You sound like a mechanical engineer, and I'm just an electrical and systems engineer, so I guess I basically defer and would like to learn. Are you talking about the force at the (deformed, I guess) contact between a single ball and the race, or the total load carried by the entire bearing. For two bikes of similar weight, load, geametry, travel speed, and current road condition, the load carried by each bearing system (top headset system and bottom headset system) should be about the same.If there are more contact points, how can the per ball load be greater. I could see the peak load in a given ball/race contact patch being greater in a smaller ball perhaps due to the smaller radius.
I guess you're saying the load capacity per ball is greater for larger balls because the radius at the point of peak contact pressure is larger that for the smaller ball. Greater durability in the bigger ball headset versus the track headset.
On Sun, Jan 10, 2010 at 6:19 PM, Andrew R Stewart <onetenth@earthlink.net>wrote:
> Ken- Your take on bearing load capacity is the opposite that I understand.
> I've always heard (and see in my work) that the load a bearing is a
> geometric factor of it's diameter. So half the balls of twice the diameter
> will result in the unit having twice the load. If the ball count remained
> the same (and the overall size of the unit then grew) the unit would have 4
> times the load capacity.
>
> My take on the smaller balls in the Pista unit was two fold. First the
> smooth track conditions didn't require maximum load capacity and the overall
> stack height could be lower. this allowed a lower bar/stem position.
>
> Any one out there have more definitive information?
>
> ----- Original Message ----- From: "Ken Freeman" <kenfreeman096@gmail.com>
> To: "Dean Nixon" <vintage.lugged@gmail.com>
> Cc: <classicrendezvous@bikelist.org>
> Sent: Sunday, January 10, 2010 9:34 AM
> Subject: Re: [CR] Identifying Campagnolo Pista vs. Strada Headsets
>
>
>
> For the same race diameter, smaller balls allow more balls in that
>> circumference. Half the ball diameter would allow twice as many balls.
>> More balls allow more points of contact and better load sharing, i.e. the
>> contact pressure at each contact point is less than for a larger ball.
>>
>> No, bigger is not always better!
>>
>>
>>
>> On Sun, Jan 10, 2010 at 8:46 AM, Dean Nixon <vintage.lugged@gmail.com
>> >wrote:
>>
>> In particular for the Super Record models - they seem identical even in
>>> the
>>> old catalogs. Other than the bearing size (3/16 vs. 5/32) is there any
>>> way
>>> to tell the difference visually? Measuring the diameter of the races
>>> would
>>> be difficult I think. Also, will the races get damaged if they are used
>>> with
>>> bearings that are either to large or too small? What is the rational
>>> behind
>>> using 3/16" bearings for the pista version anyway? Just wondering...
>>>
>>> Dean Nixon
>>> Toronto, Canada
>>> _______________________________________________
>>>
>>>
>>
>>
>> --
>> Ken Freeman
>> Ann Arbor, MI USA
>> _______________________________________________
>>
>
> Andrew R Stewart
> Rochester, NY
>
--
Ken Freeman
Ann Arbor, MI USA