44 votes
Accepted

Why are engine blocks so robust apart from containing high pressure?

If you consider only the static forces then indeed the thickness might seem over-engineered. However, engine blocks are not statically loaded. They operate in the range of a few hundred to a few ...
  • 22.9k
15 votes

Why are engine blocks so robust apart from containing high pressure?

You need to consider that the complete engine block has to withstand the reciprocating forces generated by each of the pistons and con rods moving as well as the rotational forces from the rotating ...
  • 14.2k
12 votes

Can gravity be a driving force for a spring-mass system?

It really depends on the problem and what you want to capture. Usually, in classes, it may be beneficial for the students at an initial stage to disregard gravity alltogether in order to simplify the ...
  • 22.9k
12 votes

Why are engine blocks so robust apart from containing high pressure?

The vibration, loading, and fatigue aspects have already been addressed, but a wide range of operating temperatures is another factor. A typical consumer engine can be deployed in anything from say -...
  • 221
9 votes

Is there a mechanical equivalent to a hi/low pass filter (as in electrical engineering)?

In a more general sense, the electrical concepts of inductance, capacitance and resistance are equivalent to mass, spring constant and friction in the mechanical world. Voltage becomes force and ...
  • 6,759
8 votes

Is there a mechanical equivalent to a hi/low pass filter (as in electrical engineering)?

Yes, for sound specifically there is a term called "acoustic impedance" that, just like electrical impedance, is frequency dependent. Acoustic impedance results from the acoustic wave equation, which ...
  • 3,535
8 votes
Accepted

Stiffness of a cantilever beam

Stiffness is a murky term frequently used ambiguously in engineering. However, the most common definition of stiffness is the product of a beam's Young's Modulus $E$ (which is a function of its ...
  • 13k
7 votes

In vibration study, should the reference be necessarily the mean/equilibrium position?

It can be arbitrary. It just simplifies the mathematics significantly. However the end result should be the same.
  • 22.9k
6 votes

Three-phase versus single-phase operation of a generator

But I'm thinking it may be better (more efficient maybe? less vibration maybe?) to run it in three-phase mode, with the load balanced among the three hot terminals. Correct. Figure 1. The load is ...
  • 8,824
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

Modelling splashing water in FEA

This may be only a partial answer since I don't have any idea what to do for the Young's modulus of the fluid. Consider the paper Dynamic Pressures on Accelerated Fluid Containers by G. W. Housner. ...
  • 3,587
5 votes

Is there a mechanical equivalent to a hi/low pass filter (as in electrical engineering)?

There are analogs to filters in lots of mechanical systems. In fluid systems prone to pressure spikes perhaps because they use a fixed displacement pump, an accumulator will be used to filter out ...
  • 2,135
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'...
  • 2,485
5 votes

How to prevent vibration loosening whilst maintaining adjustability?

Double nutting can be an easy option for this. I was about to describe it myself, but these folks do a great job. This image, from the article, models the forces that do the job. Take note of the ...
  • 1,976
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

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
5 votes
Accepted

Do internal / external stresses affect modal frequency?

Consider a small piece cut out of a structure that has non-zero internal stress. To maintain equilibrium, there must be some forces applied to the boundary of the piece. (Of course when it was part ...
  • 12.5k
5 votes
Accepted

How do those "dipole-shaped" weights attached to sections of electrical power lines work?

According to the wiki, these are called Stockbridge dampers. The design is tuned for a specific length and one might also expect a specific mass/material. The weights are mounted on flexible arms, ...
  • 6,427
4 votes
Accepted

Are there standard vibration and shock specs for shipment of a product?

UPS has, or at least had when I was transit testing packaged products, a specific packaging test standard based on ISTA standards and ASTM D4169. There's also a MIL-STD, 810 something, but I don't ...
  • 2,135
4 votes

Are there standard vibration and shock specs for shipment of a product?

When I have received fragile content in the past it has always come with a Shockwatch label attached to the side. I'm not 100% sure, but I believe there is some sort of guarantee by the shipper to ...
4 votes

I want a shockproof table for a model train. That is, protection from physical jolts, not electrical volts

Build two tables. The outer table will have a hole in the middle and only hold the glass plate. There should be about 10 cm of free space between the tables. The train will be placed on the inner ...
  • 1,845
4 votes
Accepted

Strategies for cable vibration: eigenvalues are suitable?

Mathematically, an eigenvalue analysis assumes the modal displacements are infinitesimally small, so the change in stiffness in the cable caused by the vibration is a second order effect which can be ...
  • 12.5k
4 votes

What does 1 x rpm or 2 x rpm or 3 x rpm in vibration analysis mean?

RPM = revolutions per minute. In the context of vibration monitoring, 1 x rpm means a vibration frequency that is the same as the rotation speed (one vibration oscillation per revolution of the ...
  • 12.5k
4 votes
Accepted

How can I measure the vibrations of a solid object?

An accelerometer is the correct choice, but the smartphone accelerometer gets its readouts smoothed out in software before being made accessible to userspace. It won't pick up such fine vibrations. ...
  • 6,133
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 ...
  • 12.5k
4 votes
Accepted

What is the difference between washer and O-ring? what is their advantages over the other?

An o-ring usually (but not always) has a round section and is made of a compressible material such as rubber, neoprene, silicon etc. A washer tends to have a square or rectangular section and is ...
  • 14.2k
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
4 votes

Why are engine blocks so robust apart from containing high pressure?

The example picture does not show a very solid outter wall; what you see a gasket surface. A closer look will show a lot of variations in thickness, with a lot of ribbs, bulky parts (for mounting, and ...
  • 41
4 votes

Why are engine blocks so robust apart from containing high pressure?

No one has mentioned yet that there are structural loads placed on the block by other components. The first that comes to mind are the cylinder heads, and as it (they) are torqued, the block needs to ...
  • 141
4 votes
Accepted

Wierd faulty gearbox FFT

Vibrations are the manifestation of things occurring at some frequency. This can be one per rev from imbalance (nothing is ever perfectly balanced) in gears spinning, one per tooth from each tooth ...
  • 1,084

Only top scored, non community-wiki answers of a minimum length are eligible