Popsicle Stick Bridge

The goal of this project was to build a bridge using only popsicle sticks and glue that could span 32". Guides for each joint were designed in Fusion 360 and 3D printed out of PLA to make building the trusses much quicker. In total, four corner guides and ten joint guides allowed for not needing to measure any of the member angles. The guides were designed to be able to be universal by fitting any joint, firmly hold at least five popsicle sticks on top of each other, and not stick to the popsicle sticks after glue was added.

I am currently a student at the University of Wisconsin - Platteville pursing a Bachelor's degree in Civil Engineering. This project took a lot of time and effort, but I was very happy with the end result. Feel free to follow the guide below and make your own!

Supplies

Needed supplies are as listed:

1. PLA filament
2. 3D Printer
3. Popsicle Sticks
4. Glue (super glue, construction glue, and/or hot glue)
5. Toothpicks
6. Scissors
7. Ruler

Step 1: Design

Popsicle sticks were measured using calipers to determine the width the guides needed to be. A small squared test U was printed with this width to make sure the dimensions allowed a popsicle stick to fit with some room. Truss member angles and the width dimension were then used to create guides for every connection. The joint guides were made specifically to be able to work with any of the joint connections regardless of if there was a vertical or diagonal missing. The side supports also had to be designed to hold at least five stacked popsicle sticks and have cut outs so that the glue would be less likely to stick to the them. All design work was done in Fusion 360.

The needed .stl files for this project are as follows:

Step 2: 3D Printing

After downloading the above stl files, they will need to be sliced so that the 3D printer is able to print the model. Ultimaker Cura was used in this project but any slicing software will do. Guides were sliced with the following properties but can be adjusted as needed:

• 0.6 mm Nozzle
• 0.2 mm Layer Height
• 2 Walls
• 45% Grid Infill
• 220 °C Nozzle Temperature
• 50 °C Build Plate Temperature
• 40 mm/s

To have a guide for every connection, you will need to print:

• 2 Bottom Corner Guides
• Note: You need to flip the model in Cura for one of them
• 2 Top Corner Guides
• Note: You need to flip the model in Cura for one of them
• 10 Joint Guides

Step 3: Construction

1. Start by building the top and bottom chord members (8 Total)
2. The guides will help determine the lengths using a ruler
3. Cut and glue popsicle sticks on top of each other to the necessary lengths
4. It is recommended to use heavy duty scissors to cut the sticks and use toothpicks to help evenly spread the glue.
5. Make members as one continuous piece that is between two to five popsicle sticks thick
6. Build the webs (10 Verticals & 12 Diagonals Total)
7. Measure length between the top and bottom chords
8. Use the same method as described above
9. It is recommended to give all the glued pieces time to dry before building the trusses
10. Insert the top and bottom chords into the 3D printed corner guides and glue together
11. It is recommended to use super glue or another fast setting glue as these pieces need to hold the webs in place
12. After the glue in the corners set, glue webs in between the top and bottom chords using the joint guides to help determine the correct positions.
13. Carefully slide guide off all connections and glue popsicle stick gusset plates to sides of truss
14. These help hold the webs in place
15. This can either be done by cutting pieces to the correct size or pre-making plates and gluing them on
16. If you plan to test your bridge, large plates will help your truss hold more load
17. Repeat steps 1-6 to make another truss
18. Once both trusses are made, add lateral bracing between trusses to make the bridge the chosen width
19. Add diagonal bracing for more stability if desired
20. If you plan to test your bridge it is highly recommended to make the bracing two to three popsicles thick as well as having both lateral and diagonal bracing. This is because these bridges like to buckle under load.
21. After the trusses are built and connected with bracing, you have a completed popsicle stick bridge.

Step 4: End Result

For this project, a 32" long x 5" wide x 8" tall bridge was constructed. All members were four popsicle sticks thick and gusset plates were one popsicle stick thick. These dimensions can be copied exactly or scaled down/up using the 3D printed connection guides. Have fun building your own!

Comments

[charlessenf-gm]

Would have appreciated more images of the construction steps. For instance, are those lengthwise members first assembled as a laminated piece or built in segments that, end to end equal the 32-inch length?
Or are you presenting an instruction on the building of the guide pieces?

[Joshua Peplinski]

I apologize for not being super clear. I briefly address your question in steps 1 and 2 of the construction stage of my post. All the members were made as continuous, laminated pieces, and you can sort of see these overlapping, glued sticks in the overhead picture at the beginning of this stage. In total for both of the trusses, 2 bottom chords, 6 top chords, 10 verticals, and 12 verticals (all of which are separate, laminated pieces) were made first. Then once all the pieces were made, they were fitted into the guides to help glue those pieces together into the trusses. I hope this helps answer your question and clarify any confusion.

