Introduction: Mini Earthquake Simulator
After re-reading the guidelines for the Build My Lab and the Workshop Contest, I'm not sure how this project fits into those criteria... but here it is anyways.
This project is the result a fourth-grade science project, a broken food processor, and a couple nights worth of work. My younger sister was in a group of students, and as their project, they chose to examine the strength of bridges in earthquakes.
Originally, my sister asked me to do this. Now, of course, when my mom started talking about duct-taping a motor to a desk to shake the desk back and forth, I had to get involved before something bad happened. And I wanted to totally make this one of the best, cleanest-designed things I've ever made.
So without further ado, I present the Miniature Earthquake Simulator.
- Insulated Gloves
- Safety Glasses
- Common Sense
If you undertake this project, you will be working with 120V AC mains power. I assume you know not to do stuff like connect the two ends of the wires when they are plugged into the wall socket - with your body or just by themselves.
The motor also goes really fast and spins stuff around even faster. That's what makes the thing work. It can also destroy your hand, or the wires, or the container, etc. etc.
ALWAYS wear GOGGLES and GLOVES when working with the electrics. Make sure stuff isn't plugged in when you're wiring stuff up. PLEASE be careful! I am not responsible for any and all injuries, damages, or accidents caused by this project.
- Plywood Sheet
- Heavy-Duty Plastic Tub
- Bike Tubes
- Screws (Various Sizes)
- Insulated Wire Nuts
- Food Processor (or other electric motor)
- Insulated Plastic Electrical Staple (Optional)
- Mains power cord
- Nuts + Bolts (Alternative)
- Counterweight (I used a block of wood with a screw into a PVC pipe.)
- Switches (mainly covered by the food processor - however, the safety switch is an important piece to consider making pretty.)
- Drill Bits (Various Sizes)
- Vise Grips or Pliers
- Saw (I used a plastic pipe saw)
- Jigsaw (or other power saw - suggested)
- Square and Measuring Tape
- Workbench (Vise suggested)
I'm sure I've forgotten something. With reusing projects like this one, the more tools and materials at your disposal, the better. You'll know what tools you need to use as you go, or how to improvise with another tool. But at all times, please be careful, and have fun!
Update: The earthquake simulator will be used in a few weeks to test structures at our middle school! Good luck, Earth Science classes!
Step 1: Processing the Processor
Make sure the processor is UNPLUGGED. You don't need the blade, or the top, or the bowl thing. Just the motor and gears and wires.
I started with the food processor. Unfortunately, I don't have many pictures of these first steps. While taking the screws out of the bottom of the machine, I found that one was not a standard screw. I remedied this by ripping the plastic molding off the bottom.
Then, when I found that there was still some plastic molding connected to the processor, I took Vise Grips and ripped it off too.
Sometimes force is a good thing.
After removing the bottom paneling, I was able to remove the motor mount and get to the wiring. Make sure that you save the shaft that spins the blade, and the gear connected to it. This is what I will be attaching the weight to, so that the platform will vibrate. This is better than attaching the weight directly to the motor, because it saves the motor by channeling the off-center force into the first gear. It also makes the shaft spin with more torque, which will keep the motor spinning even with a big weight at the end of it.
Next, I found the connections between all the wires. They were some factory-installed wire nuts that I un-crimped (see picture two above) with some pliers. Take note of the connections, and which wires go where. Then the motor and power cord can be removed.
On my model, there were screws that had to be removed before the switches could be taken out. There are really two switches in the casing: the one that controls the speed and pulse, and the safety switch that keeps the motor from turning on if the bowl and top is not attached.
Step 2: Creating the Quake: Surface
I actually made this last. It would have made a lot more sense to do it first. But hey! That's why I do this stuff. To learn.
This is where we need bike tubes, and the thick plywood sheet. I cut the plywood sheet so that I had an inch inside the top edge of the box. Doing this gives the platform room for movement, and lets the rubber of the bike tubes actually have tension to counteract the weight of the motor. Without this space, the entire thing would shake all over the place. With the rubber and the space, the bin moves much less.
To hang the platform from the sides of the bin, I first arranged the bike tube strips so that they would be parallel and cross at four points (see pictures). At each intersection, I poked a hole with scissors, and then threaded small wood screws through, with a washer.
