designing a round door - hobbit house style

Consider the weight/mass of the complete moving part.

In your mind: Imagine perfect (no friction, perfect fit) hardware. Then push this large heavy door (or pull or slide or roll...) as you make your entry or exit. How long does it take to open the door w/modest force? How much force to open it in a dignified but prompt manner? What happens at the end of the movement (hint - the door wants to keep moving)? What happens if for some reason the door SLAMS? Or a hinge breaks.

Just a reminder that weight implies more than just the need to suspend the object and allow it to move. Something else to consider in the planning stage. Easy enough to ballpark a large weight figure, stick a 4/4 (or so) post 4-6' into the ground and use gate hinges to hang a big piece of plywood with lead (or whatever) nailed to the bottom to give you an idea of what kind of "feel" that much weight might have. Would it be OK if kids and small women had trouble w/the door? Large weight/mass might have a large impact when part of our path through daily life.

Rufus

Blacksmithing. If your door is that thick it will be heavy. At 22% moisture content, red oak runs about 52#/cubic foot. If the calc of 19 cu ft is right that puts it at 988 pounds. White oak (about 54 #/cu ft @ 22% air dry) =1026. Hickory at a medium weight of the 5 trees gets about 74 # at 22% and that is 1,368 # at 72 #/cu ft.

Cut the weight from better drying and you're still talking MASSIVE weight.

I'd forge my own huge strap hinges, MIGHT have a pivot point near the side of the door, but DEFINITELY hide a heavy duty industrial strength caster in the base and give it a smooth run whether i had to tile it or whatever.

Thank GOODNESS i don't have such a demanding fetish, lol.

What if you tried this.

Only had the window on the top. Probably divided into panes so it wasn't one large expensive piece, either vertical, or rays out from the center like a rising sun.

You make the door 3 layers. A middle layer with your framing and support, and an outer layer on either side that covers it up and looks nice. You could them add a 6 inch wide trim ring around the whole outer layer on both sides. This would give it the look of being much heavier than it really is, appearing 5 layers thick looking at the end of the door. But you really just have 2 skins and trim hanging off of a mostly hollow center frame.

You position the door hinges nonsymmetrical. One slightly above center and a second about a quarter the way up from the bottom of the door.

The main inner support is a triangle made of square steel tubing. Think fence gate, a long top extending across, a narrow end and a angled piece to strengthen the span. Everything else hangs off of or is built on top this brace. (red in the picture)

A big door takes big hinges. If you have a scrap yard around there see if you can find a couple heavy leaf springs. Build a fire to heat them up, then set a block of wood against the arch with a bottle jack on it and run a chain from end to end of the spring and use the bottle jack to pull it strait. Then cut the "O" or eye off of one end. Weld those to your framing. (Purple in the picture)

Here is a quick sketch just to show the idea. The hinges would need support between them than what is shown. But it basically shows the idea of a door built onto a heavy duty gate frame with leaf springs for hinges.

i haven't seen it, but have you contemplated a circular, folding, frech door style. Something designed like one of those cheap slotted closet doors.

Ok,
just as an inspiration. A Method to close a round space, without needing lots of space in the doorhall. But no- it is not a simple construction at all.


but beware, if you actually build this as a door, i might take a plane, just to have a look at it.
have fun
Ludger

Weather proofing might be a problem but I saw a prototype for a round door that operated like a camera shutter. I think it had six pieces.

By the way, the shire is my very favourite part of the lotr movies and I totally understand the round door fetish.

Looking at the vault doors that had a hinge in the middle of the door and a frame to a hinge I wondered if this could be put on the inside so the door could be opened outward and swung to the side.
I have the new version of sketch up so I decided to practice on this project.
The center handle could drop a bolt out the bottom of the center hinge into the sill while pushing a lighter one up into the lentil. I was thinking a round pipe inside the square tube could serve as the pivots.
The door then would then pull out and swing back into the space of the thick straw bail wall. The frame would not interfere with Paul's window design though it might be visible up close through the top and bottom corners on one side.

My frame came out a little large; it should stay within the inner dimensions of the door to swing through the opening.

In my stupid youth, I was a hotrod guy. We used suicide doors once and awhile. Car doors can be very thick and the hinges are concealed. We used to go to the scrap yards and get hinges from 1962-1966 f100 trucks because of their unique geometry. They were shaped like a question mark and pivoted deep in the jamb and really close to the outside of the body. It allowed a thick door with a curved surface and edge to swing kinda wide to clear the body without interference. If you could find an old early sixties ford truck just to swing the doors for a minute, you might get a few fresh ideas.

