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Re: Setting drag factor

Posted: June 19th, 2018, 4:11 pm
by VivaTerlingua
So could somebody do a recalibration with the drag on high then cover the opening and break all the bikeerg records?

Re: Setting drag factor

Posted: June 20th, 2018, 4:10 am
by CaseyClarke
VivaTerlingua wrote:So could somebody do a recalibration with the drag on high then cover the opening and break all the bikeerg records?
Pretty sure I’ve already seen a case where this happened in the Facebook BikeErg group, although they never admitted to it. Either that or they calibrated first, set it to high drag, then wrap a towel around the flywheel. I think in this case it still detects the same high drag, but the pedalling resistance becomes much lighter.

Re: Setting drag factor

Posted: December 28th, 2018, 10:49 pm
by johnlvs2run
c2jonw wrote:
June 15th, 2018, 8:33 am
The BikeErg doesn't have a significant rundown period and must be manually calibrated. Once calibrated there are three inputs that the PM uses to calculate the current drag factor- damper position via an angle sensor, temperature and barometric pressure. As these inputs change the PM revises the drag factor. This method will not detect a change in drag factor from restricting the airflow by any means other than moving the damper. So while you can achieve very light loading by blocking the airflow, your scores will not be accurate. C2JonW
From a check of various logs, the pace is directly proportional to the RPM for each specific drag setting.
Thus regardless of the drag setting, the fan speed is directly proportional to the RPM, although the average is not shown in tenths.

If that is correct, I did find instances in logs were the RPM for a drag setting resulted in an out of proportion much faster pace,
which based on previous posts, could indicate that the intake was blocked, perhaps unintentionally, as this seems to be easy to do.

I wonder why C2 didn't implement a more accurate way to measure the air flow resistance, and to compare it with the fan speed or cadence.

Re: Setting drag factor

Posted: December 30th, 2018, 4:12 pm
by CaseyClarke
All too easy to trick the outputs on these unfortunately. If you drape a towel over the flywheel it significantly reduces the pedaling resistance (to almost nothing) but the drag factor stays the same. Max drag with a towel covering the flywheel makes it super easy to get below 1:00 pace (2000w+) and could be sustained all day. Once you've 'pedaled to calibrate' right before a ranking distance, doing this doesn't affect the verification code. Ranking scores can easily be cheated. As much as I'd like to see BikeErg records, I hope they are only a thing for venue competitions.

Re: Setting drag factor

Posted: February 3rd, 2019, 6:58 am
by GJS
A bit of a shame, this.

I really like the feel and riding position of the Bikerg. Better, for me, than the Wattbike and I'm tempted to get one.

But the upshot of all this is that you need to keep the thing very clean if you care for accurate measurement. (We are all aware of the impact dirt has on gym rower drag factors.)

An additional irritant is that you have no ready means of checking whether your cleaning efforts have been successful. Unless I'm mistaken :?:

Re: Setting drag factor

Posted: February 3rd, 2019, 2:02 pm
by Allan Olesen
GJS wrote:
February 3rd, 2019, 6:58 am
But the upshot of all this is that you need to keep the thing very clean if you care for accurate measurement.
No. The measurement is accurate under all circumstances. The cleanliness will only affect which damper position you will need to get the desired resistance.

Re: Setting drag factor

Posted: February 3rd, 2019, 3:52 pm
by GJS
Thanks, Allen.

Given what Jon says on pg2 I'm not entirely sure how you arrive at that emphatic 'no' ?

It seems to me that a dirty machine could very well provide a watt reading which is higher than the actual work done - an issue that does not arise on the self-calibrating SKierg and rower.

Re: Setting drag factor

Posted: February 3rd, 2019, 4:01 pm
by Allan Olesen
I assume that one still keeps the machine regularly calibrated, even if one doesn't regularly clean it.

Also, I thought I read somewhere that the BikeErg does one auto calibration per session (where the Row Erg does one auto calibration per stroke). But I may have understood that wrongly.

Re: Setting drag factor

Posted: February 9th, 2019, 9:31 am
by GJS
Cheers. I'm just not sure how one could go about recalibrating the thing.

Would be great if it did auto calibrate at the start of every session. Unless a damp crossfitter falls in a heap and blocks the fan during the piece you could certainly rely upon the watts shown.

On a selection of new bikergs I'm getting c180 watts at c 90rpm on the lowest setting. Over 20mins that's definitely top end UT1 for me in my current state. Would take a number of months before I could sit comfortably in UT2 at 90rpm for 45mins+.

Re: Setting drag factor

Posted: February 9th, 2019, 3:24 pm
by jamesg
Just stop pedaling; the flywheel slows and in the absence of power input systems can measure speed and deceleration and calculate drag. Maybe the Manual shows the minimum idle time.

Re: Setting drag factor

Posted: February 9th, 2019, 6:27 pm
by GJS
Thanks, James.

I took all this to mean that - beyond an intial manual calibration at C2 - the bike entirely lacked the capacity to accurately account for dust aggregation over time. A pessimistic and likely mistaken interpretation.

I prefer your take that recalibration effectively occurs every time the thing stops, such that you can start every session confident that PM watt readings are true; a state of affairs much more in keeping with C2's promotional literature, traditions etc