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[Sphalerite]

Step 1:

Created two five-by-five bridges, each surrounded by a five wide moat of smoothed floor and a wall.  The bridge on the left side is a retracting bridge.  The bridge on the right side is a drawbridge raising to the north.  Both bridges are linked to the lever to the north.



Step 2:

Temporary platforms were constructed above each bridge, covered with bone stacks, and then deconstructed.  This left both bridges covered with obsidian blocks and stacks of bones.  A few of the bones did evaporate during he process due to the experiment taking place aboveground.



Step 3:

The lever was pulled.

Blocks and bones were flung off both bridges.  Objects flung off the retracting bridge on the left moved a few squares in a random direction, the furthest of which landed 3 squares from the bridge.  There did not seem to be a consistent difference in distance of travel between the blocks and the bones.  Objects flung off the raising bridge on the right also appeared to travel in a random direction, but the wall created by the raising bridge prevented any blocks from landing on the north side of the bridge.  A few of the blocks thrown by the raising bridge flew 5 squares away to land against the containing wall, but the majority traveled no further than those thrown by the retracting bridge.



Step 4:

The lever was pulled again to lower/extend the bridges.

Objects under the retracting bridge on the left which were still within the footprint of the bridge were thrown a few squares.  The direction was random, and the distance appeared to be comparable to that when the bridge raised.  Objects already outside the footprint of the bridge were unaffected.

Objects under the lowering drawbridge were disintegrated instantly.  Objects outside the footprint were unaffected.



Conclusion:

Both retracting and raising bridges throw objects resting on them when retracting.  The direction of travel appears to be random in both cases, but the wall created by the raising drawbridge will tend to block objects from moving off the bridge in that direction.

There does not appear to be a consistent difference in the distance which objects travel after being flung by the raising bridge versus those flung by the retracting bridge.  The furthest objects thrown by the raising bridge traveled further than the furthest objects thrown by the retracting bridge, but it is not clear from this trial if this is random or a consistent difference.  Further trials will be needed.

Retracting bridges, when extending, produce an object-flinging effect similar to that created when they retract.  Lowering drawbridges, of course, do not.

[Kanddak]

Well-done.

I have occasionally observed objects thrown to a higher z-level by raising bridges, so it would be interesting to see this experiment performed with the bridges in holes to see whether this is the same for retracting bridges.

[Hamster Man]

While I admire your dedication to the scientific process of Dwarfology, I still think you've got too much time on your hands. But regardless, that is an interesting observation - were you running this to see which would be more effective for defensive purposes, or just curiosity?

[Jim Groovester]

The advancing of Dwarven Science needs no reason!

...although it gets advanced more quickly if it kills something.

Hmm. As a next test, you should try creatures. Kittens, puppies, goblins, whatever.

We need to know the flinging behavior of bridges in regards to creatures. For purely scientific reasons, of course.

[2xMachina]

Well, I've got something for you to test.

Code: [Select]

c===
 | |
c===

Where c is a chain, with a dog attached. Said dog decides to stand on the bridge. What happens when the bridge is raised? Does the dog fly? If they do, could they fly away from the chain? Would the chain break? Or would the chain break their neck?

[Sphalerite]

I have occasionally observed objects thrown to a higher z-level by raising bridges, so it would be interesting to see this experiment performed with the bridges in holes to see whether this is the same for retracting bridges.

Although this experiment wasn't set up to test Z-level travel by flung objects, I have seen objects on retracting bridges wind up on top of walls next to those bridges.  I'll have to do a controlled experiment to see if it happens to the same degree with raising and retracting bridges.

While I admire your dedication to the scientific process of Dwarfology, I still think you've got too much time on your hands. But regardless, that is an interesting observation - were you running this to see which would be more effective for defensive purposes, or just curiosity?

Mainly curiosity, I wanted to understand the physics involved, but there are applications to fortress defense.  Most of my fortresses use some variant of retracting or raising bridges over magma, drowning chamber, deep pits, or other death trap mechanism for defense.  I've seen invaders on retracting bridges flung to safety when the bridge retracted.  I've also been curious if there's a practical way to design an automated conveyor belt system using bridges.  Haven't come up with one yet, but it would be possible to use an array of automatically repeating retracting bridges as a sort of dwarven Pachinko machine

[Sphalerite]

Experiment #2:  The effect of bridges on chained and unchained animals.

Five iron chains were placed on the southern edge of each bridge, and a cat was chained to each.  A channel was dug around the chains to encourage the cats to stand on the bridges.  A meeting zone was placed in the center of each bridge, and a few additional loose animals sent in to stand on the center of each bridge.



The lever was pulled.

All animals on the bridges were flung.  It does appear that animals standing on the raising bridge were flung further than those on the retracting bridge, with most of them traveling all the way to the containing walls around the chamber.  Creatures on the retracting bridge only traveled 2-3 squares.

