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PostPosted: Mon Mar 13, 2017 3:36 am 
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Sorry for reviving an old topic but I would like to clear up one thing with your help...

I've never ridden a low weight titanium spoked or low weight stainless steel spoked wheel so I can't say much on the perceived properties of any of them. (Currently on bitex + kinlin xr200 + dt comp 2.0 20/24h ~ 1320gr. I'm 64kg).

Looking at the tension graphs (Pillar homepage) though I can see that thin ss spokes and more common titanium spokes have a very long range of elasticity or elongation (or what the hell you call it). Some spokes reach their highest tension at 7 mm which by comparison to what we commonly call "reliable" spokes is many times larger. I believe common dt/sapim spokes reach their maximum tension at around 2.5-3mm.

Ok so here comes my question. Looking at the graphs on Pillars homepage both the PST14 standard titanium and the TiAero middle class titanium spoke can't rival the more common steel spokes BUT looking at pillars highest end titanium spoke, the X-Tra Lite Ti (also the lightest), it's graph quite resembles the graph of a good ss spoke. I'm looking at 250plus kgf at around 2.5mm elongation.

What do you think of this and is it fake?

Still the lightest extralite climbing wheels at like 785gr/set still seem to use ss spokes (pillar megalite? - which similarly to X-TraLiteTi also reaches high tension with low elongation, maybe because of the special alloy?)

Why do you think that is? Any input is appreciated! :D

Cheers and thank you for reading /a

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Last edited by alcatraz on Fri Mar 17, 2017 2:47 am, edited 3 times in total.

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PostPosted: Mon Mar 13, 2017 1:58 pm 
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I have no knowledge of the spokes you mention. Only that the modulus of elasticity for titanium can only vary by a few percentage points for various alloys, and that it is always roughly half that of steel. So for a given cross section, the titanium spoke will require twice as much elongation to reach the same tension. What that also means is that the spring rate of titan is half that of steel, so the wheel will be more flexible. Bottom line, lightness of the wheel is less important than the durability and predictability of the handling of the wheel (within reasonable limits, of course). I think you are better off building sapim cx-ray on light carbon rims if you want light wheels.


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Posted: Mon Mar 13, 2017 1:58 pm 


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PostPosted: Mon Mar 13, 2017 3:14 pm 
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Would be cool to hear from a ww that has tried the Pillar X-Tra Lite Ti spokes. I suspect donald is using them....

Still only a subjective review but can be interesting nontheless.

/a


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PostPosted: Mon Mar 13, 2017 6:08 pm 
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not really a review on the spokes mentioned, but I had a cane creek 700c wheelset with Ti spokes before, on a Ti bike.

The combo was a comfortable ride. When I update my ride to a carbon frame with low-to-mid Mavic wheels, I found much better power transfer from pedal to forward motion. Sadly, I am not able to isolate if it was the frame or wheel or combination of both.

My wheelset with ti spokes didn't give me any trouble and stayed true.


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PostPosted: Tue Mar 14, 2017 1:16 am 
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Thanks for the replies. Yes stockae92 that seems to be the general experience with titanium spokes when I read the Ti threads/posts.

Spud has a point that no matter the alloy variation, properties shouldn't be able to change too much. Comparing the graphs of (thicker) standard pillar ti spoke to the ultralight (thinner) X-TraLiteTi the latter appears to be twice as resiliant to elongation.

I don't know if it relates but the Pillar Megalite (reminds of Sapim super spoke) at 3.5gr steel and an extremely thin cross section still manages to outperform standard steel alloy Pillar spokes, that are thicker, by many times.

So if spud's comment on alloys being similar is true then these megalite/super spokes must have exaggerated specifications.

What do you think? Can titanium alloys vary as much as steel alloys and is it all simply not true what the manufacturers are promising?

Anyone tried super spokes/megalite?

/a

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PostPosted: Fri Mar 17, 2017 2:46 am 
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Pillar X-TRA Lite Ti spokes - has anyone tried them?

If you have tried them, would you consider them again for a future wheelset? Would you prefer to go back to Ss spokes?

If someone has tried Sapim Super Spokes or Pillar Megalite, what is your opinion on them? Would you use them again?

/a


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PostPosted: Sat Mar 18, 2017 4:39 am 
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alcatraz wrote:
Spud has a point that no matter the alloy variation, properties shouldn't be able to change too much. Comparing the graphs of (thicker) standard pillar ti spoke to the ultralight (thinner) X-TraLiteTi the latter appears to be twice as resiliant to elongation.

I don't know if it relates but the Pillar Megalite (reminds of Sapim super spoke) at 3.5gr steel and an extremely thin cross section still manages to outperform standard steel alloy Pillar spokes, that are thicker, by many times.

So if spud's comment on alloys being similar is true then these megalite/super spokes must have exaggerated specifications.

What do you think? Can titanium alloys vary as much as steel alloys and is it all simply not true what the manufacturers are promising?


That is also my understanding of the various alloys, both Ti and Steel, in that the various alloys do not vary significantly in modulus of elasticity. Because of that, a round spoke steel with twice the cross sectional area of another round steel spoke will be twice as "stiff" and resistant to elongation. Interestingly, since this is related to cross sectional area, the same thing goes for non round spoke shapes, so a Sapim Laser, which is round, should have the same resistance to elongation as a Sapim CX-ray, which is bladed. My understanding is that the CX-ray is basically just a Laser which has been squished flat, and the only real advantage should be slightly reduced aero drag, however if you look at some of the published stats from Sapim they quote the CX-ray and the even thinner Super Spoke as having very different elongation properties to all their other steel spokes. From my laymen's understanding, this isn't supported by any outside data sources, and while those spokes may be more work hardened they shouldn't be dramatically more "stiff".


