| Topic: |
Science > Physics |
| User: |
"" |
| Date: |
20 Jan 2005 05:52:41 PM |
| Object: |
spring/shock absorber has "reactance"? |
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?
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| User: "richy" |
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| Title: Re: spring/shock absorber has "reactance"? |
20 Jan 2005 05:59:24 PM |
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<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?
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.
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| User: "TimPerry" |
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| Title: Re: spring/shock absorber has "reactance"? |
20 Jan 2005 06:25:25 PM |
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"richy" <invalid@nospam.com> wrote in message
news:35auukF4jsfq1U1@individual.net...
<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?
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.
cross-posted to the universe at large.
its time to refer back to the "water" analogy.
or maybe electricity is like tiny little fireflies trapped in a still...they
try to excape but are slowed by the spiral condensor... then they fall to
the ground drunk exausted and happy...
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| User: "Jonathan Barnes" |
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| Title: Re: spring/shock absorber has "reactance"? |
21 Jan 2005 12:47:30 PM |
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"richy" <invalid@nospam.com> wrote in message
news:35auukF4jsfq1U1@individual.net...
<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?
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.
Shock absorbers are non linear.
They have different resistance in bounce and rebound
They normaly act approximatly to the viscus rule ( force proportional to the
square of speed ) at low speed, at higher speeds a spring loaded valve opens
and holds force approximatly constant.
In addition to this gas shock absorbers have a non liniar "spring" turm as
the gas in there top chamber acts as a gas spring storing energy.
As if the above was not enough they have end stops.. rubber springs..
To regard a shock absorber as an equivelent to a single electronic component
is just daft.
A simple dash pot can be modeled by the viscos law.
--
Jonathan
Barnes's theorem; for every foolproof device
there is a fool greater than the proof.
To reply remove AT
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| User: "Airy R.Bean" |
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| Title: Re: spring/shock absorber has "reactance"? |
22 Jan 2005 05:18:16 AM |
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A shock absorber that moves other than in
a straight line is an MOT failure.
"Jonathan Barnes" <jbarnes6@btinternet.com> wrote in message
news:csrio2$8je$1@titan.btinternet.com...
Shock absorbers are non linear.
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| User: "Fred Abse" |
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| Title: Re: spring/shock absorber has "reactance"? |
22 Jan 2005 08:24:27 AM |
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On Sat, 22 Jan 2005 11:18:16 +0000, Airy R.Bean top posted:
A shock absorber that moves other than in a straight line is an MOT
failure.
"Jonathan Barnes" <jbarnes6@btinternet.com> wrote in message
news:csrio2$8je$1@titan.btinternet.com...
Shock absorbers are non linear.
I think he was referring to transfer function, not mechanical alignment.
Anyway, what about lever-type shock absorbers?
--
Then there's duct tape ...
(Garrison Keillor)
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| User: "" |
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| Title: Re: spring/shock absorber has "reactance"? |
21 Jan 2005 01:10:08 AM |
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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/ |
-----------------------------------------------------------------------------
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| User: "Vilnius Roma" |
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| Title: Re: spring/shock absorber has "reactance"? |
21 Jan 2005 08:30:42 AM |
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<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.
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| User: "Airy R.Bean" |
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| Title: Re: spring/shock absorber has "reactance"? |
21 Jan 2005 08:38:59 AM |
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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.
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| User: "Farina" |
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| Title: Re: spring/shock absorber has "reactance"? |
21 Jan 2005 08:57:43 AM |
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"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?
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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| User: "Airy R.Bean" |
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| Title: Re: spring/shock absorber has "reactance"? |
21 Jan 2005 09:04:47 AM |
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The "spring back" is due to the compressed air and
not to a spring, as such.
"Farina" <nospam@nospam.com> wrote in message
news:35cjj0F4k0g9gU1@individual.net...
"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.
Bicycle pump I have has no internal spring
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| User: "" |
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| Title: Re: spring/shock absorber has "reactance"? |
21 Jan 2005 09:12:53 AM |
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On Fri, 21 Jan 2005 14:38:59 -0000, "Airy R.Bean" <Me@privacy.net>
wrote:
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.
Rubbish.
Your analogy is incorrect.
You are trying use technology to explain the science.
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| User: "N:dlzc D:aol T:com \dlzc\ N: dlzc1 D:cox" |
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| Title: Re: spring/shock absorber has "reactance"? |
21 Jan 2005 07:58:42 AM |
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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.
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
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| User: "Teddy Rubberford" |
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| Title: Re: spring/shock absorber has "reactance"? |
20 Jan 2005 09:27:16 PM |
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<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?
is this a job for the goatse man ?
