Ka 50 Gearbox Setup

[bradmick]

So, here's a question. I've been thinking alot about how in the world the Ka 50 transfers its power to two counter rotating rotor heads from one gearbox. Anyone know of any pictures of the gearing setup? Or do you eagle dynamics folks by chance have some pictures of the gearbox gearing to post? My guess is there are the two central driver gears in the gear box which connect to the intermediate gearboxes, they are geared a certain way so that a top mounted rotational gear rotates clockwise, and a bottom mounted rotational gear rotates counter clockwise. The thing I can't get my head around, is what the gears would look like, and the tooth setup of the rotor rotational plates.

 

Anyway, thoughts? Ideas? Pictures?

 

Brad

[GreyStork]

I don't know if you can picture this, but if you have two 45 degree cone stub gears facing each other and a fixed 45 degree peripheral gear engaging both, that would make the first two gears counter-rotating. Add a few more peripheral gears for mechanical strength.

[RvETito]

I can post the picture you want but unfortunately not sooner than next thursday, I'm away for the holidays. The Ka-50 is a unique solution among the other Kamov helicopters- look here. The designers have decided to put the rotor axis between the engines which leads to a more complicated gearbox system- two intermediate GBs with free-wheel drives (clutches) connected with driveshafts to the main GB VR-80. The last is pretty much common to the VR-252(the most popular GB for Kamov helicopters- Ka-27/29/31/32) when it comes to gears. The two rotor driveshafts are driven by the last (3rd) stage of reduction- the satelite gear. It's hard to explain it without a picture (cinematic scheme) so I won't write now just some alien descriptions :D

[GreyStork]

This is how I imagined the main gearbox would work. However, according to Kamov's own schematics, it seems the counter rotation gear assembly is situated on the lower rotor shaft, although I can't quite see how this contraption would connect to the upper rotor shaft, as it's situated below the lower rotor itself.

[bradmick]

I can post the picture you want but unfortunately not sooner than next thursday, I'm away for the holidays. The Ka-50 is a unique solution among the other Kamov helicopters- look here. The designers have decided to put the rotor axis between the engines which leads to a more complicated gearbox system- two intermediate GBs with free-wheel drives (clutches) connected with driveshafts to the main GB VR-80. The last is pretty much common to the VR-252(the most popular GB for Kamov helicopters- Ka-27/29/31/32) when it comes to gears. The two rotor driveshafts are driven by the last (3rd) stage of reduction- the satelite gear. It's hard to explain it without a picture (cinematic scheme) so I won't write now just some alien descriptions :D

 

Awesome, that would be great! I ask because I want to try and build one for an RC model and not have to use two motors. The trick is finding a place that sells mini gears.

 

Brad

[4c Hajduk Veljko]

Awesome, that would be great! I ask because I want to try and build one for an RC model and not have to use two motors. The trick is finding a place that sells mini gears.

 

Brad

 

I wonder how many motors these little RC helicopters are ysing?

 

[GreyStork]

I ask because I want to try and build one for an RC model and not have to use two motors.

 

If you'd be interested in seeing a few examples of other people's coaxial RC helicopter projects, here's a couple of links:

 

http://www.cad-modelltechnik-jung.de/projekte/kamov_mechanik_turbine.htm

http://users.skynet.be/thididag/helicoax/

 

Of course, a much less expensive solution would be the Heli-Max EZ:

 

http://www.helimax-rc.com/helis/hmxe05-index.html

[GreyStork]

I wonder how many motors these little RC helicopters are ysing?

 

Since these micro helis don't use a three-axis swashplate design, they have to control collective and yaw by varying the RPM of the two rotors independently. Hence, they have to use two motors.

[bradmick]

Sweet! Yup, as Grey said, the majority of them have two motors connected to independent gears.

 

The one with the mini turbine engine is awesome, but i'm sure the same result can be achieved by using an electric motor.

 

Brad

[bradmick]

i'm pretty sure i just hit pay dirt!

 

http://home.cfl.rr.com/pwales/ka50.html

 

this is from that german kit, gives me a pretty solid idea of what it looks like inside.

 

Brad

[VS461]

Ka-50 gearbox

 

This is how I imagined the main gearbox would work. However, according to Kamov's own schematics, it seems the counter rotation gear assembly is situated on the lower rotor shaft, although I can't quite see how this contraption would connect to the upper rotor shaft, as it's situated below the lower rotor itself.

GreyStork, your imagination is correct. I think on the Kamov's picture there's sth missing on the lower part. There must be a same but mirrored wheel as the one for the lower rotor shaft. Maybe against spies...

As incoming torque, there must be a free-wheel sub-gearbox after the free turbine shafts of the TV3-117s, similar to Mil's VR-8/14/24 gearboxes. It doesn't allow the rotor to "backdrive" engine(s) after a flameout or during startup, and it equalizes small torque differences between the engines.

THX

[RvETito]

The free-wheel drives are 100% identical to the ones used in VR-14/24(Mi-14/17/24) gearboxes, it's a matter of engine(TV3-117) used rather than gearbox. I'll post a picture of the free-wheel drive as well- from the VR-252 gearbox(the same as in VR-14/24/80)

[RvETito]

Sorry, I forgot about it. :)

 

Here it comes- scheme of VR-252 gearbox (pretty much the same as the VR-80 when it comes to rotor driveshafts and last reduction stage gear).

[GreyStork]

Here it comes- scheme of VR-252 gearbox (pretty much the same as the VR-80 when it comes to rotor driveshafts and last reduction stage gear).

 

Apart from a few errors and omissions (for instance, the right secondary engine shaft appears connected directly to the chassis), it makes perfect sense. The counterrotation configuration isn't as I would have imagined it, but now the scematics on Kamov's site make a lot more sense.