Help on creating a rube goldberg machine?

Work backwards from the result you want, and keep asking (and answering) the question “What can trigger this?”

You have the final goal of “catapulting an object”, so now you just have to figure “what can trigger the catapult?” Brainstorm that for awhile until you get a list of triggers that seem possible / practical for you (and keep that list, because you may need it again), and then figure, again, what can trigger this trigger?

You might end up with a dead end at some point, and need to go back to an alternate idea, which is why I suggest that you retain all of your brainstorm ideas.

If you were going to be really fancy, then you should have separate mechanisms to:
1. Load the catapult basket
2. Prime the catapult (put the tension on it to make it ready to deliver)
3. Trigger the catapult

But that’s just my own one-minute brainstorm. Have fun with this. My physics classes were never so much fun.

I agree with @CyanoticWasp on reverse engineering back from the final result. Think of things like transferring fluids, falling water, dropping objects, as silly as possible. Do they allow external power sources? A battery-powered fan to turn a windmill? Lightbulb activating a PV cell?

Check out the game Mousetrap if it is still available in stores. The whole game is a rube goldberg machine with a catapult as part of it. It may well give you some good ideas. Here’s a review that shows the contraption.

Here’s some inspiration.

Tiny waterfalls filling a cup till it’s weight reaches a tipping point make a great delay device. Another interesting delay is a repetitive action that advances an escapement one click each time it repeats. Have fun with it.

Cheap windup alarm clocks or kitchen timers are good trigger devices and can do work, too. Obviously, they can be timing devices, too.

Candles are popular (but you can’t cheat and light the thing yourself; you need a trigger to strike a match or other flame to start the fire). The candle can be used for timing (a candle in a horizontal alignment will have its flame move along the length of the wick, and can burn through a string to trigger something happening, and (see below)

With the candle, you can do things with hoods to capture the hot gases and then rise as another trigger mechanism; depending on the sizes of the candle and hood (and its mass), this is another timing mechanism if you can judge how long it takes the hood to rise, for example.

All kinds of gravity devices are available, from falling dominoes (very popular) to balls rolling along inclined planes (a trough, so you can control its direction) to water devices, as others have mentioned.

The point of the exercise is two-fold: for you to recognize various types of mechanisms and triggers yourself, and then to be somewhat ingenious in making a series of them cheaply… and to be aware of the physics that make them work.

Don’t forget friction!

okay so for our delay, we’ve used cell phones. hopefully our project works, we’re presenting tomorrow!

@NuGoonie23 I hope you can post a video of it to YouTube and post a link here. I’d love to see it.

will do. =)

okay. so I’m TOTALLY SORRY. I forgot to check out a camera to record it. but I’ll post up a scan of the sketch for our project.

Drat. I was looking forward to the video, but a sketch will be fun too.. Did it work as you wanted it too?

Haha wow, okay so we totally thought ours wouldn’t work. Ours turned out to be the best one! When I went to lunch tutoring before my class (physics class) one student from the class before told me that they heard that my lab partner was driving to school and on the way to school our project broke. So I was freaking out by the time I got to physics, but thank god she brought her glue gun and put everything back the way it was. Ours did work, and we had to help it only once. So we got 5 points deducted for that. We ended up getting a 95 though so we really couldn’t complain. The other lab groups didn’t do the task they said they would and ours did.

=)

here’s the url to our sketch:
http://i135.photobucket.com/albums/q140/tokenturk23/scan0003.jpg
you have to turn your head to the right and look at it horizontally. It starts on the far left with the diagonal ramps and ends with the catapult.

@NuGoonie23 Congratulations. It looks like it would have been a barrel of laughs watching it. Thanks for sharing.

Thanks @ETpro!!! And no probs!