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timo888 08-19-08 07:36 AM

Hub Gears: does near-perfect efficiency really matter?
 
Do small gains or losses in efficiency really matter to commuters, multi-modal commuters, and leisure riders?
"If racers, or even commuting or touring cyclists, could choose optimum gears
they would be hundreds of meters ahead at the end of 60 km (37 mi)."
-- The mechanical efficiency of bicycle derailleur and hub-gear transmissions
Chester Kyle and Frank Berto, in HUMAN POWER: the technical journal of the International Human Powered Vehicle Association NUMBER 52 SUMMER 2001

Regards
T

Diode100 08-19-08 07:45 AM

I think you have to decide if you are a leasure cyclist or a performance cyclist with sporting motivations or ambitions. If you are the latter, then it is going to matter to you, if you are the former, then as long as the gears are properly adjusted and maintained, I doubt you would know any difference. I'd include casual commuters as leasure cyclists, and also anyone who doesnt have a speedomter on their handlebars.

datako 08-19-08 08:21 AM

Don't notice any losses on my 3 speed Sturmey-Archer. Slightly noticeable on Nexus 8 speed, and horribly so on Rohloff 14 speed.

Sammyboy 08-19-08 08:47 AM

Theoretically, however, the Rohloff is MORE efficient than the Nexus, isn't it?

MichaelW 08-19-08 12:10 PM

The world record for cycling around the world was set using a Rohloff hub. It probably has more to do with ease of maintenance than simple mechanical efficiency.
I like my new Alfine hub gears, they dont feel at all draggy.

Sixty Fiver 08-19-08 12:15 PM

Efficiency is important when the miles really start to pile up... there are a lot of commuters who log more miles than the most serious roadies.

The reduced serive requirements of IGHs also cannot be overlooked.

Foldable Two 08-19-08 12:16 PM

Quote:

Originally Posted by timo888 (Post 7301092)
"If racers, or even commuting or touring cyclists, could choose optimum gears
they would be hundreds of meters ahead at the end of 60 km (37 mi)."
-- The mechanical efficiency of bicycle derailleur and hub-gear transmissions
Chester Kyle and Frank Berto, in HUMAN POWER: the technical journal of the International Human Powered Vehicle Association NUMBER 52 SUMMER 2001

How many casual/commuter type riders do 60 km (37 miles) per ride? Maybe 6 km (3.7 miles) is more like it, therefore the actual advantage would be in the TENS of meters. Not a really noticeable advantage.

Disclaimer: I am a casual rider, but do stay in Direct Drive as much as possible on my Dual-Drive BF - I use the upper and lower ranges on more extreme terrain. Is there a big difference? I don't know, but will check it out on our next ride by staying HIGH range for the whole ride.

rhm 08-19-08 12:30 PM

Quote:

Originally Posted by timo888 (Post 7301092)
Do small gains or losses in efficiency really matter to commuters, multi-modal commuters, and leisure riders?

No.
Quote:

Originally Posted by timo888 (Post 7301092)
"If racers, or even commuting or touring cyclists, could choose optimum gears
they would be hundreds of meters ahead at the end of 60 km (37 mi)."
-- The mechanical efficiency of bicycle derailleur and hub-gear transmissions
Chester Kyle and Frank Berto, in HUMAN POWER: the technical journal of the International Human Powered Vehicle Association NUMBER 52 SUMMER 2001

I agree. An efficient pedaling style matched to a gear appropriate to the terrain makes a more of difference than is lost through the hub.

For this reason I much prefer my Sturmey Archer 8-speed hub over my Sturmey Archer 3-speed hub; I believe the latter is a more efficient transmission, but the engine is more efficient with the 8-speed!

-=(8)=- 08-19-08 01:37 PM

My hub/shafty is a dream from a maintenance standpoint, but like a
bad dream from an efficiency standpoint...one of those ones where you
are running real hard but not going anywhere :eek:

EvilV 08-19-08 01:52 PM

Quote:

Originally Posted by MichaelW (Post 7303018)
The world record for cycling around the world was set using a Rohloff hub. It probably has more to do with ease of maintenance than simple mechanical efficiency.
I like my new Alfine hub gears, they dont feel at all draggy.

