RC Helicopters

Helicopters are technical toys, and your first source of reference (before this piece of text, anyway) is the official documentation. You should systematically consult the official documentation before applying any tip you read, or watch, or hear from anybody. Don’t trust anyone, because people says whatever to look smart. This includes me, of course.

I’m writing here the documentation that applies with my own configuration. You may have a different set-up, most probably the transmitter and the FBL gyroscope and governor, because those two are not included in the T-Rex 300x Combo kit:

- The T-Rex 300x User Manual:

- The FBL gyroscope / governor user’s manual:

- The servo user’s manual:

- The ESC user’s manual

- The engine user’s manual:

Well, it shouldn’t be your first helicopter. It should be your third. Your first helicopter should be a simulator. There is no way around 20 or more hours to learn hovering at all angles, and some more to learn flying your eights. When you’re more or less able to avoid crashing your virtual helicopter, you can go to the next step. My advise here is buying your emitter, and a compatible USB receiver stick. That way you already get familiar with your emitter.

https://hobbyking.com/en_us/orange-rx-dsmx-dsm2-compatible-protocol-usb-dongle-flight-simulator.html

Your second helicopter should be a 3D micro-heli like for example the Blade CP S2. If you already have a RC emitter, you can buy a BNF (Bind N’Fly) version. These are full 3D helicopters, the size of your fist, and very resilient. Most crashes won’t break anything, particularly if you fly over grass and learn to switch the Hold before hitting the ground. Plus, as they are quite fast and susceptible to wind, you will develop nice reflexes that will spare you tears and money when you finally fly a bigger machine.

Then, your third could be a T-Rex 300x. Lots of people dislike it, saying it is too heavy for its size, too delicate, and it has a couple of shortcomings when setting it up. I believe it may be true, but it is also true that it is quite cheap to repair, it flies very smooth, and it is a full blown kit appropriate to learn all tricks in the trade, including sport and 3d flying.

To me, helicopters look like killing devices of destruction and death. A 450 size helicopter is able to severely disable a human. Probably you, if you spend enough time around it. So I chose the T-Rex 300x out of fear. I guess fear is a criteria as good as any other.

Hi all,

I've noticed that my Align T-Rex 300x has some play in the swash plate:

If I adjust the pitch to have 0º angle

Then I can move the blade to 1.3º just by slightly wiggling it, without any amount of force, and without the servo protesting.

See the photos below

This is my first normal size helicopter, so I don't know if this is normal:

Should I change the swash plate, or can I keep going?

Can I fly until I receive the new swash plate?

What is the normal / safe amount of play?

Also, if some play is acceptable, then should I take it into consideration when I level the swash plate? Like, I should measure the average angle between two extremities of the play (for example, 0º and 1.3º, the angle is 0.7º)?

Well, any hint will be helpful.

Have a nice weekend.

[EDIT]

The solution I’ve implemented so far is looking for a compromise where the servos are not very far from center, the servo links are within safe limits, and the swash plate is completely level: - Both aileron servo links: Fully screwed (no pun intended). - Elevator servo link: Fully screwed on both ends, and then unscrew 1 full turn the linkage rod. This is like unscrew 1x each ball link. -  Both DFC links (those attached to the rotor grip arms):  - Plastic ball link: fully screwed and CA glued.  - Metal-to-metal screw: unscrewed one full turn.

With this arrangement I managed to have: - Swash plate: leveled - Aileron servo arms: a tad lower than horizontal - Elevator servo arms: a tad higher than horizontal

When trimming the servos, I also achieved a “blue OK” light from the MicroBeastX, meaning that servo ranges are large enough.

Been flying 12 accumulators so far (a little above 1h), and this is my found no particular problem that I could relate to this issue: - The helicopter flies stable, - The only maneuver I dare to perform at full pitch is push ups and down, and the helicopter is stable also there. - But, when hovering, I can feel that it pull a little to the right and backwards.

I believe that the pulling is related to my lack of experience trimming the servos. I’ve ordered the official T-Rex 300x swash plate leveler to see if I can fix the pull.

Also, I feel that the elevator link rod is a bit on the scary side, so I’m not completely satisfied with the solution. I’m currently looking at other kits, see if I can find a suitable replacement part.

The T-Rex 300x has very little space in the canopy. If leads are too long, It’s going to be difficult to close the canopy. This is particularly true if you’re using a non official LiPo battery like the Tattu, which has a XT60 connector with AWG12 wires. Instead of preparing yourself and calm your mind, you’re going to struggle with the canopy while the wires are making all sorts of crazy loops in it’s belly.

To solve this problem, I cut the wires real short, and I let them go outside of the velcro loop. As they’re so short, there is no risk they bother the motor (being an outrunner, nothing should touch it)

Alternatively, there is this solution (look at minute 7:00)

The T-Rex 300x is sold without a power connector to the ESC (or at least some kits are sold without a connector). One of the first tasks of the new owner is to solder a power connector. What size to choose?

Initially I thought that it was better to install a XT30, because the 3s, 1300mAh, 30C LiPo battery officially sold for the T-Rex 300x has a XT30 connector. Logically, one should infer that official size for the power connector is XT30.

However, upon further investigation, I changed my mind. Maximum ratings of the XT30 connector are:

- 15A continuous current.

- 30A peak current (could not find how long can be the peaks)

- 500V maximum voltage

The corresponding ratings of the ESC that comes with the 300x, the RCE-BL25A are:

- 25A continuous current.

- 40A peak current.

- 11V to 22V (3s to 6s)

And the corresponding ratings of the brushless motor that comes with the 300x, the 300MX, are:

- 24A continuous current.

- 36A peak current (peak duration of 5 seconds)

- 3S (11V)

By comparison, I feel that the XT30 is a bit on the short side of the maximum current admitted by the ESC and the motor. I found out also other shortcomings of the XT30:

- Most 1300mAh, 3S, LiPo sold around have XT60 connectors. Actually, the official Align LiPo looks like the only battery of this size with XT30 connector.

- XT30 are also more difficult to find in my local shop.

That’s why, considering all of the above, I chose to go with XT60 connectors for my 300x

I’ve just bought a second hand T-Rex 300x and I am in the process of configuring it MicrobeastX Plus 5.1. I’m at the setup menu H, servo trim:

It says to “trim the servo center positions so that each servo horn forms an exact 90 degrees angle”

Then, in bold, it stresses that before going to the next step you have to “adjust the linkage rods according to your helicopter's manual, so the rotorhead system is set up neutral and allows to have equal movements in all directions”

My problem is that, if I follow the manual, the swash plate doesn’t look level by far. Actually, it looks so not level that I don’t think that the rods can be adjusted to absorb that amount of difference:

At first I thought that it was a problem in the helicopter. I bought it second hand, and even if the previous owner says he never flew it, I can’t be sure if he messed around with the rods or what. But then, looking at the manual, I am not so sure that it is a problem:

At page 15, user manual says that all three linkage rods should be approximately 12.5mm long.

I’ve measured mine, and they’re all quite exactly 12.5mm long.

Now, the elevator servo is at least 3mm lower than the two aileron servos.

Therefore, if I follow the manual then my swash plate is never going to be level with all three servos at 90º.

And I fear that if I unscrew the elevator rod to absorb all the difference, then the linkages are going to be weak and fall off.