Abstract[edit | edit source]
The purpose of this project is to design a safe bridge tester system that is able to measure the strength and endurance of bridges under pressure in pounds per square inch. Through the Engr215 Introduction to Design class at Humboldt state University, students from Team Burke der Meister: Chris Corona, Trevor Herron, Oliver Ruiz Hurtado, Drew White; designed a bridge tester machine that will be integrated into the engineering section of the STEAM Program at Zane Middle school for projects and competitions.
Background[edit | edit source]
Zane Middle School introduced the STEAM program in the fall of 2013 that allowed students to include Science, Technology, Engineering, Art and Math into their already existing curriculum. The uniqueness of the STEAM program allows students to be exposed to design electives for real world situations. Zane Middle School came to the Cal Poly Humboldt Engineering Department in the spring of 2014 with the intent to improve their STEAM program.
Problem statement and criteria[edit | edit source]
The objective of the Engineering 215 group, Bürke der Meister, is to design a system able to test the strength and endurance of student built bridges by applying distributed force along the model bridge deck. The machine will measure the amount of pressure a student's bridge can withstand before breaking. This allows the students to record this data and use it in calculations and report writing.
|Safety||10||The bridge tester should include a safety switch to prevent injuries.|
|Functionality||10||The machine must be easily operated and work every time while providing consistent pressure readings.|
|Educational Value||9||Information gathered from measurements and calculations will be utilized by the STEAM program appropriate for 6th to 8th grade education.|
|Durability||8||The machine must be constructed with materials to ensure proper use for 10 years and withstand long periods of inactivity.|
|Mobility||8||The machine will have wheels for easy transportation and must be able to fit through doors.|
|Cost||6||Each material for the project must not exceed 25 dollars in cost and must stay under the specified budget of 400 dollars.|
|Up-Cycle||5||50 percent of all materials used will be from recycled or reused products.|
|Aesthetics||4||The bridge tester needs to portray the purpose of design and have the appearance of a well-built professional project.|
Description of final project[edit | edit source]
RIPSAW shown above generates mechanical pressure from the McElroy sidewinder shown to the right which allows for pressures upwards of 600 psi to be applied to the model bridge decks. The sidewinder dimensions are 21.4"x 12.5"x 10.25" and allow for 18" of travel on the drive screw assembly. The sidewinder comprises of a load cell measurement system and integrated dry pressure gauge to display the desired pressure. The threaded drive screw assembly is controlled by the operator and can be moved up and down to a desired height. Once in position, the drive screw assembly is rotated by the knob clockwise to apply gradual pressure and counter-clockwise to relieve pressure. The McElroy sidewinder is bolted to a fabricated C-bracket frame and C-channel platform to ensure stability. The dimensions of the channel platform are 3'x 6"x ½" and is welded to two 12"x 12" x 1/4" iron plate to support the base of the model bridges. The C-bracket runs 3" out from the back of the C-channel and up 17.7" and 14" across the top where the sidewinder is mounted. The sidewinder and frame assembly are bolted to moveable cart that comprise of caster wheels with dimensions 24"x 18"x 42". The dimensions of RIPSAW allow for the complete assembly to be easily stored and maneuvered for Zane Middle School teachers.
Cost[edit | edit source]
The bridge tester items, purchase size, quantity of items, team cost, individual retail cost and total cost of the final design bridge tester are summarized below in Table 1, Table 2, and Table 3.
|Bridge Tester Item||Purchase Size||Quantity||Team Cost||Individual Retail Cost|
|Cart with Wheels||(24inx18inx42in)||1||Donated||$106.99|
|Black Spray Paint||12 oz.||1||$8.49||$8.49|
|Red Spray Paint||12 oz.||1||$8.49||$8.49|
|Matte Clear Coat||12 oz.||2||$4.99||$4.99|
|Bridge Materials||Purchase Size||Quantity||Team Cost||Individual Retail Cost|
|Fishing Line||1500 yards (50lb Test)||1||Donated||$117.99|
|Popsicle Sticks||1000 Pack||2||$5.99||$5.99|
|Popsicle Sticks||100 Pack||1||$3.49||$3.49|
|Wood Glue||4 oz.||4||$2.49||$2.49|
|Fine Sand Block||(4.8inx2.9inx1in)||1||$2.15||$2.15|
|Clear Coat Protection||1.0|
|New Black Spray paint coat||1.5|
|Total Task Hours||3.5|
Testing Results[edit | edit source]
To test the final design created, each team member made several types of bridges. These bridges were made with stronger equipment and materials than would be available to the students at Zane Middle School to test the limits of RIPSAW. Different variations of bridges were constructed to test the flexibility of bridge design the machine could effectively test. These bridges are shown below. RIPSAW was able to successfully test and break each of the bridge types while giving accurate information about how much pressure each one of them could take. All of these tests gives the team a good inclination that the machine operated the way it is supposed to.
|Test||Bridge Type||Pressure (PSI)|
How to Use[edit | edit source]
How to Build[edit | edit source]
Measure all given metal components from the materials list to the lengths shown below:
- Square Tubing: 2- 3" sections, 2- 17.7" sections, 2- 14" sections
- Iron Plate: 2- 12" x 12" plates
- Square Tubing caps: 2- 1.5" x1.5" sheets
- Rectangle Tubing: 1- 6" section 1- 12" section 1- 24" section
Discussion and next steps[edit | edit source]
Several obstacles arose during the development process of our design that impacted the final design. Many changes to the design occurred to accommodate the various criteria and constraints.
The solution of "Project RamRod," which scored the highest on the Delphi matrix, had a lot of components that were going to be donated. An integral part of the design is the pump that supplies pressure to the ram. This pump is powered by Alternating Current, which allows it to be plugged directly into the wall socket. This specific pump that was supposed to be donated was no longer available. This meant that we would have to buy a pump and this did not meet our cost constraint for the project.
Different alternatives to using the pump were considered, one of which would include an air compressor that that would serve the same purpose. While the air compressor would serve the same function as the pump, it created more obstacles to overcome. The air compressor that could be used was powered by direct current. This meant that in addition to replacing the parts from the compressor that needed it, e.g. the connecting hoses, more parts would have to be located and purchased in order to achieve the constraint of durability. A tickle charger would have to be applied to the power source, a battery, to increase the lifespan of the battery. Another solution researched was to purchase an inverter. An inverter converts Direct Current to Alternating Current. Once again this solution created problems with achieving the cost constraint.
While gathering materials for the project, Rick White, Gas Operations Manager with PG&E, had a piece of equipment that is no longer in operation and donated it to the project to be repurposed. This job specific piece of equipment would in fact take the place of several different components of the design. By using the McElroy Sidewinder, the need for a power supply source, pressure gauge, ram, and pump would no longer be necessary. All of the electrical components to the design would be obsolete. The acquisition of the mechanism would have the biggest impact on the specifications of the final design.
Video[edit | edit source]
References[edit | edit source]
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