Model B Drag Factor

[old] PaulS · Post by **[old] PaulS** » October 6th, 2005, 5:42 pm

Since for some reason I could not reply to another thread that was in dire need of this information, we get a whole new thread. The Model B Erg generally has a 13 and 15 tooth sprocket to select from, unless there has been a retrofit of a 14 tooth sprocket. Drag Factors from the C and D (14 tooth sprocket) will necessarily not be directly comparable to either of the "stock Model B" configurations. A model B with all vents closed and using the larger sprocket would certainly result in an "effective" DF of less than 140. For the 15 tooth sprocket take the PM's DF and divide by 1.23 For the 13 tooth sprocket take the PM's DF and divide by 0.80 That said, the flywheel will be slowing down at the same rate as the C or D, but the Drive will have a considerably different feel due to the different "gearing". Cheers!

[old] John Rupp · Post by **[old] John Rupp** » October 6th, 2005, 7:49 pm

Usually posts started by C2's development group who have that funny flag thing cannot be replied to by the rest of us.

[old] John Rupp · Post by **[old] John Rupp** » October 6th, 2005, 7:52 pm

As Paul said, you need to do a converation of the model B drag factor reading to convert it to the same resistance as a model C or D. If you are using the 13 tooth sprockets, your 59 reading would be the equivalent resistance to 74 (59 / .80) on a model C or D. The resistance is determined by comparing the cubes of the number of teeth on the sprokets. 13 x 13 x 13 = 2197 14 x 14 x 14 = 2744 15 x 15 x 15 = 3375 3375 / 2744 = 1.23 . . . conversion from 15 to 14 teeth 2197 / 2744 = 0.80 . . . conversion from 13 to 14 teeth

[old] FrankJ · Post by **[old] FrankJ** » October 6th, 2005, 7:54 pm

<table border='0' align='center' width='95%' cellpadding='3' cellspacing='1'><tr><td><div class='genmed'>QUOTE(PaulS @ Oct 6 2005, 09:42 PM)</div></td></tr><tr><td class='quote'>Since for some reason I could not reply to another thread that was in dire need of this information, we get a whole new thread. </td></tr></table> Paul, Those forums down there are restricted to members of the US Indoor Rowing Development Squad. They don't want them contaminated by knowledgeable people like you. Frank

[old] PaulS · Post by **[old] PaulS** » October 6th, 2005, 7:58 pm

<table border='0' align='center' width='95%' cellpadding='3' cellspacing='1'><tr><td><div class='genmed'>QUOTE(FrankJ @ Oct 6 2005, 04:54 PM)</div></td></tr><tr><td class='quote'><table border='0' align='center' width='95%' cellpadding='3' cellspacing='1'><tr><td><div class='genmed'>QUOTE(PaulS @ Oct 6 2005, 09:42 PM)</div></td></tr><tr><td class='quote'>Since for some reason I could not reply to another thread that was in dire need of this information, we get a whole new thread. </td></tr></table> Paul, Those forums down there are restricted to members of the US Indoor Rowing Development Squad. They don't want them contaminated by knowledgeable people like you. Frank </td></tr></table> I suppose that's understandable....

[old] John Rupp · Post by **[old] John Rupp** » October 6th, 2005, 8:08 pm

You only need to cover the fan side of the monitor. You can do this with anything that blocks at least some of the air flow. I first used black roofing paper, after cutting it in semi circles and attached it with plastic ties to the fan side of the erg. Then I later did the same thing with layers of rubber from a truck tire innertube. You can also cover the perimeter of the erg, which helps to further reduce the noise from the fan. I had also covered that with the black roofing paper, which is easy to use and works very well. The erg fan perimeter is now covered with 3 layers of rubber from a truck tire innertube. If you are really curious about the drag factor and want it to be the same as the C or D, you could likewise replace the sprockets with a 14 tooth cog. Or just continue to use the conversions above, as they are accurate.

