2013-11-21, 18:18
The following post is an entire topic copied from the discontinued NuVinci Forum. The majority is written by members of the old forum and not by me.
Wheel not spinning freely
by bouldermain on Sat Feb 09, 2013 1:34 pm
Hello.
I've got about 250 miles on my N360, which drives the rear wheel of my Terratrike Rover. The front gear is 32-cog and the rear is 17 (about a 1.9 ratio).
Yesterday, I noticed that the rear wheel doesn't spin freely. I can get it going pretty fast on a bike stand, with the N360 in the highest gear, and when I stop turning the pedal, the wheel spins down to a stop in about six seconds rather than freely spinning. I don't know whether this has been a problem for the entire time I've had the N360, or whether the problem developed recently. The weather has been cold lately (near freezing in the workshop this morning), but I don't know if that would have an effect. I don't see any rubbing on the wheel or tire (nothing to slow it down except friction in the N360). Any ideas on what might be causing the problem? Thanks!
all good things,
Michael
Re: Wheel not spinning freely
by Oran on Sat Feb 09, 2013 7:16 pm
Hi Michael,
This is normal for an N360 and is due to the seals that retain the traction fluid. The amount of drag varies between hubs and may reduce as you do more miles. The drag will appear to stop the wheel quite quickly but the power loss is only a few watts and not noticeable when you ride the bike.
Hub resistance varies greatly
by FransM on Wed Apr 11, 2012 7:28 am
I have received a number of hubs and found that when trying to turn the axle by hand some hubs have much more resistance than others.
I've done some testing with different gearing and found the following:
All 4 hubs require 0.11 Nm torque to turn the axle in the 1:1 ratio (middle) position.
In low gear they require twice the torque
In high gear 2 (good) hubs require 1.5 times as much
the 2 other (bad) hubs require 3-3.5 times as much (this feels very sticky, it can hardly be turned by hand without tools)
For completeness sake, although not very relevant in daily practice, I also measured the resistance in reverse direction:
The good hubs require 0.11 Nm torque in the 1:1 ratio;
in low gear 3.5-4 times as much
in high gear 1.5 as much
One of the bad hubs also 0.11 Nm in the middle position, the other 6 times as much (!)
in low gear 5-6 (!) as much
in high gear twice as much
As can be seen, the resistance varies according to chosen gear, but also between different hubs, and in one instance - the bad hub in reverse direction - there is a sudden great increase in resistance in the middle position which feels rubbery (a seal?).
What could be the explanation of these results?
I think that the resistance in the bad hubs is too much and will have a considerable effect on the efficiency.
Re: Hub resistance varies greatly
by NuVinciSupport on Wed Apr 11, 2012 10:36 am
I will try to get a more specific answer for you, but in the meantime, the sticky hubs typically become "un-sticky" after a minor break in period. Not sure if there is something technical there or not, but they do break in after a few good rides on them.
Keep On Smooth Cruising
NuVinci Support
Re: Hub resistance varies greatly
by FransM on Wed Apr 11, 2012 10:50 am
I forgot to mention that I had a hub replaced in the past which was very sticky and remained so even after about 500 km's.
Re: Hub resistance varies greatly
by NuVinciSupport on Thu Apr 12, 2012 4:13 pm
What you are experiencing is common to sealed internal hubs, and is primarily the small amount of resistance due to seals against their mating components. This resistance often decreases with use because fluid will lubricate a portion of the sealing surfaces, and the seals and the mating components will settle into an optimized alignment with use.
As for the torque numbers you were measuring, these will feel high to “fingers”, but typically do not increase with additional torque. As an example, if a rider is putting 50 Nm of torque into the CVP with their legs, your highest measured torque of 0.66Nm of seal resistance is only around 1%. So while your fingers will feel this as a large resistance, your legs likely will not!
Finally, the N360 does use rider torque somewhat in the shifting process, and finger torque may not be enough to properly shift the system completely into its true operating state…which may also cause additional resistance.
Keep On Smooth Cruising
NuVinci Support
Re: Hub resistance varies greatly
by FransM on Fri Apr 13, 2012 4:43 am
Thank you for your answer.
