Kamov Helicopters

Russian Kamov (KA) helies are the only ones that I know of that use counter rotating rotors in the real production helicopters. And I'm sure that they have a septate collective pitch control for each rotor. They must have. They don't have separate motors for upper and lower rotors like the little Lama. So yaw control must be made by the differential collective pitch between the upper and lower rotors. I am just curious about the mechanics. Collective and cyclic controls must be made independent for each rotor. How many swashplates they have? And how are they linked?

It looks to be precisely what we talked about - a 2nd swashplate between the two rotors, tilting the upper rotor.

I don't know anything about collective pitch yet but what else could the uppermost linkages be?

It's possible the inner shaft is hollow too and the controls for the uppermost CP linkages run through it. Couldn't duplicate that on a Lama.

I would guess the two turbines feed power into a single transmission which then splits it again for the inner and outer shafts, so one turbine can power both rotors if the other is hit or otherwise fails. I believe the Chinook has a similiar arrangement.

Slightly offtopic, how about making a Kamov V-100 out of two Lamas? Gawd that is sick. Almost as sick as the V-50.

Not quite clear from this picture, but it's 3 blade helicopter and it looks like they have 3 pushrods for each rotor. Each blade controlled independently. Obviously lower ring of the upper swashplate is somehow fixed to the outer shaft and the upper ring is fixed to the inner shaft. How they provide the collective for the upper rotor, is not clear. May be the swashplate can slide up and down without rotating using some splines on the shafts. I still assume that they have independent collective control for both rotors. It's the only way to control yaw. Or look at the very top of the upper rotor. There are some links there too. May be they have another shaft inside the inner shaft that is used for collective control? I would love to see the mechanical diagram of this setup.

Hanol wrote:

Or look at the very top of the upper rotor. There are some links there too. May be they have another shaft inside the inner shaft that is used for collective control?

That's what I said.

I wouldn't rule out the possibility of yawing via change in rotor speed. The Kamov does have two engines, and I think you could also brake the rotors independently in the transmission. All you have to do is cut the power to a rotor and let air resistance do the rest.

Just got this set from HeliHobby.com. Total price with cheapest UPS delivery was $26.62 to NJ from CA. Took 5 days.


Outer shaft is 110mm, comparing to 104mm of the Lama shaft (measured from the bottom of the gear to the top)

Upper holes in the outer shaft are 72mm high, comparing to 74mm of the V4 Lama. Also measured from the bottom of the gear.

So swashplate will be lower by 2 mm. And this can cause problems with stock motors. Also you will have to extend the inner shaft by 6mm, if it's fixed, or cut the outer shaft. I use DIY inner shafts with a set of DIY Teflon spacers. So it's not a problem for me.

I didn't try it yet. My outer shaft gear is still intact and I am not planning to replace it till it breaks. But inner gear is damaged, so I am going to replace it right now. I will keep you posted on the results.

Jack the R wrote:

...
Slightly offtopic, how about making a Kamov V-100 out of two Lamas? Gawd that is sick. Almost as sick as the V-50.

I don't know. I think if you will make the exact mechanical copy, it will be too complex and usability for RC flying will be very limited. Technically. This design idea is speed and fuel efficiency combined with VTOL. However, if you are into scale models, you can do something like this. Just take Esky Chinook, put it sideways, make a new body and attach a dummy push propeller.

Jack the R wrote:

Hanol wrote:

Or look at the very top of the upper rotor. There are some links there too. May be they have another shaft inside the inner shaft that is used for collective control?

That's what I said.

I wouldn't rule out the possibility of yawing via change in rotor speed. The Kamov does have two engines, and I think you could also brake the rotors independently in the transmission. All you have to do is cut the power to a rotor and let air resistance do the rest.

I read an article on this in one of the aviation magazines when I still used to fly real things. Before the Internet. And they reviewed Kamov designs. I don't remember all the details, but one thing I remember is that they used separate collective pitch mechanics on both rotors. Why I remember this is that the article went into details of autorotation. And the yaw control in coax helies is opposite during the power off autorotation. And this control can only be archived by the differential CP. So, I guess differential power can be ruled out. Especially when you have no power at all. :)

I spent some time on the Internet trying to find anything about the mechanics of Kamov's design, but couldn't find anything useful so far. :(

I played around a little with my spare plastic parts today -







I could mock up the necessary custom pieces in 3D and print them through shapeways.com, but shapeways print accuracy may or may not be enough. The question is, is it worth doing? From what I've read the Lama is unflyable without it's flybar, so this arrangement probably wouldn't work.

Maybe copy the HBFP's rotor head for the upper rotor?

What is the goal here, anyway? More manueverable Lama or aerobatic Lama? Can we get it to loop and roll with tilt on the upper rotor?

Kamov V-100 IIRC the Twister Skylift has smaller front rotors, so it wouldn't work for a V-100. Be great for a V-50.

