Monday, December 18, 2006

Fifth Meeting: Dry Ice, Smashing a Monitor, Rocket Car and Feedback

Hiya y'all. Thanks for coming on Friday, if you did. It was fun. :) (Last meeting of 2006, too!) Vivek's going to try to get those videos online sometime in the near future.

We started off with some dry ice bombs. Our first one appeared to be a dud, which was a bit scary because you just know that the moment you give up and go to pick it up it'll blow up in your face. Fortunately, that didn't happen. :)

We had several more successful dry ice bombs after that. We also tried burning flour and making bottles of hairspray into flamethrowers and so on. But the real fun was just beginning. (If you've come a lot you'll notice that our meetings tend to start off slow and really pick up towards the end.)

Michael Firer had donated an old broken PC monitor for us to, uh, break even more. At first we tried using the potato gun, but we only got one glancing shot in and then the potato gun decided to, well, stop working. So naturally, we took the biggest, heaviest metal pole we could find, and just smashed it. A lot. Over and over and over again. We tried putting some dry ice bombs inside, but that didn't work so well.

Finally, we decided to re-try a rocket car, since the rocket dune-buggy went a total of, um, 5 feet? Brenden Hickey had recently participated in a 9th Grade Physics Class mousetrap car competition. Obviously, a rocket engine provides a bit more thrust than the spring of a mousetrap. So we strapped on four. You'll have to wait for the video to see just what happened, but suffice it to say it was spectacular. :)

Now for a few thanks:

- Mr. McKinney, for getting the dry ice for us
- Vivek for filming everything
- Michael Firer for donating his old PC monitor, poor thing
- Everyone who cleaned up the remains of said monitor
- Ms. Nickerson, Peter, and Vivek for doing extra cleanup
- Brendan Hickey for donating his car & David Arbeiter for spiffing it up with a few nice rocket engines
- And whoever took attendance at the LAST meeting, not this one (I know, the thanks are kind of late)

And now for some feedback. So far this year in the club we've done all sorts of things, but we haven't really put a lot of time into any single project. What does everyone think about that? We don't want to go too slowly, because then it gets boring. But we don't want to go too fast, because then we can never do any big projects. I feel like we might be rushing through things a bit too much at the moment.

So: is there any project people want to spend some more time on? If you don't want to answer this little mini-survey you don't have to, but we'd love to get people's input. We're open to ANYTHING. So: what do you want to do? Rank the following from first (you really want to do it) to last (you couldn't care less):

- Hovercraft (big project)
- Egg Launch Contest (big project - try to launch eggs in rockets and return them to the ground unharmed)
- Model Car Contest (compete for fastest, farthest distance, etc.)
- Glider/Model Plane/Flying Things Contest (longest flight time, fastest, highest, etc.)
- Building Circuits
- Rube Goldberg Machines Contest (you know--the ball rolls down the ramp and starts the dominos, the dominos trip a wire that releases a bowling ball, the bowling ball knocks over a vase that yanks a weight off a table, the weight falls on a button that launches a rocket - that sort of thing)
- More Coke & Mentos
- More Dry Ice
- More shooting the potato gun at stuff
- More rockets

Any other comments? Anything else you'd like to add to the list?

Friday, December 01, 2006

Fourth Meeting: Potato Gun and Target

Today we shot a target with the potato gun. A lot. At least, we tried a lot. :)

But first we tried launching little match rockets... and we kinda failed. That was pretty, uh, experimental... as in, I had never done it before and barely even knew how to do it. Well, it engaged a lot of people for much of the club block, so apparently there was something interesting about it. Or maybe it was just the matches.

(UPDATE: Willy tells me they gave up on the match rockets and just made a giant match instead. So it was just the matches. Guys, you should have soaked the paper towl in hairspray. It would've been a lot easier to catch on fire.)

Once Vivek returned with a camera we set up the target, leaving a few people behind still playing with the matches. Craig, marksman extraordinaire (he alone hit the improvised target of 'a bag' in our first meeting) took the first shot... and it was a good one. The wood immediately cracked, and the bracing boards on the back popped right off. (One of those boards would soon become the match group's giant match.)

Our next few shots weren't so successful. For the first time, we had two potato guns operating simultaneously. We never got to shoot them at the same time - Ms. Nickerson wouldn't let us (no clue why) - but it made things go much more quickly. We soon branched out from our normal potato ammunition and threw some yogurt and pudding into the mix. Our first few shots missed, but we got some good ones in there. Craig also made a triumphant return, this time punching a hole straight through the target.

