chippyhawkeye wrote:
Hi Tom, I think the answer you received was an inadvertent mixing of a few numbers I have been throwing around at the show. Our flywheel actually weights in at around 6kgs with a rotational inertia of the system of around 0.32 kg*m^2. Based on your energy analysis that would put it at an equivalent bike/rider of about 24kg. We also have a 6 pole electromagnet brake that can deliver 8Nm of torque. We can add in brake torque dynamically to make up for the delta between real bike/rider weight and flywheel Inertia. This allows us to provide a feel that is about as close as you can get to going outside and riding without requiring a really massive flywheel.
Chip, thanks for the reply! An equivalent bike/rider mass of 24kg is still pretty good...better than the tiny flywheels on some fluid trainers (which I've calculated to be ~5kg), but short of the Revolution and the Velodyne. Let's call it a "mid inertia" trainer :-)
That said, I can see how being able to dynamically "add" brake torque would help to simulate an acceleration inertia, but that's not going to help at steady-state, or when pedal force is slightly reduced (such as within a pedal stroke).
IMHO, the main difference between "low inertia" (typical small flywheel trainers, including the Computrainer) and "high inertia" trainers (such as the LeMond, Velodyne, etc.) is that the pedal feel better mimics what a rider feels out on the road within the pedal stroke and is more specific to the training demands.
Maybe you guys just need to spin that flywheel faster? ;-) After all, you can get the higher inertia by either adding mass (or I) or increasing the rotation rate. Since the KE is proportional to V^2, you'd only have to increase the rotational velocity by 1.4x to basically make it the same as the Revolution. More "bang for the buck", inertially speaking, increasing the rotation rate than increasing the mass.
Looks like a cool product. It appears you've thought about the "portability" aspect as well. I can't wait to get a closer look.
http://bikeblather.blogspot.com/