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Author Topic: Interesting Problem ...  (Read 1328 times)

Offline Wynn Robins

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Interesting Problem ...
« on: November 06, 2010, 08:48:32 PM »
I bet this is related to the cheap A$$ turnigy motor - but here goes..

Flying the other day I needed more RPM - so plugged in the FM9 programmer and added another couple hundred - (no tach) so flew again...hmm - no more speed than before - same lap time....land - up the RPM again....same thing...weird

Setup is Turngiy 3548-900 - ICE Lite 50 - Hubin FM-9 timer with +/_ 1000 RPM pot - 4s 4000mAh pack

I get home and throw the tach on it as it was at the field - 8465RPM  -RPM,  timer is set to 9760 - not even close......up the RPM on the timerto 10200 - same RPM 8465.... change the timer to a new one - RPM set to 10200 to see what happens - same 8465 RPM...

took the timer and ESC and put it on my T-rex that is running a scorpion  3026 890 - hits target 10200 no problem on the tach - the "pot" needle adjust revs as it should...  so I am wondering if it is the motor that cant keep up - or is there something else I am missing here?

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Offline wwwarbird

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Re: Interesting Problem ...
« Reply #1 on: November 06, 2010, 10:35:04 PM »
 Nitro. ;D
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Offline Howard Rush

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Re: Interesting Problem ...
« Reply #2 on: November 06, 2010, 11:43:21 PM »
Good one, WWW.
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Offline Keith Renecle

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Re: Interesting Problem ...
« Reply #3 on: November 07, 2010, 12:29:21 AM »
Hi Wynn,

I was going to say, add some ether......but ....I'll resist the temptation S?P I reckon that you simply hit the highest rpm that the Turnigy will run at for that particular setup. You could try disabling the governor on the ESC and then wind up the pot on the timer to see where the max rpm is. If you have an R/C system then try that to see what the motor can do.

I've never used any of the CC ESC's, but I know that many of them require you to set the upper and lower throttle range. If you get higher rpm on the R/C system, then maybe the ICE 50 has been set to a higher pulse width than your timer is putting out. For example, if the ICE has been set for a high end throttle of 2.2 ms, and your timer gives you a max of 2.0 then you just not reaching the maximum throttle. Let us know what you find.

Keith R
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Offline Wynn Robins

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Re: Interesting Problem ...
« Reply #4 on: November 07, 2010, 12:31:39 AM »
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Offline Igor Burger

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Re: Interesting Problem ...
« Reply #5 on: November 07, 2010, 01:58:29 AM »
It could be problem of motor, ESC or battery.

- put on small prop 10” or so. If everything works well, then ESC is OK. If not, then ESC does not allow proper RPM and governor needs to be reprogrammed.

If ESC is OK, then the combo is overloaded, so put on original prop and:

- measure voltage of battery while running, it must be somewhere at 14V. If it is low (12V or so), then your problem is battery.

If battery is also OK, then you have problem with your motor or you use too large prop.

But if I read comments on http://www.hobbyking.com/hobbycity/store/uh_viewitem.asp?idproduct=7393 I think I know what is wrong  ;D
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Offline William DeMauro

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Re: Interesting Problem ...
« Reply #6 on: November 07, 2010, 10:47:39 AM »
I am almost sure you are overpropping. I've had similar problems with turnigy motors and large props. Some of them seem to hit a wall in the mid to higher 8000 rpm range. Put a small prop on it (8x6 or  similar) and watch it spin up to your desired RPM. The funny thing is that it seems kind of random sometimes where one motor will do that and another wont. I always bench run first with a small prop so the motor wont load up then try it with the fly prop. There is always a difference!!! I've read over on RC Groups that if you use a prop on the bench that is about 2 sizes smaller than your fly prop you will be pretty close in numbers to your fly prop when it unloads in the air. Like you I NEVER had a problem with my scorpions hitting my desired RPM,so tolerances and heat, better magnets also factor in.
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Offline Wynn Robins

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Re: Interesting Problem ...
« Reply #7 on: November 07, 2010, 12:14:36 PM »
I am going to replace the motor with a scorpion - I am sure it will solve the problem.

I changed all the hardware out and used it on my T-rex and it all works correctly - so it IS the motor.....

bye bye Turnigy!
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Offline Tim Wescott

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Re: Interesting Problem ...
« Reply #8 on: November 07, 2010, 12:33:43 PM »
There used to be a sign above the counter -- at the local junkyard, no less -- "The bitterness of poor quality lingers long after the sweetness of low price has worn off".

(They were a _really high quality_ junkyard -- you have to experience both to understand how this can be so).
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Offline Wynn Robins

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Re: Interesting Problem ...
« Reply #9 on: November 07, 2010, 02:00:28 PM »
Quote from: Tim Wescott on November 07, 2010, 12:33:43 PM
There used to be a sign above the counter -- at the local junkyard, no less -- "The bitterness of poor quality lingers long after the sweetness of low price has worn off".

(They were a _really high quality_ junkyard -- you have to experience both to understand how this can be so).

the motor had its place in me getting into ECL - so it served its purpose rather well
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Offline Crist Rigotti

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Re: Interesting Problem ...
« Reply #10 on: November 07, 2010, 04:59:19 PM »
Is the pole count the same for the 2 different motors you tried?
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Offline William DeMauro

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Re: Interesting Problem ...
« Reply #11 on: November 07, 2010, 05:23:48 PM »
Crist,
 The pole count on the Turnigy and the Scorpion are both 14. I have both of those motors.
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Offline Wynn Robins

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Re: Interesting Problem ...
« Reply #12 on: November 07, 2010, 06:28:02 PM »
yes they are - but one works, the other does not.   I am sure I have had the Turnigy up around 10K before  - but that was before......but this is a different one - maybe it is buggered - anyway - its out the door now - so no big deal

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Offline Dennis Adamisin

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Re: Interesting Problem ...
« Reply #13 on: November 07, 2010, 09:43:38 PM »
If the motor was overpropped you should also be experiencing high current draws and high heat.  If those are not happening then its probable that the motor KV is way off - that fact that it keeps coming back to the SAME RPM suggests that it is hitting the wall becasue of incorrect (low) kv...
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Offline John Cralley

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Re: Interesting Problem ...
« Reply #14 on: November 08, 2010, 06:53:22 PM »
Just a thought. If the KV is way off the motor might work fine in this application by switching to a 5S battery.

John
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