They're very, very stiff... a quick twang of the spokes quickly explained why, there's incredible spoke tension between hub and rim
Bike Forum
Bike journo doesn't do physics shocker
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Posted 7 months ago #
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nobody want to support Matt then?
Posted 7 months ago # -
where's it from then?
very short quote you've given us.
Posted 7 months ago # -
Why not simply explain his 'mistake' (if indeed there is any), rather than attempt to look all superior?
I don't 'do physics' either. Or maffs. Not in my field of inertest.
How good's your cycling journalism?
Posted 7 months ago # -
Random internet person doesnt do proper thread shocker.
Posted 7 months ago # -
I'd have given up after the first non-response, tbh.
Posted 7 months ago # -
would that not make them stiff?
Posted 7 months ago # -
did more than a spot of physics, back in the day, and struggling here
Posted 7 months ago # -
Is it because the tension is between the spokes?
Posted 7 months ago # -
Obviously nobody else reads the mag then?
No - spoke tension doesn't affect wheel stiffness. Don't have a problem with people not doing stuff outside their specialist field, but it is irritating to see incorrect stuff in print.
Posted 7 months ago # -
Yea, where's the mistake?
High levels of pre applied tension = stiff structures, a principle used eveywhere from spoked wheels, railway lines through to huge dams.
Posted 7 months ago # -
I believe it's a miss-quote from one of Charlie Sheen's Tweets, I've rework it based on that assumption, should be read like this?:
I'm very, very stiff... a sudden twang In my underware and I realise, I've necked a dangerous cocktail of Rohypnol, Viagra and Half a bottle of Tequila... It's going to be another messy night, and yet again I won't remember a thing...
Posted 7 months ago # -
so if the spokes were barely screwed into the nips and all floppy it wouldn't affect the wheel stiffness?
Posted 7 months ago # -
spoke tension doesn't affect wheel stiffness
go on then, enlighten us to what does.
Posted 7 months ago # -
so if the spokes were barely screwed into the nips and all floppy it wouldn't affect the wheel stiffness?
That's a strawman. Provided the spokes are under enough tension that they don't go completely slack in use (as is the case for any half-decent wheel), increasing the tension further doesn't increase the stiffness.Posted 7 months ago # -
increasing the tension further doesn't increase the stiffness.
I think you'll find thats not true.
Posted 7 months ago # -
No - spoke tension doesn't affect wheel stiffness.
(Loosens spokes on wheel; notices wheel is now flopy. Tightens spokes on wheel, notices wheel is now stiff)
Posted 7 months ago # -
I think you'll find thats not true.
I think you'll find it is! Try superposition of forces.We've already done that strawman, elf.
Posted 7 months ago # -
Is it panto season already?
He's behind you!
Posted 7 months ago # -
Imagine a structure with no stength in tension and lots of strength in compression (the opposite of a spoke in this example, a wall) with no cement.
Normaly the wall is fine. The forces act directly through the middle of it.
Push on it and the imaginary line the force travels down moves towards the edge. Once it gets about 2/3 of the way accross the wall falls over as 1/3 +1/3 either side of the line is in compression, but the 1/3 furthest from the line is in tension, and falls appart. This also applies to loading the top of the wall, if you put an off center weight on the wall it will fall over even if the COG is within the wall itself.
To counteract this dams and other structures can have steel tie rods/cables tensioning them top to bottom to keep back the water. This does the job of the spokes in the wheel.
Posted 7 months ago # -
Surely a spoke that is barely under any tension has more of it's elastic range available;
it will elongate (allowing the wheel to deform) under a lesser load than a spoke which has a higher pre-tensioning, which will require higher loads toachieve the same deformation (higher loading meaning a podgier IT manager)...
Posted 7 months ago # -
Posted 7 months ago #
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Surely a spoke that is barely under any tension has more of it's elastic range available;
it will elongate (allowing the wheel to deform) under a lesser load than a spoke which has a higher pre-tensioning, which will require higher loads toachieve the same deformation (higher loading meaning a podgier IT manager)...
No. As suggested above, look up superposition of forces.Posted 7 months ago # -
To counteract this dams and other structures can have steel tie rods/cables tensioning them top to bottom to keep back the water. This does the job of the spokes in the wheel.
