Science > Physics > Why does a starter motor in a motor car have a high current requirement?
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Science > Physics |
| User: |
"JohnDeCarlos" |
| Date: |
19 May 2004 03:08:49 PM |
| Object: |
Why does a starter motor in a motor car have a high current requirement? |
Thanks in advance for your response
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| User: "Michael Varney" |
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| Title: Re: Why does a starter motor in a motor car have a high current requirement? |
19 May 2004 03:21:40 PM |
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"JohnDeCarlos" <yuetwah2000@hotmail.com> wrote in message
news:d2005bc8.0405191208.5474bdbc@posting.google.com...
Thanks in advance for your response
Are these homework problems? Are you trying to cheat?
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| User: "floyd" |
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| Title: Re: Why does a starter motor in a motor car have a high current requirement? |
19 May 2004 10:19:30 PM |
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(JohnDeCarlos) wrote in message news:<d2005bc8.0405191208.5474bdbc@posting.google.com>...
Thanks in advance for your response
The power delivered is the voltage times current which gives watts.
746 watts in 1 hp if that helps. The voltage in your house is 120 V
(rms), but you have 12 V in your car. So a 1 hp motor in your car
would draw 10 times more current than a motor of the same power in
your house.
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| User: "Jim" |
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| Title: Re: Why does a starter motor in a motor car have a high current requirement? |
20 May 2004 10:10:04 PM |
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(JohnDeCarlos) wrote:
Thanks in advance for your response
To start the car,... I think.
Jim
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| User: "G=EMC^2 Glazier" |
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| Title: Re: Why does a starter motor in a motor car have a high currentreq... |
24 May 2004 09:20:34 AM |
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Hi Jim The motor has to get heavy parts moving,and that means greater
electrical energy. It takes all 12 volts,and has a heavy wire.
Electrical wire obeys the inverse square law. Bert
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| User: "Michael Varney" |
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| Title: Re: Why does a starter motor in a motor car have a high currentreq... |
24 May 2004 09:41:43 AM |
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"G=EMC^2 Glazier" <herbertglazier@webtv.net> wrote in message
news:23090-40B204B2-229@storefull-3172.bay.webtv.net...
Hi Jim The motor has to get heavy parts moving,and that means greater
electrical energy. It takes all 12 volts,and has a heavy wire.
Electrical wire obeys the inverse square law. Bert
You are an idiot.
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| User: "John Fields" |
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| Title: Re: Why does a starter motor in a motor car have a high current req... |
24 May 2004 10:41:23 AM |
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On Mon, 24 May 2004 10:20:34 -0400, (G=EMC^2
Glazier) wrote:
Hi Jim The motor has to get heavy parts moving,and that means greater
electrical energy. It takes all 12 volts,and has a heavy wire.
Electrical wire obeys the inverse square law.
---
So you'll make money if you buy wire on a mountaintop and sell it at
the seashore for the same $/lb.?
--
John Fields
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| User: "The Ghost In The Machine" |
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| Title: Re: Why does a starter motor in a motor car have a high current requirement? |
21 May 2004 10:59:38 AM |
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In sci.physics, JohnDeCarlos
<yuetwah2000@hotmail.com>
wrote
on 19 May 2004 13:08:49 -0700
<d2005bc8.0405191208.5474bdbc@posting.google.com>:
Thanks in advance for your response
Well, a standard gasoline motor has to run at 80-100 kW, as it
turns out. Since the standard motor also has an RPM of about
800 RPM to 1,200 RPM at idle (I'd have to look), and presumably
running the motor below its suggested idle causes many problems,
one has to basically crank up the motor to this revolution,
with everything more or less working.
Now let's take out the spark plugs (well, the spark bit, anyway),
and the fuel, and consider the motor as a rather interesting
geared piston arrangement. The standard stroke of a 4-stroke
is: intake, compression, power, exhaust. The one that
concerns the starter is the compression stroke.