[old] rspenger · Post by **[old] rspenger** » October 6th, 2005, 8:32 pm

<table border='0' align='center' width='95%' cellpadding='3' cellspacing='1'><tr><td><div class='genmed'>QUOTE(PaulS @ Oct 6 2005, 02:42 PM)</div></td></tr><tr><td class='quote'>Since for some reason I could not reply to another thread that was in dire need of this information, we get a whole new thread. The Model B Erg generally has a 13 and 15 tooth sprocket to select from, unless there has been a retrofit of a 14 tooth sprocket. Drag Factors from the C and D (14 tooth sprocket) will necessarily not be directly comparable to either of the "stock Model B" configurations. A model B with all vents closed and using the larger sprocket would certainly result in an "effective" DF of less than 140. For the 15 tooth sprocket take the PM's DF and divide by 1.23 For the 13 tooth sprocket take the PM's DF and divide by 0.80 That said, the flywheel will be slowing down at the same rate as the C or D, but the Drive will have a considerably different feel due to the different "gearing". Cheers! </td></tr></table> Paul, I am not sure what you mean by "a model B with all vents closed." The same cover disk does all the vents together. They will always all have the same angle of opening ranging from completely closed through any arbitrary angle to completely open. Mine has two sprockets, so I assume that they are the 13/15 combination (it is awkward to try to see in there to check) and I have always used the larger sprocket. The drag factor numbers that I quoted, i.e 162 (closed) and 210 (open), were the values supplied by the monitor. I am not sure what you mean by "effective" DF. If it is less than 140, what do the monitor values mean? I know that when I try out a C or a D, usually with a setting of 5, the pull feels much lighter than it does on my B. I used to use the B with the vents about half open, but started the summer training program with them closed to make it easier to work at some of the higher stroke rates that the program called for. I am curious about this because I would like to account for the large differences in my own best performance at home (8:50.9) and at the Beach Sprints (8:19.7) and the CRASH-B (8:18.1). Some of that is most likely do to the altitude difference, since I live at 4000 ft., but the CRASH-B qualification allowance in my bracket is only 19 seconds and Denver is a third again as high as Big Pine. I am sure that I was helped at LB by some great coaching by a friend during the trial, but I didn't have that at Boston. The machines are quaranteed to all give the same results, so I can only assume that there are physiological factors that make up the difference. By that I mean that I might be more efficient with a lighter load and a higher stroke. According to my notes, I did the piece at home at 30 spm for 2 minutes and then settled down to 20 spm for the remaining 6:51. At L.B., I remember that it was in the low 20s (about 24?) and when one of the LBRA members needled me about that at Boston, I went for a higher rate and probably held at about 27 or 28. If you have further comments, I would be pleased to read them. regards, geezer Bob P.S. to P.S. What does "angry" have to do with it? Did my message anger you? If so, you have me puzzled. I wasn't trying to be controversial.

[old] John Rupp · Post by **[old] John Rupp** » October 6th, 2005, 9:34 pm

Bob, Why are you being so controversial. The large (closest to the fan) cog has 15 teeth. The other one has 13 teeth. Since you are using the large one, divide your readings by 1.23 to get the equivalent for a C or D. Thus 59 / 1.23 = 48. Yes indeed that is quite low for a drag factor. I usually use a range of 65 to 100 and mine are lower than most.

[old] John Rupp · Post by **[old] John Rupp** » October 6th, 2005, 9:37 pm

When's the last time you did a 2k time trial at your home? You could probably do much faster than 8:50, since you have done 20-30 minutes at that pace.

[old] rspenger · Post by **[old] rspenger** » October 6th, 2005, 10:06 pm

<table border='0' align='center' width='95%' cellpadding='3' cellspacing='1'><tr><td><div class='genmed'>QUOTE(John Rupp @ Oct 6 2005, 06:34 PM)</div></td></tr><tr><td class='quote'>Bob, Since you are using the large one, divide your readings by 1.23 to get the equivalent for a C or D. Thus 59 / 1.23 = 48. Yes indeed that is quite low for a drag factor. I usually use a range of 65 to 100 and mine are lower than most. </td></tr></table> The 59 value was only from an experiment in which I boxed the erg just to see how low it would go. So far all my work has been done with an open erg and, in the last two months, a closed set of vents. As I stated, the lowest drag factor for the unboxed erg is 162, presumably equivalent to 132 on a C or D. if the 1.23 factor is valid. I don't know what slider setting that would correspond to. The few times I have a C or D, I have set the slider in the middle, i.e. at 5. It felt lighter than the B, but at the time I was using a more or less mid vent opening on the B. Interpolating midway between the open and closed vent values, 162 and 210 (186), would give 151. Since that is above the recommended 100 to 140 range, the numbers seem to fit. No way would I ever want to try to use a drag factor of 59. I could never get up to a stroke rate high enough to get anything out of it. Bob S. Row Hearty

[old] rspenger · Post by **[old] rspenger** » October 6th, 2005, 10:21 pm

<table border='0' align='center' width='95%' cellpadding='3' cellspacing='1'><tr><td><div class='genmed'>QUOTE(John Rupp @ Oct 6 2005, 06:37 PM)</div></td></tr><tr><td class='quote'>When's the last time you did a 2k time trial at your home? You could probably do much faster than 8:50, since you have done 20-30 minutes at that pace. </td></tr></table> My last 2k at home was in early January, about 3 weeks before the Beach Sprints. I am waiting now for the end of October trials, but the new training program calls for a 3k, 2k, 1k sequence on Saturdays, so I may find out in a couple of days. Of course a 2k only a few minutes after a 3k will not be particularly definitive, but it might give me some idea of which is gaining the upper hand - training or aging. The aging has been whacking away at me steadily and this is the first time that I have ever tried any training, so it will be interesting to see how it works out. Bob S.

