Hybrid gearing (with acknowledgememts to Robin Walker)
Posted: Monday 21st September 2020
As we get older the need for lower gears becomes more prevalent and there are many ways of achieving this. Probably the most common way is to keep your existing derailleur block or your hub gear sprocket the same and go for smaller chainrings. The only problem with smaller chainrings is that, in my opinion, aesthetically they do not look right! Or is it pure vanity on my part that I can’t face the fact of geting old!!! On my lightweights that are fitted with derailleur gears I have fitted 46/36 chainrings and 14-24 blocks, which is the maximum capacity (20 teeth) for most derailleurs of the 40’s and 50’s on non-touring lightweight bikes. This combination gives me a top gear of 88.7″, I can’t remember the last time I used it, in fact, I believe that sprocket is now covered in cobwebs, and a bottom gear of 40.5″, which I use very frequently but is not quite low enough to use on the lower slopes of the Mendips where I live! I know…
I know, a couple of ‘granny rings’ would solve that problem, but, as I said earlier, aesthetically, they just don’t look right!!! My two lighweights that are fitted with Sturmey Archer FM’s have a combination of a 46 toothed chainring and a 22 toothed sprocket, giving gear ratios of 64.1″ to 37.7″. The 22 sprocket looks a little on the large size, but I can live with it, and I can also live with the ratios, but, as tempus fugit, I will need to find lower gears! I’m aware of the Cyclo Converter of combining a two speed derailleur to a hub gear, and, in fact, I do believe that someone does a five speed derailleur combined with a hub gear! But all these conversions look very ‘agricultural’, in my opinon! And, of course, you need to fit two gear levers!
Reading issue No. 343 of the V-CC’s News and Views I had a ‘Eureka’ moment! I read Robin Walker’s article “Hybrid Gearing – Another Solution.” Robin had fitted his hub geared bike with two 3/32″ chainwheels, 46/36, a 3/32″, a 19 tooth rear sprocket, a Cyclo/Osgear Chain tensioner and a Cyclo Benelux rod operated front changer. BINGO! I couldn’t wait to get started.
I spoke to Robin on the phone and he informed that the conversion was a bit fiddley but could be done in a morning. It took me a day! But then, I ain’t so clever. The only difference I made to Robin’s conversion was that I used a 22 tooth rear sprocket, a French Cyclo front mech. and jockey wheel with teeth. Robin had used a round jockey wheel on the chain tensioner which had a tendency to jump. I also used a Simplex chain tensioner, courtesy of Mark Stevens and I cannot recommend this conversion highly enough. As Robin says, and I quote “…everything is period correct for an early 1950’s bike.” The other thing he mentioned, and I quote again “… there is a slight chain rub between the chainrings when running on the inner ring.”, I can live with that. I have a gear ratio of 64.1″ to 29.5″, “… touring gears on a racy looking bike.” to quote Robin again! I LOVE it!