A gasoline motor has about an 8:1 compression ratio, and at
any time at most one cylinder is compressed in a 4-banger
(a V6 and V8 might have two). So now it's a matter of looking
at the size of the cylinder, the amount of travel, and the
pressure.
The pressure's easy: air pressure is 101350 Pascal.
That compresses to 810800 Pascal. The pressure
difference presses on the piston, resisting the compression.
This shows up as a force; one can integrate and
therefore compute the amount of energy required to
compress that one piston. Since we have specified
1,000 RPM we know how often that piston needs to
compress per second.
Because of the way an engine's designed it is not
clear that another piston's expansion will help
compress the one.
http://www.bmwusa.com/vehicles/3/325iSedan/techdata.htm
is probably as good a reference as any; BMW is good at
technical specs. :-) Unfortunately they seem to have
learned that we like inches, horsepower and lb-ft, as opposed
to cm, kiloWatts, and N-m. I'm also not certain whether
the bore refers to diameter or radius, though it's far easier
to measure the former. The compression ratio for this
engine is a little higher than I specified above (10.5 : 1).
Now you can grind through the computations (I don't have the
time at the moment) and work out how much torque that engine
needs in order to counteract the cylinder pressure (the
unknown here is the camshaft, admittedly, but one can at least
work out the force required).
--
#191,
It's still legal to go .sigless.
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| User: "Jim" |
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| Title: Re: Why does a starter motor in a motor car have a high current requirement? |
21 May 2004 05:59:45 PM |
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On Fri, 21 May 2004 15:59:38 GMT, The Ghost In The Machine
<ewill@aurigae.athghost7038suus.net> wrote:
In sci.physics, JohnDeCarlos
<yuetwah2000@hotmail.com>
wrote
on 19 May 2004 13:08:49 -0700
<d2005bc8.0405191208.5474bdbc@posting.google.com>:
Thanks in advance for your response
Well, a standard gasoline motor has to run at 80-100 kW, as it
turns out. Since the standard motor also has an RPM of about
800 RPM to 1,200 RPM at idle (I'd have to look), and presumably
running the motor below its suggested idle causes many problems,
one has to basically crank up the motor to this revolution,
with everything more or less working.
You can jack up one rear wheel of a VW, pop the trany into 3rd/4th,
give it spin by hand, and start the motor. (probably turning about
"2" RPM at start-up)
Jim
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| User: "The Ghost In The Machine" |
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| Title: Re: Why does a starter motor in a motor car have a high current requirement? |
21 May 2004 10:59:38 PM |
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In sci.physics, Jim
<lose30lbs@workformhome.com>
wrote
on 21 May 2004 18:59:45 EDT
<h42ta0ls8o9p6ourqpcm7cnb8fattc5hak@4ax.com>:
On Fri, 21 May 2004 15:59:38 GMT, The Ghost In The Machine
<ewill@aurigae.athghost7038suus.net> wrote:
In sci.physics, JohnDeCarlos
<yuetwah2000@hotmail.com>
wrote
on 19 May 2004 13:08:49 -0700
<d2005bc8.0405191208.5474bdbc@posting.google.com>:
Thanks in advance for your response
Well, a standard gasoline motor has to run at 80-100 kW, as it
turns out. Since the standard motor also has an RPM of about
800 RPM to 1,200 RPM at idle (I'd have to look), and presumably
running the motor below its suggested idle causes many problems,
one has to basically crank up the motor to this revolution,
with everything more or less working.
You can jack up one rear wheel of a VW, pop the trany into 3rd/4th,
give it spin by hand, and start the motor. (probably turning about
"2" RPM at start-up)
Jim
Is this the old air-cooled Beetle or the new one? :-) I can't
say I've tried that -- and my car has an automatic tranny anyway.
--
#191,
It's still legal to go .sigless.
