Rower is too hard to row

[nick rockliff]

...
There is no difference between before and after. Bungee makes no difference.

What was the bungee tension before the revision and what is it after the revision ?

Why would you need to check that? The new bungee is a straight swap like for like. You just fit it the same way as the old one comes off.

[Nomath]

Because the statement "bungee makes no difference" should be based on facts, in this debate on bungee tensions.

[nick rockliff]

Because the statement "bungee makes no difference" should be based on facts, in this debate on bungee tensions.

You can debate all you like but it makes no noticeable difference when rowing. This is what this thread is about, not some mathematical theory which proves absolutely nothing.

[Nomath]

This is not about mathematics, but physics. The drag factor and the bungee tension are two quantities that make a perceptual difference while rowing. To find out whether they explain time or power differences, you need a physical model and real numbers.

[Slidewinder]

Five seconds is a long time in the closing moments of a race, and five seconds very definitely separates the winner from the loser. In an on-line race with a bungee cord strength difference of 1 to 3 kg between machines, the PMs could be showing in the time/distance display the actual winner as the loser, and the actual loser as the winner.

In OTW rowing there are races where specific lanes are in a serious disadvantage due to the wind. Life isn't fair, and racing certainly isn't.

Further, since a weaker bungee cord is an advantage, there is the possibility of tampering to create this advantage. All this is not good.

There are very clear rules what contestants can and cannot do during a race.

I was referring to the possibility of bungee cord tampering by unscrupulous contestants in online races. There would be no one to witness prior race tampering.

Every effort is made in sports competitions to create a level playing field. If something could be done about the wind in OTW competitions, something would be. In an indoor rowing competition it is expected that parity will exist between machines. If it is determined that variations in elastic cord strength result in unfair races, the sensible response is not to shrug and say, as you do, that "life isn't fair, and racing certainly isn't." The sensible response is to see this as a real problem, and to think about how the problem could be eliminated. Concept 2, I submit, knows this is a problem. That is why indoor rowing competitions use new machines - so that all of the bungee cords will be fresh and new and as close as possible to equal strength. But with time and usage that equivalence is lost.

[Slidewinder]

Bungee cord?


I’ll get my coat

Now look what you've done

So, let's all laugh at the most probable cause of discrepancy between C2 rowers. Maybe laughter and ridicule will make it go away.

Before laughing. you should think about what a 1 kg stronger elastic cord means in terms of extra work required in a 2k race. Assuming 200 strokes of 1.5 metre length, then the rower must apply the extra 1 kg of force for a distance of 300 metres. This is equivalent to hoisting a 10 kg bag of potatoes through a vertical distance of 30 metres. Not sure about you, but in a race I would prefer to be on a machine that doesn't also require me to lift a heavy bag of potatoes while I am trying for my best time.

[nick rockliff]

Now look what you've done

So, let's all laugh at the most probable cause of discrepancy between C2 rowers. Maybe laughter and ridicule will make it go away.

Before laughing. you should think about what a 1 kg stronger elastic cord means in terms of extra work required in a 2k race. Assuming 200 strokes of 1.5 metre length, then the rower must apply the extra 1 kg of force for a distance of 300 metres. This is equivalent to hoisting a 10 kg bag of potatoes through a vertical distance of 30 metres. Not sure about you, but in a race I would prefer to be on a machine that doesn't also require me to lift a heavy bag of potatoes while I am trying for my best time.

Rubbish

[JaapvanE]

I agree that 5 sec on 2K doesn't look like a huge difference. But put yourself in the position of the topic poster. He finds that he can row 5 sec faster, possibly a PR, on heavily used ergs in the gym, but not on his home machine that is in better condition. Wouldn't you be disappointed and look for an explanation?

I have a very similar experience in this respect, where badly maintained, literally decade old machines feel smoother than my personal brand new one. And as I have a strong mechanical background, it partially intregues me as my day job is in maintenance and installation performance management and I'd expect decades of neglect to leave its mark in performance.

However, the behaviour itself isn't totally against common knowledge. In heavy industry we have a wear-in period where the installation has to "settle in": we are not allowed to push it beyond a certain limit far below 100% power, to allow axles to allign, sprockets to wear in, etc.. Also in cars, the parts have to wear in. That is why we often replace parts of installations, as old worn in mechanical parts do not work well with new parts. Even my bike has a very explicit replacement regime where the drive belt and driven cog must always be replaced at the same time. What wear-in does is let the parts' friction do its work and wear in things like bearings, cogs and chains to remove any obstructing production tolerances. It takes a couple of thousand kilometers, and how the engine adapts is a bit unpredictable, but then the engine is at its mechanical best. I can imagine that is also what happens in a brand new C2. And as most sprockets, bearings etc. are not measured in the dragfactor, you feel it, but it isn't measured.

