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Picture of Popsicle Stick Bridge
The popsicle stick bridge is a classic science demonstration and competition. Every year many students world-wide build bridges made soley from popsicle sticks and glue, to see which designs can hold the most weight.

We built one, using maybe 140 sticks, give or take a few. Not expecting it to hold much weight, we were surprised by how strong it ended up being! (results in last step)
 
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Step 1: Design your bridge

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There are many ways to build bridges, both real bridges and popsicle stick bridges. Do some research, be creative, and remember - triangles are strong.
A triangle spreads out weight and is much more stable than a simple rectangle or square support. Be sure to incorporate lots of triangles into your bridge design. More popsicle sticks doesn't necessarily mean a stronger bridge.

In fact, according to the internet, "If there is a single most important shape in engineering, it is the triangle. Unlike a rectangle, a triangle cannot be deformed without changing the length of one of its sides or breaking one of its joints. In fact, one of the simplest ways to strengthen a rectangle is to add supports that form triangles at the rectangle's corners or across its diagonal length. A single support between two diagonal corners greatly strengthens a rectangle by turning it into two triangles."[link]

My design consists of two main bottom supports, and two across the top, and then a lot of triangles across the sides, the top and bottom, and going from the bottom of one side to the top of the other. Very similar to the one in the diagram.

Draw your design on paper, and estimate the number of sticks you will need.
Be creative with your design!

Step 2: Supplies

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Very, very simple:

-Popsicle sticks
-Wood glue
-PVC (optional)

Step 3: Constructing

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Some things to keep in mind:

A clamp of some sort is a good idea when constructing. I used Tim Andersons method, but bulldog clips work just as well. Clamps are important because most of the popsicle stick aren't flat, so if you don't clamp them when you glue them together your bridge probably won't hold together very well.

Don't pinch your fingers.

Keep your workspace clean! I glued everything on top of a piece of paper, as I have a tendency to get glue everywhere.

Step 4: Start small

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I started by making smaller pieces that would be easier to glue together. I counted out how many I needed and started with that. Once they'd dried just enough to not fall apart, I moved on.

Step 5: Get bigger...

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I glued the smaller pieces together, to create the main supports for the bridge. I then repeated the process and made some slightly shorter pieces for the top.

Step 6: Add supports

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I started with each side of the bridge, keeping them symmetrical, then flipped each side and added more.

Step 7: Add MORE supports

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I added angled supports across the bottom to start with, to hold it together, then across the top.
Keeping in mind the idea that triangles are strong, I added some center supports going across as well as up and down.

Step 8: Finish it off

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I finished it off with some pieces across the top. I'm not sure they add any structural support, but they look good.
I also touched-up on the glue where it was looking scarce, and added more horizontal supports.

Lastly I sanded the top, to make it completely flat so that weight wouldn't be focused on any one point

Step 9: Break it! (Or try)

This is the last step, obviously.

We decided we'd test the bridge with sand in a bucket. We bought two 60 lb bags of sand, thinking surely my bridge would break under 120 lbs.
It held 120 lbs.
We emptied the sand out, and added 40 lbs of water, then added all the sand back. It still held.

We tried the intern, and it still held.

Two days later we bought another 150 lbs of sand. The bridge finally broke under 205 lbs!

How much does yours weigh?
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EatMyHat1 month ago

Mine held 492 lbs! Anyone held that much?

PatrickA22 months ago

How about using a glue gun for steps 3-5? It dries faster!

trbblk4 months ago

Thanks for this project. Its working out great so far!

FianaS4 months ago

Is it ok to use ordinary glue? and What are those gray things on the side of the bridge to hold it up?

Sk8ty4 months ago

how much did your bridge weight

Is it okay to use ordinary glue?

GavcrafterB7 months ago

AWESOME thats really cool! also congrats nicholas

OMG THIS PROJECT WAS SOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOO GOOD I WON 1ST PLACE IN STATE AND WON 200 DOLLARS TY SO MUCH!

saifa18 months ago

wow this is nice but i would appreciate a video of how you did it or a more detailed one.

this isn't bad its awesome !!!!!

Gabethegr89 months ago

This project was so awesome when I entered it in the science fair that I won 1st place and won a $100 Visa Gift Card. Yay

IsabellaB19 months ago

Cool design! I'm doing this for class and this would probably work super well! Thanks for the tips and info.

Ty! I got a perfect score because of this!