That guy is on BBC1 tonight and for a few more nights in a series of programmes about his massive and triumphant ride. I think its 22.35. His name is Mark Beaumont and he did a hundred miles a day for about 195 days.


By the way, I saw an engineering analysis that showed that an oil lubricated and run in sturmy archer three speed hub was more efficient than derailleur gears. Once the chain line starts to run out of true on a deraillieur the efficiency drops off quite sharply. The middle gear or direct drive on a srf3 is as efficient as single speed and the other two gears are only about 4% down on 100%. Plenty of the derailieur gears are that far down because of chainline issues as I understand it.

brakemeister 08-19-08 02:20 PM

it almost always depends on what you are trying to proove ......

all kinds of statements can be twisted and turned just in the right direction that the findings seem to make sense .....

just like the no service idea of all can hubs.... yes much less service, but than eventually they do need service and than what ? where to bring it?. do it yourself ? what if you need any spare part of any internal hub in the middle of Iowa ( or Illinois , Indiana .....) .... than all of the sudden a derrailleur doesnt seem to bad anymore.....

so there is always a pro and con involved ..... I like cans as they just look cool in my opinion .... and they came a long way , indeed.... but like everything else they might have their limits as well...

thor

datako 08-19-08 02:34 PM

Quote:

Originally Posted by brakemeister (Post 7303856)
...just like the no service idea of all can hubs.... yes much less service, but than eventually they do need service and than what ? where to bring it?. do it yourself ? what if you need any spare part of any internal hub in the middle of Iowa ( or Illinois , Indiana .....) .... than all of the sudden a derrailleur doesnt seem to bad anymore.....

Yes but by that time you have worn out several derailleurs and cassettes.

Sturmey-Archer hubs are actually quite simple to fix if done by the book. Parts are readily available. Most of the problems they have are actually poor adjustment of the cables which can be quickly fixed.

I would hope to get about 3-4,000 miles out of a derailleur and cassette. I would expect a hub gear to last the life of the bike.

In cycling magazines I have covering several decades of the 20th century, there are many instances of people covering in excess of 50,000 miles on one hub, and this was not seen as remarkable. Hopefully improvements in technology means that modern versions should be capable of exceeding these mileages.

As far as a round the world trip, I think I'd pick a 3 speed S-A. In direct drive (middle gear) it is as efficient as a single speed.

timo888 08-19-08 03:21 PM

Quote:

Originally Posted by brakemeister (Post 7303856)
it almost always depends on what you are trying to proove ......

all kinds of statements can be twisted and turned just in the right direction that the findings seem to make sense .....

just like the no service idea of all can hubs.... yes much less service, but than eventually they do need service and than what ? where to bring it?. do it yourself ? what if you need any spare part of any internal hub in the middle of Iowa ( or Illinois , Indiana .....) .... than all of the sudden a derrailleur doesnt seem to bad anymore.....

so there is always a pro and con involved ..... I like cans as they just look cool in my opinion .... and they came a long way , indeed.... but like everything else they might have their limits as well...

thor

Thor,
I don't disagree with you -- service and parts availability are issues with any product that has limited market penetration ... or with proprietary parts in general, unless they happen to be de facto standards.

But my question has less to do with internal hubs vs derailers than it has to do with the engineering focus of companies who make these hubs. If they're trying to find some "sweet spot" between Reliability and Efficiency, whose needs would be served by giving more emphasis to maximum efficiency over maximum reliability? Conversely, whose needs would be served by emphasizing reliability over efficiency ... assuming there's a tradeoff, i.e.that one comes at the expense of the other.

What demographic(s) or sub-markets would you say are attracted to internal hubs?