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PostPosted: Sat Mar 18, 2017 3:12 pm 
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I don't think the problem is the ultimate tensile strength of ti spokes. It's the stiffness and fatigue that is less good than steel.


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PostPosted: Sat Mar 18, 2017 6:25 pm 
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F45 wrote:
I don't think the problem is the ultimate tensile strength of ti spokes. It's the stiffness and fatigue that is less good than steel.


Yes, and with Ti spokes, to achieve the same stiffness as a steel spoked wheel, you would either need to run more spokes or thicker spokes, which will essentially negate the weight savings, and be slightly worse aerodynamically. The Ti spokes would only be advantageous in a situation where you wanted to go even lighter than the lightest steel spokes, and were willing to accept the reduction in wheel stiffness. If the figures I have seen are right, these Pillar X-Tra Lites save about 1g per spoke vs. Super Spokes, which is close to a 30% reduction in spoke weight, so I would have to imagine the reduction in stiffness would be pretty significant.


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PostPosted: Mon Mar 20, 2017 2:23 am 
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What about super spokes / megalite (ss 3.5g) vs thicker ss spokes?

Are they in a class of their own? Or are they just there for wheelbuilders trying to set a weight record at the expense of wheel quality?

Looking at the big brands high end wheels like Bora 50 and so on. Seems they mostly run like cx-ray "medium sized bladed" type ss spokes. They don't go under a certain size.

Would you agree that this is the sweet spot for a performance conscious weight weenie today? I guess it's all a subjective gray area (rider weight,use) but still I'd like to know your opinions.

/a


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PostPosted: Wed Mar 22, 2017 8:54 pm 
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We can extract data from the X-tra Lite Ti information to check if it is valid. The titanium probably has a modulus of elasticity (stiffness) of 114 GPa. I'm estimating the cross section to have an area of 1.71 mm^2. The information isn't clear since it lists a width of 2mm, but a "spoke profile" of 1.45mm. I went with 2mm, less a little to account for the rounded ends on the cross-section. From the force/deflection graph we can estimate that yield is occurring at 245kgf with a deformation of 2.4mm. This equates to a stress of 1406 MPa (seems a little high - most titaniums I'm familiar with don't go above 1000 MPa for yield). Using E=114 GPa we can extrapolate a spoke length of 195mm. This seems reasonable. So, I think the information they've presented is valid.

Deflection of a spoke can be calculated using the formula: deflection = (F*L)/(A*E)
Higher force gives more deflection. Longer spoke gives more deflection. Increasing the cross sectional area, or the Modulus of Elasticity gives you less deflection. So, as stated above, the only way to compensate for titanium's lower E is to increase the cross-sectional area of the spoke. If you don't, then you get a more flexible spoke that will require more turns of the nipple to get it up to tension.


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PostPosted: Thu Mar 23, 2017 6:21 am 
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Qman wrote:
We can extract data...


Thank you very much for your educated analysis.

Do you have any theory why the thicker titanium spokes (Pillar homepage) show a longer elongation at same tension as these?

Do you believe that differences in alloys alone can account for this difference?

/a


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PostPosted: Thu Mar 23, 2017 10:02 pm 
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Looking at the standard Ti spoke graph on the Pillar website, then we see that the deformations do indeed look longer. From the Breaking Strength graph I would guess that yield is happening at about 240kg with 3.6mm elongation. The cross-sectional area is 3.14mm^2, which is double that of the X-tra Lite. The yield stress then works out to 750MPa, much lower than the other spoke. If we assume a 200mm spoke length then I get a Modulus of Elasticity of 41.7GPa. Titanium alloys are usually 100GPa to 114GPa, so this seems very unlikely. If they tested it with the longest possible spoke, 310mm, then I get an E of 64.6GPa. Closer, but still too low. If I choose a lower yield point (it is very much a guess based on eyeballing their graph), then I will get a slightly higher value for E, but still nowhere near 100 GPa. The graph for the Standard Ti spoke doesn't seem possible. Either the graph is in error, or I'm missing something!


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PostPosted: Thu Mar 23, 2017 10:21 pm 
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One further thought: There would be a difference if you test a j-spoke vs. a straight pull spoke. The J-spoke should deflect more. If the X-tra Lite was tested as a straight pull, and the Standard was tested as a J, then it could account for some of what we're seeing. I would also expect the Load vs Deflection graph to look different for a J - it would start out flatter, then get steeper. I'd need to do a full analysis on both to find out. It would be fun to do, but I don't have time right now...


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PostPosted: Fri Mar 24, 2017 3:18 am 
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Thank you very much Qman. Have a break. You've demonstrated some interesting differences.

I'm still leaning towards the explanation that the graphs must be false.

Now if only someone who has actually tried the spokes could shine a bit of light would be awesome.

I'm pretty sure "donald" uses these spokes. 16/20 configuration wheelset OMG. :D


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Posted: Fri Mar 24, 2017 3:18 am 


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