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| User: "Jim" |
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| Title: Re: Why does a starter motor in a motor car have a high current requirement? |
21 May 2004 11:26:18 PM |
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The Ghost In The Machine <ewill@aurigae.athghost7038suus.net> wrote:
In sci.physics, Jim
<lose30lbs@workformhome.com>
wrote
on 21 May 2004 18:59:45 EDT
<h42ta0ls8o9p6ourqpcm7cnb8fattc5hak@4ax.com>:
On Fri, 21 May 2004 15:59:38 GMT, The Ghost In The Machine
<ewill@aurigae.athghost7038suus.net> wrote:
In sci.physics, JohnDeCarlos
<yuetwah2000@hotmail.com>
wrote
on 19 May 2004 13:08:49 -0700
<d2005bc8.0405191208.5474bdbc@posting.google.com>:
Thanks in advance for your response
Well, a standard gasoline motor has to run at 80-100 kW, as it
turns out. Since the standard motor also has an RPM of about
800 RPM to 1,200 RPM at idle (I'd have to look), and presumably
running the motor below its suggested idle causes many problems,
one has to basically crank up the motor to this revolution,
with everything more or less working.
You can jack up one rear wheel of a VW, pop the trany into 3rd/4th,
give it spin by hand, and start the motor. (probably turning about
"2" RPM at start-up)
Jim
Is this the old air-cooled Beetle or the new one? :-) I can't
say I've tried that -- and my car has an automatic tranny anyway.
Impossible on the new Beetle. :)
Once, some co-workers and I, started a 10wheel dump-truck, pulling
an trailer loaded with 10,000bls of trac-loader, by pushing it.
The Detroit motor needed about a half-a-revolution to fire up.
Made that motor run backwards one day by accident, using a similar
technique.
Smoke pouring out the intake! :)
Ah, the good old days.
Jim
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| User: "tj Frazir" |
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| Title: Re: Why does a starter motor in a motor car have a high currentreq... |
22 May 2004 06:36:15 PM |
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I waz 20 years younger restarting a ship 2 cycle 8000 hp backwards for
reverse.
you could ,,if yer good ,,without using the starter but two people can
use the decomperssor and the fuel valva and get it going from forward to
backwards without the starter and allmost stopping it.
I have the duals off my loader and got the axle btween two logs and
boath wheels off the ground. man was I pissed ,,the tide came in .
Its still out there running ,,the exsaust and the top 1/2 of the cab and
a bit of wheel showing .
I got it chained to a redwood that went to beached that is 15 feet dia
and 100 feet long.
I tryed prying in between two logs 5 feet tall on the side ,,,no budge .
it steeers in the center JD big loader dualie .
It wount turn and now the sea ate a 150,000 loader .
thats a million usd syaoya tree too.
Im cutting it into 3 inch slabs and making one floor and a bar and
tables and chairs.
And the trim and siding ..Up on the hill in reo de janeiro .
The bandsaw is 20 feet wide up to 30 .
2 inch blade 50 thick , strung up to sound like a base fidle . I have
a mill jack that I can bolt a pice to and let the pc cut a pice shaped
,,
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| User: "The Ghost In The Machine" |
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| Title: Re: Why does a starter motor in a motor car have a high current requirement? |
22 May 2004 03:01:56 PM |
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In sci.physics, Jim
<lose30lbs@workfromhome.com>
wrote
on Sat, 22 May 2004 04:26:18 GMT
<nkkta05dfsm2mubbpoicgoqg1l93f3qlvj@4ax.com>:
The Ghost In The Machine <ewill@aurigae.athghost7038suus.net> wrote:
In sci.physics, Jim
<lose30lbs@workformhome.com>
wrote
on 21 May 2004 18:59:45 EDT
<h42ta0ls8o9p6ourqpcm7cnb8fattc5hak@4ax.com>:
On Fri, 21 May 2004 15:59:38 GMT, The Ghost In The Machine
<ewill@aurigae.athghost7038suus.net> wrote:
In sci.physics, JohnDeCarlos
<yuetwah2000@hotmail.com>
wrote
on 19 May 2004 13:08:49 -0700
<d2005bc8.0405191208.5474bdbc@posting.google.com>:
Thanks in advance for your response
Well, a standard gasoline motor has to run at 80-100 kW, as it
turns out. Since the standard motor also has an RPM of about
800 RPM to 1,200 RPM at idle (I'd have to look), and presumably
running the motor below its suggested idle causes many problems,
one has to basically crank up the motor to this revolution,
with everything more or less working.
