Originally Posted by
Happy Feet
The goal would be a loaded touring bike based on a converted rigid mtb I already have. Steel frame, easy to cold set. As it is I have what I want in terms of bikes for regular road touring and off road touring so there isn't much practical need for building yet another platform in those areas. However, I have a good frame and lots of parts to build a conventional four pannier bike so without practical considerations I can experiment a bit. Boredom with derailers makes me look to something different but not so far as the expense of a Rohloff because I doubt I would ever use such a bike to its fullest extent.
I've have several SA hub'd bikes and like the simplicity of design so I could just go with that but I think the restricted range would be a bit of a pita for loaded touring on steep sustained hills. Most everything I do seems to involve a mountain pass of some sort. A hybrid double/triple IGH would be fun to build and withinin my experimental price range.
https://www.sturmey-archer.com/en/pr.../detail/rx-rd5
That five speed Sturmey Archer hub could work. Using a five speed cassette to approximate the five speed IGH in the calculator. Something like this:
https://gear-calculator.com/?GR=DERS...N=MPH&DV=teeth
For the crank I used an older road triple (52/42/30) which Campy used for their square taper cranks. FSA still makes a road triple, but not sure what the chainrings are.
And chose 20T sprocket. Calculated a five speed cassette that would be equivalent to the IGH, but the 13 and 31T sprockets are slightly off since a sprocket has to have a whole number of teeth for the calculator to work. Used 26 inch wheel.
There are a few redundant gears there, but you could play around with different chain ring sizes to get rid of some of the redundancies.
I did not read any of the PDFs, so I do not know if they have a minimum chainring to sprocket ratio. Rohloff sets a minimum chainring to sprocket ratio of 1.9 for riders that weigh less than 100kg (plus a few other restrictions), the reason for that is to prevent too much stress on the internal parts in the hub. My point is that in first gear on the hub, with a small granny gear on the crank you would put a lot of stress on some of the internal parts. It would be a major bummer to start cranking up a steep hill and suddenly shear off one of the planetary gear shafts or start stripping off some of the spur gears.
Yeah, that five speed IGH with a triple could work. Would have 15 gears and cross chaining would be insignificant..
For discussion purposes, this is the gearing on my folding bike, I am using an approximation of a triple crank in the calculator to substitute for the 3 speed IGH. Bike has 24 inch wheels, 8 speed Sram 11/32 cassette on a Sram Dual Drive rear hub, 39T chainring. The 29 and 53 sprockets are approximations of the actual gearing, Has 24 gears. With short chainstays, there is some cross chaining but not as bad as would be with a real triple.
https://gear-calculator.com/?GR=DERS...N=MPH&DV=teeth