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NELUG recently participated in the LEGO Roadshow. We decided that we wanted
to do something special for the event, so we built a fully automated quarry
scene that had working vehicals with a Rube-Goldberg feeling to it where
"gravel" would continuously flow around the display.
THE SYSTEM
Every system is made up of smaller parts. Before going into the specific
pieces, it's helpful to know what the system is suposed to do. This link
shows the original layout that we went for:
http://www.brickshelf.com/cgi-bin/gallery.cgi?i=456740. While we ultimately
made changes to the quarry, especially in terms of the conveyor system, we
generally held fast to the basic flow of the "gravel." We decided the flow
would be:
1. Start with gravel in the Canister (yellow cilendar above the shovel)
2. When the shovel scoops, dispense gravel into the shovel's bucket
3. Turn shovel 180 degrees and dump contents into the dump truck
4. The dump truck will then backup, wait for the bulldozer to be in position
and then dump
5. The bulldozer will then puck the gravel to the end of the path
6. Upon receiving the gravel from the bulldozer, the conveyor system will
start up and deliver teh gravel back up to the canister
7. The process starts all over again.
While originally the bulldozer was simply going to push the gravel onto a
conveyor at the end of the path, we ultimately used a lift that dumped the
gravel into the conveyor. We're not really sure why we made this change,
but we had precious little time in which to design and build this (about 5
weeks), so we simply worked with what was there.
Video of the quarry (note that it is nearly 20MB in size):
http://www.peeron.com/pics/nelug/RoadShow-20030713/?pic=mov02119.mpg
General picture:
http://www.peeron.com/pics/nelug/RoadShow-20030713/?pic=dsc02092.jpg
COMMUNICATION
The various pieces of the system needed to speak to one another, so we
devised a system that used the Infrared (IR) messages of the RCX's along
with a number of touch sensors. If we had more initial design time, we
could have nailed down some issues before we started building the specific
pieces and we most likely could have just used the IR messages alone. But,
since some of the equipment is dumb and some is intelligent, we needed touch
sensors in certain areas to make the intelligent pieces even smarter to
account for their less intelligent counterparts.
The following message ranges were used:
* Canister 10-19
* Lift 20-29
* Dump Truck 30-39
* Bulldozer 40-49
* Conveyor 50-59
* Shovel 60 -69
CANISTER
Picture: http://www.brickshelf.com/cgi-bin/gallery.cgi?i=456640
The canister is what holds the gravel and will dispense it once the shovel
"scoops" it up. The canister is responsible for telling the shovel when it
can start a cycle by issuing the "start cycle" message. The canister
monitors a touch sensor that is attatched to a lever embedded into the cliff
face. The shovel's arm will hit this lever and the canister will issue the
"gravel release hit" message. The canister then dispenses the gravel by
turning a blade that allows the gravel to fall out the bottom of the
canister, down a ramp and into the shovel's bucket.
The canister also monitors the conveyor. Once the conveyor stops, the
canister knows it should be full. Once this event occurs and the shovel
sends its "shovel done" message, the canister will issue the "start cycle"
message again.
SHOVEL
Scooping: http://www.brickshelf.com/cgi-bin/gallery.cgi?i=455331
Open Bucket: http://www.brickshelf.com/cgi-bin/gallery.cgi?i=455332
The shovel doesn't do anything until it receives a "start cycle" message.
Once it does, it raises its arm until it sees a "gravel release hit"
message. This message is sent by the cannister. At this point, the shovel
pauses for 2.5 seconds to ensure the gravel has enough time to fall into the
bucket and then rotates 180 degrees (determined by a rotation sensor). The
shovel issues a "dump truck ping" to ensure it is there. When it receives a
response, the shovel will then open the bottom of the bucket and drop the
contents into the back of the dump truck. Upon closing the bottom of the
bucket, the shovel issues a "bucket closed" message. The shovel then
returns to it's starting position by lowering its arm and turning back 180
degrees. Upon completing this, it issues a "shovel done" message.
