Powershift rear hub gear - tempted?

For discussions about bikes and equipment.
rareposter
Posts: 1988
Joined: 27 Aug 2014, 2:40pm

Re: Powershift rear hub gear - tempted?

Post by rareposter »

boblo wrote: 4 Dec 2022, 4:50pm I don't use Di2 and show your workings if you think a 500g hub weighs less than a front der/conventional rear hub mechanical set up. It'll also need some form of power unless they've solved electrical alchemy at the same time...

Just saying it, doesn't make it so...
You've removed the weight of a front mech and a chainring plus the chain can be shorter. The Classified cassette is also lighter than a Dura Ace one so there's some weight loss there too. And it's not me saying it, it's in the reviews.

I also didn't say it didn't need any power, I actually can't see what the power source is - there's nothing in the reviews I've seen of it to explain that. I'm assuming a coin cell battery in the wireless shifter.
esasjl
Posts: 55
Joined: 18 Feb 2021, 9:02pm

Re: Powershift rear hub gear - tempted?

Post by esasjl »

I'm confused by the 'no cross-chaining' claim, seems the only way to avoid this is a single sprocket and single chainring?
slowster
Moderator
Posts: 4629
Joined: 7 Jul 2017, 10:37am

Re: Powershift rear hub gear - tempted?

Post by slowster »

rareposter wrote: 4 Dec 2022, 4:58pm the chain can be shorter
No, it can't.
boblo
Posts: 799
Joined: 24 Sep 2009, 7:35pm

Re: Powershift rear hub gear - tempted?

Post by boblo »

You've removed the weight of a front mech and a chainring plus the chain can be shorter. The Classified cassette is also lighter than a Dura Ace one so there's some weight loss there too. And it's not me saying it, it's in the reviews.
You're right - in part. I included the weight of the front der and a 'mid range' rear hub (Ultegra) but forgot about the cable and chainring. The cassettes look similar to SRAM's XG range as in milled from solid. I bought one for lightness, they are now over £300! Not sure if the Powershift ones are available ATM and at what cost.

I stand corrected on the system weight, it looks like it might come out very similar. I'll maintain my luddite churlishness ( :D ) on electrickery, cost and all the weight being concentrated around the rear axle. I had a Shimano 8 speed IHG at one point and it felt horrible to ride partly because of this.

I know we do this every so often with new stuff. All the gear freak early adopters are wetting themselves over shiny new things and all the grumpy gits (me) are rolling their eyes and sucking their teeth.

For the record, click shift (now STI) and 11 speed have been brilliant for road cycling and click shift and anything at 9 speed the same for touring and MTB. I embrace it, just not slavishly. I recently built a new dedicated tourer (my old one was flattened in a road accident) and used 3x9 as the 'best' option (for my application) and have yet to enter the Di2 game as I don't see a compelling need (for me).
PH
Posts: 13106
Joined: 21 Jan 2007, 12:31am
Location: Derby
Contact:

Re: Powershift rear hub gear - tempted?

Post by PH »

slowster wrote: 4 Dec 2022, 5:25pm
rareposter wrote: 4 Dec 2022, 4:58pm the chain can be shorter
No, it can't.
Yes, no, maybe...
If you need less capacity, then there's less slack to take up, so if there's a suitable shorter derailleur, then there's a weight saving both on that and the shorter chain it'll require.
brumster
Posts: 510
Joined: 8 Sep 2009, 7:50pm

Re: Powershift rear hub gear - tempted?

Post by brumster »

All this tech is fine until it stops working and you can't fix it at the side of the road.
slowster
Moderator
Posts: 4629
Joined: 7 Jul 2017, 10:37am

Re: Powershift rear hub gear - tempted?

Post by slowster »

PH wrote: 4 Dec 2022, 5:47pm
slowster wrote: 4 Dec 2022, 5:25pm
rareposter wrote: 4 Dec 2022, 4:58pm the chain can be shorter
No, it can't.
Yes, no, maybe...
If you need less capacity, then there's less slack to take up, so if there's a suitable shorter derailleur, then there's a weight saving both on that and the shorter chain it'll require.
Chains are sized on the big/big chainring/sprocket combination plus one link, regardless of the derailleur jockey arm length. I think the potential weight saving of a shorter jockey arm would be negligible, given that they are made of aluminium or carbon fibre.
cycle tramp
Posts: 3531
Joined: 5 Aug 2009, 7:22pm

Re: Powershift rear hub gear - tempted?

Post by cycle tramp »

..not really, no...
Motorhead: god was never on your sidehttps://www.google.com/search?ie=UTF-8&client=m ... +your+side
rjb
Posts: 7200
Joined: 11 Jan 2007, 10:25am
Location: Somerset (originally 60/70's Plymouth)

Re: Powershift rear hub gear - tempted?

Post by rjb »

brumster wrote: 4 Dec 2022, 5:56pm All this tech is fine until it stops working and you can't fix it at the side of the road.
It's just like a freewheel. When the pawl springs fail you just bounce your carbon rimmed wheel on the road until one of the pawls engages then ride home without freewheeling. :lol:
At the last count:- Peugeot 531 pro, Dawes Discovery Tandem, Dawes Kingpin X3, Raleigh 20 stowaway, 1965 Moulton deluxe, Falcon K2 MTB dropped bar tourer, Rudge Bi frame folder, Longstaff trike conversion on a Giant XTC 840 :D
rareposter
Posts: 1988
Joined: 27 Aug 2014, 2:40pm

Re: Powershift rear hub gear - tempted?

