Blower Volume

[SmoothBore]

I've just acquired a coal forge, with a blower that was originally made to operate off a line shaft.

The problem is, ... that I have no clue what speed the line shaft operated at, ... or what RPM range, the blower requires.

I have NO EXPERIENCE with coal forges, and wouldn't know a properly aspirated coal fire, if it was burning my backside.

ANY information about blower requirements, ... or performance, ... would be helpful in flattening out the learning curve, and save me a lot of trial and error.

[Larry H]

blowers like buffalo usually have 3450 rpm motors, high output cfm's but I have seen blowers with 1750 rpm, clean it well and check for cfm number, a blower with a 400 cfm output needs 3450 motor

[bigfootnampa]

For a smaller fire most hair dryers put out about the right amount of air for a coal fire. You don't need a lot of air unless you are running a big fire. A small salvaged appliance motor would likely serve your needs.

[Dr Dean]

A line shaft typically runs at 400 rpm. What gave the diffrent speeds of output was the size of pully that was mounted on the shaft. So a 6 inch pulley would make 7539.6 inches per minute and if your driven pulley was say 2" you would get 1200 rpm on the driven shaft. To figure speeds I take Pi (3.1415) X diameter = circumfrence do this on both pulleys and write it down. Take P1 (drive) and multiply circumfrence= linear per minute (inches if you used inches to figure your circumfrence). Then take linear per minute and divide it by P2= rpm.

[Steve Sells]

blowers like buffalo usually have 3450 rpm motors, high output cfm's but I have seen blowers with 1750 rpm. Clean it well and check for cfm number, a blower with a 400 cfm output needs 3450 motor

where did you got those numbers? the 3450 or 1750 rpm is because of AC having 60 cycles for incoming power in the states. The blades being turned size and shape determine the CFM being moved. both these motor speeds Can produce the same CFM with various fan blades being used. also I very much doubt a line shaft was turning anywhere near 3450 rpm.

[Francis Trez Cole]

A picture would be great I have seen ones with hand cranks and belts but not one that ran off a line. would like to see it

[Glenn]

You build the size fire you need to do the work at hand. More air makes a bigger fire, less air makes a smaller fire. The amount of air (not the size of the blower) determines the size fire.

[SmoothBore]

Thanks for the info.

At this point, the resurrection of this old Forge, will most likely be a "Winter" project.

It's currently disassembled, and resting upside down, on a pallet, ... but as soon as I get it back together, pictures will be forthcoming.


In a very general sense, is it safe to say that a "variable speed", or "multi-speed" blower motor, is the most desirable way to deal with the Blower Volume issue ?

[John B]

Thanks for the info.

At this point, the resurrection of this old Forge, will most likely be a "Winter" project.

It's currently disassembled, and resting upside down, on a pallet, ... but as soon as I get it back together, pictures will be forthcoming.


In a very general sense, is it safe to say that a "variable speed", or "multi-speed" blower motor, is the most desirable way to deal with the Blower Volume issue ?

Not in my opinion, a slide valve is my preferred option

[SmoothBore]

Yeah, ... a Gate or Damper type valve would be a simple, effective solution, ... but on this unit, the blower bolts directly to the tuyere.

Still, it wouldn't be a big problem to introduce a sliding Gate between the blower and the tuyere.

I'll surely give that idea some more thought.

[John B]

Yeah, ... a Gate or Damper type valve would be a simple, effective solution, ... but on this unit, the blower bolts directly to the tuyere.

Still, it wouldn't be a big problem to introduce a sliding Gate between the blower and the tuyere.

I'll surely give that idea some more thought.

It is relatively simple in that situation, all you need are two spacer plates, and a slider plate with a large hole in to fit loosely between them, fit a handle mechanism to the slider plate if you need to.

Sorry this pic is blurred but it may help illustrate the point, mount it horizontally and it is more likely to stay in place when in use.



These two are slightly better quality pics.



It may be advisable to put in a spacer tube between the forge tuyere and the slide vale arrangement as this helps keep heat transference from the forge to the fan

If you use the same thickness of material for the spacer plates and the slider, cut some shims from a cold drinks can or similar and use these to allow the slider to work easily.

[Tom Allyn]

At this point, the resurrection of this old Forge, will most likely be a "Winter" project.

In a very general sense, is it safe to say that a "variable speed", or "multi-speed" blower motor, is the most desirable way to deal with the Blower Volume issue ?

First off, don't wait for Winter. Get it done while the fire is still in you. Stuff happens and things don't get done. Better to move on it now rather than later.

And in regards to the "variable speed", I think it's a good idea. I'm a noobie to blacksmithing but I like having variable speed. I have a rheostat controlling my blower. I can give it a low blast for a slow even heat on small stuff or crank it up for heating larger stock. It's a good idea to have as much air as you could want at your disposal.