designing a round door - hobbit house style

I am seriously considering putting a round door on the downhill side of the 10x10 wofati. There are many ways to do this and there are many that have been done.


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If it is going to follow what is laid out in the hobbit book, then the round door must have a door knob in the middle of the door.

There are ways to have something that looks round, but it really isn't. But I want to shoot for what would be cool over what would be easy. Round is challenging, but round can be done.

I want the door to look simple to the outside - so that means that the hinges and stuff will have to be on the inside. Therefore, the door must open to the inside. And if the door opens to the inside, that means that it is going to take up a LOT of inside real estate.

I want the door to be made of wood, and really thick. Possibly five to six inches thick. We can make it hollow and fill it with a bit of wool. If the door is made even thicker (eight inches?) that would be even better.

I am thinking that the outer walls on the 10x10 will be straw bale walls. And they will probably be built entirely under the eaves thus making the 10x10 a bit more like a 10x11 on the inside. But straw bale walls are typically 18 inches wide - so this might leave only three feet for the eaves. the upside is that when the round door
swings in, it will take up a little less space.

I am guessing that the hinges for the round door will end up crazy elaborate and massive. Including something structural to be able to hold all that weight.

This door will end up on the downhill side.

Since the door will be made of many wooden layers, and the wall will be made out of cob and straw bale, it is possible that a lot of the hinge stuff can end up being hidden.

What am I not thinking of?

Is there a way to roll the door to the side? That would make it take up way less space.

You can have the hinges on the inside and swing to the outside just have one really sturdy one at the center.

How about a round door that rotates around a vertical shaft? Kinda like a revolving door in 2 dimensions?

I'll think of some more later I'm sure...

Joe - you and I must be thinking along the same time as my first impulse was to make it pivot around a central bar as well. Only problem is, you would possibly have a very awkward space to enter and exit through. Now you could move the center bar to about the 2/3 spot. The door would not pivot all the way around but you would get a larger, more accommodating opening than one split in half and it would take up less room than the full door swinging in. It would also allow for the center doorknob to be more ergonomic.

Also, I visited the Hobbiton set when in NZ over Christmas 2011/2012 (what a wonderful country!). Alas none of the doors opened as I recall. The interior scenes were all shot in a studio in Wellington. (NZers, correct me if I'm wrong).

Pivot door:



Round pivot window:

Concealed hinges to open outward. Found here, but will they support the weight? Dunno.

The pivot hinges might work better (same link lower down and here).

Another way would be to make only part of the door openable - again maybe 2/3rds to 4/5ths. The rest of the door would be part of the door frame and provide a straight edge for the hinges on the unopenable side.

Or you could make it swing up like a garage door (no lost space on the side). These run on a track I believe. This would also make a central knob more ergonomic.

Single inside hinge -



http://www.finehomebuilding.com/how-to/articles/inside-hobbit-house.aspx

double hinge, opens opposite the hinges. Could open out with hinges inside



http://lumberjocks.com/projects/10674

Jennifer, I too though of the center pivot first and later the 2/3 pivot. I'm liking this better than the heavy complicated hinges.

The thickness desired will add dimensional stability. It would suck to build a piece of artwork and have the thing warp. Think of plywood, each layer in a different direction. For an exterior door, using plywood is right out. Alternate the layers of lumber. Eye appeal suggest the grain be vertical on the interior and exterior face.

Load Bearing
8 inches thick would be tremendous. With a 6' diameter, built solid it would contain nearly 19 cubic feet of wood. Make it a hardwood, the door will weigh upwards of 700 pounds. A massive door demands a massive jamb and massive hinges.
Constructed hollow and filled with a lighter insulating material may be more practical, but if muscle building and fallout is a focus then by all means, build that puppy with a steel core!
What if you added wheels to bear the load?
A hinge fabricated with wood is possible, but changes in humidity can swell the wood. This brings the potential of a 700 pound door that is TOUGH to pull open.
Iron or steel will bear the weight, but can be costly as it would need to be custom made.
The pivot point for such a door may need to be offset rather than at the point of contact between the door and the jamb. This would allow several hinges to line up with using that new math.

Central Knob
There's hardware for that. Ever see an overhead garage door?
Be sure to examine the Physics of Round Doors.

Stopping the Swing
You'll be wanting one of these. I can spend hours playing with them.


