Headset dead spot?

[jim beam]

[email protected] wrote:
> On Apr 6, 9:32 pm, jim beam <[email protected]> wrote:
>> you're a blathering freakin' idiot utterly clueless of
>> extremely well and abundantly documented facts that any "engineering
>> professor" should know. all you do is shoot your mouth, completely
>> unable to add the smallest quantum of value. other than entertaining
>> with your uselessness of course. give up your day job krygowski. every
>> check you cash is the commission of fraud.
>
> Seems like every time I post web links that prove you're wrong, you
> lapse into another childish tantrum.

funny. and ironic because it seems every time /i/ post something that
might help fill a little of the huge cognizance gaps in your meager
grasp of engineering basics, you don't read them!


> We've gone through this many
> times - for example, when you claimed no bike components are castings.

thixo-forming has a completely different microstructure to casting.
that's why thixo-forming is not /called/ casting! idiot.


>
> You tell others to do your work, use Google to find photos to prove
> you right. Why won't _you_ use Google to learn a little, before
> arguing yourself into a corner? If you didn't have to defend such
> obvious mistakes, maybe you could be more civil.

see above. and i'd be civil to someone that wasn't a fraud. and i
wouldn't be /able/ to point out that you're an idiot if you weren't one.


>
> Google "false brinell." Read a few links. Or stop in at any
> engineering library and start learning about bearings.
>

if only /you/ would do that, maybe you'd have some idea of what you
didn't know.

[only a complete idiot could try to lecture from a position of utter
ignorance and complain when they get it wrong. and yet again, your post
is completely free of any technical content.]

 

[jim beam]

still just me wrote:
> On Mon, 07 Apr 2008 05:56:16 -0700, jim beam
> <[email protected]> wrote:
>
>> as for grinding paste, yes, it will work for a while, but it has a risk
>> of eroding the seat post [because there will be small movement and thus
>> abrasion] and it could subsequently fatigue and break.
>
> I think it's highly unlikely that using valve grinding paste
> (typically around 500 grit) will lead to any sort of a failure. Those
> are very, very minor. People run with scratches way deeper than that
> on their posts from frame imperfections for years and years and years
> and never have a failure.

it's not the grit size, it's the erosion.



>
> For the OP, I still wouldn't use a compound with that kind of grit
> factor to fix your seat post situation.

 

[Ben C]

On 2008-04-04, jim beam <[email protected]> wrote:
> Ben C wrote:
[...]
>> Yes but the distinction here is important. Do you get those indents from
>> a single big thump or overload, or are they gradually eaten away by some
>> kind of corrosion/fretting process?
>>
>> The practical side of this is that a headset that's too loose I would
>> expect to be more prone to true brinelling, one that's too tight more
>> prone to the false kind.
>
> other way about.

I figure that if there's some up and down travel in the headset because
it's loose the bearings get a bigger knock when you hit a bump.

I think it's because if they're loose they're less protected by ability
of the tyre and fork to slow down the impact.

Suppose the front wheel is crashing back down to earth after a bump.
While it's in mid-air, the fork drops a bit because the headset is loose
and so there's a small gap between the bearings and the races. The tyre
hits the ground first and perhaps bounces up a bit but in any case the
bearings collide with the races directly.

If you plot force against time at the bearing for the impact I think you
get the same area for tight and loose headsets (total change of momentum
the same), but a shorter fatter shape with lower maximum force for the
tight headset. So perhaps less risk of true brinelling.

I think tight headsets are more likely to promote false brinelling
because if they're too tight they may prevent the balls rolling around
and the grease circulating.

On the other hand, increasing pre-load increases total load when you hit
a given bump, so I can see that too-tight could also promote true
brinelling.

And I suppose too loose could promote false brinelling if it meant all
the grease leaked out.

 

[Ben C]

On 2008-04-08, Ben C <[email protected]> wrote:
> On 2008-04-04, jim beam <[email protected]> wrote:
>> Ben C wrote:
> [...]
>>> Yes but the distinction here is important. Do you get those indents from
>>> a single big thump or overload, or are they gradually eaten away by some
>>> kind of corrosion/fretting process?
>>>
>>> The practical side of this is that a headset that's too loose I would
>>> expect to be more prone to true brinelling, one that's too tight more
>>> prone to the false kind.
>>
>> other way about.
>
> I figure that if there's some up and down travel in the headset because
> it's loose the bearings get a bigger knock when you hit a bump.
>
> I think it's because if they're loose they're less protected by ability
> of the tyre and fork to slow down the impact.
>
> Suppose the front wheel is crashing back down to earth after a bump.
> While it's in mid-air, the fork drops a bit because the headset is loose
> and so there's a small gap between the bearings and the races. The tyre
> hits the ground first and perhaps bounces up a bit but in any case the
> bearings collide with the races directly.
>
> If you plot force against time at the bearing for the impact I think you
> get the same area for tight and loose headsets (total change of momentum
> the same), but a shorter fatter shape with lower maximum force for the
> tight headset. So perhaps less risk of true brinelling.
>
> I think tight headsets are more likely to promote false brinelling
> because if they're too tight they may prevent the balls rolling around
> and the grease circulating.
>
> On the other hand, increasing pre-load increases total load when you hit
> a given bump, so I can see that too-tight could also promote true
> brinelling.
>
> And I suppose too loose could promote false brinelling if it meant all
> the grease leaked out.

Following up to myself here, but I think from the other posts that
too-loose promotes false brinelling because it allows the balls to
vibrate?

That's why you pre-load in the first place, but hopefully not by too
much.

