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Motivation
Although not often seen exceeding 5 Mph, the average lawn tractor packs all of the essentials for going fast. This Murray model for instance came equipped with a 12 HP engine, 4 speed manual transaxle, and 4 wheels to roll on. Working in collaboration with fellow engineer Jason Donatella, this tractor was pushed to its limits through incremental modification and improvement creating a racing machine unlike any other.
Pulley Swap
The pulleys on the engine output shaft and transaxle input shaft were replaced to maximize the drive ratio for speed. To accomadate the new pulley configuration, an array of idler pulleys were welded to the frame. These idler pulleys kept the clutch belt from going slack during dissengagement and prevented the belt from rubbing against seperate components.
Muffler
To address the excessive noise of the engine, a muffler was constructed from scrap metal using a baffled design. Passing exhaust gasses through a series of restrictions and metal shavings significantly dampened its volume over the stock exhaust. (And shoots Flames)
Intake
An air intake was modeled to improve airflow to the engine. The intake used an off the shelf cone air filter and was 3D printed using PETG filament.
Drive Coupling
During initial testing, both differential spider gears fractured leading to a loss of power. To address this issue, a drive coupling adapter was devised to link the independent rear axels together and deliver power through the main ring gear. The coupling was made up of a stack of steel plates laser cut to a specific profile and then bolted together to increase their width. The plates were then welded to the drive axels. This modification improved power delivery and drivetrain reliability at the cost of handling.
GPS documented 45 Mph top speed
Takeaways
This project, while low in budget, relied heavily on fundamental engineering skills in design and troubleshooting. In addition, hands on skills in machine tools, 3D printing, welding and rapid itteration were essential to completing project obectives.
Best In Show Winner: Motorcycle Category - Spring 2025 RIT Car Show (No actual motorcycles showed up due to weather)
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