Then attach the motor to the board. To begin with, position the motor mount off center, with the motor to one side. My reasoning was that the weight would counteract the rotational force of the weight, and provide just enough shake. 'Course, that was just an idea and an impulse... Maybe if the motor was centered, then the board would shake more, because the motor would act as the center of a wheel, as opposed to the other end of a fulcrum.
After positioning the motor in the right place, press down on it. Then pick it up. Find the imprints of the bolts for the gears on the wood, and use a big drill bit to hollow them out. I especially had to do this because the screws were only just long enough to reach into the top board after I drilled out those holes. Then, replace the mount, placing the bolts in the newly drilled holes. But don't drill all the way through! Keep the top clean! Also beware the gears rubbing on the board.
Once the mount is in the right place, I prepared to put screws into the vibration mounts. However, the first time I started it up, the rubber dampeners were left on the screws while the mount ended up in the bottom of the tub. To fix that, I put the washer and dampener on the screws, and then screwed the screws into a small piece of plywood. Then I cut them apart with a hand saw. By inserting the rubber dampeners into the motor mount and tightening the wooden blocks against the mount, the dampeners are kept tight against the mount, and prevent the mount from shaking itself loose. Also make sure the pilot holes and screws aren't going through the top, or else there will be some filing to do... and I speak from experience...
The counterweight is seen in the top picture. It is very simply made: a block of wood run through with a screw, which is driven into a piece of PVC. The PVC pipe is then jammed onto the end of the shaft that used to hold the blade. Simple and effective. :-) I would suggest drilling pilot holes through the block of wood and one side of the PVC pipe so that it is easy to get the screw through.
Step 3: Creating the Quake: Switch Box
I wanted to use the original switches, because that was the easiest thing to do. However, I ran into a problem with the safety switch. It was too short. So I hijacked another switch with a big red button (which was hijacked from a defunct dehumidifier) and mounted it on the processor's switch. Luckily, they were the same style switch, and the big red button would make it obvious that it was important. I found a drill bit that would accommodate the button assembly, and drilled a hole for it. Make sure that the switch will fit where you put it; mine almost didn't. Then I tightened the nut that came with the button assembly thing. Lastly, I inserted the actual button thing. At the contact point with the switch, the red button flares outward in a fork. By pushing these two spreaders together, the red part of the button can be removed again.
If you don't have this whole "button assembly" thing, you can bypass the switch by soldering it together. It is convenient though.
I drilled a big hole first for the wires that come out of the switch box and need to connect to all the other stuff. I then (using the same screws as removed from the machine!!!) drilled pilot holes and screwed the switch box to the side. It's a lot easier to attach one screw and then drill the pilot hole for the other one in a spot where you know the other hole in the switch box will be.
Step 4: Creating the Quake: Wiring
At this point, we can break out the wire nuts. Because the power is AC, the polarity of connections doesn't really matter much. Make sure your mains power cord is UNPLUGGED!!! I wasn't paying attention and ended up with flying flaming copper bits in the bottom of my tub and blowing a fuse because the ends touched. Luckily I had gloves and goggles on. Don't let it happen to you.
A wire from the switch and a wire from the motor have to connect to the two ends of the cord. But before that, I tied a knot to keep the cord from slipping out of a hole I drilled in the side of the bin. To connect the leads, while the mains is UNPLUGGED, hold the wires together and twist the wire nut over top of the two wires. Righty-tighty, lefty-loosey.
Now that the wires are all in the right place, it's time to clean them up before the motor's fan cuts them. To do this, I took a plastic insulated electric staple, yanked the nails out, and drilled a little in the ends so that screws from the food processor could do the job. The screws are just long enough to bite into the plastic, but short enough to not poke fingers. I gathered up the extra wire and was ready to finish up.
Step 5: Creating the Quake: Closing the Box
The last thing to do is finish! Start by poking holes through the tubes again, and threading screws with washers. Then, drill pilot holes for the screws in the sides of the tub, attaching screws as you go. It helps to start on one side, then do the opposite side, and then the other two. I discovered that the design is extra clean if the tubes are screwed around the outer edge of the tub. Make sure that the rubber keeps the board kind of tight, centered in the middle of the top of the bin. The last thing to do is plug it in and go!
Thanks for looking!