Emily closed off with a very nice bulls-eye, splattering pudding all over. That was the last of our hits - we only had three - and the only one to really splatter stuff on the board. On most shots, we pretty much just splattered the makeshift "road" to the construction site.

We closed off by talking a bit about our plans for the future. We all agree that the next meeting should be dedicated to just blowing stuff up, plain and simple. But what comes after that? Building radios? Steam-powered boats? Rocket planes? Speak up! We need your feedback!

Safety First! A Few Guidelines

A year ago, at our third club meeting ever, I was bracing the potato gun against my side when we fired it. Today at our fourth club meeting of the year, Jason was doing pretty much the same thing. Every other potato gun launch we've ever done has been perfectly fine. But these two times, we got a pair of holes in our shirt. Why? And how can you prevent it? (HINT: it's very easy and totally reliable.)

Potato Gun Safety

  1. Never walk in front of the potato gun while it's primed and loaded. Actually, I'd avoid walking in front of it any time it's being used. If you do have to walk in front, be sure the person holding it AND the person holding the ignition switch know you're there.
  2. If you're holding the igniter, NEVER go until the chamber lid is firmly on. Wait until after the person who screwed it on takes his or her hand away. Willy got burned once because someone jumped the gun and clicked too soon.
  3. And here's the one Jason and I have to pay attention to. Notice where the two wires from the igniter go through the PVC and into the chamber. See the two little holes? Jason and I got burned because we had them facing towards us. Normally its not a problem, because most of our potato guns have those holes epoxied. (Epoxy is that super-strong glue stuff.) If the holes are epoxied, you're perfectly safe. Don't worry at all. We've done this dozens of times, if not hundreds. If you can't tell whether or not there's any epoxy (think glue) around the holes, tell one of the club presidents or a teacher. But as long as you keep the holes facing away from you, you'll be completely fine. It's a very very small flame coming out of there, and it only goes for an instant.

Rockets

  1. Don't be near the rocket when it fires. If you're launching it, stand as far back as the wire length will allow. If you're not launching it, stand even farther back.
  2. Don't stand behind the rocket, or downwind of it. You'll get a mouthful of yucky yucky smoke. It's not really dangerous, but it's yucky.
  3. Never try igniting the engine with anything other than the electronic igniter.

Other than that, don't do anything dumb. When in doubt, ask a teacher. Or me. Or Peter. Or Vivek.

Using the Potato Gun and Launching Rockets: A Few Tips

When you have thirty kids running around begging for pudding, sometimes it can be hard to give them all good instructions. These are a few tips that will help us get the most out of our meetings.
The Potato Gun
Nobody Likes a Misfire
Today at our fourth club meeting we did a ton of potato gun firing. We did have quite a few misfires, though - that is, times when the potato gun just didn't fire. There were also a few misses, although our aim was fairly good. In any case, here are a few tips for being a potato gun expert.

AIMING: If you want...
  • Maximum Distance: Hold the potato gun at a 45-degree angle.
  • Maximum Height: Hold the potato gun straight up, of course! :)
  • To Hit Something: If you're relatively close - say, half the width of the Lower Field - you should pretty much aim straight at the target. Aim a little bit up, but probably not more than 10 or (at most, if you're, say, all the way accross the Lower Field) 15 degrees. This one will just take practice.
POWER: How do I get the most?

  • We haven't yet done a lot of testing, but there's a perfect amount of hair spray to spray. We've found that 4 seconds works quite well.
  • Also, choose a nice big potato - bigger than the barrel. Use the sharpened edge of the barrel to cut it down to size. Try to avoid ANY air gaps on any side of the potato.

MISFIRES: Why do they happen, and how do you prevent it?

  • The potato gun will not fire if you have too little or too much hair spray in the chamber.
  • NOTE: More hair spray does NOT always mean it'll go farther! There's an optimal ration of air to fuel. If there's too much fuel and not enough air in the chamber, it won't ignite.
  • SO: don't spray too much! (That's a lot more common than spraying too little.) It it won't fire, wait! Air out the chamber.
  • Note that sometimes, misfires are out of your control. Sometimes a wire is loose or unplugged or broken or something like that. But 98% of misfires are thanks to having a bad air-to-fuel ratio.
DUDS: Why did the potato just softly plop out of the barrel?

