Subject: Re: 12V fan source

From: [email-masked] (Nick Pine)
Date: 22 Mar 1995 04:05:53 -0500

Michael R. Michovicz <[email-masked]> wrote:

: Hey, this sounds great! I never thought of making my own fan, from parts...
: Could you post the part numbers of the motor and fan blade, and Berg's part
: number and phone number?

: Does the fan blade have efficient, solid aerodynamic surfaces, vs bent sheet
: metal? I see a TM92MTR2270 1200 rpm, 24 VDC 0.2A no-load motor on page 13 of
: my 1995, Issue 1, H & R catalog, with a 3/8" shaft, with a metal 1" diameter
: metal cog pulley attached (pressed on?) to the shaft, and an optical shaft
: encoder on the back, for $17.50, that weighs 4 lbs.

The Grainger fan blade I used was the 3 wing aluminum exhaust fan blade 
2C358 @$11.90

The motor is a Pittman PM reversible rated at 30.3v. I have used this 
motor at voltages down to about 1 to 2 volts at which point it is 
overcome by its own friction, but the torque (and hence the speed) is 
quite proportional to the input voltage. I got these so long ago that I 
don't have the catalog anymore, but I have since found another source for 
surplus motors that you might want to check out. The are:
	Servo Systems Co.
	115 Main Rd.
	Montville, NJ 07045-0097
	(201) 335-1007
	(800) 922-1103

For example I see in there a Clifton Precision 24 VD 42 oz-in 
(continuous) motor 2.25" diam. X 5" L for $12.50
(Many, many others)

Sorry I have my gear catalogs packed. See if you can get Phone #'s for
	Winfred M Berg
	  -or-
	Stock Drive Products
	  -or-
	(I can't remember some of the others, ask an ME or machinist)

: Seems like most fans have the motor mounted on a metal X of some sort in the
: middle... I guess you could squeeze the motor between the flat sides of two
: 1 x 3's, with a couple of long drywall screws. Is that what you did? 

I drilled a hole the diameter of the motor in a piece of hardwood, and
sawed a little slot in it, then put in a long bolt and nut to tighten it
up.  Then I attached the block to the 1X3's and mounted it in a larger 1X4
frame. 

: >I measured the voltage and current in the setup yesterday - 13.04 v,
: >drawing 1.34 A. The fan meanwhile blows at a pretty good clip all day long
: >when the sun shines. (No idea of CFM, although I could calculate this from
: >the RPM -- the motors allow the addition of an optical encoder on the back!)

: Nice... I guess you could calculate the CFM, knowing the fan blade pitch?
: Or measure the average air velocity coming out of the fan, as you traverse
: the output circle, with a Grainger/Dwyer pith-ball windmeter, and multiply
: by the fan blade swept area.

Graingers gives CFM at several RPMs for the fan in question. I would just
interpolate... 
  
I tried to post, but it came back; we don't have alt.solar.thermal yet on 
my internet provider -- I've been bugging them to get it.

Feel free to post this reply if you want to. Sorry I didn't have more 
info at my fingertips, but I'd like to keep the conversation going if you 
want to.

Mike Michnovicz
[email-masked]