Trebuchet Business Card - Trebucard

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The Trebucard is a business card sized mini trebuchet. It is designed to fire jumbo paper clips and uses 16 pennies as a counter-weight. Unlike a traditional trebuchet the Trebucard uses the surface it is resting on as a pivot rather than being mounted on a frame.

See a demonstration of the card here:

And here is a video that shows you how to make your own:

Step 1: Download the Design Files

Download the design files for the card in whatever format is easiest for you to work with.

If you have any problems with the Instructables attachments the files are also available here: http://www.thingiverse.com/thing:16735

Step 2: Required Tools and Materials

The materials you need are:
  • 16 pennies (or other similarly sized coins)
  • Some tape
  • At least one 'jumbo' sized paper clip
  • Some cardboard or thick paper
The easiest source for the card material is the cardboard from things like cereal boxes.

The tools you need are:
  • Scissors
  • A sharp knife
  • A printer or other method to transfer the design to the material.
You could probably make it with only one of those two cutting tools, but it is easiest if you have both.

Step 3: Transfer the Design

Now we need to transfer the design onto the cardboard. If you want to add your own text and graphics to make the card an actual business card then this would be a good step to do so.

The easiest way to transfer the design would be to just print it directly on the cardboard, but most printers cannot handle that thick of a material, so here are some potential alternatives.

You could print on a normal piece of paper and glue it to the cardboard.
You could cut it out from the normal paper and trace the design onto the cardboard.
Or you could use some kind of trace paper or pen with heavy bleed to trace the design onto the cardboard through the paper.

One thing that you want to check in all cases is that the design is not being scaled to a different size when you are printing it. The overall design should be 3.5" by 4"

Step 4: Cut Out the Design

Now we just need to cut along all the solid lines. The dotted lines are where folds need to be made, so you don't cut the dotted lines.

The outside shape can be quickly cut with scissors, but the inside lines are more easily done with a sharp hobby knife.

It may be helpful to make some slight notches along the 4 dotted lines that touch the outside of the card to make folding along that line easier.

Step 5: Fold the Card

The two sides of the card fold up at right angles and the two smaller tabs that were cut out with a hobby knife fold in towards the center and interlock.

This should form a sturdy shape that will rock on the table much like a rocking chair.

Step 6: Assemble the Counterweights

The counterweights are made by wrapping two stacks of 8 pennies with tape. I don't think it is very critical to use a certain kind of tape or wrapping technique, but I usually use Scotch tape and wrap them along the outside and just bunch up the excess tape along the edges.

The coin size isn't extremely crucial so small coins in other countries will also probably work. Just use however many coins it takes to make a stack that will fit firmly in the slots at the front of the card.

Step 7: Insert the Counterweights Into the Card

Then you simply insert your stack of coins into the slots you cut out of the card. They go in on the side opposite of the way the other parts are folded.

The coins should be a firm fit because they need to be held in place as the card moves around quickly.

Step 8: Prepare the Paperclip

The  two loops that you put on either side of a stack of paper when using a paper clip need to be bent apart slightly. Then you just set it on a surface with the largest loop propped up in the air.

I'm not sure if there is much variation from brand to brand, but the box of paper clips pictured above is the brand that I used when designing the trebuchet.

You could probably make your own sling if you wanted to shoot other small objects, and you can also attach objects to the paper clip to fire them.

Step 9: Fire the Trebucard

With the large loop of the paper clip propped up in the air you want to insert the small tab at the end of the card into the top loop of the paper clip. Be sure the loop is tight up against the tab on the card, then you simply allow it to rock forward and throw the paperclip. It should shoot somewhere around 8-10 feet.

A grippy rubber surface provides the best performance, but it can also be more temperamental to fire on such a surface.

You can adjust the loop on the paper clip (or the shape of the tab on the card ) and make it smaller or larger to alter the trajectory of the trebuchet.

A more detailed video of the operation of this card can be found here:

Step 10: Done? Fold It Up

Once you are done playing with the card you can simply fold it up to the size of a standard business card.

First you need to remove the counterweights by just pulling them out. Then you unlink the center arms and fold them back to the sides. Then the entire sides can fold in, and your paper clip ammo can be used to help hold it all closed.

