Singlespeed chain tension varying when wheels spins?



A

Alan Hoyle

Guest
I have an 80's Nishiki road bike converted to fixed by someone else.
I recently added a freewheel to the other side of the Suzue Basic
hub. I noticed something odd though: if I spin the wheel forward so
that it's "freewheeling" (i.e. pedals/chain stay put) the tension on
the chain still varies. Does this mean something bad is up with my
hub, like the axle or spindle is bent? I would expect to see the
tension vary if the chain was moving, but if it's sitting still....

-alan

--
Alan Hoyle - [email protected] - http://www.alanhoyle.com/
"I don't want the world, I just want your half." -TMBG
Get Horizontal, Play Ultimate.
 
N

Nate Knutson

Guest
Alan Hoyle wrote:
> I have an 80's Nishiki road bike converted to fixed by someone else.
> I recently added a freewheel to the other side of the Suzue Basic
> hub. I noticed something odd though: if I spin the wheel forward so
> that it's "freewheeling" (i.e. pedals/chain stay put) the tension on
> the chain still varies. Does this mean something bad is up with my
> hub, like the axle or spindle is bent? I would expect to see the
> tension vary if the chain was moving, but if it's sitting still....
>
> -alan
>
> --
> Alan Hoyle - [email protected] - http://www.alanhoyle.com/
> "I don't want the world, I just want your half." -TMBG
> Get Horizontal, Play Ultimate.


When the cranks are immobile and the chain tension is still varying,
that means something on the hub end is nonconcentric and causing the
problem. It could be a bent axle, freewheel threads machined slightly
off, or maybe an issue with the freewheel itself (although that seems
unlikely to me).
 
K

Kinky Cowboy

Guest
On 15 Sep 2006 17:54:11 GMT, Alan Hoyle <[email protected]> wrote:

>I have an 80's Nishiki road bike converted to fixed by someone else.
>I recently added a freewheel to the other side of the Suzue Basic
>hub. I noticed something odd though: if I spin the wheel forward so
>that it's "freewheeling" (i.e. pedals/chain stay put) the tension on
>the chain still varies. Does this mean something bad is up with my
>hub, like the axle or spindle is bent? I would expect to see the
>tension vary if the chain was moving, but if it's sitting still....
>
>-alan


Most likely source of eccentricity is the hole not being quite in the
middle of the freewheel body. If you look closely, you can probably
see the sprocket precessing around the spinning hub centre.

Kinky Cowboy*

*Batteries not included
May contain traces of nuts
Your milage may vary
 
R

RonSonic

Guest
On Fri, 15 Sep 2006 23:07:06 +0100, Kinky Cowboy <[email protected]> wrote:

>On 15 Sep 2006 17:54:11 GMT, Alan Hoyle <[email protected]> wrote:
>
>>I have an 80's Nishiki road bike converted to fixed by someone else.
>>I recently added a freewheel to the other side of the Suzue Basic
>>hub. I noticed something odd though: if I spin the wheel forward so
>>that it's "freewheeling" (i.e. pedals/chain stay put) the tension on
>>the chain still varies. Does this mean something bad is up with my
>>hub, like the axle or spindle is bent? I would expect to see the
>>tension vary if the chain was moving, but if it's sitting still....
>>
>>-alan

>
>Most likely source of eccentricity is the hole not being quite in the
>middle of the freewheel body. If you look closely, you can probably
>see the sprocket precessing around the spinning hub centre.


If my memory of the old days is correct that used to be pretty normal.

Ron
 
K

Kinky Cowboy

Guest
On Fri, 15 Sep 2006 21:06:08 -0400, RonSonic
<[email protected]> wrote:

>On Fri, 15 Sep 2006 23:07:06 +0100, Kinky Cowboy <[email protected]> wrote:
>
>>On 15 Sep 2006 17:54:11 GMT, Alan Hoyle <[email protected]> wrote:
>>
>>>I have an 80's Nishiki road bike converted to fixed by someone else.
>>>I recently added a freewheel to the other side of the Suzue Basic
>>>hub. I noticed something odd though: if I spin the wheel forward so
>>>that it's "freewheeling" (i.e. pedals/chain stay put) the tension on
>>>the chain still varies. Does this mean something bad is up with my
>>>hub, like the axle or spindle is bent? I would expect to see the
>>>tension vary if the chain was moving, but if it's sitting still....
>>>
>>>-alan

>>
>>Most likely source of eccentricity is the hole not being quite in the
>>middle of the freewheel body. If you look closely, you can probably
>>see the sprocket precessing around the spinning hub centre.

>
>If my memory of the old days is correct that used to be pretty normal.
>


Not just "not in the middle" but "not on a parallel axis" was normal
in the old days of multiple freewheels, so the sprocket carrier would
not only precess but wobble too as you spun the wheel. Although it
looked bad on the workstand, it was never a problem in real life.

Kinky Cowboy*

*Batteries not included
May contain traces of nuts
Your milage may vary
 
Q

Qui si parla Campagnolo

Guest
Alan Hoyle wrote:
> I have an 80's Nishiki road bike converted to fixed by someone else.
> I recently added a freewheel to the other side of the Suzue Basic
> hub. I noticed something odd though: if I spin the wheel forward so
> that it's "freewheeling" (i.e. pedals/chain stay put) the tension on
> the chain still varies. Does this mean something bad is up with my
> hub, like the axle or spindle is bent? I would expect to see the
> tension vary if the chain was moving, but if it's sitting still....
>
> -alan
>
> --
> Alan Hoyle - [email protected] - http://www.alanhoyle.com/
> "I don't want the world, I just want your half." -TMBG
> Get Horizontal, Play Ultimate.


Common as cranks, hubs, etc, are not really that round...all fixie
chains are a wee bit tight->loose, as it spins.
 
D

dvt

Guest
RonSonic wrote:
> On Fri, 15 Sep 2006 23:07:06 +0100, Kinky Cowboy <[email protected]> wrote:
>> Most likely source of eccentricity is the hole not being quite in the
>> middle of the freewheel body. If you look closely, you can probably
>> see the sprocket precessing around the spinning hub centre.

>
> If my memory of the old days is correct that used to be pretty normal.


I have a singlespeed freewheel that is not-so-old (5 years?) with this
problem. Although it has seen spotty use in those 5 years, I have been
using it on my daily commuter for about a year. It would work OK if the
rest of my system were healthy...

I have a problem getting proper chain tension with it, though. The
appropriately sized chainring that was in my spare parts bin was egg
shaped (biopace). With both cog and chainring non round or off center,
it's very difficult to get the chain tension right. There's a very small
range of adjustment where the drivetrain doesn't bind and the chain
doesn't jump off easily.

I lose my chain maybe once a month with this setup. I guess that means I
should fix it, but guess I haven't found the problem irritating enough
to spend time and money on it.

--
Dave
dvt at psu dot edu

Everyone confesses that exertion which brings out all the powers of body
and mind is the best thing for us; but most people do all they can to
get rid of it, and as a general rule nobody does much more than
circumstances drive them to do. -Harriet Beecher Stowe, abolitionist and
novelist (1811-1896)