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Testing 

The bridge will be tested on these requirements 
• 32mmx25mm “vehicle” traversing the bridge without obstruction
• Articulation of 140mm vertically
• Bridge rests on 60mm abutments
• Minimum lift of 5mm while exerting 10g of force
• Support between 18.9 to 20 kg load
• Weight of bridge (with articulation apparatus removed) less than 85g.
• Max vertical deflection of 25 mm.

Block Slide Test

The purpose of this test is to demonstrate that a “vehicle” can traverse the bridge deck unobstructed. This will be done by dragging a 32mm x 25mm block across the bridge deck with a string.

Procedure for completing test 

  • Bring equipment to the testing site, block with string, phone camera and balsa wood vertical lift bridge. 

  • Set up block and string inside of the bridge in preparation to traverse. 

  • Thread string through the bridge so that once pulled, the block will travel the span of the bridge. 

  • Gently pull string and demonstrate the block traveling the span of the bridge without any obstructions.  

  • Document process with smartphone camera. 

The testing process went smoothly, and all the equipment used behaved in an expected way. The block was able to traverse the entire length of the bridge deck without running into any obstructions.   

 

Weight Requirement

The Balsa Wood Vertical Lift Bridge has a series of testing requirements necessary for the proper completion of the bridge. The requirement that will be addressed in this test is that the bridge must weigh less than 85g.  

Procedure for completing test 

  • Bring equipment to the testing site, scale, phone camera and balsa wood vertical lift bridge. 

  • Turn on scale and press the tare button to zero the scale to 0g 

  • Place span portion of the bridge (not including towers or lift mechanism) on the center of the scale. 

  • Wait 10 seconds for the scale to produce an accurate reading. 

  • Photograph the scale readout for the weight to be documented in the report.  
     

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The testing process went smoothly, and all the equipment used behaved in an expected way. The bridge met the weight requirements as it weighed in at 82g which is below the max of 85g 

 

Force to Lift Requirement

Geometry Requirement

Force to Lift Requirement

The purpose of this test is to demonstrate that the bridge can articulate while applying a minimal amount of force. The bridge was tested on articulating vertically so that a piece of 20lb printer paper could slide underneath while exerting 10g of force.  

 

Procedure for completing test 

  • Set up vertical lift bridge on table, position so lift is spaced evenly between the towers. 

  • Using the rubber bands, attach the 10g weight on the lever arm while the lever is at 90 degrees in the horizontal direction, so that the weight will pull the lever down. 

  • Wait for movement to be complete before attempting to slide the paper stock under the bridge. 

  • Repeat steps 2 & 3 three more times to complete four trials, each time filling out data table below.  

    This test went as planned and in all four trials the bridge was able to lift enough from the 10g force for the piece of 20lb stock paper to slide underneath.

The purpose of this test is to prove that the bridge adheres to all building constraints that are in place for the project. The constraints that will be tested are the weight, length, and the ability to rest on the required abutments

Testing Procedure

  • Bring equipment to testing site, scale, phone camera and balsa wood vertical lift bridge. 

  • Turn on scale and tare to 0g 

  • Place span portion of the bridge on the center of the scale. 

  • Wait 10 seconds for the scale to produce an accurate reading. 

  •  Photograph the scale readout for the weight to be documented in the report.  

  •  Using the measuring tape, record a reading for the longest length of the bridge deck. 

  • Using the lift mechanism raise bridge to fully lifted position. Measure the distance from the bottom of the bridge to the ground.  

  •  Place bridge on the 60mm blocks so that they are directly underneath the towers. 

  • Judge if bridge can maintain stationary while resting on blocks.

 

It was found that the bridge met all the requirements tested for in this section, however this demonstrates there is room for improvement in the bridge design. Since the bridge was both underweight and over length, a design change could have been made to increase the bridge's strength by making it both shorter and heavier.

 

Deflection Requirement

The purpose of this test was to measure the bridges deflection while adding weight approaching the maximum load. 

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Procedure for completing test 

  • Attach eye hook and washer to the hole located in the center of the bridge span. 

  • Set up bridge span across a gap measuring 500mm 

  • Attach fishing scale to eye hook, and the bucket to the fishing scale, so that when water is added to the bucket a weight measurement will be seen on the scale.  

  • Add water to the bucket until the scale displays 5kg of weight. 

  • Measure deflection in the bridge at the center by measuring the distance the bridge has dropped from its original position. 

  • Repeat steps 4&5 using 5kg increments until 20kg of weight is obtained or until the bridge fails. 

  • Record and make a graph of data.  

​

The results of this test demonstrated that the bridge was able to maintain most of its rigidity up until the point of fracture. The maximum deflection before fracture was 3mm, an acceptable amount for the bridge project. 

Load Requirement 

The purpose of this test was to measure the bridges maximum load. The predicted load was 20kg.

 

Procedure for completing test 

  • Attach eye hook and washer to the hole located in the center of the bridge span. 

  • Set up bridge span across a gap measuring 500mm 

  • Attach fishing scale to eye hook, and the bucket to the fishing scale, so that when water is added to the bucket a weight measurement will be seen on the scale.  

  • Add water to the bucket until the scale displays 5kg of weight. 

  • Measure deflection in the bridge at the center by measuring the distance the bridge has dropped from its original position. 

  • Repeat steps 4&5 using 5kg increments until 20kg of weight is obtained or until the bridge fails. 

  • Record and make a graph of data.  

​

 

The testing process encountered some problems along the way, but the test was completed overall. The first problem encountered was attaching the scale to the eyehook. In the first attempt a key ring was used. The key ring was successful for the first half of the test, but it broke in the second half. A carabiner was used to replace the broken key ring and remained successful for the remainder of the test. The goal for this test was for the bridge to support a weight of 20kg. The bridge ended up braking at just under 18kg, so the goal was not reached. After inspecting the bridge, it was determined that the reason for failure was dure to the method of fastening the bridge pieces together. The bridge separated at the joints; the actual bridge members showed no sign of breaking.  

 

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