Sunday, June 26, 2011

How the Pancake Bot Works

The Pancake Bot (PB) is basically a 3 axis CNC made that uses the Z coordinate as the Pancake Batter Dispenser Control. This one just happens to be made out of LEGO.
The Pancake Bot is made up of the following parts:

1.  A set of linked base plates with 3 parallel tracks snapped on.  One track has a bunch of Technic, Gear Racks (1 x 4) riding along top which makes up the X axis.

2.  A moveable bridge that holds one NXT motor on one side and has free rolling wheels on the other.  The top of the bridge uses two tracks covered with gear racks that holds the Pancake Batter Dispenser Unit (BDU).  The track allows for Y Axis Control.

3.  A carrier gantry on top of the moveable bridge that rides on the gear racks and holds the PDU.

4.  The PDU consists of two ketchup bottles cut in half and glued together so you have two open ends.  This allows you to change the nozzle size on the bottom and allows for input of compressed air on top.

5.  Compressed Air Dispersal Apparatus (CADA) consists of an NXT Motor, two Pneumatic Cylinders, a tank and a bi-directional flexible switch.

The bi-directional flexible switch allows for the switch to be flipped based upon which direction the NXT motor turns.  If you notice in the video, on the close up of the motors turning, the cam is switching the flexible switch every time it rotates.  In the initial turn, the switch is flipped and stops and then continues to flex out of the way of the rotating cam.  When the motor turns the other way, the cam catches the switch, flips it back and changes the direction of the airflow.  It continues to flex as the cam passes over it.  This allows for air to be compressed when the motor turns clockwise, and then the air to be released when the motor turns counter-clockwise.
The reason I did this is because I only have 3NXT motors and needed to a way to change the direction of the air flow while at the same time, still compressing air.

The Program
Originally, the goal was to control this with Python NXT, an open source programming interface developed by Marcus Warner and the Python NXT group.  It worked like a charm at first but for some reason, I could no longer communicate with the brick, so I went back to using the less flexible LEGO Mindstorms programming.

The program itself is a variant of the the Etch-A-NXT program found in Extreme NXT, by By Michael Gasperi, Philippe E. Hurbain, and Isabelle L. Hurbain.  The original program just controlled two motors using an external text file.  I modified the program by adding the third motor.

The text file needed to draw with the Pancake Bot uses three coordinates, each with a character return afterwards.


This tells the NXT to rotate Motor A 360 degrees, Motor B 2400 degrees, and Motor C 500 degrees conterclockwise.  Depending on which gears you choose, one rotation can equal different numbers of units of movement.
I used the 8 tooth gear which with one rotation, moves 4 standard LEGO units.
Depending on the size of your electric griddle, you can calibrate how big you want your drawings.
A simple program in XL converts the LEGO units into degrees and outputs the text file.

Motor C in this case is the Z axis which controls the BDU.  It also acts as a timer for discharging the batter.

The parts that are exposed to the heat of the griddle are covered with a sheet of aluminum foil during cooking.  This reduces the chance of parts melting.

Making the batter.

The batter is made using Martha Stewart's Basic Pancake Recipe as the base.   I sometimes add cinnamon or different berries for flavors or color.
Once the batter is made it goes through a strainer and all the clumps are removed.  This makes the batter smooth and allows for continuous flow of the batter from the BDU.

Things to work on!
The BDU is not the best design but other attempts were not as successful for batter delivery.  I attempted using a standard RCX motor with a corkscrew that went to a funnel but the corkscrew was not as effective as using air pressure.
A corkscrew discharge would allow for controlled amount of flow vs. the air pressure discharge (10 turns equals 20cc's of pancake batter.  When you use the air pressure discharge you have the additional variable of batter viscosity and so any slight changes in batter recipe modifies the flow speed.
The advantage of the air pressure solution is that you don't need a mechanical means to extrude the batter, so even using a aquarium pump (thanks Bruce Shapiro from Egg-Bot) could be used to control the flow of the batter.

