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A Main Hobbies . Boca Bearings . Modefo's RC Helicopters

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Got Jet Fuel? Turbine Helicopters > Coaxial KA-50 Turbine
 
 
Havoc
Key Veteran
Location: Ky.

Quote 
don't think differential torque is the issue

You are right but at least I caught that and removed it before you posted.
02-27-2008 02:26 PM
 
 
iflynething
Senior Heliman
Location: Charlotte, NC-USA

Any advantage to using three blades verses two with construction complications.

I'm sure you get more lift from them

~Michael~

Some peope see things, and say Why......I dream things that, never were and say WHY NOT?
02-27-2008 04:06 PM
HOMEPAGE  
 
 
Peter Wales
Key Veteran
Location: Orlando Fl

2 blades would have a difficult linkage getting around 180 degrees from bottom to top swashplate.

Peter Wales
02-27-2008 07:47 PM
HOMEPAGE  
 
 
FCM
Elite Veteran
Location: Back in Blighty!

No, there would still be a problem with autoing due to the tail gyro being active in the wrong direction. I imagine this would lead to a pirouetting auto unless a change of gyro/servo direction could be set up in your TX linked to your throttle hold switch perhaps? Practicing auto approaches and bail-outs could be real interesting!

Paul.
02-28-2008 01:47 AM
 
 
iflynething
Senior Heliman
Location: Charlotte, NC-USA

Thanks Peter, that makes perfect sense now that you mention that

~Michael~

Some peope see things, and say Why......I dream things that, never were and say WHY NOT?
02-28-2008 02:41 AM
HOMEPAGE  
 
 
Peter Wales
Key Veteran
Location: Orlando Fl

Well the instructions (in German) say nicht mit das autorotations. Not really, but it does warn against autos. I cant think of a gyro which can have its direction reversed from the Tx and even my mighty MC-24 cant reverse a servo in a different flight mode.

Nope, das auto is verboten Ja?

Peter Wales
02-28-2008 02:50 AM
HOMEPAGE  
 
 
human213
Senior Heliman
Location: malibu

Autorotations

A few facts to clarify the auto capability with the coaxial...

1)The gyro must be turned off...this is best done with a condition
with throttle hold activation sequencing.

2)Simultaneously, the servo must be reversed, so the inputs are now correct, with the gyro turn off condition, as above...

3)When flaring, the direction is not reversed again.
Yaw control is maintained, but with reduced amplitude.

4)These conditions are easily programmed with a unit capable of such...by way of example, the FC-28 will do so, and is over 15 years old... so will my new FX-40...



kindest,

michael

Not everything that can be counted counts, and not everything that counts can be counted.
02-28-2008 07:17 AM
 
 
wilerbee
Senior Heliman
Location: Hong Kong

I ordered the same mechanics from scalecopter in Germany and will be building the KA-50 for it. The factory will hopefully be on schedule and I will have the first fuselage in late April/early May. Lars from scalecopter has already expressed interest in selling my fuselages in Europe. I will be working on the retracts and scale accessories once I have the fuse. It will be approx. 1/6 scale (based on 2.4 m rotor). If anyone is interested I can keep them updated.

ps the factory is CNCing the male moulds now.
02-28-2008 02:30 PM
 
 
Elliot
Heliman
Location: Germany

Dear Willis,

as stated, your KOAX is ready to go and will leave Germany on tuesday next week. The 2.40m rotordisk is fine; we are just flying one exactly using this diameter. It performs quite nice, you will probably like it. To built the KA50 sure will be a big pleasure. Just saw the real thing a few weeks ago. A very impressive machine indeed.

We will do some auto-tests as well in a very short time. I will let you folks know how it will go.

Kindest,

Lars
02-28-2008 03:57 PM
HOMEPAGE  
 
 
human213
Senior Heliman
Location: malibu

Jung Factory Fuselage price list, and retracts

Due to multiple requests:
Original scale fuselage engineered by Jung Modelltechnik



