Stretched Shock Cord & Time

[hjs]

Carl Watts,
Thanks for the link. It is interesting.

I say you are wrong that erg racing results are not comparable due to the shock cord.

It is basic physics that variations in shock cord tension between machines will affect times. Less tension (but not to the point of sluggish chain return), means less effort, means lower times.

At the risk of sounding like a broken record: Consider two machines, one of which requires one pound more force to stretch the elastic cord than the other. After one hundred strokes the user of this machine will have equivalently lifted a hundred pound weight through a distance - an effort not required by the user of the other machine. No deep understanding of Newtonian mechanics is needed to comprehend that this is going to affect times.

Some posters have presented the absurd argument that the more effort required to stretch the cord (ie: a higher tensioned cord) will actually result in reduced times. Even if we accept this nonsense, it is still an acknowledgement by those who believe this, that cord tension variations between machines affect recorded times.

Other posters have argued that none of this is a concern because only new machines with identical cord tensions are used in indoor rowing competitions. Maybe so, but many race participants train on used machines which have reduced shock cord tension. Consequently, they are recording incorrect training times. This is poor preparation for a competition.

This simply shows how inexpericed you are, I and many others train on lots of different machines and don't get a notion that there are differences and I am a very experient trained person, if I use a dumbel that is 1 kg off I alway notice the diference right away and on the erg my results are very evenly.

Your idea about 1 pound of difference is wrong, on new machines the difference is a lot less.

Plus your ignore the pull back effect, less tension will mean less given back energy, so even would be a 1 pound different the net effect would be quit a bit less.

And yes, you don't sound like a broken record, you are one. In principle you have a point, but that point is a lot smaller than you make it sound and you simply ignore any comments on your "considerations", at races there is not a one pound difference.

[Carl Watts]

As above, you cannot just look at the cord and the forces on its own.

Your body muscles are more efficient on the push or drive than the recovery so it stands to reason the energy stored in the cord assists you in the recovery.The Net result is as long as the cord is not too slack to do it's job you can forget about it.

Besides all of this what better system would you come up with to recover the chain ? Yes there are other methods but they will not be as simple and do you seriously want to have to plug the Erg into power to have some sort of electronic motor/servo driven retraction system that at the end of the day has no advantage and just adds complexity and cost to the Erg ?

[Cyclist2]

This is a fun academic discussion that I've been following. No way C2 is going to change it, and I think it's insignificant in any results, as has been mentioned numerous times. My question is; how do the other machines do the retraction of the handle? i.e. WaterRower, RowPerfect, LifeCore, etc. Is theirs any better? (OK , two questions).

[Slidewinder]

hjs,

re: "I don't get a notion that there are differences" between machines.

I am not talking about "notions" and subjective impressions. I am talking about the laws of physics. Variations in shock cord tension between machines affects times. Protesting against this reality is like protesting against gravity. If the physical laws of the universe are not to your liking, please do not direct your complaints to me.

re: pull back effect"

As I stated in an earlier post. A weight-stack leg press machine also helps the user return to the start position. Does this mean the exercise is easier with heavier weights? Of course not. The same applies to shock cord tension.

re: "on new machines difference is a lot less than one pound"

I acknowledge this. I am not referring to new machines.

[Slidewinder]

Carl Watts & Cyclist2,

I know WaterRower uses an elastic cord. I believe the others mentioned do too. So what? Common usage does not mean it's the best method. All bicycles used to have solid rubber tires until someone developed the pneumatic tire.

An improved chain return would be simple, constant in its return force, and never require adjustment or replacement.
How could this be accomplished? Here is one idea (not a solution, but a starting point towards one):

If, when the chain is pulled, instead of stretching an elastic cord, a weight were lifted through a distance, then on the recovery, the weight and the handle would be returned to the starting position. Unlike an elastic, gravity never wears out.

Of course there would be problems to solve. The weight, having mass, would also have inertia, so at the end of the stroke there would be a tendency for the weight to continue to move in the direction it was going and this would probably cause a jerk at the handle when a moment later the weight reversed direction. But there are methods to eliminate that.

You are probably correct that C2 will not investigate alternative chain return strategies. Why should they? If C2 groupies attack anyone who suggests that certain things about the machine could be improved, then C2 will not be motivated to change anything, and the groupies will continue to get what they deserve.

[Carl Watts]

Other options are not practical so you have either elastic bungee or a spring to choose from i.e like the seatbelt retraction system in your car which is NOT going to like repetition and has no advantages over a bungee cord.

We are not atacking you here but Concept 2 have run with the same system and have refined it over 20 years.

Bottom line is it works, is incredibly reliable, cheap, quiet and it also adds a certain "feel" to the erg during recovery.

If you have a well maintained Model D or E then it's a great Erg, smooth and fast and the cord simply is not a factor in your performance comparison against other rowers.

[bloomp]

First of all, what experience do you have with these machines? How much have you trained on them? Have you ever coached a team?

Look, it takes several years of ROUGH wear to require an adjustment to the shock cord. If you never store the handle at the lower attachment and row properly, you won't run into an issue anytime soon after your purchase. The only possible serious difference comes from people ranking pieces online (because the difference one 2k race makes is negligible). And that difference is one that cannot be rectified because even with your 'perfect' world in play, there are still differences between everyone's attempt.

Instead of spouting some very uninformed and annoying garbage, make a god damn suggestion as to how to better return the chain to the cage. You had no problem marketing your handle here, even though it does not really serve a purpose.

[Slidewinder]

Carl Watts and Bloomp,

Other options are not practical.

Instead of spouting some uninformed and annoying garbage, make an (obscenity) suggestion as to better return the handle to the cage.

