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Old Oct 22, 2012, 08:50 AM
Fly Fast, Fly Hard, Fly Fun
rexless's Avatar
Canada, BC
Joined Apr 2012
1,454 Posts
Quote:
Originally Posted by BThirsk View Post
I thing the bobbing is the flybar swinging back and forth over center(90% to the main shaft) trying to stabilize that is causing the bobbing. I think low head speed and the correct updrafts and rotor wash all combine to creat this effect.

What type of issues did you have before your crash?
One of these days I'll see if I can get someone to film the heli as it happens. I'd love to see it, although I doubt even 60 f/s will give much detail.
I was flying down a narrow lane when the heli seemed to get stuck in a weird slightly forward, slightly nose down angle. I tried to fight back but the space was too small to allow recovery. I do small test flights there often and usually it's ok since I know it well. I'm not sure how I ended up in that position to start with. So long as there is no wind and no snow today I hope to give it another try in a more open space.

Quote:
Originally Posted by slothy89 View Post
Agreed, however there are people who just have to tinker for the sake of tinkering and IMO the F45 is a very suitable platform to do this. Even If the changes are largely over the top
This is so true. I'm learning tons by modding this little dragon. By the looks of it this is a great group as well.
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Old Oct 22, 2012, 10:16 AM
Brent 黑雁
BThirsk's Avatar
Canada, AB, Ponoka
Joined Jan 2012
1,756 Posts
Quote:
Originally Posted by War Horse View Post
I'll start by saying this (F45) is by far my favorte heli to fly with a high fun factor, but it is what it is , and the bang for the buck in stock form cant be beat. However much fun all these mods are, it makes more sense to move up a few grades to something of higher quality.

I'm a 40+ year professional mechanic/machinist/drag racer / bike builder and have built some crazy wheels in my time, once put a big block Ford engine into a Mercedes , but I think of the F45 as a Miata that just will never perform like a Ferraril, althought the Miata can be loads of fun.

Just my .02 devalued US cents worth
You are pretty close to right on that. I did some drag racing in the 70s with a 600hp Chevy Vega. It ended up with only the Vega Sheet metal.
In the F45 case, I think we are just trying to get it to Chevy level. I want it to handle close to a CP heli in response knowing full well it has it's design limitations.
I need to give 3 cents CND for this comment.
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Old Oct 22, 2012, 11:34 AM
Registered User
United States, CA, Modesto
Joined Aug 2012
828 Posts
The Bobbing

Do we think that lengthening the tail boom will help to resist some of the bobbing that we experience?
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Old Oct 22, 2012, 12:21 PM
Brent 黑雁
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Canada, AB, Ponoka
Joined Jan 2012
1,756 Posts
Quote:
Originally Posted by arrowshooter View Post
Do we think that lengthening the tail boom will help to resist some of the bobbing that we experience?
No, I don't think it would effect that at all unless the extra weight put you in a tail down postion in which case you would have a lawn dart. The only real reason to lengthen the tail is to give more tail authority.
Just grab your heli, spin to about hover speed, rock it back and forth, and whatch the flybar. I needs to work to find centre. Everytime it goes beyond center, the heli reacts and it now has to compensate for the new position. In most case, this is so subtle that it is not noticable. In the rare cases whe see, combinations of factors make the heli rocking and the flybar trying to correct it, make it only get worse. At least that is my theory from what I have observed and a bit of studying the mechanics.
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Old Oct 22, 2012, 01:49 PM
Registered User
The Netherlands, UT, Nieuwegein
Joined Sep 2012
78 Posts
Quote:
Originally Posted by BThirsk View Post
No, I don't think it would effect that at all unless the extra weight put you in a tail down postion in which case you would have a lawn dart. The only real reason to lengthen the tail is to give more tail authority.
Just grab your heli, spin to about hover speed, rock it back and forth, and whatch the flybar. I needs to work to find centre. Everytime it goes beyond center, the heli reacts and it now has to compensate for the new position. In most case, this is so subtle that it is not noticable. In the rare cases whe see, combinations of factors make the heli rocking and the flybar trying to correct it, make it only get worse. At least that is my theory from what I have observed and a bit of studying the mechanics.
What would happend if we would make the flybar longer or shorter ? or even lighter or heavier ? would it have any effect on the hobbling ?

