Cervélo aero post tuning

[Ypsylon]

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.



Weight savigns would be 9g.

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



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



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?

[...]

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


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" . Then I can send you a prototype version and you will test it... ?

[Boonen]

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

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.

[Ypsylon]

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

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.

[Boonen]

I think he means the diameter of your saddle rails

[Ypsylon]

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

[...]

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

I know the other measures for the saddle rails:

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 ( 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.

[BMANX]

This thread is getting good now that it appears we can go lighter by a nice margin on the Cevelo posts.

[Ypsylon]

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.

[daryl1]

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

[Cheers!]

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.

[daryl1]

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.

[alienator]

Uhm, shouldn't 2r/diameter=1, since 2r=diameter?

[Ypsylon]

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.

[Boonen]

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