Hello everyone! We (Graciela and I) made a couple of carnival rides for our midterm project. Here’s how we did it, starting from the bottom, working our way to the top, and going back to the bottom to finish, just like a Ferris wheel.
The Bottom of the Wheel (Gate 1)
We first decided to start with the idea of making a swing ride that is commonly found in carnivals and fairs. The main pole of the swing will move up and down using a camshaft mechanism while it is spinning, and it has a cart that swings out due to inertia as the pole spins. We later expanded that idea to include a planetary gear that has more carts that rotate outside of the ride. When we sat down to figure out how we would include the many mechanical movements that would go into this great ride, we came up with these conceptual designs.
Figure 1: The first drawn concept of the ride design.
Figure 2: The second drawn concept of the ride design, with included intended arrows of movement.
Here’s how our design would work: A crank handle would turn two layers of gears. On the bottom layer, the gear attached to the crank would rotate two right-angle gears, one of which (the vertical one) connects to a heart-shaped cam (Mechanism #96, housed in an open press-fit box) that pushes the pole that has the swing carts up and down. On the top layer, the crank gear would rotate a stack of gears and a gear that is attached to the main pole. We thought that the stack of gears would keep the main pole spinning as it moves up and down since the main pole has a gear that provides its rotational motion. At the same time, the outer gears (the one on the crank shaft and the one on the main pole) would rotate an outer planetary gear (Mechanisms #34, #55) with the outer carts that is bound within a circular frame.
We knew for sure that the mechanism would be complicated, but we were confident that it will work.
25% OF THE JOURNEY (Gate 2)
Now that we’ve sat in the Ferris wheel for a while, we’ve started building our low-fidelity prototypes out of cardboard. We began with cardboard structures, cardboard gears, and wooden dowels, but quickly realized that if we were to test our gear functionality, especially our right-angle gears, we would have to make our gears and our heart-shaped cam out of laser-cut wood. So we did, knowing that we would have to use our own wood later for future prototypes. We also had to use the hand saws and the band saw extensively to cut our dowels to the right size.
We used Gear Generator to make our gears, which we laser cut from scrap sheets of cardboard and 1/4-inch plywood from previous projects. It took us a good while to ensure that the gears are properly aligned, especially with the outer planetary gear, and that the gears turn smoothly.
Note that we also used dowels that are glued on the planetary gears to represent the carts that will be rotating on the planetary gear.
Figure 3: An incomplete preliminary prototype of our ride design, mostly made of cardboard.
Figure 4: A first iteration of the stacked gears.
Figure 5: An iteration of our low-fidelity prototype using wooden gears, wooden dowels, and cardboard components.
Figure 6: Progress on the prototype, with the right-angle gears attached.
We also laser cut the heart-shaped cam out of 1/4-inch scrap plywood to test its integration in the ride design.
Figure 7: the wooden heart-shaped cam.
However, when we put the main shaft on the cam, we noticed two problems. First, the main shaft tends to lean when it is moved up, causing it to fall over when it happens. This problem required Adam to develop a cardboard cross-shaped component that kept the main shaft and the central shaft straight and aligned properly as they both rotated. The second problem is that the main shaft gets stuck sometimes as the cam rotates. We solved this problem by smoothing the main shaft’s bottom edge, which gives a ramped platform that can more easily slide on the cam than before.
After these considerations, we’ve made a top frame that holds string threads that go through each of the four swing carts. We then put the whole prototype together, making sure to attach the top frame with the string to the top of the main shaft and to include a crank made of cardboard. We also had to make holes in the bottom base to ensure that the rotating shafts are secured. After all these steps, we finished our low-fidelity prototype and can now continue riding the Ferris wheel.
Figure 8: Our final low-fidelity prototype.
AT THE TOP (Gate 3)
At this point, we were at the top of the Ferris wheel, with the design ready to go. We laser cut everything out of wood, taking into account the feedback that we got from our professors and mentors. Graciela managed to fit everything we needed to cut onto a 24-inch by 24-inch template, though we did have to use a couple of sheets of wood to cut out every piece.
