14
votes
How do large turbines deal with asymmetry and beat arising from those?
It is done carefully. Lots of other rotating machinery has the same problem, and whole systems exist just to deal with it.
For example, jet engines are usually smaller, but also usually spin much ...
- 11.3k
10
votes
Accepted
Derivation for bridge natural frequency estimate in Eurocodes
If we simplify the whole bridge into 2D thin beam with a constant section size, no internal damping and subject only to small vertical deflections, then the natural frequency is determined by simple ...
10
votes
Hovercraft design parameters
Designing the lift system for a hovercraft isn't actually about the mass and the acceleration, it's about the pressure required to lift the hull and the rate at which the air leaks out from under the ...
- 6,824
7
votes
Accepted
Feedback control of two-link planar manipulator
Convert the nonlinear model to state-space form, $x'=f(x,u)$, and linearize it to get a linear state-space or transfer function representation. You can use this to design a PID controller and simulate ...
- 1,901
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 ...
- 1,901
5
votes
Detailed dimensions of an aircraft engine compressor blade
The ESA has a page on compressor blades. They give a good dimensioned diagram of an approximate shape; here are some basic dimensions:
Length: 300 mm
Width: 30 mm
Height: 70 mm
Thickness: 5 mm
I can'...
- 2,475
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. ...
- 11.3k
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 ...
- 1,307
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 ...
- 1,307
5
votes
Accepted
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
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. ...
- 11.3k
4
votes
How do you find the kinematic degrees of freedom of a mechanism?
It's a question of how many independent variables you need in order to write out the equations of motion.
Let's walk through it step by step.
Start by just considering Pulley 1 and Mass A. If they'...
- 2,760
4
votes
How can I extract transfer function an unknown nonlinear system?
As I remember (learned it 15 yrs ago) You need to have an experimental data, which will help you to find "linear" sections and the their limits (with taking into account the things like hysteresis), ...
4
votes
Accepted
What is the benefit of additional planetary gears?
Advantages
I'll start off by quoting from the "Benefits" section of the Wikipedia article:
The load in a planetary gear train is shared among multiple planets, therefore torque capability is ...
- 2,475
4
votes
How do large turbines deal with asymmetry and beat arising from those?
Adjustable counterweights.
The wheels and tires of your car are not manufactured perfectly circular but after the tire gets put on (or you go for a rebalance) the mechanic will tack on weights to put ...
- 5,711
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 ...
- 3,587
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 ...
- 1,433
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 ...
- 21.4k
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 ...
- 5,711
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 ...
- 3,520
4
votes
Accepted
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 ...
- 1,076
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$$
Where $T$ is the tension in the rope, $a_y$ is the acceleration of the ...
- 5,313
4
votes
Power decreases as the diameter increases
The downwards tension force in a cable with a $130\text{kg}$ mass hanging under gravity is:
$$F=mg=130*9.81=1275.3\text{N}$$
The upwards force provided by a servo with arm radius $0.02\text{m}$ and ...
- 7,569
4
votes
Accepted
Power decreases as the diameter increases
In addition to what Jonathan has said, there is several other practical things to consider:
not only torque is limited, but power also; since power is torque times angular velocity (P=T*omega), your ...
- 158
4
votes
Resonance vs flutter
In flutter, the force applied to the structure depends on the deformation and velocity of the structure. Therefore, the force is necessarily at exactly the same frequency as the motion, though it may ...
- 12.4k
4
votes
Accepted
Unit Conversion for Mass Density
First Part
Simplifying the
$$
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 ...
- 5,967
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-...
- 390
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