NHI Kolibri N-3, scale 1:48, scratch build

[RDN1954]

Modeling wise, I think I'm at the pivot point of the build; I now have to turn my attention towards the rotorhead and since I determined that I wanted to have functional flight controls, I manoeuvred myself in a tight corner.
Basically all manoeuvrability and speed stems from the changing the (differential) pitch of the rotor blades (apart from the tail rotor, which controls the torsion around the vertical axis) and is accomplished through a complex system of linkages, connected to the collective pitch control lever and the cyclic controls, co trolled by the pilot. This all comes together in the rotorhead with shafts, both plane- and roller bearings, linkages, seas, fuel lines, ignition harnesses, main rotor axle, gears for the tail rotor drive, just to name a few of the components. Since the available space is quite limited, it's quite impossible to replicate all parts in scale 1:24. This means I have to make a simplified design for the rotor head and that's what I'm currently working on, without tangible results yet.
To give you an idea of the complexity of the rotorhead, the drawing below, which I was fortunate enough to obtain at the NLR, shows the details:



At the moment I'm considering a main shaft diameter of 3mm and a collective control shaft of 2mm, which leaves me with a 1 mm diameter free opening for fuel and ignition lines/harnesses. The first task I picked up was the simplified design of the controls for the collective pitch. It took me a couple of hours, but I still need to also determine the details for the other cyclic controls, before being able to start work on a physical model. And that's just one of the many challenges I'm facing. TBC.

 

[Daniel20]

What a daunting challenge Johan. I am looking forward to your solutions.

 

[GrantTyler]

Modeling wise, I think I'm at the pivot point of the build; I now have to turn my attention towards the rotorhead and since I determined that I wanted to have functional flight controls, I manoeuvred myself in a tight corner.
Basically all manoeuvrability and speed stems from the changing the (differential) pitch of the rotor blades (apart from the tail rotor, which controls the torsion around the vertical axis) and is accomplished through a complex system of linkages, connected to the collective pitch control lever and the cyclic controls, co trolled by the pilot. This all comes together in the rotorhead with shafts, both plane- and roller bearings, linkages, seas, fuel lines, ignition harnesses, main rotor axle, gears for the tail rotor drive, just to name a few of the components. Since the available space is quite limited, it's quite impossible to replicate all parts in scale 1:24. This means I have to make a simplified design for the rotor head and that's what I'm currently working on, without tangible results yet.
To give you an idea of the complexity of the rotorhead, the drawing below, which I was fortunate enough to obtain at the NLR, shows the details:

View attachment 535474

At the moment I'm considering a main shaft diameter of 3mm and a collective control shaft of 2mm, which leaves me with a 1 mm diameter free opening for fuel and ignition lines/harnesses. The first task I picked up was the simplified design of the controls for the collective pitch. It took me a couple of hours, but I still need to also determine the details for the other cyclic controls, before being able to start work on a physical model. And that's just one of the many challenges I'm facing. TBC.

Good afternoon Johan. Whew way above my pay grade. Looking forward to seeing how you achieve this.. Cheers Grant

 

[Peter Voogt]

Modeling wise, I think I'm at the pivot point of the build; I now have to turn my attention towards the rotorhead and since I determined that I wanted to have functional flight controls, I manoeuvred myself in a tight corner.
Basically all manoeuvrability and speed stems from the changing the (differential) pitch of the rotor blades (apart from the tail rotor, which controls the torsion around the vertical axis) and is accomplished through a complex system of linkages, connected to the collective pitch control lever and the cyclic controls, co trolled by the pilot. This all comes together in the rotorhead with shafts, both plane- and roller bearings, linkages, seas, fuel lines, ignition harnesses, main rotor axle, gears for the tail rotor drive, just to name a few of the components. Since the available space is quite limited, it's quite impossible to replicate all parts in scale 1:24. This means I have to make a simplified design for the rotor head and that's what I'm currently working on, without tangible results yet.
To give you an idea of the complexity of the rotorhead, the drawing below, which I was fortunate enough to obtain at the NLR, shows the details:

View attachment 535474

At the moment I'm considering a main shaft diameter of 3mm and a collective control shaft of 2mm, which leaves me with a 1 mm diameter free opening for fuel and ignition lines/harnesses. The first task I picked up was the simplified design of the controls for the collective pitch. It took me a couple of hours, but I still need to also determine the details for the other cyclic controls, before being able to start work on a physical model. And that's just one of the many challenges I'm facing. TBC.

This will be a great challenge, Johan. Indeed what you wrote, you have to simplify this technical part.
Regards, Peter

 

[Marquinius]

Modeling wise, I think I'm at the pivot point of the build; I now have to turn my attention towards the rotorhead and since I determined that I wanted to have functional flight controls, I manoeuvred myself in a tight corner.
Basically all manoeuvrability and speed stems from the changing the (differential) pitch of the rotor blades (apart from the tail rotor, which controls the torsion around the vertical axis) and is accomplished through a complex system of linkages, connected to the collective pitch control lever and the cyclic controls, co trolled by the pilot. This all comes together in the rotorhead with shafts, both plane- and roller bearings, linkages, seas, fuel lines, ignition harnesses, main rotor axle, gears for the tail rotor drive, just to name a few of the components. Since the available space is quite limited, it's quite impossible to replicate all parts in scale 1:24. This means I have to make a simplified design for the rotor head and that's what I'm currently working on, without tangible results yet.
To give you an idea of the complexity of the rotorhead, the drawing below, which I was fortunate enough to obtain at the NLR, shows the details:

View attachment 535474

At the moment I'm considering a main shaft diameter of 3mm and a collective control shaft of 2mm, which leaves me with a 1 mm diameter free opening for fuel and ignition lines/harnesses. The first task I picked up was the simplified design of the controls for the collective pitch. It took me a couple of hours, but I still need to also determine the details for the other cyclic controls, before being able to start work on a physical model. And that's just one of the many challenges I'm facing. TBC.

