Hub drive with fluid clutch

[Robint]

Has anyone heard of this combination. Similar to what is used in auto xmissions. A fluid clutch can supply with up to 3x full speed torque at stall conditions. This would enable a hub motor to run up to full torque/speed with 3 fold output torque increase under start conditions. It needn't be considered inefficient under running conditions as it can incorporate a centrifugal "lock up" after suitable wheel revs are reached. It can also have a manual over-ride to lock up under slow speed conditions.

This can't be allowed to run under slip conditions for long as it would heat up the fluid (just like a mechanical clutch) but ok for starting bursts

Hmmmm?

 

[trex]

the NuVinci hub gear uses a similar concept.

 

[Robint]

the NuVinci hub gear uses a similar concept.

Ive just been reading about it, they don't say what the gear range is? Suspicious.

It is a mechanical rotating ball principle

Ive seen their website, bit coy on performance details torque speed ratio

relies on strong pressure between 2 rings and suitable viscous fluid, so they say

Efficiency??????????

 

[selrahc1992]

Ive just been reading about it, they don't say what the gear range is? Suspicious.

It is a mechanical rotating ball principle

Ive seen their website, bit coy on performance details torque speed ratio

relies on strong pressure between 2 rings and suitable viscous fluid, so they say

Efficiency??????????

I'm echoing what many have said here, but tried the nu-vinci a few months ago and it felt - to me - like treacle, really inefficient, my humming rohloff felt very free running afterwards

 

[Robint]

I'm echoing what many have said here, but tried the nu-vinci a few months ago and it felt - to me - like treacle, really inefficient, my humming rohloff felt very free running afterwards

Finally got a response out of 50C
they call it the i360 cos its reputed to have 360% gear range - so why didn't they say so up front?

Interesting your test results. WOW, last thing you want on a e bike is an inefficient drive. Users moan that the hub gear is less efficient than a chain derailleur 90% vs 98% under full load

I remember how bad those rim generators were on a push bike

I wonder if Khalkhoff will come clean on this

 

[trex]

...
Users moan that the hub gear is less efficient than a chain derailleur 90% vs 98% under full load
...

my experience with Shimano hub gears is that I can't tell the difference in efficiency between Shimano hubs and derailleurs, certainly much closer than 90 % vs 98%.

 

[Deleted member 4366]

I have a Nuvinci on one of my bikes. I can't say that I can feel any difference in efficiency. If there is a difference, it's small.

 

[Robint]

my experience with Shimano hub gears is that I can't tell the difference in efficiency between Shimano hubs and derailleurs, certainly much closer than 90 % vs 98%.

yup me too but Im not a power rider and we have some welly booted beasties on here that seem to destroy e-bikes 100+kgs and serious power

 

[anotherkiwi]

There is a Dutch or Belgian bloke/boffin who did the tests in his lab (sorry didn't mark the URL again...) and in order compared to a fixed gear:

Derailleur
Rohloff
Nexus 8 inter
Alfine and Nuvinci are the least efficient with losses of around 14%

That is testing on a machine, not the subjective feeling one might have riding.

 

[Deleted member 4366]

The problem with lab tests is that they give different results to what people experience in the real world because they don't tell the whole story. What's important is the overall system efficiency between the rider, bike and motor. What's important is how much effort the rider has to put in for any journey. The Nuvinci allows the rider always to operate at their optimum cadence so that the rider is being efficient. We know that a hub motor can operate at as low as 30% efficiency by going at the wrong speed. The same is true of the rider, so losing a few percentage points in the gear train can be insignificant.

 

[anotherkiwi]

Yes but... I remember you asking me why I wanted to use battery power to turn a hub dynamo... The raw numbers give us something to chew on that is not an up in the air "I feel drag, how much is there?"

I have just discovered for the first time in my life bike gear changers that work properly so for the moment I am happy to stick with a derailleur. I find amusing that Shimano's most expensive hub is less efficient than its entry model. I am not surprised by the performance of the Rohloff but I am that the Nexus Inter 8 is more efficient than the Rohloff is in its (inter 8's) direct drive gear! Is comfortable gear changing really worth a 14% loss in the gear box? On an e-bike why not, I'll ride in assistance level 3 instead of 2 and lose a little range. I certainly wouldn't want a Nuvinci on a bicycle! The Inter 8 however really attracted my attention.