Static Mechanics: Aircraft Nosewheel Linkage Torque

  • Thread starter Thread starter jojosg
  • Start date Start date
Join the discussion
Registration is free. Ask a follow-up in this thread, or start your own.
Sign up Log in
4 replies · 3K views · last reply
jojosg
Messages
37
Reaction score
5
Homework Statement
Hi I'm stuck at how to draw the free body diagram for thise nose wheel question
Relevant Equations
Moment equal 0
see attached

Textbook problem 4/131 with the statement that a torque M lifts a nose-wheel assembly through link BC, with a diagram of the linkage: points A, B, C, D, O and G, lengths 400 mm, 500 mm, 800 mm and 200 mm, and angle theta at D.


Handwritten engineering solution on ruled paper: problem statement at top, weight calculation W = mg = (50 kg)(9.8 m/s^2) = 490.5 N, a diagram of the nose-wheel linkage with bars BC and AO and wheel, and free-body diagrams of AO and BC with moment equation sum of M_A = 0.
 
Last edited by a moderator:
Physics news on Phys.org

Discussion

A free body diagram shows the forces on a single rigid body. Here you have a linkage, so you need an FBD for each moving part. This will involve defining unknowns for forces and torques between connected bodies, each such force being represented in the FBDs for both bodies.
What are the moving rigid bodies in this problem? Pick one and list the forces on it. Then post your attempt at its FBD.
 
I think it is safe to assume that links BC and CD are massless because no masses are given for them. Assume that the torque at M gives rise to a force ##F_D## at D that is just right to prevent the combined (arm + wheel) assembly AO from rotating either clockwise or counterclockwise.
 
Consider the external force and moment acting on the whole mechanism first.
One is the represented M, which is necessary to raise the combined mass of 50 kg, which can be represented as a vertical force applied at point G.

Note that the value of that vertical force will be constant, while the value of the necessary moment M will change as the wheel is being raised, reason for which the problem asks for the value of moment M at that specific position of the mechanism's stroke.

Please, see this example:
https://www.school-mechademic.com/blog/static-force-analysis-on-a-4-bar-link-mechanism

:cool:
 
Last edited:
ok I think I got it thanks everyone
 
Attachments
  • Handwritten physics solution on lined paper with a diagram of a nose-wheel linkage: arm AO with wheel W, link BC, torque M, dimensions 400mm, 800mm, 500mm and 250mm, and free-body diagrams for AO and BC with weight W = mg = 490.5 N and angle θ = 30°.
    IMG_20251020_190101.webp
    30.5 KB · Views: 57
  • Handwritten free-body diagrams and moment equations on lined paper: FBD for AO with forces Ax, Ay, FCD, W and a 60 degree angle, and FBD for BC with Bx, By, M, FCD and a 60 degree angle, with moment sum equations and a result of M = 153.3 N·m.
    IMG_20251020_190106.webp
    30.8 KB · Views: 61

Similar threads

Static mechanics problem with inclined plane and forces
  • bostonfenway
  • · Replies 7 ·
  • Introductory Physics Homework Help
Replies
7
Static Force Analysis of Linkage
  • BatsDude
  • · Replies 10 ·
  • Mechanical Engineering
Replies
10