Originally Posted by
Alias530
I'm not resisting it, I'm just trying to sort out the point at which I'm underbuilding the wheel. I've accepted that Lasers are too light duty. I'm trying to sort out whether Sapim's process to turn a Laser into a CX Ray will allow me to use a lightweight spoke that is also strong, by paying more for it.
I've always been under the school of thought that out of strong, light, and cheap, you could to pick two. I'm picking strong and light. That's what the CX Rays seem to be. I'm just trying to make it clear that if their benefit is aero, NOT strength, that I'll go with something else. I just don't want to turn a 1,500g wheelset into a 1,700g wheelset by overbuilding it, because the benefits compared to what I already have will disappear.
You are really over-thinking this. You can easily do the math to determine how much more or less a spoke weighs based on it's diameter. Calculate the cross sectional area and multiply by the length to get the volume of steel that is used. Then divide by the density of the steel...8g/cubic centimeter... and that will give you the weight per spoke. But, honestly, the weight difference between spokes is going to be minimal. You aren't going to gain 200g/wheel by going to a slightly heavier spoke. As I said above, the difference is on the order 2.5mg/spoke for a heavier head. You have to do something else to the wheel to gain 200g.
Honestly, it's tough to lose 200g of weight on a wheel. I recently built a wheelset that lost 2 lb (about 1000g) on both wheels but that's with a light rim (Velocity A23) and light hubs (White Industries T11). A good chunk of the weight savings came from the titanium freehub body.
Originally Posted by
chaadster
Yes, I understood all that, I just question how you know it. How are you sure the forging is wasted strength?
As I said before, and which you have not addressed, is that it stands to reason that the forging process brings about behavioral changes throughout the spoke. The shaping and metallurgy changes will impact the way stresses are distributed and the way the spoke moves and transmits vibration.
I don't know what the answers are, and I'm not saying you're wrong, just that my base for trust on these matters are the manufacturers, the folks who've presumably done modeling and testing of spokes, though a critical questioning of that base trust by some dude in an internet chat room could be compelling were it comprehensive and supported with some facts or other evidence.
Certainly your basic question is valid-- does spoke body forging provide practical strength?"-- but I just don't see any rational reason to answer in the negative. It may be that forging does nothing for strength at the J bend, and the manufacturers are referencing other elements of spoke performance as stronger, but I'd just like to hear a little more before tossing out their strength claims as meaningless or irrelevant.
The forging that is being done to the CX Ray spoke is only in the middle. Nothing is done to the head of the spoke over what is done to other spokes. Forging and working only have an effect at the site where the forging occurs.
Originally Posted by
chaadster
That's exactly the claim that I challenge.
This discussion is formed around the idea that strength only refers to J bend fatigue, which is erroneous. The entire spoke is forged anyway, so really it's the way that the additional shaping and increased density of forged aero section spokes affects overall performance that's the issue, not a matter of forged vs. non-forged.
There are many types of forces that impact spoke performance, and increased strength can manifest in other areas than the elbow. Reducing the intensity of stresses that the elbow sees is a way to increase fatigue life without changing the fatigue limit of the metal at the bend itself.
Spokes aren't "forged". They are drawn from wire stock. Sapim goes a bit further and makes the middle of the spoke oval by compressing the spoke. If anything the ovalization of the spoke may increase stiffness which translates into more force being put on the head. The spoke may be less elastic than a traditional double butted spoke.
Originally Posted by
FBinNY
Unless Sapim somehow works the elbow differently than they do with all their other spokes, there won't be any difference in these elbows as compared to all the others. More cold work in the center of the spoke doesn't magically change the elbows.
Exactly.
And when FB and I agree on something, you should take it as a miracle...a Christmas miracle if you like