The direction of travel of thrown creatures was random for both bridges.  As in the previous trial with objects the raising bridge blocked any creatures from traveling in the direction the bridge raised.

Every chained cat standing on the bridge was removed from the chain when the bridge was raised or retracted.  The chains still listed a cat as assigned, but not chained.  None of the cats had any injuries, nor did any of the other animals involved.



Conclusion:  Both raising and retracting bridges throw creatures standing on them in a random direction.  Raising bridges appear to throw creatures further than retracting bridges.  The direction of throw is random.  Chained creatures will be removed from their chains when thrown.  Chained or unchained, creatures are not harmed by being thrown, assuming they land on a safe location on the same Z-level.

[WhatDoesThisLeverDo]

If the above is true, you could "release the hounds" so to speak 

[Iapetus]

Some observations of my own which may be useful (but aren't part of any quality-controlled experiment):

In my current fortress, I attempted to set up a forced swimming training program (I have a carp-filled river right outside my front door, so swimming ability is a potential life-saver).


My training pool consists of a 7 x7 pit, with ramps all round the edge.  I've built a retracting bridge over the top, linked to a leaver, and designated a 5x5 meeting zone in the centre of the bridge.

Periodically, when a large group of dwarves congregated on the bridge, I ordered the leaver pulled.  When this happens, the dwarves are flung in a random direction, with most beig flung off the bridge, but some dropping through into the water.  I don't know if this is because they were randomly throw a short distance (not far enough to get off the bridge), or if some automatically drop through a retracting bridge if it has empty space under it (although it probably doesn't make any difference in practice).

[Sphalerite]

Experiment #3:  Z-level movement of thrown objects.

The bridges and chains used in the previous experiment were deconstructed.  Two 5X5 pits were dug, each one Z-level deep.  On the floor of the left-side pit a 5X5 retracting bridge was created.  On the floor of the right-side pit a 5X5 north-raising drawbridge was created.  Both were linked to the lever to the north.



As in the first experiment both bridges were evenly covered with blocks and bones.



The lever was then thrown.

Objects were observed to fly up out of both pits and land on the surrounding floor.  More objects seemed to fly out of the left-hand pit (with the retracting bridge) but it is not clear if this is a consistent difference or merely random chance.  The distance objects were thrown seems similar for both bridges.  The direction objects were thrown appeared to be random.  No objects were observed thrown out of the north side of the pit with the north-raising drawbridge, but with the small number of objects ejected from that pit it is not clear if that was random chance or if objects thrown upward are prevented from moving in the direction the bridge raises.



The lever was then thrown again.  The extending bridge in the left pit again threw objects up on to the surrounding floor.  The number of objects thrown and the distance traveled was comparable to that thrown when the bridge retracted.  The lowering drawbridge in the right pit did not throw any objects as it lowered, instead destroying any objects in its path.



Conclusion:  Both retracting and raising bridges can throw objects at least one Z-level upwards when they retract or raise.  Retracting bridges can also throw objects upwards when they extend, to a similar degree as when they retract.

[Sizik]

You should test how bridges fling items if there is space under them.

[Duuvian]

How about the effects on military dwarves? Or if the length of the bridge effects the distance thrown? Would they make it over a wall? (and maybe into the goblins beyond)

[Hamster Man]

While I admire your dedication to the scientific process of Dwarfology, I still think you've got too much time on your hands. But regardless, that is an interesting observation - were you running this to see which would be more effective for defensive purposes, or just curiosity?

Mainly curiosity, I wanted to understand the physics involved, but there are applications to fortress defense.  Most of my fortresses use some variant of retracting or raising bridges over magma, drowning chamber, deep pits, or other death trap mechanism for defense.  I've seen invaders on retracting bridges flung to safety when the bridge retracted.  I've also been curious if there's a practical way to design an automated conveyor belt system using bridges.  Haven't come up with one yet, but it would be possible to use an array of automatically repeating retracting bridges as a sort of dwarven Pachinko machine

I believe, based on your previous experiment, that retracting bridges with no open space under them make operate like this. I propose you design an experiment with multiple retracting bridges, lined with walls on both sides, and see how many objects make it from the first bridge to the last bridge.

(Edit) And, if you used a raising drawbridge to form a wall at the "start" end, you could set the flipper on repeat and eventually ALL objects should make it to the end bridge, right?

[Heliomance]

Assuming an infinite amount of time, every object will occupy at some point every possible position. This chain can be interrupted by falling off the end of the chain, so assuming an infinite amount of time, every object will indeed make it off the end. In any finite period, however, there is no guarantee that this will happen. An object could, for example, be batted back and forth between two bridges ad nauseum.

[winner]

is it possible for a extending drawbridge to push things into a lower z level?

lets say you had a 3x3 retracting drawbridge and 8 of it's nine spaces were channeled out. If you put some items on the 9th space and lowered the bridge would they end up around the bridge or under it?