Using CdA / Testing Protocol Advice?

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b9rel8tor
Posts: 4
Joined: Sun Apr 05, 2015 10:37 am

Using CdA / Testing Protocol Advice?

Post by b9rel8tor » Mon May 14, 2018 11:29 am

I will be using the CdA function in my ibike in the coming weeks to see if I can eek out any speed gains in time for Nationals, June, 14.

Some questions that I hope the group can help me with:

- - Is the CdA function precise enough that I will be able to tell the difference between, let's say, helmet positions?

- - My iBike is mounted between my aero bars (see photos below and attached). I seems as though nothing will interfere with it (one photo shows my hand on the bar, just in case). Is that right?

- - I have an Xlab "torpedo" water bottle that mounts above and behind the iBike - again, it seems like it shouldn't interfere, but I wanted to check (it mounts on the carbon platform that is velcro'd to the TT bars in the overhead shot. I can see the iBike when the bottle is in place, so the whole body of the iBike is in front of the bottle).

- - The ONLY place where a mount fits is on my aero bars. This isn't a problem except if I want to try a different angle for the bars. The iBike tilt will be incorrect, and probably the wind sensor will be affected also? What protocol should I use if I want to try a different TT bar angle? Do I need to do a cal ride in-between CdA tests? What's the best way?

Thanks all for your help!

Peter in StL
Attachments
iBikeTTOverheadCrop.jpg
iBikeTTOverheadCrop.jpg (65.9 KiB) Viewed 299 times
iBikeTTSideView.jpg
iBikeTTSideView.jpg (89.87 KiB) Viewed 299 times
iBikeTTSideViewWHand.jpg
iBikeTTSideViewWHand.jpg (87.9 KiB) Viewed 299 times

Velocomp
Velocomp CEO
Posts: 5190
Joined: Fri Jan 11, 2008 9:43 am

Re: Using CdA / Testing Protocol Advice?

Post by Velocomp » Mon May 14, 2018 11:49 am

Attaching Newton to your TT bars won't work. The bars are too flexible for the required accuracy of CdA measurement.

Find a way to attach Newton to your top tube, then run a hose from Newton to the front of your bike. This will work great.
John Hamann

b9rel8tor
Posts: 4
Joined: Sun Apr 05, 2015 10:37 am

Re: Using CdA / Testing Protocol Advice?

Post by b9rel8tor » Mon May 14, 2018 1:00 pm

Hmmm . . . has anyone done this (attach an iBike to the top tube)?

I have a Cervelo P3, which has two water bottle-style screws in the top tube for mounting a bento box (which I have done - a fabric pouch for spare tube etc . . . I take it off when I race). Maybe I can use one of the screws?

This means that I won't be able to view the iBike while riding in aero position . . . but I guess I can check the results afterwards?

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