How Do Fluid Trainers Work?

[noonievut]

In terms of resistance...say when compared to rollers with no resistance?

For example if I'm trying to follow along a spinnervals DVD and I shift to a hard gear for an interval, how is resistance created?

I'm just looking to maintain fitness over the winter months, no serious training required.

 

[RickF]

Fluid trainers work by spinning a fan in oil. As the fan spins faster, resistance increases exponentially. Each brand has slightly different power curves due to differences in the viscosity of the oil, the size and shape of the fan blades, and the mass of the flywheel, but they all work on the same principal.

I have plotted resistance versus speed for some of the major fluid trainers based on information provided on the Kurt Kinetic site (http://www.kurtkinetic.com/calibration_chart.php)

 

[noonievut]

Another somewhat related question: when following along a spinerval DVD do you need a cycling computer (for speed/distance), or is HRM fine? I generally know what cadence I'm at. Reason I ask is that I don't want to move the cycling computer to the rear wheel.

 

[RickF]

If you know your cadence and gear ratios, then you really do not need a computer, but most of us find it easier to keep track of what we are doing by having a rear wheel computer. I use the Kurt Kinetic Power Computer because it is a rear wheel computer and when I am using the trainer, it will display watts as well as speed and distance. I could do without the computer, but I like having it to measure my progress.

 

[lennyk]

I just started using a kurt kinetic and spinervals also,
the items of effort are basically the gearing which is fixed and your output ie cadence
I find speed irrelevant and cadence is the most accurate way to track effort.

Once you can get an idea of what gearing you are spinning your expected cadence you don't really need any other measurement.

 

[noonievut]

Fluid trainers work by spinning a fan in oil. As the fan spins faster, resistance increases exponentially. Each brand has slightly different power curves due to differences in the viscosity of the oil, the size and shape of the fan blades, and the mass of the flywheel, but they all work on the same principal.

I have plotted resistance versus speed for some of the major fluid trainers based on information provided on the Kurt Kinetic site (http://www.kurtkinetic.com/calibration_chart.php)

Thanks for the info. Do you know how long it takes for the resistance to kick in (I've heard something about needing 10 minutes to warm up).

I ask only because after setting up the trainer I put the bike on and pedalled for all of 1 minute so this may not be realistic.

 

[RickF]

Thanks for the info. Do you know how long it takes for the resistance to kick in (I've heard something about needing 10 minutes to warm up).

I ask only because after setting up the trainer I put the bike on and pedalled for all of 1 minute so this may not be realistic.

The resistance starts as soon as the wheel begins to rotate. It probably takes about 10 minutes for the amount of resistance at a given speed to become constant, since the oil in the unit gets hot, and viscosity decreases as temperature increases. This would mean that when the oil is cold, the resistance is greater than it would be when the oil is warm. The change, though, is small, and you probably will not nitice it.