Seeing that the A-model gets all the love and the B-model almost none made me feel sad. The B-model is a great build. It's long and sleek which gives it a great sense of agility and speed. Plus the fact that the intermeshing rotors are really cool. Even my wife was impressed…

After seeing Jeroen Ottens post on his counter rotating rotor mechanism I started wondering if something similar could be done for the B-model. Since this is my 1st mod in over 20 year (that just made me feel ancient) there were lots of challenges to overcome. Like familiarising myself with the Technic pieces again and getting up to speed with current building techniques. Anyway long story short, I succeeded.

The coaxial rotor mod has the following features:

- PF powered functions (M motor)

- Coaxial rotors (with ratchet)

- Collective pitch on both rotors

- Bi-directional clutch to operate landing gear

- Clutch to start/stop rear propeller (with ratchet)

Things to do:

- post pictures of final test rig (v3) DONE

- integrate battery box into mod (nearly done)

- integrate mod into B-model

First attempt

Below you can see the 1st version of the test rig that demonstrates the main features. Sorry for the bad lightning.

I've also listed my learning points from this version.

Front and bottom beam setup are identical to B-model to ensure proper space restrictions.

1. Coaxial rotor mast
   
2. Landing gear clutch
   
3. Propeller clutch
   

1. All gear down at the start of the gear chain = BAD! (you think after reading all those truck trial threads I would've learned something… *slaps forehead*
   
2. Ratchet support is not strong enough at full speed. (See 1)
   
3. Toothed clutch gears are handy for compact rotation reversal but very rare.
   
4. Flimsy clutch lever mounts.
   
5. Gear box lacks rigidity.
   

The rotor mast uses 3 small turntables. Collective pitch will be operated from below.

I'll post update in the coming weeks. Comments are more then welcome.

EDIT: Added the pictures into the post.

Edited August 30, 201212 yr by Nvolar

That's pretty cool. I might have to try building my own helicopter design one day. I have several remote control helicopters that I could use to get ideas from.

Here are the pictures of the improved and final version of the test rig. All the planned features are now realized.

I've also made a small video of the coaxial rotors in action.

Test rig v3 with the rotor blades.

Close up of the gearbox. The motor is now more integrated.

Close up of the collective pitch control at the bottom of the rotor mast.

Thats pretty cool!

Here are the pictures of the improved and final version of the test rig. All the planned features are now realized.

I've also made a small video of the coaxial rotors in action.

Hi,

That's really cool! Great that you took up the challenge. I love the way you made your collective pitch control. Very clever!

Meanwhile I have updated my mechanism to a much more reliable one (based on the 9396 mechanism), but this time with 4 blades per rotor and full pitch and collective control :)

I'm still not going to build it into a real helicopter because I have another project under way...

Leg godt,

Jeroen