Making an electric blower adjustable

[eyrian]

I have decided to fire my coal forge using an electric blower. To get it adjustable, I've considered two methods

1) Building something like this; or
2) Having a sliding cover over my blower's intake that restricts the air flow.

Does anyone know if the first thing will actually work? It says it's designed for an electric motor, but I'm far from being an electrical engineer.

Are there any downsides to physically restricting air intake?

[Neal L]

If the motor doesn't have a start winding then you should be able to use a rheostat to control the speed. They a fairly inexpensive at Lowe's or Home Depot. You could restrict the intake or you can use a blast gate between the blower and forge which is what i have on my forge. McMaster-Carr has them

[Frosty]

When it comes to electronics I'm a first class weldor so I don't know what the diagram says. However, I do know the electronic cycle controlers work fine with induction motors but power reduces with RPM.

Restricting intake works fine as long as the motor doesn't rely on blower air for cooling.

A bypass in the outlet is another if more complex option that allows plenty of air for the motor. Bypassed air can be directed up the flue to increase draft.

Frosty

[Covforge]

Why not put an air gate in the line, it won't hurt a thing and is simple to adjust.
Travis

[Dutchmancreek]

I use an air gate that I bought from Centaur Forge. Simple and works well.

You might also consider adding a spring loaded foot switch, so that the blower is shut off when you step away from the forge. After you forget to shut off the air and burn up some steel, you'll find it handy. I made one from the foot switch that came off an old sewing machine.

Steve

[irnsrgn]

I just use a butterfly valve I made to go in the pipe, it looks like the manual choke on a carbuerator.

[blksmth]

When you buy a Centaur Forge PB50 blower you get with it a speed control which is a heavy duty light dimmer switch normally used to dim lights. Most folks that use that blower only use the speed control, infrequently, to slow down the speed of the motor, when possible, to keep the noise of the motor down to a more comfortable level. The electronic speed controller works, but the motor reacts too slowly for most folks. Everyone I know uses an additional aluminum & galvanized sliding gate in the output tube as a main air controller. Centaur Forge sells sliding gates for around $12 (been awhile since I checked the price). They can also be purchased from woodworking supply stores as a damper for sawdust collection systems. Maybe they can be purchased from the local furnace supply outlet. I made a sliding gate for my permanent forge. I put the Centaur sliding gate on my portable forge. I'd never make another one considering the price of the purchased sliding gate and since it works exceedingly well. I have a pivoting plate that covers the input of the fan on my gas forge. It works well also, at least for that purpose, but wouldn't work well for my coal forge as the fan is to low and inconvenient to reach. The sliding gate on my coal forge works off a push pull rod right under my forge table next to the firepot. It is handy.

[Covforge]

I suggested an air gate but any kind of valve will work. I set mine and very seldom move it. I also use a foot control, saves a lot of coal.
Travis

[ApprenticeMan]

Thomas Powers once mentioned, that it is better and easier on the blower motor to restrict the amount of air going into the blower, rather than restrict the air coming out of the blower. I have my forge setup so, i set the blower at whatever level of airflow I need, then have an ON/OFF air dump valve, on when heating off when you step over to the anvil to hammer.

[matt87]

Yo can make a sliding air gate very simply: IronFlower Forge - Construction

Although this on is implemented on the output (blow) side of the blower, there is nothing to stop you doing it on the intake (suck) side.

Something I've been interested in but not yet needed is a blower muffler. I read this in The Artist Blacksmith by Peter Parker-Pearson; build a box from boards (lower density is probably best) and line it with something like rockwool (quite loose fibreglass insulation). Put the blower inside and have the intake hole reflexed; rather than just a hole, build an extra insulated enclosure at 90 degrees to the axis of the hole. With this setup you can reduce noise, easily add an intake filter and, crucially for this thread, add an intake control gate, irresepective of how your blower is built.