-------------------------------------------------
Ted Rubberford.
'The Man In The Green Latex Skintight Hood'
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| User: "Rudolf Zeitschek" |
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| Title: Re: spring/shock absorber has "reactance"? |
21 Jan 2005 11:51:06 AM |
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schrieb:
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 the mechanical analogue of capacitance is a spring, then the analogue
of an inductor is a mass.
These two can resonate like a car without shock absorbers. The shock
absorbers are the analogue of a resistor (damping the oscillation.
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| User: "Greg Locock" |
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| Title: Re: spring/shock absorber has "reactance"? |
21 Jan 2005 05:53:59 AM |
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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?
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.
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| User: "John Larkin" |
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| Title: Re: spring/shock absorber has "reactance"? |
21 Jan 2005 03:15:01 PM |
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On 21 Jan 2005 11:53:59 GMT, Greg Locock <greglocock@yahoo.com.au>
wrote:
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?
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.
But both mechanical and thermal systems, translated to lumped
electrical equivalents, can be dynamically modeled with Spice. If
you're modeling something like an electronic servo system and its
motor and loads, you may as well toss the whole system into the
electrical domain; you're not going to have much fun moving all the
electronic parts into a mechanical simulator.
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.
Nonlinear isn't difficult. It's distributed or diffusion models that
are harder to do with Spice.
John
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| User: "Greg Locock" |
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| Title: Re: spring/shock absorber has "reactance"? |
22 Jan 2005 04:12:42 PM |
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John Larkin <jjlarkin@highSNIPlandTHIStechPLEASEnology.com> wrote in
news:8sr2v091nkurlakpuqu5cqqlqib25kb1e9@4ax.com:
On 21 Jan 2005 11:53:59 GMT, Greg Locock <greglocock@yahoo.com.au>
wrote:
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?
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.
But both mechanical and thermal systems, translated to lumped
electrical equivalents, can be dynamically modeled with Spice. If
you're modeling something like an electronic servo system and its
motor and loads, you may as well toss the whole system into the
electrical domain; you're not going to have much fun moving all the
electronic parts into a mechanical simulator.
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.
Nonlinear isn't difficult. It's distributed or diffusion models that
are harder to do with Spice.
Well, we can incorporate FEA models into our suspension design programs, so
diffuse systems are easy. And I do have the antilock and stability control
computers simulated in or interfaced with my suspension program. So that's
the control side sorted out.
So, what is the electrical analogue of static and dynamic friction?
Cheers
Greg Locock
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| User: "Franz Heymann" |
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| Title: Re: spring/shock absorber has "reactance"? |
23 Jan 2005 09:23:15 AM |
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"Greg Locock" <greglocock@yahoo.com.au> wrote in message
news:Xns95E75E0A4EF3Dgreglocockyahoocomau@211.29.133.50...
So, what is the electrical analogue of static and dynamic friction?
Draw the speed vs force diagrams and you will see that force is not
proportional to speed. Dynamic friction is analogous to a zener
diode producing a pd of V in series with an EMF of -1/2 V.
Franz
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| User: "Bruce Durdle" |
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| Title: Re: spring/shock absorber has "reactance"? |
23 Jan 2005 02:43:10 AM |
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As late as 1970-odd, most of the complex dynamic calculations were
carried out using analogue computers. It is possible to build an
electronic circuit that efectively simulates a friction system - I did a
Master of Engineering degree based on an analogue computer model of a
steam turbine and governor, looking specifically at nonlinear and
frictin effects.
From memory, a LOT of the dynamic problems thrown up by the Saturn and
similar early space missions were sorted out on electronic analogue
computers ...
Bruce.
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| User: "N:dlzc D:aol T:com \dlzc\ N: dlzc1 D:cox" |
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| Title: Re: spring/shock absorber has "reactance"? |
22 Jan 2005 05:02:40 PM |
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Dear Greg Locock:
"Greg Locock" <greglocock@yahoo.com.au> wrote in message
news:Xns95E75E0A4EF3Dgreglocockyahoocomau@211.29.133.50...
....
So, what is the electrical analogue of static and dynamic friction?
I don't think electronics has a non-active analog. A diode has a threshold
voltage, below which very little current flows. If the diode is formed of
germanium, this is 0.3 volts. If silicon it is between 0.6 and 0.7 volts.
