At the beginning of this year, when I noticed that my venerable old SON28 dynamo hub had developed a bit of play in the bearings, I decided to prioritise a project that I’d been working on to figure out how to open the thing up to service it. After searching online for any information that I could get, I finally arrived at a tool that worked to unscrew the internals from the hub shell.
I was certainly very pleased to see that the internals were completely free of any sign of corrosion, even after about 13 years of use. However, with the internals out of the hub I was able to feel that both of the bearings had some degree of play in them; the one on the terminal side of the hub being considerably worse.
When it comes to 7 speed hub gears that are available in the current market, there are two approaches to implementation: First, the single stage approach, with compound planet gears having 3 different radii. This type of 7 speed implementation can be found in hubs produced by Sturmey Archer, and by Sachs, since the mid 1990’s.
Very briefly, they achieve 7 speeds by gearing up and gearing down through the same planetary gear set, ie increase gears are achieved by driving the planet cage (hub is driven by the ring gear) and reduction is achieved by driving the ring gear (planet cage drives the hub shell). 3 reduction gears (as the planet pinions have 3 steps) + 3 increase gears + direct drive = 7 speeds. Note that this design is kind of like an extension of the Sturmey Archer 5 speed: essentially an S5 with an extra sun pinion and with 3 stepped planet pinions instead of the two-stepped planets in the S5.
Readers who are familiar with bicycle touring will probably know about the venerable Schmidt SON (Schmidt Original Nabendynamo), being one of the more highly regarded hub dynamos. I will leave it to others to weigh up the relative merits of different hub dynamo brands; this particular hub has certainly served me well over the last few years, and I would be reluctant to part with it, mainly due to the fact that it’s relatively simple to pull apart for overhaul.
I actually didn’t acquire my SON28 new (nor even second hand). It was owned first by my father, from circa 2008 until early 2011, and then he passed it on to my mother who owned it from 2011 until early 2017, when I acquired it.
This particular hub was originally owned by Thorin (who I know vaguely through the MBTC). Thorin gave it to John Harland, but John wasn’t going to use it because he doesn’t like the uneven gear ratios (more on that to come later). The idea of pulling it apart came up at another swap meet, when I saw an 8 speed for sale, and suggested buying it. John told me about the old internals that he’d got from Thorin.
This story begins at another Vintage Club swap meet. John Harland had brought along a lot of stuff to sell (he went there with more than 100 kg loaded on his bike, and didn’t want to take it all back home), which included two Sturmey Archer 3 speed hub gear + coaster brake jobs.
Fun fact, this all happened back in April, and it’s taken til now for me to get my shit together to write this up. Working full time, you see…
I already have more hub gears than I have bicycles to put them in, so I wasn’t all that enthusiastic about taking them. However, I noticed that one of the hubs was seized up, so I decided it could be interesting to pull it apart just to see what was wrong, and to attempt to restore it to working order. But mainly just to see how it works, since I don’t have any use for either of these hubs, and (being completely satisfied with cantilever brakes) no motivation to use a coaster brake hub. Continue reading “Strip down: Sturmey Archer S3C”
A close friend of mine, Glenn Rodda, has been using a Shimano Alfine 11 speed hub for a number of years (I’m not sure precisely when he first got one, but it was in 2010 or 2011). After his original hub started malfunctioning, he decided to buy a new hub and consequently the old one was donated to science. Which is how I was commissioned to pull it apart. Continue reading “Alfine 11 Strip Down”
Recently, I acquired a four speed Sturmey Archer hub. I was feeling a bit bored the other day, so I pulled it apart, and had a look at the bits.
Normally, taking apart these hubs requires a lot of effort, since the force of the pedals tightens the screw threads, but this time it was easy. Quite obviously someone else had pulled it apart before me, even the bearing lock nuts were only finger tight.
Here are some pictures of the internals:
First step is to undo the non drive side bearings, so that the internals (and axle) can be removed from the other side
Internals, removed from the hub.
Push rod that goes into the axle; note the teensy thread on it. This screws into a matching thread on the indicator chain.
I didn’t take any pictures of the bits of the internals, too busy focusing on what I was doing. Note the compound planet pinions: the way this system works is that there are two ranges depending on which sun gear is locked to the axle, a really wide three speed and a not so wide three speed. You can get 5 gears from this mechanism (middle gear of both ranges is direct drive, which is the same regardless of sun gear selection).
The four speed hub doesn’t use all of the available gears. Highest gear is the high gear of the not-so-wide range. Changing down from second to first (lowest) gear, the sun pinions are slid along the axle to engage the low gear of the really wide range.
In order to convert this hub to a five speed, we will modify the shift mechanism so that we can move the sun pinions independently of the main clutch. That way, we will be able to select the high gear in the really wide range; the only gear not available to the four speed hubs.
Many readers will be familiar with the Rohloff Speedhub, a 14 speed bicycle hub gear, and if you don’t know about it then you can go look it up on Google. Understanding how the mechanism works and pulling one apart have been a couple of my long term goals. This article won’t attempt to communicate the former (that is for a separate article I think) but I am going to tell you about how I pulled my hub apart and put it back together again (that is quite important too). You may want to go brush up on your knowledge of epicyclic gears right about now too, because I’m not doing any intro to that topic, it’s all assumed knowledge. Wikipedia has a very good article on the topic. Continue reading “Inside the Rohloff Speedhub”
This is based on an article that I wrote for Spokenotes, my bike club’s newsletter, but reworded and with more pictures. Pictures and diagrams are actually a very powerful learning tool for engineering; as an example, I learned how a 14 speed gear hub works primarily from a book that is written in German. I can’t read or speak German at all, but I could understand the pictures and diagrams in the book, and even spotted a mistake in one of them. But I digress. Hopefully from this article you will not only learn how to pull a dynamo hub apart, but you will also get a good idea of how they actually work. Having a background in physics would probably be useful for the latter, but hey, it’s not like it’s general relativity; I learned about electrical generators in high school. Continue reading “Dynamo hub overhaul”