C2 Erg Prototype

[johnlvs2run]

What you want to say

I already said what I wanted to say.

[c2jonw]

Lots of speculation here and of course this sort of feedback is all good information for us. What we know is that the HOC prototype (shown in the short video clip at the beginning of this thread) was very sensitive to ones rowing technique. About half the people that used it would get into a sort of selp-perpetuating oscilation that had them bumping from one end stop to the other, as demonstrated by the young woman in the short clip. Typically these people did not like the prototype. The other half had rowing styles that kept them moving slightly somewhere between the end stops but without bumping, and typically these people liked the prototype. So from that information we came up with the CRASH-B prototype, which fundamentally has the same drive mechanism but a different method of restraining the seat which is a lot more forgiving of rowing technique. We've shown this prototype at several coaches clinics and it has been used by numerous elite level athletes with mostly positive feedback all around. There's still a lot of work to fine tune the feel of it, and then even more work to get it to production, if we decide that's what we want to do. C2JonW

[Nosmo]

It also looks like one would be sweating on the flywheel. I'd guess that C2 is aware of that would want to deal with it

[bloomp]

To clarify my point - the issue of a rowers center of mass is redundant - here are some pictues.

Some British chap at the finish


Some British chap at arms away


Some British chap at the catch


The lines drawn in show an approximate center of mass. It BARELY changes. Maybe six inches (15cm) from finish to arms away, then it doesn't change at all as he approaches the catch. It would change even less with a smaller rower (less mass on the upper end of the body). That sort of change, John, is meaningless for your suggestion of 'balance'. Especially because the center of mass is buried so close to the hips, there is even less of an effect because it's practically on the seat.

EDIT:
Finally, the concern is with the transfer of momentum, not just the center of mass. From the center of mass you can calculate the moment of inertia. L=I*omega is the number that matters - not the minimal change in center of mass.

[Bob S.]

Lots of speculation here and of course this sort of feedback is all good information for us. What we know is that the HOC prototype (shown in the short video clip at the beginning of this thread) was very sensitive to ones rowing technique. About half the people that used it would get into a sort of selp-perpetuating oscilation that had them bumping from one end stop to the other, as demonstrated by the young woman in the short clip. Typically these people did not like the prototype. The other half had rowing styles that kept them moving slightly somewhere between the end stops but without bumping, and typically these people liked the prototype. So from that information we came up with the CRASH-B prototype, which fundamentally has the same drive mechanism but a different method of restraining the seat which is a lot more forgiving of rowing technique. We've shown this prototype at several coaches clinics and it has been used by numerous elite level athletes with mostly positive feedback all around. There's still a lot of work to fine tune the feel of it, and then even more work to get it to production, if we decide that's what we want to do. C2JonW

Jon,

Thanks for the clarification. Something was said at the C-Bs that gave me the impression that the stretcher assembly might be weighted to give it more inertia. On thinking it over, I wondered if it was done to simulate the weight of a boat (about 30#). Is the stretcher assembly that heavy or did I just get the information screwed up? It was a busy, confusing time with lots of snatches of conversation going on, so I am not sure of what was said nor who said it. I would appreciate it if you could straighten me out on this.

On my short trial of the C-B prototype, I liked the feel of it very much and I hope that I am still around to use one if and when it gets into production.

Bob S.

[Nosmo]

To clarify my point - the issue of a rowers center of mass is redundant - here are some pictures.

Actually Paul it doesn't clarify anything. Trust me on this.

I think you are only thinking of only the vertical position of the Center of Mass, which hardly changes. John is referring to the horizontal position.

[bloomp]

Well that'd be his fault for not stating it. In fact it makes even less sense to consider 'horizontal' center of mass - of course it moves, there has to be some displacement. The advantage to the prototype is that it moves much less than on the grounded erg. Why would he want more center of mass movement if that's what C2 is trying to shift away from? The more fixed your mass remains, the more like rowing on water. Remember - the boat runs underneath you to a certain degree.

Maybe if I had a pencil and paper I could show this better, but either he's talking about how the back swings and the center of mass changes slightly, or he's just making up about why it would be better to have MORE center of mass motion (e.g. displacement along the rail).

