Small derailleur sprockets

Does anyone know of an engineering or experimental reference to
how the rate of wear of a sprocket varies with number of teeth?
All of Renolds, Rexnord and Diamond strongly disrecommend below
13 teeth, and advise more, but the reason is irregularity of
speed, not rate of wear.

My experience from a long time back with hub gears is that it is
highly non-linear once you get below (say) 16 teeth.


Regards,
Nick Maclaren.

On Fri, 20 Feb 2015 12:31:48 +0000 (GMT),
(Nick Maclaren) wrote:


Does anyone know of an engineering or experimental reference to
how the rate of wear of a sprocket varies with number of teeth?
All of Renolds, Rexnord and Diamond strongly disrecommend below
13 teeth, and advise more, but the reason is irregularity of
speed, not rate of wear.

My experience from a long time back with hub gears is that it is
highly non-linear once you get below (say) 16 teeth.


Regards,
Nick Maclaren.

I took a quick look and there apparently is a correlation between
sprocket size and wear although I didn't find a specific calculation I
did find a reference that in a low ratio chain drive the total number
of drive and driven teeth, for best longevity, should not be less
than 50, i.e., a 25 tooth driver and a 25 tooth driven which seems to
be indicative.
--
Cheers,

John B.

On 2/20/2015 7:31 AM, Nick Maclaren wrote:
Does anyone know of an engineering or experimental reference to
how the rate of wear of a sprocket varies with number of teeth?
All of Renolds, Rexnord and Diamond strongly disrecommend below
13 teeth, and advise more, but the reason is irregularity of
speed, not rate of wear.

My experience from a long time back with hub gears is that it is
highly non-linear once you get below (say) 16 teeth.

I don't know of any engineering reference regarding sprocket wear vs.
tooth count. Yes, the main reason typical engineering situations avoid
low tooth counts is probably irregular speed. IOW, the angular velocity
varies more through the passage time of each tooth (assuming constant
chain velocity), since the effective radius is greatest with the pin at
right angles to the chain line, and least with the tooth itself at right
angles.

I'm not surprised that the effect of low tooth count on wear would be
non-linear. By lowering tooth count, you're simultaneously increasing
chain tension necessary for a certain drive torque, and also increasing
the frequency with which each tooth bears the maximum load. And I
suppose even the tendency toward rougher angular velocity would have an
effect.

But again, I don't know of a reference that quantifies this.

--
- Frank Krygowski

In article ,
John B. Slocomb wrote:

Does anyone know of an engineering or experimental reference to
how the rate of wear of a sprocket varies with number of teeth?
All of Renolds, Rexnord and Diamond strongly disrecommend below
13 teeth, and advise more, but the reason is irregularity of
speed, not rate of wear.

My experience from a long time back with hub gears is that it is
highly non-linear once you get below (say) 16 teeth.

I took a quick look and there apparently is a correlation between
sprocket size and wear although I didn't find a specific calculation I
did find a reference that in a low ratio chain drive the total number
of drive and driven teeth, for best longevity, should not be less
than 50, i.e., a 25 tooth driver and a 25 tooth driven which seems to
be indicative.

Thanks. This could be another of the important aspects of cycling
that is ignored because it isn't important to UCI racing :-(


Regards,
Nick Maclaren.

On Sat, 21 Feb 2015 09:58:47 +0000 (GMT),
(Nick Maclaren) wrote:

In article ,
John B. Slocomb wrote:

Does anyone know of an engineering or experimental reference to
how the rate of wear of a sprocket varies with number of teeth?
All of Renolds, Rexnord and Diamond strongly disrecommend below
13 teeth, and advise more, but the reason is irregularity of
speed, not rate of wear.

My experience from a long time back with hub gears is that it is
highly non-linear once you get below (say) 16 teeth.

I took a quick look and there apparently is a correlation between
sprocket size and wear although I didn't find a specific calculation I
did find a reference that in a low ratio chain drive the total number
of drive and driven teeth, for best longevity, should not be less
than 50, i.e., a 25 tooth driver and a 25 tooth driven which seems to
be indicative.

Thanks. This could be another of the important aspects of cycling
that is ignored because it isn't important to UCI racing :-(


Regards,
Nick Maclaren.


I suspect that in terms of a bicycle it isn't overly important, or
perhaps not easily corrected. A 25 tooth rear sprocket would require a
113 tooth front sprocket to match the usual 50/11 road gearing.

After all, a full, oil bath, chain cover would increase chain life by
years and even a simple oil less cover will do wonders for chain life
but I can't remember ever seeing a recreational cyclist with one.
--
Cheers,

John B.

