Luke Rasmussen and Dr. Mark Colton, Mechanical Engineering
People with hip disarticulation are those who have had a leg surgically removed above the hip, taking away every muscle and movement in one of their limbs. A surgery of this type makes it extremely difficult for its recipients to lead an active lifestyle. This project aimed to design a bicycle for use by people with hip disarticulation, thus enabling them to maintain an active and healthy lifestyle despite their obstacles.
By working closely with a student, named Chandler, who is suffering from hip disarticulation, it was decided that the project would focus on three specific features to improve bicycle technology for people with high-level leg amputations, such as hip disarticulation:
1. A method for locking the pedals in the horizontal position while standing. This provides better control while the bicycle is coasting. Chandler has indicated that this will be a critical improvement for those with hip disarticulation.
2. An improved seat upon which it is easier to sit for Chandler, and which provides more comfort.
3. Placement of the drive train on the left side of the bike or some form of guarding. All drive trains for bikes are on the right side, and because Chandler has only a left leg he tends to break parts vital to the function of the bike.
Dividing the project into three specific areas enabled the team to focus on one feature of the bicycle at a time. The results and current status of each improvement will be discussed.
Locking the pedals while riding a mountain bike is important to help avoid obstacles on the ground or scraping the ground while going uphill. Most riders are able to balance on both pedals and keep the pedals above their lowest point. However, a person with hip disarticulation must stand on the pedal while at its lowest point in order to coast. To overcome this problem, a braking concept was used on the pedal shaft. Using a hydraulic brake and a custom designed bracket shown in Figure 1, the rider can hold a brake to keep the pedals from moving. In order to pedal again the rider simply releases the brake.
The seat proved to be a more difficult area than anticipated. It is undesirable to strap the rider to the bike in case of a crash which made it difficult to balance a secure seat with the freedom to move about while riding. The end solution was design a hooked arm that would keep the rider from sliding off the side of the seat but still allow room to move and fall off during a crash.
It was decided that the best method for protecting the drive train from damage was to place a guarding around it. The guarding has not yet been completed but will likely consist of steel rods bent and welded around the drive train to protect it in the event of a crash or fall.
While these three improvements to a bicycle for those with hip disarticulation are significant, there is more work that can be done. Maintaining balance is difficult while riding a bicycle, largely due to the lopsided distribution of weight resulting from the missing limb. Designing a counterweight device could counteract this and enable a person with hip disarticulation to ride more comfortably. Another improvement that should be considered in future work is a method of pushing the used pedal up while riding. The biker will push down on the pedal to move forward but without being able to push the other pedal down the momentum can be lost, especially when riding up a hill. If the pedal were spring loaded and rose from the bottom to the top by itself the biker would be able to ride up hills more easily. Work will continue on this project with the goal of improving the quality of life and providing greater opportunities for fitness and recreation for those suffering from hip disarticulation.