Author Topic: New from Rotor, a hydraulic 13 speed group and a 10-46 cassette  (Read 1848 times)

Re: New from Rotor, a hydraulic 13 speed group and a 10-46 cassette
« Reply #50 on: July 11, 2018, 03:09:31 pm »
the maths is complicated but it is possible (in a linear form) to contrive an involute shape so that the rollers can share the load and the usual drag through movement whilst meshing is minimised, because of the roller bearings. The idea can be refined by angling the teeth (which they are looking into) as well as giving them exactly the right profile.

But (as per a comment I posted yesterday on the cycling UK forum) this transmission creates axial thrusts in the 'chainring' and the 'sprocket' which may not manifest a lot of drag under constant torque conditions but are more likely to do exactly that if the torque is like  real pedalling, i.e. 'pulsy'.

cheers
 

Re: New from Rotor, a hydraulic 13 speed group and a 10-46 cassette
« Reply #51 on: July 11, 2018, 03:24:59 pm »
Somewhere I've seen a photo from the late 19th or early 20th century of PotUS amid a security unit mounted on Columbia shaft-drive bikes. This design is for rather different riding conditions though. And of course they were single-speed.

I can't find even a hint of price or market dates in that road.cc piece.
The earth is vast and beautiful and contains many miraculous places. (Chekhov)

Re: New from Rotor, a hydraulic 13 speed group and a 10-46 cassette
« Reply #52 on: July 11, 2018, 03:31:56 pm »

I can't find even a hint of price or market dates in that road.cc piece.

reason being that it is all just flim-flam.

All they have done so far is to test a singlespeed version; the multi-speed version is just a non-functioning mock-up and they admit they don't have the skill set required (does anyone?) to make it work....

cheers

Porkins

  • Formerly Nick H. And a long time ago etc, Eurostar
Re: New from Rotor, a hydraulic 13 speed group and a 10-46 cassette
« Reply #53 on: July 11, 2018, 03:33:21 pm »
First shipment for the Rotor 1x13 is apparently planned for 1Q19.

Rotor have talked more about 1x13 being as efficient as 2x11:

Quote
Rotor has been doing a lot of work looking at optimal cadence and speed, mining data from their professional athletes using their power meters. What they’ve discovered is that optimal cadence isn’t a rigid thing; instead it varies, with a narrower band in higher gear ratios and a wider spread as you get lower. The engineers showed us a lot of graphs, but the upshot is that with the correct 13-speed cassette you can cover all speeds, with the same spread of gears as a double, and keep the rider within the optimal cadence range the whole time. So there’s no downside, in terms of pedalling efficiency, to running 1x13 instead of 2x11. TO replace a 53/39 and 11-28 setup, you can run a 50T chainring and Rotor’s 10-36 cassette. For road riding Rotor is offering the 10-36 and a slightly wider ratio 10-39, which is more the equivalent of a compact double and a wider-range cassette. There’s a 10-46 which can be used for gravel or mountain biking, and a 10-52 for the widest range off-road.

http://road.cc/content/tech-news/244867-depth-rotor-1x13-all-you-need-know-about-rotors-latest-hydraulic-groupset


Re: New from Rotor, a hydraulic 13 speed group and a 10-46 cassette
« Reply #54 on: July 11, 2018, 03:39:55 pm »
they are talking about biomechanical efficiency and how it varies with cadence; basically they are arguing that wider spaced gears are not so bad after all.

 What they don't appear to be talking about is the efficiency loss due to using stupid small sprockets and stupid heavily angled chainlines.

cheers

Porkins

  • Formerly Nick H. And a long time ago etc, Eurostar
Re: New from Rotor, a hydraulic 13 speed group and a 10-46 cassette
« Reply #55 on: July 11, 2018, 04:09:14 pm »
Why are small sprockets bad? And how small is small?

Re: New from Rotor, a hydraulic 13 speed group and a 10-46 cassette
« Reply #56 on: July 11, 2018, 04:29:58 pm »
I believe that if you can have a big-big with the same chainline as a small-small then you will save a couple of Watts because the chain has to bend less at each link and that results in reduced drivetrain losses. That's why you see track/TT bikes with giant chainrings and mid sized sprockets.
On how small is small - 10t is pretty damn small. :)

I don't know if the benefit of having no front mech outweighs this reduced efficiency...

Re: New from Rotor, a hydraulic 13 speed group and a 10-46 cassette
« Reply #57 on: July 11, 2018, 04:43:20 pm »
Why are small sprockets bad? And how small is small?

small sprockets suffer unduly with increased losses known as 'chordal losses'. These losses increase whenever the number of teeth on the sprocket is reduced. The magnitude of this effect is comparable to that of having a poor chainline, so the typical outcome is that the measured efficiency does not vary a huge amount over the range of gears offered by (say) the big chainring on a double; in the high gears the chainline is good but the chordal losses are bad, and in the lower gears the chordal losses are much reduced but the chainline renders the gear less efficient than it ought to be.

