spring/shock absorber has "reactance"?

Guest
They say that the mechanical analogues of capacitors are springs, and
of inductors are shock absorbers. And this does have a strong
intuitive appeal.

But do springs/shock absorbers have any kind of frequency-dependent
behaviors?
 
<alanh_27@yahoo.com> wrote in message
news:1106265161.475444.323700@z14g2000cwz.googlegroups.com...
They say that the mechanical analogues of capacitors are springs, and
of inductors are shock absorbers. And this does have a strong
intuitive appeal.

But do springs/shock absorbers have any kind of frequency-dependent
behaviors?
Click to expand...
inductors are not shock absorbers, as they do not dissipate energy like
shocks do.
Shocks would be simulated by a resistive element.

Answer to second is Yes. They are "tuned" to your cars mass, and expected
road conditions.
 
On 20 Jan 2005 15:52:41 -0800, alanh_27@yahoo.com wrote:

They say that the mechanical analogues of capacitors are springs, and
of inductors are shock absorbers. And this does have a strong
intuitive appeal.

But do springs/shock absorbers have any kind of frequency-dependent
behaviors?
Click to expand...
If you treat

Capacitance = mass
Inductance = spring
Resistance = damping (shock absorber, viscoscity)

then identical differential equations will describe both systems.

A parallel L-C circuit has a resonant frequency where it's easiest to
excite. A mass hung on a spring is the same, it twangs at a resonant
frequency if whacked. Jump on the fender of a car with bad shocks; it
will bounce at the resonant frequency.

John
 
in article 1106265161.475444.323700@z14g2000cwz.googlegroups.com,
alanh_27@yahoo.com at alanh_27@yahoo.com wrote on 1/20/05 3:52 PM:

They say that the mechanical analogues of capacitors are springs, and
of inductors are shock absorbers. And this does have a strong
intuitive appeal.

But do springs/shock absorbers have any kind of frequency-dependent
behaviors?
Click to expand...
These analogies are meaningful because of identical mathematical
description. As part of the formalism, charge is equivalent to position and
rate of charge change is current and analogous to rate of change of
position.

Capacitors store potential electrical energy C*V^2/2 as springs store
potential mechanical energy k*x^2/2. Inductors store kinetic electrical
energy L*I^2/2 as masses store kinetic mechanical energy m*v^2/2.

When you make a lagrangian formulation based upon these energies, the
equations for electrical and mechanical motions are identical and frequency
dependence is identical.

Bill

Bill
 
<alanh_27@yahoo.com> wrote in message
news:1106265161.475444.323700@z14g2000cwz.googlegroups.com...
They say that the mechanical analogues of capacitors are springs, and
of inductors are shock absorbers. And this does have a strong
intuitive appeal.

But do springs/shock absorbers have any kind of frequency-dependent
behaviors?
Click to expand...
is this a job for the goatse man ?
-------------------------------------------------
Ted Rubberford.
'The Man In The Green Latex Skintight Hood'
 
In alt.engineering.electrical richy <invalid@nospam.com> wrote:

| inductors are not shock absorbers, as they do not dissipate energy like
| shocks do.
| Shocks would be simulated by a resistive element.

There is a very resistive element to shock absorbers, but there is some
that I suppose coule be said to be inductive. It's just a very low Q.

--
-----------------------------------------------------------------------------
| Phil Howard KA9WGN | http://linuxhomepage.com/ http://ham.org/ |
| (first name) at ipal.net | http://phil.ipal.org/ http://ka9wgn.ham.org/ |
-----------------------------------------------------------------------------
 
In alt.engineering.electrical John Larkin <jjSNIPlarkin@highthislandpleasetechnology.xxx> wrote:

| If you jump on the fender of a car with bad shocks, the entire car
| oscillates. It's the mass of the car and the stiffness of the springs
| that determine the resonant frequency, typically a couple of Hz; if
| you take the cars's mass as infinite, absolutely nothing will happen
| if you jump on it.

Nor will you be able to get off the car :)

--
-----------------------------------------------------------------------------
| Phil Howard KA9WGN | http://linuxhomepage.com/ http://ham.org/ |
| (first name) at ipal.net | http://phil.ipal.org/ http://ka9wgn.ham.org/ |
-----------------------------------------------------------------------------
 
If you make a basic cart out of just a box and four wheels, the ride
would be rough.

If, to improve the ride, you are given the choice of using either a set
of springs or a set of what most people call "shock absobers" you would
use the springs.

Why?

