yehster wrote:PaulS wrote:
The Erg jumping in the direction of the flywheel ("backwards") would certainly not cost him any time, since all it does is allow for a quicker engagement of the flywheel clutch. In fact, when Lisa stepped on the Erg to keep it from moving, it would cause Henrik to bring his mass up to speed to catch the flywheel rather than the erg mass moving the other way, this may well have complicated it for him. It also doesn't translate directly to bad boat moving, just as when the Erg is on slides the backwards travel of the Erg does not imply increased boat check. (one would have to watch the seat relative to the floor) Just think of henrick being on Slides with a lot of friction to deal with.
I buy your argument that erg jumping does not necessarily reflect poor OTW technique, but I disagree that it doesn't hurt your time. There is non-zero energy dissipated to friction that won't be registered to the PM. You can calculate this loss, which is going to be equal to F*d, where d is the distance the erg moved, and F is the force of friction, equal to the mass of the system times the coefficient of kinetic friction.
I believe that you could approximate the distance lost by computing this energy dissipation (call it E) and dividing by the power being recorded by the PM at that instant to get a time in seconds. Multiply that time by the speed the PM is using at that moment, and volia, a distance. I'm sure I'm ignoring some terms, but this ought to be close enough from an "engineering" standpoint. That said, the distance lost to the meter is going to be less than the distance the erg moved. However, without Lisa stepping on it, he would lose some distance every stroke.
This scenario is different than being on slides, because the energy that goes into moving the erg on slides is returned to you through the bungies, where as without them, all that energy is dissipated as friction to the floor.
Well, it costs him less energy to drive the Erg backward than to bring his body to a stop and reverse his momentum. I think "by defnition" would be the appropriate description.
If he were pulling the Erg forward during the recovery, not that would indeed be quite an energy use that is not registered on the PM, but it's not for anyone, and only serves to complicate the change in direction at the catch. All the forces have to balance.
There is evidence for this in his remarkable VO2Max testing over a 6 minute time, on slides. Where he nearly nicked 2000m in 6:00. Which he has not really come all that close to when on the grounded Erg. (publicly reported anyhow)
Theoretically, the Slides don't really need the bungees at all, but due to imperfections in us as humans, they do provide the slight balancing forces required to keep us centered. In fact, a perfectly level and very long set of near frictionless tracks would be a great way of really sorting out rowers for technique issues, since there would be 3 possibilities.
1 - No net system movement (Perfectly balanced - Good)
2 - Net movement in the direction of the flywheel (Bad)
3 - Net movement in the direction opposite the flywheel (Good)
This really addresses how well the athlete manages the varying momentum of their body in the appropriate directions, something that is important in a boat, and even on the Erg to a lesser degree.
Of course this only applies if the rails are of very low friction in both directions, if the friction is high then we can't tell anything, because it's too easy for the rower to control what they do with the available friction.
