Scooter Design Project
Introduction Overview of Project:
The objective of this project is to properly design, fabricate, and test a kick scooter entirely made from PVC pipe and fittings(excluding the wheel assembly/connection). The main requirements we included in the design were weight ( < 12 pounds), size (36'' x 24'' x 24''), dynamic loading (10" jump impact), deflection (non-visible under static loading), professional quality, and braking capability.
The project began as a multiple week design phase that involved brainstorming different designs. Throughout brainstorming, we preformed multiple hand calculations as well as Finite Element Analysis in order to account for static and dynamic/impact loading. Through our calculations, we narrowed down the ideal designs and narrow the components to their final iterations. We then moved to the manufacturing stage, where we got to experience hands on creation and fabrication. The prototype scooter was then put to the test and ridden in order to determine areas of improvement with the customers requirements( "our requirements") in mind. Finally the improved and final scooter design was put to the test through an obstacle course, 10 inch jump, and an evaluation by our peers.
Design Details:
In the picture, you can see the designed scooter assembly. It was designed in this manner to sustain the calculated loads. The design has many features, of which include: the water bottle holder, a sleek two color design, functional spring loaded brake, adjustable handlebar, grip tape, and a collapsible deck design.
The second picture shows the final designed water bottle holder, of which we choose to ride with out in front of the handlebars (as opposed to facing the other way in the picture). The water bottle holder allows the rider to stay hydrated and gives the rider a place to store their drink while they are utilizing the scooter for transportation. This picture also shows the adjustable handlebars. The handlebars were made to adjust in height for variance in rider height and comfort.
In the third picture, the spring loaded brake is shown up close. The brake is put together by a bolt that runs through a spring and the deck, straight down with a rubber stopper on the end that hits the brake and stops the scooter.
The grip tape, two color design as well as the collapsible state can be seen if the third picture as well.
The deck connection is seen in the fourth picture. The deck is designed to have a screw at the front of the deck running horizontally that connects the fork to it with a second pin about the same size as the bolt running horizontally behind the bolt. When the pin is removed, the scooter will collapse into a smaller more store-able state.
When designing our scooter, most, if not everything, was based off of our chosen deck design. When doing our analysis for the deflection of the deck, we found that many decks would work but that the one we had chosen gave us extra support in preventing any deflection from occurring. We also found that the deck we chose was a little bit simpler to piece together through a couple bolts. The cross sectional properties of our deck allowed us to prevent deflection while easily fabricating the deck.
From our deck design, we then we able to agree on a standard PVC pipe column as the fork with a T connection attached at the top for the handles. The handlebars were a straightforward design and it wasn't until later prototyping testing that we decided to add some adjustable features into the scooter in order for the rider to feel more comfortable.
The final part of the scooter design was the connection between the steering column and our deck. We ran into a few problems here but were able to design a connection that was able to hold up. Our first design was multiple elbows coming off the sides of the deck and attaching to a cross that the handlebar column rotated through. Unfortunately, the design became a problem when we realized that the elbows and deck width caused the scooter to be a lot wider then we had planned at the connection. With the materials we had, we then switched the connection design to two thick PVC sheets on either side of the deck with screws going through it and the sides of the cross that rotated around the steering column. Unfortunately, after prototype testing, the connection failed when making improvements. From the way the connection split (picture shown above) it showed evidence of shearing, which we believe it could withstand, but split due to fatigue. After observing this failure, we were able to realize that the handlebars were creating a moment in the connection that we could try and correct by adding in a wire connection near the bottom of the handlebar column. Our final design resulted in us making the PVC connector sheets bigger as well as adding in the wire and thin metal brackets to help with stability.
Analysis:
For all FEA results, hand calculations were first utilized in order to verify the simulation results. I have included the hand calculations pictured above in order for some to generally grasp what our assumptions and how we did our calculations. I have also included the isometric views of the SolidWorks model assembly of the scooter. If you want further details on hand calculations, FEA results, or assumptions made for those, let me know!
We considered a variety of different deck designs, but we ultimately decided on a deck that had the highest factor of safety and was easiest to manufacture. You can see the top three different decks that we hand considered along with all of their calculations.
Conclusion and Technical Challenges Faced:
At the scoot-off performance, our scooter successfully maneuvered across the obstacle course. Our deflection measurement test also indicated less than a 1/4" deflection under static loading of 175 pounds. During the course, the scooter spring loaded brake and steering assembly performed extremely well when taken to the test at sharp corners. In the end, we even took our scooter on the jump and it survived without damage.
Reflecting on the project, this project taught me many things. The scooter analysis allowed me to apply the formulas and concepts that I had been learning in classes for a while now and translate it into a real designed prototype. The manufacturing process allowed me to grow a lot as an Engineer. Being a Biomedical Engineer, we mostly take classes that do not pertain to us being able to utilize the machine shops we have, as a result, I was able to learn and apply my machine skills. The design process also taught me a lot about going from a design to the manufacturing stage. We may be able to conceptualize a great design but must keep in mind the feasibility aspect when it comes to manufacturing the product. The project also taught me a lot about teamwork. When the project came down to it, we had many days were only two out of the three group members were working and unfortunately when things went wrong others were there to criticize rather then coming up with a fixable design.
For us as a group our most challenging part was our connection. When our originally design was deemed as to big, we were forced to go back to the drawing board with the connection. As we were able to figure out a more feasible part, we were then faced with the challenge of that breaking and we were forced to come up with a better design two days before final prototyping was due. On the final day of testing, seeing that final design work really was rewarding. As much trouble and stress as the final days brought, I really believe that this project allowed me to become a better engineer. I was able to gain experience in the whole design process, from designing, manufacturing, testing, designing, manufacturing, and lastly design validation.
