Forge blower idea: good or bad?

While choking the blower on the input will work, it makes the blower starved, and thus has lower pressure. A gate on the output keeps the blower ar full pressure all the time.

Both will work, but the manifold valve/gate will allow more pressure, regardless of the air flow volume.
 
Geez yeah, glad you asked, really bad idea, especially for a ribbon burner.

Ribbon burners require much higher pressure than traditional blown burners, to the point that most blowers than work fine for such, will not function, or be very dangerous to use for a ribbon burner.

Not only that, but there's almost zero advantage for you to build a ribbon burner in this circumstance. It's a highly specific type of burner, for a highly specific type of forge, that you only use, if you know you need it. How do you know? Apologies for being enigmatic, but you'll know when you do. Too much hype and popularity surrounds them currently. They're a waste of time, effort, and unnecessarily risky for most smiths.


Also, choking a blower at the intake will destroy a blower much faster, than it would die from appropriate use. The Kayne and Sons blowers for example, will last decades if used with a gate valve and disconnected from a hot forge after it cools (I pull mine off at around 1200 degrees), to keep hot forge air from backing up into it and cooking the motor and bearings. Dampening at the intake reduces the input air the the blower needs to keep itself cool, and causes different stresses on the whole assembly than they're designed for. Backpressure on the other hand from a gate valve is no problem.


Just build a standard blown vertical or horizontal, and buy a good blower from Blacksmith's Depot.
 
Fwiw, For guys using salvaged blowers.
Some centrifugal blowers are expecting backpressure in the system its was originally designed for. Removing that restriction can cause its motor to overload.
Probably not much issue for guys cobbling up a small forge, Just something to be aware of.
Can be a problem if reusing furnace blowers and the like to ventilate a shop for example.
 
So your saying an intake damper is wrong. What if your blower came from the factory with one. And the motor is isolated from the blower section?
This is mine, the red thing is a slide damper. It’s sized do it never closes off the entire opening.
Photo%20Dec%2017%2C%204%2048%2022%20PM.jpg
 
Lieblad said:
Bounce House blower is HUGE for a knifeforge. We just use hairdryers to blow gassers.
Buy several at thriftstore for a few dollars. With daily use, Some will last a couple years, others a few months. A wrap of duct tape seals it into the blower tube. Its not rocket science.
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If hairdryers works , this will work too .It is from my first gas emission control ............works on 12V .

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JT;

Blacksmith Depot blowers come with them, yet even they will tell you, that you're better off using a gate valve. It used to even say so on the page, not sure if it does anymore.


You can slow down your grinder motor with a VFD, but every manufacturer will tell you, that even the VFD "rated" motors will have less longevity doing such, although the VFD "rated" ones will be less affected than the non-vfd rated ones, and the "VFD Ready" ones, that have fixed fan speeds independent of spindle speed, are the only ones they warranty for use with a speed controller.


I've seen numerous premium blowers die with dampers after a couple years of use, and I've yet to not "hear one" when coming into a shop with a blown forge utilizing one. I'm running 5+ years, full time, making Damascus commercially on a couple of mine, and they make zero noise. However, I use gate valves, and I remove the blowers (the air intake on my forges are "slip" fit for the blowers), after the forges cool to about 1200 degrees F.



I can't point you to any literature, so take it for what it's worth. However, I'd lean more toward the assumption that a blower manufacturer without any implicit warranty will "make whatever you want" versus "if it's there, it must be made to utilize it" in this case.
 
Is that a Cadillac Blower ? Nice... They are the best. I have one from about 1940 what still runs great.
JTknives said:
So your saying an intake damper is wrong. What if your blower came from the factory with one. And the motor is isolated from the blower section?
This is mine, the red thing is a slide damper. It’s sized do it never closes off the entire opening.
Photo%20Dec%2017%2C%204%2048%2022%20PM.jpg
Click to expand...
 
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javand said:
Geez yeah, glad you asked, really bad idea, especially for a ribbon burner.

Ribbon burners require much higher pressure than traditional blown burners, to the point that most blowers than work fine for such, will not function, or be very dangerous to use for a ribbon burner.

Not only that, but there's almost zero advantage for you to build a ribbon burner in this circumstance. It's a highly specific type of burner, for a highly specific type of forge, that you only use, if you know you need it. How do you know? Apologies for being enigmatic, but you'll know when you do. Too much hype and popularity surrounds them currently. They're a waste of time, effort, and unnecessarily risky for most smiths.


