Split Reaction &#187; Nonsense

The Mega Claw – Prizes (7 of 9)

dye — Sat, 25 Sep 2010 15:09:14 +0000

So what kind of prizes does a massive claw machine have? Well we all chipped in and bought over $700 in prizes for Maker Faire. All the earnings will be used to power Splitreaction’s web fees, projects and cost of the machine. We certainly like the prizes. We hope you guys will too! Also since we hate unfair claw machines, the MEGA CLAW will be a PRIZE EVERY TIME!

In fact to sweeten the deal we will raffle a Nintendo Wii as a grand prize, mailed to the winner’s house. It will start as one Wii for the event, but if we recoup our machine cost we will add more prizes. Since it’s win every time we don’t want the first player to grab the Wii and run away. Also we don’t want to bury the winning prize at the bottom because that’s just being mean. The best way to give everyone who’s supporting us a fair chance to win is by making the Wii a raffle. In the machine raffle tickets will be attached to special balloons. Some balloons may have many tickets, some may only have one. We will also sell the raffles on the side for anyone who is not interested in playing the machine, but wishes to help us fund our next project.

This is a really cool tool pen we got customized with our site. Limited Quantity, only 36.

It spins, it bounces, it flies!

We felt jipped in the Mp3 experiment #6 so we decided to order hundreds of bats and hammers for the machine.

Here are Dave & Andrey showcasing how to use the bats and hammers

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The Mega Claw – Electronics & Software (6 of 9)

dye — Sat, 25 Sep 2010 15:08:45 +0000

HARDWARE

This is the block diagram, some of the things may have changed since we first worked with it. The Mega Claw is an Arduino Pro Mini with some Sabertooth Motor Controllers and a PC communicating over serial.

This is the pin out we used. We wired most of the signals with cat 5 cable so it made life a bit easier.

Here is the development board.

Behind the breadboard we routed out a hole. This way we can solder to it and keep everything secure on the backside.

Wiring was a nightmare, the cable harnesses took days to wire. We wound up using molex connectors for most of the joints.

To suspend the wires we used those spring loaded id badge holders.

Some random motor testing. All was going well until 48 hours before Makerfaire one of the speed controller channels stopped working. It was horrible and we were in panic mode since there was no way we could afford over night shipping for a new one and they were about $67 each. The only thing we could do was scrounge around and ask everyone we knew for a loaner.

Fortunately Chris still had some friends at PolyBots and they happened to have a real beefy one to loan us.

Here’s the machine being driven by our development board.

SOFTWARE

The software is a bit of a secret sauce cause we don’t have it 100% functioning. We’ll probably release that after Makerfaire since we’re still tweaking it constantly. We actually have two pieces of code. One is the arduino script running on the microcontroller, the second is a script running on the PC as a sound board. This way when the machine starts the arduino can use the PC to play sound effects.

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The Mega Claw – The Frame, Sliders and Prize Bin (5 of 9)

dye — Sat, 25 Sep 2010 15:07:57 +0000

THE FRAME

For the frame of the Mega Claw we figured we would start with a regular canopy. It was affordable and much more portable than the original one we started working with. In this segment We’ll talk more about how the main structure was put together and why it was designed that way.

We popped off the top and planned to add some pvc pipes and joints to form a large bin.

The bin would then be covered with a tarp for the balloons and to hide the tarp we would buy some inexpensive black cloth.

Here I am next to the frame at the lowest height. The off the shelf canopy was great because we could lower it when we needed to wire the electronics or fix things up.

We could attach the machine to the canopy using ropes and hooks. This made the machine less stiff and alignment wasn’t as important.

This is the original rigid design. It probably wouldn’t have been as convenient.

THE SLIDERS

Just like the claw we started out with many 3D models before we started building the sliders.

These are the three sliders used on the machine. They are upside down in this photo. The one with the rope has a built in winch as well.

More painting.

The sliders work like a clothes line. The motor below turns the black plastic pulley. That pulls the second pulley which pulls the rope.

Test video before we added a u joint. You can see the other side fall off the rail.

The pulleys are made of 3 stacks of 1/3″ wood.

They worked really well.

Here is a snapshot of the unpowered side and the axle we finally added to make it move.

Here is a better picture showing how both sides are now connected with an axle.

We were worried that the axle would buckle since the rails were suspended. We made two sets of universal joints out of pvc. This way even when the machine bends the axle will compensate.

u joint attached to pulley

THE PRIZE BIN

The prize bin was made of PVC pipes. The hardest part was remembering where everything belonged.

To secure the tarp and cloth we used grommets. These make the little brass rings on the tarps

Now all we needed to do was drill some holes into the pvc and we could use regular 1/4-20 bolts to secure it.

Makes a good bunker too.

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The Mega Claw – Joystick (4 of 9)

dye — Sat, 25 Sep 2010 15:07:12 +0000

The joystick was a definite must. We had talked about it and stumbled across Mary Flanagan’s giant joystick and it was final, we needed something epic. Just like her’s, ours is modeled after the Atari days of joysticks. It’s human sized and enough to be a project itself. We’re hoping that we’ll be able to use this to play games as well.

We started with a wooden model and it was too heavy. It had a lot of inertia and stressed out our joints (on the joystick and our back.)

We finally took another approach and made the joystick out of stacks of foam surrounding a pvc pipe. It would be modular, lighter and easier to transport.

To make it all swivel we used a universal joint.

Clearly we love skate bearings, but skate bearings were a little too short to fit into the 1/2in wood we used. So we designed a spacer.

Front View

Back View

The button is a sparkfun arcade switch with a bent coat hanger as a spring. You can see the pink foam on the inside. Instead of painting the joystick we actually use contact paper to cover it.

We sanded the PVC down on an endcap and we got an instant button.
6 coats of paint in case you were wondering. We kept dropping the cap and denting it.

This is the U joint with the limit switches mounted on it. The switches are triggered before the joystick hits the edge. The whole assembly is held in the center using bungee cords.

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The Mega Claw – Claaaaw (3 of 9)

dye — Sat, 25 Sep 2010 15:06:11 +0000

So I designed the real claw in Google Sketchup, a 3d design tool. I decided to make it out of 1/4in plywood and to add a skate bearing at every joint to reduce any friction or strain on the motor. In hindsight this cost a lot more and probably wasn’t necessary.

By the time I could turn my PC CAD on I already had this built in Lego Bricks. I gotta say I love those little abs bricks.

We printed out all the patterns and cut them all out using a band saw.

With the right motivation and sanding it all fit like a dream.

More assembly

Done!

I found a site called www.gifninja.com and got a little obsessed with making animated gifs.

Oh well it was time to disassemble the claw and peel off all the paper to paint it. Look at all those skate bearings. By the way those aren’t bolts, those are all rods we cut and sanded to the right length.

3 Coats later

I cheated and used a drill to power the claw in that video, but explaining how it works is a lot easier after you’ve seen the video.

The claw has a little winch inside. There are three Kevlar ropes inside that lift the three claw teeth and make the claw close. The two chords on the outside are used to make the claw open. The outside and inside are wound in opposite directions so one pulls and the other releases. A pulley connects to the motor.

This is a shot of the three chords that pull the claw closed. Using three helps the claw’s finger close at the same time. Some springs were added so the pieces wouldn’t slam so hard together.

Threaded rod was machined flat on a grind wheel and drilled so the ropes would not chafe

Pulleys made from plywood

We always wanted to use a pneumatic piston, but the cost of the air cylinder, 20 feet of tubing and everything else made it too expensive. Maybe next year.

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