Blast valve improvement ideas.

[ODaily]

I've been building a coal forge with a CF pot and electric blower. Long story short, I overdo things. In this case a beautifully heavy forge with all the trimmmings.

 

But. I'm ready to mount the blower, which means mounting the blast gate first. I just couldn't bring myself to put it on there. (I tried, I really really tried.) It's just such cheaply made junk. I realize that's what everybody uses, but it leaks everywhere. And it's just so... cheap.

 

This led me to looking for alternatives, and I thought I'd share / brainstorm. If nothing else maybe this'll help someone else out someday. (Good luck, Buddy!)

1. I could rebuild the blast gate. Smooth it up, and put in a thicker slide so it doesn't have such a huge gap. This is probably the most practical of all the ideas, but it will still leak, just less than before. Still seems like a bad compromise.

2. I thought about a 3 inch RV wastewater valve. It's a slide type valve too, but much better sealed. It is however all plastic. I couldn't find any with a metal construction. A shame really, cause If I wasn't worried about accidentally scorching or igniting it, this would be an excellent alternative.

3. There are a bunch of variations of homemade valves that vent the excess air. (Check YouTube.) These look excellent, but my tendency to overdo is likely to go nuts here. Besides, I have a variable speed fan, and should only need to block the air, not vent any. Plus I don't really want to build entirely from scratch.

4. I Really kind of like the idea of using a Chevy Vortec throttle body. Could be easily adapted to a machined plate, and is almost the perfect size. Cons are the outrageous price junkyards charge, the extraneous bits that might come with and need to be deleted (IAC, TPS, etc.) Getting an earlier cable controlled model and attaching some kind of lever to it is an issue as well. Also, I'm not sure how blacksmithy it feels. I mean sure I've got an electric blower, but TBI?

5. I really like the idea of an iris type valve. Pro models are VERY expensive. But... there's a metal iris being marketed as a dawing tool. Google "Iris drawing tool". The original is expensive, but there's a bunch of knockoffs available. It has a max 3" bore, and closes to nothing with a quarter turn. Cons are I'll have to heavly modify or totally rebuild to turn it into a valve. But it's just so cool. I ordered one, cause it'll be cool no matter what I use it for. (FYI, it very much makes me think of Stargate).

6. Theres another iris option. Iris valvs are use for flow balancing in HVAC systems. The smallest valve is a 4". Google "Iris air damper" to see what I'm talking about. One major flaw, they don't completely close, looks like about a 1.5" hole remains open. I could put something permanently mounted in there to occupy and block that middle space. Being a 4" valve on a 3 inch pipe might actuall work out about right for surface area. I wouldn't even want to fully block as I'll always need a little air to keep the fire alive. And if I want no air, I can just switch the fan off. Plus it's almost completely premade, sealed, and basically designed to regulate airflow in a pipe.

7. There's also a radial air damper designed for inline HVAC duct work. It consists of sever small hourglass shaped panels all on a central bolt / pin / pivot. When rotated one way, they spread out, rotated the other way they stack up. Going this way would require homebuilt however. I could not find any smaller than 6 inches in diameter.

 

Anywho, that' what I've been mulling / obsessing over lately.

[Irondragon Forge ClayWorks]

Air gates are relatively easy to fabricate and believe it or not they do not have to be air tight. For sliding one's the coal ash will seal them in no time. If you do a search using your favorite search engine like this    air gate site:iforgeiron.com      it will bring up enough threads to keep you busy reading for a while. Just if you want pictures look at the later threads as the one's prior to 2015 (I think) the pictures were lost in a forum update.

I can't control the wind, all I can do is adjust my sails. ~ Semper Paratus

[Frosty]

I like the iris valve but it'd be imperative you mount it where spectators can watch it work. I'll bet one would be COOL BEANS on the intake side of my Champion hand crank blower. Oh, no practical reason for one there but it'd look so cool. Hmmm, steam punk safety glasses maybe?

Leaky air valves are no problem, put the leaks where they'll exit the air pipe. 

