I got the Roaduno racked and fendered and it's almost complete - I think just chain stay protection and a headlamp remain. Here's how it sits:
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Bill and Neal - appreciate the thoughts on the hub behavior and gearing! I got about 7 miles in this afternoon and here's what I've seen so far.
The hub shifts around 10mph on this wheel. So with the two rings I have the following (approx):
- Below 10mph (low, 1:1): 39" (28t) or 58" (42t)
- At or above 10mph (high, 1.38:1): 53" (28t) or 80" (42t)
The hub will upshift while pedaling but downshifts require a pause in pedaling.
On flat to downhill areas running in the 42t works pretty well - a stopped/slow speed gear of 58" is slightly lower than what I like as an all-round single speed gear. This is good for getting up to speed with a standing start (feels single speed-ish) then around 10mph the shift comes and I'm cruising at 80" - as long as the grade supports it or I feel like pushing that much - otherwise I'll shift down to 28t high/53" and spin or coast. 28t high/53" is a nice easy going gear for tootling or slight grades or small hills.
Starting in the 28t low/39" feels pretty slow on the road but should be useful for starting on hills. I have to be going pretty slow in order for the 28t low/39" gear to kick in on hills (and you have to stop pedaling to allow the hub to downshift), so I end up taking most hills standing in 28t high/53".
I've seen reports of some opening the hub and tweaking the springs that support the weights to provide more resistance and a higher speed shift. I think ideally the shift would occur a bit later - say 12-13mph. I wouldn't want it much higher than that as it's more of a cruising / townie setup than a road riding setup and I prefer lower cadences in this situation.
Looking forward to getting some more saddle time on it.
-Dave
On Friday, November 1, 2024 at 12:21:37 PM UTC-4 nlerner wrote:
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:
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?)
![PXL_20241030_210447300_roaduno-initial-1600.jpg]()
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)
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