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Old Aug 07, 2011, 09:58 AM
ExPat
Aero Andy's Avatar
Spain, Murcia, Mazarrón
Joined Apr 2010
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OK guys, the maiden went well, up to a point. The good news is it flies, and I've plenty of power, the bad news is, it wants to turn left all the time until I give it WOT, then it straightens up. So, it's just as I described earlier, the right hand motor is starting up first, and through the throttle curve it's increasing in RPM slightly ahead of the left motor. When WOT is reached the the left motor catches up and the RPM's are identical, so it's this start-up lag which is the issue.

I have four spare 10g motors and three 6A plush esc's, and in an effort to get any two motors to start at the same time, I've tried combinations of all kinds. The esc settings are all identical, but still I'm having no luck.

Regards
Andy
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Old Aug 07, 2011, 11:00 AM
Reap the wild wind
headlessagain's Avatar
Bristol,UK
Joined Feb 2007
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Looks like your out of options, time to go for differential control as used in the "The Twins"
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Old Aug 07, 2011, 11:14 AM
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Aero Andy's Avatar
Spain, Murcia, Mazarrón
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Quote:
Originally Posted by headlessagain View Post
Looks like your out of options, time to go for differential control as used in the "The Twins"
Head
Yeah, looks like the only option, unless I want to fly in circles all day....
Andy
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Old Aug 07, 2011, 08:46 PM
Jack
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United States, FL, Hudson
Joined Feb 2010
389 Posts
Howdy Andy:

Seems like if your going to mess with multi-motored planes that a tachometer is a must.

In the old days when I was doing Nitro models I had a C-119 with a pair of OS Max .15's. Bought them both on the same day and broke them in the same way at the same time. It was real easy to get them to run and idle identical. But with electric's it seems to be a different game.

I'm waiting on a tachometer now from Tower hobbies to insure that my motors are turning the same RPM.

Can't wait to see your video.

Jack
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Old Aug 08, 2011, 04:08 AM
WMD
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Bradford, UK
Joined Jan 2010
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Quote:
Originally Posted by Aero Andy View Post
I have four spare 10g motors and three 6A plush esc's, and in an effort to get any two motors to start at the same time, I've tried combinations of all kinds. The esc settings are all identical, but still I'm having no luck.
Hi Andy,

I dunno. I've only ever built one twin, so far, and this is it. Maybe I just got lucky, but I had no issues with power offset/balance, I just installed 2 x CF 2812 motors, 2 escs, and it worked first time.

My motors do not start exactly together, but that is just a momentary thing, I just ignore that and set off. In the air, all is good. I think I wrote earlier that at one point when throttling back I managed to stop one motor and not the other by mistake, then throttled back up and found myself flying on one engine for a few seconds. But flight was still smooth, still controlled.

I don't think the start time difference of the motors matters, because you can just push past that to get them both going. What matters I think is that they have a (broadly) similar response together up through the throttle range. Surely switching motors around if you have - 4 spares - would at some point fix it? Mind you throttle diff control would be a cool thing to do too.

Steve
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Old Aug 08, 2011, 11:45 AM
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Aero Andy's Avatar
Spain, Murcia, Mazarrón
Joined Apr 2010
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Steve

These motors are driving me crazy, but I'm not giving in...
I'm a stubborn bugger and I'm determined to get it right, this plane will fly properly, even if it drives me into an asylum.

A challenge is a challenge, bring it on...
Andy
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Old Aug 09, 2011, 08:11 AM
NKK for short...
nkkromhof's Avatar
United States, IN, Mitchell
Joined Oct 2010
216 Posts
Silly question, you have calibrated the throttle range on both ESC's, right?
Did a quick scan of the last couple of pages and didn't see it mentioned...

It may be necessary to do them both separately, unplug one, calibrate; unplug and plug the other one in and repeat.


Quote:
Originally Posted by Aero Andy View Post
OK guys, the maiden went well, up to a point. The good news is it flies, and I've plenty of power, the bad news is, it wants to turn left all the time until I give it WOT, then it straightens up. So, it's just as I described earlier, the right hand motor is starting up first, and through the throttle curve it's increasing in RPM slightly ahead of the left motor. When WOT is reached the the left motor catches up and the RPM's are identical, so it's this start-up lag which is the issue.

I have four spare 10g motors and three 6A plush esc's, and in an effort to get any two motors to start at the same time, I've tried combinations of all kinds. The esc settings are all identical, but still I'm having no luck.

