Originally Posted by razorblade
Below is the tach I bought. It works out pretty good. I took the main blades off and tail blades off. Applied a .5 inch of piece of reflective tape (included) to the top of one blade grip. Then raised the throttle to max and measured the rpm by pointing the red laser emitting from the tachometer at the tape for about 4 seconds. I took several measurements. This is considered the no load reading. Well its actually not a "no load" reading since there is some minimal load exhibited by the main gear and tail belt mechanics. But it works well enough.
From what I have read, a more accurate reading can be taken by using an optical tachometer (more expensive) but than that involves having a buddy take the reading while you hover the heli at around 5 feet off the ground.
Couldn't you just do a strap down with the motor running at zero pitch and 100% throttle? Either way the optical tachs i've been looking at won't do 5 bladed. I was hoping i could use this one with a single piece of tape on 1 blade tip or something while doing the strap down thing.