[TheForge] Re: Dimmer switch as motor controller

[Mike Spencer]

> There's another way to do it with out a dimmer. Put a gate valve on
> the intake of the blower. The motor runs at full speed but by cutting
> down the amount of air it gets it will slow the blast.

Yet another way to do it:


    Plumbing:  

    ---------------------------------------------------
                                       /
    from blower -->                   +     --> to forge
                                     /
    ----------------------+     +----------------------
                          |     |
                          |     |
                          |     |
                          |  |  |
                          |  +  |
                          |  |  |
                          |     |
                          |     |

                             |  Dumps air to room
                             |
                             V


       Linkage:
                                  
                                      +
                                       \
            _                           \
      |=-------------------------o-------o
            ~                   /
                               /
                              +

       Two butterfly valves, each with a bell crank, linked together
       by a control rod.  "o"s are pivots. The ~ is any kind of
       friction doo-hickus to keep the valves where you put them.

You can cobble this together from light sheet metal and 3/16" round or
even, in a pinch, from tin cans and coat hangers.  Duct tape helps.

I did this once in a shop where I was to do several demos/workshops.
Two forges, big AC blowers with 5-speed controllers, the lowest two
positions of which offered Furious Gale and Barely Perceptable Zephyr.
No mods to the blowers themselves were allowed.  The above plumbing
made it possible for the novice participants to use the Furious Gale
setting to heat a range of smallish stock without burning. AFAIK, it's
still in place 20 years on.


In my own shop I have a fancy cast aluminum, 20" high-volume blower
from some kind of radar equipment with the 1/2HP 3450RPM motor ripped
off and replaced with an antique AC/DC brush motor.  It's worked fine
on a household light controller for 30 years.  As someone else pointed
out, I do have to crank it up to "high" (or at least "medium") to
start the motor but then it can then be throttled back to a mere
breeze if desired.

FWIW,
- Mike

-- 
Michael Spencer                  Nova Scotia, Canada       .~. 
                                                           /V\ 
mspencer at tallships.ca                                     /( )\
http://home.tallships.ca/mspencer/                        ^^-^^