Anu Susan10 months ago

Thank you for this good instructions.

nice 1 this will help me alot..........

giggles2321 year ago

gahhhh

Thank you for this wonderful instructable!!

Camby23mvp6 years ago
I am a science/tech teacher and my kids loved this. I had the students draw blueprints prior to building the bridge. Instead of pop sticks, I used balsa wood. This is by far the best project of the year!
drinkmorecoffee (author)  Camby23mvp6 years ago
I'm so glad you found it so useful! Post pictures of the bridges!
what is the silver thing you used to test your bridge? What's it called and where can I find one?

I could be wrong, but that "silver thing" looks like a slotted aluminum extrusion. They can be found here: http://www.adafruit.com/products/1302, but I'm sure you could probably find them somewhere else with a quick Google search

its just a deck of cards
we did this when i was in the 8th grade only with toothpicks. its amazing how much weight those little things can hold with a little glue.
i did in 7th grade and it held 20 lbs. designed useing computer
Sharky19341 year ago

Thanks for the steps! I won the competition and won a $150 Gift Card!!

loonyzac1 year ago
WTF so strong :)
hsaeed31 year ago
I'll be trying to make that in a Bridge Competition on 11th October, 2013.. I wish i don't mess up! :P Can you explain the (STEP 7) a bit??
me_zainab2 years ago
i am doing a school brigde project and this is very help ful
Can someone Please answer??? I need to right a supply list for a school project and I dont know that the silver thing on top is! PLEASE ANSWER!!!!!!!!!!!!!
Avi6073 years ago
yea... i am kinda lost.
Elroy316 Avi6073 years ago
Hello guys. I have an upcoming contest... Need help... Going to give the details in next comment...
so im going to venture that i am quite a bit late in answering your question but for future reference:
i was in a class at school where we had to build a russ bridge that could hold as much as possible.

my design was something like the picture it was made out of toothpicks the trusses were three toothpicks in a triangular fashion and as long as they needed to be.
i made my bridge extremely sloppily and it still ended up being able to have me stand on it at the time i weighed somewhere in the range of 120-130 pounds

i suspect if one were to take the same design and make it extremely not messily it would do very well.

one thing i might try because of the materiels you have availible, make all the colomuns and trusses out of triangles of popsicle sticks. make the bottom have a open faced rectangle with the straws in that and have notches in the straws to hold the trusses in.
i would say make the base out of every other one a straw then a Popsicle stick

one thing i didnt draw is that you make an x with two more trusses between the bottom and top of each side
bridge design.png
ME TOO!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!1
Elroy316 Avi6073 years ago

Judging Criteria:
The winner is determined by a point system as follows:
Complexity - 10 points : The number of purposeful members involved in the design.
Aesthetics - 5 points.
Engineering - 10 points : How much thought is placed into the design, where the connection points are and what member shapes are used in the design.
Workmanship - 5 points : A bridge that is "clean", such as nice glued edges, members matching at connections and nice sanded edges.
Efficiency - 30 points.
Rolling loads test- 20 points.
If anyone can help please mail me at pravinrox@gmail.com.

Elroy316 Avi6073 years ago
I think this place is good. Nice site...
Heres the problem statement...
Construct a stable truss bridge of span 20 inches, height 5- 6 inches and internal width 4 inches with hollow and solid members (straws and Popsicle sticks) that sustains a minimum load of one kg.
The deck should be essentially made of straws. The loads will be uniformly/non-uniformly placed on the deck. The bridge will also be tested for its efficiency, rolling loads, complexity, aesthetics and workmanship. Paper (provided) can be used for joints consisting of three or more members.
The efficiency of the bridge will be calculated as follows-
Efficiency = Maximum load sustained by the bridge/Weight of the bridge.
Maximum use of straws is suggested as efficiency will be multiplied by the factor 'Number of straws/Number of Sticks used'.

sreed113 years ago
im actually going to a bridge building contest tomorrow. last year i did it and mine held like 35 lbs. well thats ok because me and my partner still won first place. but this year we are aiming to achieve even more weight on our bridge. so this was very helpful. i will share this page with him on our way down to atlanta ga tomorrow.
sreed11 sreed113 years ago
i will post pics tomorrow when we are done
i cant beleif it takes about 140 popcicles stick!!! but.. can you be a little more spacific???? HELP!!!!!!!!!
Avi6073 years ago
i didn't have PVC pipe so i just used rubber band.
wow!!!its so nice!!!
yeah IT IS!!!!!!!!
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