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Old Mar 25, 2008, 02:02 PM
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Lama V4 Dual Swashplate Mod Project

The dual swashplate mod allows a coaxial heli such as a Lama V3 or V4 to have directional pitch data not only on the lower blades but also on the upper blades as well. The aim is to improve the Lama's response on pitch/roll commands. This means connecting the main swashplate to the upper blades. However, the upper blades are rotating in the opposite direction thus a second swashplate is necessary in order to pass pitch data to the upper blades. It is possible to implement the concept less the metal parts by using another heli's parts such as the CP2. In order to have a 2nd functional swashplate, this swashplate has to be connected to the primary swashplate to four points by means of four linking arms.

The picture below shows a CP2's swash as the 2nd swashplate and a couple of the CP2's pitch links which all have the right size and lenght to connect the two swashplates together.





The mod requires four balllinks on the main swashplate to connect it to the 2nd swashplate however there are only two thus we need to fabricate one to allow for four balllinks.



Basically i got this plastic part from a spare Lama V4 swashplate head and trimmed it, glued it on the cnc swashplate surface and added two screws to secure it.

Connecting the two swashplate together;





With the added Lama V4 blades;



Here is a video of the dual swashplate links in action;

LAMA V4 Double Swashplate Mod (0 min 50 sec)


The only thing that is missing is mounting the 2nd swashplate to a mixing arm going to the upper blades.


CP2 Parts that were used:

SwashPlate : EK1-0235 (inner brass ball removed to fit Lama shaft)
Swashplate Links : EK1-0234 and EK1-0245

Upper swashplate to upper blade links: EK1-0236, EK1-0229 (L-Arm)

Lama Parts that were used:

Swashplate Head for the additional two ball-links: EK1-0571


Detailed Build Log here:

http://www.rcgroups.com/forums/showthread.php?t=845669


UPDATE:

bigmark61's upper swash to upper blade link design using a "V-link" configuration is a better way in maintaning the upper swash to upper blade 90 degree phasing. See thread here;


http://www.rcgroups.com/forums/showthread.php?t=856425
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Last edited by EQMOD; Sep 09, 2008 at 11:46 AM. Reason: add parts list
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Old Mar 25, 2008, 02:33 PM
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But you would lose all of the stability provided by the independance of the flybar gyro. It would certainly be more responsive but a challenge similar to a FP single rotor to just hover. At this point, you've lost the stability and simplicity of a FP coaxial; why not just buy a small FP single?

Regards
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Old Mar 25, 2008, 06:04 PM
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Verry Nice, you continue....
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Old Mar 25, 2008, 06:28 PM
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Quote:
Originally Posted by rbinc
But you would lose all of the stability provided by the independance of the flybar gyro. It would certainly be more responsive but a challenge similar to a FP single rotor to just hover. At this point, you've lost the stability and simplicity of a FP coaxial; why not just buy a small FP single?

Regards
Stability is retained by means of a mixing arm. It should look somethine like this;



But instead of connnecting the upper pitch arm to the lower swashplate it gets connected to the 2nd swash.
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Old Mar 25, 2008, 07:29 PM
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I know what you are trying to do here and it's a noble attempt. One of the problems is that none of your photos show the concept to completion.

I assume that your last photo is missing the ball link on the other side from flybar to rotor? A degree of stability would be maintained with Bell-Hiller mixing, but nothing like the original Lama. In comparison, it will be a much harder helicopter to hover. The only reason these are so simple to fly is because the upper rotors and flybar comprise a gyro that keeps the helicopter extremely stable. If this gyro is restrained at all, even with Bell mixing, stability is exponentially degraded.

Best of luck in the modifications, but this is a road well-traveled. These simple coaxials exist for the market that enjoys them; easy to hover and fly indoors. There is nothing that can be done in this rotor span without significant compromise.

Regards
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Old Mar 25, 2008, 11:13 PM
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Quote:
Originally Posted by rbinc
I know what you are trying to do here and it's a noble attempt. One of the problems is that none of your photos show the concept to completion.

I assume that your last photo is missing the ball link on the other side from flybar to rotor? A degree of stability would be maintained with Bell-Hiller mixing, but nothing like the original Lama. In comparison, it will be a much harder helicopter to hover. The only reason these are so simple to fly is because the upper rotors and flybar comprise a gyro that keeps the helicopter extremely stable. If this gyro is restrained at all, even with Bell mixing, stability is exponentially degraded.

