Zane Middle School shake table

Abstract

Final Shake Table design without the cart.

A Shake Table was designed and constructed to imitate earthquake magnitudes to help students at Zane Middle School to better understand seismic activity and allow them to test their own building structures.

Background

Zane Middle School is a STEAM ( Science, Technology, Engineering, Arts, and Math ) school that believes hands on learning is very important for student success. For several years Engineering 215 students at Humboldt State University have teamed up with Zane's faculty to help them achieve this goal. In Spring 2017, our team was challenged with the construction of a Shake Table that demonstrates shaking of an earthquake. Our Shake Table design specifically allows 7th grade students to learn about the seismic activity in Earth’s crust during an earthquake while also providing a way for them to be creative and test their own building designs.

Problem statement (Objective) and criteria

The objective of our design was to make the most realistic shake table design possible, and satisfy the needs of our client, Zane Middle School. Our client expressed their desire to illustrate the effects of liquefaction of earth during an earthquake and how the earth undergoes a wave motion at these times. Most standard shake tables don’t express this motion so this was one of our challenges. Aside from that, our primary concern was to ensure the device was safe as children would be interacting with it in close proximity.

Below is a table of our criteria and weighted values of importance that our team and client agreed upon:

Description of final project

This design meets the criteria and uses the Flex Board design combined with the Drill Sergeant’s power mechanism to achieve an efficient shake level that safely tests structures built by the students at Zane Middle School. Most of the materials were obtained from local stores or donated in order to reduce costs.

This shake table uses a drill to turn an axle, which translates movement along a metal shaft in order to shake the table top. The top of the table is composed of seven wooden slats, each 21 inches long, three inches wide, that are held together using plastic tubing and epoxy with small compression springs in between each slat. The structures that are built by the students will be held to the top of the shake table using straps that are connected to a few of the slats. The top of the table is supported by a total of eight compression springs that are connected to five of the seven wooden slats, three of the slats will have two springs connected to them, but two of the slats will only have one spring. The compression springs that support the tabletop are held in place by a combination of epoxy, setting the end of the spring into the board one-quarter inch, and also compressing the springs one-quarter inch using a wire clamped with aluminum ferrules.

The shake table is mounted on a metal cart that is almost four feet tall, two feet long, and three feet wide. The cart rolls on two regular and two locking casters to prevent movement during testing, but also provides an outlet to power the corded drill that shakes the table top. The cart is big enough to allow the students to watch the structures be tested and has shelves beneath the shake table to allow for more storage space.

Costs

Costs included in this project are shown below. Many of the materials were purchased while some were donated.

Testing Results

When testing the shake table for the first time, it showed that the flex board method worked and created the wave motion that was originally theorized but there were still a few issues that needed to be mended. These issues included the vinyl tubing coming out of the end wood slats and the screw connecting the steel bar to the cam system jamming and stopping the movement. These minor complications were remedied by threading the left over spokes from the axle hub through the vinyl tubing to hold the it place. The jamming screw was fixed by adding thread lock to the end of the screw to keep it from over-tightening on the steel bar.

How to Build

How to Build a Shake Table:

1. 

   Boards with tube and mini springs.

   Drill two holes through 7 wood boards. Thread vinyl tubing through each board and hole, putting mini springs in between each board.
2. 

   Pockets for springs being drilled.

   Drill pockets same size as larger springs into the table top boards and the base board. Two on each of the end boards, two on the middle board, and one in the middle of the surrounding board. Refer to AutoCAD illustration above.
3. 

   Will Crimping springs in place.

   Place springs in pockets of both board. Run wire cable through base board, spring, then the table-top. Crimp the wire using aluminum ferrules, to hold the springs in place in between the boards.
4. 

   Gluing springs in pockets.

   Glue the springs in the pockets, with epoxy for extra support and durability.
5. 

   Drill Mechanism.

   Get axle hub from a front wheel of a bicycle, remove spokes, and seal axle into block of wood with epoxy. Attach a cam system (wiggle waggle) onto one end of the axle. Connect a steel bar onto the cam system. Then tighten the drill to the other end of the axle.
6. 

   Drilling wood block with axle onto base board.

   Attach the wood block with the axle hub and cam system by drilling screws through corner braces onto the base board and wood block.
7. 

   Final Design.

   Connect two wood blocks underneath the table top and sandwich the steel bar between them, bolting it in place. Now that everything's connected, plug in the drill and start shaking.

How to Video