David A. Smith
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| User: "N:dlzc D:aol T:com \dlzc\ N: dlzc1 D:cox" |
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| Title: Re: spring/shock absorber has "reactance"? |
22 Jan 2005 09:59:38 PM |
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Dear Greg Locock:
"Greg Locock" <greglocock@yahoo.com.au> wrote in message
news:Xns95E75E0A4EF3Dgreglocockyahoocomau@211.29.133.50...
...
So, what is the electrical analogue of static and dynamic friction?
I don't think electronics has a non-active analog. A diode has a
threshold voltage, below which very little current flows. If the diode
is formed of germanium, this is 0.3 volts. If silicon it is between 0.6
and 0.7 volts.
Fluorescent light fixtures require high voltage to fire, and lower voltage
to sustain fluorescence once lit.
David A. Smith
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| User: "Beachcomber" |
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| Title: Re: spring/shock absorber has "reactance"? |
21 Jan 2005 09:49:09 AM |
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On 20 Jan 2005 15:52:41 -0800, 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?
Yes... Think of a standard spring watch movement. (I believe the
formal term is "escapement"). There is a specific time period between
each direction reversal, just like a clock pendulum.
Beachcomber
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| User: "daestrom" |
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| Title: Re: spring/shock absorber has "reactance"? |
21 Jan 2005 04:21:49 PM |
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"Beachcomber" <not_real@xxx.yyy> wrote in message
news:41f122e6.2272312@news.comcast.giganews.com...
On 20 Jan 2005 15:52:41 -0800, 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?
Yes... Think of a standard spring watch movement. (I believe the
formal term is "escapement"). There is a specific time period between
each direction reversal, just like a clock pendulum.
Exactly. The mass and shape of the wheel determine the moment of inertia of
the wheel. This can be analogous to inductance. The spring, analogous to
capacitance. The combination forms a 'tuned' circuit that oscillates at a
resonant frequency and requires only a little energy input to make up for
frictional losses. Much like how a tuned circuit draws little real power
from the supply to make up for resistive losses.
The escapement mechanically gets a 'nudge' from the pawl system that it
controls as it swings through the center point. Electronically, this is
similar to having a pulse of power applied as the current through the
inductor approaches maximum.
daestrom
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| User: "John Larkin" |
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| Title: Re: spring/shock absorber has "reactance"? |
20 Jan 2005 06:40:45 PM |
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On 20 Jan 2005 15:52:41 -0800, 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)
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
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| User: "Don Kelly" |
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| Title: Re: spring/shock absorber has "reactance"? |
20 Jan 2005 11:27:08 PM |
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"John Larkin" <jjlarkin@highSNIPlandTHIStechPLEASEnology.com> wrote in
message news:6dj0v0h4lt6fuo8i52l64ehhsrdvq6og9p@4ax.com...
On 20 Jan 2005 15:52:41 -0800, 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)
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
To complete your analogy - treat current as force and voltage as velocity.
(nodal modal)
You can also use
current+velocity
Voltage =force
Inductance=Mass
Capacitance =compliance
resistance =damping
--
Don Kelly
dhky@peeshaw.ca
remove the urine to answer
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| User: "" |
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| Title: Re: spring/shock absorber has "reactance"? |
21 Jan 2005 01:24:01 AM |
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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.
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| User: "Vilnius Roma" |
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| Title: Re: spring/shock absorber has "reactance"? |
21 Jan 2005 08:35:07 AM |
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<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.
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.
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| User: "" |
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| Title: Re: spring/shock absorber has "reactance"? |
21 Jan 2005 02:54:36 PM |
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I know how the sytem works.
The spring ABSORBS the shock.
Try the basic cart with your "shock absorbers" and no springs.
Better still, take the road springs off your car/automobile, leaving
your "shock absorbers in place.
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| User: "" |
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| Title: Re: spring/shock absorber has "reactance"? |
21 Jan 2005 03:53:47 AM |
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John Larkin wrote:
On 20 Jan 2005 15:52:41 -0800, 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)
Actually, it's:
Capacitance = spring
Inductance = mass
Resistance = damping (shock absorber, viscoscity)
Slick
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| User: "John Fields" |
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| Title: Re: spring/shock absorber has "reactance"? |
21 Jan 2005 06:32:18 PM |
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On Thu, 20 Jan 2005 16:40:45 -0800, John Larkin
<jjlarkin@highSNIPlandTHIStechPLEASEnology.com> wrote:
If you treat
Capacitance = mass
Inductance = spring
Resistance = damping (shock absorber, viscoscity)
then identical differential equations will describe both systems.
---
I haven't read the whole thread so I don't know if anyone else caught
it, but:
Capacitance = spring
Inductance = mass
Resistance = damping
--
John Fields
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