We are not attacking you here.

The elastic cord chain return system which Concept 2 has always used, has four problems which a weight driven return system would solve. As follows:

1) It would never require adjustment

2) It would never require replacement

3) It would maintain an absolutely constant return force regardless of usage

4) It would not be affected by handle storage position

I apologize bloomp. I know that hearing this is very upsetting for you and your fellow C2 groupies.

[NavigationHazard]

Actually, gravitational acceleration is NOT constant from place to place. Something of the same mass will weigh more in Helsinki than it does in Mexico City, other things equal.

See http://en.wikipedia.org/wiki/Gravity_of ... _the_world

There also are local gravitational anomalies to consider.....

[c2jonw]

Yes, the bungee has served us well over the last 30 years and we have made improvements to it's performance characteristics. As I already stated (and seem to have been misquoted on) we found negligable differences in effort required between ergs with tight vs loose bungees and if anyone has done tests that indicate otherwise I'd certainly be interested.
But the question of handle return means is an interesting one. Recoil springs as found on most lawnmowers have been used but are relatively expensive and not typically designed for millions of cycles of use. A suspended weight has some merit though the issue of inertia and direction change makes implementation somewhat complicated.
I remember a couple of machines that showed some innovation around return force.
One of them used a sort of rack and pinion setup, with a geared bar (I think) attached directly to the handle and engaging a clutched sprocket on the flywheel axle. Pull the handle towards you and the bar drives the flywheel; push the handle away and the sprocket freewheels in the opposite direction of the flywheel rotation. No return spring or weight required. Big drawback: the rod sticking out in front of the machine at the catch- required a lot of floor space.
The other one used a very long handle. The chain attached at the middle of the handle and drove the flywheel much as the C2. But instead of attaching to a bungee the chain went below the seated person, under them and then back up to some pulleys where the chain attached to a spreader bar with ropes attached that would then attach to the ends of the very long handle. So the mechanism was a closed loop, with the person seated between the two ropes coming off the ends of the handle.
If anyone has seen photos of either of these machines (probably from the late 1980s) I'd like to see them.....C2JonW

[Citroen]

Yes, the bungee has served us well over the last 30 years and we have made improvements to it's performance characteristics.

So after 30 years of "if it ain't broke, don't fix it" do you think there would be any reason to change?

There's far worse maintenance problems than slack cords to worry about. With the number of hotel machines I've used which are full dust I'm tempted to carry a screwdriver so I can fix them. That's much more of a problem than slack cords and I'm only looking to get 125 drag to be comfortable rowing. There's also been one or two that hadn't seen a drop of oil since they left Morrisville.

The gym I use is extremely good at doing maintenance so we never have cruddy chains or dust and carp in the flywheels.

[hjs]

I know that hearing this is very upsetting for you and your fellow C2 groupies.

Strong argument

[JRBJR]

Wow. The topic that just would not die. Is C2's latest generation bungee cord the best solution to handle retraction without introducing perhaps minimal additional pull pressure? Perhaps not, but I think many (certainly not all) would agree you get better quality design engineering, beta, product distribution, and no-hassle post-sales support from C2 than just about any other company, foreign or domestic, that I can think of.

Wishing not to appear to be a "C2 groupie," I'll admit I've disagreed with some of their product strategies. The Dyno was a blunder. They didn't enter the dynamic erg market until rather late in the game, after RowPerfect and Oartec had introduced their own versions. Until recently, those of us who liked our static C2 ergs but wanted a dynamic option had to rely on room-filling slide pairs. I still don't know how good the C2 dynamic erg is and am looking forward to the chance to try it out before I decide.

But it's always best to keep things in proper perspective, to keep the big picture in mind. C2 sells good products at competitive prices. Their products are easy to purchase, well-documented, and very well-serviced. If you don't like their products, then take your business elsewhere. No need to waste your time hanging around their message board taking pot shots at the company and its customers while debating the small details ad infinitem. Instead, go out and convince the manufacturer of that wonderful rowing erg that meets all your requirements to set up and maintain their own online message board.

[Bob S.]

The gym I use is extremely good at doing maintenance so we never have cruddy chains or dust and carp in the flywheels.

I love typos like that. It makes it sound like someone was testing the "ergs don't float" theory.

Bob S.

[Slidewinder]

Gravitational acceleration not constant from place to place

Thankyou. You are correct. This is something I missed. To eliminate any unfair advantage caused by planetary gravitational differences, maybe with a weight-driven chain return system a "gravitational factor" would have to be included with "drag factor" to compensate for those nanograms of difference between locations.

inertia and direction change makes implementation (of a weight-driven chain return system) somewhat complicated

I recognized these issues when I introduced the idea, and they would have to be addressed. The obvious merits of such a system (see yesterday's posting) warrant further investigation. A gravity-driven chain return system shouldn't be preemptively dismissed on the assumption that the solution to these problems would be complex.

We found negligible differences in effort required between ergs with tight vs loose bungees...

This was through a heart rate comparison which you acknowledged was an inconclusive test. If the test were repeated using an elastic cord with say, a fifty pound stretch force for the "tight" cord, and elastic cord with seven pounds of stretch force for the "loose" cord, I think it is safe to predict that heart rate differences would definitely be noticed. Less differences in tension would result in less differences in heart rate, until, at the tension differences used in the C2 test, heart rate is no longer a reliable measure for comparison. So, until someone conducts tests with reliable and quantifiable results, we must draw our conclusions from basic physics: More effort (ie: a higher tensioned cord) will result in slower times. Two pounds of extra pull force per stroke means several hundred pounds of extra pulling effort over a 2K distance. It is not convincing to assert that this is inconsequential and will not affect times.