Project data

## Abstract

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

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

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.

Table-1: Weighted Criteria
Criteria Weight Constraints
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

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

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.

Table-1: Bridge Tester Materials
Bridge Tester Item Purchase Size Quantity Team Cost Individual Retail Cost
McElroy Sidewinder (10.25inx12.5inx21.4in) 1 Donated $1,583.00 Iron Plate (12inx12in) 2 Donated$145.90
Cart with Wheels (24inx18inx42in) 1 Donated $106.99 Square Tubing (48inx1.5inx1.5) 4 Donated$34.24
Rectangle Tubing (72inx1.5inx0.75in) 1 Donated $20.94 C-Channel (25inx6inx2in) 1 Donated$20.50
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
Bolts (3/8inx3in) 2 $0.85$0.85
Nuts (3/8in) 2 $0.23$0.23
Washers (3/8in) 6 $0.23$0.23
Total - - $30.50$2190.99
Table-2: Bridge Material Cost
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 Dowels 8 Pack 5$2.99 $2.99 Wood Glue 4 oz. 4$2.49 $2.49 Fine Sand Block (4.8inx2.9inx1in) 1$2.15 $2.15 Bass Wood (36inx3inx1/16in) 8$1.79 $1.79 Total - -$56.85 \$174.84
Table-3: Maintenance Cost in Hours per Year
Dust Equipment 0.5
Lube Wheels 0.5
Clear Coat Protection 1.0
New Black Spray paint coat 1.5

## Testing Results

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.

Table-4: Testing Results
Test Bridge Type Pressure (PSI)
1 Truss 270
2 Arch 100
3 Girder 600
4 Suspension 275

## How to Use

1
Lift the Drive Screw as high as it can go. Open the Load Cell Assembly by rotating the handle counter clockwise.
2
Insert polyethylene pipe into slot. Close Load Cell Assembly by rotating handle clockwise.
3
4
Place bridge on bridge mounts. (if needed)
5
Lower Drive Screw until the loading block is just above bridge. Turn knob until the loading block rests on the bridge. Gently turn knob until desired pressure on bridge is applied. Lift Drive Screw to remove loading block and clean debris on surface. For continual use repeat steps 5-10.

## How to Build

1
Make sure to have all materials shown in Description of Solution: Level, Angle, Cordless Drill, Drill Bits, Ballpeen Hammer, Vise-Grips, Screwdrivers, Angle Grinder with wire and sandpaper wheels, Standard Wrench set, Standard 3/8" Socket set, 3/8" Socket Wrench, Tape measure, MIG Welder, Plasma Cutter, Band Saw and Wire Cutters
2

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
Once these segments are measured, use BandSaw to cut all Square and Rectangle tubing. Plasma Cutter to cut Iron plate.
3
Weld 3" section of square tubing to c-channel. Measure to 12.5" on side wall of C-channel. From the center line measure 5" in both directions for placement of 3" sections of square tubing. Once tacked into place, finish welds around 3" section to C-channel as shown.
4
Weld 17.7" sections of square tubing vertical 90 degrees from the 3" section and 14" sections horizontal 90 degrees to the 17.7" square tubing as shown
5
Weld 1.5" x 1.5" caps onto vertical 17.7" section tops as shown. Tack a short segment of metal to top of cap for easier operation.
6
Weld 12" sections of iron plate to C-channel as shown. Where the two plates meet is the 12.5" center point on the C-channel. Tack into place and weld 2" sections of a bead around each edge and along the top of iron plates.
7
Grind down all edges and rust from C-bracket and C-channel for aesthetic and safety purposes as shown. Be sure to use one edge of grinder to ensure injury does not occur.
8
Slide Sidewinder base onto C-bracket and drill out 1/2" holes where drive screw is mounted through C-bracket and Sidewinder base.
9
Remove Sidewinder and flip C-bracket on its side. Drill out 13/16" holes along the center line of C-channel and 4" from ends of iron plate. These holes will be used for mounting C-bracket assembly to the moveable cart. Align the C-bracket to your preference and drill 1/2" holes through the C-bracket holes and into cart.
10
Spray paint C-bracket and cart to desired color as shown. This prevents future rust issues and adds to aesthetics of design.
11
Once paint has dried, mount C-bracket to cart using 3/8" x 3" bolts and washers.
12
Mount Sidewinder to top of C-bracket using hardware provided from Sidewinder.
13
Cut a edge of polyethylene tube 3/4" from its edge and 1/2" wide for rectangle tubing to slide into. Be sure to do this across the diameter of the polyethylene tube by using a grinder as shown.
14
Once polyethylene tube is cut the tube can be painted to a desired color or left yellow. Insert the polyethylene tube into Load Cell assembly and tighten handle. Slide in a metal rectangle section of tubing into polyethylene tube slot and it is ready for use.

## Discussion and next steps

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.

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Page data
Type Project model bridge tester, pressure, strength, sidewinder, iron plate, cart, tubing SDG04 Quality education Drew White, Chris, Trevor Scott Herron, Kathy Nativi 2014 CC-BY-SA-3.0 Cal Poly Humboldt, Category:Engr215 Introduction to Design, Category:Zane Middle School English (en) 531 Drew White, Chris, Trevor Scott Herron, Kathy Nativi (2014). "Zane Middle School RIPSAW". Appropedia. Retrieved August 9, 2022.
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