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"[i]How so?[/i]"
Well in a dished wheel with an equal number of spokes on each side, clearly the NDS spokes are only carrying something like a half of the tension of those in the DS. And low tension is the main cause of fatigue failures. A radial spoke will only ever gain tension under torque (and nowhere near enough to trouble the yield strength - remember it's starting from a low stress), so you never get spokes dropping to low tensions and the theory goes that they're more durable accordingly.
It's the first wheel I've built that way (I did once build one 3x/1x because I couldn't find any shorter spokes, but I sold the bike it was on before I put many miles on it) so we'll see.
"[i]the lateral drag on the wheel from being in a 30mph wind (which could be done without it spinning)[/i]"
Er... surely it couldn't. Well, it could, but only if you wanted totally useless numbers. You wouldn't try and figure out the effects of a crosswind on a helicopter without its blades rotating.
Interesting....but 3x spokes NDS are also under lower tension than DS, and radials will be even lower, perhaps to the point that allows the the peak tension to get higher*, which could cause problems?
*Isn't it the case that, up to a certain point, the higher the overall tension on an (evenly tensioned) wheel is, the lower the individual tension on each spoke can be under stress?
Bez - Member
You wouldn't try and figure out the effects of a crosswind on a helicopter without its blades rotating.
I hear Zipp are launching a helicopter line with amazing lateral drag figures 😉
Actually that's quite different - blades rotating in the direction of the wind - Zipp's wheels are (or should be) rotating in the plane perpendicular to the wind.
Iain - fair point (if you are actually right) but the point about light wheels is they feel light and fast - most folk going out for a ride are more concerned about enjoyment than doing it a few seconds more quickly (I think that's what we're talking about here?) and....if racing...is there any research on how much oif an aero benefit is lost when riding in the group?
I was looking at it from the view, if you want the "best" (which I took to mean fastest as when on the road on your own what else are you looking for?) I personally wouldn't consider weight to be my first or second priority. For a road bike stiffness would be my primary concern, aerodynamics my second and weight my third. I would look to get the stiffest for the budget then make concessions based on the other two. IMO compromising stiffness for weight is pointless as you'll loose more power through the lack of stiffness than the lack of weight will save (and yes light wheels are fun as long as they aren't flexy,flexy wheels are really irritating.) The point I'm trying to make with all my posts are, if you have a limited budget get nice stiff wheels, if you have slightly more cash get nice stiff wheels with deep rims, if you are loaded get nice stiff wheels with deep rims that don't weigh much. There are obviously conditions to this if the 20mm planet x rims build up to a nice stiff wheel for 1350g for under £300.00 then it's a bargain despite not being aero but I had the choice between them and some second hand Sram S40's or Mavic Cosmics I would get one of the latter as 9 times out of 10 it will be faster.
I've only looked at tunnel data comparing frames, wheels etc and tbh as with weight the bike matters very little compared to the rider, and in a bunch aerodynamics matters less so. That said if I was buying a set of wheels just to do crit races they would be Sram s80's which are a popular choice for the lads at the sharp end at the races I turn up to along with skinsuits. Whilst it's less of a consideration in the bunch, there are plenty of times you are not in the bunch and they are the times you want every advantage going, whether sprinting or on an attack.
Iain
Indeed - not everyone will share that starting point! I want my road bike to feel light, and a bit of flex if fine, as comfort is important too. I don't race but do have the odd pop at the local chain gang.
IMO compromising stiffness for weight is pointless as [u]you'll loose more power through the lack of stiffness than the lack of weight will save[/u]
DO you know that bit to be fact or is it just your opinion?*
Whilst it's less of a consideration in the bunch, there are plenty of times you are not in the bunch and they are the times you want every advantage going, whether sprinting or on an attack.
Easy to argue that both ways when there is little/no data - like * above.
Slight hijack - anyone got any experience of using 'fat' rims like the velocity A23?
http://www.wheelbuilder.com/store/velocity-a23-clincher-rim.html
I'm a bigger chap riding a defy carbon and i built some pro3's on to open pros. They came up at a shade over 1600grams and cost me about £300 (top deal on a rear hub) 28/28 with 2X sapim DB spokes.
I've been really please with them, stiff, spin up well, they look the dogs, and a horse scarer free hub.
"[i]Interesting....but 3x spokes NDS are also under lower tension than DS, and radials will be even lower, perhaps to the point that allows the the peak tension to get higher*, which could cause problems? [/i]"
I think the only way the peak tension would get higher in a half-radial rear would be in the drive side trailing spokes, which may carry a bit more tension under torque, that might otherwise be picked up by the trailing NDS spokes. Though I'm sceptical of that. And it may depend on hub shell stiffness. To be honest, I don't know. I suspect it's not large enough an effect to be an issue, but I've not even troubled a back of an envelope in arriving at that hypothesis, let alone a calculator or an FEA box 🙂
"[i]Actually that's quite different - blades rotating in the direction of the wind - Zipp's wheels are (or should be) rotating in the plane perpendicular to the wind. [/i]"
Well it depends what the OP meant by "lateral". But crosswinds on helicopter blades seems like the same orientation as a headwind on a bicycle wheel to me... Obviously there are a bazillion other ways that the analogy massively falls down, but hey, that's what analogies are for 🙂 ...Use the analogy of someone pissing on a millstone if you like - point is, flow over a spinning object is completely different to flow over a static object. Anyone who disagrees should go and play with a frisbee 🙂
There are obviously conditions to this if the 20mm planet x rims build up to a nice stiff wheel for 1350g for under £300.00 then it's a bargain despite not being aero
If using their 20mm rims you could easily be sub-1100g for that. You could use their their (or eBay Gigantex) 50mm rims and only give away 200g, so 50mm deeps at 1300g for less than £300. If/when I change to a different power meter I'm tempted to give that a try! While I'm using a PowerTap I don't much fancy a carbon tub rim for my Central London commute!
