jim beam wrote:
> Peter Cole wrote:
>> jim beam wrote:
>>> Peter Cole wrote:
>>> <snip for clarity>
>>>>
>>>> >> "One plant has been making over 1.2 million tons of degassed sheet
>>>> >> steel to supply the automotive market" (annual).
>>>>
>>>> Given that the US annual vehicle production is around 15M, just that
>>>> one plant would be contributing around 200lb of *sheet* to the
>>>> average vehicle.
>>>
>>> and as i said earlier, for a 3,000lb vehicle, it's /clearly/ not
>>> being used for /all/ the material.
>>>
>>>
>>>>
>>>>
>>>>> and even then, not every manufacturer would be interested. it
>>>>> would be great for forged cranks for example, but the majority of
>>>>> producers cast cranks because it's so much cheaper - fatigue
>>>>> benefits of superior materials be hanged.
>>>>
>>>> http://tinyurl.com/ywqhhy
>>>
>>> what part of "Racing Crankshaft" is hard to comprehend as being
>>> atypical when we're talking about using cast iron for cheap ****?
>>>
>>>
>>>>
>>>>
>>>>> as for chronology, the benefits have been known for a long time -
>>>>> since the 30's i believe, but knowing about it, being able to
>>>>> produce it, and /paying/ for it are all completely different
>>>>> things. i don't believe that an auto industry that will save 6' of
>>>>> copper wire by using the same bulb for brake lights and turn
>>>>> signals, or not using washers/gaskets on spark plugs, has the
>>>>> /slightest/ interest in paying extra for vacuum degassed steels
>>>>> when cheap cast iron **** will do.
>>>>
>>>> Well, you're entitled to your beliefs, but it seems you are wrong.
>>>
>>> eh? wrong like trying to ******** about racing cranks being used in
>>> everyday vehicles is wrong?
>>
>> Who said that? All I'm proving with that link is that a complete
>> (65lb) crankshaft, forged with vacuum degassed steel is only $438, qty
>> 1. How much do you think the vacuum degassing added to that price?
>
> er, the majority of domestic crankshafts are cast. /you/ cite one that
> isn't in a context of being contrarian. as usual.
No, just looking at the economics.
>>>> As for vacuum degassing being somehow cost prohibitive for bicycle
>>>> spokes, consider that even at an extra $100/ton, the change in raw
>>>> material costs would be less than a dime for a bike's worth of spokes.
>>>
>>> er, you need to check out
>>> http://www.steelonthenet.com/steel_cost_bof.html
>>>
>>> if i'm paying $261.50 per ton for steel, paying an extra 38% to get
>>> it degassed is kind of significant.
>>
>> Not if you're making spokes, which is the whole point.
>
> yes if you're making spokes, which is the whole point. materials costs
> are something and they need to be managed. processing is another.
OK, you're claiming that for a $438/65lb ($6.75/lb) crankshaft, vacuum
degassed steel is economical, but for a $.60/8g spoke ($165/lb) it isn't?
>> All of these examples prove that vacuum degassed steel has been in
>> common use for a long time and doesn't cost much, contrary to your
>> assertions. Since this is the crux of your argument about the need for
>> stress relieving, you need to rethink the matter.
>
> it's been around since the 30's iirc, but it's not been widely used -
> partly due to low tonnage, but mainly due to cost. it's not
> /prohibitively/ expensive, but if it erodes a manufacturers profit, and
> there's no benefit for that application, who is going to use it?
You are the one claiming the benefit (in spokes). It's been around and
widely available since the mid 60's anyway -- used in bulk,
cost-sensitive apps (auto sheet metal) since the 70's at least.
Let's review.
You have claimed that stress relieving of spokes is not necessary since
spoke failures are caused by surface defects, commonly inclusions. The
solution is to use quality spokes like Sapim, who, according to their
website, use vacuum degassed steel. You back up this claim with a hand
drawing of a spoke failing at an inclusion, which you assert is
representative.
You claim that the use of vacuum degassed steels was unlikely until
fairly recently because of cost and availability. The record indicates
that this was not true since at least the mid-60's.
You claim that the use of vacuum degassed steel in spokes is still
prohibitively expensive for some manufacturers. It defies reason that a
manufacturer could afford the alloying elements of stainless and not
afford to degass the steel.
Let's suppose your claim that spokes only fail at inclusions is true,
and that after using defect free material we don't need to stress
relieve. This is because:
1) There aren't any residual stresses to relieve.
2) They don't matter for fatigue life.
Item 1 is false. Metallurgists have agreed with Jobst's model on this
forum (it's archived). I have observed the residual stress first hand by
making a "slitting" experiment -- a technique that is used in industry.
Item 2 is also false. If a spoke is nominally tensioned to 33% of yield,
and the endurance limit is 40% of yield, even a small amount of residual
stress can dramatically shorten the fatigue life. Since Jobst has
reported spoke lifetimes of over 10^8 cycles, his technique must be
reducing residual stresses to a very low level since he must be below
the endurance limit.
