Bottom Bracket Gears?

General cycling advice ( NOT technical ! )
Roadster
Posts: 443
Joined: 26 Jul 2016, 2:12pm
Location: E.Lancs/W.Yorks border

Re: Bottom Bracket Gears?

Postby Roadster » 10 Jan 2018, 5:51pm

ChrisF wrote:
mercalia wrote:wow 1800 euro for just the drive thats a lot of money: why did you get that rather than a Rohlof?

For the complete bike it wasn't much more than a comparable Rohloff machine. It also has a wider range, and the Rohloff couldn't give me both the high & low gears I wanted. As mentioned above, originally I planned for the P18 which is 630% think, so even greater range, but it costs more and weighs more.
Apart from that I think the Rohloff arrangements of gear-changing mechanism just looks messy!

The Pinion has two further advantages over the Rohloff and indeed all other IGHs: first, its central position means better weight distribution than the "rear-heavy" IGH; and second, rear wheel removal is easier without having to disturb the shift cable(s). Its main disadvantages are the requirement for a Pinion-specific frame and, for those with narrow hips, its greater Q-factor.

Tiberius
Posts: 391
Joined: 31 Dec 2014, 8:45am
Location: North East England

Re: Bottom Bracket Gears?

Postby Tiberius » 10 Jan 2018, 6:13pm

Roadster wrote:The Pinion has two further advantages over the Rohloff and indeed all other IGHs: first, its central position means better weight distribution than the "rear-heavy" IGH; and second, rear wheel removal is easier without having to disturb the shift cable(s). Its main disadvantages are the requirement for a Pinion-specific frame and, for those with narrow hips, its greater Q-factor.


I'm a Rohloff user, but I also have an open mind....

I like the idea of the Pinion gear box for the reasons that you have highlighted. I use a Rohloff for it's mega reliability (my perception and experience) Have you any idea how reliable the Pinion is ??....

Roadster
Posts: 443
Joined: 26 Jul 2016, 2:12pm
Location: E.Lancs/W.Yorks border

Re: Bottom Bracket Gears?

Postby Roadster » 10 Jan 2018, 6:27pm

I've never even seen let alone tried a Pinion-geared bike, Tiberius, and ride a steel-framed roadster with Alfine 8 IGH myself. I too like the idea, and my ultimate "dream bike" might well be a titanium framed, steel forked, chain driven and Pinion geared "Uber Roadster"...

brynpoeth
Posts: 5788
Joined: 30 Nov 2013, 11:26am

Re: Bottom Bracket Gears?

Postby brynpoeth » 10 Jan 2018, 8:07pm

Reliability figures for pinion will not be available for a few years, how many are in use?
Rohloff gears have been in service in large numbers for many years

No comparison possible!
Alternative facts welcome .. Cycling? Of course, but it is far better on a Gillott

BarryP
Posts: 4
Joined: 14 Jan 2010, 2:32pm

Re: Bottom Bracket Gears?

Postby BarryP » 16 Jan 2018, 10:45am

You're right about reliability figures but Pinion offer a 5 year guarantee so they've got to be pretty confident that the components will last far longer than that. My mate's got a Rohloff on his Fat Bike and it's been far from trouble free, mainly through water ingress. We'll see in 5 years time !

Roadster
Posts: 443
Joined: 26 Jul 2016, 2:12pm
Location: E.Lancs/W.Yorks border

Re: Bottom Bracket Gears?

Postby Roadster » 16 Jan 2018, 2:55pm

Looking at a single-speed bicycle and wondering where some variable gearing could be put, the hub of its rear wheel seems the least attractive option for several compelling reasons. The rear wheel is already burdened with most of the combined weight of bike and rider and tasked with not only propelling the machine forward but also retarding its progress when necessary.

These factors place greater demands on its axle, bearings, spokes and rim than is the case with the front wheel, yet still we are not satisfied with its workload but sadistically insist that it must accommodate multiple gears as well. Perhaps the time has finally come for the poor old much-abused rear wheel to be relieved of this last onerous task which so badly compromises its structural design, now that a more rational solution has become feasible.

Brucey
Posts: 29889
Joined: 4 Jan 2012, 6:25pm

Re: Bottom Bracket Gears?

Postby Brucey » 17 Jan 2018, 8:46am

fitting gearing into the BB seems appealing until you bother to do some sums. The fundamental issue is that gearboxes (of any given size/weight) die very quickly if they see too much torque. Because (in most applications) the wheel must turn about three or four times faster than the cranks, the most common torque loadings are about 1/3 or 1/4 if the gearbox is in the hub vs in the bottom bracket.

Thus it is no accident that the most common gear-based variable gearing system ( the 3s hub) lives in the rear wheel; to give the same gear ratios and net strength in a BB gear would require a bigger and/or heavier arrangement. The hub gear has other advantages too, for both manufacturers and user; the bike need not be designed around the gearing system per se and a replacement wheel is a viable repair or conversion for an owner.

