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Old Aug 14, 2009, 06:17 PM
It flies!!! ... so who cares ?
erdnuckel2's Avatar
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Quote:
Originally Posted by FlapHappy
I stand corrected Sven
Do you know how much they cost? I'm almost afraid to ask!
...

One thing just bugs the crap out of me....It just seems like there has to be a simple way to control that upper rotor. Or at least reduce the blade strikes. I wonder how the BL would fly with the top rotor at a fixed, neutral pitch?
...

Dale
Are you sitting down, Dale? I just browsed over the prices - such a heli will set you back somewhere close to 15K

BL question:
If you say fixed neutral pitch - what means neutral? (can't be 0 right, as that would not help for anything ...) I'm sorry, but my knowledge about the principles of helis is kinda limited ...

Sven
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Old Aug 14, 2009, 09:29 PM
Ornitopters Taste Like Chicken
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Nashville, TN
Joined Jul 2009
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15k ? Gulp.... Kinda makes the Helibaby look like a bargin.

Anyway, back to the real world of Lamas

I have seen the videos of guys that have put on the turbo (extended) shaft along with using the 400D blades as well as shortening the flybar. I know all of these mods work great and makes the BL a great co-ax instead of a lame one. But I am just thinking of trying different solutions to solve the same problem. I like to design, build and tinker so this is entertainment for me. If you are not into tinkering, buy the Walkera 400D

Ok Sven, I'll do my best to explain the blade strike problem.

Even in the "neutral" position, Co-ax blades have a positive angle of attack.
This is why all you need is throttle to get lift.
I may be way wrong here but I am thinking that making the upper rotor "fixed" would still give lift but it wouldn't be influenced with a flybar nor with any input to the lower rotor. Think of the flybar as a gyroscope. When you are flying straight and level, the flybar is parallel to the ground. If you suddenly pitch the nose up, the lower rotor flexes up in front while the upper rotor actually flexes down. The reason why is that the flybar is trying to stay parallel to the ground but now the shaft is tilted backwards which effectively gives the upper blade a negative attack angle in the front, (making the upper blade flex down).
Ok...I know it might be hard to visualize with my description.
If you tilt your swash plate up in the front, then pick up your heli by the flybar, keeping it level, with the upper and lower blades in line with the fuselage, and then tilt the nose of the fuselage up you can see what is happening. Look at the angle of attack of the upper and lower blades. You can see how the blades will flex and strike each other out in front of the heli.

I am not sure and only guessing that "fixing" the upper rotor and removing the flybar would make it too unstable. That is why I am thinking that leaving the flybar might stabilize by gyro effect even though it has no influence on the upper rotor.

Remember guys, I am not advocating this as a mod, just as a concept to understand flight characteristics to create better designed helis. I use my heli as kind of a test bed for my wacky ideas.

Dale
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Old Aug 14, 2009, 09:53 PM
It flies!!! ... so who cares ?
erdnuckel2's Avatar
Joined Mar 2009
9,137 Posts
Quote:
Originally Posted by FlapHappy
...

Ok Sven, I'll do my best to explain the blade strike problem.

Even in the "neutral" position, Co-ax blades have a positive angle of attack.
This is why all you need is throttle to get lift.
I may be way wrong here but I am thinking that making the upper rotor "fixed" would still give lift but it wouldn't be influenced with a flybar nor with any input to the lower rotor. Think of the flybar as a gyroscope. When you are flying straight and level, the flybar is parallel to the ground. If you suddenly pitch the nose up, the lower rotor flexes up in front while the upper rotor actually flexes down. The reason why is that the flybar is trying to stay parallel to the ground but now the shaft is tilted backwards which effectively gives the upper blade a negative attack angle in the front, (making the upper blade flex down).
Ok...I know it might be hard to visualize with my description.
If you tilt your swash plate up in the front, then pick up your heli by the flybar, keeping it level, with the upper and lower blades in line with the fuselage, and then tilt the nose of the fuselage up you can see what is happening. Look at the angle of attack of the upper and lower blades. You can see how the blades will flex and strike each other out in front of the heli.

I am not sure and only guessing that "fixing" the upper rotor and removing the flybar would make it too unstable. That is why I am thinking that leaving the flybar might stabilize by gyro effect even though it has no influence on the upper rotor.

