Its because of the way the two side arms (the ones that dont move) fit with the rest of the frame.

The motors and props make a lot of vibrations and the flight controller does not like this.

The flight controller has a number of sensors that are vibration sensitive.

So if you want your multirotor to fly smoothly and loiter accurately you need to get those vibrations down.

The problem is that the flight controller sensors need to be firmly attached to the multirotor to sense the movements.

So you have a problem, you need to dampen the vibrations from the motors yet you dont want the sensors to get too isolated, using too soft a spongy foamgel, from what the frame is doing.

They isolate the motor vibrations from the arm by adding a little rubber bumper between a motor plate and the motor mount.

Vibrations on an APM flight controller are considered acceptable if you can reduce the x-axis and y-axis vibrations to below -3 units and keep the z-axs to -5 to -15 units.

I ended up using the RCTimer anti-vibration flight controller mount to get my vibrations down to the maximum.

These are really low vibrations and definitely help the quad fly better.

I have no way of comparing them to the plastic motor mounts but the plastic seem able to take more punishment.

The metal anti-vibration mounts are expensive compared to the plastic ones.

The TL68B33 dont grip the 16mm arms as tightly as the plastic Tarot mounts.

However i ended up buying another set of plates and made the rig 3 stacks and that gave me ample mounting space.

And on 2x4s 5000mAh batteries and a GoPro, flight times over 20min have been achieved.

I did some research and found that its recommended for 2:1 thrust for weight.

I was looking at the SunnySky v3508 380kv motors on 4s with 123.8 props.

The motor is specced with different thrust levels throughout the power band, Im a little confused as to which thrust I use to calculate for the 2:1 I can already see that my 3700g AUW is too much.

Shorten the shaft, and replace with quality bearings when needed.

I use them on my PRO and they are fantastic, maybe Im the only guy here flying 3s or maybe its just that you guys have more money to burn than I do.

You may get away with a 4S, especially if you dont run the throttle up all the way.

With a 4s the 115 would probably work but would be a bit large in my experience.

Im running a quad with 3s 2700mah battery and 104.5 gemfan props.

Its a pretty good combination.

This motor is designed for airplanes and it is a poor pair for multi-rotors.

Tarot Ironman 650 Manual Pdf