Resistance on new black model D

[cwest87]

I've noticed a serious increase in resistance on the new black model D. Even at the same frag factor there is definitely more resistance than on the blue model D. I experienced this at an indoor regatta, and my team mate who owns a black model D agrees with me. Is there an explanation as to why this is? Has anyone experienced something similar?

[Citroen]

Clean the dust and crud out of the older machine. The air flow through that older machine is probably badly blocked.

Drag factor is a measurement made by the monitor it's not directly related to damper lever position.

[Bob S.]

Clean the dust and crud out of the older machine. The air flow through that older machine is probably badly blocked.

Drag factor is a measurement made by the monitor it's not directly related to damper lever position.

But Dougie, he specifically said that it was at the same drag factor - not the same damper lever position.

Bob S.

[Citroen]

Clean the dust and crud out of the older machine. The air flow through that older machine is probably badly blocked.

Drag factor is a measurement made by the monitor it's not directly related to damper lever position.

But Dougie, he specifically said that it was at the same drag factor - not the same damper lever position.

Bob S.

Then it's all in his head. The machines are identical apart from the paint job.

[Yankeerunner]

Clean the dust and crud out of the older machine. The air flow through that older machine is probably badly blocked.

Drag factor is a measurement made by the monitor it's not directly related to damper lever position.

But Dougie, he specifically said that it was at the same drag factor - not the same damper lever position.

Bob S.

Then it's all in his head. The machines are identical apart from the paint job.

I disagree (knowing full well that I usually am proved wrong when I disagree with Dougie ). I've always felt that the new machines at CRASH-Bs are harder on the drive than my own, and other, older machines at the same drag factor. My best guess is that things like the bungees or whatever are tighter coming out of the factory than after they are broken in. Even though the drag factor as measured by the deceleration of the flywheel is the same, the effort to get the fly wheel spinning seems harder. At least for a weakling like me. Others, Tom Rawls for one, feel that the new machines only feel smoother to him and not harder.

Last week at my own race I had three nearly new machines to use for the racing and Carla Stein (Seat5) independently said the same thing about being harder to drive (she has an old Model C, I have a 9-year-old Model D).

[cootngeezer]

My new model D was very hard to pull the first 5 or six pulls. I though that was caused by the new bungees getting stretched. It too is harder to pull than an old model C that I was using at a gym and the return force is for sure a lot greater on my new model D. I guessed the old model C just needs a tune-up.

[kayakr]

Can someone confirm or deny that the model C and D have identical flywheel weights and moments of inertia?
I use a model C at a gym and D at home.
The gym model seems to have a lighter flywheel but maybe I'm mistaken.

The gym model C does have more broken in bungies and the damper also walks itself to a lighter setting over time.

[Ergmeister]

Can someone confirm or deny that the model C and D have identical flywheel weights and moments of inertia?
I use a model C at a gym and D at home. The gym model seems to have a lighter flywheel but maybe I'm mistaken. The gym model C does have more broken in bungies and the damper also walks itself to a lighter setting over time.

I happened to be rebuilding an older Model C today so I weighed the flywheel at 9.4 lbs. This will likely vary some from C to C as these flywheels are usually balanced by drilling 1/2" holes in the perimeter, so some will have more than others, but that's a starting point. I expect when I pull a D apart it will weigh more but I don't know what that equates to as far as inertial pull differences if anything. But the older C flywheel I just weighed twice on different scales was 9.4 pounds.

Clean the dust and crud out of the older machine. The air flow through that older machine is probably badly blocked. Drag factor is a measurement made by the monitor it's not directly related to damper lever position.

Correct. Worn or stretched bungees and dust are main culprit of this.

Dust in the machine is generally counter-intuitive to most people's thinking; dust makes the machine easier to row, so the dust in the older machine will have a much lower drag factor than a new machine at the same damper setting. I've seen dust plugged rowers that couldn't get the drag factor to 100 with the damper slammed to 10. Drag factor is generally a reliable number irrespective of the damper setting from rower to rower.

If this is truly as stated, perhaps updating firmware, and proper cleaning and maintenance of the rowers showing the differences will level the field for you.

I frequently hear from owners that after I do a full rebuild on their rowers, they lower their damper 50% or more to get the same drag factor as before.

[Bob S.]

Dust in the machine is generally counter-intuitive to most people's thinking; dust makes the machine easier to row, so the dust in the older machine will have a much lower drag factor than a new machine at the same damper setting.

There was one odd exception to that on this forum (or maybe the UK forum?) not long ago. A really clogged up erg was reported as giving very strange results, like having an extremely high drag (and feel), which would suddenly drop to a very low level. It all cleared up on cleaning. It was never completely spelled out, but I am convinced that the dirt build-up was so great that it was actually contacting the wheel creating the very high drag due to friction. A few spins of the wheel would knock some dirt loose and the wheel could turn freely again, with only air left to provide drag - which was very low because of the clogged cage.

Bob S.

[Atorrante]

I have a new black D since November. It roughly had half million meters logged in, so it's breaked, and I find it harder than my 8 y.o. D, and I'm actually slower in it.

[rowbike]

The black model D I bought in December with about 300k on it so far is noticably harder than the two six year old model D's I use at the gym, and I can see significant differences in my times. But my black one has a better, more substantial "feel" when rowing, beyond the fact it is new, if that makes any sense.

[c2jonw]

Can someone confirm or deny that the model C and D have identical flywheel weights and moments of inertia?

The flywheel moment of inertia (which is the important value, not weight) is the same for the models B, C, D, E, Skierg and Dynamic. Differences in feel between various machines at the same drag factor are anecdotal but may be attributal to how well the chain is lubricated, bungee tension and overall smoothness of the machine. Then there's always pre-race jitters.....C2JonW

[Atorrante]

So in a machine with an over tensed bungee one actually can be wasting energy while rowing and be slower? While an under tensed bungee is easy to diagnose, how can be tested the bungee not to be over tensed?

[c2jonw]

So in a machine with an over tensed bungee one actually can be wasting energy while rowing and be slower? While an under tensed bungee is easy to diagnose, how can be tested the bungee not to be over tensed?

As long as the bungee cord is in the normal range of tightness (6-8 pounds at the catch) there's not going to be a significant score difference between machines. Testing has confirmed this, and it is our conclusion that at normal tensions the majority of the energy that you put into the cord to stretch it is returned to you in helping you back up to the catch. Of course at much higher tensions there will be noticeable changes in the feel and in the energy needed. C2JonW

[Atorrante]

Thanks Jon to clear this. For now I will assume my new black D has an extremely tensed bungee not to be ashamed with the otherwise poor performance in the last few months.