Technote: Inventor Sketch Blocks
I have uploaded a video showing the mechanism for the Main Landing Gear for the Lockheed P-38 Lightning. This was created using the Inventor Sketch block feature which is a great tool to understand how these mechanisms work and provides an opportunity to examine the operational relationships.
Landing Gear mechanisms are quite complex and at first glance at the drawings, it can be difficult to fathom how they actually work. One way of visualising this mechanism and understanding the extent of the operation is to use Sketch Blocks.
The way this works is that you first build your sketch; minimise constraints, and select the elements that form each of the components; whether that be hydraulic cylinders, linkages, axles etc. Then you would constrain them according to how the mechanism should work…in this example, the cylinder actuator rod is constrained to align with the centre of the cylinder and virtually everything else is concentric constraints at each of the nodes. There are a number of good Youtube videos that show how this is done.
The dimension shown is a “driven” dimension which will change according to the location of the operation. You could of course have driven dimensions for the angles to check the max and minimum inclination. The quality of the video is not great but you get the idea.
Video link: P-38 Main Landing Gear Operation
For better precision, it is always best to use the Simulation environment with relative constraints applied accordingly to confirm operational parameters but for a quick check on movement, the Sketch Block feature is a good solution prior to committing to modelling.
Update 16th June 2022 LG Hinges:
Have you ever wondered what the Main Landing Gear Door Hinges look like?…
Aviation CAD TechNotes 