Figure 9: the Illustrator file layout of all the pieces we needed to laser cut for our medium-fidelity prototype, excluding the extra washers and spacers.
We also used ball bearings for each rotating shaft to reduce the friction the shafts experience from rotating. To keep the shafts in place, we designed small wooden washers and spacers that prevent the shafts from moving translationally.
Figure 10: Building the medium-fidelity prototype with ball bearings.
We also cut a heart-shaped cam from aluminum using the Proto waterjet cutter. After cutting, Graciela sand-blasted the cam to post-process it. We then attached it to a laser-cut wooden box that was the same dimensions as the cardboard prototype before putting on a ball bearing and gluing it to the base using superglue.
Figure 11: the heart-shaped cam as it appears on the ProtoMAX software.
Figure 12: the cam after cutting on the waterjet cutter.
Figure 13: an image of our prototype featuring the heart-shaped metal cam.
After assembling everything together using string, superglue, and a bit of elbow grease, our medium-fidelity prototype is complete!
Figure 14: Our medium-fidelity prototype.
However, we noticed a few issues with our prototype. The first is that because the dowels we used were slightly bent, the top base of our prototype ended up being unstable and not level, which misaligned the gears on both the top and bottom layers, making them extremely hard to turn, even with the crank that we developed. Similarly, we often had to move some of the superglued parts because the rotating shafts would still be slightly bent even when we determined the best places to put the washers for each of the shafts, meaning that we had to adjust to keep them stable, resulting in a lot of glued wood left over on the base as we moved each washer. We would also have to constantly redesign the cross-shaped piece that kept the main shaft and the central shaft straight, resulting in a lot of wasted wood.
These problems would be addressed in the final stage of our Ferris wheel journey.
APPROACHING THE FINISH (Final Prototype)
Based on our mentors’ feedback and our realization, we decided to modify the main chassis of the ride design. Instead of circular layers supported by dowels, we went with a hexagonal box that will enclose the bottom layer functions; that is, the box will close off the right-angle gears and the attached heart-shaped cam mechanism. We felt that this method would be more stable than circular bases supported by bent dowels.
Figure 15: An incomplete top of our final prototype, with the new crank attached.
For additional iterations, we increased the hole sizes on the cross-shaped stability pieces, made an entirely new crank, and slightly decreased the size of the gears (excluding the right-angle gears, we took a while to work the sizes out) so that they have a looser fit between each other, especially with the planetary gears. We also decreased the size of the heart-shaped cam and the box that it goes into so that we would have less wood to cut for the main chassis box.
Figure 16: Progress on the new chassis, with some of the mechanisms intact.
Figure 17: The new cam in its new box.
To finish the wooden components, Graciela did an amazing painting job on the chassis and main components (seen in some of the images below), adding a white spiral design with colorful dots to the main shaft and a pond design with small fish to the space inside the planetary gear. Adam spray-painted the carts on the swings and the carts on the planetary gear with different colors (6 of them to be exact) to give the feel of different carts on each ride. Here are some images of the spray painting process:
And with that, after designing, cutting, and pasting our name plate, the ride design is complete!
Figure 18: The final prototype, on a clean workspace…without the spiral design.
Here’s a video of the ride design in action, with a notable white + colored spiral on the main pole done by Graciela:
We hope that the ride is enjoyable for all who step on board!
Stepping Off the Ride (Cost Analysis)
Materials:
- 4 sheets of 24-inch x 18-inch 1/4-inch-thick plywood (source: here) = $48.99
- 6 cans of spray paint (source: here for each spray paint can): 6 x $6.99 = $41.94
- Acrylic paint set (source: here) = $9.99
- 3 608 RS ball bearings (source: here): 3 x $0.45 = $1.35
- White string (source: here) = $4.99
- Maybe a foot of black glossy vinyl from a roll (source: here) = $0.62
Tools:
- Renting a laser cutter (source: various blog posts on the internet): $35/hour x 3 hours = $105
Labor:
- Considering that we spent 70 hours on this project and that $7.25 is the minimum wage in Texas: 70 hours x $7.25 = $507.50
Total Cost: $720.38
Adam’s note: I guess this ride needed some tender love and care put into it, after all…
