how can i set up multiple pulleys to raise & lower a set of doors that are hinged at the top & bottom?
481826
I can think of two ways. First is with counterbalence weights with the doors balanced seperatly. For the bottom door think drawbridge with weight(2x door mass)  attached to pulley to get more travel in door.Same for top. depending on space limitations several pulleys might be needed to keep weights where they can moove. \nYou might try garage door springs. look at the pulley setup for single garage door with old pulley/ spring setup instead of the new torsion spring.\nSecond way is harder to describe. Starting at the top hinge create an attachment point 90 deg from door same distance as door length. Imagine a big carpenters speed square bolted to the upper doorwith 90 deg. angle(pivot point) at top hinge. Now with both doors closed, working from inside, make a connection with a stiff rod, angle iron, from furtherest point of speed square on top door to top edge of bottom door. When the top door is pulled up the rod pushes the bottom door down with equal force and distance.
230952
a compound machine would involve multiple mechanical devices.  For example a pulley connected to a lever which is connected to a gear system would be a good example.  This would be used possible to mechanically lift a load.
1104231
Pull it back up.  What else could I do?
355815
Move things according to your mode???  I'm with the previous poster on this one.
140612
Yep.  A fan will do the trick, or if it's a vehicle used for a specific purpose (like carrying something from set point A to set point B) a pulley system would work.  I don't know the exact equations involved, but the fan's windpower strength should be (obviously) greater than the mass of the vehicle, and should have some kind of failsafe cutoff switch as well as a means to decrease power to the fan, for (again, obviously) safety reasons.
815263
Buy powertools, and use the "Boss Button"
102578
http://home.howstuffworks.com/combination-lock.htm
997307
hey go buy a pull up bar for the doorway
1055896
The probablity that u need to try 4096 combinations is 1/4096. 4095 times u ll be able to open it in lesser number of tries.\nu cant do it  for certain in lesser comb always unless you have some other information about the state of locks or use some other source to obtain it.\n  lookin at ur q's it seems u really get screwed opening doors ..12 locks ...remote inside ,, :)
652413
Engineers use a cable and pulley system to pull the cables that are on the ground up to the insulators on the very tall towers.  Then they pull the cables at the end of the respective run to tighten them to specifications.
272672
Number of rope segments. only if the last segment rope us pulled upward
482721
http://en.wikipedia.org/wiki/Toggle_Mechanism
679226
on a lot of doors you can slip a butter knife in between the door and the frame and get down to where the latch is and slip the knife down and pry the little thing that holds the door shut so then you can open the door.
160606
try to select the second item from the top that would work
682732
Make sure the toolbars are unlocked.  View > Toolbars and make sure Lock the Toolbars is unchecked.\n\nDouble click on the name of the toolbar in Explorer ie. Links, Address and make sure you hold down the mouse button on the second click while dragging it to another location.\nIt takes practice.  You can move them up or down or resize them by positioning the mouse cursor over the lines delimiting the toolbars (two or even three bars can be put at the same vertical position and unnaccessible links will be accessible using the >> double arrows in a drop down fashion).\n\nWhen you get it like you want it make sure you 'Lock the Toolbars'.  That is why they came undone from your layout.  It's an easy mistake to make.
909305
you might try a figure 8 knot, or a stopper knot.\n\nhttp://www.chockstone.org/TechTips/Stopper.htm
745227
Generally simple machines include levers, wheels and axles, belts and pulleys, gears, and inclined planes.   This site should help you.  Best of luck with it.