Best of luck in the modifications, but this is a road well-traveled. These simple coaxials exist for the market that enjoys them; easy to hover and fly indoors. There is nothing that can be done in this rotor span without significant compromise.

Regards

I already have the prototype with the 2nd swashplate to upper mixing arm link. The project mod is done in phases and i always post them per phase completion.

Test flight:

The hover is very much stable (just like the original lama hover feel) except that when you start sending hard aileron and elevator servo movement commands (roll and pitch) the heli moves fast . This should be a good wind breaker and a fast flyer

Anyway this can be compensated depending on user preference by specifiying servo arm throws limits from the TX side (i am using a Futaba 6EX). Will post pictures and video of the flight.
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Old Mar 26, 2008, 01:04 PM
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UPDATE: Day 3 - Linking the upper swashplate to the upper blades + Test Flight Videos

Here is what i did in linking the upper swashplate to the upper blades' mixing arm. To keep the link upright i used 3 points of the "CP2" swashplate as a support.

Pitch Link Mounting:


Mini stabilizer arm for the pitch link:


Mixing Arm Mounting:


Test flight Video:
Again, i have to apologize for the lighting as i can only take daytime shots during weekends. Here is a combination of hover and HARD aileron and elevator commands sent to the heli. This is to demonstrate how agile the Heli is after the dual swashplate mode and how the stability is retained as demonstrated during a Heli Hover. Take note, no blade strikes as BOTH Upper and lower blades are shifting on the same direction even if they are counter-rotating from one another;

Lama V4 Dual Swashplate Mod Flight demo (1 min 21 sec)



Blade Tracking Demo Video:
Here is a demo of the dual swashplate mod and the effect the pitch passing from the lower swash to the upper swash then up to the upper blades. You can clearly see how the angle of the upper blades follow the lower blades as i enter the aileron and elevator commands to heli;

Lama V4 Dual Swashplate Mod Blade Tracking Demo (1 min 15 sec)


Pitch Link Demo Video:

Here is a short clip on how the upper swashplate moves and the upper blades change pitch when aileron and elevator commands are sent to the lower swash.

Lama V4 Dual Swashplate Mod Upper Swash Pitch link demo (0 min 57 sec)
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Last edited by EQMOD; Sep 09, 2008 at 11:47 AM. Reason: added some comments
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Old Mar 26, 2008, 07:45 PM
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Quote:
Test flight:

The hover is very much stable (just like the original lama hover feel) except that when you start sending hard aileron and elevator servo movement commands (roll and pitch) the heli moves fast . This should be a good wind breaker and a fast flyer

Anyway this can be compensated depending on user preference by specifiying servo arm throws limits from the TX side (i am using a Futaba 6EX). Will post pictures and video of the flight.
With all due respect (and I'm sincere as I admire your experimentation), the helicopter was in an actual hover for about a second in the entire video, under your cyclic control on the stick; not in the inherently stable "handsfree" hover of a factory helicopter. Not sure if you understand just what provides the stability for beginners in these helicopters, but the second you dampen or mix the flybar, the factory stability is gone. You can keep claiming the contrary all you want, but it's simple gyroscopic physics.

Perhaps you could have someone video over your shoulder to show that your TX inputs and the helicopter's flight is "just like the original Lama feel"? Then maybe a video of the helicopter in simple patterns?

Regards
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Old Mar 26, 2008, 09:47 PM
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Quote:
Originally Posted by rbinc
With all due respect (and I'm sincere as I admire your experimentation), the helicopter was in an actual hover for about a second in the entire video, under your cyclic control on the stick; not in the inherently stable "handsfree" hover of a factory helicopter. Not sure if you understand just what provides the stability for beginners in these helicopters, but the second you dampen or mix the flybar, the factory stability is gone. You can keep claiming the contrary all you want, but it's simple gyroscopic physics.

Perhaps you could have someone video over your shoulder to show that your TX inputs and the helicopter's flight is "just like the original Lama feel"? Then maybe a video of the helicopter in simple patterns?