I helped build an adobe schoolhouse in New Mexico. We built an 8' round top door with vertical planks of recycled Douglas Fir. Stability was gained the old way by free floating tenons in rabbets between planks and forging our own strap hinges and clincher nails. The door was obscenely heavy and hard to open, so we built a regular sized nurse door inside of it. This helped to stabilize the door as well.

Morgan Barker wrote:In my stupid youth, I was a hotrod guy. We used suicide doors once and awhile. Car doors can be very thick and the hinges are concealed. We used to go to the scrap yards and get hinges from 1962-1966 f100 trucks because of their unique geometry. They were shaped like a question mark and pivoted deep in the jamb and really close to the outside of the body. It allowed a thick door with a curved surface and edge to swing kinda wide to clear the body without interference. If you could find an old early sixties ford truck just to swing the doors for a minute, you might get a few fresh ideas.

I hadn't thought of that. My thought was a ships rudder. Look in Buehler's Backyard Boatbuilding [1] for step by step instructions.

[1]The web site

Personally, i am always doing stuff. i want a door with a wide enough bottom that when i am carrying that "two hernia THING" we all have, and am inbalanced, i don't have to pick my feet up extra inches to clear the threshold. The sides of the round door are interesting to me, but personally, i'd rather have an Anasazi door - like a fat letter "T". Width up top for carrying THINGS inside, reasonably narrow at the bottom and flat so i dont' trip with my loads.

Just sayin'. And i like the Anasazi style of rockwork that i'd fake into cob, adobe, etc.

Instead of having a post buried very deeply to hold the hinges, maybe weld up a whole frame for the door. It can be covered with wood for aesthetics.

I totally agree on doing it right per Bag End standards, not compromising to make it easier.

Also, please do this. It's just too awesome.

I have not had time to read this thread in-depth yet, but wanted to post this before I forgot! This is a real working root cellar door. I can ask my friend how he did it if it is of interest!

Lisa Allen wrote:I have not had time to read this thread in-depth yet, but wanted to post this before I forgot! This is a real working root cellar door. I can ask my friend how he did it if it is of interest!

Yes!

It would be great to get lots more pictures too. Especially of the hinge and latch.

Its doable, but the material holding the door is concrete which I have no objection to. The Romans loved it, Floridians do and so do I. I however would not put more weight on that handle because those hinges need to be designed to carry the weight of 3 of those doors and it visually does not look to be the case.

Benjamin Sizemore wrote:

You could build it out of styrofoam but paint it to look like big heavy oak and build in breakaway hinges or neodynium magnets to hold it on. Then when you go to open it you grab it and go GAARRR!!! like an ogre and tear it off the hinges and throw it to the side, like you are going in to eat the hobbits.

Only cool if somebody sees you do it, tho.

Of course styrofoam is out of the question but why not some kind of veneer to make it look massive with some wool insulation inside to keep it lighter?

I may have some experience to offer as food for thought. Much of this is in my experience selling alot of butterfly valves. I know it seems wierd to think of a door as just an open and close valve (as big as it is), but it's the same.
With that said, round doors can not be supported by an edge hinge unless the post it is attached to is anchored in a concrete bunker. Let alone the hinge being able to carry all that leverage.

SO - you have to do the hinge as a pivot point. The guy who designed the hanging gardens of Babylon knew this well.

The big deal is to realize not only does the pivot point deed to be a bit away from the edge of the disc (door), but ALSO must be a couple inches off the plane as defined by the door jamb. This is called a double offset. To see what that is, google search "double offset high performance butterfly valves". They show it well. Large diameter butterfly valves will have the shaft (pivot point) way to close to the center for you, but the idea is the same.

So you need a top pintle and a bottom pintle double offset from the edge of the door and the plane of the door jamb. Set it into a thrunst bearing receiver hole on the bottom and a hole on the top of the jamb. This would be a pivot style.

If you insist on hinges on the edge, then set a piece of steel with a 6" web in a 36" x 36" x 36" concrete footing and frame it so you don't know what it is and make the hinge out of 1/2" plate steel. That door will be so massive that if you don't, when you go to open the door, it stays put and you turn the house.

Look at high performance butterfly valves with particular attention to the Offset design of the shaft from the disc in two directions. It will add to your pool of thoughts.

Obviously you don't want the shaft down the center of your door or it just spins on the shaft and you have a post in the center of your entrance way - so you set it off to one side as far as it will go. The part people do not understand is the second offset which is moving the pivot off the jamb as well. When you do that the door will cam off the jamb in lieu of "spinning".

You'd have to look at the way those websites graphically display how a "high performance butterfly valve" works to understand it. It's worth a look.

You're designing a door like the hanging garden of Babylon - in essence.

In the pictures of those round doors of your post - they are photo shopped - there is no way those hinges would support that much mass.

