Learning to read logs with sk data viewer

[Colin Broughton]

So I purchased the Skookum data viewer as I'm really interested in learning how to read and benefit from the logs.

I've checked today's flight logs on 2 different heli's just out of curiosity what I would find different between the models. One is a goblin 380 and one a goblin 500

Im running both of them with the Skookum governor and here's where my question comes into play. I see that in my first log posted here is the goblin 500, which the governor is showing a sporadic line very close to the same as the throttle



And here is a photo of the goblin 380 where the governor is well above the throttle



Ok so now here's where I'd like a little lesson on what this means and if it's an indication one is set up wrong etc. I feel that the last log I posted is an indication I'm geared wrong and the governor is running higher that the first log, and the first log I posted is running an inproper gain resulting in the fluctuation.

Or these logs look incredible and I'm posting nonsense haha. Either way just looking for input on reading the sk logs.

[RontaryUS]

What matters most and foremost to tune the gov using the log is to check the RPM and see how stable it is (i.e display the RPM, gov output and collective on the same screen). The gov output can help fine tuning and see how the gov may overcompensate or undercompensate in relation to the RPM to then fine tune the gain. Having the collective input will help putting the RPM in relation to the load on the head.

[Colin Broughton]

Thanks rontaryUS here's a more recent log from today's flights on the same helis but displaying the rpm

Goblin 380



Goblin 500

[RontaryUS]

It seems you can still play with the gov gain on the 500 to decrease the variation in rpm. You could indeed verify the gearing on the 380 with Mr Mel calculator (I am sure you know how to figure the best gearing but feel free to ask if you need assistance) although it holds the headspeed pretty good; except toward the end (spikes and maxout gov output). If you display the collective on the graph it will help you see the load you put on the head and check the rpm variation associated to it and decide if acceptable or not accordingly. You will have to fine tune trying different gov gain values (and review of the gearing for the 380). Hard to do through a post but hope you got the concept from those few guidelines which I understand was the goal of your post!

By the way, you get quite a bus voltage drop from the first posted log on the 380. Bench test with load (pitch pump while adding pressure on the swash for example) to make sure you don't get brown out. You may want to add a capacitor to help your BEC.

[omerco]

What is much more noticeable in your log is that the first one is mechanically better tuned (you could use one tooth bigger pinion (or pulley no?) on this one, depending on how satisfied you are from the performance). this can be seen in the amount of times you hit 100% throttle.

The second (380?) has a much too big pinion for your headspeed - your governor output is between 60-80% throttle. this stresses your batteries, ESC, heats the motor and shortens your flight times. above all it makes the governor gain harder to tune - similar to using a too long servo arm for the tail - it has too low resolution.

Fixing the gearing will eventually help get the governor gain tuned better and getting your RPM more stable.

[A VIKING]

And this is the power of the Skookum Logs!
I think everyone looking for more knowledge should take a good look at these logs, as they are great examples, then bump them against their own logs to see how or if they compare, then read about what is recognized in the log, understand the advice given and corrections needed.
Great work guy's.

[mrultralite]

umm, there really needs to be a tutorial somewhere on this subject.

[Luvmyhelis]

Originally Posted by mrultralite

umm, there really needs to be a tutorial somewhere on this subject.

We have tried and discussed it for years now. I after all this time am still learning myself. Brilliant diagnostic work always has me watching.

[Colin Broughton]

Originally Posted by RontaryUS

If you display the collective on the graph it will help you see the load you put on the head and check the rpm variation associated to it and decide if acceptable or not accordingly. You will have to fine tune trying different gov gain values (and review of the gearing for the 380). Hard to do through a post but hope you got the concept from those few guidelines which I understand was the goal of your post!

Now the same logs but added the collective

380



500

[Colin Broughton]

Wow guys thanks for all the responses and inputs, I'm really glad I brought this topic up. It's very interesting and I want to learn as much as I can. If it's available to use why not, right

[Xrayted]

Originally Posted by Badhelipilot

Wow guys thanks for all the responses and inputs, I'm really glad I brought this topic up. It's very interesting and I want to learn as much as I can. If it's available to use why not, right

Yes, its a great tool and constant learning process. I have a double RPM head spike on my Goblin that bounces as I do certain cyclic moves.