[Nomath]

.... I can imagine that is also what happens in a brand new C2. And as most sprockets, bearings etc. are not measured in the dragfactor, you feel it, but it isn't measured.

The home machine of the topic poster is not brand new. Read his first post!
We need other factors to explain the difference, which has been reported here in several other topics.

I asked you and others to measure the bungee tension of available ergs. Somehow this seems like a forbidden request, because I didn't see any measurements yet. As a mechanical engineer, you should take this seriously or come up with an alternative explanation.

[JaapvanE]

Regarding the time ratio drive:recovery, you should not be misled by what the Performance Monitor tells you about the drive time. The PM cannot see the initial aceleration after the catch. The PM only start to measure power input as the handle speed matches the speed of the flywheel. The same holds for the last part of the drive when the handle speed drops below the corresponding speed of the flywheel. Both time periods are part of the drive and correspondingly reduce the recovery time.

My assumption of a drive : recovery ratio of 1.5 : 1.0 is not unrealistic, especially for an all-out effort. Shorter recoveries are the main way to speed up if leg and arm force are limited. I am not talking about a calm "pull strong - rest in the recovery" stroke often advocated here by jamesg.

In OpenRowingMonitor we also measure drivetime and recoverytime, with a slightly different definition. Let's look at the definitions before we continue:

• C2's definition: a drive is where the flywheel accelerates. In practice, this means that there is a netto positive force causing this acceleration to happen.
• ORM's definition: a drive is when the flywheel's deceleration is less than can be explained by the presence of the dragforce alone, with a 98,5% certainty. In essence, we look if the deceleration matches the deceleration caused by the flywheel drag alone. If it does, we are in the recovery.

ORM's definition isn't perfect: there is a slight moment (i.e. the catch) which is incorrectly considered the recovery: we can only measure once caught. Same goes for the finish: there is a moment where the subject loses contact with the flywheel but still could be moving. Across several rowing subjects and machines, we typically see that ORM's drive is consistently 0.02 (competitive rowers) to 0.04 seconds (recreational rowers) longer than C2's. Video analysis of these rows compared to ORM's result show that the catch takes some time, but nowhere near the times you suggest, especially at high stroke rates and a pace below 2:00/500m. Typically, this is in the range of 0,005 to 0,01 seconds.

As said, when rowing at 2:00/500m, having a drive time over 1 second is nearly impossible, regardless how you measure it.

My thesis is that also the bungee tension has a significant effect on the time/power. I suggest that you measure the bungee tensions of your own rower and possibly the rowers on the gym. It's easy and quickly done with a luggage scale. If you report them here we build up a base of facts rather then vague perceptions.

I haven't got a scale myself, but I found this video quite interesting: https://www.youtube.com/watch?v=15KT3efpeTQ

John from RowAlong set two machines side by side (one a decade old, one brand new), and tested their bungee strength, and what time he could do on both. Spoiler: the times are identical.

[JaapvanE]

I asked you and others to measure the bungee tension of available ergs. Somehow this seems like a forbidden request, because I didn't see any measurements yet.

Because I don't have a luggage scale perhaps?

As a mechanical engineer, you should take this seriously or come up with an alternative explanation.

I am not in a contractual obligation with anyone on this forum, so I am not required to do anything. And as said, my alternative explanation is that the machine has to wear in. Given the low forces compared to the materials used, could take a couple of million meters though...

[JaapvanE]

I was referring to the possibility of bungee cord tampering by unscrupulous contestants in online races. There would be no one to witness prior race tampering.

Every effort is made in sports competitions to create a level playing field. If something could be done about the wind in OTW competitions, something would be. In an indoor rowing competition it is expected that parity will exist between machines.

If people want to fake results, they will:

• https://www.dcrainmaker.com/2019/10/bri ... ating.html
• https://www.dcrainmaker.com/2020/11/zwi ... sorts.html
• https://www.dcrainmaker.com/2022/03/zwi ... nging.html
• https://www.dcrainmaker.com/2022/12/zwi ... ifier.html
• https://www.dcrainmaker.com/2023/03/pre ... hoosh.html

And these are very serious competitions with serious prizes, that require two (!) independent and calibrated power meters to be active during the race to make it a valid entry for the race.