Thursday, March 17, 2011

I made this snow sculpture about a week before the earthquake and Tsunami in Japan but hadn't posted any pictures of it yet. (We wish the people of Japan the best as they face several catastrophes.)

 It's a sculpture of a Valkyrie VF-1S R.Focker Custom Snow Sculpture from the Robotech Macross Saga, a cartoon I watched as a kid.  Maia is standing in front of it for scale.  It's painted with non-toxic finger paint and I shot it in the morning as the sun came up over the horizon.  There are no build instructions for it but I ended up using a broom stick in the torso after the thing fell over twice while I was in the middle of making it.  There is a stick for the gun since it hangs over so much.  Hope you enjoy the photos.  Now it's back to getting Chris-bot and the animation project going again!

This is the non painted version.  I personally like the painted version because the colors really add to the shading of the thing.

Sometimes, it's not cool to mess with a robot.  Don't worry about Maia.  She was outside for 2 minutes and it was nice and warm in the sun.

She just didn't listen when I told her not to play with the robot.
This will probably be my last snow sculpture as the snow is starting to get crispy and not very usable.  I may give it one last shot this weekend, maybe a snow speeder in the woods, or possibly an Imperial tie fighter.
We'll see.

Thursday, March 10, 2011

How to Make a Star Wars Taun Taun out of Snow

I asked my cousin Don Solo what kind of sculpture I should do next and he suggested a Tauntaun which I think is rather appropriate since it gives something for the kiddies to ride on.  Not as technical as the AT-AT snow sculpture but it still was pretty fun to make.  I also made a timelapse video (Click here for link) of the making of this thing with some music by my friend in Orange County named Mark Dumas of Trailer Studios. 

Here's the build instructions for you.

  • About 30 shovels of sticky snow (Standard snow shovel about 24 inches wide by 18 inches deep)
  • 1 stick about 2 feet long to hold the neck in place (you only need the stick if kids are going to be sitting on it so they don't knock off the head when they try to hug the thing)
  • 1 Spray bottle full of Snow Glue (AKA water)
  • 1 Butter knife (now with 1 million and 2 uses)
  • 1 hand saw to cut away extra snow if necessary
  • A hammer to nail stick into upper torso
  • A leather harness or piece of rope
  • A small child (preferably your own or used with the permission of a parent)
  • A picture of a Tauntaun found at a Star Wars Wiki Site
Build Time:
About 2 hours (can be cut down if one person brings snow and the other person builds)


1.  Again, start off with sticky snow, preferably when outside temperatures are about 35 or 40 degrees Fahrenheit (4 C).  Try to use more powdery snow which can be found underneath the thin layer of crunchy snow.

2.  Begin by making a base of snow in the shape of a small R2 Unit by packing snow together tightly. The base should be about as tall as the child you intend to put on the thing.

3.  Once you have your base, hammer in stick so it sticks up at a 30 degree angle from vertical.  Make sure it's nice and solid.  If not, pull out, repack with snow and try again.

4.  Proceed with building the tail by creating a thin wall of snow to support the main tail and build on top of that.  This wall will be carved away after the snow freezes a bit. 

5.  Build up a bit of snow around the neck.

6.  Begin piling up snow on the sides of the base to make the legs.  Tauntaun legs are really big, like dinosaur legs so make sure you get some nice bulk there.

7.  Once you have your general leg shape in place, star working on the saddle by piling up a small wall around the top of the back of the base.
8.  At this point you can test the saddle size by placing the test child on the sculpture.

9.  After removing the test child, proceed with building up the torso of the Tauntaun and then work your way up to the head.  Make sure the head is turned to one side as this makes for a more interesting sculpture than just looking straight ahead.
10.  Proceed with building the arms and extending them outwards.  The claws curl in to tho the body.  Spray with Snow Glue once you're happy with the arms.