You can jack up one rear wheel of a VW, pop the trany into 3rd/4th,
give it spin by hand, and start the motor. (probably turning about
"2" RPM at start-up)
Jim
Is this the old air-cooled Beetle or the new one? :-) I can't
say I've tried that -- and my car has an automatic tranny anyway.
Impossible on the new Beetle. :)
Damn. Not that I have (or even want) one.
Once, some co-workers and I, started a 10wheel dump-truck, pulling
an trailer loaded with 10,000bls of trac-loader, by pushing it.
The Detroit motor needed about a half-a-revolution to fire up.
Made that motor run backwards one day by accident, using a similar
technique.
Smoke pouring out the intake! :)
Ah, the good old days.
IIRC, one technique at one point to get off traintracks if the
motor has stalled was to put it in gear and crank up the
starter. This technique has apparently been mothballed --
if only because automatic trannies don't work in this mode
at all, and, the last time I had a manual (either a '76
Mustang II or an '84 Topaz), it wasn't horribly cooperative
with cranking in gear, either; apparently there was an
interlock switch. Another comment was that it was once
possible to start a car as you describe: by pushing it
and popping the clutch once it got fast enough.
Of course nowadays the best advice is probably to get out
of the car and a safe distance away. That train, after
all, weighs a heck of a lot more than you do... :-)
(It takes 1/2 a mile just to *stop*.)
Running a gas 4-stroke backwards would be a neat trick
(the explosion timing is all wrong), but it still should
be possible on diesels and maybe 2-strokes. I'd have to look.
Jim
--
#191,
It's still legal to go .sigless.
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| User: "John Fields" |
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| Title: Re: Why does a starter motor in a motor car have a high current requirement? |
21 May 2004 06:52:39 PM |
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On Fri, 21 May 2004 15:59:38 GMT, The Ghost In The Machine
<ewill@aurigae.athghost7038suus.net> wrote:
http://www.bmwusa.com/vehicles/3/325iSedan/techdata.htm
is probably as good a reference as any; BMW is good at
technical specs. :-) Unfortunately they seem to have
learned that we like inches, horsepower and lb-ft, as opposed
to cm, kiloWatts, and N-m. I'm also not certain whether
the bore refers to diameter or radius, though it's far easier
to measure the former.
---
It's the former.
Bore is 3.31", so the area is 8.33 square inches and the stroke is
2.95 inches, so the swept volume is 25.21 cubic inches and, since it's
a 6 cylinder engine, the displacement is 151.3 cubic inches .
However, they give the displacement as 2.5 liters, so that's 2500
cubic centimeters, and since there are 16.3 cubic centimeters in a
cubic inch, 2500 cubic centimeters / 16.3 cubic centimeters per cubic
inch = 152.55 cubic inches. Pretty close to 151.3 cubic inches, so
its the diameter of the bore, not the radius. :-)
--
John Fields
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| User: "Jim" |
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| Title: Re: Why does a starter motor in a motor car have a high current requirement? |
21 May 2004 07:10:52 PM |
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On Fri, 21 May 2004 18:52:39 -0500, John Fields
<jfields@austininstruments.com> wrote:
On Fri, 21 May 2004 15:59:38 GMT, The Ghost In The Machine
<ewill@aurigae.athghost7038suus.net> wrote:
http://www.bmwusa.com/vehicles/3/325iSedan/techdata.htm
is probably as good a reference as any; BMW is good at
technical specs. :-) Unfortunately they seem to have
learned that we like inches, horsepower and lb-ft, as opposed
to cm, kiloWatts, and N-m. I'm also not certain whether
the bore refers to diameter or radius, though it's far easier
to measure the former.
---
It's the former.