  • Again, there is an optimal ratio of air to fuel. If you have just a little too much or too little hair spray, the potato may not go very far.
  • Also, the potato needs a good seal in the barrel. That is, it should fit very snugly, and give a good deal of resistance when you shove it down the barrel. Otherwise, all those explosive gasses can just escape out the gaps around the potato instead of launching the potato.
  • SO: spray for about four seconds. (It's probably worth experimenting a bit with the exact timing.) Don't have too long a countdown - three seconds will do it.

Rockets
Push the button HARD

Rockets are, in some ways, a lot simpler to launch than is a potato gun to shoot. You don't need to optimize this or that. But it is a longer process. Here are the steps:

PREPARE THE ROCKET (note: I won't be too detailed about actually making the rocket.)

  • When your rocket body is all assembled, crumple up three or four pieces of fireproof wadding and stuff them down the body tube.
  • Attach the parachute, fold it up and put it into the body tube.
  • Take the bottom of the rocket off and put in the engine. Put the bottom back on.
  • Stick the black end of an igniter (the little metal wires split like a weird V) into the hole in the bottom of the engine. Secure it with one of those little plastic plugs - the things that look like thumb tacks. Bend the wires out to either side.

ON THE LAUNCH PAD

  • If there's no wind, keep the launch rod aiming straight up. If there's wind, tilt it slightly into the wind.
  • Slide the rocket down the launch rod. Try to suspend it off the metal disc an inch or two, e.g. by wrapping the rod in tape at that point. (The tape part isn't necessary, but helps.)
  • To test it, take the the black box (electronic control box thingy) and clip the ends of the wires together. Put the key in the hole and press down hard. If the light lights up, you're good to go. Otherwise, you need new batteries.
  • Clip the wires from the control box to the two wires of the igniter on the bottom of the rocket. Keep the clips from touching any other metal.
  • Walk as far away as you can with the control box. If the launch pad is tilted in any direction, stand behind it. The wires will come unclipped very easily, so you may want to have someone hold on to the wires by the launch pad so that when you pull it taut, it'll tug on them and not the fragile connection to the rocket.

ACTUALLY LAUNCHING IT

  • Start a countdown
  • Around 3, put the key in the hole and press down hard.
  • Right on one, or even an instant sooner, press down hard on the black square button and hold it. Hold it! It'll take a second for the engine to light.

And that's it! :) Now you're all potato gun/rocket launch experts.

A Guide to the Blog

Welcome to the official Beaver Science and Engineering Club blog! Here you'll find news, videos, pictures, and more. To help you get around, here are a few links to the most important posts and items:

Year One
First Meeting: Planning our first meeting ever, spent doing some simple planning
Second Meeting: Rube Goldberg Machines 9th grade won, 10th grade lost. :(
Third Meeting: Potato Gun I get the burn on my sweatshirt

And then there was a long stretch where we didn't do very much, but worked on rockets with egg payloads for a long time.

?th Meeting: Egg Launch Finale finally! after THREE MONTHS!
?+1th Meeting: Burning Flour the beginning of a new era
?+2th Meeting: More Flour... Waaaaay More we got some BIG flames

We did a bit more before the end of the year, but nothing significant.

Year Two
First Meeting: Potato Gun the year we don't make the mistake of starting out without a bang
Second Meeting: Silly Putty and Basic Rocket Launch fewer bangs, more chemistry
Third Meeting: Van de Graaff Generator and Rocket Dune Buggy less chemistry, more electricity
Fourth Meeting: Potato Gun + Target this time we have something to shoot AT, plus some more ammunition variety
Fifth Meeting dry ice, smashing a monitor, rocket car
Sixth Meeting rocket javelin [with video]
Seventh Meeting dry ice and two rockets, including one that kind of nearly killed us (or at least, nearly hit us) [with video]
Eighth Meeting we fail at making a hydrogen fuel-cell car
Ninth Meeting our rocket does eight flips [with video]
Tenth-Twelfth Meetings Recap the egg launch project puts us in a bit of a lull for the second year in a row

Miscellany
Become a Potato Gun/Rocket Launching Expert a few tips and tricks
Safety Guidelines we try not to be quite as reckless as we look

I will expand this guide as the blog expands.