I have weighed Duprat hollow cranks and yes, the Duprat hollow cranks are as light as aluminium - the 5-pin weigh just over 12oz for a pair and the 3-arm about 15-16oz for a pair - both without rings. But they were not especially reliable...
Quite a few older components are really light - Constrictor Asp rims in 26in weigh about 450-470g, Dunlop Special Lightweight steel only about 590g, less than some modern aluminium ones and less than the solid section Constrictor Boalloys.
Hilary Stone, Bristol, England
Chuck Schmidt wrote:
> I would be very surprised if that was the case, but of course, I'd have
> no way of knowing without actually weighing them. Perception is
> extremely imprecise...
>
> I picked up a track bike at the Framebuilders show the other month that
> weighed a little over seven pounds (yes, complete bike) and it felt the
> same weight as a full water bottle, which of course it didn't.
>
> Chuck Schmidt
> South Pasadena, CA
>
> On Apr 21, 2007, at 1:23 PM, Kurt Sperry wrote:
>
>> Weren't the hollow armed steel cottered cranks just as light as Al alloy
>> cotterless? I hefted a '50s Durax (?) octagonal armed crank and
>> although I
>> didn't weigh it, it felt about the same as Al alloy Campagnolo Record
>> cranks
>> to me weight wise.
>>
>> Kurt Sperry
>> Bellingham WA
>> USA
>>
>>
>> On 4/20/07, Chuck Schmidt <chuckschmidt@earthlink.net> wrote:
>>>
>>> This appeared on the iBOB list yesterday and I thought this might be
>>> an interesting subject for discussion on the CR list. Anyone want to
>>> add their comments?
>>>
>>> On Apr 20, 2007, at 7:22 AM, Jan Heine wrote:
>>> > More importantly, we (Bicycle Quarterly) put the history in
>>> > perspective. Many of our readers don't care when a logo on a crank
>>> > was changed, but they are fascinated by finding out why old bikes
>>> > were designed in certain ways and what we can learn from that. For
>>> > example, why did racers continue to use heavier steel cranks for
>>> > almost 25 years after the Stronglights were introduced? In various
>>> > web forums, you read that it was because the racers feared that the
>>> > aluminum cranks broke. BQ showed that many racers in the early
>>> > 1950s used aluminum cranks in mountain stages - if they were afraid
>>> > of failure, they would not have used them on stages where cranks
>>> > suffer from the highest loads. However, these racers switched to
>>> > steel cranks for flat stages. Combined with other evidence, we
>>> > concluded that on the flats, where weight matters little, the
>>> > racers preferred the lower tread (Q factor) of the steel cranks. In
>>> > the mountains, they were willing to pedal with their feet apart in
>>> > exchange for almost a pound less in weight. Suddenly, you realize
>>> > that there was a method behind this, rather than just "racers
>>> > always are conservative." And of course, it illustrates that racers
>>> > believed tread (Q factor) was very important, something that many
>>> > people still believe today, even though many crank manufacturers
>>> > don't care about tread at all.
>>>
>>>
>>> Jan writes, "BQ (Bicycle Quarterly) showed that many racers in the
>>> early 1950s used aluminum cranks in mountain stages - if they were
>>> afraid of failure, they would not have used them on stages where
>>> cranks suffer from the highest loads. However, these racers switched
>>> to steel cranks for flat stages."
>>>
>>> Aluminum cranks were first used by professional racers in the early
>>> '50s on mountain stages because of their light weight. Even though
>>> aluminum cranks were introduced in the mid 1930s, pro racers were too
>>> conservative to try them since they were new and unproven. Also
>>> aluminum's lack of a fatigue limit was well known (aluminum bike
>>> frames date back before 1900), so what better reason not to use
>>> aluminum cranks on flat stages since weight wasn't an issue on the
>>> flats. Also bear in mind that WWII interrupted the 25 years that it
>>> took pro racers to ride with aluminum cranks (no racing of any
>>> significance for the ten years between 1939 and 1948).
>>>
>>> Jan writes, "Combined with other evidence, we (Bicycle Quarterly)
>>> concluded that on the flats, where weight matters little, the racers
>>> preferred the lower tread (Q factor) of the steel cranks."
>>>
>>> I think what the pro racers preferred was the piece of mind of racing
>>> on their race proven steel cranks. In all my reading and talking to
>>> geezers that raced I have never once heard a concern for the
>>> different tread dimension (Q factor) of steel and aluminum cranks. I
>>> think your conclusion that racers didn't use aluminum cranks because
>>> the tread dimension was slightly wider, not because they didn't trust
>>> them, is highly suspect given the overall conservative nature of pro
>>> racing back in the thirties and forties.
>>>
>>> Incidentally I measured the distance the pedals are moved outwards,
>>> comparing a 1950 Bianchi Folgorissima equipped with steel Magistroni
>>> cranks and a 1979 Bianchi Superleggera equipped with aluminum
>>> Campagnolo Super Record cranks: it's a pretty insignificant 8.5mm on
>>> each side!
>>>
>>> Chuck Schmidt
>>> South Pasadena, CA