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Cervélo aero post tuning

Discussion on bikes, and whatever...

Re: Cervélo aero post tuning

Postby Ypsylon » Sun Dec 27, 2009 1:40 pm

While the cradle thingy is on its way, I thought I'd post some pics of my "effort" so far.

I've just put the thing together loosely, it's not properly mounted.

The idea is to resemble the way KCNC and NU use yokes.

Image

Weight savigns would be 9g.

The only problem right now is the front bolt. The NU bolts are only threaded to a certain point.

Image

If the yoke can't move freely the clamping mechanism doesn't work properly.

Image

Possible solutions:

a) File the threads off of the bolts.

b) Drill out the threads inside the yoke.

c) Get a proper bolt.

So, would you guys consider this a safe mod? I'll have the time to test it and just carry the standard parts around with me, but this is my race/crit bike and the weight savings are "only" 9g.

Which way would you go and where can I buy a partly threaded ti bolt?
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cerveloNUcomp.jpg
NUpostrearbolt.jpg
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Re: Cervélo aero post tuning

Postby ... » Sun Dec 27, 2009 5:36 pm

Ypsylon, I have a question: do you think it would be OK if I make it just like this (because it's quite narrow?)
Image

Of course with carbon fibre and about 4-5mm tick - it would be very light. But I will need the exact "2r of the groove" :roll:. Then I can send you a prototype version and you will test it... :mrgreen: ?
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Re: Cervélo aero post tuning

Postby Boonen » Sun Dec 27, 2009 6:34 pm

If it's something you have to do and you're going to use the KNCN yokes I'd say something like that would be the answer, in stead of messing about with copying the current design in carbon. Basically just copy the normal design of an inline seatpost :dunno:

Yps, the difference between the NU post and the way you want to do things is that in the NU post the yoke acts as the not where you screw the bolt into. In your setup you don't need the threads for the front mount, don't mess with the bolt but drill out the yoke instead. Are you sure you have enough clearance between the bolt and your saddle? I've given one of those Toupe's a try once and they were awfully flexible.


Berk, I'd be curious to see what one of those carbon halfpipes would weigh, I have one here that weighs in at 10.7 grams. How much are the aluminium one's you made? I think aluminium is the better material for these things.
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Re: Cervélo aero post tuning

Postby Ypsylon » Sun Dec 27, 2009 6:41 pm

I have no clue if it would hold up, but I'd try it and carry the original part around just in case. :top:

The 2r/diameter is ~2.2cm.

If it helps, a 20 euro cent coin is ever so slightly bigger, a 5 euro cent coin is just a tad smaller.
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cervaeropost20cent1.jpg
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Re: Cervélo aero post tuning

Postby Boonen » Sun Dec 27, 2009 6:46 pm

I think he means the diameter of your saddle rails :wink:
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Re: Cervélo aero post tuning

Postby Ypsylon » Sun Dec 27, 2009 6:57 pm

Ah, I see. I'm at my parents house and didn't bring my calipers. Could somebody measure a Toupé for me please?
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Re: Cervélo aero post tuning

Postby ... » Sun Dec 27, 2009 10:47 pm

Ypsylon thanks, I meant the 2r/diameter and now I know it (cca. 2.2mm) :wink:

I know the other measures for the saddle rails:
Image


Berk, I'd be curious to see what one of those carbon halfpipes would weigh, I have one here that weighs in at 10.7 grams. How much are the aluminium one's you made? I think aluminium is the better material for these things.


The aluminium halfpipes are quite heavy (but undestroyable), 24g for 30mm diameter.
For 22mm diameter it would be around 18g ( :roll: approximation)


IN THEORY:
If I would make a carbon one, with my specific technic, the weight would be (statistic calculated) around 7.8g for 30mm diameter, with 5mm thickness. That means around 6.3g for 22mm diameter with 5mm tickness.
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Re: Cervélo aero post tuning

Postby BMANX » Mon Dec 28, 2009 12:16 am

This thread is getting good now that it appears we can go lighter by a nice margin on the Cevelo posts.
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Re: Cervélo aero post tuning

Postby Ypsylon » Mon Dec 28, 2009 11:33 am

Also, I was just explained that you save an extra Watt during out of the saddle riding for every 100g of less saddle weight. So saving 20g is .2 Watts. Doesn't sound too great? Wait till you spring uphill.
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Re: Cervélo aero post tuning

Postby daryl1 » Mon Dec 28, 2009 6:36 pm

This sounds interesting, I am getting my frame refinished and it would be great to drop a little weight with the rebuild. I don't have a derailleur hangar handy so I don't know how much savings there would be, but there are carbon hangars for sale here:

http://www.carbonschmiede.de/schaltauge.htm
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Re: Cervélo aero post tuning

Postby Cheers! » Mon Dec 28, 2009 7:17 pm

my concern with that hanger is that it won't act as a fuse when you get into a situation where you need the hanger to bend or break. I would rather have an aluminum hanger at a cost of X weight increase bend and break rather than a carbon hanger that won't break and damages my frame instead.
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Re: Cervélo aero post tuning

Postby daryl1 » Mon Dec 28, 2009 8:55 pm

Yes that is why I did not purchase the part. However tempting it may sound, I would rather have my derailleur shifting be really misaligned than have the derailleur snap off and possibly hit my wheel spokes or frame.
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Re: Cervélo aero post tuning

Postby alienator » Tue Dec 29, 2009 2:52 am

Uhm, shouldn't 2r/diameter=1, since 2r=diameter? :grin:
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Re: Cervélo aero post tuning

Postby Ypsylon » Tue Dec 29, 2009 9:52 am

That is indeed true if you interpret the sign "/" in a mathematical sense. Here it was used to give one more reference to what measurement I refered to. I suppose diameter(2r) would have worked as well but would have ended up being (2r)squared, and since we are two europeans comunicating here I knew that he'd know that I knew he'd know that I'd used diameter:2r had I wanted him to divide anything. :wink:
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Re: Cervélo aero post tuning

Postby Boonen » Tue Dec 29, 2009 11:21 am

... wrote:The aluminium halfpipes are quite heavy (but undestroyable), 24g for 30mm diameter.
For 22mm diameter it would be around 18g ( :roll: approximation)


IN THEORY:
If I would make a carbon one, with my specific technic, the weight would be (statistic calculated) around 7.8g for 30mm diameter, with 5mm thickness. That means around 6.3g for 22mm diameter with 5mm tickness.


Will be interesting to see where this goes, the one's I have are 3,5mm but to weak. Don't think it has to do with either weight or thickness but with build quality though. I'd go for the 18g aluminium one, not sure if you'd save much weight then though which was what got all this started in the first place :wink:
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