Flush trap opening flat

I've been banging my head against this one all morning, and it's gotten to the point where I know I need a set of fresh eyes on the question.

I'm building a trap door that needs to sit flush with the deck and open completely flat. The director is taking inspiration from this production of Shakespeare in Love that Cincinnati Playhouse did a few years ago, so I know it's possible:



What I'm trying to figure out is what the heck kind of hinge they used that would do that. And of course the actors are sitting over what I really need to see in the pic of it open... Zooming in, I can tell that the door sets back from the edge of the trap a bit when it's open; it doesn't look like it's lined up vertically.

No amount of Google-ing/flipping through my usual catalogs is turning up an obvious solution. Everything I find will do either, but not both.

Suggestions?

It looks to me like they are just using cleverly painted strap hinges on the deck.
This would be a slight trip hazard so I don't know that it would be my first option.
I've had good luck just using a standard door hinge, carefully mortised into the trap framing. It's really a very minimal trip hazard. Piano hinges do the trick as well.

I had to rig two Steel framed "french doors" into a floor for a production of some Chekov play... < I HATE Checkov).

I used "Concealed, Mortise mount entry door hinges" McMaster Carr has them here: https://www.mcmaster.com/1612A42

It is also important that the entire perimeter of the frame have a very stout stop and if there is to be no center jamb then the framing of the doors needs to be really stout.
The french doors I did were 1.25"HSS with 3/4" Lexan Panes so it could be walked on. They were on a rake, with a pond underneath... No, you cannot make a pond rake at the same angle as the doors..... <directors...>

I don't see why butt hinges mortised into edge of opening and edge of trap door wouldn't do this. The barrels of the hinge might be slightly proud of floor but very little. But I feel there is another constraint you see.

BillConnerFASTC said:

I don't see why butt hinges mortised into edge of opening and edge of trap door wouldn't do this. The barrels of the hinge might be slightly proud of floor but very little. But I feel there is another constraint you see.

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To get 270° out of the hinge, so the door lays completely flat, the entire diameter of the barrel has to be proud of stage floor. Have you met an actor that couldn't trip on a line that was only on the design sketches?

Van said:

To get 270° out of the hinge, so the door lays completely flat, the entire diameter of the barrel has to be proud of stage floor. Have you met an actor that couldn't trip on a line that was only on the design sketches?

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This exactly. The director is adamant that they be as flush as possible because there's a substantial bit of fight choreo in the show and student actors...

The problem with the strap hinges is that while they would lay flat, they don't open all the way; they get to a certain point and hit themselves.

Van said:

I used "Concealed, Mortise mount entry door hinges" McMaster Carr has them here: https://www.mcmaster.com/1612A42

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I was looking at these this morning, but I couldn't tell from the image & description if they were able to open completely so the door would lay flat. Do they let it fold back all the way so that the actors could sit on it like in the picture?

blueeyesdesigns said:

I was looking at these this morning, but I couldn't tell from the image & description if they were able to open completely so the door would lay flat. Do they let it fold back all the way so that the actors could sit on it like in the picture?

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Yep, That was my major concern with the french doors I did. Because they are mortised there is not a huge gap at the hinge jamb. Also the have a very low bevel angle when the open, smaller gap between the doors.
I laid the door in place on the stage to do the mark ups of where to mortise even.

Van said:

Yep, That was my major concern with the french doors I did. Because they are mortised there is not a huge gap at the hinge jamb. Also the have a very low bevel angle when the open, smaller gap between the doors.
I laid the door in place on the stage to do the mark ups of where to mortise even.

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Awesome. Thanks for humoring me. Now that I'm looking at the catalog page again, I'm seeing a 3d rendering with the hinge open that I wasn't seeing before. It wasn't loading or something. Shrug. I ordered one to design the frame with (bit of a pucker factor on the price there - want to make sure it'll work before I order more....)

blueeyesdesigns said:

Awesome. Thanks for humoring me. Now that I'm looking at the catalog page again, I'm seeing a 3d rendering with the hinge open that I wasn't seeing before. It wasn't loading or something. Shrug. I ordered one to design the frame with (bit of a pucker factor on the price there - want to make sure it'll work before I order more....)

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@blueeyesdesigns Try Googling Soss hinges, be securely and comfortably seated prior to googling their prices.
Toodleoo!
Ron Hebbard

There's also a shop-built solution in Technical Design Solutions for Theatre Volume I Page 195. I won't post a scan of the page here, but a search for "A Simple Flush-Mount Hinge" and the title of the book might turn up some useful results. There's three volumes of Technical Design Solutions and they're full of useful solutions to problems.

Rose Brand also sells a double knuckle hinge for much cheaper than the McMaster Carr hardware linked above. It looks just about identical to the one in the book and looks like it will lay flat both open and closed.

Van said:

To get 270° out of the hinge, so the door lays completely flat, the entire diameter of the barrel has to be proud of stage floor. Have you met an actor that couldn't trip on a line that was only on the design sketches?

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Why does the door need to rotate 270 degrees--does it need to open both downwards and upwards? The pictures look to me like they only open upwards, or 180 degrees. If the hinges are mortised into the surface of the trap and the stage platform (rather than on edge) so that the pin is downward and they fold on themselves when the trap opens, it should be flat. I don't know how easy it would be to procure hinges with the countersinking on the "wrong" side of the hinge leaves, though; maybe one would have to re-countersink them and use larger screws than originally intended.

