Expanding Marginal Efficiency in Mechanical Power Transmission
Type of Submission
Poster
Keywords
Transmission, power transfer, gearing, power band, marginal efficiency
Abstract
The proposed transmission design is addressed to increase shifting efficiency and power band optimization. These issues are of crucial importance to applications where absolute performance or efficiency is desired, like car or bike racing, PTO for large generators, but the practicality and ease of implementation of the design lend its benefits even to less rigorous applications. To date, continuous transmissions have relied on friction to do their work, which adversely either limits the output gearing ratio or the output torque. The proposed design is not hampered by such issues. In 1898, James Moncrief Cleland outlined the use of an expanding sprocket for bicycles, but it stepped between two speeds only, and the mechanism was unwieldy. Modern designs have suggested the use of one way bearings and tangential contact transmissions, but these continue to offer significant friction losses, and no mechanical float to match the gearing to a set input torque. The impetus for my design flowed from frustration in managing gear ratios in my car and on my bike. Furthermore, I understand that a torque converter might usefully increase the power band of an engine, provided the mechanical efficiency of the transmission did not offset the gains in efficiency on the fringes of the power band. For this reason, I am proposing an expanding sprocket with infinite variability which manages its own ratio in order to match the load to the source. The design is such that the ratio may be changed down and back up in even as the same link in the chain passes over one half of a turn about the sprocket. Between the seamless shifting and expanded power band, I anticipate modest efficiency gains. However, even a few percentage points of improvement in mechanical efficiency translates into massive power gains over time in a large scale power-generation system, or it could be that little bit extra a biker needs to shave half a second off his time to win a race.
Faculty Sponsor or Advisor’s Name
Timothy Norman
Campus Venue
Stevens Student Center
Location
Cedarville, OH
Start Date
4-1-2015 11:00 AM
End Date
4-1-2015 2:00 PM
Creative Commons License
This work is licensed under a Creative Commons Attribution-Noncommercial-No Derivative Works 4.0 License.
Expanding Marginal Efficiency in Mechanical Power Transmission
Cedarville, OH
The proposed transmission design is addressed to increase shifting efficiency and power band optimization. These issues are of crucial importance to applications where absolute performance or efficiency is desired, like car or bike racing, PTO for large generators, but the practicality and ease of implementation of the design lend its benefits even to less rigorous applications. To date, continuous transmissions have relied on friction to do their work, which adversely either limits the output gearing ratio or the output torque. The proposed design is not hampered by such issues. In 1898, James Moncrief Cleland outlined the use of an expanding sprocket for bicycles, but it stepped between two speeds only, and the mechanism was unwieldy. Modern designs have suggested the use of one way bearings and tangential contact transmissions, but these continue to offer significant friction losses, and no mechanical float to match the gearing to a set input torque. The impetus for my design flowed from frustration in managing gear ratios in my car and on my bike. Furthermore, I understand that a torque converter might usefully increase the power band of an engine, provided the mechanical efficiency of the transmission did not offset the gains in efficiency on the fringes of the power band. For this reason, I am proposing an expanding sprocket with infinite variability which manages its own ratio in order to match the load to the source. The design is such that the ratio may be changed down and back up in even as the same link in the chain passes over one half of a turn about the sprocket. Between the seamless shifting and expanded power band, I anticipate modest efficiency gains. However, even a few percentage points of improvement in mechanical efficiency translates into massive power gains over time in a large scale power-generation system, or it could be that little bit extra a biker needs to shave half a second off his time to win a race.