However things are different if the gearing system is required to have some very low gears, e.g. with about a 1:1 ratio (crank rpm vs wheel rpm). This is obviously more likely to be the case if the wheel size is large and the road speed is low, so MTBs and touring bikes are likely to fall into this category. Then there is no advantage in terms of lower torque at the hub, and the gearbox weight isn't so likely to be very much different.

However the whole bike has to be increasingly designed around the gearbox, so the resultant machine becomes extremely focused.
In general the more gears you have in a gearbox, the larger fraction of the net cost of the machine is taken up in the gearbox, whether it is a frame mounted gearbox or an IGH. In extremis half or even three quarters of the cost of the whole machine might be tied up in the gearbox, and problems within it may be very expensive to resolve if not covered by a warranty.

There is of course lots of detail in terms of how the gearbox is configured internally. Planetary gear systems are attractive, in that there is only one (easily dealt with) reaction load that might have to be accommodated in a structure external to the gearbox internals. By contrast a layshaft gearbox (e.g. the Pinion) needs to sit inside a very stiff housing, because there are large reaction loads that are not self-contained within the moving parts.

The Pinion gearbox is (clutching aside) based on the same kind of technology that is used in a typical car gearbox. But, perhaps worryingly, layshaft gearboxes in cars and motorcycles are not especially noted for their high efficiency; losses of tens of percent are commonplace. Whether a modern BB gearbox is comparably efficient to an IGH remains to be seen; I've not seen any independent tests of this as yet. Personally I doubt that this will be the case, but it remains to be seen.

Note that whilst they are commonly layshaft or planetary depending on whether they are frame mounted or IGH gearboxes, this is not an exclusive arrangement; folk have used planetary gearing systems in frame-mounted arrangements, and in fact once you allow the structure to rotate you can use what is effectively a layshaft gearbox as a simplified, lopsided IGH. The Dursley Pedersen 3-speed hub (circa 100 years ago) was configured in this way; however this approach must have some kind of fundamental problems, because it has not been a route that has been used much since.

In terms of gear ratios, it is arguably easier to design a layshaft gearbox with relatively few stages and evenly spaced ratios than to use an IGH to do this, unless you add extra stages to the IGH. Both Alfine 11 and Rohloff hubs effectively use up to three planetary gear stages in series which makes some gear ratios noticeably less efficient than others. Neither IGH fully utilises the potential number of ratios, either; the Alfine 11 could have 12 ratios and the rohloff structure could similarly have 18 gears instead of 14. In both cases practical issues (shifting characteristics, gear ratio spacing) make the reduced ratio set a pragmatic choice.

In terms of net efficiency, this will also vary with duty cycle, so the average efficiency is weighted by the usage that each gears sees. In general if your duty cycle uses the 1:1 gear ratio in a gearbox much of the time, higher losses in other gears may be tolerable, because they don't affect the overall efficiency that much. This is basically how car gearboxes succeed despite relatively low efficiencies in many of the gears; if for much of the duty cycle, you trundle down the motorway in a high gear that is 1:1 inside the gearbox, losses are minimised.

A similar consideration applies to a lot of IGHs, eg 3s hubs, some 5s hubs, some 8s hubs, even the Rohloff hub; tapping along on the flat can be arranged to use the 1:1 ratio (or one close to it) which is intrinsically efficient, and this can occupy much of the duty cycle. I worked out that with a well-used 1:1 ratio, the average efficiency of some IGHs was lowered only by 1% (in my use) or so despite some gear ratios having losses of 15% or so. If efficiency is a concern, it makes sense to choose the gearing system to match the expected duty cycle.

It is also worth bearing in mind that all gearing systems (with very many ratios) work by multiplying one set of gears with another. Typically x2 or x3 is applied to a simpler system to give an increased range or more ratios. Obviously there is no necessity to have the whole gearing system based around any one technology, so for example you can have an IGH combined with a cassette, or an IGH combined with a simple derailleur system. Systems of this sort can be very flexibly configured and can offer a gear range, shifting characteristics, running costs and overall duty cycle efficiency that would not be possible using any single technology, and that can be matched to particular needs.

