Still struggling with combo mount settings

Still struggling with combo mount settings

Postby djaustin » Wed Apr 19, 2017 6:15 pm

Running my two powerpods, the Time Trial unit is providing consistent reproducible data with an FTP of about 290 Watts (for my 67 kg). I've tested this by calibration, a 25 and a 10 TT (attached file with race from about 27 minutes).

I'm running a second powerpod, that when mounted on the bars this gives reasonably consistent values. However my road race bike can't take this mount, so I use an out front combination mount due to the profile of the handlebars bars not being round. What I note is consistently higher (+30 Watts or so) values, and I don't know what needs tweaking. I think it is wind scaling that is over-optimistic for the mount. I attach a race file on the same circuit that had a lot of drafting (of course), but I don't believe my NP was higher in the two races compared with the TT.

The TT bike has lower Crr (not much), weighs about a kilo more and has more aero wheels. The road races had drafting, but I was still going hard and the second was basically an FTP test! I'd like the two to match at about 300 watts really.

Can you advise as to what tweaking is needed please for the combination out front mount? I did calibrate with the outfront settings, but still don't get agreement.
Attachments
iBike_04_18_2017_1729_84_km.ibr
Road races on same circuit
(412.83 KiB) Downloaded 2 times
iBike_04_19_2017_1842_31_km.ibr
TT race
(164.66 KiB) Downloaded 2 times
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Re: Still struggling with combo mount settings

Postby djaustin » Thu Apr 20, 2017 5:18 pm

Just as an update, I ran some time for power calculations to predict my TT time based on reported average power of 289 Watts using bikecalculator. The predicted time was within 1% of my real time, so I am certain the TT calibration is spot on. Of course one can argue that the model uses the same algorithm as the powerpod so it ought to agree. So then I predicted the time of the winner based on their DFPM recorded 395 Watts, and this too was within 1% of their time giving model validation. Those TT numbers are for a closed circuit, 11 laps with setting for tubular tyres, 9C, 33 metres elevation and aerobars.

I'm impressed and now have a target average of 320 Watts.

If only I could get the consistency on my road race bike to help with the training.
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Re: Still struggling with combo mount settings

Postby Velocomp » Thu Apr 20, 2017 5:33 pm

It looks like your road bike ride involved a lot of drafting. That's OK, but it is impossible for me to determine if anything is wrong.

Please post a solo training file and I will see if I can help.
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Re: Still struggling with combo mount settings

Postby djaustin » Fri Apr 21, 2017 2:56 am

Commute to work on the same day attached. No drafting this time. NP is listed as 227 Watts, but this was a very gentle ride. I'll do the same 11 lap TT on my race bike to get something for comparison, as I like the closed circuit as a means of field testing - it's always windy though.

Thank you John.

PS I get a lot of interest at the TTs I enter here in the UK
Attachments
iBike_04_18_2017_0945_22_km.ibr
Commute
(139.04 KiB) Downloaded 2 times
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Re: Still struggling with combo mount settings

Postby djaustin » Fri Apr 21, 2017 8:40 am

And for further reference, here is today's 40 km commute with the PP mounted on the handlebars of my "roadified" cross bike (8 kg, with tubeless 28c high quality clinchers). The power readings here are entirely credible, consistent with my TT bike and RPE, and involved no drafting. I want the "outfront" profile to match this one really. At the moment they do not, and I am sure it is just wind scaling. I ride predominantly on the drops.

This profile was calibrated on my fixed wheel road bike (about the same weight, tyres, position), and I just moved the pod and speed sensor across (I have three bar mounts).
Attachments
iBike_04_21_2017_0842_40_km.ibr
Bar mounted commuting ride
(245.07 KiB) Downloaded 2 times
djaustin
 
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Re: Still struggling with combo mount settings

Postby Velocomp » Fri Apr 21, 2017 5:36 pm

For your road bike, please do an "out and back" calibration. Use Isaac Device/Device Setup, and select "Best Accuracy" on the final step.

You'll find O&B instructions elsewhere on the forum.

After doing an O&B ride please post your subsequent ride file.
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