Losses incurred these ways can be of the order of one to two percent. Well worth worrying about. 

Thus if you have choice of a regularly used gear of (say) 39/14 or 50/18 (with a comparable chainline) the latter is liable to be a percent or so more efficient.

The British cycling track team gained ~0.5% transmission efficiency (for virtually nothing) at Rio by running slightly larger sprocket and chainring combinations  than normal.  If you choose a 1x drive (with a small chainring) on a road bike, you are throwing that much or more away, all the time.

cheers


Porkins

  • Formerly Nick H. And a long time ago etc, Eurostar
Re: New from Rotor, a hydraulic 13 speed group and a 10-46 cassette
« Reply #58 on: July 11, 2018, 04:56:26 pm »
And you'd shorten the life of chain, rings and sprockets?

Re: New from Rotor, a hydraulic 13 speed group and a 10-46 cassette
« Reply #59 on: July 11, 2018, 07:59:33 pm »
And you'd shorten the life of chain, rings and sprockets?

yes, loads are higher on the chain, and each link articulates through a bigger angle as it goes over smaller sprockets.  This (and running with worse chainlines) does reduce the life of any given chain, sprockets, chainring.

cheers

grahamparks

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Re: New from Rotor, a hydraulic 13 speed group and a 10-46 cassette
« Reply #60 on: July 12, 2018, 09:16:09 am »
Weight?  Aero (not just the mech and extra ring, but also Q factor)? Ability to use narrow/wide rings and reduce dropping chains? One less mechanical/electrical thing to go wrong? No redundant gears.

I have 1x11 on my audax bike because primarily because I wanted sequential shifting. I also love never having to worry about chain rub on the front derailleur - 105 5800 seems impossible to adjust correctly in this regard, or possibly it's just my particular frame or my poor maintenance skills.

1x11 can give you the same number of *distinct* gears as 2x7 or 2x8 (depends on the chainset/cassette size). 1x13 should be pushing well into 2x9 territory.

(My non-audax road bike now has sequential shifting and no front mech rub thanks to Di2, although the moment it simultaneously shifts the front mech is far from seamless)

Re: New from Rotor, a hydraulic 13 speed group and a 10-46 cassette
« Reply #61 on: July 12, 2018, 12:41:05 pm »
re fd-5800 setup; there are two possibilities for cable mounting at the pinch bolt, that are meant to allow for variations in cable approach angle to the mech caused by variations in cable routing (frame design) and/or chainline. You are meant to use a little gauge to measure the cable approach angle and choose from there.

That this isn't a perfect solution is tacitly admitted by shimano in that they have completely redesigned the parts for the later 11s FDs. For example the current 105 FD (FD-R7000) has the new system which has a separate adjuster screw in the mech to allow for variations in chainline etc.  Considerably easier to set up IME.


Problems with the FD-5800 type setup include finding it impossible to set the FD up so that it never rubs, and that the force required to move the FD from the low gear position is excessively high.

My own view is that using a half-decent double setup, you can have gear ratios of ~40" to ~100" on the big ring and the small ring can do gears up to about 60" if necessary. Thus anything that is 'a proper climb' (including false flats midway) can be approached in the small ring and for everything else the big ring is OK. This minimises the number of double-shifts that are required.

cheers


grahamparks

  • London N19
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Re: New from Rotor, a hydraulic 13 speed group and a 10-46 cassette
« Reply #62 on: July 12, 2018, 10:00:49 pm »
re fd-5800 setup; there are two possibilities for cable mounting at the pinch bolt, that are meant to allow for variations in cable approach angle to the mech caused by variations in cable routing (frame design) and/or chainline. You are meant to use a little gauge to measure the cable approach angle and choose from there.

The perennial problem is that the correct position for the small ring / lowest gear requires the pinch bolt to go beyond top dead centre, where neither the cable nor the return spring are doing much of anything to hold the mech in a particular place, so it doesn't go as far inboard as it should.

Re: New from Rotor, a hydraulic 13 speed group and a 10-46 cassette
« Reply #63 on: July 13, 2018, 10:08:37 am »
I don't think it can quite go over  centre vs the cable pull (if it did it would never move again) but you are right, in that the first trim position (for running small-small) is incredibly sensitive to small changes in cable length in mechs like FD-5800. I think that FD-R7000 etc is better in this respect but it still ain't great.

cheers

mattc

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Re: New from Rotor, a hydraulic 13 speed group and a 10-46 cassette
« Reply #64 on: July 13, 2018, 10:21:44 am »
Front shifting was solved decades ago, wasn't it?