A good example is the 6s Brompton gearing; the machine needs a tensioner anyway, so adding a 2s derailleur has only a small impact on the machine, yet allows a reliable and simple IGH to yield six ratios instead of just three, still with high average efficiency. In operation it is still possible to do large block shifts when stationary, which is important for most users of this type of machine. It is likely that various different hybrid systems may offer the most cost-effective, efficient, and flexible solution for a lot of other applications too.

cheers
-------------------------------------------------------------------------------
~~~~~~~~~~~~~~~~~~~~~~Brucey~~~~~~~~~~~~~~~~~~~~~~~~

ChrisF
Posts: 269
Joined: 22 Mar 2014, 7:34pm

Re: Bottom Bracket Gears?

Postby ChrisF » 17 Jan 2018, 11:06pm

Brucey wrote: The fundamental issue is that gearboxes (of any given size/weight) die very quickly if they see too much torque. Because (in most applications) the wheel must turn about three or four times faster than the cranks, the most common torque loadings are about 1/3 or 1/4 if the gearbox is in the hub vs in the bottom bracket.

Brucey, I don't understand your point here. I agree that there's a difference in the torque on chainwheel and rear cog depending on IHG or BB gear (and the max force on the chain or belt), but surely for a given road speed the torque applied to the wheel itself (and thus the final pair of gears driving it) is gong to be the same? Or am I missing soemthing?
Brucey wrote:
Whether a modern BB gearbox is comparably efficient to an IGH remains to be seen; I've not seen any independent tests of this as yet.

Have a look here https://www.cyclingabout.com/speed-difference-testing-gearbox-systems/ for a comparison
Chris F, Cornwall

Brucey
Posts: 29889
Joined: 4 Jan 2012, 6:25pm

Re: Bottom Bracket Gears?

Postby Brucey » 18 Jan 2018, 1:11am

ChrisF wrote:
Brucey wrote: The fundamental issue is that gearboxes (of any given size/weight) die very quickly if they see too much torque. Because (in most applications) the wheel must turn about three or four times faster than the cranks, the most common torque loadings are about 1/3 or 1/4 if the gearbox is in the hub vs in the bottom bracket.

Brucey, I don't understand your point here. I agree that there's a difference in the torque on chainwheel and rear cog depending on IHG or BB gear (and the max force on the chain or belt), but surely for a given road speed the torque applied to the wheel itself (and thus the final pair of gears driving it) is gong to be the same? Or am I missing soemthing?


the torque at the wheel is obviously going to be the same, but the torque at the pedals is in inverse proportion to the speed at which they go round. [torque x rpms = power] Thus if the wheel is turning x4 time faster than the cranks, the torque at the cranks is x4 greater than the torque at the wheel. Thus a BB gearbox has to see much higher torque values than the wheel on most bikes when 'normal' gear ratios are used.

Only when the cranks and wheel are turning at the same speed are the torque values at wheel and crank the same; this does happen if you have very low gears fitted.

Thanks for the link to the efficiency test summary. This graph
Image
contains a lot of Oehler's old data, plus some newer data concerning the Pinion P18 gearbox.
This graph presents the other (old) data along with NuVinci data (from 2008)
Image

In the link the average test results (@200W 60rpm cadence) are summarised thus
Singlespeed: 97% efficient (Drivetrain loss of 6w @ 200w).
Rohloff : 94.5% efficient on average across 14 gears (Drivetrain loss of 11w @ 200w)
Pinion: 90.5% efficient on average across 18 gears (Drivetrain loss of 19w @ 200w).
Shimano Alfine 11: 90.5% efficient on average across 11 gears (Drivetrain loss of 19w @ 200w).
Shimano Nexus 8: 90% efficient on average across 8 gears (Drivetrain loss of 20w @ 200w).
Nuvinci 360: 83.5% efficient on average across the gear range (Drivetrain loss of 33w @ 200w).


The Inter-8 they tested is, I think, an old model without roller bearings on the pinions. I'd expect newer model Nexus 8 premium hubs and alfine 8 to be much more efficient in 4th gear etc. The average efficiency of an A8/Premium N8 is likely to be close to that of the rohloff, in fact.

Note also that the 'average efficiency' is a simple arithmetic mean; if the duty cycle varies from this assumed 'even usage' (and it probably will) then transmissions with lumpy graphs will either do better or worse than the average value suggests.

The Pinion P18 is actually slightly better on test than I had expected; even so you are giving away four or five percent to a Rohloff hub.

cheers
-------------------------------------------------------------------------------
~~~~~~~~~~~~~~~~~~~~~~Brucey~~~~~~~~~~~~~~~~~~~~~~~~

Mountgrove
Posts: 6
Joined: 8 May 2018, 12:35pm

Re: Bottom Bracket Gears?

Postby Mountgrove » 8 May 2018, 1:09pm

Hi apologies for "resurrecting" this topic. I am a newbie.
I am in search of a Pinion bike in the UK. Preferably a "mass produced" option.
Is there a retailer or outlet in the UK that offers any bike (or ebike) with a Pinion gear box?
I like the look of this german model.

raleigh rush hour 2018 https://www.youtube.com/watch?v=5xYkJvQtGM0

However the above Raleigh bike is not advertised for sale on Raleigh UK . I have phoned Raleigh in the UK to see if there are plans to bring it on to the UK market.
(What would be the implications for warranty if purcahsed in Germany and serviced in the UK?)

