Hi-Mod frame vs non-himod ? Different frame quality ?

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Hexsense
Posts: 3269
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Location: USA

by Hexsense

gewichtweenie wrote:Seen an old magazine comparing steel makers who crafted 7 variants of a model using different tubing. differences were minimal.

Here's a similar one by Josh Poertner

http://www.slowtwitch.com/Tech/Thoughts ... _4571.html

That is Steel, metal, which is Isotropic material. So their stiffness of material are equal in any direction (but tubing make it different, however)

Carbon is Anisotropic material. Each layer of sheet is only strong in a direction it design for. So it would give very differrent result if we change the test from tube shaping of steel to tube shaping and lay-up of carbon.

a video of the subject with real carbon example
www.youtube.com/watch?v=_4ALUyrTe90

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gewichtweenie
Posts: 152
Joined: Fri Sep 25, 2015 3:12 pm

by gewichtweenie

Hexsense wrote:
gewichtweenie wrote:Seen an old magazine comparing steel makers who crafted 7 variants of a model using different tubing. differences were minimal.

Here's a similar one by Josh Poertner

http://www.slowtwitch.com/Tech/Thoughts ... _4571.html

That is Steel, metal, which is Isotropic material. So their stiffness of material are equal in any direction (but tubing make it different, however)

Carbon is Anisotropic material. Each layer of sheet is only strong in a direction it design for. So it would give very differrent result if we change the test from tube shaping of steel to tube shaping and lay-up of carbon.

a video of the subject with real carbon example
http://www.youtube.com/watch?v=_4ALUyrTe90


But bikes aren't made from single ply (=sheet) of carbon and the forces aren't aligned to the principle axes , meaning the anisotropy isn't fully exploited. The primary control in characteristic still being general tubing dimension and shape.

The real point being that unless a manufacturer truly and fully gimps 1 variant of their bike from the same mould (like, say, putting jello suspension, 14" tires, and 150hp motor on a porsche,), there is way more marketing value in saying "we used the best carbon in the best orientation in the best places" than there is in real appreciable differences.

Hexsense
Posts: 3269
Joined: Wed Dec 30, 2015 12:41 am
Location: USA

by Hexsense

gewichtweenie wrote:But bikes aren't made from single ply (=sheet) of carbon and the forces aren't aligned to the principle axes , meaning the anisotropy isn't fully exploited. The primary control in characteristic still being general tubing dimension and shape.

The real point being that unless a manufacturer truly and fully gimps 1 variant of their bike from the same mould (like, say, putting jello suspension, 14" tires, and 150hp motor on a porsche,), there is way more marketing value in saying "we used the best carbon in the best orientation in the best places" than there is in real appreciable differences.

what?
did you watch the video i posted?
for fork as an example, if i use purely 45 degree carbon sheet in the video it would be very tortional stiff (won't rotate) but can flex forward and backward quite a lot.
In another extreme, if i use purely straight 90 degree going down carbon. it will not flex forward and backward but it can twist which is obviously bad.

Real fork will not make from single type of sheet of carbon, but how much of each type and where would it place will dictate how it perform even if it has the same shape.

Then stem is another very good example in other way.
Stem require stiffness in all direction so making a carbon stem will require quite a lot of carbon sheets in different directions that it will not be any lighter than aluminium stem. Unlike other place of the bike where designer can tune stiffness in only some way and leave it to flex in other and also save weight by doing so, Carbon stem only improve aesthetic as it can be made to look real cool easier.

gewichtweenie
Posts: 152
Joined: Fri Sep 25, 2015 3:12 pm

by gewichtweenie

Hexsense wrote:[
what?
did you watch the video i posted?
for fork as an example, if i use purely 45 degree carbon sheet in the video it would be very tortional stiff (won't rotate) but can flex forward and backward quite a lot.
In another extreme, if i use purely straight 90 degree going down carbon. it will not flex forward and backward but it can twist which is obviously bad.

Real fork will not make from single type of sheet of carbon, but how much of each type and where would it place will dictate how it perform even if it has the same shape.