I think the V-100 would work fine with two Lama frames attached by a carbon fiber tube. The body would only need to be a foam profile deal. Maybe use the tail rotor from HBFP as a pusher prop, or a similiar size setup. I've seen the Twister Skylift carrying around a Lama so I'm sure two Lamas can carry less than three Lama's weight. The wing would be providing lift too. Wish I had the time to mess with it.

The idea would be to get an aerobatic heli with the stability of a coaxial. You'd want the pusher prop to be functional, and a functional elevator. It'd probably need a more advanced radio with mixing functions so you can roll by cutting the power to one side.

The lower swashplate on your new outer gear shaft would be an advantage on V3 Lama. The extra 6mm above the upper holes will make no difference, so overall this is a much better part for V3 Lama than the V4 outer shaft I've currently got in it, and won't need any modification that I can see. Thanks for the report!

Sorry, I didn't reply for a while. So I got those white plastic gears and the lower one got stripped in no time. Like 10 flights. It was just a normal wear. And I think I found a reason why. Under power the frame tends to bend and the distance between the motor pinion and the gear increases. So gears don't mesh quite right. All you have to do is to put some spacer between the shaft holder tube on the frame and the top of the motor made out of Styrofoam or wood. This way you can also adjust the mesh and it will stay put. There should be just some little noticeable play. Then I installed the stock black inner gear and after many flights I don't see any wear. You don't have to mess with outer shaft gear, thought, as it's much closer to the bottom of the frame and it doesn't cause frame to bend. Also I think some grease can help.

I observed it by holding heli in my hand without the fuselage and applying full power. With blades on, of course. Frame bends a lot! I guess stiffer frame can solve this problem too, but I think that the simple spacer does the job just fine.

Pics? I'm having a tough time visualizing your mod.

Jack the R wrote:

Pics? I'm having a tough time visualizing your mod.

It's easy. The pinion gear of the inner shaft motor is pushed out by the force of the motor. This causes the frame to bend and it increases the gap between the gears, causing the premature wear. And the top of the motor tilts towards the main shaft. If you put some kind of separator there, you will prevent this. I used 3 little pieces of Popsicle sticks and a drop of crazy glue to keep them in place. I'll post a pix, when I charge my camera batteries. :)

Here we go.
Notice 3 little pieces of wood right in the middle of the picture. Little out of focus, but you can get the idea. This prevents frame from bending and moving the motor pinion gear out of mesh with inner shaft gear.



You can change thickness of this separator to adjust the mesh. There should be just a very little play between them, so they can rotate freely without any binding. Too much gap will cause stripping. Too little will cause friction.

I see, the pic makes it all clear.

What motors have you got in there?

Jack the R wrote:

I see, the pic makes it all clear.

What motors have you got in there?

Xtreme. Some say that Aero Nuts are better, but I didn't try them yet. It will be my next test after I burn out current motors. But Xtremes have much more kick comparing to stock. And they can grind your plastic gears real fast :) So proper mesh is important.

One thing I can tell you, trash the stock motors at once. They are real crap.

On the sad side of the story, my 2.4G 4in1 just died. It simply spins one of the motors at full speed when I connect battery. No reaction to transmitter :( But I have a hobby store not far away that carries parts for E-flight CX line, that should be identical. ...I hope. If not, I will have to order it from some place else and wait for the delivery some time next week. So right now I have my heli parts spread over several Chinese food containers and I can't put them together and fly them using the chopsticks alone. :)

I'll see how long it takes you to burn up those Xtreme motors before I buy - provided my stocks last. I haven't been flying much lately.

Jack the R wrote:

I'll see how long it takes you to burn up those Xtreme motors before I buy - provided my stocks last. I haven't been flying much lately.

I doubt Extreme motors will burn fast. They have ball bearings. Only things that may will need replacement are brushes. But they are cheap and can be replaced in seconds. Next thing that can get worn is the commutator. But it will take time. So don't expect a report on Aero Nuts any soon :)

As I said before, my 4in1 2.4G receiver from $106 kit died. It just keeps spinning one of the motors at full power. While all other controls work. I guess speed controller went bad.

Anyway, I went to the local hobby shop that carries E-flight CX helies. They didn't have 2.4G recivers, but had 72MHz 4 in 1. So I bought one, because I have 20 years old 9ch helicopter Futaba transmitter, that was very advanced at that time. About $1000 back then. Can set up curves, mixes, etc. Not that I need all this stuff for Lama, but there is one benefit. I can set up servo travel limits and curves on transmitter without messing up with the links on helicopter. It's heavier, but it has a neck strap.

Hanol wrote:

Jack the R wrote:

I'll see how long it takes you to burn up those Xtreme motors before I buy - provided my stocks last. I haven't been flying much lately.