After some channel plotting, its easy to see that it only occurs when I add elevator. What is even more odd, is that it only occurs with back elevator. Nothing much I can do about it, and it doesn't cause me any issues, buts its cool to be able to drill down to exactly what situation causes the spike.

It also make it clear that there isn't any problem with some out of balance part, as the issue only occurs with elevator and not all of the time like an out of balance issue would create.

Notice in the image that only back elevator causes the vibe spikes. Forward elevator circled in red does not. Its very cool to be able to see these little details within the logs, and it takes time to fully understand exactly what value and detail this data is able to provide for us.

In my case I'm not wasting my time trying to balance something away on my blades that is not out of balance in the first place. Just looking at the vibe score alone is only a small portion of what the graph can tell me. Its drilling down to the exact thing that causes those vibes to spike up that matters, as I can determine if I have real control over it or not, or if its a failing part.

[Luvmyhelis]

Originally Posted by Xrayted

Yes, its a great tool and constant learning process. I have a double RPM head spike on my Goblin that bounces as I do certain cyclic moves.

After some channel plotting, its easy to see that it only occurs when I add elevator. What is even more odd, is that it only occurs with back elevator. Nothing much I can do about it, and it doesn't cause me any issues, buts its cool to be able to drill down to exactly what situation causes the spike.

It also make it clear that there isn't any problem with some out of balance part, as the issue only occurs with elevator and not all of the time like an out of balance issue would create.

Notice in the image that only back elevator causes the vibe spikes. Forward elevator circled in red does not. Its very cool to be able to see these little details within the logs, and it takes time to fully understand exactly what value and detail this data is able to provide for us.

In my case I'm not wasting my time trying to balance something away on my blades that is not out of balance in the first place. Just looking at the vibe score alone is only a small portion of what the graph can tell me. Its drilling down to the exact thing that causes those vibes to spike up that matters, as I can determine if I have real control over it or not, or if its a failing part.

Great post. Also there are vibes in our set up work on our helis that hit a point of no return. Where you can chase them down to nothing at great cost and effort. Or live with them and really never have them effect anything other than just knowing they are present. I have gone from having almost totally vibe free helis, other than the description Xrayted described above that appear in just about every Sab I have ever seen's logs. To, the hey, I can live with this attitude. And just go fly and have fun as long as the vibes aren't overly invasive.

Depends on what kind of individual you are and where you are at in the process. I used to love to tinker. Now, I would rather go fly and spend less time on my own helis trying to hit that magic zero mark.

[Colin Broughton]

Originally Posted by omerco

The second (380?) has a much too big pinion for your headspeed - your governor output is between 60-80% throttle. this stresses your batteries, ESC, heats the motor and shortens your flight times. above all it makes the governor gain harder to tune - similar to using a too long servo arm for the tail - it has too low resolution.

Fixing the gearing will eventually help get the governor gain tuned better and getting your RPM more stable.

I may be using Mr Mel's calculator incorrectly then

120 main gear
21 pinion
880kv motor

So when I calculate the stock gearing I read this chart as a 3000ish is optimal range
This is where I have the gov set to and now I'm confused that by the sounds of it I'm missing a step of sort.

[omerco]

According to your log you are at 2400...

[Colin Broughton]

Originally Posted by omerco

The second (380?) has a much too big pinion for your headspeed - your governor output is between 60-80% throttle. this stresses your batteries, ESC, heats the motor and shortens your flight times. above all it makes the governor gain harder to tune - similar to using a too long servo arm for the tail - it has too low resolution.

Fixing the gearing will eventually help get the governor gain tuned better and getting your RPM more stable.

Originally Posted by Badhelipilot

I may be using Mr Mel's calculator incorrectly then

120 main gear
21 pinion
880kv motor

So when I calculate the stock gearing I read this chart as a 3000ish is optimal range
This is where I have the gov set to and now I'm confused that by the sounds of it I'm missing a step of sort.

Originally Posted by omerco

According to your log you are at 2400...

Ok just to clear up a couple things for anyone following along to the logs and comment, me and omerco have spoken via pm and sorted out a couple things and I'll clarify it now

We got a little mixed up with which log was for which model so to speak. It's the logs for the 500 is where he's pointed out I'm geared wrong in this post stating the 2400hs not the 380

So here's the log again



And here's Mr Mel saying I incorrectly have my gearing set



I'm ordering the correct pinion now