What forces do flanged bushes on a door hinge experience?

[ghobbs]

Hi. I have a door mounted on 2 hinges, aligned on a vertical axis. The hinge shafts run in flanged plain bushes.

I'm trying to work out what forces the flanged bushes will see. The door weighs 100Kg, with the centre of mass at the centre of the door. The door is 2m wide and 2m vertically between hinges.

I think that the flanges will see the mass of the door, i.e. each flange sees 500N.

The bushes will also see radial forces, counteracting the moment of the door about the hinges. Based on the moment and geometry, will the top bush see 1000N and the lower bush -1000N?

 

[CWatters]

my experience is limited to hanging a field gate. In that case its impossible to get both hinges to share the load because they are never the same distance apart. One or the other "bottoms out" first and carries the vertical load.

 

[sophiecentaur]

As CW wrote, only one of the hinges will have a shear / vertical force on it but the upper hinge will have a force outwards and the lower will have a force inwards. This simple setup gives the horizontal forces as + and - 500N, assuming the cm of the door is half way between the levels of the hinges the total moment being 1000Nm and each hinge provides half the necessary torque against this( 500+500, one way = 1000 the other way). Unless you have some resilience in the hinge mountings plus some way of fine adjustment of the vertical height of the hinges, you can't be sure which hinge will take all the additional vertical load of 1000N.

 

[ghobbs]

Ah yes, I understand now. Thanks for the clarification.