Regards

The duration of hover is basically upon the user's control. Obviously we can hover longer than that that is by simply not applying any aileron/elevator correction (handsfree). If the heli is accurately trimmed and if the user does not apply any cyclic corrections (aileron, elevator), one side of the mixing arm (where the 2nd swashplate is connected) will remain constant. The other side of the mixing arm where the flybar is connected would still function as originally designed - that is to keep the heli upright and "floating" as it will equalise the the pitch on both upper blades due to the gyroscopic effect of the flybar. It is as if the flybar is still directly connected to the side of the upperblade holders.

I wouldnt say that the factory stability is eliminated as i could achieve the flybar induced stability through the mixing arm. That is the originally intended purpose of this mixing arm - that is to combine the "stability" inputs of the flybar and the cyclic corrections coming from the 2nd swashplate. The pitch of the upper blades is actually the average of the two inputs on the mixing arm; flybar and swash.- (mixing arm mechanics).

From the video alone, you would easily know if the pilot is applying any aileron / elevator correction at the TX's stick as the heli's body would change angle due to the correction. If no inputs are applied, one side of the arm will become fixed, and since one side of the mixing arm is fixed, the upper blades will simply remain in parallel with the flybar's gyroscopic plane and would keep the Lama heli in constant hover (which is basically what i termed as "the Lama hover feel"). It is as if the heli is dangling from the center of the upper blades with the shaft directly perpendicular to the upper blades's plane.

This mod is actually getting the best of both worlds, a stable heli that can hover handsfree, a fast and aggressive flyer which is good for windy environment.

Hope this explanation helps.
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Last edited by EQMOD; Mar 26, 2008 at 10:04 PM. Reason: add a few lines below
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Old Mar 26, 2008, 11:14 PM
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This mod is actually getting the best of both worlds, a stable heli that can hover handsfree, a fast and aggressive flyer which is good for windy environment.
You don't seem to understand anything I am saying, and it isn't my opinion.

Prove it with video. Show us that it hovers with the same ease as a stock Lama. Show us your TX inputs as you fly the helicopter.

Okay?

From the video, the heli only goes fore and aft with but a second of hover.

Show your skills. Fly some simple patterns as well.

Regards
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Old Mar 27, 2008, 02:04 AM
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Quote:
Originally Posted by rbinc
You don't seem to understand anything I am saying, and it isn't my opinion.

Prove it with video. Show us that it hovers with the same ease as a stock Lama. Show us your TX inputs as you fly the helicopter.

Okay?

From the video, the heli only goes fore and aft with but a second of hover.

Show your skills. Fly some simple patterns as well.

Regards
Please check the mixing arm explanation. This is i think were the confusion is.

Its only a second of hover on the video because i chose to initiate the next aileron / elevator commands after a quick hover. I am trying to make the video clip as short as possible with all the tests i could fit in.


Will post the video as soon as i get a good lighting spot.
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Old Mar 27, 2008, 02:34 AM
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Very original work! Good for you. Since the rotor disk of the Lama is so small I presume it retains most or all of its original stability or it would be difficult to fly. In the video you yank it around in a confined space with apparent ease. Are you an advanced single-rotor pilot?
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Old Mar 27, 2008, 04:19 AM
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Quote:
Originally Posted by zen@lanset.com
Very original work! Good for you. Since the rotor disk of the Lama is so small I presume it retains most or all of its original stability or it would be difficult to fly. In the video you yank it around in a confined space with apparent ease. Are you an advanced single-rotor pilot?
technically i am still beginner as i can only do tail-ins. I am still practicing nose-in flights. I have a Honey Bee King II and a CP2
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Old Mar 27, 2008, 04:40 AM
This is what I want!!!
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Nice work and thanks for all the detailed photos.

How did you determine the phasing for the upper swash? Is is adjustable?
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Old Mar 27, 2008, 04:45 AM
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Originally Posted by Hokum Jim
Nice work and thanks for all the detailed photos.

How did you determine the phasing for the upper swash? Is is adjustable?

Just get the mirror image and flip. So basically its 180 degrees on the opposite side.

-- Correction: Its 90 degrees from the middle part of the mixing arm. So that is right under the blade.
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Last edited by EQMOD; Apr 30, 2008 at 02:28 AM.
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