The objective of this project is to properly design, fabricate, and test a kick scooter entirely made from PVC pipe and fittings(excluding the wheel assembly/connection). The main requirements we included in the design were weight ( < 12 pounds), size (36'' x 24'' x 24''), dynamic loading (10" jump impact), deflection (non-visible under static loading), professional quality, and braking capability.
The project began as a multiple week design phase that involved brainstorming different designs. Throughout brainstorming, we preformed multiple hand calculations as well as Finite Element Analysis in order to account for static and dynamic/impact loading. Through our calculations, we narrowed down the ideal designs and narrow the components to their final iterations. We then moved to the manufacturing stage, where we got to experience hands on creation and fabrication. The prototype scooter was then put to the test and ridden in order to determine areas of improvement with the customers requirements( "our requirements") in mind. Finally the improved and final scooter design was put to the test through an obstacle course, 10 inch jump, and an evaluation by our peers.
Design Details:
In the picture, you can see the designed scooter assembly. It was designed in this manner to sustain the calculated loads. The design has many features, of which include: the water bottle holder, a sleek two color design, functional spring loaded brake, adjustable handlebar, grip tape, and a collapsible deck design.
The second picture shows the final designed water bottle holder, of which we choose to ride with out in front of the handlebars (as opposed to facing the other way in the picture). The water bottle holder allows the rider to stay hydrated and gives the rider a place to store their drink while they are utilizing the scooter for transportation. This picture also shows the adjustable handlebars. The handlebars were made to adjust in height for variance in rider height and comfort.
In the third picture, the spring loaded brake is shown up close. The brake is put together by a bolt that runs through a spring and the deck, straight down with a rubber stopper on the end that hits the brake and stops the scooter.
The grip tape, two color design as well as the collapsible state can be seen if the third picture as well.
The deck connection is seen in the fourth picture. The deck is designed to have a screw at the front of the deck running horizontally that connects the fork to it with a second pin about the same size as the bolt running horizontally behind the bolt. When the pin is removed, the scooter will collapse into a smaller more store-able state.
When designing our scooter, most, if not everything, was based off of our chosen deck design. When doing our analysis for the deflection of the deck, we found that many decks would work but that the one we had chosen gave us extra support in preventing any deflection from occurring. We also found that the deck we chose was a little bit simpler to piece together through a couple bolts. The cross sectional properties of our deck allowed us to prevent deflection while easily fabricating the deck.
From our deck design, we then we able to agree on a standard PVC pipe column as the fork with a T connection attached at the top for the handles. The handlebars were a straightforward design and it wasn't until later prototyping testing that we decided to add some adjustable features into the scooter in order for the rider to feel more comfortable.
The final part of the scooter design was the connection between the steering column and our deck. We ran into a few problems here but were able to design a connection that was able to hold up. Our first design was multiple elbows coming off the sides of the deck and attaching to a cross that the handlebar column rotated through. Unfortunately, the design became a problem when we realized that the elbows and deck width caused the scooter to be a lot wider then we had planned at the connection. With the materials we had, we then switched the connection design to two thick PVC sheets on either side of the deck with screws going through it and the sides of the cross that rotated around the steering column. Unfortunately, after prototype testing, the connection failed when making improvements. From the way the connection split (picture shown above) it showed evidence of shearing, which we believe it could withstand, but split due to fatigue. After observing this failure, we were able to realize that the handlebars were creating a moment in the connection that we could try and correct by adding in a wire connection near the bottom of the handlebar column. Our final design resulted in us making the PVC connector sheets bigger as well as adding in the wire and thin metal brackets to help with stability.
Analysis:
For all FEA results, hand calculations were first utilized in order to verify the simulation results. I have included the hand calculations pictured above in order for some to generally grasp what our assumptions and how we did our calculations. I have also included the isometric views of the SolidWorks model assembly of the scooter. If you want further details on hand calculations, FEA results, or assumptions made for those, let me know!
We considered a variety of different deck designs, but we ultimately decided on a deck that had the highest factor of safety and was easiest to manufacture. You can see the top three different decks that we hand considered along with all of their calculations.
Conclusion and Technical Challenges Faced:
At the scoot-off performance, our scooter successfully maneuvered across the obstacle course. Our deflection measurement test also indicated less than a 1/4" deflection under static loading of 175 pounds. During the course, the scooter spring loaded brake and steering assembly performed extremely well when taken to the test at sharp corners. In the end, we even took our scooter on the jump and it survived without damage.
Reflecting on the project, this project taught me many things. The scooter analysis allowed me to apply the formulas and concepts that I had been learning in classes for a while now and translate it into a real designed prototype. The manufacturing process allowed me to grow a lot as an Engineer. Being a Biomedical Engineer, we mostly take classes that do not pertain to us being able to utilize the machine shops we have, as a result, I was able to learn and apply my machine skills. The design process also taught me a lot about going from a design to the manufacturing stage. We may be able to conceptualize a great design but must keep in mind the feasibility aspect when it comes to manufacturing the product. The project also taught me a lot about teamwork. When the project came down to it, we had many days were only two out of the three group members were working and unfortunately when things went wrong others were there to criticize rather then coming up with a fixable design.
For us as a group our most challenging part was our connection. When our originally design was deemed as to big, we were forced to go back to the drawing board with the connection. As we were able to figure out a more feasible part, we were then faced with the challenge of that breaking and we were forced to come up with a better design two days before final prototyping was due. On the final day of testing, seeing that final design work really was rewarding. As much trouble and stress as the final days brought, I really believe that this project allowed me to become a better engineer. I was able to gain experience in the whole design process, from designing, manufacturing, testing, designing, manufacturing, and lastly design validation.
2 Teammates