[charlessenf-gm]

No need to apologize. Thanks for the response.
Have you read The Great Bridge: The Epic Story of the Building of the Brooklyn Bridge by David McCullough? Also up your street his "The Path Between the Seas: The Creation of the Panama Canal, 1870-1914The Path Between the Seas: The Creation of the Panama Canal, 1870-1914" in which Teddy "recognized Panama" and, then dealth with their newly formed government!

[mwm407408]

I like it.You should see the bridges along the Ohio river very similar work.Excellent job.

[Joshua Peplinski]

Thanks. I'll definitely have to do some research on these and take a look.

[mwm407408]

Train trussel bridges are still being used today.Good luck in your career.

[obillo]

Thats very much for this, Joshua. I have long been an admirer of the severe Euclidian beauty of truss bridges, not to mention their efficiency is use of material (unlike for example the Town Lattice truss so popular in kitschy covered bridges. BUT--please do a PRATT truss next time. Pratts are the greatest!

[Joshua Peplinski]

It was definitely a rewarding feeling getting to look at the finished project. If I ever build another popsicle stick bridge, I'll look into some other designs.

[schreib]

Since this was a school project what was your Design Load?
I can't imagine a guy after building something like this not destructive testing it! What did it FAIL at?! Ha!
Did you test it to fail with a load INSIDE or on top? It doesn't look like you have much of a road bed support on either side.

[Joshua Peplinski]

Our bridges were supposed to be able to hold 350 lbs and fail before 400 lbs while also not deflecting more than 3/4". They had to span 32" and could not be more than 10" tall. Unfortunately, during testing many of the groups' bridges failed due to lateral torsional buckling (twisting) instead of the truss failing as designed. They were testing using an automatic machine that pulled down on rods that laid across the bridges where ever the group chose (hence why the road bed is not designed to be strong). My group ended with a total of around 125 lbs due to one of the angled webs being pulled out of the joint. Our bridge was loaded with two rods sitting on top of the two "V" joints towards the middle of the bridge. Although the testing portion was kind of a let down, the project was a lot of fun and a good learning experience.

[schreib]

Interesting. Did any bridge pass the 350# design? What did the top builders hit for their proof load and what elements made their designs provide superior strength?
I built a shed with my trusses "home-built". Instead of building special "forms" as you did with the 3D printer I laid out a large plywood table as a base and placed blocks held down by construction screws as needed to hold structural elements in place while fastening to make 4 identical trusses. I was surprised that this bridge design assigned by a prof. seemed to devolve into an exercise in 3D printing. Care to comment on that?
thanks.

[Joshua Peplinski]

No one was able to meet their design loads mainly due to buckling like I mentioned, and I think the highest load was 150 lb. I remember one group had a theoretical load of 1000 lb that they used a factor of safety on to bring it down to the 400 lb requirement. I have a friend who has multiple 3D printers, so it's been a hobby I've been getting better at in my free time. When we found out about the project, I just thought it would be a lot easier constructing the trusses with guides instead of having to measure out all the web angles and getting them to fit nicely with each other. The guides ended up doing their job well and the only measurements that had to be made were the overall length and height. That doesn't sound like a bad idea for making some trusses for a small shed. Somewhat of an upscaled application of my project in a way. Interesting.

[TwoWindsBear]

Looks like a Bailey Bridge.

[Joshua Peplinski]

The bridge wasn't built to resemble any designs in particular, but I can definitely see the similarities with a Bailey bridge.

[sawdustagain]

Love it, these are miniature 3D printed Simpson Strong-Tie brackets. Fun project !

[Joshua Peplinski]

Thank you! It would be interesting to design 3D printed structural brackets versus using them only as guides.

[maker_soup]

Cool build!

[Joshua Peplinski]

Thanks!

[Aryd'ellH]

This would be fabulous in an HO scale model railroad layout...wishing I had access to the printer.

[ironarmadillo]

You probably don't need a 3D printer.

It sounds like you're an HO modeler so you probably have some scratch building skills. You can download the 3D print files, rescale them to the HO dimensions you need, print the revised images off on a regular printer in full HO scale, cut out the HO scale templates, glue them down to a flat surface and then glue vertical pieces of wood where the alignment fingers are on the template.

I've done this several times myself in my own railroad model building where I need to make repeatable spaced glue-ups - particularly with scratch building late 1800's truss rod framed freight cars.