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PostPosted: Thu Oct 03, 2013 12:41 pm 
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Every now and then I've noticed threads popping up on either light or stiff stems, but when is a stem both stiff and light enough?

Behold this 130mm prototype stem I'm testing that makes the carbon steerer of my Alpha-Q GS30 seem rather elastic.

Image

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Last edited by mythical on Mon Nov 24, 2014 6:26 pm, edited 2 times in total.

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Posted: Thu Oct 03, 2013 12:41 pm 


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PostPosted: Thu Oct 03, 2013 2:25 pm 
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Jeez louieez !
130mm is a propper lenght aswell, tell us more, how made the stem, is it your handy work ?(;


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PostPosted: Thu Oct 03, 2013 3:15 pm 
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Wow. Is that fully CNC'd? I'd be slightly concerned about the strength of a CNC'd part at that weight.

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PostPosted: Thu Oct 03, 2013 4:12 pm 
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Ahh a beautiful stem but 130mm? Might as well use a baseball bat for a stem at that point.

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PostPosted: Thu Oct 03, 2013 4:20 pm 
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So how much does the 90mm weigh?
And cost?

:twisted:

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PostPosted: Thu Oct 03, 2013 6:10 pm 
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Here are projected weights for each length.

80 mm =67 grams
90 mm = 71 grams
100 mm = 74 grams
110 mm = 77 grams
120 mm = 80 grams
130 mm = 85 grams

The prototype bolts are hollow so they're lighter than production bolts, which will not be hollow. Prices will be announced when production is underway, once testing is rounded off successfully. This is the 3rd generation prototype already. The angle is 7.5º with a 37.5mm stack height.

The first one can be seen in this Velonews article and the second one (a 150mm) can be seen here: http://www.facebook.com/photo.php?fbid=516676328379025 This one almost passed EN14781 but it wasn't good enough for production. Meanwhile, I fell ill and required immediate medical treatment, though now I'm fully recovered and want to give the world awesome bike parts.

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PostPosted: Thu Oct 03, 2013 6:19 pm 
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I fail to see why 130 is anywhere close to being a baseball bat. Pretty standard length for a lot of us out there...

Now, how can we get some real stiffness stats on this proto? Looks quite nice.


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PostPosted: Thu Oct 03, 2013 6:22 pm 
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Nicely done. Look forward to hearing more about it!


Zen Cyclery wrote:
Ahh a beautiful stem but 130mm? Might as well use a baseball bat for a stem at that point.


What is that suppose to mean?



MajorMantra wrote:
Wow. Is that fully CNC'd? I'd be slightly concerned about the strength of a CNC'd part at that weight.


Why are you concerned about a CNC'd part? No need for concern if it is done correctly by a competent person as mythical seems to be in this regard. I would have no concern.


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PostPosted: Thu Oct 03, 2013 7:05 pm 
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Just because CNC'd parts are inherently weaker than forged ones, and this is a part that's pushing the limits on weight savings.

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PostPosted: Thu Oct 03, 2013 8:31 pm 
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Allow me to address a few common misconceptions. First of all, whether forged or CNC-machined, the point at which a part fails (and all parts will fail!) is not determined by how it's manufactured, but rather by how well it's engineered. My aim was to build a stronger and stiffer stem in absolute terms. Why? I wasn't satisfied with the selection of stems I tried, e.g. a Ritchey 4-Axis WCS and Thomson X4, all 130mm, and hoped I could do better.

With FEA (Finite Element Analysis) only being a predictive tool, we calculated how my 3D-stem models behaved when applying the stringent EN14781 and EN14766 test protocols (respectively for road and mountainbikes). The published FEA-report concluded that stresses remained well below the fatigue limit of AL7075-T6 aluminum, the material used for this stem. Currently, these claims are undergoing validation through real world testing by our development partner, a trusted handlebar manufacturer in Germany. The project sustained minor delays caused by illness and faulty manufacturing, so final results are still pending.

Should this stem pass the demanding EN-tests, a basic requirement for stems raced in UCI events, an even greater challenge arises: Convincing potential buyers that our stem is sufficiently strong, stiff and durable, and safe enough for its given application despite its low weight.

As for stiffness values, they mean little by themselves. Such numbers only speak through comparative data generated by pitting this stem against competitors. Blessings to those with patience and understanding! :thumbup:

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PostPosted: Thu Oct 03, 2013 8:38 pm 
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MajorMantra wrote:
Just because CNC'd parts are inherently weaker than forged ones, and this is a part that's pushing the limits on weight savings.


That is a misconception many hold. A properly designed and executed CNC part is just as strong. No need to paint broad strokes.


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PostPosted: Thu Oct 03, 2013 10:53 pm 
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This product has a ww niche. 37.5mm stack is nice. Please also do 17deg for those who go low.

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PostPosted: Thu Oct 03, 2013 11:19 pm 
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Does it come in black?

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PostPosted: Thu Oct 03, 2013 11:36 pm 
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Definitely looks like a nice stem. Add me to the waiting list as long as the price is competitive. Keep us updated on those cranks too, Mythical. What's next beyond the stem and cranks? Brakes (I hope)?


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Posted: Thu Oct 03, 2013 11:36 pm 


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PostPosted: Thu Oct 03, 2013 11:46 pm 
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53x12 wrote:
MajorMantra wrote:
Just because CNC'd parts are inherently weaker than forged ones, and this is a part that's pushing the limits on weight savings.


That is a misconception many hold. A properly designed and executed CNC part is just as strong. No need to paint broad strokes.


It's a misconception? Forging process refines the grain structure of the material itself. Of course, engineering can get around that for the most part, but a forged part will likely be stronger than a machined one, using the same material


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