"The Engineer" - Solution to last month's problem

[Vic]

Here's the question which was posed in last month's "The Engineer", and which I posted to RBT for
the amusement and delight of the patrons here.

"Stan the cyclist is keen to stay abreast of latest developments so purchased a hi-tech carbon fibre
rear wheel with 16 radial spokes equally spaced and alternating eight to each side of the hub. The
wheel builder has centred the rim and trued the wheel and then torqued up the spokes to give a
tension of 125kg (sic) per spoke. As Stan lowers his 75kg onto the saddle he wonders what the
tension is in the spokes now.

Well the proposed answer has now been printed:

"The load in the spokes does not change until the imposed load exceeds the preload - so as the
cyclist weighs less than the preload, the spokes remain tensioned to 125kg".

This doesn't add up as far as I can see - perhaps "The Engineer"'s letters page has been a bit
slow lately...

Vic.

 

[Jonathan Bond]

Vic wrote:
> Here's the question which was posed in last month's "The Engineer", and which I posted to RBT for
> the amusement and delight of the patrons here.
>
> "Stan the cyclist is keen to stay abreast of latest developments so purchased a hi-tech carbon
> fibre rear wheel with 16 radial spokes equally spaced and alternating eight to each side of the
> hub. The wheel builder has centred the rim and trued the wheel and then torqued up the spokes to
> give a tension of 125kg (sic) per spoke. As Stan lowers his 75kg onto the saddle he wonders what
> the tension is in the spokes now.
>
> Well the proposed answer has now been printed:
>
> "The load in the spokes does not change until the imposed load exceeds the preload - so as the
> cyclist weighs less than the preload, the spokes remain tensioned to 125kg".
>
> This doesn't add up as far as I can see - perhaps "The Engineer"'s letters page has been a bit
> slow lately...
>
> Vic.

Of course the spokes have no more preload - if you're been following alt.mountain-bike's thread on
damped suspension, you'll realize that bikers do indeed fly

Jon Bond

 

[Jonathan Bond]

Jonathan Bond wrote:
> Vic wrote:
>
>> Here's the question which was posed in last month's "The Engineer", and which I posted to RBT for
>> the amusement and delight of the patrons here.
>>
>> "Stan the cyclist is keen to stay abreast of latest developments so purchased a hi-tech carbon
>> fibre rear wheel with 16 radial spokes equally spaced and alternating eight to each side of the
>> hub. The wheel builder has centred the rim and trued the wheel and then torqued up the spokes to
>> give a tension of 125kg (sic) per spoke. As Stan lowers his 75kg onto the saddle he wonders what
>> the tension is in the spokes now.
>>
>> Well the proposed answer has now been printed:
>>
>> "The load in the spokes does not change until the imposed load exceeds the preload - so as the
>> cyclist weighs less than the preload, the spokes remain tensioned to 125kg".
>>
>> This doesn't add up as far as I can see - perhaps "The Engineer"'s letters page has been a bit
>> slow lately...
>>
>> Vic.
>
>
> Of course the spokes have no more **preload**

Er, tension. And no more or less... yeah, its 4AM, I'm going to bed.

> - if you're been following alt.mountain-bike's thread on damped suspension, you'll realize that
> bikers do indeed fly
>
> Jon Bond

 

[Todd Holland]

Well I think that Stan's a sap for buying a wheel with no crossed spokes in the rear and no dish.

Todd H.

> Vic wrote:
>
>> Here's the question which was posed in last month's "The Engineer", and which I posted to RBT for
>> the amusement and delight of the patrons here.
>>
>> "Stan the cyclist is keen to stay abreast of latest developments so purchased a hi-tech carbon
>> fibre rear wheel with 16 radial spokes equally spaced and alternating eight to each side of the
>> hub. The wheel builder has centred the rim and trued the wheel and then torqued up the spokes to
>> give a tension of 125kg (sic) per spoke. As Stan lowers his 75kg onto the saddle he wonders what
>> the tension is in the spokes now.
>>
>> Well the proposed answer has now been printed:
>>
>> "The load in the spokes does not change until the imposed load exceeds the preload - so as the
>> cyclist weighs less than the preload, the spokes remain tensioned to 125kg".
>>
>> This doesn't add up as far as I can see - perhaps "The Engineer"'s letters page has been a bit
>> slow lately...
>>
>> Vic.

 

[Dianne_1234]

Lot of variable, more than were given in the problem statement I think.

Why not do the experiment and measure the change in spoke tension? Would the change vary depending
on the relative stiffness of the rim and spokes?

I have a used Wheelsmith tensiometer, but I didn't get the calibration chart. Anyone have one? Even
if it's off, the change might show something...

[email protected] (Todd Holland) wrote in message
news:<[email protected]>...
> Well I think that Stan's a sap for buying a wheel with no crossed spokes in the rear and no dish.
>
> Todd H.
>
> > Vic wrote:
> >
> >> Here's the question which was posed in last month's "The Engineer", and which I posted to RBT
> >> for the amusement and delight of the patrons here.
> >>
> >> "Stan the cyclist is keen to stay abreast of latest developments so purchased a hi-tech carbon
> >> fibre rear wheel with 16 radial spokes equally spaced and alternating eight to each side of the
> >> hub. The wheel builder has centred the rim and trued the wheel and then torqued up the spokes
> >> to give a tension of 125kg (sic) per spoke. As Stan lowers his 75kg onto the saddle he wonders
> >> what the tension is in the spokes now.
> >>
> >> Well the proposed answer has now been printed:
> >>
> >> "The load in the spokes does not change until the imposed load exceeds the preload - so as the
> >> cyclist weighs less than the preload, the spokes remain tensioned to 125kg".
> >>
> >> This doesn't add up as far as I can see - perhaps "The Engineer"'s letters page has been a bit
> >> slow lately...
> >>
> >> Vic.

 

[James Connell]

dianne_1234 wrote:
> Lot of variable, more than were given in the problem statement I think.
>
> Why not do the experiment and measure the change in spoke tension? Would the change vary depending
> on the relative stiffness of the rim and spokes?
>
> I have a used Wheelsmith tensiometer, but I didn't get the calibration chart. Anyone have one?
> Even if it's off, the change might show something...
>

won't help, they are for each tool. and the actual reading depends on what type spoke you use it on.
anything between ~ 40 and 80 is 'good' - it depends.

 

[Humongojugomang]

>f you're been following alt.mountain-bike's thread on damped suspension, you'll realize that bikers
>do indeed fly
>

hahahahahahah

 

[Dave Kahn]

[email protected] (Vic) wrote in message
news:<[email protected]>...

> "The load in the spokes does not change until the imposed load exceeds the preload - so as the
> cyclist weighs less than the preload, the spokes remain tensioned to 125kg".

The "model" answer is so strange that I'm wondering if something has been missed both from it
and the question. Possibly the question was meant to be: what happens to the tension in the
uppermost spokes?

--
Dave...