Remember guys, I am not advocating this as a mod, just as a concept to understand flight characteristics to create better designed helis. I use my heli as kind of a test bed for my wacky ideas.

Dale
Ok Dale, I can visualize that ... I also hope EQMOD is reading in the background
Now here is the thing:
Wouldn't the basic problem still persist, even if you get rid of the flybar? I mean - it was here on the forum where thesteelcube introduced his flybarless walkera 53Q so there are people (EQMOD also eliminated the flybar and I think dendog220 did too) who did that. I doubt they would be able to eliminate blade strike by "fixing" the upper rotor in one posistion (completely horizontal, if I interpret your neutral right). If you read the threads they made, each of them actually tackled the problem exactly the other way - buy trying to get MORE control over the upper rotor instead of eliminating the need for control .... (now I don't know if I put my thoughts down in a way that is ok to follow). I have the feeling that the approach of the problem through a double swash solution is the more promising one ...

Regards,
Sven

Can't wait, until the first guy on here shows us a double swash plate BIG Outdoor LAMA ...
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Old Aug 14, 2009, 11:05 PM
Ornitopters Taste Like Chicken
FlapHappy's Avatar
Nashville, TN
Joined Jul 2009
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Sven,
I absolutely agree that full control of the upper rotor using a second swash plate is the best by far! But as you know, the helis with the upper swash are very complicated, (and expensive).
I will have to look through the threads for the mods you referenced.
I am not saying to remove the flybar, only to remove (or reduce) it's influence on the upper rotor. It would have to reduce blade strike because the upper rotor would NEVER have a negative angle of attack causing the upper rotor to flex down. Even at neutral "horizontal" the blades are designed with a positive attack angle so it would tend to always flex up.
But I know what you are saying....The choice is to either get more control of the upper rotor or to find a way to "automaticaly" control the rotor which is not likely to kill blades.
I don't know, I am just throwing ideas out here.

I would love to see how the Sikorsky X2 handles this problem. Those rotors are very close to each other.
From what I understand, it is all "fly by wire".

Here's one for ya.... You could put a micro reciever, servos and a swash plate on the upper rotor....that can handle something like 30G's

I agree with you...I would love to see a simple two swash co ax.

Dale
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Old Aug 15, 2009, 12:59 AM
Ornitopters Taste Like Chicken
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Nashville, TN
Joined Jul 2009
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Sven,
Hey I just have to tell ya that I know you know a thing or two about helis.
I just had to play along with you when you said that you had a limited knowledge of helis.
I may be new to joining the groups but I have searched the threads for quite some time and I have been playing with everything rc for years. I am 49 and still learning
I have seen Eqmod's lama with the gyro setup. Very cool!
But my question is a real one. I just wonder how a coax would fly with the upper rotor "fixed". It is more of a "What if" kind of question.
I guess I'll just have to put some wedges in it and find out

Dale
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Old Aug 15, 2009, 01:23 AM
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fixing the movement of the top rotor and put a 3 axis gyro on and let the servos do the balancing work. that's doable, but as u can see from EQ's video, it's not all that stable. I don't think u can safely hover that setup head-in for too long in a small room. but that setup may be nice for outdoor flight.

I tried a flybarless setup myself, but in the end still prefers the mechanical setup, as I fly my v4 head-in 'in my closet', literally.

I think EQ's dualswash setup is cool enough; it is all-rounded and gives benefit in both worlds.
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Old Aug 15, 2009, 07:55 AM
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Okay guys, I'm having trouble with my BL.
Thought the brushed motors were going bad b/c I could not get lift. The heli would float only 4 feet off the ground.
Switched out the brushed motors. Still same problem. Thought it was the battery. Used a new battery. Still same problem.

Anyone know what the problem is?

Bad 3-1 controller?
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Old Aug 15, 2009, 08:53 AM
It flies!!! ... so who cares ?
erdnuckel2's Avatar
Joined Mar 2009
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Hi xdrive,

I am having a similar problem with my little L4 right know - not as bad as you describe (yet), but its getting there - checked same things like you - same result ...
... so what could it be? Reading suggest one of the following:
- bad 3in1 like you suggest (that would be a real PITA)
- binding somewhere or bad gear mesh
- bad bearing(s)
- bad connection or connectors somewhere
(maybe it also got to do with those fuses they put on the motors now (those square things which were not there with the first BIG Lamas to all I know)

other than that I would run out of ideas ...

