Gates Belts Provide Pedal Power for Atlantic Ocean Crossing
Imagine pedaling 3,000 miles across the Atlantic Ocean in a paddleboat.
That’s exactly what two young engineers from the U.K. plan to do to raise £250,000 for charity. Mark Byass, age 23, is a design engineer and the boat designer and crewman. The second crewman and project manager is mechanical engineer Mike Sayer, age 26.
To acquire a boat that could withstand a 3,000 mile ocean crossing, they enlisted a team of experts in the fields of boat design, fiber usage, ergonomics and hydrodynamics to design a boat that was strong, fast, reasonably comfortable and safe. They also began lining up sponsors who could provide goods and services gratis so the entire £250,000 raised can go to the charities.
The boat is called Torpedalo. As the design began to take shape, focus turned to the drive system. Since every ounce of weight matters – to keep the boat light and maneuverable - their boss suggested a belt drive and recommended they contact Gates Corporation.
“Sponsorship deals often take months to put together,” Mike Sayer said, “but this one came together in two days. It was fantastic.”
Gates product application engineer, Dan Parsons, began working with Ivo Nikolov, the drive train engineer on the project. Ivo’s initial drawings called for a two-stage belt drive using a 20mm wide synchronous belt with an 8mm tooth pitch. They also included a 90° gearbox to transmit the rotational power of the pedaling motion to the propeller.
After reviewing Ivo’s design, Dan proposed eliminating the gearbox and using a 4:1 speed up on stage one, and a 1:1 ratio and 90° twist on stage two. He also recommended narrower belts for both stages—12mm wide PowerGrip® GT®2 synchronous belts. This lightened and simplified the whole system. The narrower belts are more than ample to meet the design power, and can accommodate the required 90° twist in the second stage; with a long center distance in this stage, strain on the belt is avoided.
Belt stretch was another of Ivo’s concerns. The PowerGrip GT2 belts do not stretch, but at least one component of the drive needs to be adjustable to accommodate belt installation and drive tensioning. Once belts are properly tensioned and run in, stretch is not an issue. Additionally, the belt drive weighs 20% less by eliminating the gearbox in the previous design.
Efficiency also matters. In a human-powered boat, loss of drive efficiency means wasted effort by the crewman working the pedals. Each stage of the synchronous belt drives is about 98% efficient, for a total estimated drive system efficiency of 96%. By contrast, the efficiency of the belt drive system with a 90° gearbox is estimated to be about 92 – 94%. A 2-4% loss of efficiency might not seem like much, but it is human power for 3,000 miles; every bit of energy saved matters considerably to the crewman.
Mark and Mike expect to begin sea trials with the Torpedalo early in 2011.
For the latest news on the Torpedalo project, visit www.torpedalo.com.
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