Model Bridge Design

Polycarbonate Heat Resistant Plastic and Impact Resistance

Garrett Boon — Tue, 31 Aug 2010 16:25:32 +0000

Polycarbonate is a clear, amorphous polymer that displays amazing physical properties, such as remarkable heat resistance, superior clarity, and supreme impact resistance that makes it virtually unbreakable. It is not uncommon for this type of thermoplastic polymer to be utilized for replacing glass or metal in demanding applications when the temperature doesn’t surpass 257° F.

There are different varieties of polycarbonate plastics, and not all of them are created equal or used for the same applications. Furthermore, some have higher performance levels than others. A good example of a top performer is PC 1000. This particular thermoplastic has many great features including:

High creep resistance
Good mechanical strength
Stiffness retention across an extensive array of temperatures
Suitable for food contact
Great dimensional stability (incredibly minimal water absorption and low coefficient of linear thermal expansion)
Good dielectric and electrical insulating properties.

As was previously mentioned, polycarbonates can be used in a number of applications, and while Polycarbonate 1000 is ideal for windows and other structural applications that are in need of strong transparent materials, it is also an excellent choice for electronic and/or electrical applications, as stock shapes created from this thermoplastic are machine grade.

World’s Longest Popsicle Stick Bridge

Garrett Boon — Mon, 30 Aug 2010 00:34:10 +0000

Here is the story of the Prairie Popsicle Stick Bridge told in video format. As far as I know, this is the longest working popsicle stick bridge that a person can walk across. If you know of a longer bridge that does the same, please let me know. The largest popsicle bridge was built back in 2008 in my dorm room at Prairie Bible College. For many nights I slept on the floor, as I was using my bed space as a worktable to glue the bridge together.

The testing of this bridge was a community event, as you can see the large number of people gathered to watch. This bridge definitely is one of my favorites that I have built over the years. Two years later people are still talking about it at the school.

K-Truss bridge built for Wake Tech intro to engineering class

bcmiller2 — Sat, 12 Jun 2010 19:22:41 +0000

K-Truss bridge

This bridge is supporting 191lbs of weight. It didn’t break, that was all the weight we could fit in the trash can. I believe this is close to the maximum load it could hold because the platform the jig is resting on was significantly bowed. The rest of the structure was rock solid. The construction of the bridge is popsicle sticks.

Wood Dash Kits

Garrett Boon — Fri, 04 Jun 2010 16:35:45 +0000

I am in the market for a used car. I could never afford a new car, so I must go for a used car. Sometimes when you buy a car, especially one that is used, you are not able to get exactly what you want. That is the beauty of being able to modify the car after you get it with extra accessories. This is where wood dash kits come in. Why settle for an ugly factory dashboard when you can easily get a much better looking dash kit and install it yourself. This accessory would be a great way to brighten up the look of a newly purchased used car. So, next time you are in the market for a used car, don’t pass up on a good car because you don’t like the looks of the interior. Replacement kits for just about every accessory you can think of are available online. Just run a google search and you will see what I mean.

Bread and Cookie Recipes

Garrett Boon — Sat, 29 May 2010 01:02:26 +0000

Cooking is a great pastime, which produces something in the end which many people can enjoy. I love food, mostly eating food, but have recently begun to enjoy cooking food as well. This is mostly the result of the hard efforts of my girlfriend, who has gotten me to cook a couple of meals with her. The first meal we cooked was a fancy dinner for her family. We used some recipes that she knew and some that we gathered from the internet.

I was in charge of baking the bread, although I had to be told step-be-step what to do. The bread was leavened, but for some reason it didn’t rise. So we ended up making the break into small cookie shaped pieces. They tasted quite nice for my first time making bread, even if they didn’t end up in the form that I had hoped for. I think next time I want cookies I will just use one of the many cookie recipes that are on the internet.

The rest of the meal turned out okay too. The family enjoyed it, and there was nothing left over. I think that is a good sign. We had sautéed sausage and beef with noodles and some kind of sauce that I still can’t pronounce the name for. We collected all the fancy glasses around the house and served cranberry juice or water as requested. We went with a restaurant theme for the dinner with us acting as the waiters.

All in all cooking supper was a great experience and introduction for me into the art of cooking. I definitely have a long way to go before I am proficient at making a good tasting meal, but with practice I should be able to get it. I will keep adding quality recipes to my repertoire of cooking.

