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JohnK

Assistance request

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Hello my fellow smiths. This is my first post so I assume this is the correct place. I have built (after many months of trial and mostly error) a waste oil forge blower assembly. My new issue is that now it's not heating as it was. The old fan burned (from a hair dryer). The new one doesn't seem to produce the same results. I'd say a few hundred degrees cooler. I assumed it was the voltage or even the fan itself, perhaps the design. I guess I made a perfect match and changed a variable. Any ideas fellows?

Screenshot_2019-08-12-21-12-31.jpg

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That sir I don't know how to calculate. They are both from hair dryers. The  original was smaller but I'm not certain of the cfm( as it has since melted due to accidents). Though I wouldn't believe there would be much difference. Would more cfm produce better results? I know the chamber is heating to workable temperatures. Not enough air for what it really wants?

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My advice would be to do yourself a favor and buy an actual blower. I bought mine from blacksmiths depot. It is a costly venture compared to a hair dryer I'm afraid, but you can also use it for a coal/charcoal forge, or melting/smelting operations. 

I bought the 100 BTU which I run mostly closed off by way of gate valve on my blown burner. 50 btu would have been plenty. I dont regret the purchase. 

Good luck!

Edit: it may have actually been 100cfm... or $100... I dont really recall. I hope someone with a little more wit might steer you in the right direction. 

Edited by Zeb Camper

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You can also go to someplace like Ebay and look for party house blowers.  You might have to use a little imagination to figure out how to connect it to the forge and put a gate valve in the line to adjust the air flow but they are relatively inexpensive.

Doug

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You may also look for electric leaf blowers. I used one for my initial heat treat coal setup and worked very very well. I had to cover up the air intake on the lowest setting because of the CFM it produced. 

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I use a leaf blower on my blown forge as well.  It's loud, and produces waaay to much air, but it works.

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Am I wrong to assume the cfm isn't nearly as important as air pressure with forges? I have many squirrel cages that'll summon Satan using only wood. Not coal or charcoal. Wood. But does nothing for a waste oil forge(my many trial and errors). So I assume for waste oil the pressure is what's required to atomize the fuel or at least whip it around enough to make droplets. I do know hairdryers are designed for pressure more than cfm but logically it should work since my first did. I'm wondering if adding a 90 on the exhaust would help? Working to give more hot surface volume for the oil to vaporize? Also a treat so it'll work like a vertical blower.  

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Call around your local HVAC guys and ask if they have any oil furnace parts.  Maybe even a whole burner complete with blower and electric ignition.  Those use a pump and a fine nozzle to spray atomized oil into the air blast, and the spark plugs set it off.

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This all sounds a little dubious to me.

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I think this would fix the issue. I think the air acceleration is low and the fuel is puddling on the back of the reducer and trickling down the pipe and cooling it. 

Screenshot_2019-08-14-09-47-33.jpg

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Atomization of a liquid like waste oil will generally require a lot more energy than you can get from a simple venturi.  I think you are going to have to pump the oil into a nozzle to get it to atomize well enough to burn efficiently.  Waste oil burners always freak me out a bit, but I know a few people who have done exactly what Alan suggested.. 

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I have already tried :( I live in the south and well I dont believe anywhere around here has those. Even scrap ones. Just doesn't get cold enough. I bump shoulders with many hvac guys. None have even seen one.

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Here's one if you have the cash...

https://www.supplyhouse.com/Beckett-B2007-AFG-Flame-Retention-Residential-Oil-Burner?gclid=EAIaIQobChMIx-yAtYSD5AIVg4vICh1j2w-LEAQYBCABEgJAafD_BwE

I'm on the southern edge of oil burners myself, but I've managed to salvage a couple over the years as replacements for the one in my house furnace if and when it finally dies.  Great cheap heat!

Also, here's just the pump.  A small 3450rpm motor will run it: https://www.homedepot.com/p/Suntec-Oil-Pump-2VA7116/202274776

I know none of that is as simple as a drip-fed oil furnace.  Somewhere on this site there is a guy in New Zealand who built one of those that seemed to work well.  I'll see if I can find it.

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I'd totally appreciate that! I know it's stubborn to no just buy what's best but I like the feeling of building it myself. That I know everyone here can understand. I had planned on buying 3" nipple reduced to 1 1/2" as a way to accelerate the air. I know it'll assist in spray. Likely not atomization but once up to temp it should be fine. I've toyed with a pump version for a couple months but either it used way more fuel than its worth or didn't work due to a lean mix. I've seen guys using the design Im using but I'm not all thrilled about the noise of a shop vac or air compressor. Forging should be relaxing and not sound like a airport runway on Christmas eve. 

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