There are also Kalkhoff (ebike and non ebike) options available with Pinion : Kalkhoff Endeavour P18 Pinon Trekking Bike
Also Van Nicholas Deveron - Pinion & Titanium Touring Bicycle.
Stevens P18 Belt Drive Bike .
Any ideas where in the UK to try out one of these ?
My setup would be for touring and also day to day commuting.
(I carry a lot to work and back - laptop etc).
So I am researching a one size fits all option. (if no expense spared I would have a pinion gearbox with wide range of gearing, gates drive belt and disk brakes, front and rear pannier and lights ) .
Is there likely to be a cycle show in the Midlands (NEC?) that would have something on demo ?

From my research the Pinion is very low maintenance and the bottom bracket gearbox gives the bike much better handling ?
I would not be doing much off road so I would only require front suspension and possibly a cane creek seatpost .

I am what you might call a "slower" rider - at the moment I use a ebike for most commuting so I will not be setting any speed or distance records any time soon !
Any thoughts ?

ChrisF
Posts: 269
Joined: 22 Mar 2014, 7:34pm

Re: Bottom Bracket Gears?

Postby ChrisF » 12 May 2018, 6:01pm

Hi, I have a Pinion C12 for sale; I sent you a personal message the other day, not sure if you get a notification about this.
Chris F, Cornwall

brynpoeth
Posts: 5788
Joined: 30 Nov 2013, 11:26am

Re: Bottom Bracket Gears?

Postby brynpoeth » 12 May 2018, 6:06pm

ChrisF wrote:Hi, I have a Pinion C12 for sale; I sent you a personal message the other day, not sure if you get a notification about this.

Would you like to post pictures + info here?
Why do you want to sell it?
Alternative facts welcome .. Cycling? Of course, but it is far better on a Gillott

ChrisF
Posts: 269
Joined: 22 Mar 2014, 7:34pm

Re: Bottom Bracket Gears?

Postby ChrisF » 12 May 2018, 6:22pm

brynpoeth wrote:Would you like to post pictures + info here?

I'd forgotten there was a 'For Sale' section - good idea, I'll put it up there shortly. Thanks.
Chris F, Cornwall

elduderino
Posts: 8
Joined: 2 Jun 2016, 6:25pm

Re: Bottom Bracket Gears?

Postby elduderino » 17 May 2018, 7:14am

Mountgrove wrote:Hi apologies for "resurrecting" this topic. I am a newbie.
I am in search of a Pinion bike in the UK. Preferably a "mass produced" option.
Is there a retailer or outlet in the UK that offers any bike (or ebike) with a Pinion gear box?
I like the look of this german model.

raleigh rush hour 2018 https://www.youtube.com/watch?v=5xYkJvQtGM0

However the above Raleigh bike is not advertised for sale on Raleigh UK . I have phoned Raleigh in the UK to see if there are plans to bring it on to the UK market.
(What would be the implications for warranty if purcahsed in Germany and serviced in the UK?)

There are also Kalkhoff (ebike and non ebike) options available with Pinion : Kalkhoff Endeavour P18 Pinon Trekking Bike
Also Van Nicholas Deveron - Pinion & Titanium Touring Bicycle.
Stevens P18 Belt Drive Bike .
Any ideas where in the UK to try out one of these ?
My setup would be for touring and also day to day commuting.
(I carry a lot to work and back - laptop etc).
So I am researching a one size fits all option. (if no expense spared I would have a pinion gearbox with wide range of gearing, gates drive belt and disk brakes, front and rear pannier and lights ) .
Is there likely to be a cycle show in the Midlands (NEC?) that would have something on demo ?

From my research the Pinion is very low maintenance and the bottom bracket gearbox gives the bike much better handling ?
I would not be doing much off road so I would only require front suspension and possibly a cane creek seatpost .

I am what you might call a "slower" rider - at the moment I use a ebike for most commuting so I will not be setting any speed or distance records any time soon !
Any thoughts ?


I purchased a Kalkhoff P18 through 50cycles in Loughborough.
I replaced the handlebars & headstem ( I prefer sitting upright on a bike). Replaced the seat post with a suntour cam action seatpost, & my most comfortable Brooks B67 saddle .
Replaced the tyres with my schwalbe Marathon plus tour’s
My average speed is 11mph , & it’s the most enjoyable cycle riding I have ever had, & can’t wait to jump on the thing.

gregoryoftours
Posts: 746
Joined: 22 May 2011, 7:14pm

Re: Bottom Bracket Gears?

Postby gregoryoftours » 29 May 2018, 12:28am

Also this, which is non strictly BB gears either.
https://www.bikeradar.com/gear/category ... set-35140/