Finalized landing skids with floats

 

I have finaly finished the most demanding part of the construction so far. The landing gear looks quite realistic. More details I will give later this week (no time now).

Landing gear: made from scratch.

 NEW UPDATES, SEE BELOW!

After more than 2 months of silence I come back with some news on this project. It took a lot of time to come up with a reliable solution for the skids of the helicopter.

The original legs and skids from Vario are just... wrong in terms of geometry (are you listening Vario developers?). My experienced friends at GAM Dizy told me that this is not the only Vario model that has this weakness. Nevertheless, the quality of the kits in general is quite good but there is always a lot of place for improvements, especially when it comes to the scale details and looks.

As you can see in the photos hereby the legs form a 60-degree angle with the horizontal plane when looking face-to-face the helicopter and also they form a 10-degree angle with the vertical direction towards the front when looking from the side.

The helicopter that I have to reproduce also has floats in lieu of normal skids that had to be done from scratch as the legs.



The legs are made of anodized aluminum tubes with 1.2cm external diameter and the floaters of 0.8mm-thick aluminum sheet. Bending, drilling and the final mounting of the tubes was difficult because it is difficult to bend the tubes to the desired angle without creating a notch. I have made a tube-bender from scratch using iron pulleys, a bending-spring and some other common hardware (I will cover that in another article).

Drilling of the holes for mounting the legs on the previously mounted wooden frame is done using a press drill machine using a 10cm-wide disc made of resin. A Tupperware cap has been used as a mold. A carpenter's laser pointer has been used in order to turn the legs to the right angle (10 degrees) for drilling. The disc has given increased precision in reading the angle due to the relatively large diameter. A 10-degree angle corresponds to approximately 1cm on the periphery of the disc that is easy to read with a good precision. If I had to do that on the outer surface of the tube than I would have to precisely read and mark a 1mm-distance - out of the question with only 0.5mm available precision!




The next step was to build the floats. Stereometry has also been needed here in order to calculate the points and directions of bending of the aluminum sheet. The foil has been cut using a common cutter and by taking advantage of the material fatigue after indenting 5-6 deep grooves into the sheet and then bending it back and forth it is cleaved exactly along the groove (see images).



Each float has two cuts, one at the front and another at the back. Those cuts have been soldered using Durafix rods and a torch. The important detail when using Durafix is to prepare well the surface by rubbing it with a steel brush to remove alumina (oxide) and then attach the parts to solder on a big ceramic plate or cement brick (as I did) with iron fasteners. This limits down to a minimum any thermal losses and you can solder within seconds even with a moderate single-gas torch.



The photos below show the almost final result. Still the attachments of the legs to the floats are not finished but you can get an idea of the geometry and the relatively good fit. Nevertheless, the radius of curvature of the legs is still not perfect as it should be around 7-8cm instead of 5cm (radius of the bending pulley). Maybe when I have more time I will correct that by building new legs but for the moment the geometry is acceptable and much better than the geometry of the kit's landing skids.



As you can tell from the photos above, the doors are already mounted. I have modified the Vario locking mechanisms and adapted them to the scale looks of the model as the door handles of the real helicopter are located at the center of the door. Here is a photo of the modification:



Also I have made quite some progress with the navigation lights. I have chosen the solution from Innoflyer and I am very glad for that. The quality of their products is very good, the intensity of their LEDs is blinding (really one has to pay attention not to look directly at them!) and the people running the company are very professional. I had the chance to get one of their prototypes before the official launch of the product. This LED is a CPL and has the ideal shape and dimensions for the tail position light (see image below). Many thanks to Mr. Christophe Raible from Innoflyer for letting me having this superb prototype for the needs of my model!



I am planning to start building the engine exhausts. I will use an expanded polystyrene model to build a mold and then laminate with carbon fibers as I have already done for the tail hub cover (see below).



That's all for the moment. I will post details on the dimensions of the landing gear, how to bend the tubes and the aluminum sheet a bit later this month along with other stuff while the project progresses.

Cheers!

UPDATE
As I said before the radius of curvature of the legs is not as long as it should for the scale. I decided to correct this.
 

I changed the wheel/pulley used for bending. Now the pulley that I used before for bending is used on the lever and it has been replaced by a wheel (red, see photos) with 9cm of radius. A draft for the new leg geometry is attached as pdf on the right-hand side of the blog (see links).

Aluminum tubes with thin sidewalls and especially when they are anodized are easy to crack under tensile stress, which renders bending a bit tricky. What is important is to use a spring for bending with an internal diameter exactly equal to the outer diameter of the tube to bend. The spring offers an excellent support for the sidewalls of the tube inhibiting as much as possible the distortion of the cross-section shape (from cricular to elliptical). I used it together with the bending machine that I made from scratch. The result is very satisfying and now I only have to repeat the drilling exercise as I described before. I hope that this week I will have the landing gear finished.
The second very important detail when bending tubes is to inhibit any sliding of the tube while bending. Otherwise the result will be at least not good and in the worst case you will end up with a notched tube instead of a bent one.

In one of the photos here you can see that I use two rings that are attached firmly at the back of the tube in order to avoid sliding while bending. It works very well and the plasticity is distributed over a long curve instead of a single point (notch). Nevertheless, due to this plasticity the anodized surface becomes slightly cracked due to the tensile strain on the outer side of the curve. This is visible to the naked eye as the color of the tube around that region becomes slightly lighter (from medium grey to light grey). Nothing so alarming as the tube cross-section remains almost the same (slide-stop rings can be pulled through the bend region almost without effort).
There is only one remaining obstacle: the linkage of the legs with the floats. This is still a small headache, I want to make it simple, light and, of course, reliable! I already have an idea how to do it and I will try it with my new CAD tool that I find excellent for amateur design work: TurboCAD. The license costs more or less the same money as a stupid Wiindows 8 copy but is millions of times more reliable and useful.
Parenthesis: I am a Mac user since the age of 15 - system 6.0.7 for those who know - and by definition not 100% objective, but, frankly, I have never seen a worse OS than Windows 8 since then; we should be paid for taking it off the shelves not paying for it!!!

I will  post some more on the landing gear and maybe the lighting system this week, or at least I hope I will find the time.

Cheers!

UPDATE 2

I have found some time to remake the landing gear legs  with the new tool and mount them on the heli.
Here are some photos. I still have to make the attachments to the skids (and I am still scratching my head how...).


Here are two photos (real and model) for comparison, it's not bad:

That's all for the moment.

Bye!