Except a wheel isn't a dam - though to be fair it's not a bad analogy. Increasing the tension in the steel ties in a dam doesn't increase the stiffness of that either - it just increases the maximum load.Posted 7 months ago # -
Yep, he says
"If spokes are tighter initially, then the sudden increase in flexibility shown in data points 9 and 10 is less likely to occur in use because a tighter wheel can bear a higher load before spokes become slack."
(where 9&10 show a large deflection, 1-8 don't).
I.e tighter spokes = less deflection.
It doesn't obey Hookes law, but it does show a deflection for a given weight can be shown Vs initial tension. It's just a modulous that relies on 3 variables (force, initial tension and deflection).
Posted 7 months ago # -
"If spokes are tighter initially, then the sudden increase in flexibility shown in data points 9 and 10 is less likely to occur in use because a tighter wheel can bear a higher load before spokes become slack."
<sigh> - we're not talking about what happens when the spokes become completely slack! His first statement is:
"Some believe that a wheel built with tighter spokes is stiffer. It is not. Wheel stiffness does not vary significantly with spoke tension unless a spoke becomes totally slack."Posted 7 months ago # -
Depends whether 'significantly' is detectable by humans after you've stuck a nice squishy tyre on I suppose,
Posted 7 months ago # -
Yes, but you're telling me you've never ridden a bike with spokes that are tight (but not very tight), and it felt horrible, then added 1/4 to 1/2 turn to each spoke? to improve them?
My shimano facotry wheels on the road bike needed a half turn to stop the rear rubbing on the brake blocks while climbing out of the saddle. They 'felt' different afterwards too, but the brake blocks show it's not a placebo.
we're not talking about what happens when the spokes become completely slack!
You aren't, I am. Because thats where the difference is.
Posted 7 months ago # -
i'm not sure i understand.
a loose spoke means 'not stiff wheel'. tight spoke means stiff wheel but tighter spoke does not equate tighter wheel.
There is a threshold limit of tightness where it becomes stiff and no stiffer?
Posted 7 months ago # -
Really, who gives a sh*t.
Posted 7 months ago # -
a loose spoke means 'not stiff wheel'. tight spoke means stiff wheel but tighter spoke does not equate tighter wheel.
There is a threshold limit of tightness where it becomes stiff and no stiffer?
Errrr kinda, the "tight" and "very tight" (lets ignore completely loose spokes for now), both have (aproximately) the same stiffness up untill the point where you load them past the point where half the spokes go slack. Beyond this the stiffness drops off massively.
The point is a tighter wheel takes more load to reach this point. So the "very tight" set of wheels won't deflect during a hard corner, landing a jump or hittig a rock where the "tight" wheels MIGHT deform IF the force is grat enough to slacken off a proportion of the spokes.
Posted 7 months ago # -
All I know is that I once had a bike (04 Stumpy FSR) that was feeling a bit wobbly on the back end in fast corners and that by retensionning the rear wheel it improved dramatically. That was only about 1-1.5 turns on each spoke nipple to achieve that noticeable difference.
Explain away..........!
Posted 7 months ago # -
@ thomthumb
yes, tightening the spokes will increase the rigidity of the wheel, but only up to a certain point (whatever value that point may be)
If you turn the nipples 3 times more, it will not increase the stiffness of the wheel (technically it may on paper, but certainly not noticable to the rider)
Posted 7 months ago # -
Yes, but you're telling me you've never ridden a bike with spokes that are tight (but not very tight), and it felt horrible, then added 1/4 to 1/2 turn to each spoke? to improve them?
Apart from the very first set of wheels I built which disassembled themselves on the first ride, no. Only badly built wheels do that.You aren't, I am. Because thats where the difference is.
But that difference is one of strength, not one of stiffness - the amount of force required to make a spoke slack is very little less than the amount of force required to buckle a wheel. The normal measure of stiffness of wheels is when the spokes haven't gone slack - try re-reading that article I linked, and you'll see there are significant differences in stiffness between different wheels without spokes going slack.Posted 7 months ago # -
pedant of the week award goes to...
Posted 7 months ago #
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