opinion on my furnace design

[haddy85]

Hi Guys,

 

Been looking into casting some of my own parts as 1 off part purchasing is bloody expensive and no where near as fun.  so I have been doing some research on casting, forging, furnaces and so on.

 

I have put together a bit of an improvised plan for a 44 gallon drum, as i want something that can handle some decent size casts as well as have the capacity to go up to irons and steels when i get experience with the craft. As i wouldn't mind doing a bit of smithing as well.

 

From all the designs I have seen, they all require the basic drainage in the bottom, a hole in the side for the burner and an exhaust at the top. they should be made of either fire bricks or recastable suited for the purpose / temperature.

 

 Which you could make yourself that could handle up to 1000 oC or purpose made recastable with some ratings of up to 1600 - 1800 oC which i will be using for this project.

 

before i started on the project i wanted to put the basic idea up for critiquing to see if there is anything i have missed / save wasting my time and money.

 

Also one question with the recastable, as you would expect the the drying and first burn instructions are quite extensive, with the first burn what's the best way to control the temperature? would it be a propane burner? with controlled burns to raise the temperature slowly? or any other suggestions for the first burn?? 

 

Cheers for any help.

44 gallon drum furnace design.pdf

[ThomasPowers]

Just remember that if you cast a part off of an original that the duplicate will be smaller due to shrinkage---the metal fills the mold at high temperature and shrinks as it cools to ambient.

 

I once had a shrink rule; like a regular ruler but each side was laid out for a different metal with the scale increased the correct amount so a piece cast in that metal to a pattern laid out to that scale would end up the correct size.  I ended up giving it to a friend who did a lot of casting.

[Steve Sells]

Maybe I missed WHAT you are casting, AL, is a lot different than Fe.

[haddy85]

Hi Guys thanks for the replys,

 

not up to casting just yet, just seeing if anyone looking at the attached pdf could tell me if the 44 gallon drum furnace i will be making is good enough or i missed anything?

 

will be using it for casting al but progressing to iron and steel.

[Frosty]

Welcome aboard 85, glad to have you.

 

What you use and how you use it in a furnace makes a difference. You are asking such a vague question you aren't going to get very meaningful answers, it's not possible. It's sort of asking what kind of vehicle should I buy? Ox cart? Surrey?, Semi truck-trailer? then you get into subcategories: what kind of semi? bulk hauler, liquid solids, hazmat or dirt? dead cars compressed into blocks or maybe road building equipment.

 

I'm not being specious, you need to let us know what metal you want to melt and in what size batches.

 

Frosty The Lucky.

[haddy85]

Hi Frosty,

 

Thanks for helping This furnace is designed for iron and steel, in a crucible that is 220mm dia x 240mm deep, (holds 44lb of brass) not sure how much weight difference there is from brass to iron in that volume but i understand it would be a bit of difference. 

after a bit more research i realized that melting point and the point at which you pour is quite different so the 

temperature rating of the recastable will be higher than in the pdf, i will increase it to 1800 oC or 3272 oF

 

it will be run on either propane or waste oil 

 

is there any thing else that you need to know?? 

 

Thanks again

[Frosty]

How much casting experience do you have? Casting any of the high temp metals is VERY dangerous, especially if you're learning, not to mention trying to teach yourself. That you don't seem to know some of the  most basic info leads me to think you need to get connected with casters and learn the craft from folk who do it. As one small example of your lack of knowledge, casting steel isn't something done in the home shop except maybe by the masters of the craft that know how to maintain the metallurgy of steel.

 

A quick web search turned up a whole bunch of "metal weight" sites, this one was about 5th. down from the top of the list. http://www.simetric.co.uk/si_metals.htm

 

I'm not a caster though I have some experience so I'm not about to give you any specific info. I recommend against waste or fuel oil burners, they're potentially very dangerous, even in open air.

 

I'm not trying to be discouraging but please hook up with folk who know their business this is just too dangerous to play around with.

 

Frosty The Lucky.

[haddy85]

Hi Frosty,

 

Thanks for the concern, as i mentioned in the original post i was going to start with aluminium casting, forging tools ect.

i don't expect to fly before i can crawl. :) i do understand the dangerous nature of working with explosively high temperatures

and wouldn't try and do anything without understanding it and gaining experience on smaller projects.

 

and yes steel is not generally done at home because of the skill level required from years of practice, i'm merely building this

furnace to last and expand with my skill set even if it could handle iron i would be happy with that.

 

why would you not use waste oil burners, i would think that propane is more dangerous as with out the igniting temperature

the oil wont burn or explode where as propane only needs a leek and a spark?

 

Even though i am quite new to this please don't put me in the same category as the person that wants to cast the sword for

their first project. (knowing this is not Disney and that a sword is not cast)

[Frosty]

Without some professional grade equipment waste oil is a serious PITA. It requires good filtration or suspended crud will muck things up. It's thick and viscus so it flows slowly without a good pump, another thing to get plugged with crud and you'll need a  pump to force it through filters so. . . Then there's getting it carburated so it'll burn well, the two most common home methods are vaporization or high pressure injection through a spray nozzle. More things to plug up. Oh yeah, injectors require a high pressure pump and the oil has to be preheated to flow well enough to spray.

 

Then there's the energy density of oil, depending on it's weight there'll be varying BTUs per unit, gal. liter, etc. Using waste oil, unless you have hands on control of what goes in you'll never be sure of the energy output of the burner so adjusting it may become a near full time chore. Sure, you SHOULD be able to adjust it once per fill up but you just never know.

 

A lot of odd and BAD stuff finds it's way into waste oil tanks. There were waste oil heaters in the equipment shops where I used to work and even considering the only oil going into the tanks came out of those two shops and was inspected by ONE guy bad stuff kept finding it's way in. They finally disabled then removed the heaters because a couple times a month a pint or two of antifreeze ended up in the tank and it just plain burned the burners up and after a couple times the heat exchangers were toast too.