Regards
T

noteon 08-19-08 03:35 PM

Quote:

Originally Posted by timo888 (Post 7301092)
Do small gains or losses in efficiency really matter to commuters, multi-modal commuters, and leisure riders?

No. Even hundreds of meters over 60km don't matter much, since that's a difference of what, a minute at most? My commute varies more than that already, just as a function of my mood.

But the words "less efficient" are scary to people who are new to it all.

jur 08-19-08 04:10 PM

Quote:

Originally Posted by timo888 (Post 7301092)
Do small gains or losses in efficiency really matter to commuters, multi-modal commuters, and leisure riders?

No. I can readily see the difference between my various bikes, and commute on the bike for 70 minutes each way. I don't pick whatever bike I'm going to ride the day for efficiency; I pick it for applicability. Wet weather mostly sees the R20. Training days for long rides, I choose the Swift. Whimsically I take the Mini. Right now I'm multi-moding and am using the Yeah because of the easy folding. Efficiency never enters my mind.

alhedges 08-19-08 04:21 PM

The small efficiency losses really don't matter - at least for my ride, any difference they might make is lost in the noise of more serious delays: red lights, me being tired, tires not optimally pumped, etc.

But - tying in with Thor's point - I think it is also a mistake to assume that modern IGHs (especially those with multiple gears) will last forever just because the old-school SA 3-speeds did. A friend of mine had two Nexus IGH malfunction (a 7 speed and an 8 speed); each lasted around a year and was basically irreparable. The hubs were on Trek Navigators, which, interestingly, seems to no longer sell models with IGHs.

EvilV 08-19-08 04:27 PM

Quote:

Originally Posted by timo888 (Post 7304184)
Thor,
But my question has less to do with internal hubs vs derailers than it has to do with the engineering focus of companies who make these hubs. If they're trying to find some "sweet spot" between Reliability and Efficiency, whose needs would be served by giving more emphasis to maximum efficiency over maximum reliability? Conversely, whose needs would be served by emphasizing reliability over efficiency ... assuming there's a tradeoff, i.e.that one comes at the expense of the other.

What demographic(s) or sub-markets would you say are attracted to internal hubs?

Regards
T

But is that the trade off that is made. I don't see there really being a continuum with efficiency at one end and reliability at the other. I don't think these variables are even remotely related. In fact although I am far from being an engineer and am only a bodging dabbler, I feel sure that there are two quite different variables here and that the continuums (plural?) range from reliability -> unreliability and a quite separate one of efficiency -> inefficiency. I'm pretty tired just now so maybe I missed something here.

noteon 08-19-08 06:29 PM

This reminds me of a related question that I never remember once I'm off the bike.

Is there anything on an IGH that's analogous to cross-chaining? One of the most useful ratios on my Xootr Swift (SRAM Dual Drive + 11/32) is the highest DD gear and lowest cassette gear. It slots right in between two of my basic cruising speeds. I can't think of why it would cause any problems, but better to ask than assume.

(And if the answer is "No, you moron, that's the whole point of an IGH," then that gives us another advantage to add to the list: Access to all ratios without fear of cross-chaining.)

Sixty Fiver 08-19-08 07:03 PM

You will get some chaion deflection on the SRAm dual drive but that won;t be any m,ore severe than what you get on a derailer equipped bike when you are running off the middle chain ring.

I am not sure what gear on the SRam hub is direct drive... on an SA 3 speed hub it is it's 2nd which is about as efficient as a drive gear gets and older SA hubs tend to be far better made than later production models.

noteon 08-19-08 07:48 PM

If I understand that answer (which I'm not sure I do), you're talking about chain deflection between the chainwheel and the cassette, yes?

My curiosity--and please bear with me if I'm not stating it clearly--is about the relation between the IGH and the cassette. Do the kinds of combinations that cause cross-chaining concerns between a cassette and triple chainwheel pose any problems with an IGH and cassette?

