7 votes

Magnetic Entrapped Storage at 0 gravity

Flywheels are used in space, but not for storage of energy. They are used for attitude adjustment, as the spinning of a large mass has significant implications in an object which is free to move. ...
Rory Alsop's user avatar
6 votes
Accepted

How does load force impact load inertia?

Let's first compute the model. The control design is a separate effort. The torque applied to the drum is $n T_M $, where n is the gear ratio and $T_M$ is the output produced by the motor. $T_M= K_T ...
Suba Thomas's user avatar
  • 1,971
5 votes
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How to simulate the Natural Frequencies of a Planetary Gearbox?

To obtain the modes shapes and resonant frequencies, you start from your equation of motion with no externally applied forces, which is indeed as you've stated. $$\mathbf M \mathbf{\ddot q} + \mathbf ...
Involute's user avatar
  • 1,337
5 votes

Which mode does get excited under action of dynamic loading?

Take the Fourier Transform of the time varying driving force, this will give the frequency content of the driving force. Multiple modes of vibration can be driven at once, and will superpose with each ...
Involute's user avatar
  • 1,337
5 votes

Understanding net torque from an actuator

There are two things going on. First, even if this "actuator" can produce constant torque, the torque required to keep the load spinning will be at least in part a function of the spinning speed. ...
Olin Lathrop's user avatar
  • 11.4k
5 votes
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Ackerman Conundrum

This is quite easy: Choose one of the wheels build a second wheel so it would satisfy Ackerman condition Get the First rotation point ( O1 ) Do the same with the second wheel, and get a second ...
Jonathan's user avatar
  • 334
5 votes
Accepted

Can a thing resonate whilst exposed to white noise?

You won't get much resonance because the phase the thing is being driven with keeps changing. The resonant thing will act like a notch filter, so you are left with the frequencies near its resonance. ...
Olin Lathrop's user avatar
  • 11.4k
4 votes

How do I create a graph of the phase angle and response of a harmonic excitation in Matlab?

With your code, and with $c = 0.3$, I get the following results: The amplitude and phase look OK. But the displacement does not show any damping. To see why read on below. I'm not sure about your ...
Biswajit Banerjee's user avatar
4 votes

How does load force impact load inertia?

Stretch in the spring delta $ Y = A.sin(\omega.t) = A.sin\sqrt(k/m) . t $ So the delta Y is not constant but if you are interested in delt Y_max delta $Y max = m/k$, by Hooks law. Because your ...
kamran's user avatar
  • 22.4k
4 votes

Removing beam deflection through axial force

My question is how can I incorporate the axial force? Doing so would invalidate the assumptions made in the Bernoulli beam theorem, and therefore render your deflection equation invalid. Per the ...
grfrazee's user avatar
  • 3,587
4 votes
Accepted

Finding downward force of lever bar

The input force is 18.5+20.5 ft away from the fulcrum and the load is 18.5 away from the fulcrum. This means the force applied to the load is $\frac{(18.5+20.5)}{18.5} = 2.1$ times greater than the ...
ratchet freak's user avatar
4 votes
Accepted

What software is used for drawing dynamic & mechanical diagrams?

This is more of a long comment than an answer as i can not advice any specific software. First, if you intend to do anything professional in print or web productions than yous shouldn't be looking in ...
joojaa's user avatar
  • 3,587
4 votes
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How can I absorb shock on an existing steel structure?

Large displacement shock absorbers used to dampen the effects of seismic events may be suitable for this application. These could be used to isolate the part of the structure that is grounded and the ...
Donald Gibson's user avatar
4 votes
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Finding out torque in a viscosimeter

You didn't account for the acceleration of $m_1$. Setting up a free body diagram on the weight shows: $$m_1g - T = m_1a_y$$ Where $T$ is the tension in the rope, $a_y$ is the acceleration of the ...
Mark's user avatar
  • 5,343
4 votes

Power decreases as the diameter increases

The downwards tension force in a cable with a $130\text{kg}$ mass hanging under gravity is: $$F=mg=130*9.81=1275.3\text{N}$$ The upwards force provided by a servo with arm radius $0.02\text{m}$ and ...
Jonathan R Swift's user avatar
4 votes
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Power decreases as the diameter increases

