AeroPod, PowerPod and Newton

Now the better weather is here in the UK, I've switched to my summer bike. Did a tilt/offset/coast down and calibration ride. Here is my profile:

Aero: .330
Fric: 2.68
Weight: 174lb
Wind Scaling: .990
Riding tilt: 0
Cda: 0.334
Crr: .0034

I was pretty pleased to get such good wind scaling, and a zero tilt was interesting. The only thing that looks a bit low is the Fric figure, although I did about 10 coast downs and even excluded one result with a crazy low friction result. Otherwise the results aren't far away from the example profile provided with the iBike software.

The results have seemed to be pretty good over the last few rides.

I tried another test last night but just keeping get loads of bad coasts etc and the results were generally nonsense so I've ignored that. It did however confirm that the wind scaling was accurate (.97). I'm going to try another test in a week or two, just for fun.

edit:I noticed in another thread that it was mentioned that a scaling of 1.0 was almost impossible?

Any comments?

Thanks

Of course the wind scaling value is important for accurate power at higher speeds, but I do not think a value near 1 is any better or worse than a value different than 1. The important thing is, whatever its value, is that it accurately accounts for hardware sensor variations, your particular mounting on the bike and any airflow variations near the unit.

Fric is proportional to weight as well as the difference between crr and riding tilt when riding tilt is expressed as a tangent. The reason it is somewhat low is that riding tilt is 0. Had you a riding tilt in the usual range, fric would be 2 times or more larger.

Thanks mds. That explains it nicely.

OK for fun, I did another test today. It's a reasonably windy day today. I did 13 coast downs (into a headwind). Most of them were around the same reading except for 3 which had low aero and high crr (8, 10 & 15). I accepted all the values. On the out and back ride, I think it was more or less a cross-wind. Here are the results of todays profile:

Aero: .313
Fric: 4.48 (If I took out those three high values, this was closer to 3.4 IIRC)
Weight: 174lb
Wind Scaling: .846
Riding tilt: - 0.1
Cda: 0.370
Crr: .0048

If I switch between profiles in the iBike software, I gain on average about 7-10 watts if I use todays profile (over a short or longer ride). Taken with the other aborted test, I think the wind scaling should probably be closer to 1 and the windy day has skewed this test.

This test has at least verified the tilt is in the range 0 to -0.1 - which was what I really wanted to test. This only makes about a 1 watt difference on average from what I can tell.

I'll continue use the original profile in my original post.