 

Considering a person needs filters, a couple pumps, injection and a preheater and the thing will keep getting all crudded up and failing, a normal person switches to fuel oil. Fuel oil is the most dangerous petroleum product loaded at fuel docks. Two things make it very dangerous, worse than gasoline or compressed gases. It's saturation point, that concentration where air won't hold any more, is smack in the middle of it's flammable range. So, if you have a tea cup size bubble at the top of a huge, say 50,000gl. tank the fuel air ratio in the bubble WILL burn, rapidly if ignited. It's not only very easy to make flammable in air, it's a high energy density fuel so there's plenty of power per cubic foot of fuel air mix.

 

Spring a leak in a propane line and the automatic check valve will shut it off and the gas will rapidly dissipate provided you don't put it in the basement. Natural gas/methane is lighter than air and less powerful in it's flammable range so there's less power and it dissipates even more easily.

 

I know of a couple guys using fuel oil forges, one here in Alaska and they use burners out of oil furnaces and use them outside where vapors can't build up.

 

I'm not saying it can't be done, it is being done, I just don't recommend it as it's dangerous beyond it's value.

 

Frosty The Lucky.

[haddy85]

Thanks for that frosty, i had only considered the waste oil and propane burners due to their affordability i did see the issue of clogging 

with the waste oil and the issue of temperature control. hence the reason for asking about the propane burner to control the temp on the

first burn for the furnace.

 

when i'm talking waist oil i wouldn't be using motor oil it would be locally sourced oil from the fish and chip shops, so free and worth the PITA

 

i did manage to come across a well recommended waist oil burner on http://www.backyardmetalcasting.com/oilburners09.html simple and 

effective provided the oil is the right viscosity. 

 

it will give me something to tinker with on the initial small projects i guess, just have to see how it goes really.

 

so with the design of the furnace i have provided (not including burner) would it handle the above iron project 40lb 

i don't see why it wouldn't but that's why i wanted to double check see if i missed anything?

[Frosty]

I can't say about cooking oils, the only things I've heard is about using it as motor fuel. I believe you have fewer filtering issues to worry about and no wear particles found in lubricating oils. There is water but that can be separated using accepted motor fuel techniques, all off the shelf.

 

Keep us up to speed on your progress please. Oh and if you have any questions about propane burners let me know and we'lll get them working properly.

 

Frosty The Lucky.

[Steve Sells]

as a person that has cast metals, including steel...  your furnace you buiild now wont last long enough for you to ever use it to cast steel.  It will need to be rebuilt a few times before you gain enough experiance for steel.  after you do a few runs you will understand why I say this.

[Nobody Special]

Refractory is tricky for hot enough to melt steel. In a 44 gallon, it's gonna take a LOT of heat. A lot of refractories start to break down at around 2000-2500 degrees. Propane may not be up to the task for a beginner for such a large space.. In a 5 gallon bucket, maybe a naturally aspirated T type burner, sure.

 

For something that large, you might want to try forced air through lump charcoal. It'll use a lot of it, but relatively easy. You'll want to use flux, and preferably a good crucible with a lid to keep from oxidizing the metal. Waste oil.....tricky technically, lot of excess carbon and oxidation.

 

If you haven't cast much before, I highly reccomend that you find someone who has, and/or start on a small scale  (3-5 gallons) before making something that size. There's a huge learning curve.

[haddy85]

Thanks frosty, ill take you up on that in a couple of weeks, will be using some old pavers this weekend to create my work space. then the furnace build will begin. :)

 

 

as a person that has cast metals, including steel...  your furnace you buiild now wont last long enough for you to ever use it to cast steel.  It will need to be rebuilt a few times before you gain enough experiance for steel.  after you do a few runs you will understand why I say this.

 

i really didn't think of that, thanks Steve. i think it might be best to start with a smaller furnace after all, :) was starting to head in that direction as i still wasn't sure on controlling the temperature sufficiently for the first burn and if you cant get that right the refractory will be worthless. :)

 

 

I highly reccomend that you find someone who has, and/or start on a small scale  (3-5 gallons) before making something that size. There's a huge learning curve.

 

Thanks nobody special, was starting to head that way,  and was going to source a 20lt ( 5.2 gallon) tin this weekend, as i said to my partner (who's also interested in this as a hobby). i'm not confident with controlling the temperature, making Big Bertha could be a waste of time and money if we stuff it up. :)

 

Also managed to find a small blacksmithing place only about an hour from us, which can help us with forging and probably the odd casting question.:) 

 

Thanks for the help guys, is there any place to post projects for criticism/feedback on process/finish?

[Steve Sells]

I cheated for a start, I took on a second job at a cast iron foundry for about a year so I could learn about casting iron and steel.   Begin with 500 gram to 1 liter sized melts, and do your self a favor and BUY premade crucibles, do not try to make them. 

 

Aluminium to start then move on to copper alloy's. After you are comfortable with your skills, later you can try iron based. there are differences between them all,  but many basics remain the same.  no matter what you use for refractory's they will have to be replaced and furnace parts rebuilt, at these high temps its just the nature of the craft, needing to keep things in top shape.

 

remember HIGH QUALITY safety gear, incluiding full face shield, jacket, chaps and spats for over your boots.

[thingmaker3]

One may save a great deal of gnashing of teeth by using proven designs while learning. If one truly wishes to walk prior to flying, there are several resources for proven small aluminium furnaces.

Worry now about getting a good pour without risk of injury. Worry much later about manipulating 40 pounds of sear-your-bones liquid chasing you around the shop. :o