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Old Dec 26, 2012, 04:11 PM
John
Australia, QLD, Brisbane
Joined Aug 2012
542 Posts
Quote:
Originally Posted by Rollmops67 View Post
I think the working of the gyro is programmed in this manner :
- Heli tends to turn to left (counterclockwise seen from above) : gyro increases tail rotor speed to blow against (conteract) the rotation movement.
- Heli tends to turn to the right : gyro decreases tail rotor speed to blow less so the torque from the main rotor will help to keep the heli straight.

This behaviour will remain the same if you turn the tail 180 degrees. (what is basically correct for a main rotor turning inverted).
And so if the heli wants to turn to the left, the gyro will still increase the tail rotor speed, but with the difference that now the increasing thrust from the tail rotor will blow to the left and thus make things worse.

The solution (along with turning the tail assembly 180 degrees) would be to learn the Rx to invert the gyro's manner to work :
- Heli tends to turn to left (counterclockwise seen from above) : gyro decreases tail rotor speed to blow less so the torque from the main rotor will help to keep the heli straight.
- Heli tends to turn to the right : gyro increases tail rotor speed to blow against (conteract) the rotation movement.

But I have no idea how to do that and if it's even possible...

Roland
Probably the easiest way (if you're right, and I think you are) is to mount the main PCB upside down as well - at first thought, that should put EVERYTHING back where it was? Plenty of room in the 45/450 chassis.
It's a pretty easy job to remove the servo - on the old PCBs - and remount it 180deg out too (rewiring, of course).
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Old Dec 26, 2012, 04:43 PM
John
Australia, QLD, Brisbane
Joined Aug 2012
542 Posts
Arrowshooter -

Think the thing that makes the ADH300XL and 18Aplush work is that we're (well, I!) am only ever planning on 2s: the motor is a 3s, so never near redline .

Edit: My Turnigy 1811s just came: onwards to plan B! (actually, plan C - B is the belt)
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Old Dec 26, 2012, 05:26 PM
Brent 黑雁
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Canada, AB, Ponoka
Joined Jan 2012
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Quote:
Originally Posted by OldOz View Post
Arrowshooter -
The AD300XL -
Everything technical I know about the AD300XL is here - http://www.hobbyking.com/hobbyking/s...dProduct=11884

It's a great motor (but does run warm). No shortage at HK yet, either.
I use our 'standard' Turnigy plush 18A ESC with it, no probs yet, doesn't run hot either.

The belt tail -
Have put in a day trying ideas with this. I'm starting to think it's not going to be easy with the MJX Rx. The problem may be due to the different programming for a brushed tail vs a servo - best effort so far is pretty unstable flight in a narrow RPM band.
Still trying, though.
On the other hand, the belt tail worked at once with my 6chan Tx/Rx (and gyro). No s/w mixing, of course. It's tempting!
But I'll battle on with the Turnigy 1811s, when they get here. It would be good to tidy up the original project as specified, and helpful to newcomers too.

Finally, 6am here local. A great flying morning at 5am (a bit of a shock to the system, though!) and again reinforces just how good the F45/450 IS. Again, higher, faster, and into stronger winds than ever before: and 10min flight no problem.
It is however NOT a CP (for better and worse). But sure as hell looks like one lol.
The reason that motor runs warm is it is running out of it's design rpm range. That was the first motor I tried. It would hover for me at about 35% throttle. When it runs too slow, the amperage increase because it is lugging. If You could find a 9 tooth pinion, it would be better, but I could never find one for the 3mm shaft.
Maybe you guys should just try with the align head and set the pitch to whatever you want with a constant pitch throughout the complete throttle range. That will be fixed pitch, only you can adjust to whatever you want.
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Old Dec 26, 2012, 05:46 PM
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United States, CA, Modesto
Joined Aug 2012
828 Posts
Programing Card

Does anyone know if the Turnigy Programming Card can be used on Hobbywing or Hobbymate Speed Controls? I think I remember one or the other but not sure.
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Old Dec 26, 2012, 06:09 PM
John
Australia, QLD, Brisbane
Joined Aug 2012
542 Posts
BThirsk -
You may well be right, but the motor is well within its power range. I remember your comments at the time: which is why I had the motor shelved until the 450 mod. I also would not recommend this motor for a stock MJX F45.

