eeWings, Craig and Cane Creek's revived Sweetwings

Discuss light weight issues concerning mountain bikes & parts.

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FreaK
Posts: 840
Joined: Sat Aug 27, 2005 5:57 am
Location: mOntreal

by FreaK

Sort of.
400g
Sram direct chaining mount
Hirth joint
3al2.5v arms, 6al4v spindle and bosses
https://m.pinkbike.com/news/cane-creek- ... -look.html
Image
Should be easier to get a set than Propellers, as my local Cane Creek distro has listed it on their b2b already and apparently the first production run is sold out nearly entirely to distributors.
My opinion:
They're nearly the exact crank I would build if I were in a position to do so.
Last edited by FreaK on Wed Apr 18, 2018 11:52 pm, edited 1 time in total.
it's actually possible to come to the conclusion even before realising it makes no sense at all
-
tymon_tm

glam2deaf
Posts: 691
Joined: Mon Apr 27, 2015 4:36 am

by glam2deaf

These are stunning. Hoping for a road version asap!

by Weenie


Marin
Posts: 2819
Joined: Wed Jan 22, 2014 11:48 am
Location: Vienna Austria

by Marin

Hoping for a *steel* road BSA version!

C36
Posts: 252
Joined: Fri Mar 03, 2017 3:24 am

by C36

Appreciate the originality but it can't be competitive in terms of stiffness to weight ratio. In flexion and torsion Titanium Young modulus and density are clear on this matter And don't see any design change that would compensate this.
Anticipating comments:
- Ti aloys have little stiffness variation then it can't compensate material limitations.
- stiffness do matter, flex at one point of the pedal stroke is not usable to "spin" the cranks at the end of the stroke.
Now I can't deny it is a beautiful product.
Edit: reacted as road cyclist, just realised it is the MTB forum... the impact resistance claimed could be a plus but the welds represent a weaker point so...


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FreaK
Posts: 840
Joined: Sat Aug 27, 2005 5:57 am
Location: mOntreal

by FreaK

I suspect the reason it's taken so goddamn long for a 'mainstream' version has been because there's a known issue around welded ti cranks.
I suspect the crossection of the arms is plenty to compensate for material choice. They are very very chunky. In steel they would obviously be far stiffer.
Last edited by FreaK on Wed Apr 18, 2018 11:46 pm, edited 1 time in total.
it's actually possible to come to the conclusion even before realising it makes no sense at all
-
tymon_tm

C36
Posts: 252
Joined: Fri Mar 03, 2017 3:24 am

by C36

FreaK wrote:I suspect te reason it's taken so goddamn long for a 'mainstream' version has been because there's a known issue around welded ti cranks.
I suspect the crossection of the arms is plenty to compensate for material choice. They are very very chunky. In steel they would obviously be far stiffer.
The shape can bring stiffness but the stw ratio would remain lower than the same shape in aluminium. Just that Ti has lower specific stiffness in torsion and flexion. That's putting a lot of efforts to design something with a material with lower performance index for this application.
Now they look cool Image

FreaK
Posts: 840
Joined: Sat Aug 27, 2005 5:57 am
Location: mOntreal

by FreaK

The whole EE cranks saga, so to speak, has relied on aluminium designs, and has not led to a commercially available product. There are clearly a few reasons for that.
Comparing materials used in a crank by mass is essentially useless as crank design is a exercise in volume management. Mass is secondary. It's like saying a Ti frame "cannot" be stiff. That's fairly absurd.
it's actually possible to come to the conclusion even before realising it makes no sense at all
-
tymon_tm

FreaK
Posts: 840
Joined: Sat Aug 27, 2005 5:57 am
Location: mOntreal

by FreaK

I'd be all over a steel road version too!
it's actually possible to come to the conclusion even before realising it makes no sense at all
-
tymon_tm

C36
Posts: 252
Joined: Fri Mar 03, 2017 3:24 am

by C36

FreaK wrote:The whole EE cranks saga, so to speak, has relied on aluminium designs, and has not led to a commercially available product. There are clearly a few reasons for that.
Comparing materials used in a crank by mass is essentially useless as crank design is a exercise in volume management. Mass is secondary. It's like saying a Ti frame "cannot" be stiff. That's fairly absurd.
Not sure if that was for me but i never mentioned mass but stiffness to weight ratio, material stiffness (young modulus) and density. For example there is not a single chance on earth to have a competitive stw ratio on a Ti frame (but could be competitive on other aspect, confort, durability...). I would say it is the same here. Even if result end up acceptable, ohter materials would have been more performant.


