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11-07-2012 02:31 AM  7 years ago
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Blackhawk6

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Wobble wobble...
What causes the heli to wobble front to back (elev)? I could be wrong but I think I noticed this in flight a couple times today.

Is it in the head, 3gx, or...
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11-07-2012 04:51 AM  7 years ago
Gregor99

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A lot of times its caused by the headspeed being too low for the hardness of the dampers. Either move to softer dampers or raise the headspeed. If is DFC head, softer dampers are not an option.
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11-07-2012 09:41 AM  7 years ago
Blackhawk6

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Thanks George! Ill look into that...
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11-07-2012 09:52 AM  7 years ago
wingtip

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what your talking about is what we normally refer to as the porpoise effect... as mentioned it could be dampers, it could also be tightness of your blade grips..but most of the time its just poor rotor head design and its linkage geometry.
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11-07-2012 10:47 AM  7 years ago
Blackhawk6

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Hmmmm well, one heli is a 450 sport with a new DFC head...which is the one I noticed this on. Although, I thought I saw the same effect on my 700 a few flights later.

When you mention "poor rotor head design and head geometry" what do you mean by that? Could something be off in the head?

I'm going to check the tightness of the blades. Now that I think about it, they could be a little tight...
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11-07-2012 12:35 PM  7 years ago
wingtip

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just what it says, poorly designed and/or manufactured parts.. if thats the case with yours..
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11-07-2012 12:38 PM  7 years ago
Blackhawk6

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I see :/ Ill check into the other variables and try to solve the issue...
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11-07-2012 07:14 PM  7 years ago
Gregor99

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Hmmmm well, one heli is a 450 sport with a new DFC head
The DFC head is very stiff, it has to be. That means that it will need a higher headspeed to prevent the bobble. What is your headspeed now?

Greg
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11-07-2012 07:29 PM  7 years ago
Blackhawk6

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That why I was wondering how that could be...I just put that head on there last wk and that when I noticed it. The head speed is at 3400 right now... Can/should I even go higher than that?

I bought a 12t pinion for the 2221-6 scorpion but I thought that would be too high...it has the 11t now.
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11-07-2012 07:49 PM  7 years ago
Gregor99

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3400 seems plenty high enough. Are you sure you are hitting 3400? Are you using a governor?
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11-07-2012 07:53 PM  7 years ago
Blackhawk6

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Yea, gov is enabled...set rpm at 3400 100% flat. This happened yesterday so ill have to check the data today and see what she did.
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11-07-2012 08:17 PM  7 years ago
Gregor99

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If you have a CC, the logging will tell the story. Check the headspeed and the power out %. If the hs is not holding and the power out is pegged, then the gearing is too low (larger pinion needed) or the pack is dying (not holding voltage under load).

Also double check your gearing and Kv settings in the motor setup on the CC. When in doubt an opitical tach will verify the suspected headspeed.
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11-07-2012 08:57 PM  7 years ago
Blackhawk6

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Ok. Yea, it is the CC. Ill pull the log to iChat when I get home and check it out. I'm fairly new to the "logging" so if I have any troubles ill post the screen shot to see whatcha think. I do know that the last flight wasn't the long or hard of a flight tho. I just ran a couple mins to check how the gov was working...

We'll see what t says later.
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11-07-2012 09:27 PM  7 years ago
Gregor99

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I don't recall the logging defaults. But you may need to setup the values to be logged. Also once the log is full it stops logging. Depending on the logging settings the logs may get full after as little as 4 flights. You can clear the log in the field by powering up the ESC at 100%. Once you get the confirmation beeps, power cycle the ESC and start normally .
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11-07-2012 10:22 PM  7 years ago
Blackhawk6

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I have it set to log everything. Being new to that feature, I wanted to use it to its fullest and start to study an learn what the bird is doing at all times... I just got the gov set up the other day and I remember clearing it that day for this purpose.

So, I can see different flights that are logged? For instance, if I flew 4 flights that day I could see them all?

I'm excited to use this and start to learn and know what to look for...
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11-08-2012 12:43 AM  7 years ago
Gregor99

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If you have all data points logged, you may only get a few flights in before the log is full. You can see all flights that are logged and they are seperated by "sessions". Use the "choose session" option from the menu to zoom into a specific flight.

Because they are not timestamped and you don't know when the ESC stopped logging, it can be hard to line up the sessions to specific flight. When I'm troubleshooting an issue I bring a laptop to the field and download the logs every 3 or 4 flights. When the issue occurs in flight, I switch to a higher or lower headspeed briefly. Or use throttle hold. If you are logging the throttle channel in addition to the power out %, this gives you a visual indicator in the log as when the issue occurred.

In your case all you looking for is consistant headspeed until the end of the pack. Not a specific incident. You can probably use the exisitng logs to see what's going on.
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11-08-2012 01:29 PM  7 years ago
Blackhawk6

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I pulled the logs last night and reviewed them for a bit. Man, that is cool. I can see everything the heli did through the flight... I wanted to post it here for you guys to look at but it got a little late so I had to crash for the night. Ill put them up later this evening. Everything looks good through the flight but let's see if you can find anything...

About the wobble, I messed with the head and found that there was a little play in the grips as if the feathering shaft was loose. I took the whole head apart and reassembled it. Could that be the cause of a wobble?

In the log, it showed that the HS was right around 3350 (what I have it set to) and the batts seem to be ok as well...

Ill show ya ltr tonight.
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11-09-2012 01:00 AM  7 years ago
Blackhawk6

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Alright, here's the log from the 450 flight. Let me know what ya think.

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11-09-2012 03:49 AM  7 years ago
Gregor99

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I see two things:

1) It looks like you transitioned into a lower headspeed in near the end of the flight. You also mentioned that's when you say the wobble. Do you remember switching to a lower headspeed?

2) I get 12.5:1 for 150t main gear and 12t pinion. That is different that what you have on the log. That will affect the resulting headspeed the governor targets.
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11-09-2012 11:33 AM  7 years ago
Blackhawk6

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Well, yes, I switched to N mode for a bit and then landed. That's why you see the change. Also, I have the Scorpion 2221-6 motor with a 11t pinion at the moment. That's why the gearing ratio is different. I think I'm going to put the 12t on and try to raise the HS a bit.

I don't recall if the wobble was after I went to N or not. That "could" be the result bc I think my N HS is only 3000.

I rebuilt the head and ill put the 12t on to do a couple flights with that today. Ill keep a close eye on it to see if the wobble is gone.
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