Apart from the staggering detail you are putting in your model, you are adding true complexity. Your 3 mm and 2 mm are extremely thin to accomplish any strength and sturdiness. And although you calculate having 1 mm space left, that probably will be split in two, if not four. Would photo etch or laser cutting be of help? Just thinking out loud.

Whatever: hat off.

 

[RDN1954]

What a daunting challenge Johan. I am looking forward to your solutions.

So am I, Dan, so am I...

Good afternoon Johan. Whew way above my pay grade. Looking forward to seeing how you achieve this.. Cheers Grant

Actually, it's above my pay grade as well...

This will be a great challenge, Johan. Indeed what you wrote, you have to simplify this technical part.
Regards, Peter

Simplification is the keyword here, it's impossible to replicate all details in 1:24.

Apart from the staggering detail you are putting in your model, you are adding true complexity. Your 3 mm and 2 mm are extremely thin to accomplish any strength and sturdiness. And although you calculate having 1 mm space left, that probably will be split in two, if not four. Would photo etch or laser cutting be of help? Just thinking out loud.

Whatever: hat off.

As a matter of fact the 2mm and 3mm axes don't need to take any large loads; it will just be the loads from using the flight controls and resistance in the total system. The 1mm space should be enough for feed through of some small dia wire, but you're right, it's definitely not much room to play with.
I haven't thought about the options you mention; instead I considered 3D printing, however, I convinced myself to forego on the new available technologies and instead try to accomplish this build the hard way...


In the mean time I started parts manufacturing, based on some sketches I made.
Below a picture of some parts for the rotorhead assembly:
- on top you'll find the housing of the gearbox, dia 8mm.
- next to it is the stationary part of the collective pitch adjustment, dia 2mm.
- below that part the main shaft in which the main axis rotates, this part is also considered to be a plain bearing for the main axis.
- the 3mm main axis is next and right below the main shaft.
- the 2mm rotating axis for the collective pitch adjustment. This axis has two slots through which a pin will connect the two axis together to ensure the two axes rotate at the same rpm and simultaneously allowing the inner axis to move up and down in the 3mm axis. Still with me?
- the bottom part is the part forming a) the cover of the gearbox and b) the connection to the main mast.

Next time I'll add some pictures of the sketches I made.

 

[Peter Voogt]

So am I, Dan, so am I...


Actually, it's above my pay grade as well...


Simplification is the keyword here, it's impossible to replicate all details in 1:24.



As a matter of fact the 2mm and 3mm axes don't need to take any large loads; it will just be the loads from using the flight controls and resistance in the total system. The 1mm space should be enough for feed through of some small dia wire, but you're right, it's definitely not much room to play with.
I haven't thought about the options you mention; instead I considered 3D printing, however, I convinced myself to forego on the new available technologies and instead try to accomplish this build the hard way...


In the mean time I started parts manufacturing, based on some sketches I made.
Below a picture of some parts for the rotorhead assembly:
- on top you'll find the housing of the gearbox, dia 8mm.
- next to it is the stationary part of the collective pitch adjustment, dia 2mm.
- below that part the main shaft in which the main axis rotates, this part is also considered to be a plain bearing for the main axis.
- the 3mm main axis is next and right below the main shaft.
- the 2mm rotating axis for the collective pitch adjustment. This axis has two slots through which a pin will connect the two axis together to ensure the two axes rotate at the same rpm and simultaneously allowing the inner axis to move up and down in the 3mm axis. Still with me?
- the bottom part is the part forming a) the cover of the gearbox and b) the connection to the main mast.

Next time I'll add some pictures of the sketches I made.


View attachment 536046

I can see that you have made your plan, Johan. The start of this new charter is there! Looking forward to see your sketches.
Regards, Peter

 

[Marquinius]

So am I, Dan, so am I...


Actually, it's above my pay grade as well...


Simplification is the keyword here, it's impossible to replicate all details in 1:24.



As a matter of fact the 2mm and 3mm axes don't need to take any large loads; it will just be the loads from using the flight controls and resistance in the total system. The 1mm space should be enough for feed through of some small dia wire, but you're right, it's definitely not much room to play with.
I haven't thought about the options you mention; instead I considered 3D printing, however, I convinced myself to forego on the new available technologies and instead try to accomplish this build the hard way...


In the mean time I started parts manufacturing, based on some sketches I made.
Below a picture of some parts for the rotorhead assembly:
- on top you'll find the housing of the gearbox, dia 8mm.
- next to it is the stationary part of the collective pitch adjustment, dia 2mm.
- below that part the main shaft in which the main axis rotates, this part is also considered to be a plain bearing for the main axis.
- the 3mm main axis is next and right below the main shaft.
- the 2mm rotating axis for the collective pitch adjustment. This axis has two slots through which a pin will connect the two axis together to ensure the two axes rotate at the same rpm and simultaneously allowing the inner axis to move up and down in the 3mm axis. Still with me?
- the bottom part is the part forming a) the cover of the gearbox and b) the connection to the main mast.

Next time I'll add some pictures of the sketches I made.


View attachment 536046

Hemeltjelief!

 

[Peter Voogt]

This morning I had the opportunity to see the current ‘state of the art’ in real life! The technical construction is even more impressive than the photos here on the forum show. And it's functional!
Many challenges remain, Johan. But the solutions will certainly come.
Regards, Peter