Rotor RPM Increase With Applied Load

[georgi UK]

=] This is great news Martin the tinker!!

So you went from a +60 to -50 using 0 overdrive, so you need to be around half the default and then decide which side to tweak on test 2, test 3 should nail it!

You can type any value you wish for this setting....

[A VIKING]

If it's truly linear, that's what should happen, and as you deducted from the RPM spread, it looks to be that way.


Also while I have you as an audience...
While I was running my "Tail/Collective Mix" to "0" I got to wondering why we need that adjustment with the tail gyro in heading hold.
Shouldn't the gyro be able to compensate for high torque events when it sees the tail start to yaw like its reaction to any other outside disturbance?

With mine set to "0" I had a little counter clockwise yaw of the fuselage but not much.
Would tail gyro gain have an effect in controlling this yaw created from torque?
Are we compensating for poor tail gain adjustment with the Tail/Collective Mix adjustment?

Just a curiosity, any info on the interaction between these adjustments would be appreciated.

[georgi UK]

=] you make some good points, as usual Martin! Firstly a tail rotor has a poor efficiency rating to the point where it rotates into the rotor wash, as an attempt to gain a bit back.

Back in the day we used a Revo Mix in the Tx to add / subtract tail pitch with collective as the gyro was in its infancy, but improving towards the standards we have today.

SK use a similar mix to this in the firmware, and because its generic we need Coll Mix adjustment to suit our individual setups. Which gives good results.

Heading Hold is not without its limitations, high performing machines like yours see huge changes in torque, in an ever changing environment. The SK gov adds to this as more torque is being generated at stick extremes, it also anticipates fast collective action, which is where your thread began...

There are many additional factors also at play here, drag is going up by the square, but we have the tech to dial out unwanted results.

The tail gyro gain is better measured from a blow-out, usually a 90 deg kick, or worse. Collective kicks are dealt with using Coll Mix.

Treat the overdrive as actual RPMS, 40 rpm overshoot is usually considered as pretty damm good, I think you can get it to zero!!!

Oh, and there is a direct relationship between gov gain and tail gain....

[Smoggie]

Opps.. sory i was just duplicating what's been said.. theoretically 50 would appear to be the sweet spot.

[A VIKING]

Thanks for clearing my mind Georgi!
Can't wait for the weather to clear to do more tuning.

Could get as much as 30 inches of snow here, bought a nice big new snow blower.
Wife thinks I bought it for clearing the driveway and sidewalks...actually its for clearing the Velos pad...mums the word.

Thanks for chiming in Grumpy!
And you are probably correct the sweet spot should be around 40-50 or there about.

[georgi UK]

=] would have thought it works the other way?! Listen love, I have another velos on the way to clear the snow......

[A VIKING]

Originally Posted by georgi UK

=] would have thought it works the other way?! Listen love, I have another velos on the way to clear the snow......

She won't fall for that one, she has seen it fly and knows one is all it would take.

What I really want to do is take the Velos out and set it in several inches of pristine snow, spool it up to IU2 and do a max collective vertical takeoff.
That would be epic!
...but worried about how expensive it may be.

[A VIKING]

Originally Posted by Grumpy_Old_Man

Opps.. sory i was just duplicating what's been said.. theoretically 50 would appear to be the sweet spot.

Georgi and Grumpy Old Man you both win the cigar!

I did end up with "50" as my Overdrive number in the SK720BE for my Velos 880. Both motors now keep the rotor RPM "nailed" through high blade angles and amp draw.
As you said, theoretically given my overshoot, 50 would appear to be the sweet spot and indeed it was.
We need to thank Skookum for keeping things logical.

It's pretty cool the SK will allow you to match power requirements to the load (highest blade angle) you normally fly at to keep the rotor RPM stabile.
For those who fly smack or sport there is an Overdrive setting for you that maintains a high accuracy of rotor RPM, you don't end up chasing it or having to deal with timing issues...what you ask for you get, nothing more, nothing less.

So for my Velos I can now fly pulling high amp draws and when looking at the logs after the flight, if I display only the RPM graph line, it looks like I was in a hover the whole flight...that is awesome.
For me a steady RPM smoothens out my flight, and I need all the help I can get.

[Smoggie]

Good that the practice matched the theory.. always nice when that happens!

[georgi UK]

=] great work Martin! I know you would have lived with a bit of an improvement, but you have nailed it to the bullseye!

[omerco]

Not the theory I was told of

And it didn't work for me. I will have to check it again!

Glad it's solved!

[A VIKING]

Originally Posted by omerco

Not the theory I was told of

And it didn't work for me. I will have to check it again!

Glad it's solved!

Omer...
What motor response did you get from making the Overdrive adjustment?

[Luvmyhelis]

Gotta ask, Martin, the 50 od setting should also eliminate most if not all your spool up overshoot? Got my own Gob 800 dialed down to 80 od and am taking it out to play later today to get it fully dialed. New esc in place.

[omerco]

Well I'm back home and while setting up my X7 back to live I had the opportunity to test the collective mix theory. Here are the 2 tests one with collective mix 30 (the one I use) and another with collective mix 0:

coll mix 30:



coll mix 0:

[A VIKING]

Lets move this discussion over to the thread "Effects of Governor Settings on the CC ESC" to continue.
Thanks!