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PhilA · 10-02-2010, 01:17 AM

This started out as a "Hey, that could be fun" project, built on a budget of approximately nothing, from junk and spare parts.

About as low-tech as you can get, never built with fuel economy (or road use!) in mind, but at a steady 15mph or so I decided to see what kind of economy it would pull- as accurately as I could measure it would do 110-120mpg, that dropping to about 20-30mpg flat out at about 25mph.

The engine was a 1955 model 75cc Suffolk Iron Foundry sidevalve engine. Static points-and-magneto ignition, Zenith updraught carburetor.
Compression ratio raised from 6.0:1 up to 11.5:1, internally polished, timing adjusted to peak at about 4500rpm. New rings. Long stroke for good(!) torque. Carburetor adjusted to richer than stoich for better performance, easy to adjust lean. Toothed belt drive to the clutch to quieten the drivetrain, chain drive to the wheel. Approx. 12:1 reduction, what let it down was the gearing.

Local kiddies stole it unfortunately but the legacy of the Hardly-Davidson (yeah, it got named) lives on to prove it doesn't have to be high-tech to actually work quite well. That and it made me wonder what it could do if a bit of high-tech were to be applied to it...

I'll post pics when the forum allows me to.

--Phil

10-02-2010, 01:17 AM	#1 (permalink)
PhilA EcoModder Newbie Join Date: Oct 2010 Location: Cut Off, LA, USA. Posts: 17 GTA - '87 AMC GTA 2k6 Silverado - '06 Chevrolet Silverado LS Thanks: 1 Thanked 1 Time in 1 Post	Homebrew scooter, ~120mpg This started out as a "Hey, that could be fun" project, built on a budget of approximately nothing, from junk and spare parts. About as low-tech as you can get, never built with fuel economy (or road use!) in mind, but at a steady 15mph or so I decided to see what kind of economy it would pull- as accurately as I could measure it would do 110-120mpg, that dropping to about 20-30mpg flat out at about 25mph. The engine was a 1955 model 75cc Suffolk Iron Foundry sidevalve engine. Static points-and-magneto ignition, Zenith updraught carburetor. Compression ratio raised from 6.0:1 up to 11.5:1, internally polished, timing adjusted to peak at about 4500rpm. New rings. Long stroke for good(!) torque. Carburetor adjusted to richer than stoich for better performance, easy to adjust lean. Toothed belt drive to the clutch to quieten the drivetrain, chain drive to the wheel. Approx. 12:1 reduction, what let it down was the gearing. Local kiddies stole it unfortunately but the legacy of the Hardly-Davidson (yeah, it got named) lives on to prove it doesn't have to be high-tech to actually work quite well. That and it made me wonder what it could do if a bit of high-tech were to be applied to it... I'll post pics when the forum allows me to. --Phil