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Q: DC Motors ( Answered 4 out of 5 stars,   3 Comments )
Subject: DC Motors
Category: Science > Technology
Asked by: joe1-ga
List Price: $25.00
Posted: 13 Nov 2002 04:12 PST
Expires: 13 Dec 2002 04:12 PST
Question ID: 106745

Question:  Can I take the motor (not the transmission) out of the
Dewalt 14.4v drill and hook it up to a regular dimmer switch (the kind
they use in houses to dim the lights) and hook that up to a 18v (or
14.4v) battery to regulate the rpm's of the 14.4v Dewalt motor?

Also, what is the technical name of the metal that tripods (camera's)
are made of?  I know they are made of aluminum but what kind of
aluminum and where can I find it?  I'm looking for a light weight
square tube metal (1.5" x 1.5") with sharp corners that is rigid.

One more..... Where can I find small (2.5"w x 4"L) 9v, 12v or 18v DC
motors that have high rpm's (1000+) and high torque (120+ foot pounds)
where the rpm's can be adjusted without using a programmable

Joe Abraham

Request for Question Clarification by bikerman-ga on 13 Nov 2002 04:52 PST
Mr. Abraham,

I have the answer to paragraph one of your question, and am looking
for information on paragraphs 2 and 3.  If I can't find information on
the last two, would you accept the answer to #1 as an answer?

Looking forward to hearing from you,
Subject: Re: DC Motors
Answered By: krobert-ga on 13 Nov 2002 07:19 PST
Rated:4 out of 5 stars
The motor from the drill should work fine at 14.4 or 18 volts. I would
only recommend it for non-continuous duty... For example, don't use it
in an RC car.  If your using it to build a robot, to drive an arm for
example, you should be fine. You probably want to add a heatsink to
the motor. In this case, some of the RC car accessory heatsinks should

As far as the dimmer switch goes... yes, it should work.  Make sure it
can handle the amperage... divide the dimmer's operating wattage by
110 volts (in the US), and you get the amperage rating... so 1000Watt
dimmer can handle 1000Watts divided by 110 volts, or about 9 amps. 
You need to check the draw (amperage) of the motor that you have to
see how much it needs. There are better solutions for speed control
(more complex though), see:

Electronics 2000

EDN Access

As far as what camera tripods are made of, it's likely to be aircraft
aluminum ("aircraft" just really designates the quality). 7075-T6 and
6061-T6 are common alloys.  If you can find "aircraft aluminum" you
should be fine.

See this references for more info on this:

Aluminum Alloys

This company carries the 1/2 by 1/2 tubing that you are looking for
(in a 6063 alloy, similar to 6061).  It's worth talking to them about
your specific application (note, I don't necessarily recommend this
company, it's just here for info.).:

Airparts, Inc.

Whether or not it has sharp corners will depend on how it's
manufactured, so your mileage may vary.

As far as your last question goes, your not going to be able to get
away from using a programmable controller because of the way that DC
motors operate. As you increase the voltage on the motor and the motor
spins to higher and higher RPM, the operating resistance goes up. 
What does this mean?  A step increase in voltage does not equal a step
increase in RPM... hence, you need a programmable controller that is
able to translate voltage to speed.

There is an affordable kit listed on this page that may be able to
help you out with the "programmable" part of the motor.

A1 Parts

As far as finding the exact motor you are looking for, this site can
provide it:

Global Spec

Unfortunately, they require you to register before giving information,
but my search yielded 76 products that should fit your needs.

Best of luck on your project!

joe1-ga rated this answer:4 out of 5 stars
Dear Krobert,

This is the first time using this Google thing so I apologize for not
getting back with you sooner.  I do thank you for your quick post and
the information you supplied.  I'm now on my way to building a
prototype that will change the world! lol

Thanks again,

Subject: Re: DC Motors
From: bikerman-ga on 13 Nov 2002 10:38 PST
(I'm posting this comment because I had already done the research
when the question was answered.  Perhaps you can find some useful
information here in addition to krobert-ga's answer.)

Mr. Abraham,

Whether or not a house dimmer switch will work with your DC motor
depends on what type of dimmer it is.  Older dimmers used to
simply be variable resistors (also called rheostats), and this
type will in fact work in a DC circuit.  However, newer dimmers
make use of an electronic component called a TRIAC.  Due to the
way these dimmers function, it will not work in a DC circuit.
Take a look at the following article on for more
detailed information on how these dimmers work:

"How Dimmer Switches Work" 

There is a third type of dimmer switch which isn't mentioned on
the Howstuffworks site, and may never have been common in
households, but was used in other places.  This type of dimmer
uses an electrical property called inductive reactance, and it
also only works in AC circuits.

