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 ...
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10 votes
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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 ...
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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 ...
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  • 6,749
7 votes
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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 ...
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  • 1,876
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. ...
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6 votes
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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 ...
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  • 1,876
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'...
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  • 2,485
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. ...
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  • 11.2k
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 ...
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  • 1,272
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 ...
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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 ...
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  • 325
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. ...
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5 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 ...
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  • 5,303
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'...
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  • 2,770
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), ...
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4 votes
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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 ...
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  • 2,485
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 ...
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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 ...
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  • 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 ...
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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 ...
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4 votes
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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 ...
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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 ...
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  • 3,395
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 ...
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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 ...
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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 ...
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  • 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 ...
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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....
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  • 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 ...
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4 votes
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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 ...
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  • 5,834
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-...
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