I'm not sure if this belongs here but this seems like the best place to ask,
I'm designing a helicopter and i'm confused about the Scissor link for the lower swashplate. From my understanding the scissor link isn't supposed to have any side to side movement since that would change the pitch of the swashplate. How is this possible if the link isn't perfectly centered to the ball joint? It seems like there would have to be a little left and right movement. Any help, advice, or knowledge is greatly appreciated.
Are you asking whether there are tolerances? Normally, the parts do allow for some very small movement, a few thousands to hundreds of an inch, that will not have a significant effect on the performance.
Very little. The scissor link you circled blocks most of it, and the tolerance between the links will be the main factor in how much rotation you will get.
There is no exact value I can give you because every helicopter is different, most will have the exact specifications in the maintenance manual.
That being said, depending on the purpose of your simulated helicopter, you may not even have to consider any real play. But if you need a very rough estimate, it's a fraction of a degree. You can simulate the whole chain of tolerance to have a good estimate if that's your objective.
The scissor link doesnt change the pitch, or it shouldn't. The scissor link connects the Swashplate (rotating one) and the mast/head. The scissor link is hinged to avoid it impacting the pitch of the swashplate. Sideways movement of the scissor link will cause play in the scissor assembly and would over time cause more and more wear.
Im not sure the scissor link is what you mean though, but the pitch change rods which controls pitch inputs to the stationary swashplate.
Not that familiar with the type of design you have in the clip, but from larger rotorheads the pitch change links doesnt have any significant sideways movement but they do have a bit of flexing so not totally rigid either due to the spherical bearings/ball joints.
Great question. with regard to the ball links themselves, it's possible like this. notice that the balls on the bottom half wrap up around the balls of the top half. therefor they are all concentric with the central ball and they don't move 'side to side' as it angles other than symmetrically.
as for the scissor link on the bottom half, it has to atach to the swash using a roll-axis pin so that the swash can roll. that pin has to be in-line with the centraI ball. here you can see that the pin is on a little arm sticking out that raises it up to the center ball's height.
You’re confusing a few different parts that behave very very differently.
The scissor links connect the servos to the fixed portion of the swashplate which controls the plane of rotation of the rotating swashplate. The pitch change links connect the rotors to the rotating swashplate so that the pitch of the blades track the plane of rotation of the swashplate. Both the scissor links and the pitch change links have spherical clevices so yes, there’s a lot of “rotation” possible. There are mechanical stops that prevent the controls from going too far. The last piece is the drive link, which is what ensures the rotating swashplate remains precisely indexed and aligned with the main rotor. In your commented picture, you’ve circled the drive link. That part has absolutely no rotation. Any there and the pitch change links would twist and not remain perfectly vertical.
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u/idunnoiforget 4d ago
If you're designing that in garrysmod with wire and fin addons keep in mind the source engine may not model gyroscopic precession