Setting drag factor

Discuss all things related to the BikeErg, Concept2's newest product.
Robbie100
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Re: Setting drag factor

Post by Robbie100 » September 28th, 2017, 6:59 am

VivaTerlingua wrote:I'm very interested in this bike however I'm a little concerned about what I am seeing regarding the level of difficulty at the lowest drag setting. It is important to be able to spin at about 80 RPM and it sounds like it could be a problem to do for long periods. This bike would be used by both me and my girlfriend and we would want to be able to use it for long spinning sessions as well as interval training. Has anybody at Concept2 commented on this?
This issue is highly subjective. Some users report the drag factor to be unsatisfactory at the lowest level. Others don't find this an issue at all. If you are used to a spinning bike utilizing friction or magnetic resistance, I suspect it will take time to adjust (if at all possible).

One possible solution, if trialling from a gym, showroom or from a mate is not possible is to order the bike and test ride it. If not happy, return it within 30 days and get a refund. You lose shipping and handling charges in exchange for that nagging thought about what could have been.

CaseyClarke
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Re: Setting drag factor

Post by CaseyClarke » September 28th, 2017, 8:23 am

VivaTerlingua wrote:I'm very interested in this bike however I'm a little concerned about what I am seeing regarding the level of difficulty at the lowest drag setting. It is important to be able to spin at about 80 RPM and it sounds like it could be a problem to do for long periods. This bike would be used by both me and my girlfriend and we would want to be able to use it for long spinning sessions as well as interval training. Has anybody at Concept2 commented on this?
I've already mentioned this a few replies back but Concept 2 haven't said anything yet. 80 rpm is actually quite low for me and I prefer to do my long easy spins, as well as most of my sessions, in the 95 - 100 rpm bracket. Easy spinning at a high ish cadence won't be an option for most people on this bike unfortunately. 98 rpm in the bottom setting, around 60 drag, apparently puts out 270+ watts, which won't be sustainable for longer periods for anyone other than pretty strong riders.
For weaker riders, with say 200w FTPs, then the only easy session you're going to get is down around 50 rpm.

Additionally, it's worth noting that a lot of the people currently using this bike are the Crossfit crowd (which I think it's geared more toward) so they'll be used to things like the AirDyne and Assault where lower cadences are quite the norm. I think a lot of pure cyclists and people doing spin classes will think it's geared way too stiffly at the bottom end.

VivaTerlingua
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Re: Setting drag factor

Post by VivaTerlingua » September 28th, 2017, 11:09 am

CaseyClarke wrote: I've already mentioned this a few replies back but Concept 2 haven't said anything yet. 80 rpm is actually quite low for me and I prefer to do my long easy spins, as well as most of my sessions, in the 95 - 100 rpm bracket. Easy spinning at a high ish cadence won't be an option for most people on this bike unfortunately. 98 rpm in the bottom setting, around 60 drag, apparently puts out 270+ watts, which won't be sustainable for longer periods for anyone other than pretty strong riders.
For weaker riders, with say 200w FTPs, then the only easy session you're going to get is down around 50 rpm.

Additionally, it's worth noting that a lot of the people currently using this bike are the Crossfit crowd (which I think it's geared more toward) so they'll be used to things like the AirDyne and Assault where lower cadences are quite the norm. I think a lot of pure cyclists and people doing spin classes will think it's geared way too stiffly at the bottom end.
I currently have a rower and a skierg and think they're great machines and am interested in the bikeerg to replace our recumbent. I like the quality of the Concept2 machines and it would be great use the same controller on all of our machines. But there are 2 things causing me to hesitate. One is this drag issue. Very often for the exercise bike, I like to put in a movie and just spin for an hour or two. It sounds like it could be a challenge because of the lowest power setting not being low enough. Several people have mentioned trying some sort of obstruction to restrict air flow. Has anybody actually tried this and how has it worked out? But even that is less than ideal, when doing intervals I would prefer to spin at high RPM and low resistance for recovery vs. just reducing my cadence. Trying to cover the air intake while riding doesn't seem very practical.

My other question is a pretty minor concern. How much of an inconvenience is it changing the drag factor while riding? It seems like it would be a lot more convenient having some sort of way to change the setting on the handle bars.

CaseyClarke
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Re: Setting drag factor

Post by CaseyClarke » September 28th, 2017, 11:32 am

I have a SkiErg and when I wrap a towel around it I can get it from its lowest drag of around 60, down to about 40. Assuming you can do the same on the BikeErg, but won't actuallly know until someone tests it. They aren't available here in Europe until next year, otherwise I would've already tried.

The handlebars do look a long way away from the seat, even when they're fully extended towards you, so I don't know how comfortable distance riding will be if you can't rest down on your elbows fully.

The damper lever is reachable from the seat, just like on a Wattbike, although you'll probably need to stretch a bit more. You'll obviously be able to move it between 1 & 10, but won't get exact drag numbers in the middle of a session. Not that you'll need exact numbers anyway. Typically, if I'm doing intervals on a WB with the lever on 10, I'd just reach down and knock it to 1 and spin along easily in the recovery.