Here's a quick, unclear sketch in case the words are unclear:

As you drew here the door would not open to fully flat. It would get to 160°-175° and the hinge would stop the and the 'outside' edge of the door would would still be off the ground. If you flipped over your picture the outside edge of the door would hit the ground but the inside edge of the door would be off the ground and if anyone sat on the inside edge of the door the pressure on the hinge would threaten to break bend or pop the screws out of the hinge. Flipping the hinge over would also bring about the issue of having all the barrel sit proud on the stage surface again.

Van said:

As you drew here the door would not open to fully flat. It would get to 160°-175° and the hinge would stop the and the 'outside' edge of the door would would still be off the ground. If you flipped over your picture the outside edge of the door would hit the ground but the inside edge of the door would be off the ground and if anyone sat on the inside edge of the door the pressure on the hinge would threaten to break bend or pop the screws out of the hinge. Flipping the hinge over would also bring about the issue of having all the barrel sit proud on the stage surface again.

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Google Soss HInges and be prepared for SERIOUS sticker shock. . .
Toodleoo!
Ron Hebbard

Van said:

As you drew here the door would not open to fully flat. It would get to 160°-175° and the hinge would stop the and the 'outside' edge of the door would still be off the ground. If you flipped over your picture the outside edge of the door would hit the ground but the inside edge of the door would be off the ground and if anyone sat on the inside edge of the door the pressure on the hinge would threaten to break bend or pop the screws out of the hinge. Flipping the hinge over would also bring about the issue of having all the barrel sit proud on the stage surface again.

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Now that I think about it more thoroughly, you're exactly right. Mea culpa. Thank you for setting me right...and doing so gently.

DrewE said:

Now that I think about it more thoroughly, you're exactly right. Mea culpa. Thank you for setting me right...and doing so gently.

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Soss Invisible Hinges; in sizes from tiny to MASSIVE with prices to match.
Sit down and be securely belted in place prior to Googling the pricing of their larger, heavier load-rated, models.


Toodleoo!
Ron Hebbard

RonHebbard said:

Soss Invisible Hinges; in sizes from tiny to MASSIVE with prices to match.
Sit down and be securely belted in place prior to Googling the pricing of their larger, heavier load-rated, models.

https://www.google.com/search?source=hp&ei=y69NXs24OovJgwfM2Le4DQ&q=soss+hinges&oq=soss+hinges&gs_l=psy-ab.3..0l10.724.4025..5026...0.0..0.212.1688.0j10j1......0....1..gws-wiz.......0i131j0i10.LeAlqvawXNQ&ved=0ahUKEwiNyse9zt7nAhWL5OAKHUzsDdcQ4dUDCAg&uact=5

Toodleoo!
Ron Hebbard

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Yeah, I use 6 of the BIG ones on my 'french doors' $40/each I think. Man I wish I could find pictures of that show.

Van said:

Yeah, I use 6 of the BIG ones on my 'french doors' $40/each I think. Man I wish I could find pictures of that show.

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Try $288 Canadian PER hinge and not even close to their larger / largest sizes.
Toodleoo!
Ron Hebbard

Van said:

Yep, That was my major concern with the french doors I did. Because they are mortised there is not a huge gap at the hinge jamb. Also the have a very low bevel angle when the open, smaller gap between the doors.
I laid the door in place on the stage to do the mark ups of where to mortise even.

Click to expand...

270? Seems like 180. And the center of the pin should be at plane of trap closed - so half of barrel. And a piano hinge can have a pretty small diameter barrel.

BillConnerFASTC said:

270? Seems like 180. And the center of the pin should be at plane of trap closed - so half of barrel. And a piano hinge can have a pretty small diameter barrel.

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Piano hinge barrels change size as the hinge changes size.
If you use the picture above as a starting point. The thickness or the facing, which is where you are going to attached the hinge, looks to be 5/4 or maybe 1 1/2". If you install a mortised piano hinge with a really small barrel you are only going to be in the top 1/4" of wood with the screws. The chances of pull out are way too high and , again, Look at a grand piano. When you lift the the action cover and fold it back over the top it does not sit perfectly flat with the with the top. There are rubber bumpers that keep it off the top for two reasons; one, no scratches, 2 no stress on the hinge. When the face of a door opens to 180° if you want it to rotate all the way flat you have to bevel the edge where the hinge is to keep it from scrapping.

Is it 180°? Yes. The Hinge opens through 270° because it's designed to do so. I apologize for miss speaking. The face of the door moves from a zero point, flat closed to a 180° point flat open.

If the point, as the OP asked is to have a hinge that doesn't stick up above the floor then the only option is to use a Soss hinge. If you trust your actors, dancers and other folks on stage to not trip on an 1/8" barrel sticking up through the floor, or if you can have a 1/2" wide gap at the middle of the two doors then by all means use a piano hing, a strap hinge, a back-flap hinge, a loose-pin back-flap hinge, or a piece of leather stapled across the edge of the jamb. Me? I'm sticking with having hung hundreds of doors on hundreds of sets and using what I've learned from real world experience.