However, the motor runs hot for most users according to the HK comments. And see the last comment (in French!).
Before I fitted it to the 450 frame - and long before even considering posting the mod here - I ran it overnight into a dummy load at the same rpm with no ill effects (65deg C at the end). More to the point, It has now run irl over 40 flights @ 650g AUW minimum, and 950g max also with no ill effects.
From my own POV, the point of this mod was to AVOID using the align head. Despite 700+ flights, innumerable crashes (due to mainly my own stupidity) my total F45 damage bill has been one main drive gear, one blade, and one tail shaft. I don't of course count motors or the tail gears. Not so for anyone learning on a 450CP FB head, however modified.

I believe the MJX head and 45deg flybar will always have a place as a 'fun' flier, and learning tool. It's the best, imo.
The purpose of the 450 mod was to preserve this simplicity and indestructibility, but give some of the 'feel' of the heft and presence of a 450 in the air: and also fill a gap presently occupied solely by the Funcopter.

While not questioning your experience or advice (which has steered few wrong), perhaps you could revisit the concept from this point of view. I have previously stressed this is NOT a CP, nor handles as one: it is, however, a step up in power, wind authority, and - above all fun - from a 'standard' EH200 mod.

And - finally! I've crashed the F45/450 a few times, too. All but once, straighten the flybar and GTG again. It's a good heli.
Let's see if Arrowshooter feels the same!

Regards
John.

Final Edit: Yes, am using a 10t pinion: I wouldn't advise any larger, either.
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Old Dec 26, 2012, 07:49 PM
Brent 黑雁
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Canada, AB, Ponoka
Joined Jan 2012
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Quote:
Originally Posted by OldOz View Post
BThirsk -
You may well be right, but the motor is well within its power range. I remember your comments at the time: which is why I had the motor shelved until the 450 mod. I also would not recommend this motor for a stock MJX F45.

However, the motor runs hot for most users according to the HK comments. And see the last comment (in French!).
Before I fitted it to the 450 frame - and long before even considering posting the mod here - I ran it overnight into a dummy load at the same rpm with no ill effects (65deg C at the end). More to the point, It has now run irl over 40 flights @ 650g AUW minimum, and 950g max also with no ill effects.
From my own POV, the point of this mod was to AVOID using the align head. Despite 700+ flights, innumerable crashes (due to mainly my own stupidity) my total F45 damage bill has been one main drive gear, one blade, and one tail shaft. I don't of course count motors or the tail gears. Not so for anyone learning on a 450CP FB head, however modified.

I believe the MJX head and 45deg flybar will always have a place as a 'fun' flier, and learning tool. It's the best, imo.
The purpose of the 450 mod was to preserve this simplicity and indestructibility, but give some of the 'feel' of the heft and presence of a 450 in the air: and also fill a gap presently occupied solely by the Funcopter.

While not questioning your experience or advice (which has steered few wrong), perhaps you could revisit the concept from this point of view. I have previously stressed this is NOT a CP, nor handles as one: it is, however, a step up in power, wind authority, and - above all fun - from a 'standard' EH200 mod.

And - finally! I've crashed the F45/450 a few times, too. All but once, straighten the flybar and GTG again. It's a good heli.
Let's see if Arrowshooter feels the same!

Regards
John.

Final Edit: Yes, am using a 10t pinion: I wouldn't advise any larger, either.
No, I fully understand.
Many would've call me crazy for stretching the MJX, converting to all brushless, redesigning the flybar system, and changing to a complete different radio system.
I have thought about differ blade system as well. I might just mill a new blade mount from aluminum with an eight degree mount so I can use a real blade.
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Old Dec 26, 2012, 08:01 PM
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OldOz try using a 5030 ccw 3 blade prop with 1811 motor it runs cool with 3 blades. I have also toyed with the Idea of using two motors. one on each side so I would have equal thrust in either direction if you use a Y adapter on ESC's to the Gyro this could be accomplished as one motor increases the other would decrease if Esc was programmed right it also keeps both motors cool since one is always moving air across the other one. You would have to play around with cw and ccw props to get this down. It looks good on the bench but I blew my wad on Christmas and my project fund going to have to wait for a bit.