[JRBJR]

bloomp,
I think you're correct: on a c2 erg on slides, the center of body mass shifts fowards and backwards primarily from hinging the back forward and backward from the hips. Xeno has discussed this factor in several of his workout DVDs, noting that with proper rowing technique the shift should be quite small, only a few inches, causing the seat to essentially remain almost stationary with respect to the sliding erg.

[johnlvs2run]

bloomp,
I think you're correct: ... with proper rowing technique the shift should be quite small, only a few inches, causing the seat to essentially remain almost stationary with respect to the sliding erg.

http://www.c2forum.com/viewtopic.php?p=128608#128608

the center of gravity of the body is only slightly above the hips, i.e. slightly above the seat,
and does NOT move back and forth to any great degree on the slides, nor should it on the prototype.

Are you actually as stupid as you sound?

Yeah, who is the stupid one now.

[bloomp]

Yeah, so what are you talking about if what I've said is wrong? There is no huge fluctuation of the center of gravity on the prototype. If I had pictures of finish/catch positions on it, you would see the same thing as on a model C/D/E

[peterhowd]

Paul - be sure to state your frame of reference for the horizontal position of the CoM in order to make your statement valid for C, D, E (with and without slides) the prototype. Obviously it makes a big (relative) difference. If you are only talking about C,D,E on slides, say so.

Peter

[c2jonw]

Thanks for the clarification. Something was said at the C-Bs that gave me the impression that the stretcher assembly might be weighted to give it more inertia. On thinking it over, I wondered if it was done to simulate the weight of a boat (about 30#). Is the stretcher assembly that heavy or did I just get the information screwed up? It was a busy, confusing time with lots of snatches of conversation going on, so I am not sure of what was said nor who said it. I would appreciate it if you could straighten me out on this.

On my short trial of the C-B prototype, I liked the feel of it very much and I hope that I am still around to use one if and when it gets into production.

Bob, Yes, we did add weight to the stretcher assemblies of both the HOC and CRASH-B prototypes. We started out with them being fairly light, wanting to see how far we could push the idea of minimizing the moving mass. But something felt wrong- no momentum, perhaps- so we started adding weight. Both assemblies ended up at around 25 or 30 pounds.
Reports from our field testing continue to be positive. C2JonW

[Bob S.]

Bob, Yes, we did add weight to the stretcher assemblies of both the HOC and CRASH-B prototypes. We started out with them being fairly light, wanting to see how far we could push the idea of minimizing the moving mass. But something felt wrong- no momentum, perhaps- so we started adding weight. Both assemblies ended up at around 25 or 30 pounds.
Reports from our field testing continue to be positive. C2JonW

Thanks for that, Jon. It is interesting that the experimentally derived weight, 25-30 pounds, is the same as the weight of a typical single shell.

Bob S.

[Rockin Roland]

What about the sound coming from flywheel/fan shroud of the new C2 prototype? Is it identicle to that of a model D/E erg?

The reason I ask is because I absolutely love the grunty macho sound of the Oartec slider and new Rowperfect. It's part of the joy of rowing on such ergs. In pursuit of a quieter erg for gyms C2 have muffled their ergs to a sickly tinny sound. It becomes unpleasant to listen to when you need to spend some time on them.

The Japanese have removed all the character from their Lexus cars by making them far too quite. You can't hear the engine anymore which makes them boring to drive. C2 is going the same way with their ergs. What about transfering the new C2 prototype from a wimp to a sexy beast by beefing up the sound it emits?

[JRBJR]

No doubt Jon knows the specific details, but I'd bet that C2 desgined the Model C, D, and E ergs to be much quieter than the Models A and B because a lot of potential customers specifically requested it. I have an upgraded Model B on slides and it's loud flywheel and chain leave no doubt that the erg is doing its job, but it forces me to shut our home's exercise room door and turn up the TV quite a bit louder than I'd need to with C2's subsequent units. I haven't heard the Oartec Slider yet, but YouTube videos of the new RowPerfect confirm is still a real noisemaker, even more than my Model B, with a clanking metal on metal clatter that would annoy me (and my wife in the next room) far more than a quiet C, D, or E. Which only proves, of course, to each his own.