Photo Help Photo 0190 - Do You Recognise Someone or Something?

[Graham Smith]

If you recognise someone or something in this photograph, please comment below…

 

[Graham Smith]

Caption reads “Rollie Free".

 

[mercurycrest]

Bass Lake 1980.

 

[bmetcalf]

Sprocket carrier!

 

[TouringGodet]

Along with that small sprocket on the rear, that Lightning also had a second extra tooth on the drive sprocket, over and above the extra tooth that some Lightning’s had.

 

[Flylow]

Along with that small sprocket on the rear, that Lightning also had a second extra tooth on the drive sprocket, over and above the extra tooth that some Lightning’s had.

How many?

 

[TouringGodet]

23

 

[bmetcalf]

Very much a side question, but were all of them made from pieces sawed off a round bar of a suitable steel alloy? I worked at a place that made helicopter transmissions and one spur gear was started that way, not from a forging.

 

[TouringGodet]

According to Richardson, a 45 tooth sprocket is the smallest that fits on a brake drum.

If my ratio calculator is correct, at 6000 engine RPM, and with a tyre diameter of 26.4 inches, and with a 42 tooth rear wheel sprocket, a 21 tooth gearbox sprocket equates to 151 MPH, a 22 tooth g/b sprocket is 159 MPH, and 23 tooth is 166 MPH. To reach the speeds Rollie hit, the 23 seems to work out nicely.

 

[TouringGodet]

Denis Minett says that the Rollie Free bike speed test was "Very satisfactory. To 6400 in 3rd - app 141 MPH". A speed of 141 at 6400 RPM in 3rd fits my calculator, with 23/44 tooth sprockets.