Is it a 3+2?
Is it really a 6 speed?
How does that double stick shift work?
Let's start with terminology:
Sturmey Archer hubs traditionally have gears with names rather than numbers. However numbers are more familiar to people, so we'll use both:
Bottom - 1st Gear - the lowest of all gears
Low - 2d Gear
Normal - 3d Gear (the middle gear, direct drive)
High - 4th Gear
Top - 5th Gear (the highest gear)
The Sturmey Archer S5 hub is actually two three speeds in a single hub. It has a set of planetary gears like the AW, but it has two sun gears. The result is that you have two three speeds: a medium ratio three speed using one sun gear and a super wide three speed when the other sun gear is engaged.
Thus, you have a dual stick control. You basically have two banks of three gears.
Bottom Gear - 1st Gear. Both sticks are pulled back toward you.
Top - 5th Gear - the non-drive now pulls back but the drive stays full forward.
So if I said you have two banks of three gears, where is that last gear? It turns out that when in direct drive mode the gearing is the same no matter which sun gear you are using. Thus, as shown above, normal/3d gear has it so that the non-drive stick can be either forward or backward, it doesn't matter. Thus, you have two banks of three gears, but two of those six are the exact same ratio (so you only have 5 gears because you have a duplicate).
Could you use this on a 3 speed hub just using one side
ReplyDeleteYes, but the standard 3-speed "click" handlebar shifter is better for the 3 speed. These old stick shifter units do not have very positive-clicking stops for the three speeds. It's easy to get them out of adjustment compared to the standard shifter. I advise only using these as original equipment on the 5-speed. For the 3-speed use the clicker.
DeleteWhen did the S5.2 go out of production? I have one on a first generation early Brompton. / Pete
ReplyDeleteThe dates I have in my reference book are 1981-1990 for production. From 1981-83 as a steel shell hub, and then from 1983-1990 as an alloy shell hub. The 5.2 emerged from the need to improve the 5.1 to give more positive shifting on the left side (the non-drive side).
DeleteThanks, interesting. I'm sure I got the Brompton later than 1990, more like 93 or 94. They must have got hold of a batch of whatever stock Sturmey had and moved on to a different unit when it ran out. The gears are still fine.
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