Checking the Tail for Vibes

[Maj. Woody]

Hi Guys.
When checking the tail for vibes I removed my main blades, secured the helicopter and ran her up. Here is where my question lies. What percentage of throttle are you using to check for vibes? I started just off idle and slowly ramped up to about 70%. My concern with 100% throttle was over speeding the motor and tail blades. My thought is that without the load from the main blades the motor and tail blades might spin faster than normal causing a dangerous situation. Is this fear warranted? How fast do you spin yours while checking the tail?
Thanks!

[ahahn]

Originally Posted by Maj. Woody

Hi Guys.
When checking the tail for vibes I removed my main blades, secured the helicopter and ran her up. Here is where my question lies. What percentage of throttle are you using to check for vibes? I started just off idle and slowly ramped up to about 70%. My concern with 100% throttle was over speeding the motor and tail blades. My thought is that without the load from the main blades the motor and tail blades might spin faster than normal causing a dangerous situation. Is this fear warranted? How fast do you spin yours while checking the tail?
Thanks!

As I have noted elsewhere on the 500X forum, your ESC is already reaching WOT at a throttle setting of 70%. So in some sense you are already checking!

"Normally" most motors are happiest when they are spinning (under a load) at ~80% of the unloaded max rpm. That's where they run the most efficiently and make less heat. If you assume that's what your head speed is at WOT, then the rpm without mains is at most ~20% higher. You would hope that's within the engineering design specs.

HOWEVER, I do have a friend who was doing this test with a Hobby King 450 and it threw a tail blade on him. So keep in mind that you really don't know how over designed anything is. In other words, I'd run up to 60% stick setting (remember my 70% comment) and keep my body out of the direct line of fire! In any case, you certainly want to make sure the vibration is minimized in the rpm range where you actually fly, not at some higher rpm you will never reach (especially if there is a still a vibration in the flying rpm range).

As always, some is my opinion (but the 70% is actually true!).