In article ,
John B. Slocomb wrote:

Does anyone know of an engineering or experimental reference to
how the rate of wear of a sprocket varies with number of teeth?
All of Renolds, Rexnord and Diamond strongly disrecommend below
13 teeth, and advise more, but the reason is irregularity of
speed, not rate of wear.

My experience from a long time back with hub gears is that it is
highly non-linear once you get below (say) 16 teeth.

I took a quick look and there apparently is a correlation between
sprocket size and wear although I didn't find a specific calculation I
did find a reference that in a low ratio chain drive the total number
of drive and driven teeth, for best longevity, should not be less
than 50, i.e., a 25 tooth driver and a 25 tooth driven which seems to
be indicative.

Thanks. This could be another of the important aspects of cycling
that is ignored because it isn't important to UCI racing :-(

I suspect that in terms of a bicycle it isn't overly important, or
perhaps not easily corrected. A 25 tooth rear sprocket would require a
113 tooth front sprocket to match the usual 50/11 road gearing.

Oh, it's important, all right! Derailleurs are chain and sprocket
eaters, at best (fixed and hub gears have a VASTLY higher distance
between maintenance, and even more between replacement). But many
vendors like selling short-life equipment, because they make their
profit on the replacements.

It's soluble only by using hub gears or by even more drastic
measures.


Regards,
Nick Maclaren.

On Saturday, February 21, 2015 at 5:30:27 AM UTC-6, Nick Maclaren wrote:
In article ,
John B. Slocomb wrote:

Does anyone know of an engineering or experimental reference to
how the rate of wear of a sprocket varies with number of teeth?
All of Renolds, Rexnord and Diamond strongly disrecommend below
13 teeth, and advise more, but the reason is irregularity of
speed, not rate of wear.

My experience from a long time back with hub gears is that it is
highly non-linear once you get below (say) 16 teeth.

I took a quick look and there apparently is a correlation between
sprocket size and wear although I didn't find a specific calculation I
did find a reference that in a low ratio chain drive the total number
of drive and driven teeth, for best longevity, should not be less
than 50, i.e., a 25 tooth driver and a 25 tooth driven which seems to
be indicative.

Thanks. This could be another of the important aspects of cycling
that is ignored because it isn't important to UCI racing :-(

I suspect that in terms of a bicycle it isn't overly important, or
perhaps not easily corrected. A 25 tooth rear sprocket would require a
113 tooth front sprocket to match the usual 50/11 road gearing.

Oh, it's important, all right! Derailleurs are chain and sprocket
eaters, at best (fixed and hub gears have a VASTLY higher distance
between maintenance, and even more between replacement). But many
vendors like selling short-life equipment, because they make their
profit on the replacements.

It's soluble only by using hub gears or by even more drastic
measures.


Regards,
Nick Maclaren.

The main determinant is pressure per area. Once you exceed the material strength of the parts, it starts wearing quickly.

Single speed / hub gears use wider chains with more area. 5-7 freewheels are almost as good. 7-11 cassettes get thinner and thinner and wear much more quickly.

Dirt causes wear because it causes all the pressure to be against the piece of dirt instead of the entire surface area.

On 2015-02-21 11:30:25 +0000, Nick Maclaren said:

In article ,
John B. Slocomb wrote:

Does anyone know of an engineering or experimental reference to
how the rate of wear of a sprocket varies with number of teeth?
All of Renolds, Rexnord and Diamond strongly disrecommend below
13 teeth, and advise more, but the reason is irregularity of
speed, not rate of wear.

My experience from a long time back with hub gears is that it is
highly non-linear once you get below (say) 16 teeth.

I took a quick look and there apparently is a correlation between
sprocket size and wear although I didn't find a specific calculation I
did find a reference that in a low ratio chain drive the total number
of drive and driven teeth, for best longevity, should not be less
than 50, i.e., a 25 tooth driver and a 25 tooth driven which seems to
be indicative.

Thanks. This could be another of the important aspects of cycling
that is ignored because it isn't important to UCI racing :-(

I suspect that in terms of a bicycle it isn't overly important, or
perhaps not easily corrected. A 25 tooth rear sprocket would require a
113 tooth front sprocket to match the usual 50/11 road gearing.

Oh, it's important, all right! Derailleurs are chain and sprocket
eaters, at best (fixed and hub gears have a VASTLY higher distance
between maintenance, and even more between replacement). But many
vendors like selling short-life equipment, because they make their
profit on the replacements.

My experience on my singlespeed and Rohloff hubbed bikes is that the
chains and sprockets don't last longer that the chains and cassettes on
my derailleur equipped bikes. It is true that you can ride longer with
a worn chain and sprocket without getting into trouble. The sprocket on
my Rohloff ATB lasted 1500 km. When I replaced the chain the new chain
made a terrible noise. I reversed the sprocket and the noise was gone.
1500 km is a pathetic mileage even for a ATB used mostly in dirty
conditions. The same goes for my singlespeed.