If you have an ohmmeter, you can easily test to see if your dimmer
switch will work.  Just hook the ohmmeter leads to the dimmer
switch terminals, and turn the dimmer knob.  If the resistance
varies, you can use the dimmer in your DC motor circuit.  If your
dimmer switch is the type that won't work, you can purchase a
variable resistor (or potentiometer) from your local electronics
supply store.  I've listed a couple of sources of electronic
components in the Additional Links section below.

Camera tripods are made from a variety of substances including
aluminum, wood, and carbon fiber.  I was unable to find any
detailed information on the type of aluminum used, but I've listed
some companies which sell tubing made of various materials:

Brunner Enterprises Inc. distributes standard and custom aluminum
extrusions and fittings.  Here is a link to their homepage:

Brunner stocks square aluminum tubing (1-1/2" to a side and 1/16"
thick wall).  The tubing is 12ft long, but they will cut it for
shipment via UPS.  Here's the URL to the page (scroll down to
almost the bottom of the page to see the table of square tubing

The Metal Specialty Company manufactures tubing from a variety of
metals (aircraft aluminum, titanium, carbon steel, stainless
steel, nickel steel, and more) in a variety of shapes.  They have
a minimum order of $50.00.  Here's their URL:

American Modern Metals Corp. manufactures aluminum tubing (among other
things).  Here's their URL:

Just in case you would like to use a composite (such as carbon
fiber), here is a manufacturer of such products (Note that they
don't appear to stock square tubing, and I'm not even sure how
well carbon fiber would do in that shape.  Also, I have a carbon
fiber bike and have been told that petroleum-based oil/grease will
destroy the carbon fiber bonding agent--something to keep in mind.):

"CURRENT, INC. is a leading manufacturer of laminated sheet, rod,
tubing, spacers, and stand-offs in various grades and sizes."

I hate to be the bearer of bad news, but I don't think the motor
you are looking for is electrically or structurally possible.  A
motor running at 1000 RPM and developing 120 ft-lbs of torque
would, according to my calculations, have a power output of
approximately 22.8 horsepower.  At 18V and 100% efficiency, that
would be approximately 947 amps.  That's a LOT of current!  Here's
how I got there:

Power = Torque x angular_velocity
angular_velocity = (1000 RPM * 2 * pi) / 60 = 104.7 radians/sec
Power = 120 ft-lbs * 104.7 rad/sec = 12566.4 ft-lbs/sec

1 HP = 550 ft-lbs/sec = 746 Watts

12566.4/550 = 22.8 HP = 17044.6 W

Current = Power / Voltage, so

17044.6/18 = 946.9 Amps.

I talked to a man from Bardac Drives who knows about motors, and
he estimated that a motor with that power output would be
approximately 12 inches in diameter and 18 inches long.  He also
noted that the shaft alone would have to be 1 to 2 inches in
diameter to withstand the 120 ft-lbs of torque.  The man from
Bardac said that even if such a motor existed (which he didn't
believe to be possible), the cost would be exhorbitant.  Bardac
manufactures AC and DC drives in a wide array of sizes and
applications, but nothing in the 9-18 Volt range.  Still, you
might want to check out their website at

Note that if you were willing to increase the voltage, you could
get the same power output with much lower current.  That's usually
desirable because it is current that generates heat, and any
generated heat is wasted energy.  The motor is still going to be
much larger than you wanted, though, as far as I can tell.

Here is a page which lists many suppliers of DC Motors
(free registration is required to actually view the information): also lists manufacturers of DC (and AC) motors
in their Buyer's Guide (this site also requires free

Additional Links:

HI-TECH PROFILES, INC. manufactures plastic extruded products:

The following categories in the Open Directory may be of interest
to you:

Business: Industrial Goods and Services: Materials: Metals: Steel:
Pipe and Tube

Business: Industrial Goods and Services: Materials: Metals: Aluminum

Business: Industrial Goods and Services: Materials: Composites

All Electronics Corporation is a supplier of new and surplus
electronic supplies:

HOSFELT Electronics Inc. also sells electronic supplies:

Search Strategy:

Open Directory Search: tubing

Google Search: metal tubing supplier

Howstuffworks Search: dimmer

I hope this information is useful to you,
Subject: Re: DC Motors
From: joe1-ga on 13 Nov 2002 20:53 PST
Dear Mr. Bikerman,

This is the first time using this Google thing so I apologize for not
getting back with you sooner (still not sure if you will receive this
message).  I must say I was pleasantly surprised by your comprehensive
"comment".  It was very professional and very thorough, thank you very
much.  I feel bad because much time was put into your comment and I
don't know how to pay you for it.  Please let me know how I may
compensate you for your this.

Thanks again,
Subject: Re: DC Motors
From: bikerman-ga on 14 Nov 2002 05:04 PST
Mr. Abraham,

No compensation necessary (or possible--comments are free).  I enjoyed
doing the research and didn't want it to go to waste.  I learned a lot
from my searches, and am glad that the information was useful to you.

Best wishes,

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