Regards
Andy
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Old Aug 09, 2011, 09:34 AM
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Spain, Murcia, Mazarrón
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Quote:
Originally Posted by nkkromhof View Post
Silly question, you have calibrated the throttle range on both ESC's, right?
Did a quick scan of the last couple of pages and didn't see it mentioned...

It may be necessary to do them both separately, unplug one, calibrate; unplug and plug the other one in and repeat.
nkkromhof

Well what can I say my friend, except THANK YOU. You were spot on with the idea to calibrate the throttle range on esc's individually, it took me only a minute to do, and now both motors are starting at the same time, and running at the same RPM.
Many thanks again, I really appreciate your help.
Andy
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Old Aug 09, 2011, 09:52 AM
Jack
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United States, FL, Hudson
Joined Feb 2010
389 Posts
Yea - Me too. Thanks nkkromhof.

That may also help my twin motored F&L. I had used to different size props for the maiden flight and had trouble. After correctly that I still noticed that the motors start at a split second different. I don't have a tachometer yet but they do seem to pull the same now. But the calibrate the ESC's both separately is a smart idea.

Jack

PS: I love Indiana.
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Old Aug 09, 2011, 10:03 AM
NKK for short...
nkkromhof's Avatar
United States, IN, Mitchell
Joined Oct 2010
216 Posts
Glad I could help

It's nice to be right every once in a while!

Edit: I have no idea why it makes a difference to do them individually, but it's the same for tricopters and quadcopters, you have to do them individually there too.
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Last edited by nkkromhof; Aug 09, 2011 at 10:06 AM. Reason: Afterthought
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Old Aug 09, 2011, 02:56 PM
Reap the wild wind
headlessagain's Avatar
Bristol,UK
Joined Feb 2007
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Quote:
Originally Posted by nkkromhof View Post
Glad I could help

It's nice to be right every once in a while!

Edit: I have no idea why it makes a difference to do them individually, but it's the same for tricopters and quadcopters, you have to do them individually there too.
I guess I got lucky with my ME-262 tractor twin but your advice will be remembered for my next build. Thanks a lot
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Old Aug 10, 2011, 12:05 AM
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Aero Andy's Avatar
Spain, Murcia, Mazarrón
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Head

Isn't it amazing, I spent hour after hour swapping motors and esc's, trying to programme mix the throttles on my tx, and then "nkkromhof" come up with a simple fix. I love this site, if you don't know something, just ask, someone else will, and can help you out.

How's sunny Bristol
Andy
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Old Aug 10, 2011, 01:36 AM
Reap the wild wind
headlessagain's Avatar
Bristol,UK
Joined Feb 2007
4,157 Posts
Hi Andy
Up early again I see Bristol weather, cloudy bright with light winds. Looks like I might fit in a quickie over the park. My Freeair Fokker D V11 needs a work out.
http://www.flyingtoys.com/reviews/QEFI0909.pdf In fact it's exactly the same plane as featured in the article. The reviewer, John Stennard, is a member of my club and he sells off unwanted review planes from time to time. How about a Phase3 F-16 for £25?
Well my brother has been building and flying RC models of all types for years and it was the first time he had heard of nkkromhof's tip. I must have just been lucky with my tractor ME-262.
I'm subscribing to 86 threads. Some because I might learn something new and others because I'm interested in the build and I always try to offers advice where sought. This might just be sign posting to other threads or from my own experiences.
My build of Lee's F&L is a survivor, having been built in August 2008. I still subscribe to that thread and post when appropriate.
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Old Aug 10, 2011, 06:12 AM
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Spain, Murcia, Mazarrón
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Hi Head

I didn't know you were friends with John from Q&EFI, I've been a subscriber of that magazine for years. John writes a lot of interesting stuff, and all you fellow club members are really lucky to have him selling off unwanted planes so cheap...now I'm really jealous.

Happy flying mate
Andy
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Old Aug 12, 2011, 09:46 AM
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Aero Andy's Avatar
Spain, Murcia, Mazarrón
Joined Apr 2010
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Hi guys, just wanted to let you know that I flew my Jackal this morning, and now my motors are spinning at the same RPM (thanks again nkkromhof), it flies great, in fact it flies amazing..

Thanks Steve for the design, I've added LG and posted some finished pictures below, I'll shoot a video next time I get chance to fly. Also, I thought I'd do something a little different with the paint scheme, I didn't have anything in civilian livery, so decided on British Airways colours.

Regards
Andy
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