Very nice Roaduno (from a fellow Boston-area Roaduno owner)! I have the SRAM version of that hub, currently on a 1950 Raleigh Lenton Tourist, and Bill's cautionaries do make sense. It's an interesting experiment.
I did a quick search for that S-A A2 hub, saw that it's discontinued, but came across this model that I didn't know about previously: https://www.modernbike.com/sturmey-archer-cs-rk3-3-x-9-speed-disc-hub-32h-black I could get downright Lindsay-esque with the possibilities that hub presents on a disc-brake compatible frame. Neal Lerner Brookline MA On Friday, November 1, 2024 at 10:45:37 AM UTC-4 Bill Lindsay wrote: > Silver with Purple for the win. Very nice. I like the willingness to > experiment on the gearing front, but don't know how it'll work out on a > multi-chainring bike. If the operating principal is the same as other > automatic shifting systems I've seen, then it's rotating weights inside the > hub. When those weights spin fast enough they fly outwards and cause a > shift. The only thing that mechanism "knows" is how fast the rear whee is > spinning. Let's say for the sake of argument that the rear hub shifts when > the rear wheel goes faster than 16mph. I don't know what speed it really > is, but it illustrates my curiosity. If you were in the 28x20 gear, at > 16mph you would be pedaling at roughly 75RPM and the shift would drop you > to 55RPM. That sound pretty reasonable. If you were in the 42x20 gear, at > 16mph, you would be pedaling at roughly 50RPM and the shift would drop you > to 37RPM. That's super slow pedaling. > > Given that, maybe the most practical way to use that drive train will be > to default to the small ring and only go to the big ring when you are > already cruising at speed, but shift down to the small ring pretty much any > time the hub shifts to "low", like at stops and such. In practice, you may > rarely use the big ring with the hub in LOW. I guess it all depends what > hub RPM the thing fires with your wheel set up. > > Science! > > Bill Lindsay > El Cerrito, CA > On Wednesday, October 30, 2024 at 8:26:04 PM UTC-7 DavidP wrote: > >> I've completed the initial build of my 54.5cm Roaduno frame and taken it >> around the block. It's fully rideable but I'll be adding fenders, a >> rack/basket, lights, and bags. It's a 2x2 with a 2 speed IGH in the back. >> (Road-deux-by-deux-no?) >> >> [image: PXL_20241030_210447300_roaduno-initial-1600.jpg] >> >> A few more photos in the Flickr album: >> https://www.flickr.com/photos/ordinarylight/albums/72177720321621073/ >> >> I've been hung up on trying an automatic 2 speed IGH (Sturmey A2) and the >> Roaduno made an excellent platform for it. This hub gives 1:1 and 1:1.38 >> ratios and automatically shifts based on wheel speed. No messing with >> kickbacks but also no control over the shift. Pairing the IGH with double >> crank for a 2x2 setup gives some say in the matter (and a wider range). >> >> Current gearing (20t cog) gives 39" and 53" with the 28t ring and 58" and >> 80" with the 42t. >> >> I'll need more miles to be able to say much about how it works out, but >> am optimistic after my quick spin. >> >> Other build details: >> Sun CR18 rims (36h rear, 32h front) with Sturmey A2 IGH and Kasai dyno hub >> Resist Nomad 700x45 tires (measuring 41mm on these rims) >> 20t Nexus cog with Shimano 600 tricolor RD (as a tensioner) >> Shimano Nexave FD-T401 top swing / low clamp and Silver 1 DT shifter >> New Albion Clipper (XD2) triple - 44t guard + Sugino 42/28 rings >> MKS Sylvan Gordito pedals >> Riv 182.55 saddle >> Technomic 120mm stem with Choco bar >> Tektro R559 brakes and FL540 levers >> >> -Dave >> (near Boston) >> > -- You received this message because you are subscribed to the Google Groups "RBW Owners Bunch" group. To unsubscribe from this group and stop receiving emails from it, send an email to rbw-owners-bunch+unsubscr...@googlegroups.com. To view this discussion visit https://groups.google.com/d/msgid/rbw-owners-bunch/6fbf65ec-92fe-4f09-9b36-27a24be916adn%40googlegroups.com.