In addition to what Jonathan has said, there is several other practical things to consider: not only torque is limited, but power also; since power is torque times angular velocity (P=T*omega), your ...
oliver's user avatar
  • 158
4 votes

Resonance vs flutter

In flutter, the force applied to the structure depends on the deformation and velocity of the structure. Therefore, the force is necessarily at exactly the same frequency as the motion, though it may ...
alephzero's user avatar
  • 12.5k
4 votes
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Unit Conversion for Mass Density

First Part Simplifying the $$ 1 \ lbf = 1 \ slug .ft/sec^2 $$ then $$ 1 \ lbf \ sec^2 / in^4 = 1 \ (slug .ft/sec^2 ). (sec^2/in^4) = 12 \ slug /in^3 $$ $$ 12 \ slug / in^3 * (14.6 kg / 1\ slug)*(in/25....
epsi1on's user avatar
  • 228
4 votes

Moment equation from dynamics differs with equations from physics & statics. Where did I go wrong?

There is a slight mistake in your approach. It seems you have forgotten to add the contribution the moment due to inertial force acting at the center of mass $G$ to the moment equation. The moment ...
G R Krishna Chand Avatar's user avatar
4 votes
Accepted

Disc Brakes - Swept Area , why is larger better?

Brakes primarily convert kinetic energy to heat energy. So a large area can absorb more heat lowering the peak temperatures ;of course this is strongly affected by the thickness/mass of the discs and ...
blacksmith37's user avatar
  • 6,144
4 votes
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Why does the frequency of a bottle filling up changes?

Most acoustic vibrations of air more or less confined to a given geometry can be explained by two basic models. One is the one-dimensional treatment of the air in a tube, and the other is the lumped-...
ttonon's user avatar
  • 417
4 votes
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is a positive acceleration indication that velocity must be positive?

No, positive acceleration, alone, does not need to imply positive velocity. Another term for "acceleration in the opposite direction of the velocity" is just "deceleration". The ...
DKNguyen's user avatar
  • 5,626
3 votes

Definition of stiffness for structural dynamics: How would you find the stiffness of an unusual beam directly?

k=F/d is a linear relationship. If you're doing a non-linear analysis, you shouldn't expect a linear response. For this beam, a geometrically non-linear analysis is appropriate if your deflections ...
AndyT's user avatar
  • 3,153
3 votes
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What is the advantage of using D'Alembert's principle when dealing with dynamic systems?

I don't really understand how D'Alembert's principle "helps" in solving the problem in your OP, but I assume your teacher wants you to practise using it in simple situations before you try more ...
alephzero's user avatar
  • 12.5k
3 votes

Removing beam deflection through axial force

This is well-known theory in finite element analysis. There are two different effects that contribute to the effective stiffness of the structure in addition to the elastic stiffness $K_e$ given by ...
alephzero's user avatar
  • 12.5k
3 votes
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Approximating a Gimbal using Springs and Dampers

In my "day job" I do a lot of (mostly nonlinear!) dynamics modelling and simulation of mechanical systems. One thing that always raises a "red flag" for me is degrees of freedom with no mass, ...
alephzero's user avatar
  • 12.5k
3 votes

Unexpected Results from my Transfer Function

Checking the units is an excellent way to double check your work; kudos for doing so. However, the next step in checking to see if your results make sense is to check limits. In your case, you can ...
Chris Mueller's user avatar
3 votes
Accepted

Mass-Spring-Damper Dynamic System

Call the displacement of the box (where it is attached to the damper and spring) y(t). The force of the damper is $$-c\cdot \dot{y}$$ The force of the spring is $$k\cdot(x - y)$$ y(t) is the point ...
Dave Tweed's user avatar
  • 6,884
3 votes
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How do I represent equations of motion of a dynamic system in State Space?

Karlo mentioned to use the state space of $[q,\dot{q}]^T$ this allows you to write the system as a first order differential equation of state space. If $X$ were the state space, you could write $\dot{...
Orion Yeung's user avatar
3 votes

Why is the spin velocity of a gear irrelevant if perfectly balanced?

If the gear is not balanced then the center of mass will oscillate as it spins which will induce additional load on the shaft and create vibrations. This effect greatly depends on the speed of the ...
ratchet freak's user avatar

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