LEGO Crazy Swing Arm Action Mechanism

This is what we're going to build today.

Pieces we're going to use today:

Let's build!

Catapult Hack-a-thon!

This is a project I picked up from RAFT in San Jose. This would have been a good project on its own, but I wanted to challenge my 6th graders. So, for the first ten minutes, I have the students quickly put this kit together. Then we spent the rest of the class period hacking it for distance and accuracy.

This is what the students built in the beginning.

Supplies List:

• 1 binder side or a cardboard the size of a binder 
• 7 unsharpened pencils
• 2 binder clips
• 1 soft pompom ball
• 1 plastic spoon
• 1 rubber band
• 1 pencil top eraser
• 5 rubber tubes with a hole in the middle
• 1 rubber tube

Build Instructions:

As I said, I built the catapult then left as an example for the students to see and build. I also leave out the instruction pamphlet for them.

Once they build the catapult, they come up to the line and shoot it to see how it flies. Then the students are instructed to "hack" the catapult. The students are encouraged to do anything they want to it, except they can't cut the rubber tubes and break the pencils.

And these are what the students came up with (I didn't add all 4 classes of modifications).

The best of the best! (see below)

This design was so awesome that this design gave me goosebumps!

1st hack attempt. This didn't shoot as far as the team had hoped.

The final hack!

Closed. At rest position.

Fully armed.

Ready for a shot.

Fun group photos:

LEGO rack and pinion gears 2 - Mechanisms

Some of my favorite gears to play with in LEGO is rack and pinion gears. I guess I like watching the gears move from side to side.

This is what we're building today.

The pieces I'm going to use today:

I didn't have the pieces the book used, so I tried to use replacement pieces.

Pictured above are red and yellow flat pieces for the rack and pinion gears, 

but they didn't work out at the end. So, later on, 

you'll see orange pieces to make this mechanism work. 

Pictured here is size 5 gray stick piece. What you need is size 3 gray stick piece.

I thought I might have fun with a mini figure since my daughter enjoys collecting them so much.

These are the replacement pieces for the red and yellow piece pictured in the first photo.

The red and yellow pieces are pictured in the background.

The Tech Challenge is Coming.

This is a program I DEARLY LOVE. 

I've been an adviser since 2013. But after five years of being an adviser, sometimes two teams, I'm taking a break this year. 

I had hope to participate as a volunteer, but a sudden change of events prevented me from doing so. Still, I hope to attend the Showcase next week.

As I noted on my Cal Day 2018 blog, I haven't been able to attend Cal Day, because I was fielding teams in the Tech Challenge. So, if driving to UC Berkeley is too far for you (or taking BART), then you have something else to consider this weekend. Attending the last weekend of test trials at the Tech Challenge!

I know. It's going to be crazy. 

People are going to be EVERYWHERE. But you can't get any closer to the action than this. Especially, if you have small children who are interested in Science/Engineering and would like to see things go and do interesting things, this is the place for you. 

And it's FREE.

Have a great time!

My previous Tech Challenge 2018 post with more pictures.

Tech Challenge 2018 Post 1

PS - You might be able to get into the Museum at a discount, too.

Alka Seltzer Blast-off 2

This project effectively demonstrates the Newton's Laws of Motion.

First Newton's Law of Motion states that an object either remains at rest or continues to move at a constant velocity unless a force acts on it.

• The rocket is at rest, but when it's acted upon by the chemical reactions of water and the Alka-Seltzer tablets, it has a powerful lift-off. The force of the reaction blows off the film canister lid.

Second Newton's Law of Motion states that Force is equal to mass multiplied by acceleration.

• Force = mass x acceleration
• The force of that lift-off is equal to the mass of the film canister, the water, and the tablet inside multiplied by the acceleration provided by the chemical reaction.

Third Newton's Law of Motion states for every action, there is an equal and opposite re-action.

• As the film canister lifts off, the canister lid, water, gas, and slide experience the downward force of the push. The lid pops off. The water and the gas spread out, but because the slide is secured on the ground, we can't see it move.

The Chemistry behind the project:

1. Alka-Seltzer tablets contain sodium bicarbonate and citric acid.
2. When the Alka-Seltzer tablet piece comes in contact with the water inside the film canister, it begins to dissolve. 
3. This results in sodium citrate, water, and carbon dioxide gas.
4. The carbon dioxide gas builds the pressure inside the film canister.
5. Eventually, the pressure inside will pop the film canister lid off.

H₃C₆H₅O₇ + NaHCO₃  ==========>  NaC₆H₅O₇ + H₂O + CO₂ + Heat

Citric Acid + Sodium Bicarbonate ========> Sodium Citrate + Water + Carbon Dioxide + Heat

Because Heat is released during the process, this chemical reaction is called an 

exothermic reaction.

Second Newton's Laws of Motion states F = ma. So, different amount of water or Alka-Seltzer piece will affect the take-off time and altitude of our rocket.

Also, take-off time is affected by the surface area of Alka-Seltzer exposed to water. Crushing it will reduce the take-off time significantly.