Regards,
Sven
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Old Aug 15, 2009, 09:25 AM
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Sooo frustrating!!!
What could it BE?
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Old Aug 15, 2009, 09:46 AM
It flies!!! ... so who cares ?
erdnuckel2's Avatar
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Quote:
Originally Posted by xdrive
Sooo frustrating!!!
What could it BE?
Which of the above mentioned possibilities (except bad 3in1) did you already check??
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Old Aug 15, 2009, 10:12 AM
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Everything appears to be fine.

If the 3-1 is defective, should it still be able to let me float 4 feet off the ground with full control?

I did realize right before I had this problem, when I wanted to move forward the heli would dip. As if not enough power was going to the motors.
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Old Aug 15, 2009, 10:19 AM
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This appears to be a voltage regulation issue with the controller. As if not enough power is being delivered to the motors.

If it is the 3-1, is it worth the time and $$ to get another 3-1 from Esky? Aren't I replacing junk with another junk?

Are there any other 3-1s I can replace the junk esky one?
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Old Aug 15, 2009, 10:27 AM
Ornitopters Taste Like Chicken
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Quote:
Originally Posted by dendog220
fixing the movement of the top rotor and put a 3 axis gyro on and let the servos do the balancing work. that's doable, but as u can see from EQ's video, it's not all that stable.

Hi Dendog,
Yes, I'm talking about fixing the movement of the top rotor AND removing the connecing rod, but NOT removing the flybar. Of course the flybar would have to transfer it's force to the shaft somehow. Maybe using a spring in place of the connecting rod. This would dampen the force and give some lag time. You could possibly "dial in" the stability you want by using stronger or weaker springs.
The idea is to let the flybar act as the gyro WITHOUT changing the pitch of the upper rotor.
Replacing the flybar with a gyro is the same thing. They are both gyros, one electric, one mechanical. But a gyro mounted to the frame is not the same as a gyro controling the attack angle of a rotor.

But my idea might still be too unstable. I don't know, but that is why I have posted the question.

Anyway, maybe tis is best left to a different thread

Dale
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Old Aug 15, 2009, 11:17 AM
It flies!!! ... so who cares ?
erdnuckel2's Avatar
Joined Mar 2009
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Quote:
Originally Posted by xdrive
This appears to be a voltage regulation issue with the controller. As if not enough power is being delivered to the motors.

If it is the 3-1, is it worth the time and $$ to get another 3-1 from Esky? Aren't I replacing junk with another junk?

Are there any other 3-1s I can replace the junk esky one?
I only know Walkera making helis in the BL size ... oh yeah, and ART - Tech ... (both of them are rebranded and sold under different names in Europe)
But about neither of them you really hear great praise about their electronics.

So this leaves another question: will it make sense to go brushless right away instead (someone posted a link here to an eBaysite that sells the AEORC type brushless kit for 55$ shipped (or at least did)
The other possibility would be sticking to brushed motors, BUT STILL go for seperate parts - an experiment that I would like to perform, but cannot afford at the moment - plus the parts are only partially available anyways.
This solution also would be quite expensive - but one day I know I will do it anyway, just for the sake of doing it
Taking two brushed Xtreme 380motors, 2 x 25A brushed ESC's and a cheap HH gyro and the Dionysus mixer ... very curious, how that will work ... like I said, one day I'll find out

I know, thats not really helping, but if I were in your shoes and could afford the brushless solution (from eBay) I would go for that ...

Regards,
Sven
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Old Aug 15, 2009, 11:39 AM
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I already bought a brushless kit for the big lama.
Waiting for it to arrive.
I also bought a bunch of replacement parts for the big lama.

Still trying to figure out if my problem with not being able to hover past 4 feet is mechanical or electrical issue.

I am determined to figure this out. Hope my frustration, money spent, and time will HELP others out if they encounter the same problem as me in the future.
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