Oxy 2 Sport
Instead of Lego

How to build a helicopter? Many of us know the basics at least, but what if a 9-year-old, who's a girl actually, wants to build the heli from this kit. Is it possible? Will it fly? This is what we have tried to do with Antonia and the Oxy 2 kit. Luca Invernizzi - owner and designer of this heli - has done a good job.

We have got an Oxy 2 kit from Hely-shop. I was going to build the helicopter, but Antonia fell in love with this little bird, and she "stole" it from me. This gave me the idea: if she wants to fly it, she has to assemble the kit. I'll help her, but I'm doing as much as absolutely necessary. And she agreed. We were sitting in the workshop room together evening by evening, and we made a little progress every evening. And finally the helicopter got assembled, then maidened.

The Oxy 2 is the smallest Oxy helicopter actually. Its size is the same as the good old T-Rex 250, the difference can be millimetres only. Basically the same category. Therefore I had some expectations about the challenge created by the size of the components, this is why I was happy to give the assembling to Antonia. My thick fingers just unable to deal with those tiny bolts. But still, this is a helicopter, it was interesting to see, how it will go by a 9-year-old girl.

Then the day of unboxing has arrived. We opened the "big" black box, which contained 3 smaller boxes. Each box contains little packages with clear labels. But the box has no manual. It has to be downloaded from the Lynx website. It's not small, but contains clear diagrams and instructions and it is as detailed as a Lego assembly instruction, which became obvious, as Antonia understood every step. I didn't have to help her to understand these steps. Therefore she just carried on with my assistance.

First part to assemble is the tail block and the tail boom. It's obvious, that tail is not going to break even in a smaller crash. It's so robust, that is incredible. And the purpose and design comes through each component. The smaller parts are factory assembled, although the manual describes how to put them together. At the beginning this caused a little confusion, because few other factories pre-assembled components just to help understanding how the final component will look, but they must be disassembled and rebuilt, otherwise they will fall apart in the mid-air. Well this is not required at Oxy 2 when the manual displays: "factory assembled", just leave it as it was.

And trust in the manual. The only point I disagreed was that when we had to put the tail and the main frame together without the tail belt, it was obvious that part has to come apart later again. And yes, this is in the manual. There are more points when I though "this is not gonna work, this is not possible". But later: voilá, it works. Typical example the landing skid. Many other models use a U shaped landing skid, but Oxy uses two plastic pieces which are held by the main-frame. They are not even held by crossing bolts, just the pressure of the side frames. That was the point, when I though: "I'm sorry, but this helicopter is a joke, what that skid can tolerate?" Surprisingly a lot. It was tested by accident. I will detail it soon.

We tried to cheat, and we put the landing skid up earlier than in the manual, because the main frame just overturned more times during the assembly process. I didn't understand why the complete rotorhead comes earlier than that skid. It just didn't make any sense to me, but later we have understood the reason. During the wiring procedure we get the gears off million times. The lesson: follow the manual, even you think, it just makes no sense.

Assembly video is coming soon...

Essential kit for Oxy 2

We have got the essential kit provided by Heli for the helicopter which was a really good idea, however the essential kit doesn't contain some essential accessories for the essential kit. This is the motor, which was clear to us, but we just realised, the Lynx servos have got JST connectors instead of the good old Futaba ones. There are three options:

A. replacing the connectors on the servos
B. choosing an FBL unit with those JST connectors (like MSH Micro Brain 2)
C. purchasing the converters which is a convenient solutions but they add plus 10 cm leads to the originally not too short leads.

Our Oxy has got a Microbeast FBL unit and a Futaba R6106FS micro heli receiver temporarily, but because this helicopter will be Toncsi's heli, it will be upgraded to VBar, therefore option B hasn't played at all. Option A got kicked out quickly as well as I hate to assemble those connectors, so option C won finally giving us servo leads going round and round.

However this kit contains all servos in the desired size (including the tail servo), and a Hobbywing Platinum V4 25A ESC. The only component missing from the package - in our case - was the motor. There are much fewer options than in bigger classes. We chose the Lynx EOX 1911 3600 KV motor from ATModels, which is designed to this helicopter, but the Scorpion HKII-2208-28 or the Align RCM-BL250MX motors can be options as well. It is true, the Lynx motor is about three times more expensive than the Align alternative and the Scorpion is way cheaper also than the motor we chose. But I am a lazy person, and this motor fits in this heli perfectly.

When the motor arrived, one problem arrived as well after the happiness. Not a big deal, but the motor connectors are different from the connectors of the ESC given with the essencial kit. So if you have no gold connector pairs, you will have to order again. Luckily I found couple of appropriate size connectors at home.

Tools

1.5 mm allen screwdriver is required. And the tools of the T-Rex 250 were useful as well. The allen screwdriver for the 250 was perfect for the bolts given with Oxy 2. Apart from these tools just usual stuff were needed, like pliers, digital pitch gauge.

However using thread locker is challenging. This is why we used one drop on a plastic instead of dropping to the bolt directly. Simple and easy trick which makes the process easier.

The Oxy 2 as a helicopter

This helicopter is ideal in this category. Durability and crash resistance is high. And yes, even a child can put it together - with a little guidance and assistance. The manual is well detailed and clear like a Lego manual. And as a helicopter flies perfectly - even with those suspicious plastic blades coming in the kit.

If you are experienced 250 pilot, you know that the autorotation capability of this small, lightweight class is close to zero, this is why Oxy 2 doesn't even pretend that it would be able to make it. No one way bearing. This caused a little surprise in the first tests, because I'm landing with motor switched off always, even with my 250, which is falling down almost from higher altitude. The Oxy 2 is falling down indeed as you switched the motor off. I pulled throttle hold on about 4 feet high, this is how we tested accidentally the durability of the landing skids I mentioned above. Nothing got damaged.

Then the helicopter got hooked up in the grass once, then overturned. Toncsi was quick, and switched the motor promptly. Nothing got damaged again.

All the gears running smoothly and quietly. And the heli is tolerating the wind pretty well. It is surprisingly powerful with the Lynx motor, however the default blades could be better. If you want to fly more than figure 8 and hovering, something better is well recommended.

The spare parts are not so pricey, and batteries are also not challenging as it flies with 3S1P 850mAh 20-30C batteries. It is a really budget friend model. There are no over-complicated solutions, everything is simple. Normal micro servos can fit in, although the Lynx essential kit contains the even smaller nano servos.

The only big issue is the quality of the screws. Unfortunately the screw of the main shaft collar broke in the collar at the beginning, so the helicopter wasn't done yet, when I had to order a replacement main shaft set for that tiny collar only. And it wasn't me, the head of the screw just came off in Toncsi's hand. Few others landed in the bin during the assembly, luckily the kit contains much more than required.