Tachometer

raisingmn · Post by **raisingmn** » March 13th, 2008, 5:06 pm

After spending some time on a model A, I've come to appreciate the analog visual feedback the original bike speedometer provides. During the drive and recovery of each stroke, I can watch the "hull speed" accelerate and decelerate - something completely missing on the PM1 - PM4. For an on-the-water rower, this feedback is much more analogous to the boat than a single 500/m split report per stroke.

I'd like to see some kind of simple bar graph tachometer added to the PM3-4 display that grows with acceleration, leaves a marker at the peak, and then shrinks as the RPMs drop during the finish. The bar wouldn't reach 0 until the fan has actually stopped.

Glen

Nosmo · Post by **Nosmo** » March 13th, 2008, 5:20 pm

You sort of have that just by listening to the sound of the fly wheel.
Interesting idea but don't know if I would every use it--but it does make me nostalgic for the model A.

michaelb · Post by **michaelb** » March 13th, 2008, 5:28 pm

You could try using ergmonitor. In that blizzard of information and charts, I see speed. Not sure if it can give you wheel rotation or speed, but you could ask Paul.

http://ps-sport.net/

tomhz · Post by **tomhz** » March 13th, 2008, 5:52 pm

Yes, Ergmonitor does show flywheel speed if you like. But flywheel speed is not the same as hull speed. Hull speed is highest during recovery and lowest at the catch or a bit later. Flywheel speed is highest during the final stage of the drive and lowest at the catch.
Furthermore, flywheel speed is higher at lower drag, but the hull speed isn't.

I dont think Ergmonitor can show the hull speed.

Tom

johnlvs2run · Post by **johnlvs2run** » March 13th, 2008, 7:21 pm

Good idea, but I'd rather see a line graph than a bar, perhaps similar to the stroke profile is now.

PaulS · Post by **PaulS** » March 13th, 2008, 8:15 pm

tomhz wrote:Yes, Ergmonitor does show flywheel speed if you like. But flywheel speed is not the same as hull speed. Hull speed is highest during recovery and lowest at the catch or a bit later. Flywheel speed is highest during the final stage of the drive and lowest at the catch.
Furthermore, flywheel speed is higher at lower drag, but the hull speed isn't.

I dont think Ergmonitor can show the hull speed.

Tom

ErgMonitor can graph "Virtual Boat" Speed, which would correlate with "System Speed" when in a boat, though it is not sensitive to a rushed recovery which is why there are gross hull speed fluctuations during the recovery in a boat, that we in fact want to minimize for the sake of efficiency.

In a boat, if your hull speed goes considerably higher after the blade has been extracted from the water, you are bleeding off power at a faster rate than all that effort bing put in at the end of your drive when the system speed and hull speed were equal for at least a moment in time. Ideally the hull would not exceed the top system speed, but that is quite difficult to do and requires more patience than most can muster under "race" conditions. We tend to just get too darn excited.