If the typical torque put on the hub is 50Nm, then you're right that the torque I measured is negligable.
Wheel not spinning freely
by bouldermain on Sat Feb 09, 2013 1:34 pm
Hello.
I've got about 250 miles on my N360, which drives the rear wheel of my Terratrike Rover. The front gear is 32-cog and the rear is 17 (about a 1.9 ratio).
Yesterday, I noticed that the rear wheel doesn't spin freely. I can get it going pretty fast on a bike stand, with the N360 in the highest gear, and when I stop turning the pedal, the wheel spins down to a stop in about six seconds rather than freely spinning. I don't know whether this has been a problem for the entire time I've had the N360, or whether the problem developed recently. The weather has been cold lately (near freezing in the workshop this morning), but I don't know if that would have an effect. I don't see any rubbing on the wheel or tire (nothing to slow it down except friction in the N360). Any ideas on what might be causing the problem? Thanks!
all good things,
Michael
Re: Wheel not spinning freely
by Oran on Sat Feb 09, 2013 7:16 pm
Hi Michael,
This is normal for an N360 and is due to the seals that retain the traction fluid. The amount of drag varies between hubs and may reduce as you do more miles. The drag will appear to stop the wheel quite quickly but the power loss is only a few watts and not noticeable when you ride the bike.
Hub resistance varies greatly
by FransM on Wed Apr 11, 2012 7:28 am
I have received a number of hubs and found that when trying to turn the axle by hand some hubs have much more resistance than others.
I've done some testing with different gearing and found the following:
All 4 hubs require 0.11 Nm torque to turn the axle in the 1:1 ratio (middle) position.
In low gear they require twice the torque
In high gear 2 (good) hubs require 1.5 times as much
the 2 other (bad) hubs require 3-3.5 times as much (this feels very sticky, it can hardly be turned by hand without tools)
For completeness sake, although not very relevant in daily practice, I also measured the resistance in reverse direction:
The good hubs require 0.11 Nm torque in the 1:1 ratio;
in low gear 3.5-4 times as much
in high gear 1.5 as much
One of the bad hubs also 0.11 Nm in the middle position, the other 6 times as much (!)
in low gear 5-6 (!) as much
in high gear twice as much
As can be seen, the resistance varies according to chosen gear, but also between different hubs, and in one instance - the bad hub in reverse direction - there is a sudden great increase in resistance in the middle position which feels rubbery (a seal?).
What could be the explanation of these results?
I think that the resistance in the bad hubs is too much and will have a considerable effect on the efficiency.
Re: Hub resistance varies greatly
by NuVinciSupport on Wed Apr 11, 2012 10:36 am
I will try to get a more specific answer for you, but in the meantime, the sticky hubs typically become "un-sticky" after a minor break in period. Not sure if there is something technical there or not, but they do break in after a few good rides on them.
Keep On Smooth Cruising
NuVinci Support
Re: Hub resistance varies greatly
by FransM on Wed Apr 11, 2012 10:50 am
I forgot to mention that I had a hub replaced in the past which was very sticky and remained so even after about 500 km's.
Re: Hub resistance varies greatly
by NuVinciSupport on Thu Apr 12, 2012 4:13 pm
What you are experiencing is common to sealed internal hubs, and is primarily the small amount of resistance due to seals against their mating components. This resistance often decreases with use because fluid will lubricate a portion of the sealing surfaces, and the seals and the mating components will settle into an optimized alignment with use.
As for the torque numbers you were measuring, these will feel high to “fingers”, but typically do not increase with additional torque. As an example, if a rider is putting 50 Nm of torque into the CVP with their legs, your highest measured torque of 0.66Nm of seal resistance is only around 1%. So while your fingers will feel this as a large resistance, your legs likely will not!
Finally, the N360 does use rider torque somewhat in the shifting process, and finger torque may not be enough to properly shift the system completely into its true operating state…which may also cause additional resistance.
Keep On Smooth Cruising
NuVinci Support
Re: Hub resistance varies greatly
by FransM on Fri Apr 13, 2012 4:43 am
Thank you for your answer.
If the typical torque put on the hub is 50Nm, then you're right that the torque I measured is negligable.
- Oran