 

[jim beam]

Ben C wrote:
> On 2008-04-08, Ben C <[email protected]> wrote:
>> On 2008-04-04, jim beam <[email protected]> wrote:
>>> Ben C wrote:
>> [...]
>>>> Yes but the distinction here is important. Do you get those indents from
>>>> a single big thump or overload, or are they gradually eaten away by some
>>>> kind of corrosion/fretting process?
>>>>
>>>> The practical side of this is that a headset that's too loose I would
>>>> expect to be more prone to true brinelling, one that's too tight more
>>>> prone to the false kind.
>>> other way about.
>> I figure that if there's some up and down travel in the headset because
>> it's loose the bearings get a bigger knock when you hit a bump.
>>
>> I think it's because if they're loose they're less protected by ability
>> of the tyre and fork to slow down the impact.
>>
>> Suppose the front wheel is crashing back down to earth after a bump.
>> While it's in mid-air, the fork drops a bit because the headset is loose
>> and so there's a small gap between the bearings and the races. The tyre
>> hits the ground first and perhaps bounces up a bit but in any case the
>> bearings collide with the races directly.
>>
>> If you plot force against time at the bearing for the impact I think you
>> get the same area for tight and loose headsets (total change of momentum
>> the same), but a shorter fatter shape with lower maximum force for the
>> tight headset. So perhaps less risk of true brinelling.
>>
>> I think tight headsets are more likely to promote false brinelling
>> because if they're too tight they may prevent the balls rolling around
>> and the grease circulating.
>>
>> On the other hand, increasing pre-load increases total load when you hit
>> a given bump, so I can see that too-tight could also promote true
>> brinelling.
>>
>> And I suppose too loose could promote false brinelling if it meant all
>> the grease leaked out.
>
> Following up to myself here, but I think from the other posts that
> too-loose promotes false brinelling because it allows the balls to
> vibrate?
>
> That's why you pre-load in the first place, but hopefully not by too
> much.

that's right. you need a degree of preload, to stop the sliding in
false brinelling, but as you say, too much means you reduce the load
bearing capacity that would lead to true brinelling.

don't get too side-tracked on the "no grease" theory - it's a little
out-dated as it fails to explain why otherwise identical bearings in
oxygen-free environments don't false brinell. it also ignores the fact
that any bearing that's not rotating fast enough will not
hydrodynamically separate, and thus there will be full metal-to-metal
contact, complete with asperity welding. and bearings operate for
decades in this state with no apparent problems.

 

[Peter Cole]

Hugh Fenton wrote:
> "Teh bike guy" <[email protected]> wrote in message
> news:[email protected]...
>> This is common and easy to fix, just squirt some toothpaste (whitening
>> formulations work best) into the headset and ride around for a few miles,
>> it will become all smooth again, after that you can flush with water and
>> add grease.
>>
>>
>
> On a vaguely similar topic.........
>
> I've an old aluminium CADEX ALM1 where the (lubricated) seatpost keeps
> slipping down slowly........ No, the clamp IS correctly adjusted AND the
> seat tube isn't squeezed closed...but it still happens unless I overtension
> the quick release (and I DO need one of these owing to the riding I do.)
>
> A friend suggested that valve grinding paste would solve my
> problem.........an inert grit to prevent movement embedded in a lubricant to
> prevent seizure......
>
> Comments??????
>
> Hugh Fenton
>
>

First thing I would try is to lube the QR cam and, if it's the removable
collar type, lube between the collar and frame tube. Sometimes friction
in these places limits the clamping force.

 

[Werehatrack]

On Tue, 08 Apr 2008 12:54:34 GMT, Peter Cole <[email protected]>
may have said:

>Hugh Fenton wrote:
>> "Teh bike guy" <[email protected]> wrote in message
>> news:[email protected]...
>>> This is common and easy to fix, just squirt some toothpaste (whitening
>>> formulations work best) into the headset and ride around for a few miles,
>>> it will become all smooth again, after that you can flush with water and
>>> add grease.
>>>
>>>
>>
>> On a vaguely similar topic.........
>>
>> I've an old aluminium CADEX ALM1 where the (lubricated) seatpost keeps
>> slipping down slowly........ No, the clamp IS correctly adjusted AND the
>> seat tube isn't squeezed closed...but it still happens unless I overtension
>> the quick release (and I DO need one of these owing to the riding I do.)
>>
>> A friend suggested that valve grinding paste would solve my
>> problem.........an inert grit to prevent movement embedded in a lubricant to
>> prevent seizure......
>>
>> Comments??????
>>
>> Hugh Fenton
>>
>>
>
>First thing I would try is to lube the QR cam and, if it's the removable
>collar type, lube between the collar and frame tube. Sometimes friction
>in these places limits the clamping force.

Also, a detail I'd forgotten; if the split in the tube is not lined up
with the split in the camp, the grease mentioned becomes absolutely
essential.


--
My email address is antispammed; pull WEEDS if replying via e-mail.
Typoes are not a bug, they're a feature.
Words processed in a facility that contains nuts.

 

[John Thompson]

On 2008-04-07, Hugh Fenton <[email protected]> wrote:

> I've an old aluminium CADEX ALM1 where the (lubricated) seatpost keeps
> slipping down slowly........ No, the clamp IS correctly adjusted AND the
> seat tube isn't squeezed closed...but it still happens unless I overtension
> the quick release (and I DO need one of these owing to the riding I do.)
>
> A friend suggested that valve grinding paste would solve my
> problem.........an inert grit to prevent movement embedded in a lubricant to
> prevent seizure......
>
> Comments??????

Some cheap headset races are only case-hardened; using grinding compound
to smooth pits in such a race will remove the hardening.


--

John ([email protected])