Dynamic vs Stationary

[NavigationHazard]

I'll say it again. On a properly maintained, properly rowed C2 there simply is nothing like a "20-30cm" delay before the flywheel engages on a drive. It's hard to demonstrate this visually without instrumentation but I'll try.

Here's a screenshot from the side of a C2 Model D being rowed with the damper cover removed. The point is that the nut at the end of the axle rotates at the same speed as the flywheel when the ratchet/sprocket is engaged and does not when it's not engaged:



The strokes here were about 1:35 pace r24; I was paying roughly zero attention to constant hand height so there's quite a bit of up-and-down chain bobble. At full speed about all you can tell is that the axle starts to rotate with the flywheel on the first stroke and slows down more than the disengaged flywheel after I handle down.

Here's the same video at 1/8 speed:



Slowed down like this, it's possible to see clearly the hands come into the left side of the frame at roughly 32 seconds, 52 seconds and 1:10 seconds. At 1/8 speed it's also possible -- barely -- to make out the 'catch slip' inherent in the machine as the ratchet engages (watch the rotation of the nut pause almost imperceptibly as the hands reverse direction). As I said earlier, it's in the neighborhood of hundredths of a second.

As Tinus said, the notion that there's 20-30 cm of slack inherent in the machine is silly. You can put slack into the drive by arriving at the catch prematurely; you also can put slack into the drive by pulling the handle more slowly than it needs to move in order to engage the ratchet, and only catching up partway through the drive. But the rower is to blame for those problems, not the machine. It's like trying to condemn your driver for all the golf balls you hook or slice.

[johnlvs2run]

The empty catch is caused by a delay in the spockets catching up with the fan.

As pointed out earlier, the empty catch is hardly evident at low ratings, if at all.
It is not as evident at 18 to 24 spm, which is not evidence that it doesn't appear at 36-45 spm.
There is zero delay on the very first stroke, because the sprockets are completely connected with the fan.
Low ratings give the sprockets time to catch up with the fan, so the empty catch is also not evident at low ratings.

The delay is more evident at higher ratings, at lower drag settings; and possibly at longer stroke lengths, the first two factors being equal. Therefore the delay is more evident at 38spm with a 120df, than at 24spm with a 160df.

The delay is primarily a result of machine design, secondarily of rating and drag factor, not of skill or technique.

Making the erg more dynamic helps the erg to be more buoyant, which is excellent, but does not remove the delay between catch and sprocket engagement with the fan.

Getting rid of the delay between catch and engagement of the fan is important in order for rowing machine skills and scores to become similar to the movements and skills utilized in sculling and rowing on the water.

[hjs]

The only delay is not catching the fan, the same like otw, the water below the boat has to be caught, it is moving below the boat. The higher the speed and shorter the stroke the more slack we have, but that is just the way it should be.

[johnlvs2run]

The only delay is not catching the fan, the same like otw, the water below the boat has to be caught, it is moving below the boat. The higher the speed and shorter the stroke the more slack we have, but that is just the way it should be.

The blade in the water is ALWAYS in contact with the water.

[Byron Drachman]

What a clever idea by Jon to demonstrate the "catch slip" on the erg.

The only delay is not catching the fan, the same like otw, the water below the boat has to be caught, it is moving below the boat. The higher the speed and shorter the stroke the more slack we have, but that is just the way it should be.

It is an interesting point that on the water some of the arc near the catch is wasted. You can get some indication by looking at the splashes at the catch. In Rowing Faster, edited by Voker Nolte, M. Spracklen says you want a V-shaped splash with the front splash a little larger than the back splash. Some coaches want the back splash to be larger than the front splash, which would mean some extra checking of the boat but presumably getting locked in for a longer arc more than compensates.

The blade in the water is ALWAYS in contact with the water.

Hi John,
Actually if you get the timing just right, a "hole" in the water forms and at the finish you can remove the blade cleanly with almost no contact with the walls of the "hole," and after the extraction the "hole" closes.

[Carl Watts]

The only delay is not catching the fan, the same like otw, the water below the boat has to be caught, it is moving below the boat. The higher the speed and shorter the stroke the more slack we have, but that is just the way it should be.

The blade in the water is ALWAYS in contact with the water.

Yes but the same principal applies, your not doing any "Work" until the blade is moving with an applied force against the water, the same with the Erg, as soon as your applying a force or sufficient rpms to exceed the flywheel rpms the bearing locks up and drives. Besides there is no other way I can think of doing it, the same bearing set-up exists on the Dynamic erg anyway correct ? The big difference is that your body weight is no longer such a significant factor, which raises another question, does this mean that heavy weights now have an even bigger advantage over lightweights on the Dynamic ?

[hjs]

The only delay is not catching the fan, the same like otw, the water below the boat has to be caught, it is moving below the boat. The higher the speed and shorter the stroke the more slack we have, but that is just the way it should be.

The blade in the water is ALWAYS in contact with the water.

No it's NOT, you only have contact if you move the oar faster then the water speed below the boat, and if the speed is lower you even stop the boat, on an erg at least that is not possible

[johnlvs2run]

An interesting experiment would be to have two (or more) rowers of similar abilities, doing the same type
of repetition session on an Oartec Slider, and a C2 Dynamic. The session could be something like 10x 3 minutes
with 2 minute rests, changing ergs after each repetition. Thereafter the times could be compared to see which
of these, the Oartec Slider or the C2 Dynamic, had the closest times between the two rowers.

