# 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)

## Step 1: Design your bridge

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.

## Step 2: Supplies

Very, very simple:

-Popsicle sticks
-Wood glue
-PVC (optional)

## Step 3: Constructing

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.

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

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...

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.

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

## Step 7: Add MORE supports

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

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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me_zainab says: Jun 4, 2013. 2:25 PM
i am doing a school brigde project and this is very help ful
elizabeth_01 says: Nov 25, 2012. 2:49 PM
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!!!!!!!!!!!!!
sreed11 says: Jun 18, 2012. 3:38 PM
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 in reply to sreed11Jun 18, 2012. 3:39 PM
i will post pics tomorrow when we are done
Avi607 says: Dec 27, 2011. 8:37 AM
yea... i am kinda lost.
hannagranainotmyrealnamethough in reply to Avi607Mar 1, 2012. 3:17 PM
ME TOO!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!1
Elroy316 in reply to Avi607Jan 29, 2012. 3:12 AM

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.
If anyone can help please mail me at pravinrox@gmail.com.

Elroy316 in reply to Avi607Jan 29, 2012. 3:10 AM
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'.

Elroy316 in reply to Avi607Jan 29, 2012. 3:07 AM
Hello guys. I have an upcoming contest... Need help... Going to give the details in next comment...
zaronas in reply to Elroy316Jul 5, 2012. 6:41 PM
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
Mar 1, 2012. 3:17 PM
i cant beleif it takes about 140 popcicles stick!!! but.. can you be a little more spacific???? HELP!!!!!!!!!
Avi607 says: Dec 27, 2011. 8:36 AM
i didn't have PVC pipe so i just used rubber band.
roselle diez says: Sep 28, 2010. 11:33 PM
wow!!!its so nice!!!
christophee in reply to roselle diezDec 14, 2010. 5:30 PM
yeah IT IS!!!!!!!!
christophee says: Dec 14, 2010. 5:29 PM
you are the best website
wazupwiop says: Dec 9, 2010. 4:12 PM
A few years back, a friend and I competed in a popsicle stick bridge contest. We got second place against kids that had competed year after year. The main thing is the good supports. Our bridge held around 250 pounds before the supports gave out. The deck was still solid. I was able to sit on it afterwards, it was great.
Garrett Boon says: Nov 8, 2010. 9:24 PM
I love the idea of using PVC pipe for clamps. That is very simple and easy to make.
Garrett Boon says: Nov 8, 2010. 9:21 PM
The X's would have been more useful on the top of the bridge. Because the top chords are under compression, and they try to bend and will eventually buckle. The bottom chords are in tension, being pulled apart. While wood does eventually try to twist when under extreme tension, all you really need is straight pieces connecting the bottom. The X's would have helped more to be on the top. http://www.garrettsbridges.com/design/lateral-bracing/
aidmarsh says: Aug 29, 2010. 8:17 PM
how much does it wiegh????????
dillan_dt in reply to aidmarshSep 1, 2010. 1:11 AM
i dont know bra but i can hold a lot of weight silly assignment
bradjbear says: Oct 9, 2009. 8:40 AM
if it is just made of popsicle sticks how does it hold 205 pounds?
Architectural structure...civil engineering at work.
dodo91 in reply to bassclarinet23Aug 2, 2010. 7:53 PM
It is held together by sheer awesome.

But really, it's the triangles. Read the first couple steps.
pumablade says: Jan 5, 2010. 11:43 AM
dude that is toatallty awesome our teacher made us do a bride and this bride is so cool i hope i can do it right and get a a++++ thanks for the help
One of the people in our class did a design that held up to over 1200 pounds... I still remember some of the tricks
YOU MEAN BRIDGE RIGHT?
irockalot99 says: Jun 21, 2010. 11:54 AM
WHAT TYPE OF BRIDGE IS THIS???? I NEED TO KNOW FOR MY PROJECT ON BRIDGES. THANKS.
crazypenguin says: Jun 8, 2009. 9:01 PM
would hot glue work
jpenn in reply to crazypenguinApr 28, 2010. 3:45 PM
Actually wood glue would work much better as it is absorbed by the wood, whereas hot glue just sits on the surface.
yes
Matt526 in reply to crazypenguinJun 30, 2009. 2:06 PM
yes. it works even better
crazypenguin in reply to Matt526Jun 30, 2009. 7:51 PM
cool
KnexFreek says: Jan 31, 2010. 8:36 AM
I have a popsical stick bridge i built 4 years ago and it held 250 and did not break. I still have the bridge, and id would be happy to show it to you and prove itf you like.
jashinda hinton in reply to KnexFreekMar 17, 2010. 6:21 PM
thats cool ive never made a bridge before but i am dis year 2 of dem one out of popsicle sticks nd the other out of straws
KnexFreek in reply to jashinda hintonMar 17, 2010. 6:25 PM
Wow!
saheli in reply to KnexFreekJan 31, 2010. 3:57 PM
can u show it to me? i want to see what it looks like. i am curious about how it held 250 g :)
thx
KnexFreek in reply to saheliJan 31, 2010. 4:03 PM
it held 250 pounds and i will go find it now :)
saheli in reply to KnexFreekFeb 1, 2010. 10:25 AM
woah....in pounds.....even more amazed....wow.....thx for taking your time for this :)....i m really thankful
jashinda hinton says: Mar 17, 2010. 6:18 PM
this is cool i even have to do one for my science fair how fun is dat!!!!!!!!!
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