Blown Gas Forge Control

[Medicmc]

So last week I posted pics of a Mankel forge and anvil that I found on CL. I used it a little and found that I didn't like having the forge burning full blast while I was hammering a the anvil. 

On my home made atmospheric brick forge I made an idle circuit from some brass fittins an electric solenoid and a switch. Its a simple setup and it saves gas. 

So I started thinking (I know a very dangerous thing to do) that I need  something similar for my "new" forge. It started out simple just a solenoid and idle valve, which I made, and then found that when I turned the gas low the blower motor was still going full force and would blow out the flame. And turning the gas low, reaching over to the blower door and closing it, then taking the hot metal out, then doing the reverse after the metal I was hammering cooled, seemed kinda awkward.

And so began the long electro-mechanical journey to make a control system that would lower gas usage and control the blower motor output.

Here's what I made; 

And it actually works!! 

I had most of the parts in stock, but ended up spending about $75 on items I didn't have.

Here's a closer view with labels :)

And here's whats inside :o simple right?

Here's a closer look inside.

The gas comes in, goes to a manifold that supplies the idle control vale, and the main gas control solenoid and valve, then exists thru the black hose to the forge.

On the bottom of the box is the 12 volt power supply for the blower motor, on the right side are two PWM's (pulse width modulator) that controls the high and low speed of the blower. And a DPST relay that switches between the two PWM's and controls the indicator lights. Oh and a fan to keep everything cool...and a molded hospital grade power cord!!!

When at idle the indicator light is on next to the idle control valve and the idle blower speed adjusting knob. When at full the light is on next to the full flow gas valve and the high speed blower adjustment knob. The lights get brighter or dimmer depending on the speed output.

I can now control the gas and blower from a safe distance from the forge. And have an almost infinite amount of gas output, and air input. I leave the blower door and gas valve on the forge wide open. And it all fits inside of a 8x8x4 pvc electrical box.

[BobL]

Good job medicmc,

 

I'm considering doing a similar thing with my mains gas powered forge. The big problem I have is that I need a 3/4" solenoid valve that fully opens without any gas pressure assistance since mains powered gas has so little pressure. These valves are available but they cost big bucks here in Australia and I'm trying to find a used one I can trust, or might have to make one from bits and pieces. I had an idler circuit on my previous set up, more to reduce the heat build up inside my shop when I was not working the metal than to reduce cost as the forge only costs $2.50/hour to run 

[Bigred1o1]

bobl have you though of using a ball valve with a solenoid to run the handle open and closed?

[BobL]

Yep - that one is on the drawing board.

The problem is getting a solenoid with a long enough throw, or the other design is a spring loaded handle with a short throw solenoid to unlatch the spring loaded handle.

Just trying to design something as simple as possible.

 

I have had to stop using the forge until this control is hardwired into the pluming.

If the blower stops for any reason (most likely from a mains AC power failure) the small blue (ie blown) flame instantly turns into a yellow 6+ ft diam fireball.

I really should use an air flow sensor to switch the solenoid that way if either the AC power failed or the air lines came off or the blower failed it would turn the gas off.

 

ANy good ideas would be appreciated.

Thanks

[VaughnT]

Medic, that's a fantastic idea.  I don't use a blown forge yet, but you've solved one of the main problems I've always had with them.

 

Now, the questions is, are you going to sell those units for us poor schmucks that don't understand all that stuff?

[Medicmc]

Hi BobL

Thanks. You may not need a full bore 3/4 inch solenoid. The one I used has a 3/16 orifice, before I used it I tried to find a chart or formula to find how much gas could flow thru such a small opening. The formulas I found had waaaay to much math for me to understand, so I just set it up temporarily between the tank and forge and it seem to flow enough gas to work. My advice would be to try the largest solenoid you have and see if it works...or on some home heating systems there are electrically controlled water valves that you may be able to use.

Bigreds idea would work also.

VaughnT. Thank you also. I would enjoy making these control boxes, but if I had to buy all the parts new it would cost lots of money. Probably in the $2-300 range. It looks complicated but if you break it down into smaller sections its not to bad. If you want to try to make one yourself I'd be glad to post or email you more detailed info.

[Rich Hale]

How about a foot pedal?

[Medicmc]

A foot pedal!!! holy cow i'm gonna hafta start all over again :wacko: Now ya got me thinkin...that may not be all that hard to do hmmm. I'll let you know what I come up with.

[Dodge]

A normally closed, electrically opened solenoid would shut off the gas immediately in the event of power failure. Pretty simple to wire it into the fan switch. and as Rich said, foot pedal on the fan switch.

[VaughnT]

Medic, you might want to start sourcing parts...... I think you've got something here!

 

$300 might seem like a lot, but how much would you save in fuel if you weren't constantly heating the forge?  You spend as much time at the anvil as you do the forge, round abouts, so I would rough guess a 35% reduction in fuel usage with a gadget like this.  It would probably pay for itself in less than two years if you are just a hobby smith tinkering for a few hours a month.

[Frosty]

I just have a 1/4 turn ball valve on mine and can turn it on and off without hassle. I have to leave it turned off for probably 10-15 minutes before it starts slowing heating times significantly. The forge temp has to fall below low orange before it won't relight just turning the gas back on.

 

Ron Reil designed an idle circuit for his set up, the plans are probably on his site.

 

Frosty The Lucky.

[Dodge]

Hey Frosty,

I also have a ball valve to shut off gas on both my forced air and NA forges, however, the problem of JUST shutting off gas on my forced air is that the fan is still running. That cools the forge off so quickly that I can't simply turn gas back on to re-light like I can in the NA forge (if I don't wait too long) That's why I figure a normally closed electric open gas valve hooked into the fan circuit would relight forge with flip of a switch (or foot pedal ;) ) Any thoughts?