Bore is 3.31", so the area is 8.33 square inches and the stroke is
2.95 inches, so the swept volume is 25.21 cubic inches and, since it's
a 6 cylinder engine, the displacement is 151.3 cubic inches .
However, they give the displacement as 2.5 liters, so that's 2500
cubic centimeters, and since there are 16.3 cubic centimeters in a
cubic inch, 2500 cubic centimeters / 16.3 cubic centimeters per cubic
inch = 152.55 cubic inches. Pretty close to 151.3 cubic inches, so
its the diameter of the bore, not the radius. :-)
I live 2 miles from work. If there was a separate bike route, I'd give
it a try. On the street? No thanks.
Our city placed a painted bike route, along the curb of the same
street marked with "Truck Route" signs. Haven't seen anyone
use it yet.
Jim
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| User: "Jim" |
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| Title: Re: Why does a starter motor in a motor car have a high current requirement? |
22 May 2004 08:25:16 AM |
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Jim <lose30lbs@workformhome.com> wrote:
On Fri, 21 May 2004 18:52:39 -0500, John Fields
<jfields@austininstruments.com> wrote:
On Fri, 21 May 2004 15:59:38 GMT, The Ghost In The Machine
<ewill@aurigae.athghost7038suus.net> wrote:
http://www.bmwusa.com/vehicles/3/325iSedan/techdata.htm
is probably as good a reference as any; BMW is good at
technical specs. :-) Unfortunately they seem to have
learned that we like inches, horsepower and lb-ft, as opposed
to cm, kiloWatts, and N-m. I'm also not certain whether
the bore refers to diameter or radius, though it's far easier
to measure the former.
---
It's the former.
Bore is 3.31", so the area is 8.33 square inches and the stroke is
2.95 inches, so the swept volume is 25.21 cubic inches and, since it's
a 6 cylinder engine, the displacement is 151.3 cubic inches .
However, they give the displacement as 2.5 liters, so that's 2500
cubic centimeters, and since there are 16.3 cubic centimeters in a
cubic inch, 2500 cubic centimeters / 16.3 cubic centimeters per cubic
inch = 152.55 cubic inches. Pretty close to 151.3 cubic inches, so
its the diameter of the bore, not the radius. :-)
I live 2 miles from work. If there was a separate bike route, I'd give
it a try. On the street? No thanks.
Our city placed a painted bike route, along the curb of the same
street marked with "Truck Route" signs. Haven't seen anyone
use it yet.
Jim
Oops!
I can't believe Agent screwed up and posted my reply in the wrong
thread. So I guess it was later, and I was sleepier then I thought. :)
Oh well (copied and pasted) to "Bike physics question" where it
belongs.
Jim
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| User: "tj Frazir" |
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| Title: Re: Why does a starter motor in a motor car have a high currentreq... |
21 May 2004 10:12:32 PM |
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What STANDARD motor idles at 800 ?
my ship idles at 30 ,,,my john deere 48 A idles at 75 and 250 rpm is
max on boath.
My hurculeese 1920 40 hp starts on gas then runs on oil at 30 rpm
only.
I think it has a 10 inch piston and a 14 inch stroke with the side
push rods.
Its in a 1919 60 foot yacht .
built in nyny . mint and all original found in the baltics.
gave 100 thousand dolars
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| User: "" |
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| Title: Re: Why does a starter motor in a motor car have a high current requirement? |
19 May 2004 06:24:55 PM |
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JohnDeCarlos <yuetwah2000@hotmail.com> wrote:
Thanks in advance for your response
Does P=EI mean anything to you?
--
Jim Pennino
Remove -spam-sux to reply.
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| User: "Rene Tschaggelar" |
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| Title: Re: Why does a starter motor in a motor car have a high current requirement? |
19 May 2004 03:42:50 PM |
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JohnDeCarlos wrote:
Thanks in advance for your response
Can you imagine the pull of a little Mabucchi DC motor
operating on 1Amp ?
Rene
--
Ing.Buero R.Tschaggelar - http://www.ibrtses.com
& commercial newsgroups - http://www.talkto.net
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