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Revolution Models . CarbonXtreme . Midland Helicopters

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e-Electric General Discussion > Strange FDR comparison: 20 tooth replaced with 19 tooth
 
 
Dan A.
Senior Heliman
Location: Rancho Santa Margarita, CA

Can someone explain what may cause the dramatic difference in the low and high peaks of pack amps signal?

With the 20 tooth pinion, amps were more continuously high (~30 A). The peaks fluctuated between 42 and 18 amps. However, the 19 tooth pinion (same 3D flight pattern and same pack) resulted in more consistent continuous amps (~23 A), with fluctuations between 45 and 10 amps (much wider band). Much less bogging with 19 tooth.

Does this indicate something else that I should investigate? Or is this typical results from changing one tooth down on pinion size?

FDR attached for comparison.

08-25-2008 01:44 AM
 
 
Dan A.
Senior Heliman
Location: Rancho Santa Margarita, CA

When I play the 20 tooth data in live mode (Eagle Tree e-logger V3), the amps signal changes at an expected rate, reflecting expected (stick induced) load changes.

However, when I play the 19 tooth data in live mode, the amps signal fluctuates (bounces) much broader and faster than the expected (stick induced) load changes. Is this typical timing for voltage and current sensor output? Maybe a mistuned algorythm? Or is my new pinion backlash too tight?
08-26-2008 01:52 AM
 
 
helimatt
Elite Veteran
Location: Lafayette, IN

I'd expect a problem with sensing the amp draw on the 19T run, unless you do indeed have the mesh (backlash) too tight. I would not expect the characteristics of the amp trace to be much changed.

Never, ever, ever, ever give up.
08-26-2008 03:07 AM
 
 
Dan A.
Senior Heliman
Location: Rancho Santa Margarita, CA

Update:

Disassembled and added a slight amount of backlash to the front and rear pinions. I believe both backlash adjustments are perfect now. However, the amps signal still exhibits erratic bouncing.

I'm starting to think my ESC settings may need an adjustment? Maybe this was caused by a combination of:

  1. Lowering the throttle setpoint into the governing region (instead of maxed, following pak volts).
  2. Excessive governor gain. I have a CC HV85 ESC with governor set to high gain (80).

Maybe I should try a governor gain setting of 75? Does anyone have a less random approach? Or is this amount of amp bouncing considered normal?

08-28-2008 01:40 AM
 
 
fergus
Veteran
Location: Ireland

The pack voltage seems to be following the load shown by the amp draw so I doubt the elogger is wrong. I would try setting up the CC85 again. I would suspect the ESC governor. Its hard to know the exact cause without knowing what your flying style is. Have you tried logging just a few minutes hovering? If the amp draw is still fluctuating like that then you know the ESC is not happy.

EDIT: Just a headsup - Your voltage on the first flight was getting into damage territory for the pack (unless your flying Kong or Airthunder).

Regards

Fergus
08-28-2008 01:54 AM
 
 
Dan A.
Senior Heliman
Location: Rancho Santa Margarita, CA

Fergus,

Yes, damage territory indeed. That was the reason for replacing the 20 tooth with 19 tooth and lowering the throttle setting.

To answer your question, I've recorded hard 3D and hovering. Both traces exhibit significant erratic amp spiking that is much faster than stick demand.

What are the general symptoms of excessive ESC governor gain in terms of the signal behaviors on an FDR trace?
08-28-2008 03:38 AM
 
 
fergus
Veteran
Location: Ireland

Quote 
What are the general symptoms of excessive ESC governor gain in terms of the signal behaviors on an FDR trace?

I'm afraid I can't help with that one. I don't use Castle ESC's so am not very familiar with the governor and programming It does seem to be exhibiting a 'hunting' behaviour if thats the correct term.

Regards

Fergus
08-28-2008 11:31 AM
 
 
Dan A.
Senior Heliman
Location: Rancho Santa Margarita, CA

Update:

I lowered the governor gain setting from 80 to 50. Result: no appreciable difference in amp spiking and headspeed control.

Maybe my motor is starting to short? Is that a plausible failure mode or normal wear symptom? Is the amp spiking consistent with possible motor shorting?

What do you recommend next?
08-31-2008 02:06 AM
 
 
Rob_T
Elite Veteran
Location: Tualatin, OR - USA

I've never seen a motor with an intermittent short (they always seem to fail solidly for me) but it's possible in theory.

Is this a belt driven tail? I've seen something similar when the belt tension is too slack (in my Shogun).


Rob
Eco8, Piccolo Fun, Shogun, HB Elite CP, Trex 450XL CDE, Swift
08-31-2008 07:37 AM
 
 
Dan A.
Senior Heliman
Location: Rancho Santa Margarita, CA

Thanks Rob.

I'm starting to feel better about the FDR trace now.

I believe my belt tension is perfect. Any tighter and the drag would hurt me. Any looser and the belt would slap more than it does, which is only momentarily during hard sideways times.

I just didn't know what "normal" looked like (no experience with FDRs). I'm starting to think my amp trace is normal for hard 3D pumping.
08-31-2008 05:43 PM
 
 
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e-Electric General Discussion > Strange FDR comparison: 20 tooth replaced with 19 tooth
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