Concept2 Forum

A few years ago, I purchased a Model E with a PM4 from a friend. He was the original owner. Date is 2262011. Firmware is up to date. Chain is oiled. Does not show any rust. No obvious broken gears or anything like that. Pull is smooth. I typically have the drag factor at around 130. It has 3.3 million meters. Flywheel is clean.

On the rowers at the gyms I visit in town, I can row much faster with less effort. Some of the rowers in town have more than 10 million meters. For example, after doing a weight workout in town, I can complete my workout with a 7:45 2,000 meter row. I can only row a 7:50 at home on my Model E. Even when fresh.

Or when fresh and in town, I can row 15 times 200 meters with a one minute rest in an average of a 1:50 pace. At home on my Model E, I can only average around 1:54. And the drive does not feel like 130. It feels much higher.

Only difference I can see is that the gyms in town are at 3,200 to 3,300 feet in elevation. At home, I am close to 4,000 feet. Can 800 feet make that much of a difference?

Any other ideas?

Sounds like a Drag Factor issue to me. Do you check the Gym DF before each row and ensure its the same 130 as at home? Alternative might be to try a lower DF at home. Lower it until the feel is the same as the gym ones and then see what pace that allows you to complete your sessions at.

Oh and 800' will make some difference I'm sure, but not as much as you describe.

Thanks for replying. Yes, I check the drag factor before using in town and at home.

Your comment is exactly was I was going to try next. Lower the drag factor at home to see if that made a difference.

Bungee cord?


I’ll get my coat

Tony Cook wrote: ↑

August 8th, 2023, 2:28 pm

Bungee cord?

Unlikely, as it is only a few Newtons in a 400+ Newton stroke (for 2:25/500m, if you go faster, you easily hit 600 to 800 N). One could easily check though: a luggage scale will do.

C2 somewhere mentioned chain stiffness and bearing stiffness. Another unmeasured component is friction of the seat.

JaapvanE wrote: ↑

August 8th, 2023, 2:41 pm

Tony Cook wrote: ↑

August 8th, 2023, 2:28 pm

Bungee cord?

Unlikely, as it is only a few Newtons in a 400+ Newton stroke (for 2:25/500m, if you go faster, you easily hit 600 to 800 N). One could easily check though: a luggage scale will do.

C2 somewhere mentioned chain stiffness and bearing stiffness. Another unmeasured component is friction of the seat.

Translation into neophyte, please.

I doubt 800' in altitude will make much difference. If it does, typically (i.e. for standard atmosphere) at higher altitude the air is a bit thinner, so everything else being the same for the same lever position you'll get a lower drag factor higher up. Other factors such as a cooling fan installed such that it blows on the erg fan will also affect the lever-to-DF relationship.

I wouldn't be surprised if the gym ergs have much lower DF than your home erg (for the same lever position), especially if yours is well maintained and the gym machines aren't (and therefore dusty).

Good Luck

OhBeWan wrote: ↑

August 8th, 2023, 3:04 pm

Translation into neophyte, please.

100 Newton (N) = Force needed to lift 10kg (22 lbs) off the ground.

On the flywheel, at your speeds, I estimate there is around 400N to 500N average force throughout the drive, and 600N to 750N peak force in the drive on the handle (i.e. when I reach your speeds).

This is without considering that your legs push (and accelerate) a grown man from 0 to 2.1 meters/second in about 0.6 seconds, which is an acceleration of 3.5 m/s2 (that is what I need to do at DF135). Assuming you weigh 80 kg, the force your legs produce to do that is around 280N. So roughly, you push 750N on average throughout the drive, with peaks of a 1000N (= force needed to lift 100kg or 220 lbs off the ground).

The bungee is made to retract the chain, nothing more. If I recall correctly, it pulls with 50N normally. Weaking it might bring that down to 30N or so before retracting the chaing gets problematic. A 20N difference on a 1000N activity isn't that big.

Thinking of the altitude difference: 800ft could make a difference in oxygen absorption. There is a reason many athletes train at higher altitudes and race at sea level. I don't know if that would explain the difference though: I'm Dutch, so everything around us is at sea level....