The shovel's actions are:
* Raise/Lower Arm
* Turn shovel Left/Right
* Open/Close Bucket
DUMP TRUCK
Waiting to dump: http://www.brickshelf.com/cgi-bin/gallery.cgi?i=456638
Dumping: http://www.brickshelf.com/cgi-bin/gallery.cgi?i=455333
The dump truck does not have an RCX embedded within it like the shovel does.
The dump truck's RCX is hidden within a rock outcropping. but has it's IR
port exposed. This RCX is responsible for driving a single motor (used to
make the dump truck move back and forth), a rotation sensor (to determine
it's relative distance) and three touch sensors. Now you may be wondering
how or why we have 4 sensors on one RCX.
The dump truck RCX uses two touch sensors "chained" together so that it
knows when the dump truck is either at its back most (dumping) or front most
posistion. Since the dump truck can't be in both places at once, this isn't
an issue. The other touch sensor is for detecting the back position of the
bulldozer which will be descussed shortly.
Once the dump truck sees the "bucket closed" message from the shovel, the
dump truck will back up *near* the cliff, but not so far as to dump. It
does this by using the rotation sensor to know roughly how far along it has
traveled. It does not have to be precise, just near enough that it can dump
in a short amount. It then waits until the bulldozer is in the back most
position and then it will dump the gravel down the cliff. The dump truck
does this by then backing up until it hits the first of the chained touch
sensors and the continues on for .75 seconds causing the back to lift up. A
"dump truck dumped" message is issued. Once this is done, the dump truck
then returns to its starting position, which it knows by hitting the 2nd of
the two chained touch sensors. When this is complete, it issues a "dump
truck ready message."
The dump truck's actions are:
* Move Forward/Backward
* Dump
BULLDOZER
Bulldozer: http://www.brickshelf.com/cgi-bin/gallery.cgi?i=455318
Back sensor: http://www.brickshelf.com/cgi-bin/gallery.cgi?i=456643
The bulldozer is actually completely dumb in that it doesn't know anything
that is going on around it, nor even what it is doing. The ability of the
bulldozer to lower the blade, march down the path for a given distance,
raise the blade, and march backward down the path for a given distance is
done completely through mechanical gearing. While this is quite ingeneous,
it creates a communication issue for the pieces in the system that are
before (the dump truck) and after (the lift) the bulldozer. To account for
this, a touch sensor that senses when the bulldozer is in the back-most
position is connected to the dump truck's RCX (see above). Another touch
sensor that detects the bulldozer's forward-most position is attached to the
Lift's RCX (see below). Aside from these sensors, the bulldozer simply
moves back and forth blissfully unaware of what it is doing.
The bulldozer does have a trench in which it operates in order to keep the
bulldozer straight and also to catch the gravel that is dumped over the
cliff by the dump truck.
The bulldozer's actions are:
* Raise/Lower Blade
* Move Forward/Backward
LIFT
Forward sensor & Lift:
http://www.brickshelf.com/cgi-bin/gallery.cgi?i=456641
The lift waits for the bulldozer to get to its forward-most position and
back away before starting up the conveyor system (see below). It does this
by using a touch sensor that is both touched and released by the bulldozer.
It is the releasing of the touch sensor which triggers the following
actions. The lift then will raise 90 degrees causing gravel to fall into a
downwards ramp. The ramp is then vibrated to encourage the gravel to slide
down. The lift returns to its initial position and waits for the bulldozer
to hit the touch sensor again.
The lift's actions are:
* Raise/Lower Lift
* Vibrate Ramp
CONVEYOR
Bottom conveyors: http://www.brickshelf.com/cgi-bin/gallery.cgi?i=455346
Main conveyor:
http://www.peeron.com/pics/nelug/RoadShow-20030713/?pic=dsc02085.jpg
Once the conveyor is turned on via the lift, the conveyors will stay on for
approximately 30 seconds, shuffling the gravel up one conveyor, down a
sideways ramp into an horizontal convery to another sideways ramp to the
main conveyor which brings the gravel all the way up to the top and into the
canister. If this sounds more complicated than necessary, you are correct.