I doubt Extreme motors will burn fast. They have ball bearings. Only things that may will need replacement are brushes. But they are cheap and can be replaced in seconds. Next thing that can get worn is the commutator. But it will take time. So don't expect a report on Aero Nuts any soon :)

Didn't you say you'd read that Xtreme motors were junk? Or was it Brutus5? That's why I haven't ordered them yet.

Jack the R wrote:

Didn't you say you'd read that Xtreme motors were junk? Or was it Brutus5? That's why I haven't ordered them yet.

All I said is that some people say that Aero Nuts are better and Xtremes are junk comparing tho them. This is from RC Groups forum. I can't tell if it's true or not. You know, people tend to exaggerate and you don't have to trust every word you read. So far I am happy with my Xtremes. But when they break, I will try Aero Nuts just to compare.

check out this co-axiel http://www.gyrodynehelicopters.com/coaxial_benefits.htm

chiefqm wrote:

check out this co-axiel http://www.gyrodynehelicopters.com/coaxial_benefits.htm

This page covers only the benefits of such design. However there are many problems, like having 2 shafts, 2 rotors, complicated control system, etc. So far only one shop in the world was able to make the production coax helicopters. 50 years after they started doing it. Many companies considered this, but found it not practical. I mean NOT PRACTICAL, considering all the factors. It may be better in theory, but the conventional single rotor design does the same job at lower cost and complexity. There are no really important benefits that can justify the coaxial design.

Quote :

"These technologies can potentially bring new rotorcraft capabilities that, to date, have been unachievable by the industry," said Sikorsky President Jeffrey P. Pino. "In addition to doubling the speed of helicopters, this technology can improve hot/high performance, maneuverability and low acoustic signature. Sikorsky's Light Tactical Helicopter concept demonstrates a way to package these capabilities into an airframe that is tailored to meet a range of military missions."

Link

Quote :

Current helicopter speeds are limited by rotor aerodynamics. . .

So far the aerospace industry's solution to high speed, vertical flight has been the hugely complex tiltrotor, a hybrid airplane with rotors. The X2 differs markedly in that it is still a helicopter that can go fast, autorotate, hover, and fly nap of the earth.

Link

Not in production yet, of course, but Sikorsky apparently thinks they can get it there.

Jack the R wrote:

Not in production yet, of course, but Sikorsky apparently thinks they can get it there.

Sure. But "not in production yet" are the keywords. Simply because they can't give any significant benefits comparing to the conventional single rotor designs to justify the cost of development and production. So it's just a sales pitch so far. I may change my mind when I see one of them in operation. But I doubt it will happen any soon. Keywords here are "not practical", "not needed".

Doubling the speed isn't a significant benefit?

Jack the R wrote:

Doubling the speed isn't a significant benefit?

No, I don't doubt it. But it's all trade off. One thing I know is that Sikorsky kept coming with similar ideas for the past 25 of years or so and none of them became a reality. So I have some other little doubts.

There are many factors involved. Cost of manufacturing, maintenance and operation, efficiency, range, just to name a few. If you want to bring workers to an oil rig some 100 miles off shore, or to fly Donald Trump from NYC to his casinos in Atlantic City, will the speed make a big difference? Overall in civilian applications current designs do the job just fine.

Speed will make a huge difference in medivac, search and rescue, troop transport, as will the reduced rotor diameter. Those medivac helis have to land in the tightest spots . . .

Any place you would use a tilt rotor, you could use one of these instead. The X2 may be more complicated than a single rotor heli, but it's less complicated than a tilt rotor.

Jack the R wrote:

...
The X2 may be more complicated than a single rotor heli, but it's less complicated than a tilt rotor.

I would like to see one of them going into production. But all things considered, it's a long shot. They still won't be able to beat the sonic speed barrier on the advancing blades. Making shorter and wider blades will help, but by how much and at what cost?

Quote :

"This isn't an airplane we are training to hover. It's a helicopter that will go very, very fast," said Sikorsky CEO Jeff Pino. "I think it will get to 260 kts." (The helicopter world speed record is held by a Westland Lynx at 216.45 kts).

As long as they can keep the rotor tip speed below 460 mph, they should be fine. If I understand it right, in high speed mode the rotor can be slowed down since most of the thrust will come from the pusher prop and there's a stub wing making lift.

Jack the R wrote:

Quote :

"This isn't an airplane we are training to hover. It's a helicopter that will go very, very fast," said Sikorsky CEO Jeff Pino. "I think it will get to 260 kts." (The helicopter world speed record is held by a Westland Lynx at 216.45 kts).

As long as they can keep the rotor tip speed below 460 mph, they should be fine. If I understand it right, in high speed mode the rotor can be slowed down since most of the thrust will come from the pusher prop and there's a stub wing making lift.

It's all possible in theory. So good luck to them to make it a reality. I simply doubt they can. That's all.