A Massive door needs massive hardware

Jennifer Wadsworth wrote:Joe - you and I must be thinking along the same time as my first impulse was to make it pivot around a central bar as well. Only problem is, you would possibly have a very awkward space to enter and exit through. Now you could move the center bar to about the 2/3 spot. The door would not pivot all the way around but you would get a larger, more accommodating opening than one split in half and it would take up less room than the full door swinging in. It would also allow for the center doorknob to be more ergonomic.

Also, I visited the Hobbiton set when in NZ over Christmas 2011/2012 (what a wonderful country!). Alas none of the doors opened as I recall. The interior scenes were all shot in a studio in Wellington. (NZers, correct me if I'm wrong).

I am liking this thread! Jennifer opened it with some good advice to make a practical hobbit door. I think its far more durable to concentrate the stresses along the floor and wall vertically versus using hinges. Worst would be designing the door identical to the movies which I question the longevity. It may be obvious to many but its worth mentioning again the multiplying bending moment produced the further the hinge is from center mass of the door.



Just my two cents, but as a mechanical engineer I see an advantage to splitting the circular door in half where instead of placing the vertical rod 1/3rd of the door diameter from the wall you can place 2 rods at 1/6th the diameter. This reduces the distance from the center mass reducing shear stresses and potentially doubles fortification (depending on rod size). It also opens from the center allowing the door to be more functional. Hint, its difficult to squeeze out of a barely opened round door. Also you conserve heat/cooling by not having to open the door as widely for quick entry. On the other hand, sealing the door will be tricky near the axis of rotation centered at the rods.

paul wheaton wrote:
Since the door will be made of many wooden layers, and the wall will be made out of cob and straw bale, it is possible that a lot of the hinge stuff can end up being hidden.

What am I not thinking of?

I assume the door is going to be 6 foot or taller, meaning it will be over 6 feet wide. When you get into a width that big the expansion and contraction of the wood as the humidity changes can be significant. If you have multiple layers of wood and alternate directions it would help but you would have a very heavy door in the end. If making it hollow you would need to use a joinery technique that would help deal with the movement of the wood.

A very large door hanging out 6+ feet from the hinge point will take some hefty hinges, but more importantly a *very* hefty and stable beam to anchor those hinges into. I recently saw a standard type exterior panel door that was over 6 feet wide with windows in it. The hinges were hefty but not as big as you would think it would take and it was quite solid. Those hinges were anchored into a concrete wall though.

A 6+ foot wide door makes for a very big lever as well. I would make sure to oversize the hinges to take into account someone tripping and falling and grabbing the end of the door to stop their fall. At 6 feet out from the hinge that could put some serious strain on them, and the beam they are anchored into.

The pivot door some have mentioned would solve the hinge issues. I think it has some big draw backs though. First of all the door is then not a real hobbit door lol. It also seems having part of the door jam facing one direction, and another portion of the door jam facing the opposite direction with an awkward transition point at the pivot would make it hard to seal tight and keep the cold out. If there are children around I think they would find the smaller section fun to go through and it would be quite a pinch point when you can't see what that smaller section might be closing on. As a pinch point the larger door section would provide a lot of leverage for anything caught in the closure of the smaller portion. I just have an image of someone putting their shoes on holding the door jam as someone going out the door closes it and the weight and momentum of a big door like that crushing any fingers caught in it.

Chris - good point about fingers or entire small people getting squished in the small part of the pivot door!

Amadean looks to have the best solution above that is structurally sound and safe. (and to give credit where credit is due - Joe was the first one to come up with the pivot door )

I dig these threads where everyone comes with their ideas! It makes for a very interesting read as everyone comes at the issue from a slightly different angle.

Rock on, Permies, rock on!

With some of my earliest wofati designs I thought about putting in a round door. So I've been thinking about this for a very long time.

I dismissed the pivot idea because that would mean that you would have stops at certain points on the outside - but not the full circle. You could try to emulate it, but it wouldn't be quite right. It would never appear to be a pure circle along the edge. It would be compromised. And this is a sort of artistic endeavor.

Good point about needing the hinge and hinge mounts to take into consideration the weight of somebody stumbling and hanging onto the door for support.

I've thought about making just part of the door openable. Kinda like a big letter D - where the door would be 3/4 of the round. That works in many ways, but after years of thought, I think I want to go with the real thing. A truly round door.

Some questions ....

Does the door perfectly meet the floor, or, might there be a bit of a lip? At this moment, I am thinking it is probably best to have a hybrid: there is a bit of a rise on either side to meet the door.