Our initial design did not have the sideways movement of the gravel nor the
lift and we could eliminate one entire conveyor and all sideways movement if
we eliminate the lift and have the bulldozer simply push the gravel to the
end and onto the first conveyor. But funny things sometimes happen when you
are under tight tme constraints and backing way from some things sometimes
can cause more issues.
The main conveyor (the large black one) has a ramp a the top which allows
the gravel to slide into the canister. It also has a rotation sensor in it
that allows to canister to know when it is operating and, just as
importantly, when it stops (see Canister section).
While it may seem that the conveyor system would be the easiest thing to
construct, it is safe to say that it took as long to design and "perfect" as
any of the other pieces. Creating a conveyor that can reliably move
material any appreciable distance turned out to be quite tricky.
The conveyor system actions are:
* Start/Stop Conveyor
GRAVEL
While we always intended to use 1x1 plates as gravel, as we began testing
how well the various pieces worked with the 1x1's, we realized that certain
pieces of the quarry could handle different LEGO elements better than
others. We though for sure at one point that we were going to be using half
bushing due to their round nature and abundance. However, as we refined our
creations, we were able to make the 1x1 plates work and so stuck with that.
HINTS
Lastly, just some tips if your LUG (or LTC) is interested in developing a
similar project. As they say with every project in the universe,
communication is the key - and that's communication between LUG members
we're talking about! The more everyone is on the same page, the easier it
is to adjust things and make changes. Since it is a system, any time one
thing changes, no matter how small it may seem, it *will* affect someone
else. Always remember what you need from one piece and what you must give
to another, if you change something, they will most likely have to change
too.
If you can define a general "communication scheme" for your devices up
front, you will also benefit greatly. NELUG ended up running off and
building the major pieces of the quarry (the shovel, bulldozer, conveyors),
but didn't really know how they were going to talk to one another. We
obviously solved this, but if we knew this up front, we could have spent
less time integrating the pieces and more time fine tuning them.
Think things through. The simpler you can keep things, the more dramatic
and reliable your end result will be. This cannot be understated.
Finally, have a blast! It really is the *coolest* thing watching it all
work. The visitors to the roadshow absolutely loved it (as did we). The
possibilities are endless and it is just too much fun.
- Joe
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Message has 4 Replies:
 | | Re: Quarry
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| "Joe Comeau" <joecomeau@earthlink.net> wrote in message news:HI1BH8.1BG@lugnet.com... (...) wanted (...) quarry (...) Beautiful execution! Very well done! (21 years ago, 15-Jul-03, to lugnet.org.us.nelug)
| | | Re: Quarry
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| (...) Amazing. Absolutely amazing. The video complements the description nicely. Cheers Richie Dulin (2 URLs) Port Brique Somewhere in the South Pacifique (2 URLs) Misérable Building a safer South Pacifique (21 years ago, 15-Jul-03, to lugnet.org.us.nelug, FTX)
| | | Re: Quarry
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| I remeber seeing a very similar thing to this in the mid-late eighties at the (UK) model engineering exhibition. They used the technic vehicles straight from the sets i.e. (2 URLs) as well as a conveyor they made. I'm not certain how they did the (...) (21 years ago, 15-Jul-03, to lugnet.org.us.nelug, FTX)
| | | Re: Quarry
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| WOW!!! Deep bow! Hats off! Duq "Joe Comeau" <joecomeau@earthlink.net> wrote in message news:HI1BH8.1BG@lugnet.com... (...) wanted (...) quarry (...) <snip> (21 years ago, 16-Jul-03, to lugnet.org.us.nelug)
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