Slope of 6% on Drivo feels more like 8% or more

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Slope of 6% on Drivo feels more like 8% or more

Postby webmaster » Fri Nov 17, 2017 12:41 pm

I have set up a specific program on the Drivo using the desktop REAL application to simulate a climb of 6% over 15 km. When it enters the slope portion of the program, the effort required to do this feels more like 8 to 10%. How do I come to that conclusion, well the speed at which I am riding and the gear ratio. I am using a 36-25 and my speed is around 13.5 kph. However, in real riding when doing a 5 or 6% slope, I am doing between 18 to 20 kph. The watts vary on the road and I don't think the watts of my chain ring power meter are close to those of the Drivo so I cannot compare apples to oranges here.

I have done calibration of the Drivo but that does not make much of a difference. I have my weight set to 68kg. I have used to have a wired REAL Power and the speeds of the Drivo remind me of the 8 to 10% settings I used on that machine.

Can anyone shed some light on this? I would prefer to be setting up programs that are close to slopes I would like to train against rather than having to guess what I am doing.

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Re: Slope of 6% on Drivo feels more like 8% or more

Postby Elite Admin S » Thu Nov 23, 2017 12:43 pm

Hi

Please can you tell me the serial number of your Drivo and the offset you get at the end of the calibration?

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Re: Slope of 6% on Drivo feels more like 8% or more

Postby webmaster » Sun Dec 17, 2017 10:13 pm

Sorry for the delay in responding back with the information. I was trying out some ideas first to make sure I was comparing experiences correctly.

First off, part of the problem was that the wheel diameter was not correctly configured for my real world experiences. I needed to change the default of 2070 to 2096. That made a small change in the speeds but not enough to come close to what I experience on the road on 6% climbs. On my old Real Power trainer, my speeds were much higher and I would general do 8% climbs in a 23 rear cassette. Here I am doing "6%" in a 25 rear cassette.

The calibration value from the trainer through the Real desktop app is 6438 and the serial number is 42167.

I am going to do another test to see if my C1 chainring power meter is close to the values of the Drivo on my next ride.

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Re: Slope of 6% on Drivo feels more like 8% or more

Postby Elite Admin S » Mon Jan 01, 2018 6:13 pm

Lete me know if now simulation is realistic

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Re: Slope of 6% on Drivo feels more like 8% or more

Postby webmaster » Thu Jan 04, 2018 1:15 pm

The power values between the Drivo and C1 chainring are close which is good. However, that doesn't answer why the simulation of the 6% slope is so off in terms of reality.

I don't know how the REAL software does its calculations, but I do know that their is definite errors in them. As I mentioned in a previous post, the distances between the Garmin device and the REAL software are out. In this case now, between 20 and 50 metres over a ride. And this is due to a rounding error per se. Dividing 2096 by 3.43 yields 611.08. So over a 20 or 30 km ride, 0.08 mm is not going to add up to 50 metres. For example, if I am riding at 85 rpm and we have a 1:1 relationship between pedal revolution and wheel revolution (which it isn't), over a 60 minute ride you have 5100 pedal strokes. Mulitply that by the fraction of 0.08 you have 408 mm.

I wouldn't expect exact distances between the two devices, however, like the power devices, they should be close.

Further info Jan 16: I did a ride this morning and the distance discrepancy over the 30 km ride was 140m! That is a huge difference. The only thing I can think of that would cause that given the trainer is sending out the same signal to the 1030 and the laptop, is that the laptop is dropping packets (and it seems a lot of them today). That means that their is a problem with the ANT+ device driver or the REAL software not being fast enough or smart enough to grab all the packets and place them in a queue to be properly processed.


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