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I Forge Iron



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Hello there, or 'Ow do?' as we say round here :wink:
I recognise a few names, & hope there isn't too much groaning :D
I'm a kind of foundryman, in as much as I cast molten metal. Well, to be honest its silver, although I'm looking at maybe doing some larger sand casted pieces in Aluminium...i've 'found' Gingery.
I'm also genuinely interested in blacksmithing (but REALLY haven't the space, for the gear or for peace from the neighbours) and am a bit of a scrap hound in my spare time.
Hope I can ask you folks some questions.....
I sniffed out an air blower, what I think is a squirrel cage type. The 'cage' is made by Airflow Developements Ltd the motor by Brook Crompton. Both are uk companies, any other brits out here? It came from a kodak processing machine. Thing is I'm not a sparky, but I have jerry rigged a dimmer switch into it and it does control the speed of the 240v motor, but theres a spot just after half way round on the switch where the motor slows right down again then as you go by this 'dead' spot it jumps back up to full tilt. I thought if the motor wasn't compatible with the dimmer type switch it just wouldn't work?
As a bonus it also has heater elements in the two 'barrels', it was basically an industrial hair dryer :D . I want to try and utilise them for preheating but dont want to fry them through ignorance so that'll have to wait :)
Anyhow thanks for letting me ramble on. I look forward to hearing your ideas.

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hmmm.... wish I knew a little more to be more helpful to you, but I doubt it's the switch. I suspect that the motor is not a variable speed motor, and that is how I'd expect the motor to behave if it isn't variable speed. A dimmer switch is nothing more than a variable resistor, so you are putting a load in series with the motor... basically dropping voltage before the current gets to the motor. So I think you might be trying to run the motor at less than it's rated voltage and at some point you are at risk of burning it up.

It is probably worth a little research on your part to match a motor and controller if you want variable speed.

However, a simpler solution is to run the blower at normal speed and put a gate in the hose between the blower and your fire. Not only is this safer for the blower, but it allows you immediate and finer control of the air flow. Variable speed motors have to ramp up to speed, and coast to slow down. The damper simply throttles or widens as fast as you move it.

If you don't want to make your own slide or butterfly damper (which are pretty easy, really), you can buy different sizes online or from hardware stores where they sell dust collection systems.

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Hi Ed thanks for the advice,
I had the dimmer laying around, as part of my soldering iron/wax pen set up. I'd read about folks controlling motor speed that way and just wanted to try it. A butterfly or some other kind of choke is a definate possibility, although I'll rig it for the air inlet instead of in the tubes, less work on the motor that way. Its a 240V 50hrz motor and basically just wired to a plug and then into the mains. I'm REALLY not much of a sparky :lol: :oops:
If overheating the motor is a risk I can use one of the hoses pointed back at the motor to cool it.
Anyhow if anyone out there is, any other opinions will also be most welcome.

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There is no harm in putting the damper on the outlet. The motor doesn't work any harder, at least according to everyone I've asked that deals with motors and air flow. I've seen the damper on either side, but it seems more effective as a gate for the forge on the downstream side of the blower. My blower is also a 240V motor... but at 60~ we got more hertz than you. :D

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