Frosty The Lucky.

[ODaily]

Most of me knows the standard blast gate will work fine, leaks and all. My inner perfectionist however is howling at the thought of putting it in the middle of everything else that's so much better built. Besides, exploring options sometimes opens up new better ideas.

9 hours ago, Frosty said:

I like the iris valve but it'd be imperative you mount it where spectators can watch it work. I'll bet one would be COOL BEANS on the intake side of my Champion hand crank blower.

Never thought of it that way. And I like it. It might just be very practical for an electric, and so so satisfying to watch work.

[Frosty]

[BillyBones]

Have you tried your steel supplier? My supplier sells air gates that are pretty good quality. You can get them from 2" up to 24". 

[ODaily]

Got a pic? I did recently find some sealed metal gates that are the same design as an RV dump gate. 360 dollars.

It's two hours to the nearest steel supplier. I usually just deal with the local hardware store, or scrounge.

 

Speaking of which, I'm off to make the trip to Little Rock and see what the junkyard holds. You never know.

[JHCC]

15 hours ago, ODaily said:

I have a variable speed fan, and should only need to block the air, not vent any.

If you have a variable speed fan, why do you even need a valve in the first place? If you're adjusting the blast, use the variable speed; if you're cutting off the blast, turn off the motor.

[Frosty]

You have a perfectly valid point John but where's the over engineering in that? He's still a long way from that "fare thee well," thing.

Frosty The Lucky.

[Stash]

How about a blast gate from a woodworking dust collection system? I use one as a dump valve, coupled with a pvc 'wye'. Mine is far enough from the fire, so I use a plastic one  you can get off the shelf at Woodcraft or Rocklers or equiv. You can also get them in aluminum. Options abound.

Steve

[JHCC]

1 hour ago, Frosty said:

where's the over engineering in that?

"Perfection is achieved, not when there is nothing more to add, but when there is nothing left to take away.” -- Antoine de Saint-Exupéry
 

[Latticino]

2 hours ago, JHCC said:

If you have a variable speed fan, why do you even need a valve in the first place? If you're adjusting the blast, use the variable speed; if you're cutting off the blast, turn off the motor.

Almost exactly, word for word, what I was going to say.  Sure you weren't a HVAC engineer in a former life?

[JHCC]

No, I just hang out with one whenever I get the chance!

[Frosty]

We're on the same page there, my definition of high tech is the simplest device that does the job well. I was commenting on the OP, he enjoys over engineering and building everything. It's his thing.

Frosty The Lucky.

[Latticino]

20 hours ago, ODaily said:

This led me to looking for alternatives

I personally use Eclipse butterfly valves, but that is because I picked up a couple for free dumpster diving years ago and I don't currently have variable speed on my forge blower.

[ODaily]

7 hours ago, JHCC said:

If you have a variable speed fan, why do you even need a valve in the first place?

This is a little long and messy, so bear with me. Also there ARE broad holes in what I'm going to say, but it's close enough to understand without a need for perfection, so if you're an electrical engineer, try not to flinch and please forgive me.

The speed of an AC motor is controlled by the number of poles and the AC hertz. In the U.S. it's 60hz and motors have 2 or 4 poles. Which is why you always see 3600 rpm or 1750 rpm motors. The correct way to change the speed of an AC motor is to change the supplied hertz with a variable frequency drive. Those however are Very expensive and pretty complicated. They do however give PRECISE control of the motors rpm. That said, not really suitable for a  blacksmith's shop.

 

The above all assumes that the motor in question is rated for a workload greater than the work it's trying to do. So basically not overloaded.

 

The contol on this motor is a rheostat (light dimmer -easy cheap common solution) that is just a variable resistance. It's basically used to reduce the available power level to derate the motor. As the motor's rating decreases it should be dragged down by the load to a slower rpm. And for the most part, it is. But It's a kinda mushy control. As the rpm decreases, so does the load, which reduces the effectiveness of the derating via the rheostat / dimmer. A motor with no load at all, would still be moving at nearly the full rpm, and fans don't really create a whole lot of load.