Ryerson I-beamers’ 2009 Popsicle Bridge

Garrett Boon — Tue, 18 May 2010 14:11:51 +0000

This is a video I found on YouTube of an excellent bridge built for the Troitsky Bridge Building Competition. The only materials allowed for this competition are popsicle sticks, toothpicks, dental floss, and white glue. This is a very impressive bridge. It weighed 1.17kg and held 805kg. That gives it an efficiency score of 688.

Popsicle Stick Suspension Bridge

Garrett Boon — Wed, 05 May 2010 15:11:12 +0000

I have always wanted to build a model suspension bridge, and finally I have finished one. This is a popsicle stick suspension bridge. I created it from scratch, coming up with the design on my own. After testing it to failure I learned quite a bit about how suspension bridges react to loads. This model suspension bridge uses popsicle sticks as the main building material. The decking is cardboard, and the “cables” are 550 parachute cord (military surplus).

Testing the Suspension Bridge

Here is the video of the bridge being tested to failure. I have two different angles showed right after each other. I think this video is very enlightening as to how a suspension bridge reacts to a load.

It appears that the bridge failed due to uneven loading. The weights leaned to one side, and I over-corrected as I kept adding weights.

I did not come up with a good method of securing the cables to an anchor. You will notice in the movie that the ends of the bridge lifted up as the middle bent down, until a certain point where the ends of the deck pressed up against the cables themselves. If I were to do this again, I would have the cables already pressing down on the ends of the deck to help secure it in place. I think this would provide much better support to the bridge rather than what I did.

This suspension bridge was very flexible, as you can tell from the video. I read an article about building model suspension bridges that said it was difficult to get them flexible enough. Also, I did not have any hangers (vertical cables hanging off the main cables) on this bridge. I did not make any mostly because of the great difficulty in making them even and I did not know a good way to attach the hangers to the main cables. In real life, the cables are metal and have metal clamps and other devices that make this process easier. But I was using parachute cord.

Efficiency Score

Garrett Boon — Fri, 23 Apr 2010 19:00:06 +0000

To help clear up any confusion when I talk about the “efficiency” or “efficiency score” of the bridges I build. This is a mathematical equation to determine how well a bridge performed.

Simply take the mass that the bridge held, and divide that by the mass of the bridge.

Mass held
________ = Efficiency

Mass of bridge

Some confusion comes up when I weigh the bridge in grams while add weight to the bridge in pounds. These units do not have the same base, and cannot be divided against each other. I usually convert pounds to kilograms (1kg = 2.2 pounds) and then multiply the number of kilograms by 1000 to get grams.

So if my bridge held 54 pounds, I would convert that to kilograms. 54 pounds equals 24.54 kilograms. That equals 24540 grams.

To get the efficiency, I take 24540 and divide that by the mass of the bridge, which was, say, 33 grams. The efficiency score is then 744.

Short Pratt Truss Bridge Updated

Garrett Boon — Mon, 19 Apr 2010 19:53:15 +0000

This is the updated design of my Short Pratt Truss Bridge made from popsicle sticks. The only difference was the addition of 4 more popsicle sticks in key areas. I doubled up the angled sticks on each end, and made the lateral bracing into an X shape rather than a zig-zag pattern.

This bridge used 50 popsicle sticks, weighed 75 grams, and held 200 pounds. It’s efficiency score was 1212, which is the highest out of any popsicle stick bridge I have ever built.

Here is a video showing the testing of the bridge:

Purchase Blueprints for this Bridge

$5.95

Short Pratt Truss Bridge

Garrett Boon — Fri, 16 Apr 2010 15:23:40 +0000

This is the Original Design

Click here to see the new and improved version of this bridge

This is a popsicle stick bridge I built using the Pratt Truss design. This bridge is 13.5 inches long, 4 inches tall, and 3.75 inches wide. This bridge weighed about 70 grams and held 73 pounds before breaking. I used 46 popsicle sticks to build this bridge. That gives it an efficiency score of 474.

Pratt Truss Analysis

The last picture shows the truss analysis from the John Hopkins Bridge Designer program. If you watch the movie, you will notice that the front left corner and the back right corner started to bend a lot right before the bridge failed. The truss diagram shows that these popsicle sticks had the most weight on them, which probably contributed to their bending. To improve this design, I will double up the last diagonal popsicle sticks to account for the extra amount of force they have to withstand.

Also, the movie shows that the lateral bracing popped off right before the bridge broke. The bridge had been slowly leaning towards the left. I wonder if my standard method of just having one angled popsicle stick glued on each end for lateral bracing is sufficient. I think that having a full X pattern would be better. I will also make this change and see how it affects the strength of the bridge.