Does anyone have any accurate data on what it takes to drive the CycleOps Fluid2 trainer? I have not yet come up with the funds for a power meter, but want to get a feel for what wattage I’m pushing while on the trainer. So far, I’ve found two formulas. The problem is that they vary by a significant degree:
y = 0.0022X3 + 0.3317X2 - 4.2434X + 41.855 where X= speed in Km/hr
and
y = 0.74715*X + 0.0466912X3 where X =speed in MPH
Formula 1 was pulled from a website that shows graphs of various 2002 model trainers. (Can’t remember where it is offhand)
Formula 2 is from Kurt Kinetic’s power computer manual (don’t own the computer)
At 20mph on the trainer, there’s a variance of 66 watts (322 vs 388). At 38 MPH, the variance goes up to ~1000 watts. That’s a big margin of difference. (And yes, I do get the trainer up to 38 mph for 30 second power intervals.)
I threw your formulas into a spreadsheet, they do indeed look very different (below). In my own experience, the website figure is slightly high and the Kurt figure is very high. I’ve used both a 2002 and a 2005 Fluid2 extensively, and hold about 22mph for half an hour or so, figuring I’m putting out not more than 350W. Of course there will be some variance between models, but my two behaved similarly.
Kurt says it takes 9W to go 5mph (which I’m not buying). Your website says 30W. The website’s curve looks most accurate to me.
The formula is going to vary remarkably with tire type and pressure, and perhaps even across trainers. The only way you even stand a chance at doing this is to calibrate your own trainer with a known tire and pressure using someone else’s power meter.
“y = 0.0022X3 + 0.3317X2 - 4.2434X + 41.855 where X= speed in Km/hr”
So at 0 kph, you’re putting out 41.855 watts?
Doesn’t that refer to the power required to overcome the static resistance? i.e. the power to do 0.01mph. It needs to be a heck of a lot more than 0W, but 41W does seem a little high. Also there may be phenomenon going on that can’t easily be expressed in equations as simple as these, so it may be that the equations only really apply at real riding speeds.
The formula is going to vary remarkably with tire type and pressure, and perhaps even across trainers. The only way you even stand a chance at doing this is to calibrate your own trainer with a known tire and pressure using someone else’s power meter.
I think that’s very true… and add in the amount that you tighten the knob in the back.
I don’t have a power meter, but I can tell that the effort to speed ratio can vary quite a bit from one ride to another. I haven’t tried to quantify it - my trainer stuff is never anything more than base training, and I don’t quantify my training all that much anyway. But I think it’s going to be hard for the OP to measure power w/out somethign designed to do it.
Alright, I get it. I need to not bother to try to figure out what power I actually generate until I can invest in a meter. I guess I was just a bit curious and wanted a ball park figure, but there are probably too many variables.
It is obvious from your graphic representation that your data is not converted to the proper units of measurement. Any fool will see that your unit of speed, miles/hour, is not useful. More properly leagues/month would be acccurate when we describe this data as it applies to you. Maybe inches/week, but to assume that you are capable of covering anything like a mile in a time period as brief as an hour is crazy, therefore the use of mph is unwieldy