Because the springs absorb the shocks.

The telescopic devices which most people call "shock absorbers" are not
shock absorbers. They are dampers.
 
John Larkin wrote:
If you jump on the fender of a car with bad shocks, the entire car
oscillates. It's the mass of the car and the stiffness of the springs
that determine the resonant frequency, typically a couple of Hz; if
you take the cars's mass as infinite, absolutely nothing will happen
if you jump on it.

John
Click to expand...
Actually, you'll be sucked into the resulting black hole...

--
Regards,
Robert Monsen

"Your Highness, I have no need of this hypothesis."
- Pierre Laplace (1749-1827), to Napoleon,
on why his works on celestial mechanics make no mention of God.
 
Reactance is characterised by the storage of energy.

In the case of the capacitor, you might think that your
AC source is the only voltage source in your circuit, but
after the first 1/4 cycle, the capacitor acts as a voltage source
and starts to give back the energy that it has stored.

The combined result of the two voltage sources, your
AC excitation and the capacitor itself, accounts for
the out-of-phase current waveform.

(This bothered me for years! How could the current
be non-zero if the AC driving voltage was zero?!)

The same analogy applies to springs and to shock absorbers;
the spring stores energy when stretched; the shock-absorber
stores energy when compressed. Both the spring and shock
absorber will return energy at some time and this exhibit reactance!

<alanh_27@yahoo.com> wrote in message
news:1106265161.475444.323700@z14g2000cwz.googlegroups.com...
They say that the mechanical analogues of capacitors are springs, and
of inductors are shock absorbers. And this does have a strong
intuitive appeal.

But do springs/shock absorbers have any kind of frequency-dependent
behaviors?
Click to expand...
 
John Larkin wrote:
On 20 Jan 2005 15:52:41 -0800, alanh_27@yahoo.com wrote:

They say that the mechanical analogues of capacitors are springs,
and
of inductors are shock absorbers. And this does have a strong
intuitive appeal.

But do springs/shock absorbers have any kind of frequency-dependent
behaviors?

If you treat

Capacitance = mass
Inductance = spring
Resistance = damping (shock absorber, viscoscity)
Click to expand...
Actually, it's:

Capacitance = spring
Inductance = mass
Resistance = damping (shock absorber, viscoscity)



Slick
 
On Fri, 21 Jan 2005 09:53:26 -0000, "Airy R.Bean" <Me@privacy.net>
wrote:

The same analogy applies to springs and to shock absorbers;
the spring stores energy when stretched; the shock-absorber
stores energy when compressed.
Click to expand...
Your statement is complete rubbish. If you don't know the science,
don't make it up.
 
alanh_27@yahoo.com wrote in
news:1106265161.475444.323700@z14g2000cwz.googlegroups.com:

They say that the mechanical analogues of capacitors are springs, and
of inductors are shock absorbers. And this does have a strong
intuitive appeal.

But do springs/shock absorbers have any kind of frequency-dependent
behaviors?
Click to expand...
This is some mad person's view of the world. To those of us who were
brought up in the mechanical field then it is perhaps simpler to re-state
the basics - dampers dissipate energy, springs and masses store energy.

So, I doubt that shock absorbers are anything other than resistors,
whichever choice of voltage or current you think represents displacement.

The tradition by which control theory people attempt to reduce mechanical
systems to electrical analogues is, to my mind, counter productive and
basically a bit stupid.

Of course anyone who wishes to demonstrate the converse is more than
welcome to build the electrical analogue to a (non linear) suspension
model, with 500 DOF, and solve it.
 
Dear phil-news-nospam:

<phil-news-nospam@ipal.net> wrote in message
news:csq9sg12e88@news1.newsguy.com...
In alt.engineering.electrical richy <invalid@nospam.com> wrote:

| inductors are not shock absorbers, as they do not dissipate energy like
| shocks do.
| Shocks would be simulated by a resistive element.

There is a very resistive element to shock absorbers, but there is some
that I suppose coule be said to be inductive. It's just a very low Q.
Click to expand...
Shock absorbers are not as similar to resistive elements as they could be.
They are not linear with "current". Doesn't muck with resonant frequency
much...

David A. Smith
 
<phil-news-nospam@ipal.net> wrote in message
news:csq9sg12e88@news1.newsguy.com...
In alt.engineering.electrical richy <invalid@nospam.com> wrote:

| inductors are not shock absorbers, as they do not dissipate energy like
| shocks do.
| Shocks would be simulated by a resistive element.