 

The solution is to increase the load at the same time you derate the motor. Hence the valve and the variable speed. They work together to deliver better control than either could by itself.

 

If you have just the rheostat / dimmer, then the load is the clinker breaker, coal pile, and whatever clinker has formed. The last two are constantly changing as it burns, and the setting on the motor is to hard to find much of a sweet spot with. You'd mostly end up with too much or too little.

If you have just the valve, then as the load increases, the pressure goes up, allowing more air through the smaller opening, defeating the effectiveness of the control to a significant degree. This is why people with constant speed motors like the bouncy castle use a diverter to blow off part of the air, basically derating the air supply by "leaking" it off.

 

 

1 hour ago, Latticino said:

Eclipse butterfly valves

That is perfect. And 250 dollars. Nice dumpster diving though.

 

3 hours ago, Frosty said:

he enjoys over engineering and building everything. It's his thing.

Yeah, it sounds like you get me. Full throttle or nothing. I tend to aim high. I miss alot, but when I connect, I like to knock 'em out of the park.

 

A day at the junkyard yielded a nice valve off of a 2000's Ford 5.4L   The 4.6 has the same valve. I need to ditch the TPS, and create some linkage, but it looks like a very simple and workable piece otherwise. I may need to make a riser block for it, so it doesn't hit the control arm while rotating. Also if anybody else tries this, the later models had a drive by wire electrical motor instead of a throttle shaft. The V6s had a very similar valve, but about 1/4" smaller. Avoid both.

Edited May 7, 2023 by ODaily
clarity

[Frosty]

13 minutes ago, ODaily said:

Yeah, it sounds like you get me.

IIRC you said you enjoy going overboard on builds in your first post. To praphrase of course. 

There's nothing wrong with the game I'm a simpler=better guy myself but can play Mr. bells and whistles, t's fun.

Frosty The Lucky.

[ODaily]

I can do simple. It's just gotta be elegantly simple.

[Latticino]

Look up Varaics or ECM motors. The former are old school and work with some non-synchronous motors much better than dimmer switches. I have never seen anyone who has had good long term success using dimmer switches on AC motors.  Steve can probably tell you why they don't work well for fans.  

The latter are fairly new technology, and expensive.  Still can be available from liquidators and the like if you are crafty.

As far as I know, for using VFD you need 3 phase motors, even if the VFD will convert from single phase to 3 phase.  I use those on my grinders, but they are certainly overkill for a coal forge.

[JHCC]

I’ve had excellent luck running a universal motor off a variac to power a blower. Noisy, but extremely effective. 

[Frosty]

A quick search showed after market 2,000 watt bench top "variacs" by other companies for as little as $75 on Amazon. 

I may just have to order one and see if variable speed makes a difference to how my 2" x 72" belt grinder works for me. 

Frosty The Lucky.

[ODaily]

Are you familiar with PWM (Pulse Width Modulation)? It's basically rapid switching on/off with the length of the off time varied to adjust the duty cycle. 1/2 power is off 1/2 the time. 1/4 the power is off 3/4 of the time and so on.

I searched for "120v ac pwm" and the second unit listed was 6.59

Just be careful, lots of mis listings. Looks like a few are trying to sneak rheostats in a fancy case off, so read before you pay your money. There's a 4 pack for 10.99, for that kind of money you could probably take the risk?

 

[BillyBones]

Those "drive by wire" throttle bodies still have a shaft that opens and closes the butterfly. They just attached a small motor to it rather that a cable and linkage. Remove the motor and you will find a small piece of shaft sticking out. 

[Frosty]

Yeah, you have to be careful, especially if you aren't knowledgeable in the subject. I compared the performance claims to the ones on Variac dot com's spec for equivalent devices. I didn't even open sites claiming lower prices.

I have a local electronics GURU to ask though I'm sure Ill have to decline letting him build me something.

Frosty The Lucky.