Concept2 Forum

Say I row one minute at the rate of 20 SPM in DF 100 and DF 200. Which one results in more distance? I assume DF 200. Correct?

The correct answer is that either set of conditions may produce the greater distance depending on additional factors which you do not consider: drive speed (handle force) and drive length.

I am trying to understand the DF concept first. If the only difference is the DF, will higher DF produces longer distance (in the PM) when rowing the same amount of time?

bcjm wrote:I am trying to understand the DF concept first. If the only difference is the DF, will higher DF produces longer distance (in the PM) when rowing the same amount of time?

The DF is not a major factor here. Each erger will have a different sweet spot in the DF range (about 80 to 220 on a clean machine at sea level). But even for an individual it might vary depending on the type of row that is being done. Some ergers increase the DF for very short, intense pieces. C2 recommends a range of 115 to 140.

indoorsportservices.co.uk/assets/docs/schools/schools_factsheet_all.pdf

There are a slew of messages in the archives of this forum about damper settings and drag factors, but very little agreement about anything except that it is up to the individual and that everyone has to experiment on his/her own. There is no clear cut answer, but I would think that, for anyone new at a the game, the C2 advice would come closest to answering your questions.

Bob S.

Perhaps this will help....http://www.concept2.com/skierg/training ... etting-101

C2JonW

Ooops, sorry about the Skierg reference. Same info applies for rowing.....
http://www.concept2.com/indoor-rowers/t ... etting-101

Drag factor references a vaned flywheel which is slowed or decelerated at rates determined by regulating the entry of air to an enclosing chamber (controlled frictional braking). Drag factor controls the rate of deceleration of that wheel and influences the speed and timing of the erger's inputs (muscular exertion) for best effect, but the erger produces all the work. The deceleration of the wheel produces only a repeated inertial condition which accomodates the speed of movement, leverage and opposing mass of the erger.

I thought I can get a clear yes/no answer.

Is this a correct: The performance calculation is solely based on the energy(watts) the rower puts in. Energy is determined by the rpm of the flywheel(when pull)and the weight of the flywheel(changed by the DF). PM maps the energy input to the speed of a boat. This is the only explaination makes sense to me.

Drag factor references a vaned flywheel which is slowed or decelerated at rates determined by regulating the entry of air to an enclosing chamber (controlled frictional braking). Drag factor controls the rate of deceleration of that wheel and influences the speed and timing of the erger's inputs (muscular exertion) for best effect, but the erger produces all the work.

Sorry, Jackarabit but you have it a bit backwards. Drag factor is a numerical representation of the rate of deceleration of the flywheel and it is calculated and revised by the monitor on every stroke by viewing the stream of pulses that are coming from the flywheels interaction with the generator/pickup unit. Using this drag factor and the known moment of inertia of the flywheel the monitor calculates power and converts it to the various units we view on the screen. Drag factor is controlled by the amount and density of the air passing through the flywheel, which the user controls primarily by setting the damper. C2JonW

I thought I can get a clear yes/no answer.

Is this a correct: The performance calculation is solely based on the energy(watts) the rower puts in. Energy is determined by the rpm of the flywheel(when pull)and the weight of the flywheel(changed by the DF). PM maps the energy input to the speed of a boat. This is the only explaination makes sense to me.

Yes, that's correct. The machine measures work that you put into the flywheel. Changing the drag factor only changes how that work is applied to the fan. A very rough analogy is changing gears on a bicycle- you can pedal hard or easily in any gear. C2JonW

Only "a bit backwards," Jon? Probably the quotidien confusion of df with the setting of the mechanical shutter. I won't be the last to trip over this curious metadynamics.

bcjm wrote:I thought I can get a clear yes/no answer.

Is this a correct: The performance calculation is solely based on the energy(watts) the rower puts in. Energy is determined by the rpm of the flywheel(when pull)and the weight of the flywheel(changed by the DF). PM maps the energy input to the speed of a boat. This is the only explaination makes sense to me.

To the first sentence, yes. To the second - not at all. For one thing, the weight of the flywheel is constant. And, as its name implies, the drag factor is determined by the rate at which the flywheel is slowed by the drag of the air. With regard to the third, it is based on a "standard boat" and I believe that the 4x was the particular boat chosen.

c2jonw wrote:A very rough analogy is changing gears on a bicycle- you can pedal hard or easily in any gear. C2JonW

Very rough indeed. I would think that a much closer analogy would a variable parachute drogue pulled behind a bike on a windless day. Then there is the matter of the intermittent nature of the force applied to the erg as opposed to the relatively continuous force applied to the crank of the bike. There is no doubt a periodic variability of the amount of force applied on a bike, but it does't drop to zero. I realize that C2 uses the gear analogy because it sort of gives a feeling for the drag effect, but I think that it has led to a lot of confusion on the part of those who try to draw additional conclusions from it. I also realize that my drogue alternative is unlikely to help anyone new to erging.

Say I row one minute at the rate of 20 SPM in DF 100 and DF 200. Which one results in more distance? I assume DF 200. Correct?

NO. "Distance" is related only to the amount of Work done.
The total amount of Work we do in one minute is: Average Handle Force x Net Length of Stroke x Number of Strokes. We control all these items.
So WE control the amount of Work done, not the machine.


What drag actually gives us, is control over the flywheel speed when we take the catch at the start of the stroke, by slowing the flywheel during recovery.

If the drag is zero, the flywheel never slows down and soon spins too fast to go any faster; so no Work can be done.
If the drag is infinite, the flywheel cannot move, so no Work can be done.
So we set drag somewhere in between.

Since boats and flywheels go fast, body action has to be fast too. Faster body action lets us use lower forces by moving the handle further in any give time. High forces make me tired and can even stop me after 20 strokes, so I use low drag.

I'm currently using DF (drag factor) 78-80, and can deliver up to 200W at rating 23, if I want to. I'm 6'2 (188), 75y.
I've put a filter over the air inlet to keep the fan clean and reduce drag to that level.

If and only if the drag is so low that you cannot work as hard as you want (as measured in Watts), increase it slightly.

Very rough indeed. I would think that a much closer analogy would a variable parachute drogue pulled behind a bike on a windless day. Then there is the matter of the intermittent nature of the force applied to the erg as opposed to the relatively continuous force applied to the crank of the bike. There is no doubt a periodic variability of the amount of force applied on a bike, but it does't drop to zero. I realize that C2 uses the gear analogy because it sort of gives a feeling for the drag effect, but I think that it has led to a lot of confusion on the part of those who try to draw additional conclusions from it. I also realize that my drogue alternative is unlikely to help anyone new to erging.

Bob, I knew I was going to get called out on that and consider the message delivered... I used the bicycle analogy to point out the idea that the erg is not like a weight stack at the gym where bigger numbers mean more work. The erg, like a bicycle, is a reactive device that responds to user input and the gear/drag factor does not determine how hard the workout is. As you point out, analogies can fall apart pretty quickly upon closer examination.

How about this one- think of a 2K piece to be analogous to a pile of sand that you are tasked to move with a shovel- carrying each shovelful some distance and depositing it, then returning to the pile and repeat. You can use any size shovel you wish (drag factor), put as much sand in the shovel as you wish (pace), take as much time to deliver the sand and return for the next shovelful (rate and ratio).....for any given person there's an optimum combination of these factors to get the 2K sand pile moved the quickest........C2JonW