JaapvanE wrote: ↑

August 8th, 2023, 2:41 pm

Tony Cook wrote: ↑

August 8th, 2023, 2:28 pm

Bungee cord?

Unlikely, as it is only a few Newtons in a 400+ Newton stroke (for 2:25/500m, if you go faster, you easily hit 600 to 800 N). One could easily check though: a luggage scale will do.

C2 somewhere mentioned chain stiffness and bearing stiffness. Another unmeasured component is friction of the seat.

It was a reference to a thread from a few months ago - that ran and ran. My peculiar sense of humour.

You also need to remember that the bungee stores energy and returns it to you to assist in the recovery.

Its likely to be in the order of 80% efficiency and couple that with some pretty inefficient muscles for the recovery, some CrossFit gyms over here actually fitted a stronger cord than the standard Concept 2 one. That would be mainly because of high stroke rates and probably poor technique.

And the drive does not feel like 130. It feels much higher.

If different machines feel different, it's because they are, whatever the drag reading. So don't trust the reading.

What's needed is a fast pull; so keep drag low. After all, who wants slow pull and a short recovery?

No expert, but Google search showed that generally the drop in blood oxygenation is insignificant for most below 2000m (6500ft), when the oxygen in the air is around 81% of the sea level partial pressure. Although the partial pressure of oxygen in the air would reduce from 91% to 89% of that at sea level, less oxygen is required to fully oxygenate the blood than is available at sea level. The Oxygen in the lungs is at a lower partial pressure than in the air (100% RH, increased CO2 and mixing with expired air that has had some oxygen extracted already), not sure how the reduction in the oxygen in the lungs changes at high exertion (I seem to remember a suggestion that the fastest ergers cannot fully oxygenate their blood even at sea level during an all out 2k). So there might be some effect of the altitude.

jamesg wrote: ↑

August 9th, 2023, 3:34 am

If different machines feel different, it's because they are, whatever the drag reading. So don't trust the reading.

Another variable: human perception of what's "hard" and what isn't can be affected by the situation.

Whether one is rowing alone vs with a bunch of people around who can see the PM, or say, a solo bike ride vs a group ride, it's common to totally subconsciously perform differently. In the long run what your body is doing eventually catches up with you, but for shorter efforts the difference can be substantial.

I appreciate your comments. You are thinking but you are throwing out odd ball options. No one is watching me at either place. No bungee cords? No seat friction. No fans installed that point at the flywheel.

Could the drag factor be messed up? In other words, it says 130 but it is really 180. Possible but if I pull it really hard, it should be showing a speed in the 1:30's per 500 pace, not the slow pace I get.

How would I check/fix chain or bearing stiffness?

I still don't understand the conversation about Newtons. I understand physics but not how that helps.

OhBeWan wrote: ↑

August 9th, 2023, 8:16 pm

I still don't understand the conversation about Newtons. I understand physics but not how that helps.

The bungee cord (as a potential way to "leak" power) comment was primarily an inside joke - there have been drawn-out discussions here about the bungee, mostly because like seat friction, it's something the PM can't measure. The comments about Newtons were intended to show that it's unlikely the bungee would be the cause of your problem. (which is what C2 assumes when they program the PM)

For normal users like us who don't have something like a calibrated load bridge in an erg handle or haven't installed our own flywheel position measuring instrumentation on the erg (for example) there's no foolproof scientific way of quantifying the difference between Erg #1 and Erg #2 in terms of force input at the handle vs what the PM tells you it thinks is happening.

Other than just living with the difference in RPE (relative perceived effort) you could play around with checking the DF then doing some flywheel spin-down time tests from various steady-state power levels, or find a third erg as the tie-breaker. There are a few other options to figure out what's going on, and if you're so inclined it might be interesting.

If you really think there's a huge difference between the ergs I'd use an HRM to tell me what my body was doing and a damper lever position that I thought was "the right one that gave me the feel I like" and go from there. Either way, you can be sure that you're going to get a good workout.

Good Luck