And if not, are there any concerns? Or can I just use whatever combination results in a ratio that feels good at the moment--e.g., highest IGH gear with lowest cassette gear?

BruceMetras 08-19-08 08:20 PM

Quote:

Originally Posted by noteon (Post 7305646)
If I understand that answer (which I'm not sure I do), you're talking about chain deflection between the chainwheel and the cassette, yes?

My curiosity--and please bear with me if I'm not stating it clearly--is about the relation between the IGH and the cassette. Do the kinds of combinations that cause cross-chaining concerns between a cassette and triple chainwheel pose any problems with an IGH and cassette?

And if not, are there any concerns? Or can I just use whatever combination results in a ratio that feels good at the moment--e.g., highest IGH gear with lowest cassette gear?

That's the beauty of Dual Drive.. big gear range, no cross chain issues... use whatever feels good... :thumb:

makeinu 08-19-08 08:48 PM

Quote:

Originally Posted by noteon (Post 7305646)
If I understand that answer (which I'm not sure I do), you're talking about chain deflection between the chainwheel and the cassette, yes?

My curiosity--and please bear with me if I'm not stating it clearly--is about the relation between the IGH and the cassette. Do the kinds of combinations that cause cross-chaining concerns between a cassette and triple chainwheel pose any problems with an IGH and cassette?

And if not, are there any concerns? Or can I just use whatever combination results in a ratio that feels good at the moment--e.g., highest IGH gear with lowest cassette gear?

I don't know anything about it, but from what I understand the cross chaining problem is that, as the various cogs and rings of a derailleur system are located in different positions, when the chain is in the leftmost position in the rear and the rightmost position in the front (or vice versa) it gets pulled sideways, thus, causing the chain to rub against the ring and cog.

Since there's no chain or any other movable part connecting the cassette to the internal gears on a DD setup there can't be anything that gets pulled into a rubbing position as with cross chaining. So whatever problems the setup may or may not have I find it hard to imagine how they could possibly be described as "analogous" to cross chaining.

noteon 08-19-08 08:48 PM

That's what I was hoping to hear. Being able to shift into that gear without worrying about the chain coming off is lovely.

noteon 08-19-08 08:50 PM

Quote:

Originally Posted by makeinu (Post 7305979)
Since there's no chain or any other movable part connecting the cassette to the internal gears on a DD setup there can't be anything that gets pulled into a rubbing position as with cross chaining. So whatever problems the setup may or may not have I find it hard to imagine how they could possibly be described as "analogous" to cross chaining.

The concept of pairing extremely opposed gears and having mechanical problems as a result would be the crux of the analogue.

(I can probably also find a way to use the word "synecdoche" in there if pressed...)

makeinu 08-19-08 09:11 PM

Quote:

Originally Posted by Foldable Two (Post 7303062)
How many casual/commuter type riders do 60 km (37 miles) per ride? Maybe 6 km (3.7 miles) is more like it, therefore the actual advantage would be in the TENS of meters. Not a really noticeable advantage.

Yup, and taking your full attention away from effective pedaling in order to shift a few times over those 3.7 miles probably loses you tens of meters anyway. Sometimes less is more (as I'm sure the members of the SS FG subforum would attest if they ever took a break from trying to be cool).

Quote:

Originally Posted by noteon (Post 7306002)
The concept of pairing extremely opposed gears and having mechanical problems as a result would be the crux of the analogue.

(I can probably also find a way to use the word "synecdoche" in there if pressed...)

I believe the late Sheldon Brown may have destroyed a Nexus 8 speed by pairing it with a wide cluster and a triple and using the lowest possible gear.

The moral of the story being that some gears of an IGH perform better than others and if you use an inefficient combination of external gears to drive an inefficient gear on the IGH the two choices will compound to a doubly inefficient overall drive (perhaps even out of spec). Though I think you'd be hard pressed to create such an issue with a 3 speed IGH like a DD (just like I doubt you'd be able to create an issue of cross chaining with a 3 cog cluster).

Does that fit the bill?


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