Drag Factor on Model A

[Nomath]

Let me guess. The MOI of 28 inch bicycle wheel, without tire, is typically 0.06 - 0.08 kg m². The lower value is for a 28 inch wheel with Al-rims of a lightweight road bike ; the higher value for 29 inch MTB (same rim diameter). It doesn't matter whether it's a front wheel or rear wheel : the extra mass from the freewheel hub and the cassette are very near to the axis, so contribute little.

The Model-A wheel does not look lightweight (36 spokes). In addition it has 9 blades attached near the rim. No idea of their weight. My guess is that the MOI is 0.08-0.10 kg m². Roughly same as for Model D.

[JaapvanE]

Dave Vernooy did a similar calcuation, with a bit more populated flywheel, and some more spokes: https://dvernooy.github.io/projects/ergware/

He ends up at 0.161 kgm^2, so I stand corrected, the iniertia is indeed higher than the BCD's...

[c2jonw]

The mass of the bicycle wheel (old school 27" steel rim) is a small part of the equation. The majority of the inertia comes from a 5/8" steel hoop attached to the rim which weighs in at about 9.4 pounds. It's very efficient in terms of creating the maximum MOI for the least amount of weight.

[Ombrax]

Walter, have we managed to convince you to either 1) Forget about DF, or 2) Get a new RowErg with a PM5 ? ; )

[Nomath]

The mass of the bicycle wheel (old school 27" steel rim) is a small part of the equation. The majority of the inertia comes from a 5/8" steel hoop attached to the rim which weighs in at about 9.4 pounds. It's very efficient in terms of creating the maximum MOI for the least amount of weight.

9.4 pounds at the rim of a 27" wheel (ISO 584 mm) adds a lot : 4.3 * 0.29² = 0.37 kg m².

[walterpump]

Walter, have we managed to convince you to either 1) Forget about DF, or 2) Get a new RowErg with a PM5 ? ; )

The answer Ombrax is yes. Enough of this fixating on the DF which as you guys have pointed out is meaningless for comparing effort & performance with others. So just row, right!
Now, a new RowErg with PM5 will have to wait; and since I am 81, I may be dead before I get one in this life. Perhaps in my next life, if there is such a time - ha, ha.
However, I just have to say for everyone to know, the Model A is a cool machine, not to be looked down on, and provides basically the same rowing experience as the newer models. I have rowed on Model C and D also. My Model A is in 'like new' condition with a working PM-1 monitor, and I am having a great time rowing and staying fit. Monday's row - 3012M @ 19spm, 2:98/500m, time 19:27. I am working towards by end of year to do 2K @ 2:30spm. If I achieve that I will be rockin man!!!
Oh one more thing guys & gals, I have a used PM-3 arriving this week, and already have the mounting bracket from Concept 2 so when mounted I will be able to use my Logcard plus be able to post results a little better.
Cheers all.

[JaapvanE]

Now, a new RowErg with PM5 will have to wait; and since I am 81, I may be dead before I get one in this life.
...
My Model A is in 'like new' condition with a working PM-1 monitor, and I am having a great time rowing and staying fit. Monday's row - 3012M @ 19spm, 2:98/500m, time 19:27. I am working towards by end of year to do 2K @ 2:30spm. If I achieve that I will be rockin man!!!

I hope that when I reach that age, I would reach these times. Keep up the good work and above all: enjoy it!