The cheapest way to build RC helicopters from scratch is to buy a “partly completed” kit. This contains the body frame, canopy, fuselage and blades, and quite often the swashplate and motor as well. You buy the rest of the components to suit your pocket and needs.
Once the swashplate and motor have been fitted, it’s time to install the main servos. These must be centred, attached to the ball links and securely screwed into place.
When upgrading electric helicopters, it’s important your new components are compatible with the RC heli you are building. Hobby grade RC helicopters often have interchangeable components; their manuals will have a list of compatible brands, with the appropriate settings for each.
This can include different types of linkage. For example, for the Futaba servo, Raptor RC helicopters have a recommended distance of 10.5mm from the linkage balls to the servo arm. But for owners fitting the cheaper star-shaped servo horn, it is stated as being the second hole position.
There is a fair bit of lee-way allowed when building electric helicopters, so long as everything ends up balanced. Builders often struggle when attempting to centre the servo horn onto the output shaft splines, because they feel they have to follow the manufacturer’s exact instructions. However, it is better – and easier – to experiment fitting the arm in various positions, and get the best geometric accuracy that way.
When mounting servos to electric helicopters, there is normally a brass bush, with a flange that passes through a rubber grommet. This flange should rest against the helicopter frame, not the servo fixing screw. A lot of the “art” to building RC helicopters is ensuring the parts you are fitting are easy to get to when they need adjustment or replacing.