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Almost every door needs to be either open or closed, rarely do we need it half open. Since the doors (not the band) in my home are old, some of them tend to open or close automatically because their hinges are loose or slightly rotated. So some doors tend to open/close and usually not as desired.

I want to create a mechanism that will force the door to go towards its nearest position (open or closed). Something like this:

When door is left in the open area, it should open (even slowly) and stay there, and the opposite when it is left in the red area. I don't care if it will completely close, but at least be moved to that end.

Door position

Specs:

  • The mechanism should be nearly silent
  • It should be cheap (less than 25e/30$)
  • Should be installable to the existing doors.
  • I don't care if I'll have to drill door/floor or case.
  • It shouldn't use electricity. Only mechanical power.
  • I don't want to use door stoppers, this is the obvious solution.

I have considered somehow using strong magnets (I have several from broken hard disks) in order to move to the nearest end, but since I'm not an engineer I cannot come up with a design. Any ideas?

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If you're trying to design a new product, you should hire an engineer. –  Tester101 Jul 15 '13 at 12:30
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2 Answers 2

The best approach would be gravity self closing hinges such as these

gravity hinge

These are designed to close the door, regardless of the angle of position.

What you need is the same type of device, but one where the high point of the lower section is at the midpoint of the swing. On one side of the midpoint, the door would swing in, on the other swing out.

As far as I know, no such versions are commercially avaialble. If you are handy and have the tools, you could gring the adjoining faces of such hinges down to create the right "tip point". Note that the door needs to rise and fall a small amount to make this happen.

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These are great hinges and a good solution for new doors if you can find that mechanism in desired style, size and duty-range for doorway doors. Would also be a good solution for existing doors with more stringent caveats, which if not met would require one to deepen or shim the mortise for non-matching leaf thicknesses, and fill mortises if leafs are smaller than existing. But if it comes to that, might as well accomplish it by good craftsmanship. –  mike Jul 15 '13 at 2:10
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Doors tend to open or close automatically not because their hinges are loose or slightly rotated, but because their hinge pins are not plumb. The doors could have been hung that way intentionally (or not), or their walls could have tilted as the house aged.

To have a door move on its own to the nearest open/closed position, the center of mass of the door needs to be at its high point when the door is at threshold for open/close, which in your diagram would be 60 degrees.

Imagine that the dark line at 60 degrees in your drawing is a vertical geometric plane strecthing from floor to ceiling. Both (or all 3 if that is the number) of the hinge pins must be in this plane, with the lower hinge pin 'sticking out' into the room. Thus hung, a free swinging door in a room with no significant air drafts will behave as you desire.

To accomplish this, you may need to do one or both of these:

A) shim between the hinge leaf and its mortise in the jamb

B) move the hinge screws left or right by filling the screw holes with wood splinters/dowels + glue and then re-drill pilot holes the the left or right of the previous holes.


Some ideas for shimming are:

1) A couple layers of duct tape on the back of the hinge leaf.

2) A layer or two of paperboard or non-corrugated cardboard scavenged from discarded packaging.

3) Simpson tie plates, trimmed to fit.

4) Apply spots of a thick spackle or wood filler, then install the hinge leaf, compressing the filler to achieve an exact fit. To prevent the hing from adhering to the spackle, a) wax the back of the hinge leaf with a candle, or b) use a layer of kitchen-type wax paper, or c) wrap the leaf with kitchen-type plastic wrap. When dry, remove the the hinge leaf and fill any voids with additional spackle.


Note 1: The farther 'out into the room' the lower pin, the greater the driving force.

Note 2: The heavier the door, the 'closer in' the lower pin can be to achieve the same opening/closing force.

Note 3: For uncommonly tight hinges, the door will swing freely only if the hinges are mounted such that the pins are co-linear as well. A bit of lubricant on the pins may help in this regard in intermediate cases.

Note 4: For walls/jambs that are severely out of plumb, the jambs themselves will need to be first reset to plumb.

Note 5: 1972 Patent for Center-of-Mass Hinges

http://i.stack.imgur.com/zZcZU.png

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Great answer. I did this with a baby gate at the top of the stairs. –  Evil Elf Jul 15 '13 at 15:22
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