Also, choking a blower at the intake will destroy a blower much faster, than it would die from appropriate use. The Kayne and Sons blowers for example, will last decades if used with a gate valve and disconnected from a hot forge after it cools (I pull mine off at around 1200 degrees), to keep hot forge air from backing up into it and cooking the motor and bearings. Dampening at the intake reduces the input air the the blower needs to keep itself cool, and causes different stresses on the whole assembly than they're designed for. Backpressure on the other hand from a gate valve is no problem.


Just build a standard blown vertical or horizontal, and buy a good blower from Blacksmith's Depot.
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I appreciate the input. I've pretty much already decided at this point to put the ribbon burner idea on the shelf, in lieu of just a simpler blown burner.

Lookin at this motor, as I can find one for about $50. Thoughts?
https://www.amazon.com/Dayton-1TDP3...pID=31qBAoAeF5L&preST=_SX342_QL70_&dpSrc=srch
 
I have used those type blowers on burners, and they work OK for small to medium forges. They have a squirrel cage blower, which isn't as good as a centrifugal blower, but the one you show will work. fine for most forging tasks.

I have built a couple two-stage PID controls with those because the can be set to drop the speed at the LOW setting. You can read more on that in the PID control burner sticky.
 
knife to a gunfight said:
I appreciate the input. I've pretty much already decided at this point to put the ribbon burner idea on the shelf, in lieu of just a simpler blown burner.

Lookin at this motor, as I can find one for about $50. Thoughts?
https://www.amazon.com/Dayton-1TDP3...pID=31qBAoAeF5L&preST=_SX342_QL70_&dpSrc=srch
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As Stacy said, they'll work, but they're not optimal IMO.

I a very similar one on my first vertical blown forge, and it was just barely powerful enough. Fine when the liner was fresh, but after it started getting destroyed it would barely keep up, and this wasn't a huge forge by any means.

I'd highly recommend just getting this one, yes it's twice as much, but it's more than twice the blower, and will likely last more than twice as long (probably more like 10x), if treated correctly. https://www.blacksmithsdepot.com/products/forge-fan-fuel/blowers/gas-forge-blower-2.html

Get a 2" gate valve, and a needle valve for your gas input, and you'll have a highly tune-able, very versatile burner.

blacksmith's depot only sells a kind of flimsy "air gate" that works great for a coal forge, but not so good for a propane one. So I'd check with a local industrial pipe supply (that's where you're likely to buy the 2" BIP (black iron pipe) you need for the rest of the burner, and they should be able to get you a threaded 2" gate valve. If it's much more than $50 or so though, let me know and I can try to find you one on ebay. You'll need a couple of 2" "nipples" (threaded on each end), maybe 6" long, an elbow, and a bell reducer, from 2" to 1.5" and then a 1.5" nipple, where the burner goes into the forge.

You'll also need some smaller fittings for the gas input, at a minimum a 1/2" ball valve where the gas line comes in, but I recommend using a ball valve (shutoff) and a needle valve for tune-ability. You'll either have to tap some portion of the pipe past the blower gate valve (on the forge side), for gas input, or drill a hole out and weld a black iron fitting into it (this is the easiest).

All of this you'll have to do regardless of a standard blown burner or a ribbon, the ribbon just adds more complexity.
 
"....You'll also need some smaller fittings for the gas input, at a minimum a 1/2" ball valve where the gas line comes in, but I recommend using a ball valve (shutoff) and a needle valve for tune-ability. You'll either have to tap some portion of the pipe past the blower gate valve (on the forge side), for gas input, or drill a hole out and weld a black iron fitting into it (this is the easiest). ..." - javand

Instead of welding/tapping, I just use a "Tee" and put a 1/4" bushing in the side port. I also use 1/4" ball and needle valves as you suggest. 1/4" hoses and piping is plenty enough for any normal size forge burner running on propane.
 
Stacy E. Apelt - Bladesmith said:
Instead of welding/tapping, I just use a "Tee" and put a 1/4" bushing in the side port. I also use 1/4" ball and needle valves as you suggest. 1/4" hoses and piping is plenty enough for any normal size forge burner running on propane.
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As someone who will fire up the welder for almost any reason, i still gotta agree with Stacy here. The T and bushing solution is dead easy and takes no time.

