, but it seems like it would. Some experimentation or computer modeling would tell. Single point hinges would have to be used and there would be the same problem with the doors falling open but only half as much and they wouldn't free-fall because the fall would be controlled by the front edges of the doors being held.

[Sam Murdoch]

First, as others have said, you want to get your hinge axis vertical.

You'll need to have a longer arm at the top, and a shorter one at the bottom. But if they're pivoted on a vertical line, you'll be okay.

These 2 points are fundamental to the solution. I haven't drawn this up - really just doing a mental exercise - for what that's worth . As I began to describe in my earlier post I think this could be done with 2 pins but as Jamie writes and I think A Sketch Up mock up will quickly show, the top pin would be in to the cabinet deeper than the bottom.

I was thinking that the bottom of the door could sit directly on a pin but that at the top you would need to connect to the top pin using a fabricated bracket of some sort that would ride on the pin but be attached to the back face of the door at some location towards the center of the door rather than at the normal hinge edge. This bracket might need to be jointed itself - like that shown in Jamie's sketch Here the SU model or a real world mock up is essential.

Further thinking on the matter and I wonder if you might use one arm from some type of lid stay as the top connection, and maybe - just maybe it could be one of these slotted versions. The slot would ride on the pin. A door catch will be a key feature of the success of this system.

Unknown.jpeg


Looking forward to seeing the real world solution.

[Harry Jeffery]

Sam,
Firstly, there is no straight edge...

I've drawn a model in SolidWorks which is like sketch up, but industrial standard, so I have that to look through, its just I've still had problems in finding a suitable hinging method.

I'm also working on a real world mock up model at the moment, I'm just waiting for the glue to dry.

The sliding door stay may work but, as you brush upon, a catch would be essential. When opening the door, wouldn't the door fall about the place if I used this?


Mel
Thanks for the alternate name, I'll try and find some to test out because it does sound interesting and very useful stuff


Jamie
Thanks for the sketch, that is a good idea which I had not thought about yet,

As I was reading the post I was thinking a similar thing myself about the shelf just above the bottom swing arm,

I suppose its just I like a challenge


Yonak
I see what you mean now thanks,
I think for a bi fold door, it should work, shouldn't it!? or am I thinking of the wrong type of door type!?



Thanks to everyone that has posted so far, the feedback has been very helpful
Harry

[Sam Murdoch]

"Sam, Firstly, there is no straight edge... " Harry, sorry, I can't see from the thumbnail that the center edge also has a curve.

"I've drawn a model in SolidWorks which is like sketch up, but industrial standard, so I have that to look through, its just I've still had problems in finding a suitable hinging method.

I'm also working on a real world mock up model at the moment, I'm just waiting for the glue to dry.

The sliding door stay may work but, as you brush upon, a catch would be essential. When opening the door, wouldn't the door fall about the place if I used this?"

I don't really know but I think not. Seems to me that it would simply open within the arc. That particular stay might not be the best option if a lid stay is at all an option. I was suggesting some type of articulated arm - could be made of wood or metal but then I thought that the lid stay has merit as it is already made with attachment points and a jointed arm. To be used horizontally of course - not at all as the manufacturer intends with one end attached to a pin in the top of the cabinet and the other fastened to the back face of the door. That attachment points located with trial and error/mock up or modeling. All theoretical and maybe not at all workable - just trying to think a solution. You've got the real job, but a fun one, I'm sure.

[Jerry Miner]

Jerry,
... which part do you mean 'cabinet side-to-door'?

I was trying to say that the joint between cabinet side and door (the "jamb line" in construction parlance) would probably not be a straight line or flat plane the way it would be with a standard door.

I concur that the pivot point would be well inside the cabinet at the top, requiring some sort of bracket (assuming a vertical orientation of the pivot points, in order to provide a horizontal swing)---which would lead to a long "sweep" of the top edge of the door, which would lead to a conflict with the cabinet side at the hinge side of the door---unless the "jamb line"---where the door edge meets the cabinet side is "re-shaped" (changing from a flat plane or straight line). I'm sorry I can't articulate this better. A mock-up (in a 3-D drawing program or actual physical form) will make this clear, I think.

Good luck with this project. Certainly sounds both interesting and challenging.