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From: AMuzi <am@yellowjersey.org>
Newsgroups: rec.bicycles.tech
Subject: Re: Wheel-less tire question
Date: Thu, 13 Mar 2025 16:15:50 -0500
Organization: Yellow Jersey, Ltd.
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On 3/13/2025 1:46 PM, Mark J cleary wrote:
> On 3/13/2025 1:36 PM, Roger Merriman wrote:
>> AMuzi <am@yellowjersey.org> wrote:
>>> On 3/13/2025 11:29 AM, bp@www.zefox.net wrote:
>>>> This is mostly a philosophical question, but maybe it 
>>>> has a technical answer.
>>>>
>>>> The rim of a bike wheel is a relatively heavy component, 
>>>> largely because
>>>> of its circumference. Could it be dispensed with, at 
>>>> least in the case of
>>>> a tubular tire, by making the spokes extensions of the 
>>>> tire carcass cords?
>>>> The hub would remain mostly the same, with the "spoke" 
>>>> cords of the tire
>>>> laced around anchors on the hub flanges.
>>>>
>>>> It wouldn't be very convenient to handle, indeed, a 
>>>> spider's nightmare.
>>>> But, it could fold up much like a parachute. The tire 
>>>> would have to be
>>>> inflated to a pressure sufficient to support the needed 
>>>> spoke tension,
>>>> which might be rather higher than the pressure used in 
>>>> traditional
>>>> tubular tires.
>>>>
>>>> It would be hard to manufacture, getting all the spoke 
>>>> lengths matched
>>>> to run true being the most obvious difficulty. But 
>>>> intuition suggests
>>>> it would be about the lightest construction possible, as 
>>>> well as the
>>>> most compact when stowed before use.
>>>>
>>>> Another way of asking the same question is to ask the 
>>>> stiffness of a
>>>> fully-inflated, unmounted tubular tire compared to a 
>>>> traditional wood
>>>> or metal wheel rim.
>>>>
>>>> I've never handled one and so have difficulty guessing.
>>>>
>>>> Thanks for reading, and any insights.
>>>>
>>>> bob prohaska
>>>>
>>>>
>>>>
>>>>
>>>>
>>>
>>> Short answer = no.
>>>
>>> A tensioned wheel, (as bicycles wheels with actual tensioned
>>> spokes, not including carbon sheets) has to have a
>>> noncompressible* rim of constant* circumference in order to
>>> not flop around.  It's an elegant thing, with among the
>>> highest strength to weight ratios of human built structures.
>>>
>>> The principles are similar to an arch:
>>>
>>> https://tse2.mm.bing.net/th? 
>>> id=OIP.OtdqiBPMvo3_wmobAocS0AHaEN&pid=15.1&w=474&h=274&c=7
>>>
>>> Tension inward on the spoke is compressing the rim
>>> circumference making a rigid structure. Vertical load on an
>>> arch (keystone) is supported by the sides, with load along a
>>> vector (not vertical as a post and lintel). An arch made of
>>> cooked gnocchi would of course fall apart, as would a
>>> bicycle wheel with a fabric 'rim'.
>>>
>>> Pressed steel auto wheels are different, in that there is
>>> not a tension component. The face behaves like an infinite
>>> series of compression spokes (as wooden wheels use) and as
>>> such is heavier for any given strength.
>>>
>>> Further to all that:
>>> https://www.astounding.org.uk/ian/wheel/
>>>
>>> *practically but not absolutely
>>>
>>>
>>
>> Indeed good reasons why spokes haven’t been replaced, much 
>> like the chain
>> it’s just too good!
>>
>> Roger Merriman
>>
> Seems many hate spokes and weight what can we do to get rid 
> of them and my friend, spokes are your friend. I don't use 
> 36 spoke rims I admit but would if I had to and the 
> conditions warranted it. You can ride 36 hole rim with a bad 
> spoke but try with 20 spoke rim?
> 

No simple answer but, as in so many things discussed here, 
you can make your own personal risk assessment on that.

-- 
Andrew Muzi
am@yellowjersey.org
Open every day since 1 April, 1971