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Motors

B

Brian White

Jan 1, 1970
0
I don't know if this is the right place to ask this, but I'm wondering how
drills and circular saws work?.. How they turn electricity into rotational
motion of the tool. Chainsaws, weedwackers, and such are easy - they use
internal combustion and turn that combustion energy into rotational motion
through a piston, cylinders and rods. I do not know how you turn
electricity into rotational motion in tools like a drill or a circular saw.
Brian White
 
S

Steve Cothran

Jan 1, 1970
0
Brian White at [email protected]
wrote on 5/5/05 6:44 PM:

Power comes into the tool and this causes the motor to turn, unless
you need the drill for a project that absoulely has to be done the
next morning,and it is late and there is no other drill available.
Then the drill motor merely turns electricity into heat.

I have an entry-level college physics book that explains motor therory
well, but surely there is something on the net. Try google.
 
D

Don Kelly

Jan 1, 1970
0
Brian White said:
I don't know if this is the right place to ask this, but I'm wondering how
drills and circular saws work?.. How they turn electricity into rotational
motion of the tool. Chainsaws, weedwackers, and such are easy - they use
internal combustion and turn that combustion energy into rotational motion
through a piston, cylinders and rods. I do not know how you turn
electricity into rotational motion in tools like a drill or a circular saw.
Brian White
When you have an electric current perpendicular to a a magnetic field ,
there is a force produced between the two (which is perpendicular to both).
In a motor, the field is on one part (say the stationary part as is the case
for for many small motors) and the current is in the winding on the other
(rotating) part. Then torque (rotational force) is produced causing motion
and electrical energy is converted to mechanical energy.
This is very oversimplified but it is the same basic principle that you see
in your car starter, alternator, household motors and industrial motors and
generators.
Actually chain saws and weedwhackers are more complicated machines than
electric motors.

There is a lot of basic information in a simple format on line or in pretty
well all encyclopedias and libraries as mentioned by others who have
answered.
 
B

Brian White

Jan 1, 1970
0
This is what I was looking for (see below). So, to produce torque without
an internal combustion engine, you use the same principle as an alternator
or even a steam turbine generator. I was curious why internal combustion
engines are so complicated with all of that linear force needing to be
converted to torque. I had become curious about the rotary wankel engine
and how it makes the process much simpler. Then I thought, why not use the
same principle alternators use. Alas, it is already used. Simply put, it
does not produce enough torque to be useable efficiently in cars where
tremendous torque is needed. For instance, electric powered chainsaws are
much weaker than ones that are gasoline powered with a cylinder. Now I
understand. I wonder if they will ever come up with a better way to make
engines where you don't need to convert linear forces like in an internal
combustion engine into torque. The rotary wankel engine was a step in the
right direction I believe. Any thoughts?
Brian
 
D

Don Kelly

Jan 1, 1970
0
Brian White said:
This is what I was looking for (see below). So, to produce torque without
an internal combustion engine, you use the same principle as an alternator
or even a steam turbine generator. I was curious why internal combustion
engines are so complicated with all of that linear force needing to be
converted to torque. I had become curious about the rotary wankel engine
and how it makes the process much simpler. Then I thought, why not use the
same principle alternators use. Alas, it is already used. Simply put, it
does not produce enough torque to be useable efficiently in cars where
tremendous torque is needed. For instance, electric powered chainsaws are
much weaker than ones that are gasoline powered with a cylinder. Now I
understand. I wonder if they will ever come up with a better way to make
engines where you don't need to convert linear forces like in an internal
combustion engine into torque. The rotary wankel engine was a step in the
right direction I believe. Any thoughts?
-----------
The internal combustion engine has a better power to weight ratio than most
electric motors and also elctric chainsaws are limited by their power
supply.
However, do not think that electric motors are inherently "weaker" than IC
engines as it simply is not true. Note that electric motors of the order of
100,000 HP are not uncommon.
 
E

ehsjr

Jan 1, 1970
0
Michael said:
Don't know what you mean by a "weightless" arm, but if you have a
disembodied arm trying to throw a tomato, the tomato _will_ be thrown,
but the arm will also travel in the opposite direction. Conservation
of momentum, equal and opposite reactions, etc. It is also how rockets
work in space, (they 'throw' burning fuel) even without no air to
push against. An electric motor will also work in space, but its
frame will rotate in the opposite direction.

<snip rant>

Agreeing with your point and expanding on it:

The rocket fuel does have something to push against -
the rocket. As the fuel expands. it pushes against
all sides of whatever contains it and escapes at the
vent. For the sake of discussion, say the vent is
pointing "south" and the nose of the rocket is pointing
"north" (north and south used only to indicate exactly
opposite). The fuel expands and moves "south". The same
force that pushes the fuel "south" also pushes the
rocket "north".

I suspect "weightless" was intended to mean "massless".
Maybe ??. And maybe (I'm speculating) he has the following
in mind: In theory, if there could be such thing as
a massless arm, then it wouldn't throw the tomato. F=MA
???

With a "real" weightless arm, if it can move it will
throw the tomato. As an example, consider a mechanical
arm shaped like a human arm, floating in space. In the
palm of the hand is a tomato. On the back of the hand
is our rocket from the previous example. The rocket
pushes the hand, and the hand throws the tomato.

Ed
 
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