There are much easier and much more effective ways to cheat on a C2 than meddle with the bungee. Some of C2's making (like using identical PM5's for the Model C and RowErg without specific check on the consistency of the signal), some because you can't control specific environmental conditions which actually benefit the rower (tilting the machine...). Or modify the flywheel to reduce its inertia significantly, allowing the dragforce to be reduced as well while keeping the same dragfactor. And let's not go the route of signal emulation, which can be done with $20 of equipment. Or use OpenRowingMonitor in PM5 simulation mode with fake data in the sim, I can really row below 1:00/500m.

I'm involved in discussions with the people actually involved in technically setting up online racing, as the BIRC 2023 will include an online race on december 10th. In practice, it is a demonstration event aimed to be as inclusive as possible, as everything surrounding equalizing machines is nearly impossible. For example: on a RP3 people are quicker than on a C2, just because the RP3 moves the head of the machine instead of the rowing person's own body. As it stands now, both these machines are going to be used in competition, does that sound fair?

If it is determined that variations in elastic cord strength result in unfair races, the sensible response is not to shrug and say, as you do, that "life isn't fair, and racing certainly isn't." The sensible response is to see this as a real problem, and to think about how the problem could be eliminated. Concept 2, I submit, knows this is a problem. That is why indoor rowing competitions use new machines - so that all of the bungee cords will be fresh and new and as close as possible to equal strength. But with time and usage that equivalence is lost.

Nope. As long as they are maintained and stored in the same manner and used about as intense, they age identically as well. Especially given the tremendous robustness of these machines over time (as most people using them in gyms can attest to), they age more or less at the same pace and thus be in nearly identical conition. You might end up with a fleet of 100 rusty machines, but across that fleet, they'll row equally good/bad.

[Slidewinder]

There are much easier and much more effective ways to cheat on a C2 than meddle with the bungee.

I mentioned the possibility of cheating by tampering with the bungee cord and you reply with a lengthy, multi-linked diatribe on the improbability of that occurring. Maybe you are correct that bungee cord rigging is unlikely, but this doesn't change the fact that if differences in bungee cord strength affect PM readouts, then this is a problem. Surely everyone here is interested in the advancement of rowing exercise technology. If so, then if differences in bungee cord strength are shown to affect machine to machine equivalence, we should confront and deal with it. There is nothing to fear. C2 already, years ago, dealt with a similar problem - damper settings. The invention of the self-calibrating monitor took the damper setting into account so that no competitive advantage could be gained by playing with that setting. Here, instead of a variable damper we have a variable elastic resistance. If the PM monitored the tension profile of the elastic cord via a force transducer then the power required to stretch the elastic cord could be calculated stroke by stroke and added to the PM calculation of user power delivered to the flywheel, and the PM time/distance display adjusted stroke by stroke accordingly. This improvement sounds like it would be right up your alley, JaapvanE.

[JaapvanE]

Surely everyone here is interested in the advancement of rowing exercise technology. If so, then if differences in bungee cord strength are shown to affect machine to machine equivalence, we should confront and deal with it.

If it would affect times, which I highly doubt, the solution is simple: for races the organisation must check the chain/bunge tension before a race. A simple rule by World Rowing and its done.

Drag calculation is easily done as the flywheel speed is already measured and failure of that sensor kills all metrics anyway. Adding additional sensors to a device for measuring bungee tension like a C2 is the road to hell: you introduce a lot of complexity and failure modes while gaining nothing significantly. Overengineering at its worst. There is a reason why in many industries we still believe in human inspection instead of wiring up the place.

[Slidewinder]

Surely everyone here is interested in the advancement of rowing exercise technology. If so, then if differences in bungee cord strength are shown to affect machine to machine equivalence, we should confront and deal with it.

If it would affect times, which I highly doubt...
Adding additional sensors to a device for measuring bungee tension like a C2 is the road to hell: you introduce a lot of complexity and failure modes...

"If it would affect times, which I highly doubt..." Many C2 rower users have reported on this forum a similar experience to the OP here, often complaining of a much greater machine to machine disparity. So you have their testimony, and their testimony is supported by the physics. They do not complain because of possible unfairness in competitions. They just want a rower with a PM readout they can depend on.

"You introduce a lot of complexity..." A lot of complexity by adding one sensor? That would make a total of two. I think 21st century technology can handle it.