Furnace Exhaust Fan

[RoadmasterK]

I am new to blacksmithing and to the forum. Just completed this forge before Christmas, and my main challenge so far has been air supply. I started off with a borrowed Bufco hand crank blower, but it is very worn out so I was hesitant to use it much. 

My plan is to make a bellows eventually, and/or buy a good hand crank blower. I really like the physical aspect and the contolability of supplying air by hand. Until that happens, however, we gotta make fire so this is my current set-up. 

This is the exhaust fan from a natural gas furnace.  It has way too much power, so I have the intake almost completely taped off. I also put it on a dimmer switch. Not sure if that is a great idea, but motor is staying cool so we will see how it goes. It can still go from too cool to blowing the coke out of the firepot with a tiny adjustment on the dimmer switch lol. Certainly not ideal.

Happy forging everyone, and thanks so much for all the great information posted here.

 

[Frosty]

Welcome aboard, glad to have you. Nice looking forge you have there, well done.

Yeah, that's WAY too much blower and your problem restricting the air intake to control it is the motor is cooled by allowing part of the blower's intake to pass through the motor and you can't block it off.

If you wish to  use this blower rather than replace it with a smaller one you'll need to make a gate valve on the output side or just aim the blower away from the air supply duct by degrees.

This is the same issue as using a blow drier (under $5 at a yard, etc. sale) or a mattress inflater blower, available at Wall Mart new for $13 USD and much less in the late summer closeout sales.

I like the mattress inflaters, I had to stop picking them up at yard/garage, etc. sales, $2 USD. was my max. 12v dc  is the most common and gives you real portability but the 120v ac models are much handier in or near an outlet. These also put out WAY more air than necessary and aiming them away from the air supply duct works a treat.

Bear in mind I don't burn coal often it's too hard to come by here, I burn naturally aspirated propane mostly.

Frosty The Lucky.

[ThomasPowers]

Is the dimmer switch based on a triac or a rheostat?  Is the motor a universal motor?  A universal motor will work with a rheostat. Other motors generally have much reduced lifespans with dimmers of either sort.

It's usually easier to waste air; like keeping the ash dump open, than to mess with a motor.

[RoadmasterK]

Thanks guys. Really not sure on the type of motor or dimmer, but you are probably right on it being better to dump air than to cut motor speed. The first time I used it I had the pipe blocked on the pressure side and was regulating it further with the ash dump. Having that dust storm under the forge isn't ideal either:)

This will just inspire me to get at those bellows sooner than later!  But for now I am really enjoying making tools. A cutoff hardie, a square drift, and one pair of tongs so far... Not gonna show you the tongs..haha

 

[FlatLiner]

You could ditch the dimmer switch and unblock the air intake if you do something similar to what I have done. I have a furnace exhaust fan that pushes up to 500 cfm so I put a t in-between the airgate and the blower so that when I turn down the air the excess air is exhausted out the open t.