Anecdotally... I had some 1600g Bontrager Aeolus 5.0 clinchers. With the tyres and tubes I used they were exactly the same weight as the aluminium 23mm Race X Lites they replaced. On the flat and down hill they were very good indeed, but uphill they were a proper slog due (I assume) to the not insignificant additional mass at the rim. I sold them after 6 months or so, I'd not rush to buy some aero rims that were no lighter than a 'normal' shallow rim personally.
cynic-al - Member
Indeed - not everyone will share that starting point! I want my road bike to feel light, and a bit of flex if fine, as comfort is important too. I don't race but do have the odd pop at the local chain gang.IMO compromising stiffness for weight is pointless as you'll loose more power through the lack of stiffness than the lack of weight will save
DO you know that bit to be fact or is it just your opinion?*Whilst it's less of a consideration in the bunch, there are plenty of times you are not in the bunch and they are the times you want every advantage going, whether sprinting or on an attack.
Easy to argue that both ways when there is little/no data - like * above.
The big IMO at the front of the first sentence along with "I personally" at the top would be hinting that it's all my opinion. I only gave one fact which was Zipps are the most aerodynamic wheels you can buy. You could calculate the power lost due to flex and plot it against the reduction in power needed for a given weight loss for a particular wheel, but obviously I haven't bothered. "Facts" seem to be at the forefront of everyone's thoughts on the matter but not many are available as it's quite subjective. Too many factors come in to play to do controlled testing of any "real" value (i.e tests that would answer your questions fully, are aerodynamics more important than an X-gram weight saving in the bunch etc) If you are coming at the problem afresh you're best off defining it (what do you want? I've come at it from a "largest power saving per pound" perspective) looking at all the information available, seeing what other people use (Trends across pro teams are a good place to start), gathering thoughts from your own experiences and formulating your own opinion. That's what I have done and it is 1. Stiffness 2. Aero 3. Weight. One could delve deeper into the problem and do your own testing but why bother? I feel my conclusion answers all of my needs so no need to go further.
Iain
From that Velocity rim link:
The A23 has been described as a "Clinchular" because it has all the benefits of a tubular tire (smooth ride quality, lower rolling resistance) with the convenience of a clincher tire (ease of installation, easy to repair a flat, low cost).
BS OF TEH WEAK!
Bez - Member
I think the only way the peak tension would get higher in a half-radial rear would be in the drive side trailing spokes, which may carry a bit more tension under torque, that might otherwise be picked up by the trailing NDS spokes. Though I'm sceptical of that. And it may depend on hub shell stiffness. To be honest, I don't know. I suspect it's not large enough an effect to be an issue, but I've not even troubled a back of an envelope in arriving at that hypothesis, let alone a calculator or an FEA box
I don't think you've got my argument...the * bit?. I too doubt the effect of pedalling torque on spoke tension will matter a jot to any radial spoke, but it and moreso effects of braking.
Frisbee - isn't it that the rotation and ensuing angular momentum/gyroscopic effect keeps it steady?
Iain - fair enough - it wasn't clear that both parts of your previous sentence were IMO or not.
seeing what other people use (Trends across pro teams are a good place to start)
I [i]always[/i] say this - they are paid to ride bikes, they are also subjective and irrational in the choices they are allowed to make (eg Kelly running straps for years after everyone was on clips). Not to say what they are riding isn't the fastest, but it is also about marketing and sales.
Thanks for reading if you've got this far...at the heart of my posts here is the argument that a bike that feels light/comfortable makes me smile, that's what I cant, IDGAS about 2s off the commute etc. Light weight achieves this, and has been proven not to affect speed that much, as aerodynamics appear to.
Thing is we appear to judge the effect (affect? I give up) of lightness as more significant than it is.
Firstly for someone new to light road wheels sorry for resurrecting this thread.
Can someone explain this further
There are obviously conditions to this if the 20mm planet x rims build up to a nice stiff wheel for 1350g for under £300.00 then it's a bargain despite not being aero
What hubs, where from and who builds these for you to get it all in under 300?
Im looking at RS80 -c24 at the moment.
Thos hubs I linked to min my first post, planet x rims, buy your spokes from somewhere and build them yourself.
they would look like Taco's of i did them. 🙁
Will take a look at those hubs ta
Get on eBay and search "6 pawl hubs", there's loads for about £80 a pair. Planet X rims are £100 each, although they've done a number of deals bringing them down to £80, alternatively again seach eBay.
Revolution spokes from Action sports come to about £40 or so, et voila.
You need to build them yourself/find a local builder.
they would look like Taco's of i did them.
Why?