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Physics Balsa Bridge Building Contest

 

2010

 

Photos and Design and Workmanship Comments

Contest Website: http://www.balsabridge.com

Workmanship could be improved. Rough saw cuts are obvious. Compact, low structure is beneficial. Thin roadway is advantageous.

74.85 kg

Graceful arch. Difficult to keep ends from bending out. Linking pieces between arch and road deck need to be carefully connected.

15.75 kg

Workmanship is clearly questionable here. Asymmetry of structure mean forces (weight) will not be equally distributed. Excessive use of cross pieces at centre. Some of these could be removed, with a focus only at the point where the load will be applied.

68.65 kg

Arch in this entry is strictly decorative. What stands out here is the lenticular (lens-shaped) main structure under the roadway. A very nice design and a tricky structure to build.

81.05 kg

Better workmanship was needed for this structure. The small feet have been added as an afterthought and they do not appear to be well built. This structure did receive a 2nd place award in the "most unusual" category. The actual roadway does not really meet the requirement of it being "approximately level", except in the centre portion.

15.75 kg

Basic truss design, although no triangular section in middle. Note thin roadway and cross pieces only where needed, to support the test frame.

40.10 kg

Structure lacks a key, single long beam to serve as the base. It appears that the feet sections have been added on as an afterthought. This bridge held less than a simple bridge consisting of just feet and two 45 cm beams would likely have held.

10.40 kg

Elegant, simple structure with clean, sharp cuts, reflecting good workmanship.Single post at centre means that this bridge was tested with two bolts on the test frame. Note how the diagonals, under the roadway, meet the vertical feet at least 2.0 cm above the ground, thereby meeting the 40 cm x 2 cm board rule.

98.40 kg (5th place)

Standard "queen post" or split "king post" design. Thin roadway, supported only where needed. Ends of roadway not glued down as roadway strips tend to "curl" upwards as incresing load is applied. Decorative features do not add strength to this structure.

58.95 kg

"Tarzan" or high-road structure. Very large footprint. Winner of "most unusual" category.

24.25 kg

Main horizontal beams were not long enough. Extensions added to feet are used to reach 40 cm span requirement but in so doing leave a weak point. Roadway is thicker than it needs to be.

38.10 kg

Good workmanship. Upper triangle could be removed, leaving a basic truss design. Wood from top could then be used for better horizontal beams.

15.90 kg

Can't get much simpler than this, at least in terms of appearance. Basically horizontal beams with extensive cross bracing. This design is subject to excessive bending (one of the contest rules identifies excessive bending as a drop of more than 1.0 cm at the bridge centre.

36.60 kg

A-frame (above roadway) is made of double-stacked beams. Would have been more effective to use these as the main horizontal beams. The upper portion does not form a unified triangle with the horizontal beams.

17.75 kg

What an interersting structure. Laminated strips used to produce arches. These are thick laminations and the difficulty in bending such thick pieces is apparent in the asymmetry of the arches. The curved sub-arch is needed to keep the main arch in place (a tie rod) but it needs better connection to the outer arch.

25.40 kg

Using double-stacked 3/8x1/4 beams for main horizontals. Simple, effective pedestals (feet). Thin roadway. Cross braces mainly where needed.

35.30 kg

Excellent workmanship. Double-height horizontal main beams are a good idea. Thin roadway at top of truss is effective.

27.75 kg

Definitely unusual and unorthodox. Attractive design, lacking strength in centre. Double height horizontal beams are helpful.

29.55 kg

Basic truss design. Double horizontal beams would have helped the strength of this structure.Triangle (diagonal) pieces are not properly integrated into the horizontal pieces.

42.75 kg

Classic truss design. Double horizontal beams. Diagonals interlocked below the horizontal beams. Very thin roadway.

102.75 kg 4th place

Compact design with good workmanship. Nicely reinforced at centre, where load will be applied.

60.70 kg

Very roughly built, incomplete structure. Pedestals (feet) not vertical.

11.50 kg

Definitely a novel structure.Some asymmetry visible in this photo.

25.75 kg 2nd Place for Most Attractive Bridge

Basically laminated horizontal beams that should have been a little longer. Offset pieces were needed to extend the effective length of the beams. Pedestals (feet) could have been finished with better workmanship. Stiil, the strength of this bridge surprised everyone, including its builders.

108.75 kg (Third Place)

Terrific workmanship in a structure designed to mimic suspension-style bridges. A worthy winner in the worksmanship category. Clearly not a structure built for strength.

13.80 kg.

1st place Workmanship and Design, 1st Place Most Attractive Bridge.

Arch structure using fairly thick pieces for arch. Compact design with good tie-rod to keep arch shape locked in place. Decorative touches on outer edge of arches.

84.95 kg

2nd Place Workmanship and Design

Classic truss, three-panel triangular sections, with below-centre support.

157.80 kg, 2nd Place

Workmanship could be improved significantly. Stcked (double) horizontal beams would be better in this case. Elevated structure at ends is too short to provide any meaningful vertical support.

22.00 kg

An amazing structure with excellent workmanship. Beautifully built arches that set a new standard. This bridge was not only the winner of the 2010 contest, the mass it supported is the second-highest of all 30 years that the contest has run.

160.95 kg 1st Place

3rd Place Workmanship and Design

3rd Place Most Attractive Bridge

Classic truss design. A bit of asymmetry. Some more attention to detail in making cuts would have made for a cleaner looking structure.

55.70 kg

Double-stacked horizontal beams. Thin roadway, not glued down at the ends. Note Dremel grooves on upper structure. Used to reduce overall mass to the maximum of 100.0 g.

60.50 kg

Use of notching would have helped this structure perform better. The upper portion is too high to work effectively. Some good bracing beneath the roadway.

29.65 kg

Lots of potential here. Truss framework is well built. Moving pedestals inward would have been helpful.

24.40 kg. 3rd Place Most Unusual (although not that unusual)

Good basic design, built over limit, necessitating considerable "shaving" which likely weakened the structure. Diagonals in centre panel would work better if flipped vertically, or replaced by corner-to-corner diagonals.

33.80 kg

Major last-minute changes have weakened the performance of this structure. What remains is a box girder, essentially two walls made of stacked beams topped by a thin roadway.

34.85 kg

Excellent workmanship with a lot of high-quality notching (interlocking) of pieces. A high-road structure where the load is delivered at the apex (or vertex) of a triangular frame.

39.15 kg

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