5
$\begingroup$

I am trying to find out how a helicopter rotor's lift is transferred to the chassis. Equivalently, how is the weight of the helicopter transferred to the rotor blades?

While looking for this online, I find a whole array of pictures of the drivetrain. The force enters the main gearbox (MGB), but leaves the MGB with a spinning axle going to the rotor. First I thought that something happens in the swashplate, but that is not well designed for bearing large amounts of force. So my thought is that somewhere in the MGB there is a nice piece of a bearing.

There is a question like this one for airplane propellers: How does the load transfer from a prop to the airframe? The bearings shown there cannot be found in the MGB of a helicopter (or, at least, I could not find them). It seems to me that a helicopter is hanging from its MGB. Can someone help me out? Pictures would be really appreciated.

$\endgroup$

3 Answers 3

5
$\begingroup$

The load path is rotor blade to hub, to mast, to mast bearing set inside transmission, to transmission housing, to transmission mounts/struts, to airframe.

enter image description here

$\endgroup$
1
  • $\begingroup$ You might want to add the "Jesus" nut. Called this because if it fails, all the occupants are left to say is "Jesus". $\endgroup$ Sep 28, 2019 at 9:23
4
$\begingroup$

EDIT: it is the main gearbox of an H145 aka EC145 aka BK117


I might have found the right picture:

H145 main gearbox

This cutaway displays the main gearbox of a H145 and nicely depicts all the bearings (in light blue) which are found in a typical helicopter gearbox. The one of interest is the one I circled in red: it is a double-row spherical roller bearing.

This particular type of bearing is typically used for rotating shafts. It tolerates slightly misalignment between shaft and bore and it can transfer high radial and axial loads. Just perfect for a helicopter shaft!

The bearing transfers the load from the shaft to the outer case of the gearbox (in green) which is in turn connected to the fuselage via the v-shaped beams (in yellow).

$\endgroup$
2
$\begingroup$

The force is transmitted through the mast bearing. Gearbox diagrams often omit that because they're already so complicated.

$\endgroup$

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.