Diameter? To have a bit of respect to the book, gandalf had to duck a bit to get inside. Regular doors are about 6 feet 8 inches tall - this is my guess because I'm 6'6" and most doors will try to take my hat if I am wearing one. Plus, the smaller the diameter, the less real estate that is consumed inside the house - and this would be a tiny house. At the moment, I am thinking that the door would be six feet in diameter.

Windows. I want to add a lot of light to the tiny house. With such a big door on such a tiny house, there isn't a lot of opportunity for a window. So it would be great if the door could include some glass. Of course, any glass added to a door like this needs to be symetrical in order for the round door theme to work. So I am guessing there would be four windows surrounding the door knob.

Inner door knob: I am thinking that the inner door knob does not need to be in the center.

Sealing: it will be cold outside. So I like the idea that the door can be sealed well. I am concerned about the door coming out of alignment and being too big to muscle into a closed state. So maybe the hinge will need to have some capacity for adjustment. I am also concerned about growing and shrinking. So it is possible that when the door closes, there will be a quarter of an inch of ring around the door to keep the door from jamming. Maybe a bit of wool could be tucked into the door jamb in such a way that the door slides by the wool. And the wool might need to be periodically fluffed or replaced.

Doors typically have a floor clearance to account for carpets and pebbles. The threshold height usually offers 3/4"-1". Round doors would be no different, but the concern is limited to a small arc at the bottom rather than a 3 foot wide door.

Gandalf had to bend over because the home he was entering was designed for a 3' tall hobbit. His hat was 3' tall. The homes of the humans in Middle Earth would be taller. Being that we are working with circles, the mass of the door would be dependent on square of the radius. Double the radius, get 4x the door size and mass. Windows would greatly reduce the mass. I think windows should be an integral part of the plan in order to get the weight down.

Weather stripping is an easy fix. Rather than seal the door on the edge, the door would be sealed at the face. The ring of the door frame can be increased to allow for expansion/contraction without sacrificing the seal. As long as the door remains a plane the seal will hold.

Knob Placement
What if the knob hardware was on the frame, rather than the door. The door would only need to accept the deadbolt. Add a strong handle for pulling it closed.

As we design this, I think we can keep in mind that there are heavier doors - like on vaults. So we are not talking about stuff that has never been done before, or even that unusual.

I also think this could be a fun time to start talking about the door knob (cast iron? ornate? simple? Piece of commissioned art? Maybe somebody reading this would be an artist?) and the latching mechanism.

Doors on ships have a threshold that is several inches, maybe even mid-shin for sea-going craft. You get used to it quickly, after a few barked shins.

Aren't there some old bank vault doors that are round? That would be a cool repurposing and the hinges would be stout.

If you made a step with the door and frame that would help with keeping air rush through. Like the inside of the door frame you see the actual frame, then inside it about half way theres a lip around. Like on a safe somewhat.

paul wheaton wrote:As we design this, I think we can keep in mind that there are heavier doors - like on vaults. So we are not talking about stuff that has never been done before, or even that unusual.

Though vault doors of that build are incredibly heavy and expensive. Its looking like the door could be half the price or more of the rest of the house.

How about a sort of pocket door? The door handle could be mounted through the door and mounted through some sort of bearing. So that it would stay fixed in your hand as you rolled the door.
The round door could roll into and out of a pocket wall.

If you have any fiber optic or power or phone companies nearby you might be able to repurpose one of those giant cable spools. Just pretty up the visable surfaces with nice wood.

A pocket door can be a simple solution for folks with less developed carpentry skills.
The whole door slides left and right.
This would allow wheels to support the weight, handle a great deal of weight, removes the need for a cumbersome hinge, takes up no interior space for a swing.
Wheel placement on a hidden section can counterbalance the weight to allow easy sliding/rolling.
The round section can be weather stripped where it contacts the jamb. Still thinking about the weather stripping for the other half.

The above design used a D shape rather than a circle

What do the wheels do? Couldn't the door itself act as a wheel? All of it's weight is on the floor?

mmm I thought about this in a different way . How about a circle door frame but two sliding door behind these could be rectangular or whatever . Since the door would be in a wall 10ft wide the maximum size would have to be 5ft round . If this is centred I dont see it as an issue . The fact that the doors are not round , they would only appear appear to be round means that they will be easier to construct , could even double as a window, weight would not be an issue , the hanging / sliding mechanism would be simple to make and maintain .
If you have a door that is 6ft wide opening into a room 10ft deep you are going to have a lot of space taken up by door and not much space available to people . If it opens outwards that can have other issues as its still a lot of air transferance for such a small volume.

