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.
...
- 170
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 ...
- 1,996
5
votes
Accepted
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 ...
- 1,327
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 ...
- 334
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 ...
- 1,327
5
votes
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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. ...
- 11.4k
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 ...
- 22.6k
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 ...
- 6,101
4
votes
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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 ...
- 3,675
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 ...
- 1,078
4
votes
Accepted
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$$
Where $T$ is the tension in the rope, $a_y$ is the acceleration of the ...
- 5,333
4
votes
Power decreases as the diameter increases
The downwards tension force in a cable with a $130\text{kg}$ mass hanging under gravity is:
$$F=mg=130*9.81=1275.3\text{N}$$
The upwards force provided by a servo with arm radius $0.02\text{m}$ and ...
- 7,761
4
votes
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Power decreases as the diameter increases
In addition to what Jonathan has said, there is several other practical things to consider:
not only torque is limited, but power also; since power is torque times angular velocity (P=T*omega), your ...
- 158
4
votes
Resonance vs flutter
In flutter, the force applied to the structure depends on the deformation and velocity of the structure. Therefore, the force is necessarily at exactly the same frequency as the motion, though it may ...
- 12.6k
4
votes
Accepted
Unit Conversion for Mass Density
First Part
Simplifying the
$$
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....
- 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 ...
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 ...
- 6,172
4
votes
Accepted
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-...
- 417
4
votes
Accepted
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 ...
- 5,621
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 ...
- 3,133
3
votes
Accepted
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 ...
- 12.6k
3
votes
Accepted
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{...
- 156
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 ...
- 6,101
3
votes
Accepted
Why is the spin velocity of a gear irrelevant if perfectly balanced?
This depends greatly on the context. Here is a counter-example, a situation in which the spin velocity of the gear is relevant to the dynamics of the overall system, even if that velocity is constant....
- 2,656
3
votes
Can a thing resonate whilst exposed to white noise?
The thing will vibrate at all frequencies. It will vibrate more (be amplified) at frequencies that are close to a natural frequency. Effectively, the system will act as a band pass filter (NOT a band ...
- 2,656
3
votes
How to implement a Monte Carlo Simulation for studying uncertainty in dynamic stiffness?
My advice would be to forget about the mathematical theory and start thinking about what the engineering means. It's hard to think of any situation where the stiffness of a sensibly designed structure ...
- 12.6k
3
votes
hydraulic diameter
You have the correct answer, you just haven't simplified the terms.
Root 3 divided by 3 is 1 over root 3.
ie. x^(1/2) / x = x^(1/2).x(-1) = x^(-1/2)
- 9,712
3
votes
Linearization of dynamic equations/transfer function in control theory
In addition to @arash’s answer:
Designing directly with a nonlinear system is cumbersome, not only computationally expensive.
By linearization one can cover the whole nonlinear space, by generating ...
- 906
3
votes
Finding out torque in a viscosimeter
Mark has already pointed out what you are missing, and this is the Lagrangian approach which also should give the same result - and it does.
The position of $m_1$ is $x_1 = R \ \theta(t)$
The ...
- 1,996
3
votes
Vertical component of force for rigid wheel hitting a step
Mark has indicated that he's going to write an answer relating to conservation of angular momentum - this is very likely the best way to approach the problem.
I'm going to answer very specifically ...
- 7,761
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