And what would happend if we would put the flybar or something simillar to this under the heli to change the gravity of the flybar and i am allso very curios about the idea of putting a counterwise flybar under the heli so this functions as a coaxial rotor would this work ?

I think if there would be something that could make counter force under the heli this would somehow have positive effects because all the force focust on top of the helicopter and there is nothing under the helicopter to absorb or to compensate makes the heli somehow unstable in changes of gravity.

Can someone with knowledge responce on this...
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Last edited by eminemin; Oct 22, 2012 at 02:06 PM.
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Old Oct 22, 2012, 02:05 PM
Still learning to fly
Germany, SH, Lubeck
Joined Aug 2012
56 Posts
F645 with GA250 Gyro and Flysky TH9x Transmitter

Hello to all,
this is what i did the last three days:
I removed the PCB from the F645 and placed my Flysky reciever, then i placed a GA250, wich has got a wonderfull new Firmware ( http://www.rcgroups.com/forums/showt...=1493174&pp=50 ) then i configured the gyro and went out to fly... and it works! The gyro is very stable in heading-hold-modus, in rate-mode it drifts clockwise, but as the heading-hold-modus is really fine, you donīt really need the rate-mode. The only thing i have to do for now is to trim the pirostops, as the heli sometimes bounces on hard stops.
The heli could be moved very sensitive now with the TH9x, it is such a pleasure now to do exact turns in small places, i could not do this with the original transmitter.
A big compliment to OlliW, who did the job on the GA250 firmware and to all the others, who made the ER9 Firmware for the TH9x and other TX -> they did a great job!



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Old Oct 22, 2012, 02:41 PM
John
Australia, QLD, Brisbane
Joined Aug 2012
542 Posts
A truly awe inspiring mod!
Slothy89 is right though -
Quote:
"Agreed, however there are people who just have to tinker for the sake of tinkering and IMO the F45 is a very suitable platform to do this. Even If the changes are largely over the top"
Should be our thread motto.
But does it still 'bob' at all?
My own two cents is that I've noticed similar bobbing (but not as bad) on the 120SR, and even my MJX F39 (big coax, again nowhere near as bad). Can't help but wonder if it's simply a 'feature' of the 45 deg flybar? Theres no sign of it at all on my 450CP.
I've tried to follow BThirsk's (and Balr14s) more technical analysis, and a bit of 'light' wiki reading, but find myself somewhat boggled at the complexity of it all. Perhaps the only real problem is for the purist - or Solarcow, whose FPV might possibly be a bit vomit inducing - as otherwise the F45 does everything you could ask of a $100 heli.
But as before, all hail Hinnerk's trailblazing!
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Last edited by OldOz; Oct 22, 2012 at 02:55 PM.
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Old Oct 22, 2012, 03:13 PM
Brent 黑雁
BThirsk's Avatar
Canada, AB, Ponoka
Joined Jan 2012
1,756 Posts
Quote:
Originally Posted by Hinnerk View Post
Hello to all,
this is what i did the last three days:
I removed the PCB from the F645 and placed my Flysky reciever, then i placed a GA250, wich has got a wonderfull new Firmware ( http://www.rcgroups.com/forums/showt...=1493174&pp=50 ) then i configured the gyro and went out to fly... and it works! The gyro is very stable in heading-hold-modus, in rate-mode it drifts clockwise, but as the heading-hold-modus is really fine, you donīt really need the rate-mode. The only thing i have to do for now is to trim the pirostops, as the heli sometimes bounces on hard stops.
The heli could be moved very sensitive now with the TH9x, it is such a pleasure now to do exact turns in small places, i could not do this with the original transmitter.
A big compliment to OlliW, who did the job on the GA250 firmware and to all the others, who made the ER9 Firmware for the TH9x and other TX -> they did a great job!
Nice job. After not being able to get my signal convertor to recognise the signal from the PCB, I have been considering this as well. Now you have given my the incentive to do it.
Maybe you could do a step by step guide on what you did for us not so electrically inclined and post in your blog area.
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Old Oct 22, 2012, 03:18 PM
Ol' Chap. MJX F45!
Canada, ON, Toronto
Joined Sep 2012
19 Posts
I know alot of people were talking about the keychain camera's (aswell as myself) but I think I may want to go with the camera built for the MJX F45/F645, because it'll be more efficient then tying zip ties and other things to make the keychain camera be still and stay on the helicopter. It also weighs more than the original camera built for it. The KeyChain camera is 3 ounces while the MJX Built one is 1.5 I believe (not a huge difference). What do you guys think, The one that's built for it or the keychain camera (My MJX just arrived today )
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Old Oct 22, 2012, 03:30 PM
Brent 黑雁
BThirsk's Avatar
Canada, AB, Ponoka
Joined Jan 2012
1,756 Posts
Quote:
Originally Posted by eminemin View Post
What would happend if we would make the flybar longer or shorter ? or even lighter or heavier ? would it have any effect on the hobbling ?

