Re: Ever do wattage intervals on a gym bike?I've used the Star Trak Pros at the local Y for a couple of years. The wattage readings appear to be very consistent from bike-to-bike, as well as over time. Haven't seen them taken apart, but believe they use a chain-driven alternator and load bank for resistance, which means power is just a matter of measuring the volts/amps.
Can't judge the absolute accuracy of the calibration of course, but as others have said, that really doesn't matter for training as long as the load is stable and repeatable. Don't know if they have any calibration adjustments, or if any periodic calibration checks are possible.
The power I see on the StarTraks does seem to correlate well with estimates from low-speed road climbing. For my weight (200 lbs body and bike), a 10% grade requires ~40 watts per each mph. So, to maintain 6 mph takes ~240 watts output, which is sadly about my max for 10 minutes....whether on the road or on the indoor trainer.
Believe it feels harder indoors on the Startrak due mostly to the lack of cooling air. As you know, the little 1 x 4 cm fan doesn't do a whole lot compared to the breeze on the whole body we generate while pedaling.