Drill Powered Bike
Date: January 2022 - April 2022
Drill Powered Bike
Date: January 2022 - April 2022
The Drill Powered Vehicle component design project applies the theory and application of mechanical components. Our team, 4 Wheel Drive, was tasked with the challenge of competing our drill powered vehicle in the endurance challenge, a 30 minute race in Kittredge at the University of Colorado, Boulder. Throughout the project, our team, 4 Wheel Drive, got the opportunity to apply what we have learned in our mechanical engineering degree and to create a bike that is motored solely by a cordless drill. In this project, our vehicle was manufactured with custom parts, following a budget and time, and working as a team with specified engineering roles. We followed design requirements that included: actuation, driving, weight, budget, frame, bike frames, manufacturing, and were aesthetically pleasing. By these requirements we created our dill powered vehicle that resembles a bike.
Weight: Vehicle must be below 50 lbs
Budget: The cost of the vehicle at the run-off must be less than $200
Manufacturing: Your team must manufacture at least 1 component which requires custom machining using a mill, lathe, and/or welding. This component cannot be readily purchased as an off-the-shelf part.
Actuation: Power only provided by supplied drill, only one battery per attempt
Driving: Driver must complete course while riding on vehicle
Frame/Bike Frame: Frames should be partly produced/customized by each team. Each team may reuse half of a commercial bike frame, as defined in the lab writeup.
Aesthetics: Your design must have an aesthetic theme
The most important specifications were weight requirements, power requirements and the ability to complete the endurance challenge course. The power to weight ratio was very important to consider because if it were too low, the vehicle would not be able to complete the course. Drill power was calculated using torque and RPM measurements based on the drill we were allowed to use. We measured the weight of the vehicle using the scale in the machine shop. This allowed us to calculate the power to weight ratio. As we assembled the vehicle, we also tested critical components and found out if they meet the criteria to be able to race. Most importantly, the vehicle would have to be tested on the 1100 ft. race course to see if it would function as designed and meet time requirements.
Test: We weighed the completed vehicle in the idea forge. We will also measure the exact torque and RPM of the drill we will use. Then we will calculate if the ratio is acceptable to meet the challenges of the endurance course
Goal: Adequate power to weight ratio
Criteria: Vehicle exceeds ratio needed for course = pass; Vehicle does not exceed ratio = fail
Result: Pass. Our vehicle weighed in at 35.6 pounds. This meets our weight to power requirement and passes the test.
The frame was an involved process to manufacture. First, each one of the specific tubes had to be cut to length on the roll-in bandsaw. Then, each one of the tubes that needed an angle had the angle cut on that same roll-in bandsaw. One of the angles was steep enough that a parallel had to be manufactured in order to space the tube off the bench. After each angle was cut, some of the tubes that had to interface with other parts had to be machined to final dimensions. Mostly, these were ¼-20 holes for mounting the drill plate, but the footrest and rear horizontal tubes needed operations too for the footrest hole and wheel mount slots, respectively.
After sizing, the next major operation was welding. Two halves of the bike were manufactured separately: the cage structure around the back wheel and the center Y-shape. Each was fixtured in place with magnets and/or clamps, then tack welded in place. After tack welding, the whole bike was finished welded in one go. Many of the welds were excessively overbuilt, so afterwards some were ground flat with a handheld angle grinder. See Appendix B for manufacturing drawings.
The drill plate is a key component to our design as it connects the drill and drive train to the frame, which essentially makes it the foundation of our transmission. The plate must resist the torque from the drill and fasten it to the frame such that there will be no turbulence between the drivetrain and the drive wheel. The plate holds the drill, pillow blocks, and throttle stationary on the frame. The plate was made from 6061 Aluminum and was cut into a 12” x 10.5” x 3/16” plate. There will be six slots for the hose clamps to hold the drill down, six holes for the spacers to level the drill, four holes for the pillow blocks, seven holes for the frame, and one slot for the sprocket and chain to go through.
The drive train is one of our most critical components as it is how we are able to actually move the vehicle. It consists of many parts including sprockets, pillow blocks, bearings, and a bike chain. To apply torque, the drill spins the shaft, which is connected to the back wheel via a sprocket and chain that maintains a 4:1 gear ratio. The main constraints that affected the drive train were cost and the size of the shaft. The shaft had to be 0.5 inches in diameter, which greatly narrowed down the choices for bearings.
The throttle was assembled with a combination of purchased and recycled parts. One of the purchased parts were two steel, 90 degree brackets purchased from Home Depot. One bracket would act as the trigger actuator while the other acted as a fixed support for the throttle cable to be fed through. The fixed support was bolted in place on the side of the drill opposite of the trigger. The trigger actuator was not bolted to the drill plate but instead fastened to a spring-loaded hinge purchased from McMaster Carr. The spring-loaded hinge acted as a throttle return and was fastened to the drill plate just underneath of the trigger. We used the rear brake lever present on our donor bike to act as the throttle lever. A cable ran from the lever all the way back the bike, through the fixed support, to the trigger actuator where it was locked in place. Rubber hosing to hold and protect the cable was found in the used parts bin of the DIDL. The end of the cable was fixed to the throttle actuator using a bolt and a lock nut which sandwiched the cable tightly against the bracket. The end result was a system which allowed the driver to control the speed of the drill without taking their hands off of the handlebars.
We learned many lessons during this project and would make many changes in the next iteration. The most important lesson would be to create a design that we know has plenty of tolerance for when we actually manufacture and assemble everything. We found that our design had many instances where assembled parts didn’t fit quite as planned in the CAD design. We could have also done more second checking on one another’s work to make sure they didn’t miss anything while designing. Another factor was that our team had little to no experience with building bikes, which showed when we designed to have the drive shaft on the left side of the bike. We also were crunched for time when it came to testing the fully assembled bike, which affected our performance at runoff. This was not because of doing things last minute, but more so because of how many major issues we encountered with assembly. Some days we spent 9 hours trying to fix one or two issues with the bike. With the knowledge we have now about bikes and experience in the design process, I know that we would build a much better bike and we would encounter a lot less setbacks.
Mechanical Engineering
Test Engineer
Mechanical Engineering
CAD Engineer
Mechanical Engineering
Mechanical Engineering
Mechanical Engineering
Project Manager
Mechanical Engineering