Mechanical engineering in SL

Hi all. I do not have a problem this time, but are seeking others with this strange interest.
SL has a physics engine, which seems more "powerfull" in some ways than I thought. So I have been playing with "mechanics". I have managed to make the following contraptions:

A "water wheel" - a big physical wheel which is suspended on two non-physical pillars. The wheel has baskets on the outer rim, and a small box above the wheel to the side will produce a stream of balls which will then end up in the basket. Thus, the wheel becomes heavy on the one side, and the physics engine make the wheel turn. When the basket reaches the bottom of the wheel it has turned so much that the balls fall out. Same principle as a real waterwheel, only done using balls as I have no water. It is chunky and it stalls at occasion, but in general it works.

B "simple gears" I have a gear with 8 spikes which drives an other wheel with 16 spikes.

C "worm drive" Using prim torture one can make a worm drive which then drive a normal gear.

You are welcome to visit the contraptions on "Splendour/52/118/3020". Look for the red part in the three - a touch should start them - please turn them off again by touching a second time.....

I have not been able to find anything like this in SL, but I guess my glasses have just not been good enough. If you are interested in making such gadgets send me an IM so we can help each other out.

Also, it seems like physical objects hover above non-phys objects at a distance of 12-14.5 cm. Does anyone know any way to predict this distance? This distance is the reason while all my gears are suspended in hollowed out discs. My experience shows that a hole size of about 2*15 cm is suited (when using a 1cm shaft). Also the disc need a certain thickness for the physics engine to do its rounding errors without the gears falling apart.

Any fellow builders of "amazing machines"???

Since windlight & all these clouds, I'm doing a lot of kite flying, trying to discover electricity
Kyte flying? there's an idea someones probably already done
Otherwise, when can we get a "lighter than air" material to make prims from, would be interesting idea, good for blimps, baloones etc and reversing your physics engines

llSetBuoyancy(1.1) makes things lighter than air Even big things of Stone

Cool, have to try that, what would happen to a balloon if It kept going up, returned at 4096m or just stay there drifting around sims forever?

There is a limit at 4096m for prims - but if there is a link between the object and an avatar the limit is the value of a floating point. I tried to go to 320 km once using the buoyancy method - it took some hours.

There is nothing up there but rounding errors. First I turned black, then spiky, and the flyscript in my glasses broke for some reason. To get my clothes and skin back in order I had to clear my cache as well.

Well I was thinking of sending the balloon by itself, who cares if it takes a week

you mean like these?


http://www.youtube.com/watch?v=mxark62X63w

http://www.youtube.com/watch?v=mCrJBSCZbdE

can we use it to power a car?

In Havok 1 at least, machines like marble runs and worm gears and so on would generally tie the poor physics engine in knots, and the performance of the sim would suffer. Havok 4 apparently still doesn't deal with friction very well, it's more concerned with objects colliding with each other and bouncing off. I hadn't heard about people trying these things again though, good to hear you've had some success!

Wow, I'll take a look.

I tried some simple gears, but they "jumped' the bearings and shot across the landscape.

No trebuchet???

Trebuchet was my first thought.

I did see some folks in a sandbox once playing with a gravity-driven catapult. Dropping balls on a lever and sending each other up in the air. More height than distance, but it was successful.

I made a Newton's cradle a while back. Catapults are quite good fun too! I think it is also possible to make a windmill that reacts to the wind, but I've never seen a fully working model.

I seen a working physics driven trebuchet that worked quite well. Tossed any object positioned in the tossing end. also had pre-loads like cow, flamingballs and even flaming cows. Tossed my AV a map and half's distance.

I messed around with that for awhile, except I was making one of those circus acts where one person jumps on one end and launches the other person. it was fun.

The biggest problem was keeping the launch lever from flying off the sim.

Oh yeah - forgot to mention earlier, in case it is not obvious to all readers, these contraptions can hammer the physics FPS of the sim, so it is brilliant that Boreal's displays have an off button!

Hmm thats a worry considering how simple they are and what could be built

not to forget, a significant part of machines' problems in SL is the ACTUAL geomtry of the parts.

A circle is actually a hexagon. So an axil made of many thin rods will present fewer large jaggies (friction) to any surface it encounters. But then it's presenting them more often. The physics engine then has more work(and more chance for catastrophe)

Isn't that the best part of a trebuchet, watching it all go horribly wrong and taking out the crowd instead of tossing prim cows at neighboring sims??

quite!!!


but explosion physics are old school too. The topic i believe is workable machines. But if you have a spare nuke i could put it to better use than mearly getting seizmic readings from it. Anyone up for EXTREEMLY high pressure/tempurature materials production?

i made a perpetual motion wheel in client 1.2 and it spun faster and faster till it exploded
i should try it again in havoc 4

Zen Zeddmore says that friction might be reduced using multiple rods rather than a single. Any idea of the actual effect?

Also, I can not determine the actual magic bounding box distance. It seems to be that two physical objects fly somewhere between 12 and 14.5 cm above each other, but I cannot figure out what determines this distance - and guesses. It would be nice to be able to calculate the opening necessary in around the axis in a bearing.

Also, I have experienced the "exploding gears" that Beezle Warburton mentions. I deal with it by letting the room for the axis be 15 cm wider rather than the approx 14, and by letting the material around the axis be at least 1.5 times as thick as "axis diameter+2*15" cm. Seems to work most of the time. But I have had to come and fix my exhibition a few times (you are still welcome .

Also, remember to make axis and bearings in "glass" as it has the lowest friction.

A Trebuchet - wow - I should love to be hauled across multiple sims - I'll pay 10L$ per ride

And thanks Zen Z for the vid refs. Other mechanics out there.....

There's a 10cm distance between physics objects.

[11:26] Andrew Linden: the collision tolerance is a fixed size 10 cm

from:
http://wiki.secondlife.com/wiki/User:Andrew_Linden/Office_Hours/2008_04_08

Hmm, yes, that I can verify by experiment in the case if it is a box on a box. But if it is a cylinder on a box I get 9.6 this morning. And with other shapes and constructions I get other numbers. Presumably it can be something with when the physics engine stops simulating and decide it has reached a stable configuration.

How you're altering the amount of friction by changing the material I wish I knew. So far as I know all those material changes do are change the collision sound effect, they are a redundant feature of a previous experiment with physics that never worked and were consequently left out. I could be wrong but so far as I know thats the case.

You can make levers, but they are likely to jump out of their hinge, so they are single-use only beyond 1 meter length.

Even havok4 has the problem that, if enough force is applied, you can push a solid object trough another 3 meter thick solid object.