Setting drag factor

Discuss all things related to the BikeErg, Concept2's newest product.
VivaTerlingua
Paddler
Posts: 14
Joined: September 27th, 2017, 6:48 pm

Re: Setting drag factor

Post by VivaTerlingua » June 19th, 2018, 4:11 pm

So could somebody do a recalibration with the drag on high then cover the opening and break all the bikeerg records?

CaseyClarke
1k Poster
Posts: 101
Joined: July 1st, 2016, 8:59 am

Re: Setting drag factor

Post by CaseyClarke » June 20th, 2018, 4:10 am

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.

User avatar
johnlvs2run
Half Marathon Poster
Posts: 3676
Joined: March 16th, 2006, 1:13 pm
Location: California Central Coast
Contact:

Re: Setting drag factor

Post by johnlvs2run » December 28th, 2018, 10:49 pm

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.
73 5'8 155
age 70+ world record pace per weight percentages
skierg: 100m 87.4 / 500m 86.2 / 1k 85.9 / 2k 89.4 / 5k 87.6 / 10k 89.4 / 60' 92.0 / 21k 93.6
my training log

CaseyClarke
1k Poster
Posts: 101
Joined: July 1st, 2016, 8:59 am

Re: Setting drag factor

Post by CaseyClarke » December 30th, 2018, 4:12 pm

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.

GJS
2k Poster
Posts: 317
Joined: March 28th, 2016, 1:21 pm

Re: Setting drag factor

Post by GJS » February 3rd, 2019, 6:58 am

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 :?:
Gary
43, 5'11'', 190lbs

Allan Olesen
2k Poster
Posts: 374
Joined: April 27th, 2018, 6:40 am

Re: Setting drag factor

Post by Allan Olesen » February 3rd, 2019, 2:02 pm

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.

GJS
2k Poster
Posts: 317
Joined: March 28th, 2016, 1:21 pm

Re: Setting drag factor

Post by GJS » February 3rd, 2019, 3:52 pm

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.
Gary
43, 5'11'', 190lbs

Allan Olesen
2k Poster
Posts: 374
Joined: April 27th, 2018, 6:40 am

Re: Setting drag factor

Post by Allan Olesen » February 3rd, 2019, 4:01 pm

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.

GJS
2k Poster
Posts: 317
Joined: March 28th, 2016, 1:21 pm

Re: Setting drag factor

Post by GJS » February 9th, 2019, 9:31 am

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+.
Gary
43, 5'11'', 190lbs

jamesg
Half Marathon Poster
Posts: 2493
Joined: March 18th, 2006, 3:44 am
Location: Trentino Italy

Re: Setting drag factor

Post by jamesg » February 9th, 2019, 3:24 pm

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.
78y, 188cm, 87kg, last seen MHR 163. 2k (24 May 19) 8.46.6@22

GJS
2k Poster
Posts: 317
Joined: March 28th, 2016, 1:21 pm

Re: Setting drag factor

Post by GJS » February 9th, 2019, 6:27 pm

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
Gary
43, 5'11'', 190lbs

User avatar
johnlvs2run
Half Marathon Poster
Posts: 3676
Joined: March 16th, 2006, 1:13 pm
Location: California Central Coast
Contact:

Calibration and rankings

Post by johnlvs2run » July 28th, 2019, 9:22 pm

CaseyClarke wrote:
December 30th, 2018, 4:12 pm
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.
There are videos on Youtube recommending to drape a towel over the cage to keep out perspiration.
Also, videos like this one recommend actively changing the damper setting to make the pedaling much easier.
I wonder if C2 is working on ways to make calibration more stable, so tampering won't interfere with times and rankings.
73 5'8 155
age 70+ world record pace per weight percentages
skierg: 100m 87.4 / 500m 86.2 / 1k 85.9 / 2k 89.4 / 5k 87.6 / 10k 89.4 / 60' 92.0 / 21k 93.6
my training log

User avatar
NavigationHazard
10k Poster
Posts: 1729
Joined: March 16th, 2006, 1:11 pm
Location: Wroclaw, Poland

Re: Setting drag factor

Post by NavigationHazard » July 29th, 2019, 3:54 am

Actively changing the damper setting isn't tampering.
5. There is no required damper setting. You are free to choose the setting you prefer and you may change the setting during the piece as long as it is done by the person using the machine.
C2 rules and regulations for ranking pieces, https://log.concept2.com/rankings

I don't see how you could do this by yourself on a rower without pausing at the catch, but it's easy enough on a BikeErg.

As for gaming the system, as it were, the only foolproof way to ensure a mechanically level playing field is to accept only records produced at a sanctioned competition. Give everyone the same correctly set-up equipment. And that still won't solve problems like doping, or falsifying age-group status.
64 MH 6' 6"

CaseyClarke
1k Poster
Posts: 101
Joined: July 1st, 2016, 8:59 am

Re: Calibration and rankings

Post by CaseyClarke » July 29th, 2019, 12:55 pm

johnlvs2run wrote:
July 28th, 2019, 9:22 pm
CaseyClarke wrote:
December 30th, 2018, 4:12 pm
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.
There are videos on Youtube recommending to drape a towel over the cage to keep out perspiration.
Also, videos like this one recommend actively changing the damper setting to make the pedaling much easier.
I wonder if C2 is working on ways to make calibration more stable, so tampering won't interfere with times and rankings.

Ahh, bummer. Not good.

If you first calibrate, then drape a towel over the flywheel on any given damper setting the pedalling suddenly becomes super easy, but the PM5 still thinks it’s at that same drag. This is obviously most pronounced on max drag. Has led to a few dodgy scores showing up in the rankings which I’ve had to complain about. Some completely inadvertently as well.

If the flywheel isn’t covered by a towel then dropping the damper will of course make pedalling easy but your power output will drop off if you don’t increase RPMs to compensate.

I like Nav’s suggestion of only having records come from official race meetings.

User avatar
johnlvs2run
Half Marathon Poster
Posts: 3676
Joined: March 16th, 2006, 1:13 pm
Location: California Central Coast
Contact:

Bikeerg calibration and rankings

Post by johnlvs2run » July 29th, 2019, 1:42 pm

Regarding calibration on the Bikeerg:
johnlvs2run wrote:
July 28th, 2019, 9:22 pm
Also, videos like this one recommend actively changing the damper setting to make the pedaling much easier.
CaseyClarke wrote:
July 29th, 2019, 12:55 pm
dropping the damper will of course make pedalling easy but your power output will drop off if you don’t increase RPMs to compensate.
Isn't power determined by calibration on the Bikeerg? Thus calibrating on 10 then moving the damper to 1 would not result in a power / watts / pace drop at the same RPMs on the monitor. Plus, increasing the RPMs would be easier, and result in much higher power readings and faster times on the monitor than the actual power output of the cyclist. Otherwise, why bother to calibrate? The reason is, because moving the damper - on the Bikeerg - would completely mess up the readings.
73 5'8 155
age 70+ world record pace per weight percentages
skierg: 100m 87.4 / 500m 86.2 / 1k 85.9 / 2k 89.4 / 5k 87.6 / 10k 89.4 / 60' 92.0 / 21k 93.6
my training log

Post Reply