And what would happend if we would put the flybar or something simillar to this under the heli to change the gravity of the flybar and i am allso very curios about the idea of putting a counterwise flybar under the heli so this functions as a coaxial rotor would this work ?

I think if there would be something that could make counter force under the heli this would somehow have positive effects because all the force focust on top of the helicopter and there is nothing under the helicopter to absorb or to compensate makes the heli somehow unstable in changes of gravity.

Can someone with knowledge responce on this...
In my blog, I have pictures of what I have done with the flybar. I have not had enough flights on it to know whether the bobbing is there or not. I only experienced it about twice in 150 plus flights.
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Old Oct 22, 2012, 03:44 PM
Registered User
The Netherlands, UT, Nieuwegein
Joined Sep 2012
78 Posts
Quote:
Originally Posted by BThirsk View Post
In my blog, I have pictures of what I have done with the flybar. I have not had enough flights on it to know whether the bobbing is there or not. I only experienced it about twice in 150 plus flights.
BThirsk i saw your modifaction with the paddles before and i am sure this will improve the heli in many aspects but i am allso curios about putting under the heli somekind of counterwise turning weights and what this would have for effect ?

Great job with the modifications !
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Old Oct 22, 2012, 04:06 PM
Brent 黑雁
BThirsk's Avatar
Canada, AB, Ponoka
Joined Jan 2012
1,756 Posts
Quote:
Originally Posted by eminemin View Post
BThirsk i saw your modifaction with the paddles before and i am sure this will improve the heli in many aspects but i am allso curios about putting under the heli somekind of counterwise turning weights and what this would have for effect ?

Great job with the modifications !
I don't think any of us could answer that question. Only experimenting would tell.
I honestly don't think it would do what you want. I think it whole only rob power and may cause undesired effects.
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Old Oct 22, 2012, 04:14 PM
Registered User
Joined Aug 2012
71 Posts
Damn...Im starting to have sputtering with my tail motor.
when it starts up..the tail wont go..untill i give it a little tap.

Does the metal teeth dont look completely straight..but ive never looked at them until now.

do i need a new motor?
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Old Oct 22, 2012, 04:32 PM
John
Australia, QLD, Brisbane
Joined Aug 2012
542 Posts
Probably, particularly if 40+ flights. Order a complete tail assembly (not much dearer).
Good luck
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Old Oct 22, 2012, 04:57 PM
John
Australia, QLD, Brisbane
Joined Aug 2012
542 Posts
PCloud-
The 'built for MJX' camera is pretty low res (640 x 480 from memory) and isn't really optimal for F45 AP. Rexless's video a few pages back (eg) is much better quality than anything I've done with the FO3432.
The extra weight of the keychain cam is really inconsequential - I think Markkona strapped a mobile phone under his heli back in the day.
I've ordered the Rexless cam (ebay) despite having 2 standard MJX compatible cams.

Edit - Video page 252 here, cam http://www.ebay.ca/itm/221059205423?...d=401472413984
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Last edited by OldOz; Oct 22, 2012 at 05:09 PM.
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