.




Respectfully, acknowledgement of elementary material science should already have been shelved in this discussion.

As said before, a bike isn't built from a single strand of fiber or a plane of plies. It is a large'ish cylinder of fair thickness from many plies, with diverse stress vectors. Bending a simple bar of carbon as a demonstration serves only to exaggerate.

For example if you had to fill a mould of a beefy zipp stem with random sheets of commercial CF like t700 vs t800 vs t1000.... The end result wouldn't be much different than a layup resulting from 1000s of runs of FEA.

So back to the point, of a frame of same dimension, where both share the same conditions and target characteristics -- say a supersix vs supersix hm.....Unless the manufacturer willfully makes major sacrifices to that one weighs half or double the other , then their result will be very much the same.

Hexsense
Posts: 3269
Joined: Wed Dec 30, 2015 12:41 am
Location: USA

by Hexsense

gewichtweenie wrote:
For example if you had to fill a mould of a beefy zipp stem with random sheets of commercial CF like t700 vs t800 vs t1000.... The end result wouldn't be much different than a layup resulting from 1000s of runs of FEA.

So back to the point, of a frame of same dimension, where both share the same conditions and target characteristics -- say a supersix vs supersix hm.....Unless the manufacturer willfully makes major sacrifices to that one weighs half or double the other , then their result will be very much the same.

Yeap, making a stem with carbon is like creating a tube material that require Isotropic property with an Anisotropic material. It need a lot of random direction to make it stiff in any direction. Grade of carbon doesn't have anything to do with this (lower stiffness carbon are heavier and thicker for the same stiffness of course). It's pretty much only shaping that matter, just like steel.

But other parts of the bike is not like that though, Tube shaping can be the same but internally it can use different mix of carbon layup (not necessary grade of carbon, just mixture ratio of different angle carbon sheet is enough, seat tube doesn't need much of twisting stiffness, chain stay can be made to completely stiff in all direction or only torsional stiff but can flex up and down for comfort etc. ). And ride different, as i give an exaggerated fork example above. My point is only about that you talking about different in ride is minimal between tube shaping of steel so assume the same for carbon, which is not that simple and safe to assume. It has tube shaping and also lay-up as another factor to make difference in ride quality. But whatever, go back to thread 8)

cyclotripper
Posts: 19
Joined: Tue Jul 18, 2017 10:19 am

by cyclotripper

Anyone ridden both the hi-mod and standard current System six? the price differential seems huge. The ultegra model same price as hi mod frame alone. Is the ho\i mod really worth it? any thoughts? Real-world experience?

Noctiluxx
Posts: 1336
Joined: Tue Feb 07, 2017 7:17 pm
Location: Southern California

by Noctiluxx

uraz wrote:
Thu Apr 13, 2017 2:40 pm
TheKaiser wrote:When it comes to the Cannondale SS bikes from about 4-5 years ago, the higher end ones were less torsionally stiff, both in terms of pedaling and front triangle "steering" stiffness, than the regular ones:
https://cycletechreview.com/2012/media/ ... -bicycles/
Ignoring the fact that this is a marketing material from giant (just look what they have done to make TCR "lighter" than SS Evo) they are comparing 2 totally different super six's (evo and "before evo" model) - not hi-mod and non hi-mod. Actually you can't even tell if they used hi-mod or non hi-mod cannondales.

Relying purely on weight I'd guess that it was evo hi-mod and non evo non hi-mod.

For me the most important aspect of a bike is how it feels, how it corners and how it brakes. Don't get me wrong, wats savings and drag coefficient are also important but mostly when doing TT. If you pay too much attention making bike "fast" you will lose in joy and rideability department.

I have swapped frameset in my bike 2 times (from non hi-mod ss to hi-mod ss and from non hi-mod evo to hi-mod evo) and believe me I could feel the difference right away.

I believe those results came from Tour magaine.
Bianchi Oltre XR4, De Rosa SK Pininfarina, Trek Madone SLR, Giant TCR Advanced SL, Cervelo R5 Disk, Giant Revolt

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