Design the door like a high performance butterfly valve but with the shaft moved way over to one side.

I hope you'll trust me on that one; I've worked on a lot of large diameter swinging discs on valves, and it's exactly the same.

Hans Quistorff wrote:

Looking at the vault doors that had a hinge in the middle of the door and a frame to a hinge I wondered if this could be put on the inside so the door could be opened outward and swung to the side.
I have the new version of sketch up so I decided to practice on this project.
The center handle could drop a bolt out the bottom of the center hinge into the sill while pushing a lighter one up into the lentil. I was thinking a round pipe inside the square tube could serve as the pivots.
The door then would then pull out and swing back into the space of the thick straw bail wall. The frame would not interfere with Paul's window design though it might be visible up close through the top and bottom corners on one side.

My frame came out a little large; it should stay within the inner dimensions of the door to swing through the opening.

I can not get this to appear as a picture but if you have sketchup you can download it and work with it some more.

yes- you got it. Do it like a vault door. You could re-purpose a care axle and hubs. Mount the axle virticle on the inside of the house on the jamb. Connect the hub to the door with a cool hinge. All the weight will transfer to the bottom bearing and make sure it is setting on the ground. You will need to remove the housing on the hub so as to make it smaller. That will give you your virticle shaft and bearings like a vault door. A junkyard should let you get an axel and hubs real cheap. You would basically modify the car axel and paint it and make it look cool and mount it on the inside jamb. Weld hinges off the axel from there and then use 1/2" thrubolts to fasten the disc to the hinges. A car axel should work same as a vault door arrangement.

Try these

http://www.hardwaresource.com/hinges/specialty-hinges/weld-on-hinges-welding-hinges/weld-on-hinges-welding-hinges

use a weld on hinge common for container doors and prison doors and boat hatches

link attached

you'll see the hinges are basically a small axle on top and bottom bearing. It's like a mini car axle

It takes some welding work - but you'll want to do some welding anyway so the hinges look really really cool.

3000 pounds per pair. $106 ea.



link



3000 pounds per pair. $88 ea.



link




3000 pounds per pair (for the 9 inch model). $94 ea.



link



3000 pounds per pair. $93 ea.



link

Just remember that 300 pounds can turn into 3000 pounds with a simple flick of geometry. Leverage can wreak havoc on even competent engineers plans, go open a door on a late 70s early 80s camaro. Those hinges are massive, but the curvature of the hinge side forced the hinges to be spaced closely; combined with the weight and length of the door, it caused a very common drop when the door was opened.
But if Tim is welding those hinges to a frame or post support, I am sure he will put a 20:1 failure factor into the overbuilding.

The roll bender looks like a perfect tool for the job, but if you don't need it for other things it would be an expensive lump after you finished this door.

A blacksmith with a forge, anvil and heavy hammer could make up the radius barstock easily (with a template to follow), and they would automatically look handmade rather than machined... since the look is important for this project. If you don't have a forge and anvil, you should, as these are tools with infinite applicability for low-tech building projects.

Nieces and nephews just visited Hobbiton here in NZ. I was looking at their photos and noticed that the doors on the hobbit hole that tourists are actually allowed to go into are regular doors swung from each side but with the round door frame in front of them. The holes with round doors are just pretend. I guess they decided that the physics was too difficult in the real world.

Ah! The thot plickens!!

The counterbalanced door with a pivot a little ways out from the center of mass sounds smartest to me. Easier to move, and if the door has windows and insulation and the counterbalance-part is more solid, it would balance easily and be a lot easier to work. A simple rolling door has some appeal too.

The round "hole" implies that one enters like an animal, head-first and slithering, rather than upright like a stick on parade. Making it a little low, or even a wide window-seat that you literally crawl through, could be "authentic". Arctic dwellings and tipis have rounded entrances which sometimes helps with the structure and cold-lock properties of those dwellings. Boat's hatches and bank vaults are rounded for strength and because it allows a better seal, convenient entry with one's hands full is a secondary function, and rolling trolleys through is pretty much impossible.

However, if the goal is to have a fantasy door that appears to open on hinges, there are several ways to do the hinges.

1) A single, massive, engineered hinge at the point where the round cheek meets the frame. This seems like the silliest and most expensive option, as the hinge would need to be enormous, effectively two or three hinges in one.
2) Like the bank vault doors, with the hinges built into a post a little ways back from the door, so the door is more like a round plug that fits into the wall, but hangs from a rectangular frame that connects with the hinges.
3) Like some country gates, where you have a cable from a tall gate post, to take some of the weight off the hinges.

