HobbyKing.com New Products Flash Sale
Reply
Thread Tools
Old Jan 13, 2015, 02:07 PM
Registered User
Lenny970's Avatar
Greeley, Colorado, USA
Joined Feb 2000
2,947 Posts
Quote:
Originally Posted by rotoraddict View Post
Flying a Swift 16 at a 1620 rotor speed would require about 450 watts when using 520mm blades. I calculated, your current draw on your 6S pack would be relatively low (450/22.2 = 20.27 amps). With only using 80% (2720mah or 2.72 amp hours)of your 3400 mah pack your flight times would safely be 2.720/20.27 =0.134 hours or 60 x .134 = 8 minutes.

You are using throttle curves better suited for nitro/glow helis, NOT good for use with electric helis.

May I suggest the following considering a 5 point curve - Normal 0/100/100/100/100 and Idle up as 100/100/100/100/100. You should see an improvement even at that 1620 head speed.

But using this throttle curve, you would even find a big improvement in flight maneuverability by going to a 10T or 11T pinion. Of course you would sacrifice a lot of flight time also.

I had a short opportunity to fly over the weekend and tried a revised version of the same throttle curve I had been using.
I changed the Normal curve to (-100/50/100), so that I'm at 3/4 throttle at mid stick and a little above that in a hover. The top half of the Normal curve matches my Idle 1 curve.

The headspeed sounded better to me and the Swift was a bit more responsive to pitch inputs.
I just did some hovering and some basic circuits along with a few hard pitch pumps to test the response. I've got 530mm Helimax carbon blades on this one.
According to the data from the Castle controller, it's pulling about 13A and 325W in a hover and maximum power in a hard pitch pump is 35A and 825W.

Recorded headspeed was about 1885 in a hover, a maximum of 1950 (at the top of a pitch pump), and minimum of 1821 (at the start of a pitch pump).

So, if these numbers are accurate I think the headspeed is about right for me.
When I get another chance to fly, I will try to test a (0, 100, 100, 100 100) Normal curve also and see how that goes. It would be nice to have a more constant headspeed.

Thanks,
Lenny
Lenny970 is offline Find More Posts by Lenny970
Reply With Quote
Sign up now
to remove ads between posts
Old Jan 18, 2015, 03:25 PM
Registered User
Joined Apr 2009
170 Posts
Quote:
Originally Posted by Lenny970 View Post
...Recorded headspeed was about 1885 in a hover, a maximum of 1950 (at the top of a pitch pump), and minimum of 1821 (at the start of a pitch pump).

So, if these numbers are accurate I think the headspeed is about right for me.
When I get another chance to fly, I will try to test a (0, 100, 100, 100 100) Normal curve also and see how that goes. It would be nice to have a more constant headspeed.

Thanks,
Lenny
Rotoraddict has explained it all pretty well in post #1991. It explains why you are getting the rotor speed variations. It is simply because of your V shaped throttle curve settings.

Of note is that I am sure that if you used a rotor tach, you would find the Castle readings will consistently be about 10% high. I think that is because they do not take into account the fact that most motors operate at only a 90% efficiency.

I will try to explain your V curve, as simply as possible relating to voltage and KV. It is a bit more complicated then this, but this should make it adequately understandable.

Think of the ESC as a variable voltage regulator. So at the 100% setting it is feeding the full voltage from the battery. If you have a 22.2 volt 6S pack the 910 KV motor will turn at 910 x 22.2 = 20,200 rpm. At 3/4 stick it would be sending out a command for 75% to the ESC, which in turn would send less voltage to the motor so the motor speed would drop. Ditto for the mid stick position at 50% which would ask the ESC to drop the voltage to the motor even lower, which would drop the rotor speed even more.

If you would run a straight line across the top as RA is suggesting, then your ESC would always give a command to the ESC for a constant voltage. This would result in a constant rotor speed. As the pitch changes resulting in the loads increasing and decreasing, the motor will draw whatever AMPS from the battery it would need to maintain that rotor speed.
GyroMan is offline Find More Posts by GyroMan
Last edited by GyroMan; Jan 18, 2015 at 03:31 PM.
Reply With Quote
Old Jan 19, 2015, 01:23 PM
Registered User
Joined Jul 2008
1,695 Posts
Thank you GM, you saved me a lot of typing.

Sorry Lenny970, I was away from any computers over the weekend but GM seems to have covered it all very well.
rotoraddict is offline Find More Posts by rotoraddict
Reply With Quote
Reply


Thread Tools

Similar Threads
Category Thread Thread Starter Forum Replies Last Post
Discussion Gyro for Swift NX knfevg Large Electric Helis 7 Jun 22, 2010 01:21 PM
Discussion Hurricane 550 vs Swift NX 550 WEFlyer Large Electric Helis 22 May 07, 2010 02:25 PM
Discussion Century Swift 16/550/620 Owners Thread RcSuperSales-Net Large Electric Helis 43 Feb 11, 2008 07:42 AM
Discussion Century Swift Power and Setup question thread Fred Bronk Electric Heli Talk 731 Nov 30, 2006 09:25 AM
Century Swift 16 Build Thread dthreatt Electric Heli Talk 52 Dec 21, 2005 04:32 PM