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

Peter Voogt · Mar 30, 2025

RDN1954 said:
After having installed the collective controls and closed the torsion box, I changed my focus to the cockpit floor and the tail rotor controls. The four rudder pedals protrude through the floor and connect to two parallel shafts. On each shaft a lever is present, to which a control rod is attached. This control rod is then attached to another lever system in the main mast.

The cockpit floor is made from Evergreen ribbed sheet. It's left over material from my Fokker Spin build, which is now being put to good use. The forward edge of the floor is reinforced with a brass u-section; the Evergreen sheet is rather flimsy, when unsupported. Below a picture of the raw cut floor with the cut-outs for the rudder pedals:

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In order to have a robust support for the two pedal shafts, I crafted a block with two dia 1.6mm holes, 2.5mm apart.
The two pictures below show this block with one of the shafts installed:

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The next picture shows the helicopter's fuselage with one of the shafts installed and in front of the helicopter the second shaft and two of the four pedals:
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First dry fit of the floor and the rudder/tail rotor control system:
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Fast forward a day and the second set of pedals have been made and the RH control rod. It's all a temporary fit, still a lot of work is needed to tidy it all up.
One of the issues I'm now encountering is to find the proper build sequence. Since a lot of parts need to share the same space, it's unavoidable to encounter sequence issues, for instance the fwd tank attachments occupy the fwd traverse landing gear spar. The floor with the rudder controls sit directly above the fwd spar. Installing the floor first results in limited access to the tank installation and vice versa. I guess I need a night's sleep over it...
Another emerging issue was that I added some external details to the torsion box, based on the isometric sketches I have, but those details were heavily interfering with the cockpit floor.

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Very delicate and nicely scaled parts, Johan. And the sequence of installation can give you a headache. But hopefully no sleepless nights.
I can almost she her turning left and right with those pedals.
Regards, Peter

dockattner · Mar 30, 2025

Nice preservation of scale, Johan. Fiddly...

Daniel20 · Mar 30, 2025

RDN1954 said:
One of the issues I'm now encountering is to find the proper build sequence.

I know you will ultimately figure the sequence out. In the meantime, those floor pedals look great.

Pathfinder65 · Mar 30, 2025

Those pedals are a precise engineering feat. Nicely done.

Jan

RDN1954 · Tuesday at 12:24 PM

The above picture shows the main parts of the tail rotor control system. Not all parts are shown, but it gives you an idea about the complexity.
Clearly identifiable are the four pedal assemblies. There are two different assemblies, the RH and LH set of rudder pedals.
Then there are the two similar shaft assemblies with the control rods, which will drive the lever assembly, shown top center. This last assembly converts the fore and aft control inputs in the horizontal plane into an up- and down movement along the axis of the main mast.
You're looking at some 30 parts, pins, bolts and nuts excluded and I still need to fabricate a few parts...
I also use pin/hole connections to positively locate parts.
(The floor panel, center bottom, is shown for reference.)

One of the things worrying me right now is the possibility I might accumulate too much play, causing the whole thing not to work.
In real life this system would be loaded with bushes, bearings, washers, retaining rings, bolts, nuts, etc.
For modeling purposes it's essential to reduce parts count, or simplify the system, otherwise I would seriously damage the scale ratios.

To emphasize again, an awful lot of details are AL-FI, there's now way I can be absolutely certain about quite a few design details , but this build is turning out to be very demanding and very interesting.

RDN1954 · Tuesday at 1:02 PM

Peter Voogt said:
Very delicate and nicely scaled parts, Johan. And the sequence of installation can give you a headache. But hopefully no sleepless nights.
I can almost she her turning left and right with those pedals.
Regards, Peter

dockattner said:
Nice preservation of scale, Johan. Fiddly...

Daniel20 said:
I know you will ultimately figure the sequence out. In the meantime, those floor pedals look great.

Pathfinder65 said:
Those pedals are a precise engineering feat. Nicely done.

Jan

Can't say I have sleepless nights over this build, other than contemplating the next steps and how to proceed.
To stay true to scale is a major concern, selecting the wrong dimensions for parts may ruin the look I am after. This is not new; I had similar concerns with my Bluenose build, where I wanted to make sure the selected dimensions of amongst others blocks and ropes emphasized the true size of the Bluenose and not make it look smaller than she was.
It are pictures like the one below I use to fabricate the parts from, as you can see it's a lot of AL-FI...

GrantTyler · Wednesday at 9:08 AM

RDN1954 said:
View attachment 511067
The above picture shows the main parts of the tail rotor control system. Not all parts are shown, but it gives you an idea about the complexity.
Clearly identifiable are the four pedal assemblies. There are two different assemblies, the RH and LH set of rudder pedals.
Then there are the two similar shaft assemblies with the control rods, which will drive the lever assembly, shown top center. This last assembly converts the fore and aft control inputs in the horizontal plane into an up- and down movement along the axis of the main mast.
You're looking at some 30 parts, pins, bolts and nuts excluded and I still need to fabricate a few parts...
I also use pin/hole connections to positively locate parts.
(The floor panel, center bottom, is shown for reference.)

One of the things worrying me right now is the possibility I might accumulate too much play, causing the whole thing not to work.
In real life this system would be loaded with bushes, bearings, washers, retaining rings, bolts, nuts, etc.
For modeling purposes it's essential to reduce parts count, or simplify the system, otherwise I would seriously damage the scale ratios.

To emphasize again, an awful lot of details are AL-FI, there's now way I can be absolutely certain about quite a few design details , but this build is turning out to be very demanding and very interesting.

Good afternoon Johan. A very interesting build although something I would not attempt to do. I can see why this is a demanding build but that is how we all like it. If it was easy we wouldn’t be doing it - right? From my layperson point of view you are certainly on top of this. Enjoy. Cheers Grant

Marquinius · Wednesday at 9:27 AM

Really nice to see this "bird" taking shape. Intricate work, but well worth it. Hat off!

RDN1954 · Wednesday at 9:46 AM

GrantTyler said:
Good afternoon Johan. A very interesting build although something I would not attempt to do. I can see why this is a demanding build but that is how we all like it. If it was easy we wouldn’t be doing it - right? From my layperson point of view you are certainly on top of this. Enjoy. Cheers Grant

Marquinius said:
Really nice to see this "bird" taking shape. Intricate work, but well worth it. Hat off!

What can I say; despite everything I wrote to the contrary, I do like the challenge.
(And if they could build this 70 years ago in 1:1, I most definitely can build it in 1:24... )