Ray
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Old Dec 26, 2012, 08:12 PM
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I don't know if one gyro will work since i have two cheep ones hooked up now. oh well probably just a wet dream. Looks cool if it don't work i'll use it for a weed wacker.
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Old Dec 26, 2012, 09:01 PM
John
Australia, QLD, Brisbane
Joined Aug 2012
542 Posts
BThirsk -
Thanks for your comments. And I don't think anyone here would call you crazy: plus you solved the great F45 feathering shaft mystery that had us all stumped (if I remember rightly) amongst others. Won't forget that particular one, either .

Ray -
Yep, working on the 1811s as we speak. Have found out WHY the Xtreme converter won't handle the unmodified tail signal (can post scope traces if anyone is interested). But now hunting for a fix (though yours is certainly one approach)!
My own crazy idea was a dual rotor F45 - Chinook, not coax. Even can't see why an MJX F39 pcb couldn't work for a mockup: just imagine the lift from two AD300XLs!
All this to disguise my slow progress in learning CP lol.
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Old Dec 26, 2012, 11:36 PM
John
Australia, QLD, Brisbane
Joined Aug 2012
542 Posts
Well, finally have a working (mockup) BL tail: or servo tail.
I have to say is all credit to TumppiT: how on earth he found the problem - and solved it! without my electronics workshop resources is beyond me.
The basic problem is that the stock drive to the tail motor is a PWM signal, with a (very approx) 2kHz frequency.
The Xtreme converts this to a servo/esc compatible signal, again a more precise PWM, but at a strictly controlled PRF. However, this conversion relies on a 'heartbeat' signal from the original drive frequency (however short) to function.
With the standard FET, at much over half right rudder, this signal vanishes entirely: so the converter goes back to zero output. With an alternative (or higher power) FET this signal is preserved, so the converter maintains full right Yaw.
This is NOT a function of any power requirement, just a peculiarity of the drive signal/FET combination.
The pics below show the story. That showing the very short tail drive pulse is taken at full right rudder: and is totally absent when the original FET (actually MOSFET) is used.
Again, my thanks to TumppiT for leading the way!
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Old Dec 27, 2012, 02:02 AM
Eternal beginner
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France, Alsace, Strasbourg
Joined Jun 2012
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Quote:
Originally Posted by OldOz View Post
Probably the easiest way (if you're right, and I think you are) is to mount the main PCB upside down as well - at first thought, that should put EVERYTHING back where it was? Plenty of room in the 45/450 chassis.
Oh yes I think this could work !

Quote:
I believe the MJX head and 45deg flybar will always have a place as a 'fun' flier, and learning tool. It's the best, imo.
I totally agree !
Each time I fly it I have a large grin on my face

Quote:
All this to disguise my slow progress in learning CP
Don't worry, you're not alone !
I bought a Walkera Master CP 3 weeks ago, and for now, even if I don't crash (too) much, it's not yet a really pleasure for me to fly it, because it requests full concentration...

Regards, Roland
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Old Dec 27, 2012, 02:40 AM
John
Australia, QLD, Brisbane
Joined Aug 2012
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LOL -
+1 on that last one, Roland! - and more of a 'demand' than a 'request'
Cheers!
John.
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Old Dec 27, 2012, 02:44 AM
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Price on the mjx f45 went up by 10 dollaz again at banggood
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Old Dec 27, 2012, 05:03 AM
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United States, VT, Windsor
Joined Apr 2012
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I guess i been playing with the Quads to long I was looking at the Walkerra Scorpion at the two opposing motors on the tail. Well I still have a big box of parts and its 15 degrees and snowing here. About all the flying I can do is with the v911's and v929's. Not a whole lot of fun just hovering the big ones in the house.
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Old Dec 27, 2012, 06:03 AM
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United States, VT, Windsor
Joined Apr 2012
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The other thing to look over is the Blade SR ESC it is interesting it has a brushless main motor and a brushed tail motor in the same unit and lets you adjust the proportional to the tail. I have a small fortune in mine with auto pilot. But the thought has crossed my mind to trying the parts on the MJX project. (I never liked the thing anyway) I scored a spare Esc on Ebay for $20 but have to buy motors unless I use the ones I have on the SR.


Ray
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