As to needing more than 1/4” if you keep the pressure high for the flow rate (in other words, a smaller nozzle for the gas) my understanding is that you get a more complete gas mixture. I would suggest that you could get by woth something FAR smaller than 1/4” for any forge burner and be fine. Though this is only for your nozzle. You would still want 1/4” pipe prior.

Venturi burners use very small nozzles for a given flow rate (required to the venturi effect to draw enough air), and consequently operate at a higher pressure. While this isn't required in a blown burner, it technically should improve mixture rate.

I am not sure it is really worth experimenting with (though I may if I get bored), but it does mean that you don’t need to worry about using 1/4” fittings for the gas.
 
The mix on a blown burner is due to gas mixing, thus the mixing chamber. There is no need or real advantage of injecting the gas stream into the air stream. Actually, it could cause turbulence, which lowers flow. I know that 1/8" pipe would work perfectly fine if you had a bunch of stainless 1/8" gas valves sitting around that you bought at a surplus auction really cheap (which I did).

1/4" allows using easily available fittings, especially the gas quick-connects from HighTempTools. HTT&R carries all the valves, hoses, regulators, etc.
 
Stacy E. Apelt - Bladesmith said:
The mix on a blown burner is due to gas mixing, thus the mixing chamber. There is no need or real advantage of injecting the gas stream into the air stream. Actually, it could cause turbulence, which lowers flow. I know that 1/8" pipe would work perfectly fine if you had a bunch of stainless 1/8" gas valves sitting around that you bought at a surplus auction really cheap (which I did).

1/4" allows using easily available fittings, especially the gas quick-connects from HighTempTools. HTT&R carries all the valves, hoses, regulators, etc.
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Agree. As I said, it would probably not make much diference, but turbulance actually serves to improve mixture, and there is no reason laminar flow would be desirable in a burner. Sure you would get a touch of extra drag, but it would likely be imperceptible, especially considering the pressure diferential your blower is pushing.

In fact, our blown forges aren't wildly different than a jet engine in principal, we just drive them a little bit differently. In a jet engine, turbulent flow is prefered in decelerated sections as it assists in fuel intermix and delays boundary layer separation (less important for us, but still nice because it would increase the efficiency of the defuser/exhaust). Now we don't run liquid fuel, so the propane intermixes more easily, and the vibrations and noise the burner makes, combined with the centrifugal blower guarantee that your flow through the whole system is turbulent.

If we could have laminar flow, it would benefit us for the flow upstream of the gas nozzle. there it would decrease parasitic drag allowing a smaller blower. That all being said, this is one of the two big reasons we use blowers instead of other fans. The high static pressure of centrifugal blowers allows us to be liberal with our airflow ducts without really caring. It also allows us to overcome the back pressure from the combustion. Either way, turbulence isn't really a problem. Neither seemingly is fuel/air mixture from what I can tell.
 
I comletely agree. I have placed a half-twist of titanium sheet in the mixing chamber to cause toroidal turbulence, which goes down the burner tube and into the forge as a twisting flame. It worked very well for complete mixing. However, for the purposes of a knife forge it makes very little ( if any) difference.

I also agree that the bigger and better the blower, the better the whole burner.
 
I have no knowledge of them, but would an oil furnace burner fan minus the injector provide enough air pressure?
 
Jesse Latham said:
I have no knowledge of them, but would an oil furnace burner fan minus the injector provide enough air pressure?
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Easily big enough. You will have to choke its output for a knife size forge.
Fwiw, you can use the entire oilburner if you want to run an oilforge.
 
An oilburner fan works great for a normal blown vertical welding forge. I've tried it for a ribbon burner, and it seemed not to produce enough pressure. The one I had was a squirrel-cage type of fan, but for pressure it's better to have a bladed radial fan such as the turbo blower I used on my ribbon.
 
JG Custom Metal Works said:
Thanks for posting that. Does it come with a power cord? Is that pretty much everything needed for the blower setup? Aside from the pipe leading to the forge of course.
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Yes but the switch that is included is worthless and I highly recommend replacing it or rewiring around it. I don't think it's sufficient to carry the wattage the blower draws, mine started to melt. I took it out of the circuit and have had no problems since.
 
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