Has never ridden RAAM
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Porkins

  • Formerly Nick H. And a long time ago etc, Eurostar
Re: New from Rotor, a hydraulic 13 speed group and a 10-46 cassette
« Reply #65 on: July 13, 2018, 12:09:48 pm »
Here's a Rotor customer committing the cardinal chain deflection sin. Must be a noob.






Re: New from Rotor, a hydraulic 13 speed group and a 10-46 cassette
« Reply #66 on: July 13, 2018, 12:11:36 pm »
Front shifting was solved decades ago, wasn't it?

For most of us, yes.

The problem is that some people insist on pedalling with high power through the shift. I see (and hear) this often on my group rides, even from experienced cyclists who really should know better. They don’t seem to realise that if you let up the power while continuing to spin the cranks you can change gear as quickly as the derailleur moves and then instantly resume power. The overall effect on speed is nil because the sub-second rest allows commensurately more work to be done over the next few seconds. If you’re in a tight paceline, precede the shift by a surge in power as if you were about to stand up to reduce the risk of the daydreaming person behind you touching your wheel.

What is Cavendish or his mechanic doing wrong in the photos above, Porkins?

Porkins

  • Formerly Nick H. And a long time ago etc, Eurostar
Re: New from Rotor, a hydraulic 13 speed group and a 10-46 cassette
« Reply #67 on: July 13, 2018, 12:13:28 pm »
Big ring with big sprocket.

Re: New from Rotor, a hydraulic 13 speed group and a 10-46 cassette
« Reply #68 on: July 13, 2018, 01:01:22 pm »
That's Rotor cranks bit Di2 for shifting though, right?
Pros seem to like big-big. I suspect they would prefer to stay in the big ring all the time (outside of mountains).

Porkins

  • Formerly Nick H. And a long time ago etc, Eurostar
Re: New from Rotor, a hydraulic 13 speed group and a 10-46 cassette
« Reply #69 on: July 13, 2018, 01:24:12 pm »
Yes, it's Dura Ace with Rotor crankset

Torslanda

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Re: New from Rotor, a hydraulic 13 speed group and a 10-46 cassette
« Reply #70 on: July 14, 2018, 05:21:27 pm »

Pros seem to like big-big.


That's because they never have to worry about maintenance. At the end of every racing day a grease monkey will service/clean/strip and rebuild the bike while they go for a shower and a massage.
VELOMANCER

Well that's the more blunt way of putting it but as usual he's dead right.

Re: New from Rotor, a hydraulic 13 speed group and a 10-46 cassette
« Reply #71 on: July 14, 2018, 07:47:15 pm »
That's Rotor cranks bit Di2 for shifting though, right?
Pros seem to like big-big. I suspect they would prefer to stay in the big ring all the time (outside of mountains).

I did notice with Di2 that it "protects" you from using the bottom 3 cogs with the small ring, but doesn't stop you going Big Big;
I kind of expected it to do so since I've got the "bad habit" of using Big-Big, something just feels better about it.

Re: New from Rotor, a hydraulic 13 speed group and a 10-46 cassette
« Reply #72 on: July 14, 2018, 09:09:28 pm »
I use Big Big all the time. It's my pulling away from a standstill gear of choice, so most of the time when I'm using it, there is a fair bit of torque going through it.

It doesn't cause any issues at all and I think the whole cross chaining thing is overstated.

I'd never use small small though! It just feels mushy, and needlessly using small sprockets is definitely bad for the chain - much worse than cross chaining in my opinion.

Porkins

  • Formerly Nick H. And a long time ago etc, Eurostar
Re: New from Rotor, a hydraulic 13 speed group and a 10-46 cassette
« Reply #73 on: July 14, 2018, 09:21:11 pm »
It's obvious that it shortens the life of chain, rings and sprockets. I don't understand why you wouldn't care about that, unless you are a pro cyclist.

quixoticgeek

  • Mostly Harmless
Re: New from Rotor, a hydraulic 13 speed group and a 10-46 cassette
« Reply #74 on: July 14, 2018, 09:26:30 pm »
It's obvious that it shortens the life of chain, rings and sprockets. I don't understand why you wouldn't care about that, unless you are a pro cyclist.

Shorten it by how much?

Road.cc did an article about this http://road.cc/content/feature/213468-cross-chaining-it-really-all-bad

I am very guilty of cross chaining, in both rings, my current chain has 2700km on the current chain, and it's not at 0.5% yet.

J
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