Post by rareposter »

slowster wrote: 4 Dec 2022, 5:25pm
rareposter wrote: 4 Dec 2022, 4:58pm the chain can be shorter
No, it can't.
Yeah, you're right, apologies, I was thinking the other way around (keep small ring, ditch the big) but it is of course keeping the big ring. My mistake.
brumster wrote: 4 Dec 2022, 5:56pm All this tech is fine until it stops working and you can't fix it at the side of the road.
Why would it go wrong? What is there to go wrong? No cable to snap or seize. The hub, as pointed out above, is not really any different to the old Sachs 2x7 - it's a planetary gear system, the same as on Rohloff (which everyone raves about for their reliability). Electronic shifting has far fewer moving parts than mechanical, it's no different to a light switch in a house really.
slowster
Moderator
Posts: 4629
Joined: 7 Jul 2017, 10:37am

Re: Powershift rear hub gear - tempted?

Post by slowster »

From the maufacturer's website:
How efficient is the hub?

Very efficient! More efficient than a 1x setup and as efficient as a 2x setup. Compared to a 1x, less cross chaining is required, sprocket and chainring sizes are larger and thus chain tension, crank and hub bearing losses are lower. Compared to a 2x; the fact that the 0.7 ratio of the hub still uses the large chainring in front, results in 30% less chain tension and thus lower chain, crank and hub bearing losses. On top of this you will experience that you will use the Classified hub much more frequent than a normal front derailleur, this means that in practice you will have less cross chain losses. The hub does not have any additional losses on in the 1:1 ratio, and is designed to have extremely low losses in the 0.7 ratio which are completely balanced out by the big chainring and straighter chainline by using a Classified setup.
That looks to me like cod-science which is deliberately intended to deceive. Note the difference between:

"The hub does not have any additional losses on in the 1:1 ratio"

"is designed to have extremely low losses in the 0.7 ratio which are completely balanced out by the big chainring and straighter chainline"

Similarly, "30% less chain tension and thus lower chain, crank and hub bearing losses" sounds great, but is meaningless without knowing the amount of Watts which those losses involve and their overall significance.

"in practice you will have less cross chain losses" - I suspect that there may be less cross chain losses *averaged* over the course of some routes, depending upon how hilly/mountainous the terrain is.

There is no substitute for rigorous scientific measurement of the comparative losses, and that is conspicuously missing from the marketing.
rogerzilla
Posts: 2887
Joined: 9 Jun 2008, 8:06pm

Re: Powershift rear hub gear - tempted?

Post by rogerzilla »

A single epicyclic geartrain with well-sized pinion gears loses about 3% (measurements of a well run-in, oil-lubricated Sturmey-Archer AW in top gear agree with this).

So "extremely low" is at least 3%, probably worse if grease-lubricated. Assuming a sporty power input of 200W, that's 6W, like a 50% efficient hub dynamo with the lights on.
rareposter
Posts: 1988
Joined: 27 Aug 2014, 2:40pm

Re: Powershift rear hub gear - tempted?

Post by rareposter »

GCN video of it here:

https://youtu.be/UFMhUYoqFyc

The efficiency is reckoned on being little different to a regular 2x setup. Certainly all the reviews have said it's pretty much undetectable in use.
zenitb
Posts: 832
Joined: 7 Aug 2018, 9:59pm
Contact:

Re: Powershift rear hub gear - tempted?

Post by zenitb »

Cugel wrote: 4 Dec 2022, 9:58am It seems that some big capitalist has decided to have faith in this new way of establishing a double clanger gear system -

Cugel
Bonjour Cudgel..

Are they trying to relaunch this? We have already THOROUGHLY RINSED this product 18 months ago 😀 😉

I posted it up originally and it triggered a bit of a feeding frenzy with posters rightly ridiculing the thing.

The fact the product has got nowhere in the intervening 18 months tells you all you need to know.

Also the fact that GCN etc are still pushing it doesn't surprise me..time for them to consider real cyclists...

viewtopic.php?t=145707&hilit=Zenitb+%26 ... %26quot%3B
rareposter
Posts: 1988
Joined: 27 Aug 2014, 2:40pm

Re: Powershift rear hub gear - tempted?

Post by rareposter »

zenitb wrote: 5 Dec 2022, 12:10pm
The fact the product has got nowhere in the intervening 18 months tells you all you need to know.
It tells me they've spent some time perfecting the design, working with other wheel manufacturers to offer some choices of wheel to broaden the appeal and got some investment on board to enable a proper release. But then I've worked in an industry where 8+ years is normal for a project to go from drawing board to fruition...
zenitb wrote: 5 Dec 2022, 12:10pm Also the fact that GCN etc are still pushing it doesn't surprise me..time for them to consider real cyclists...
What's a "real cyclist" please? Do I have to have ridden a solo LEJOG on a 1980's steel touring bike to qualify? Maybe I need some plus-fours and a Carradice saddle bag? Or perhaps I have to commute on a Moulton?
Would be fascinated to know...
Post Reply