The windows do not have to be arranged around a central cross to be symmetrical and pleasing. There are a lot of "fan-light" windows over regular doors or windows, which could be used for the upper part. Then you can use regular windows below. You could also have a fan-light top, and then a gibbous lower window so the whole thing was round but a little above the center of the door.
This multi-pane style (shown) would give a central handle, which would be used to open the window not the door. This offers a "nurse-door" effect where you can climb out the window if the door is too heavy or sticking today. A discreet sliding bolt in the main door would allow opening the whole thing from either side, and could be blocked from inside for a simple lock (or have an ordinary hasp-lock fitting).

I don't see that the central handle is ever going to be a simple and sole control with this massive a door. You will be manhandling it like a barn door, perhaps with a shoulder to the frame, so any element that can be grabbed should be strong enough to stay attached while being used to move the whole door.

We did lots of weird-shaped panels for theater using just door-skin (1/8" luan, lew-ahnn, however you spell it) over a 1x2 or 1x4 frame, as strength demanded. Some corner bracing but mostly just simple frames.
The resulting panels lightweight like a regular door and easily moved.
For a thicker door like this, I would look at embroidery hoops, drums, barrels, or wagon-wheels for ways to make the edge:
- either multiple pieces butted or lapped and jointed, with spoke-like frames and a metal band for rigidity, like a wagon wheel. Or the barrel variant: wedges with hoops to hold them together.
- drum/embroidery hoop: A lapped, bent-wood hoop, held to round by some spoke-like tension cables or lacing. A very light skin (fabric, leather, or very thin wood panel). This light-weight version would basically be a fluffy plug with the lightest possible door skin. It would be lashed or braced onto the rectangular hinge-frame, and the window, handles, latches, and other structures would all be built into the hinge-frame not the door itself.

The images below show one possible way to frame the door skeleton. Black is framing; white is insulation (or windows); the second image shows a thin wood skin.
I would not make the wood skin thicker than 3/4"; 1/4" would be better in a lot of respects if you could keep people from kicking it to pieces. Maybe put in a thicker kick-plate at the bottom and make the rest thin.

Here's a video of a company that makes "Hobbit Holes" -- little structures of varying uses (and usefullness-es). Lots of shots of the round doors working.

<iframe width="560" height="315" src="//www.youtube.com/embed/_DCOrHc-tKI" frameborder="0" allowfullscreen></iframe>

ok, what did I do wrong...?

Valerie Dawnstar wrote:Here's a video of a company that makes "Hobbit Holes" -- little structures of varying uses (and usefullness-es). Lots of shots of the round doors working.

[youtube]<iframe width="560" height="315" src="//www.youtube.com/embed/_DCOrHc-tKI" frameborder="0" allowfullscreen></iframe>[/youtube]

ok, what did I do wrong...?

Here ya go sweetie.

[youtube]https://www.youtube.com/watch?v=_DCOrHc-tKI[/youtube]

Found a tourist video of the film set.

Saw this picture and thought of this forum:



The company that made it is Firetube. And it is not very big (10inch dia maybe?) But the hardware is quite clear. I like the adjustable part. The seating of the door can be precise even with wear.

I don't think I say this mentioned or if its what paul would want but...
what if instead of one big round door you have two half circle doors? that way you can open just one for everyday in and out or open both sides for the full circle. plus I can already imagine how much easier moving in furniture would be with a big round doorway! hahaha.

I just found this thread, and the thought that came to mind was an iris door (which is what I think Ludger was talking about). This would require more space around the frame of the door (including beneath it, which might be a non-starter), but it's really cool. Here's a toy sample:



BTW - If you haven't seen them, the thing that gave me the idea was an expandable table, called a "Fletcher Capstan Table". Amazing bit of engineering!

John Hazen wrote:I just found this thread, and the thought that came to mind was an iris door (which is what I think Ludger was talking about). This would require more space around the frame of the door (including beneath it, which might be a non-starter), but it's really cool.

Interesting.

I notice while looking through some of the other Iris opening mechanisms after that youtube vid is done, that using more blades of thinner shape uses a lot less outside of the opening room. I get the idea that a half iris could work that would have nothing below the door.

On the down side (why we don't use irises for doors or windows):
- Quite complex.
- Not real sturdy.
- How would you seal the thing?

- not perfectly round - but working every day in upstate new york ! Link Below :


https://www.facebook.com/Cronk-Earthship-162709063823518/?fref=ts


For the Craft ! Big AL

allen lumley wrote:- not perfectly round - but working every day in upstate new york ! Link Below :


https://www.facebook.com/Cronk-Earthship-162709063823518/?fref=ts

That is one big hinge!

Here's a gorgeous variation. While not a round door, it does remind me of the letter "p."

https://m.facebook.com/artandartarchitecture/photos/a.1645903988997089.1073744052.1607021469552008/1645903992330422/?type=3&source=48

(source)