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        Discussion Going to try Set RPM on my Trex 700 again

#1 Raydee Sep 22, 2012 05:34 PM

Going to try Set RPM on my Trex 700 again
 
I didn't have much luck getting it to work good before but I am going to give it another try. Is this setup still the preferred setup for the Trex 700 using the newest 4.02 firmware?
http://www.castlecreations.com/suppo...0mx-530kv.html

#2 RC Man Sep 22, 2012 06:16 PM

I am not speaking for CC but I think that they now recommend a PWM of 12 and High start power.

Governor gain seams to vary from motor to motor so you may want to tune it a little after you get flying. Some are able to run a little higher gain than 12.


I have found that V4.01 and V4.02 governors are definitely better than the older versions.



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#3 Raydee Sep 22, 2012 06:32 PM

Ok what should I change the start power to? I think I left it low last time I tried 4.01 and that may have been the cause of some of the issues I had.

#4 John235 Sep 23, 2012 04:22 AM

I've always had good results with Set RPM mode on micro size helis since the feature was introduced in 2009. I'm running V3.28 now and it as good as ever. Since I crashed the heli with an old version of governor software (about V1.3 or something) I don't want to try beta release firmware anymore.

In the interests of stability and safety I think its important not to go too aggressive on the gain setting. Lower gain is safer. Better to be safe than sorry with a 700 size heli.

#5 RC Man Sep 23, 2012 05:17 AM

Quote:

Originally Posted by Raydee (Post 22807144)
Ok what should I change the start power to? I think I left it low last time I tried 4.01 and that may have been the cause of some of the issues I had.

Start Power controls the motor power used during the first couple of seconds to get the blades turning. Set it at 100 and forget it for most helicopters. If it if trying to turn the helicopter around at first then decrease 10 at a time until smooth.


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#6 Clintstone Sep 25, 2012 05:51 AM

I would Leave the start power at default and adjust up if it is needed. My 700 is default on start power...

If the 700 is stock use 12 kHz PWM and Normal timing.

#7 Raydee Sep 25, 2012 06:23 AM

Quote:

Originally Posted by Clintstone (Post 22828267)
I would Leave the start power at default and adjust up if it is needed. My 700 is default on start power...

If the 700 is stock use 12 kHz PWM and Normal timing.

Ok I will give that a try.

#8 Bernie Wolfard Oct 05, 2012 03:58 PM

Increasing start power usually make a good start up bad. This is not a setting you want to change from its default unless you have a good reason to do so, usually related to a motor so bad it won't start anyway else.

Bernie

#9 Raydee Oct 06, 2012 02:14 PM

Ok I put the start power back to default and will hopefully get to try out the GOV mode tomorrow or Monday.

#10 Clintstone Oct 09, 2012 07:42 AM

Quote:

Originally Posted by Raydee (Post 22929864)
Ok I put the start power back to default and will hopefully get to try out the GOV mode tomorrow or Monday.

I would start the GOV gain around 12....

#11 Raydee Oct 09, 2012 11:55 AM

Yep I have the GOV gain set to 12 to start. I will post a log after I fly it today after work.

#12 Raydee Oct 09, 2012 05:38 PM

1 Attachment(s)
Ok I took the heli out today after work. It looks like 2200rpm is a bit to high so I will knock it down to 2050 and see how it does. I think the gain is to low, I dont know if it is a good way to tell but when I switched at the end of the flight from 2200rpm to 1950 to land the RPM dipped way down and had to come back up to 1950.

#13 Alan Hahn Oct 10, 2012 09:23 AM

Your head rpm is too high.

Look at the PowerOutput parameter. It is near 100% at the start of the flight, and is at 100% after 100s until you switch back to the lower rpm.

That means you are flying at near 100% throttle for the entire flight.

What did the Parameter window say when you chose that set rpm? If it didn't complain big time, then I think you don't have the pole count, gearing, or Kv input correctly into the Castle Link software.

added. Looking at your current parameters, and I see it is in the 30-40A range during most of the flight, only occasionally peaking into 80A range.

I'd say your gearing (or Kv) is a bit on the low side.

#14 Raydee Oct 10, 2012 12:13 PM

Alan I am using the standard Trex 700e motor and gearing. Like I said in the post above I know i need to lower the RPM for the gov to work properly. When I put 2200rpm into the program it did warn me but I wanted to try it anyway and make sure.

Do you think when switching to 1950 and having the head speed drop way off before it picks back up is a indicator that the gain is to low?

#15 Alan Hahn Oct 10, 2012 04:30 PM

Quote:

Originally Posted by Raydee (Post 22963523)
Alan I am using the standard Trex 700e motor and gearing. Like I said in the post above I know i need to lower the RPM for the gov to work properly. When I put 2200rpm into the program it did warn me but I wanted to try it anyway and make sure.

Do you think when switching to 1950 and having the head speed drop way off before it picks back up is a indicator that the gain is to low?

I'm not an expert on the drop-off issue---I just tend to fly at one headspeed for the entire flight, including takeoff and landing.

I have heard of other's problems with the drop-off. I am not positive what exactly causes it, except that when you flip to a lower rpm, the rotor rpm can tend to decouple from the motor rpm--due to the one-way bearing. So the ESC sees that the motor load drops dramatically and lowers the current way down in an attempt to keep the new low motor rpm--with the motor seeing almost no load. At some point the main rotor slows down enough to have the oneway engage, but now the motor current is really low, so the governor has a long way to go to get it up to sustain the head rpm.

Not sure if that is a real explanation of the problem or not. Sounds good to me :D!

I am not sure if goosing up the gain will help this or not, and whether the higher gain may cause other problems.

But like I said, it is easy enough to land at any headspeed, as long as you can lower the pitch appropriately. So I don't experience the problem in the way I fly.


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