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32 Discussions

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AyeAyeCaptain

2 years ago

Very nice! Performs much better than I expected. A bit of advice: Don't use index cards (I learned that the hard way), and thin cardboard (think cereal box) works quite well.

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Midcrane

3 years ago

amazing!!!!!!!!!!

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kevmcd

5 years ago

I adore this!

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prushik

6 years ago on Introduction

I was not real impressed.. Until he started consistently hitting that cup from so far away, that was crazy and awesome!! Once I saw that, I was thoroughly impressed, this is about as cool as the iris business card, this even has practical applications (if you define "practical" very loosely)

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clideprushik

Reply 6 years ago on Introduction

For the sake of full disclosure I was probably only hitting about 1/3 of the shots out there (or less), and I'm not really sure what all was throwing it off. I think it was largely the wind. In a more controlled environment with smooth concrete floors and no wind I was hitting 80-90%

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prushikclide

Reply 6 years ago on Introduction

Well, of course wind is going to throw it off, that has to be expected, however, its still incredibly accurate. I am quite impressed.
Most of the applications I can think of are indoors anyway (sinking paperclips in your boss's coffee).

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Dream Dragon

6 years ago on Introduction

Excellent Project (voted), and well documented too.

A couple of rules of fun, sorry THUMB!

In a conventional trebuchet, The Counterweight should be about 100 times the weight of the Projectile, the Arm should balance at the pivot when not loaded, and the pivot point is about 1/4 of the length from the counterweight end. Maximum efficiency is achieved if the weight is permitted to fall in a straight line.

Not sure how that might translate to your rocker design but I'd like to see some variations. Let's see if I can find some heavy Card...

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clideDream Dragon

Reply 6 years ago on Introduction

Thanks, I'd like to see some variations and optimization as well.

From my experimentation one of the important things about this rocking design is to have the CG of the counterweight as close as you can get it to the edge of the rocker so that it is as close as possible to the ground as the projectile is launched. I do have a variation which is more optimized in this regard.

Also a grippy surface without any slipping will help performance. Which seems to deviate a bit from that straight line principle in conventional trebuchets. But if you think about it, it makes sense because with the way the card rocks the counterweight's speed relative to the ground will be slowest as it reaches the lowest point. In the ideal scenario where the counterweight is at the very end of the trebuchet and in contact with the ground with no slippage at the time of launch then the speed of the counterweight relative to the ground would be zero which is exactly what you want. Although unless you have an infinitely dense material you will always have some speed relative to the ground and some angular momentum that won't be fully used.

But I do think you could get some pretty good efficiency out of this design with a dense counterweight and making the rest of the device as light as possible. One bad thing is that it doesn't scale well. Anything beyond what one or two people could lift would have to have a big frame to lift and support it for launching. But I've been thinking about trying to scale it up to golfball size projectiles and seeing how well it works on a medium scale.

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clideKiteman

Reply 6 years ago on Introduction

Thanks Kiteman. I actually did a rough calculation of the mechanical efficiency and came up with 45% which isn't bad considering there are many things that could be done to optimize it's performance (at the cost of being harder to make/use and less durability).

For comparison the Cardapult V2 launches the same size paper clip about the same distance, but requires about 3x the energy input.

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clideKetzer

Reply 6 years ago on Introduction

That's one thing that could be looked at, as well as the overall length of the card. If I was going for maximum efficiency the main things I would go for would be moving the counterweight as close to the outside edge as possible (which may also include using a denser counterweight). And minimizing the weight and air resistance of the rest of the device especially as you get more towards the projectile end because it will be moving the fastest on that end. Also a proper sling might help, but it's hard to do on this scale.

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gverble

6 years ago on Introduction

I am not an old fuddy duddy, but I don't understand the purpose of this item, nor have I ever heard of such a thing, but it was a well presented instructable, so I voted for you. ☺

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clidegverble

Reply 6 years ago on Introduction

A trebuchet is an old siege engine that was used to hurl large rocks into castle walls. These days it serves no purpose other than being a fun way to make stuff fly through the air.

It can also be useful for demonstrating principles of physics like conservation of energy. The energy from dropping the relatively heavy weight of the pennies a few inches is used to launch the lighter projectile several feet.

This is just a scaled down and highly simplified version.

Thanks for the vote.