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youngs_modulus
Posts: 512
Joined: Wed Sep 20, 2006 1:03 am
Location: Madison, WI USA

by youngs_modulus

C36 wrote:
Thu Apr 19, 2018 12:18 am
FreaK wrote:Comparing materials used in a crank by mass is essentially useless as crank design is a exercise in volume management. Mass is secondary. It's like saying a Ti frame "cannot" be stiff. That's fairly absurd.
Not sure if that was for me but i never mentioned mass but stiffness to weight ratio, material stiffness (young modulus) and density. For example there is not a single chance on earth to have a competitive stw ratio on a Ti frame (but could be competitive on other aspect, confort, durability...).
I'm not sure what you're trying to say here, C36. You say a Ti frame can't possibly have a competitive stiffness-to-weight ratio. But compared to what?

Besides, most metals used for bicycles have essentially the same stiffness (modulus) to weight (density) ratio. In units of gigaPascals / grams per cm^3, those ratios break down like this:

4130 steel: 26.12
Ti 6Al/4V: 25.73
7075 aluminum: 25.52
Magnesium: 25.29

You can see that each of these is within 1.5% of the values above or below, and most of them are within 1%. A material's stiffness-to-density ratio is not really something that matters so much when trying to make something light and/or stiff.

Marin
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Joined: Wed Jan 22, 2014 11:48 am
Location: Vienna Austria

by Marin

youngs_modulus wrote:
Fri Apr 20, 2018 1:22 am
metals used for bicycle
There's a reason most frames are CF nowadays :)

My main ride is still titanium though for various reasons.

C36
Posts: 252
Joined: Fri Mar 03, 2017 3:24 am

by C36

youngs_modulus wrote:
C36 wrote:
Thu Apr 19, 2018 12:18 am
FreaK wrote:Comparing materials used in a crank by mass is essentially useless as crank design is a exercise in volume management. Mass is secondary. It's like saying a Ti frame "cannot" be stiff. That's fairly absurd.
Not sure if that was for me but i never mentioned mass but stiffness to weight ratio, material stiffness (young modulus) and density. For example there is not a single chance on earth to have a competitive stw ratio on a Ti frame (but could be competitive on other aspect, confort, durability...).
I'm not sure what you're trying to say here, C36. You say a Ti frame can't possibly have a competitive stiffness-to-weight ratio. But compared to what?

Besides, most metals used for bicycles have essentially the same stiffness (modulus) to weight (density) ratio. In units of gigaPascals / grams per cm^3, those ratios break down like this:

4130 steel: 26.12
Ti 6Al/4V: 25.73
7075 aluminum: 25.52
Magnesium: 25.29

You can see that each of these is within 1.5% of the values above or below, and most of them are within 1%. A material's stiffness-to-density ratio is not really something that matters so much when trying to make something light and/or stiff.
Hell yes it matters! The ratio you listed is valid in traction (E/density). Flexion performance index is (SquareRoot E / density) then your perf index is:
- Steel 1.9
- Aluminium 3.1
- Ti: 2.4

In torsion the differences are even larger. Now in all cases you need to factor other parameters like manufacturing (wall thickness limits) or strength (not a problem for Al, Ti or steel but could be the case for magnesium for example), will stop there or could talk about it four hours Image.

For the Ti frames, "compared to what?" Well compared to other materials, aluminium for example (carbon being anisotropic you can't generalise).


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scant
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Joined: Fri Apr 30, 2004 2:05 pm
Location: S.Wales UK

by scant

ta

scant

Ravnsnaes
Posts: 88
Joined: Thu Dec 22, 2005 2:48 pm
Location: Denmark

by Ravnsnaes

They can definitely make titanium cranks to rival carbon and aluminium cranks in terms of stiffness and weight. The answer is ofcourse: 3D printing. (But the price would be in the thousands of $).

by Weenie


C36
Posts: 252
Joined: Fri Mar 03, 2017 3:24 am

by C36

Ravnsnaes wrote:They can definitely make titanium cranks to rival carbon and aluminium cranks in terms of stiffness and weight. The answer is ofcourse: 3D printing. (But the price would be in the thousands of $).
Not really sure what 3D printing would bring for a component that has a "fairly" simple shape and no real volume constraint, the performance index of Ti would remain lower in terms of stw. That's just not an application where you need titanium...


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