There is a very resistive element to shock absorbers, but there is some
that I suppose coule be said to be inductive. It's just a very low Q.
Click to expand...

Wrong. Inductors store energy, Shocks do not.
 
<dmb06851@yahoo.com> wrote in message
news:1106292241.636782.279620@z14g2000cwz.googlegroups.com...
If you make a basic cart out of just a box and four wheels, the ride
would be rough.

If, to improve the ride, you are given the choice of using either a set
of springs or a set of what most people call "shock absobers" you would
use the springs.

Why?

Because the springs absorb the shocks.

The telescopic devices which most people call "shock absorbers" are not
shock absorbers. They are dampers.
Click to expand...
Wrong.
The spring stores the energy and puts it back out over a longer time period,
smothing the ride,
and a damper = shock adsorber, it is the only thing that dissipates the
energy.
 
"Airy R.Bean" <Me@privacy.net> wrote in message
news:35c20gF4kjnumU1@individual.net...
Reactance is characterised by the storage of energy.

In the case of the capacitor, you might think that your
AC source is the only voltage source in your circuit, but
after the first 1/4 cycle, the capacitor acts as a voltage source
and starts to give back the energy that it has stored.

The combined result of the two voltage sources, your
AC excitation and the capacitor itself, accounts for
the out-of-phase current waveform.

(This bothered me for years! How could the current
be non-zero if the AC driving voltage was zero?!)

The same analogy applies to springs and to shock absorbers;
the spring stores energy when stretched; the shock-absorber
stores energy when compressed.
Click to expand...
Wrong. shock absorber does not store energy, it dissapates it.
 
If you take a shock absorber that is not mounted in a vehicle,
and compress it, you'll find that it will spring back, just
as will a bicycle pump.

However, having thought further about the OP, perhaps he,
or the person advising him, meant to refer to springs and to masses,
rather than to springs and to shock absorbers?

"Vilnius Roma" <nospam@nospam.com> wrote in message
news:35ci0cF4kp41uU1@individual.net...
phil-news-nospam@ipal.net> wrote in message
news:csq9sg12e88@news1.newsguy.com...
In alt.engineering.electrical richy <invalid@nospam.com> wrote:

| inductors are not shock absorbers, as they do not dissipate energy
like
| shocks do.
| Shocks would be simulated by a resistive element.

There is a very resistive element to shock absorbers, but there is some
that I suppose coule be said to be inductive. It's just a very low Q.



Wrong. Inductors store energy, Shocks do not.
Click to expand...
 
Yes- you're partly right, and I was misled by
the OP, who perhaps was misguided into referring
to shock absorbers rather than to masses.

However, if you take a shock absorber that is not
mounted in a vehicle and compress it, you'll find that
it will spring back, much as if you compress a bicycle
pump with your finger closing the hole at the sharp end.

It won't spring back as far, nor as readily, however.

Let us not get side-tracked into irrelevancies; what the
OP asked was for an explanation of reactance, and I think
he got a good one from me, EOE, which you have reproduced
below.

"Vilnius Roma" <nospam@nospam.com> wrote in message
news:35cic7F4kjdbdU1@individual.net...
"Airy R.Bean" <Me@privacy.net> wrote in message
news:35c20gF4kjnumU1@individual.net...
Reactance is characterised by the storage of energy.
In the case of the capacitor, you might think that your
AC source is the only voltage source in your circuit, but
after the first 1/4 cycle, the capacitor acts as a voltage source
and starts to give back the energy that it has stored.
The combined result of the two voltage sources, your
AC excitation and the capacitor itself, accounts for
the out-of-phase current waveform.
(This bothered me for years! How could the current
be non-zero if the AC driving voltage was zero?!)
The same analogy applies to springs and to shock absorbers;
the spring stores energy when stretched; the shock-absorber
stores energy when compressed.
Wrong. shock absorber does not store energy, it dissapates it.
Click to expand...
 
"Airy R.Bean" <Me@privacy.net> wrote in message
news:35civeF4kfve7U1@individual.net...
If you take a shock absorber that is not mounted in a vehicle,
and compress it, you'll find that it will spring back, just
as will a bicycle pump.

However, having thought further about the OP, perhaps he,
or the person advising him, meant to refer to springs and to masses,
rather than to springs and to shock absorbers?
Click to expand...
The some shocks have small return springs inside them, with a hydraulic
metering valve that limits rates and provides resistance.
some shocks do not have internal springs at all
Bicycle pump I have has no internal spring
 
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