It's soluble only by using hub gears or by even more drastic
measures.

Not in my case.

--

Lou

Lou Holtman formulated the question :
On 2015-02-21 11:30:25 +0000, Nick Maclaren said:

In article ,
John B. Slocomb wrote:

Does anyone know of an engineering or experimental reference to
how the rate of wear of a sprocket varies with number of teeth?
All of Renolds, Rexnord and Diamond strongly disrecommend below
13 teeth, and advise more, but the reason is irregularity of
speed, not rate of wear.

My experience from a long time back with hub gears is that it is
highly non-linear once you get below (say) 16 teeth.

I took a quick look and there apparently is a correlation between
sprocket size and wear although I didn't find a specific calculation I
did find a reference that in a low ratio chain drive the total number
of drive and driven teeth, for best longevity, should not be less
than 50, i.e., a 25 tooth driver and a 25 tooth driven which seems to
be indicative.

Thanks. This could be another of the important aspects of cycling
that is ignored because it isn't important to UCI racing :-(

I suspect that in terms of a bicycle it isn't overly important, or
perhaps not easily corrected. A 25 tooth rear sprocket would require a
113 tooth front sprocket to match the usual 50/11 road gearing.

Oh, it's important, all right! Derailleurs are chain and sprocket
eaters, at best (fixed and hub gears have a VASTLY higher distance
between maintenance, and even more between replacement). But many
vendors like selling short-life equipment, because they make their
profit on the replacements.

My experience on my singlespeed and Rohloff hubbed bikes is that the chains
and sprockets don't last longer that the chains and cassettes on my
derailleur equipped bikes. It is true that you can ride longer with a worn
chain and sprocket without getting into trouble. The sprocket on my Rohloff
ATB lasted 1500 km. When I replaced the chain the new chain made a terrible
noise. I reversed the sprocket and the noise was gone. 1500 km is a pathetic
mileage even for a ATB used mostly in dirty conditions. The same goes for my
singlespeed.


It's soluble only by using hub gears or by even more drastic
measures.

Not in my case.

My sprocket on my Rohloff ATB lasts already 3000 km, almost all rides
in dirty wet conditions.

My third chain although on it - no problems so far...

Keep my fingers X'ed.

Martin Borsje wrote:
Lou Holtman formulated the question :
On 2015-02-21 11:30:25 +0000, Nick Maclaren said:

In article ,
John B. Slocomb wrote:
Does anyone know of an engineering or experimental reference to
how the rate of wear of a sprocket varies with number of teeth?
All of Renolds, Rexnord and Diamond strongly disrecommend below
13 teeth, and advise more, but the reason is irregularity of
speed, not rate of wear.
My experience from a long time back with hub gears is that it is
highly non-linear once you get below (say) 16 teeth.
I took a quick look and there apparently is a correlation between
sprocket size and wear although I didn't find a specific calculation I
did find a reference that in a low ratio chain drive the total number
of drive and driven teeth, for best longevity, should not be less
than 50, i.e., a 25 tooth driver and a 25 tooth driven which seems to
be indicative.
Thanks. This could be another of the important aspects of cycling
that is ignored because it isn't important to UCI racing :-(
I suspect that in terms of a bicycle it isn't overly important, or
perhaps not easily corrected. A 25 tooth rear sprocket would require a
113 tooth front sprocket to match the usual 50/11 road gearing.
Oh, it's important, all right! Derailleurs are chain and sprocket
eaters, at best (fixed and hub gears have a VASTLY higher distance
between maintenance, and even more between replacement). But many
vendors like selling short-life equipment, because they make their
profit on the replacements.

My experience on my singlespeed and Rohloff hubbed bikes is that the
chains and sprockets don't last longer that the chains and cassettes
on my derailleur equipped bikes. It is true that you can ride longer
with a worn chain and sprocket without getting into trouble. The
sprocket on my Rohloff ATB lasted 1500 km. When I replaced the chain
the new chain made a terrible noise. I reversed the sprocket and the
noise was gone. 1500 km is a pathetic mileage even for a ATB used
mostly in dirty conditions. The same goes for my singlespeed.

It's soluble only by using hub gears or by even more drastic
measures.

Not in my case.

My sprocket on my Rohloff ATB lasts already 3000 km, almost all rides in
dirty wet conditions.

My third chain although on it - no problems so far...

Keep my fingers X'ed.

Hmm, three chains for 3000 km. It was obvious that I waited a bit to long
replacing the chain. Your numbers prove that. Bottom line is that my
experience is that the same chain wears as fast on a single speed or
gearhub setup as on a derailleur setup.

--
Lou