Wednesday, February 22, 2012

When 3 Speeds Weren't Enough

Around 1936, Cyclo introduced a clever way around expanding the gear range of the 3 Speed Hub. By placing a 2 or 3 gear 1/2x1/8th inch cog block on the driver of the hub and adding a Derailleur, The standard 3 speed bicycle could be converted into a 6 or 9 speed bicycle.
I used this system on 3 different bicycles including the DL-1 I posted back on November 18th 2011 and a BSA Gold Vase I had back in the early 80's that used a S5, five speed hub to then have a 15 Speed touring bike.

This cog block was a later version with the 3 splines to replace the single cog. I found that for the system to be totaly dependable, the cir-clip needed to be flattened by placing the clip on a anvil and pounding it with a ball peen hammer. This would allow the clip to fit better because of the space needed for the cogs was too wide for the Sturmey Archer Driver by about 1/3 of a millimeter. Under heavy load, the cogset could pop off requiring working it all back together with the wheel on, or correctly with the wheel removed.

My DL-1 Nine Speed. High gear on this bike was around 117" and low gear around 22"

High gear on this 15 speed BSA bicycle was 137"! Notice the DBU on the seat tube for the perfect touring rig!

The Derailleur worked in the opposite direction then most so that when you pulled back on the lever, it would change into its high gear. What a great feeling when its really a high gear and your at the top of a large hill!


  1. My DL-1 Nine Speed. High gear on this bike was around 117" and low gear around 22

    Wow, that's over 500% range! Have you ever plotted the gear spacing over those 9 gears? I wonder how much of an even distribution one can achieve with judicious cog choices.

  2. I never did or had any reason to. Te low cog was a 23t and the high was a 15t The bicycle had 28x1 1/2 tires, (remember the British measure the rim) and it had the standard Sturmey Archer AW hub.