Fuselage Kamov Ka-52:
scale 1:6, length 2.30m, wingspan 1.3m, semi-scale execution
material glass fiber, reinforced with carbon, styrofoam sandwich construction (for low vibration)
withe coating, with many details and thousands of rivets
prefabricated execution, composed of:
front part, middle part, tail part, 2 great openings for maintenance
removable wings with fitted carbon pipes and assembly fastening
removable tail part
yaw rudder, manufactured fitted in hinges, linkage and servo holder
horizontal tail
four-part panel doors for undercarriage with hinges, already glued together
transparent window material, deep drawn
all window openings and ventilation slot are cut out
two turbines front covers with brackets
vertical frames for coaxial rotor mechanics fitted in and glued
all other frames also fitted in and glued
in the fuselage passed on to fastenings for removable wings and glued together
prepare for retractable landing gear
witout guns, missiles etc. (projected)
introductory price 3.400,- Euro (incl. 19% tax)
the price is valid until March 31st, 2008, delivery date May 2008
retractable landing gear:
electrical 3 leg retractable landing gear, semi scale execution
front retractable landing gear in a rotatable execution, with in the middle centring
execution complete into aluminium
inclusive wheels
inclusive special electronics (no servos etc. required)
price 1.280,- Euro (incl. 19% tax)
www.cad-modelltechnik-jung.com 18.2.2008

Not everything that can be counted counts, and not everything that counts can be counted.
02-28-2008 04:09 PM
 
 
wilerbee
Senior Heliman
Location: Hong Kong

Thanks Lars !!
02-29-2008 03:51 PM
 
 
fredd
Senior Heliman
Location: UK - London

human123,

I'm not sure I follow your point 3)
"When flaring, the direction is not reversed again.
Yaw control is maintained, but with reduced amplitude."

If you rudder servo is reversed, wouldn't flaring be potentially problematic (of course only if you plan to use the rudder).

I assume that the mixing rudder to collective doesn't need to me modified if there is negative pitch.
03-01-2008 07:26 PM
 
 
human213
Senior Heliman
Location: malibu

No, it would not...

...only if you were to return power input, then the throttle hold and mixing would need to actuated. The reversal is correct for all
inputs in an auto, be it positive or negative collective movement.


michael

Not everything that can be counted counts, and not everything that counts can be counted.
03-02-2008 09:36 PM
 
 
umdpru
Elite Veteran
Location: Massachusetts

what exactly is the mechanism that causes the rudder to reverse? I'm trying to wrap my brain around this one.
03-02-2008 09:48 PM
 
 
human213
Senior Heliman
Location: malibu

Hi Um

...on power, vs reverse flow for auto...


control is reversed in auto, normal for power transmission input...

blades driven in auto by net upward slipstream... down to up net flow...


Yaw control maintained, but at lower amplitude in auto...(transmission
drag torque) Large rudder also very effective in this mode.



See earlier white paper and posts by me on coax aerodynamics,

via Kamov factory...

m

Not everything that can be counted counts, and not everything that counts can be counted.
03-02-2008 10:43 PM
 
 
human213
Senior Heliman
Location: malibu

Coming soon...

pics of fuselage, landing gear, and the new 3 meter KMAX...



KA-32 fuselage currently in the works, 3.2 meter rotor span, and
can be flown with current 2.4 meter rotorspan mechanics....turbine in front....

Please PM me if anyone is interested in any of this models, due to many requests.. They are also available professionally built by the designer, and test flown.




michael

Not everything that can be counted counts, and not everything that counts can be counted.
03-02-2008 10:48 PM
 
 
umdpru
Elite Veteran
Location: Massachusetts

I understand now. In a coaxial design, yaw is accomplished via differential collective input to the two disks. increase the pitch on one while decreasing it on the other and you get a net torque in one direction - with power.

Without the yaw would reverse. Interesting. I never realized that about an auto....
03-03-2008 12:59 AM
 
 
human213
Senior Heliman
Location: malibu

This is done electronically

in the coaxes of Kamov.
Aerodynamically they are over 13 percent more
efficient than conventional, and have a far greater collective reserve and lower auto sink rate.


michael

Not everything that can be counted counts, and not everything that counts can be counted.
03-03-2008 03:29 AM
 
 
fredd
Senior Heliman
Location: UK - London

Michael,

it took me a few minutes to understand why flow was what really mattered and not pos / negative pitch. Thank you.
03-03-2008 06:47 PM
 
 
human213
Senior Heliman
Location: malibu

Which is why we always....

...go with the flow....





m

Not everything that can be counted counts, and not everything that counts can be counted.
03-03-2008 06:58 PM
 
 
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Got Jet Fuel? Turbine Helicopters > Coaxial KA-50 Turbine
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