I can't speak for John, obviously, but I did some of my own experimenting with a cover on my old model B. With the original PM(1), there was no way of knowing the drag factor and I had no idea that there was such a thing. Then I acquired and installed a PM3 and gradually found out what it was all about. With the damper of the Model B fully closed, I was getting a draq factor of over 150 and that was at high altitude, so the DF would be even higher with the higher density of air at lower elevations. Since I was using a 15 cog gear, instead of the 14 cog gears of the later models, it would be like having a DF of about 140+ on a C or D. I also had the option of using a 13 cog gear, but that would make it feel like a much higher DF. I found a convenient cardboard box that neatly fit over the wheel, effectively covering it except for a narrow opening on the back end (i.e. the end where the monitor, support, and chain are). This reduced the drag factor by a full hundred points. I was getting readings in the low 50s. I never did work out with the covered wheel. I had been using it uncovered, damper set in the middle, on the 15 cog gear, mostly at sea level for about ten years. I was used to it and saw no need to change except to close the damper down. A few months later I bought a Model D and decided to get used to using it at a more conventional DF, under 140. Currently, I leave the damper at 6, which gives me a DF of 115-125 depending on local temperature and pressure.TabbRows wrote:John,
When you cover the fan cage on your Model B, did that affect the drag factor settings?
Yes, definitely. Most of the reduction is due to the speed ring on the side though, then the perimeter covering just reduces it a bit more. My model B has a drag factor range of 65 to 200, with a model C 14 tooth cog. I changed to a 14 tooth cog soon after getting a pm2+.TabbRows wrote:John,
When you cover the fan cage on your Model B, did that affect the drag factor settings?
Well that certianly explains why I was having problems maintaining a 1:52 AN effort on a 5x2' workout on Monday at home (lack of time for more) but was swinging over 300 watts average (1:44/500!?) at the club last night on the same workout but up 2 beats in rating. Both drags were 115. By your formula, I was pulling 144 on the B but 92 on the C.If you're using the small 13 tooth cogwheel on the model B and are getting, for example, a drag factor of 120, this is the equivalent resistance of a 150 df on a model C or D.
There is no need to do any conversion from the C reading of 115. The more significant difference is the +2 in rating. (about an 8 second swing at the paces involved).TabbRows wrote:Well that certianly explains why I was having problems maintaining a 1:52 AN effort on a 5x2' workout on Monday at home (lack of time for more) but was swinging over 300 watts average (1:44/500!?) at the club last night on the same workout but up 2 beats in rating. Both drags were 115. By your formula, I was pulling 144 on the B but 92 on the C.If you're using the small 13 tooth cogwheel on the model B and are getting, for example, a drag factor of 120, this is the equivalent resistance of a 150 df on a model C or D.
Right, 115 with the B on 13 is equivalent resistance to 144 on a C.TabbRows wrote:Well that certianly explains why I was having problems maintaining a 1:52 AN effort on a 5x2' workout on Monday at home (lack of time for more) but was swinging over 300 watts average (1:44/500!?) at the club last night on the same workout but up 2 beats in rating. Both drags were 115.