VivaTerlingua
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Re: Setting drag factor

Post by VivaTerlingua » September 28th, 2017, 12:05 pm

The bike looks very interesting, but it's not like I need one in the next week. I think I'm going to wait until a few more user reviews get out there. It's not been available very long yet, I'm sure more comments will start turning up.

Dreadnought
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Re: Setting drag factor

Post by Dreadnought » June 3rd, 2018, 1:36 pm

CaseyClarke wrote:
The drag is simply the resistance level, which is the same as the gears on a bike.

You'd use a high ish gear if you wanted to simulate the feeling of climbing up a steep incline at low rpm, and you'd use a much lower gear for spinning along.

Not exactly. There is another factor besides rpm and resistance. It is inertia which can be created using a a large flywheel or a motor. I am currently using the TACX Neosmart Trainer, which can be set on low inertia state (uphIll grade) or high inertia state (downhill grade).

Doing 200W at 80 rpm at a 5% uphIll grade is totally different than doing 200W at 80 rpm at a 5% downhill grade.
When going uphIll you have to apply pressure to the pedals throughout the stroke in order to maintain the power output.
When going downhill, it is not necessary since the flywheel or motor will carry you through the sticking points.

jamesg
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Re: Setting drag factor

Post by jamesg » June 7th, 2018, 6:06 am

There's probably a way of getting that drag down even further by placing a tea towel or something similar over some of the holes in the grate.
To shift the drag range down (on the rowing erg) I use a filter over the air intake; now working at drag 80 - 85 and damper wide open. Can still go over 200W if I want to, however unlikely.

Presumably the same can be done on the ergbike for those who want to pull < 200W at max cadence.

The Drag range will drop anyway, as the fan fills with dust; a filter provides the same effect from day 1 and also keeps the fan clean.
77y, 188cm, 85kg, MHR 160. Last 2k (May 1018) 8.37@23

VivaTerlingua
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Re: Setting drag factor

Post by VivaTerlingua » June 14th, 2018, 1:22 pm

Does restricting the airflow affect the accuracy of the performance monitor?

dr3do
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Re: Setting drag factor

Post by dr3do » June 14th, 2018, 1:23 pm

VivaTerlingua wrote:Does restricting the airflow affect the accuracy of the performance monitor?
No, it‘s self-calibrating.
Boris (Bike/SkiErg/RowErg)

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c2jonw
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Re: Setting drag factor

Post by c2jonw » June 15th, 2018, 8:33 am


VivaTerlingua wrote:
Does restricting the airflow affect the accuracy of the performance monitor?
No, it‘s self-calibrating.
The Indoor Rower and SkiErg are self-calibrating, utilizing the recovery time between strokes to view the rate of decay of the flywheel speed to do it's calculations and recalibrating on every stroke. So any changes in airflow or other local conditions are "seen" in the rate of decay and compensated for instantly. This method was developed by C2 in 1983 and has been used succesfully in all of our PMs.

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
67 year old living in Waterbury Center, Vermont, USA
Concept2 employee since 1980! and what a long, strange trip it's been......and retiring from C2 in October 2018!

dr3do
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Re: Setting drag factor

Post by dr3do » June 15th, 2018, 8:39 am

Thanks for the explanation. #good2know
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VivaTerlingua
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Re: Setting drag factor

Post by VivaTerlingua » June 15th, 2018, 9:18 am

c2jonw wrote:

VivaTerlingua wrote:
Does restricting the airflow affect the accuracy of the performance monitor?
No, it‘s self-calibrating.
The Indoor Rower and SkiErg are self-calibrating, utilizing the recovery time between strokes to view the rate of decay of the flywheel speed to do it's calculations and recalibrating on every stroke. So any changes in airflow or other local conditions are "seen" in the rate of decay and compensated for instantly. This method was developed by C2 in 1983 and has been used succesfully in all of our PMs.

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
Thank you for an informative and very helpful reply. This makes everything very clear now.

jamesg
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Re: Setting drag factor

Post by jamesg » June 15th, 2018, 10:00 am

Presumably manual recalibration will take account of dust or any other air blockage and can restore accuracy.
77y, 188cm, 85kg, MHR 160. Last 2k (May 1018) 8.37@23

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c2jonw
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Re: Setting drag factor

Post by c2jonw » June 15th, 2018, 3:11 pm

Presumably manual recalibration will take account of dust or any other air blockage and can restore accuracy.
No not any other air blockage. Some dust buildup shouldn't be an issue, but an excessive block such as a towel over the flywheel will likely put things out of normal operating range. C2JonW
67 year old living in Waterbury Center, Vermont, USA
Concept2 employee since 1980! and what a long, strange trip it's been......and retiring from C2 in October 2018!

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Re: Setting drag factor

Post by jamesg » June 16th, 2018, 2:04 am

How do you define "normal operating range"? Is 200W at 90 rpm "normal"? "Likely": does this mean you haven't yet tried low drag?
77y, 188cm, 85kg, MHR 160. Last 2k (May 1018) 8.37@23

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