11.  Add horns and ears by placing bits of snow on the side of the head and building up a little at a time.  Once you're happy with the horns, spray with Snow Glue (water) so it will freeze up a bit.
12. Form the mouth completely closed at this time.  It's easier to carve out later.
13.  You should now have a general shape of the Tauntaun and you can begin carving in the details with your butter knife like the eyes, the nose, extending the feet and ears.  Don't forget the saddle strap that goes under the Tauntaun.
14. Once you're happy with the details, remove portions of the support from underneath the Tauntaun to make the belly as well as removing portions of the support from the tail.  Snow doesn't overhang very well for long distances unless it's frozen so you may have to leave a bit of support at the end of the tail or simply let it support itself on the ground.
15.  Spray the entire sculpture with Snow Glue (water) and let sit for about 15 minutes.
16.  Add harness or rope and smooth Tauntaun with bear hands to create smooth surface.  Please note in the picture it may look like the Tauntaun has a fin on its tail but it's not a fin, just a piece of snow in the background.

17.  Finally add child with goggles, light saber and/or laser blaster and fun captions.

'Captain Solo.  We've spotted the children and it seems their Tauntaun has frozen before it reached the first marker.'

Photo Tips
  • When shooting photos of you (yes, you'll also want to try it out) or the kids make the shot more interesting by shooting from low or high angles.
  • Picking up the details in the snow may be difficult if you're using direct flash but if you can bounce the flash in from an angle, you'll get better shadows which brings out the detail.
  • Use a photo editing program like Photoshop or Gimp (Open source) to increase the contrast and bring out more detail.
  • The light saber glow is done by using three layers in Photoshop.  First lay down a straight airbrushed line across the edge of the saber.  Second, overlay that with a thinner feathered white line and fade back to about 30%.  Last, add a layer underneath the saber layer and paint the surrounding areas with the color of the saber.  Fade back to about 7% and this gives you a nice vibrant glow in the surrounding area of the saber.
Thanks for visiting and if you repost this, please remember to show the proper credit!
Starwars and Tauntaun are registered trademarks of Lucasfilm Ltd.

Monday, February 28, 2011

How to make an AT-AT Imperial Walker Snow Sculpture for Kids.

 These are the instructions for making an AT-AT Imperial Walker Snow Sculpture.

First, wait for the snow to be a little bit mushy and you can make a snow ball by just grabbing it with one hand.
Next start off with something completely unrelated like the Pi symbol.

Then come to the realization that you can make legs of snow and actually bridge snow over short distances. The way to bridge the snow is to start off with small chunks and have the snow grow ever so slightly off the legs.  Then slowly start piling more and more snow on top of the thing and it should hold.  Now find a picture of an AT-AT Imperial Walker at a Star Wars Wiki Site. You'll need this to try to get as close to the details as possible.

Pile on the snow and make a small column to support the head and shape away with some hand tools such as a trowel, a small saw and a butter knife(now with one million and one uses).  Stick a kids broom into the body and form snow around it for the head.  Note:  I don't recommend you put the broom on as you're building the body, you want to jam it in to the torso so the snow compacts around it and holds it tight).
Use a column that looks like smoke to support the head.  (You may consider adding a crashed snow speeder there but the column is temporary).
Continue adding small patches of snow, little bits at a time to build up the different parts of the legs, head and body.  The legs need to be rather fat because you'll be carving a lot out of them.

The best way to do this is to scrape the snow from the top surface of the ground as that usually is nice and sticky.  Notice the  trowel in the background.
Pack it down with the concrete forming tool, then use a knife or a saw to cut straight lines into the cylinders on the legs and the body.  Carve the details with a sharp knife and then use your fingers to patch it up.
Run your bare hand over parts that you want to turn to ice as the top layer will melt and then freeze again forming a nice hard shell.
When I'm forming these things I use wool gloves as they get bits of ice on them and it creates a sand paper like effect.
 Add details and smooth out with fingers.  Let sit overnight before adding children.

Let it sit overnight and then breakaway the support on the head by carefully cutting away at it little by little as close to the head as possible.
 The legs are about 15 centimeters (6 inches) wide and have managed to hold about 50 pounds worth of children.

Add children and lightsabers (a little Gimp action on the glows) and you're having a blast!

A pair of x-country skis works too.  Helmet provided for safety.