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What do you guys use for air flow control?

I use to just place a piece of plywood in front of the air intake of my squirrel cage blower, but now I've chaged blower, and it's not possible to do that anymore.

Pictures welcome!





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When using a small shop vac blower, I use a variable transformer...this particular shop vac motor is kept cool by another fan in the motor..so it does not depend on the blower air for cooling. When using a vacuum as a blower, the dust container ( most of the volume of the machine) must be removed.....should that volume ever fill with gas it may explode and be quite a hazard. To get really low flow rates I do place aluminum tape over the intake and vent some of the output to the atmosphere. This combination allows me to run a gas forge from 650 C to higher than welding heat and use it for some heat treating. I will post a photo of this unit to emphasize the safety advantage of discarding the dust container.

I am going to try to reach an even lower temperature and temper quenched steel in the exhaust of the forge.


I also use a regenerative blower when the need for higher pressure comes up ( smaller charcoal, tall narrow furnace...ore added in a manner which may obstruct the air flow). The regenerative blower

motor is also cooled by a fan in the motor housing and can be choked at the intake..I just have a simple gate valve at the intake. Choking at the intake (not the exhaust) allows the motor to run faster under less load and stay cooler.


A very effective method for changing air flow is to pipe the air to the forge ( furnace via a "T") say it is 1.5" at the T...one of the legs of the T vents to the atmosphere via a 1.5" diameter pipe about 18" long...a 1.5" wooden dowel is cut at a severe slant and when that dowel is all the way in, the escape of air is blocked..as the dowel is pulled out air begins to escape from the angled cut and a simple adjustable "valve" is in place...about a 10 minute job. It does not take much imagination to expand this to sort of copy the motion of the bellows used by the Japanese sword smiths....push in = high volume to the fire pull out low volume to the fire...if you want to work harder it can be spring loaded both ways.



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Here is my current tuyere set up.
I use a ball valve set up, just past the tuyere .
Because my valve is usually mostly open I added a return air flow to blow the unused air onto my copper tuyere, helping with cooling.


It works VERY well, through many smelts.





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I use a blown gas burner, with a metal cased fan. I use magnetic sheet material (I get it from the local craft store, they use it for making stick on signs). I cut a piece just oversized and slap it on the intake of the fan.



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