[old] PaulS · Post by **[old] PaulS** » October 6th, 2005, 10:55 pm

<table border='0' align='center' width='95%' cellpadding='3' cellspacing='1'><tr><td><div class='genmed'>QUOTE(rspenger @ Oct 6 2005, 05:32 PM)</div></td></tr><tr><td class='quote'> Paul, I am not sure what you mean by "a model B with all vents closed." I am curious about this because I would like to account for the large differences in my own best performance at home (8:50.9) and at the Beach Sprints (8:19.7) and the CRASH-B (8:18.1). Some of that is most likely do to the altitude difference, since I live at 4000 ft., but the CRASH-B qualification allowance in my bracket is only 19 seconds and Denver is a third again as high as Big Pine. I am sure that I was helped at LB by some great coaching by a friend during the trial, but I didn't have that at Boston. The machines are quaranteed to all give the same results, so I can only assume that there are physiological factors that make up the difference. By that I mean that I might be more efficient with a lighter load and a higher stroke. According to my notes, I did the piece at home at 30 spm for 2 minutes and then settled down to 20 spm for the remaining 6:51. At L.B., I remember that it was in the low 20s (about 24?) and when one of the LBRA members needled me about that at Boston, I went for a higher rate and probably held at about 27 or 28. If you have further comments, I would be pleased to read them. regards, geezer Bob P.S. to P.S. What does "angry" have to do with it? Did my message anger you? If so, you have me puzzled. I wasn't trying to be controversial. </td></tr></table> Not angry with you GB, just that it was inconvenient to not be able to reply in the most appropriate place for a reply. I should have said "vents all the way closed", better? If you look closely there are actually shiny and dull "wedges" on the vent covers that make for incremental adjustments from what I would call "0" (closed), "1" (one wedge open), to 4 (completely open). Couple that with the "L" (Large) and "S" sprockets and the lightest setting would be "L0" (Large w/closed vents) and the heaviest "S4" (small w/full open vents). easy aye? The 0.8 and 1.23 adjustment factors are about as good an estimate that you are going to get, not quite perfect, but a whole lot better than just taking the DF from the PM3. "Good enough for gov't work." one might say. If you were normally training with a PM"1" on your B, you are on the side of the adjustment scale where the PM2 and PM3 are slightly advantageous for you. 1:55 is the "break even" point, i.e. at the power to get a PM1 2:05, the PM3 will be about a 2:04. The advantage fades to 0 as you approach 1:55. Dropping to a SR=20 is very low for a 2k, and it forces you to take much harder strokes to maintain a given pace than increasing the rate a bit. Keeping the rate up was almost certainly the reason for the better time, keeping the workload more even and efficient. C2 may still sell an accessory called the "Speed ring" which covers a bit more on teh vent side of the B cage, worth it if you can get one.

[old] jjpisano · Post by **[old] jjpisano** » October 7th, 2005, 6:18 am

I have a Model B and a PM2. Ihave one of Paul Smith's fan covers on it. Normally the lowest my DF reads is 170 or so; but with the fan cover situated properly I can get the df much lower. Right now I have the vents all closed with the fan cover on and my chain on the 15 tooth sprocket. I've been training at a df of 115. This is basically equivalent to a 93 df (115/1.23) on a C or D? How come I never knew this? Has this ever been discussed on the forum before? Jim Pisano

[old] John Rupp · Post by **[old] John Rupp** » October 7th, 2005, 12:45 pm

There were quite a few postings on the old forum about this. Here is one from early this year: <a href='http://concept2.ipbhost.com/index.php?s ... rag+factor' target='_blank'>http://concept2.ipbhost.com/index.php?s ... +factor</a>

[old] cdykstra · Post by **[old] cdykstra** » December 3rd, 2005, 3:53 pm

All: Sorry to "drag" this one out again, but I have to be certain I get my information straight. On my Model B, with a PM3 and no other modifications (no speed ring, no fan cover, stock sprocket, etc.) with the vents all closed my df is around 170, which, on the 13 tooth gear, is comparable to a df of 212.5 on a Model C or D. Am I figuring that right? Yow. Like others, I have occasionally used newer models. They seem uncomfortably "easy" to pull, although I seem to post similar times. I also seem to have the "catch" problems others have been posting about elsewhere when using the newer models. I guess the real questions I have involve whether I am limiting my potential, developing bad habits, or making myself more prone to injury by rowing the Model B as is with what is apparently an extremely high df. FYI - I did check the old posts but didn't find this information. Please advise. Charles Dykstra

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