[Rockin Roland]

Actually there is definetly some chain slack at the catch on a C2 erg. However it's certainly not 20-30 cm as John is trying to argue. The chain slack at the catch becomes very obvious when you get straight off a C2 erg and get onto a Rowperfect. The Rowperfect has instant connection and I'm not saying that just to push some sort of Rowperfect propaganda.

The problem is that none of you blokes that have posted above would have any clue about this simply because none of you have ever rowed on a Rowperfect to feel this difference. But the slack is certainly there. That's one of the reasons people develope technique problems from rowing on C2 ergs. The feeling at the catch is not right. If you think so then I'd hate to see your technique out on the water because I reckon you'd have issues at the catch.

[johnlvs2run]

The chain slack at the catch becomes very obvious when you get straight off a C2 erg and get onto a Rowperfect. The Rowperfect has instant connection and I'm not saying that just to push some sort of Rowperfect propaganda.

Roland,
Thanks for that information.
What do you think it is about the Rowperfect vs C2 that gets rid of the chain slack?

The Rowperfect indoor sculler is $3400 shipped to my door, including $250 for shipping. They certainly do jack up the price, including the shipping. So I'd need to pay almost 3 times the comparative value to obtain one. Even so, it does look like a good machine, and I like the monitor, which does have input for weight, or can be adjusted to C2 values (95kg in a 4-). However I would just hate to pay more for something than it's worth. Why should I pay $250 for shipping when it should be no more than $100??? The machine is loud and there is no online community. I was considering to get one a couple of weeks ago but put the Oartec Slider and C2 Dynamic ahead because of the price, and the companies are much more serious about getting their dynamic ergs out there. I could see myself having a Rowperfect and just no motivation to use it. However I hope it keeps becoming more competitive with the others.

By the way, 1xsculler came up with a DIY home built dynamic erg using a static C2 machine and parts, which works like the Rowperfect and looks very good. I was considering to go that route too, but figured the chain slack would still be the same. So I'm wondering why a Rowperfect would be any different.

[Citroen]

By the way, 1xsculler came up with a DIY home built dynamic erg using a static C2 machine and parts, which works like the Rowperfect and looks very good. I was considering to go that route too, but figured the chain slack would still be the same. So I'm wondering why a Rowperfect would be any different.

Why did you bother posting that link to that thread? There's no info in that thread, all the videos (except the one for the entirely stupid Wii rower - demonstrated by a girl with crap technique) have been deleted by the author.

[Rockin Roland]

The reason for the differences at the catch between the C2s, Oartec Slider and Rowperfect is due to their flywheel clutch mechanism. The Rowperfect flywheel clutch is designed to give a feeling of instant resistance at the catch. Whereas the C2 flywheel clutch has more give in it. The Oartec Slider is somewhere in between the two.

As all three have different clutches you are going to experience different catches between them. I'm not sure if using the software associated with these ergs will clearly demostrate this as it depends on which point the software starts reading the signal from the flywheel.

[johnlvs2run]

The reason for the differences at the catch between the C2s, Oartec Slider and Rowperfect is due to their flywheel clutch mechanism. The Rowperfect flywheel clutch is designed to give a feeling of instant resistance at the catch. Whereas the C2 flywheel clutch has more give in it. The Oartec Slider is somewhere in between the two.

As all three have different clutches you are going to experience different catches between them. I'm not sure if using the software associated with these ergs will clearly demostrate this as it depends on which point the software starts reading the signal from the flywheel.

Roland, thank you very much for that information, very helpful!

C2, if you're listening, how about an improvement in the clutch so there can be instant resistance at the catch.

In addition to improving the rowing mechanics, this would probably reduce injuries to the ribs.

[NavigationHazard]

No. The ratchet on the C2 can be engaged in roughly 0.01 second. How much more instantaneous do you want or need? You don't get instantaneous catches in a boat either, as the blade does not reach proper depth instantaneously. You can row the blade in to try to apply power from the moment the bottom edge contacts the surface of the water but that's creates its own -- significant -- set of catch problems.

The difference at the catch between a RowPerfect and a static C2 is overwhelmingly the well-known difference between a dynamic erg and a static erg. That has to do with lowered inertial force on the footstretcher potentially affecting handle turnaround, >not< some significant difference in the clutch mechanisms.

[Carl Watts]

Right so basically the lower mass of the moving part of the Dynamic is lower than your body mass (well certainly way less than mine) so the accelleration is faster with the same force applied and hence there is less perceived slack.

As Nav said are you seriously going to start an argument over 0.01 of a second ? So whats the Dynamic, up to 3 or 4 times faster for a heavy person (Acceleration = Force / Mass)? who cares ? The one way locks up and transfers 100%power the instant your driving the sprocket faster than the flywheel if it is working as it should, end of story...why would you even think about trying to drive the flywheel when your at a point in the drive that is slower ?

The only "slack" is the time it takes you to accelerate in the drive and take up any chain slack, which is only an increasing problem at higher ratings, seriously it's not an issue if you row with the correct technique and look at your force curve and maintain your Erg to a race standard. I have bigger problems in keeping the slide spotlessly clean than slack at the catch.