David

In this drawing, I'm showing a plain door with hinge straps. Then a door with windows - and those straps won't work. Then an attempt at a steel framework that would work with the windows and all the wood would effectively be hung from the steel. Of course, steel does not come in rounds like this. So here is the same thing made from a bunch of flat pieces welded together.

How would you envision a hinge strap door like that mounted up on mud plaster walls?

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Amedean Messan wrote:How would you envision a hinge strap door like that mounted up on mud plaster walls?

There would have to be some structure built into the wall before the straw bales and mud went up.

Awesome idea about the hobbit door, but don't forget, those are movie sets and not functioning houses. Also, how many hobbits could Paul eat in one sitting? at least three and a half I think.

Benjamin Sizemore wrote:Awesome idea about the hobbit door, but don't forget, those are movie sets and not functioning houses.

I've been thinking of doing this long before the movies came out. I read the book.

I think it is a little bit of an art and engineering challenge. Fortunately, my brother is a great welder and has and excellent brain for this sort of thing. Plus, to do it "right" would just be super cool.

Oh come on you guys this just an engineering problem. What's the big deal?

You are right, Paul....

This is totally doable. As you know, you need to watch thermal bridging with steel (as well as wood). Most doors have rigid insulation inside, and that's a wonderful application for this project. Go ahead and build a prototype! When I stop by in the coming days I'm happy to give you and the crew a few suggestions that I'd consider as starting points.

Stay warm,
Noah

We are currently thinking that this will be at least $600 in materials - mostly steel. This cost will probably make this project sit on hold for a long while. The function of this thread is to help polish any design ideas.

Paul Wheaton wrote:Of course, steel does not come in rounds like this. So here is the same thing made from a bunch of flat pieces welded together.

Paul, making hoops like that isn't nearly as bad as it seems, with the right tool for the job. (I made some steel wheels for a cart earlier this year, got four out of four right on my first try. And they matched each other, too.) The tool is a roll bender: http://en.m.wikipedia.org/wiki/Roll_bender
No need to dismiss the possibility if it's what you really want! Perfectly achievable.

If only you had someone who loves to weld things...

Sean Kibler wrote:If only you had someone who loves to weld things...

I spent about 20 minutes talking to my borther about this yesterday.

What if you put casters on the door so the hinges didn't support the whole of the weight? The hinges hold the door vertical and allow rotation and the casters let it glide.

Edit::: or perhaps add a glide track of some sort.

More edit::: with a door as big as you're describing you could build said caster right into the door, leaving only an inch or so below the door. With a frame built to accommodate this it should seal right up. For wheel maintenance you could build a decorative access panel that just looks like woodwork.

Ken Peavey wrote:A pocket door can be a simple solution for folks with less developed carpentry skills.
The whole door slides left and right.
This would allow wheels to support the weight, handle a great deal of weight, removes the need for a cumbersome hinge, takes up no interior space for a swing.
Wheel placement on a hidden section can counterbalance the weight to allow easy sliding/rolling.
The round section can be weather stripped where it contacts the jamb. Still thinking about the weather stripping for the other half.

A pocket door would leave two feet of door sticking out when open ... probably more because the corner post of the home would take another half foot. While this would leave four feet of open space, the lowest part of the opening would only be one foot or less from the door... but the part of the door sticking out would not be in clear line of site being only 3 feet up from the sill. This is considering the door being offset to one side of that wall, not centred. I think centred would look a lot better and it seems to be the whole idea is a looks comes first kind of project.

Also one comment on the door knob in the centre rather than close to the edge:

My first thought is that the centre position means it is harder to open (as suggested by the article linked in one of the above messages) but with a 6 foot door, the length of one's arms comes into play as well. We have about a 3 foot reach with one arm. If the door knob was at the edge the door might pull the person opening the door right through the doorway (total 12 foot of movement), tripping them on the higher than normal door sill which would be close to that edge. (remembering this is also a heavier than normal door and once it started opening it would pull the person opening it with it as we have a learned habit holding on to keep it from "banging") The centre position still has 6 feet of movement, but the operator can be near the hinge so that while the hand moves a long way, the body doesn't.

As someone pointed out, something to "catch" the door at the end of it's swing would be required. It would have to be 3 feet up so it would put the least amount of strain on the hinges. It would probably need to be beefier than those one can pick up a Walmart.

It would also catch the wind rather well