Biopowered - vegetable oil and biodiesel forum
General => Chatter => Topic started by: julianf on February 02, 2014, 08:25:04 AM
-
http://www.youtube.com/watch?v=Zt8L5OVu7zw
note: they only make an ingot, but, still - looks like zero spent on equipment! : )
-
The first aluminium casting I did used a bean can (not recommended) on the front room fire, making a work lamp for the lathe which I'm still using today.
If you've not tried metal casting, dream up something to make, it's great fun.
-
See, for me, that part is easy - all i want is (good) slabs of aluminium for machining.
I could melt small amounts easily enough - i reckon when the cast iron hotplate of the rayburn starts to glow its probably going to be hot enough in the firebox, but i can only do small quantities then. Also, as its covered in machine oil it may get a little exciting to be doing indoors?
I guess, volume wise, id be wanting to do something like 4ltr batches. That'd give me an ingot of, maybe, 25 x 35 x 5 (cm) after wastage? (3500cc)
I like that ive just noticed people using the bases of fire extinguishers. Ive only seen them using fancy graphite crucibles before, which are money, but we have Brett, so that may be that side taken care of : )
Our oil boiler is not in use at the moment, so i could use the burner from that as the heat source.
-
The classic home foundry is based on a 20 ltr can and is a piece of cake to make.
Cut the top off about 2" down. Make holes in the sides at 90° to take 6 or 8mm reinforcing rod forming a cross inside. Get some "grog" fire clay mixed with fine gravel ... can be bought ready mixed and quite cheap. Pack the lid flush with the cut edge. Make a 2" hole, 2" up from the base of the can and a hole to take a 12" length of cast iron down pipe at a 30° angle pointing up, 2" from the top opposite to the hole in the bottom. Pack a 2" layer of grog in the bottom up to the hole.
Then line the tin with a 2" layer of grog ( you can use another 20 ltr can cut up to act as an internal former spaced with bit of wood) and break out the bottom hole. Pack it around the down pipe, which should be supported until the grog drys. Put somewhere warm to dry for as long as possible. Once air dry, light a gentle wood fire in it to dry it further, the slower the better. You can make a three legged stand with grating about 4 - 6" tall, but many people don't bother.
Get hold of some coke and start a fire going. Once its got hold add coke, allowing enough room for the crucible. Stuff a vacuum cleaner or something similar on blow into the bottom hole and let it run. Aluminium will melt quite quickly, but other metals may need a top up of coke.
For aluminium you may get away without a blower if you have a suitable length of stainless chimney liner you can run up a tree or brick wall to create a draft.
I've melted cast iron in one of these, but it took a couple of charges of coke and even then the iron chilled too quickly resulting in a very hard surface, but it was still possible to machine with some effort. Melting iron, it's quite astounding when you open the furnace ... it's incandescent to the point of being uncomfortable to look at and very scary the first time you try and pour it!
-
i know how scary molten cast iron is. i worked in a foundry once, when i was young and foolish. the job we hated doing was changing the hydraulic hoses under the 7 ton pot of molten iron. the hoses would blow in the middle of the pour so we had to go underneath and change them with 7 tons of molten iron over our heads. it was hot but not excessivly so. must have very good insulation around the pot. if we coundnt fix it in time it took a wekk to chisel out the cold iron. i gave up working in the engineering trade after that.
-
damm! just lost an hour looking up the company i i was working for at the time. they still exist but have moved. lots of pics of the place i worked at.
-
Cast aluminium is not ideal for machining. I used to do a lot of it at school with the kids. You don't know the ally you are using and it can turn out too soft so it rags on the tool or have gas or other inclusions in it. Even when degased with chlorine it is can still have gas pockets. It is ideal if the casting is not going to be machined or if the machining is in an area that is not seen but for CNC work solid stock workers much better.
-
I did not really realise it was possible (well, feasible) to do other metals. I guess brass isnt much higher, which might be useful.
Julian - do you have a diagram of what youre describing? I can follow your description, but if its from a book or something, then i could probably find it. I know you mentioned a book previously, but, when i looked, it seemed more on casting, whilst all i really want to do is make ingots, to physically machine there after.
So, what i need at this point is a way of melting the metal, and moving it to the ingot mould.
Coke and a blower are possible, but i was thinking along the lines of a central heating burner running on bio. From your experience, would you say this is a bad idea, and i should stick with coke?
-
Cast aluminium is not ideal for machining. I used to do a lot of it at school with the kids. You don't know the ally you are using and it can turn out too soft so it rags on the tool or have gas or other inclusions in it. Even when degased with chlorine it is can still have gas pockets. It is ideal if the casting is not going to be machined or if the machining is in an area that is not seen but for CNC work solid stock workers much better.
Dick,
All the stock i have is 6000 series. I assumed (possibly incorrectly?) that if i used only that material, then i would end up with that material at the end?
Im aware of chemicals you add to make the dross float up, and to degass, but i have no idea yet where to obtain them.
-
There you go, just a rough section but you should get the idea. The grey areas are "grog" ...
(http://www.palmergroup.co.uk/Bio/furnace.png)
I used to get crucibles, casting sand and grog etc from a place called FL Hunt (think it was FL but I could be wrong). I'm pretty sure I read they went bust, but a quick google reveals these people who seem to sell all the kit along with dental supplies for some obscure reason ... http://www.johnwinter.co.uk/ . They have a whole page on fluxes and degassers. I'm sure if you search the model engineering forums you'll find more willing to sell small quantites. I remember I used to grind up cat litter (unused) as a source of fullers earth ... but I can't remember what I used it for, possibly core making.
There was a general school of thought in the model engineering world that if you used scrap of the correct type, the casting process didn't alter it's properties too much. For aluminium, I used to smash up gear box casings and bell housings, they seemed to machine OK. Pure ali. would certianly be a different matter.
-
Cast aluminium is not ideal for machining. I used to do a lot of it at school with the kids. You don't know the ally you are using and it can turn out too soft so it rags on the tool or have gas or other inclusions in it. Even when degased with chlorine it is can still have gas pockets. It is ideal if the casting is not going to be machined or if the machining is in an area that is not seen but for CNC work solid stock workers much better.
Dick,
All the stock i have is 6000 series. I assumed (possibly incorrectly?) that if i used only that material, then i would end up with that material at the end?
Im aware of chemicals you add to make the dross float up, and to degass, but i have no idea yet where to obtain them.
It is far better if you use a known stock but it is also heat treated after production (hard half hard etc) the stock I have used was also drawn which again refines the structure.
This is one link to degassing tabs.
http://artisanfoundry.co.uk/store/product_info.php?products_id=67&osCsid=932b7bbb45af1524a27fd64a7709dd8e
Not used those particular ones but I imagine they are mostly the same.
I would also invest in a graphite or fireclay crucible . It is easy to make pickup tongs and a pouring ring. When you pick the crucible out of the furnace make sure the pickup tongs and the pouring ring are red hot. I have had a crucible crack out of the ring and deposit a gallon of liquid aly on the floor. Oh you should pour over a sand try containing dry sand, liquid aly on concrete goes about tike mercury but it is hot!
-
There you go Dick's found another good supplier and I'd agree with his comments about a crucible, especially if you want to experiment with other metals and the dry sand bed is a very good tip.
I remember visiting a foundry in India many years back. That had a sand floor on top which all the spills went, but the workers were walking round in shorts and bare feet!
As to running a furnace on bio, I've no idea if it would work. I hadn't even heard of bio when I was playing at casting. If it's something you're not doing on a regular basis, I recon coke would be a lot less hassle to set up and you know it will work.
Worth investing in a chrome leather apron and some leather boots if you don't have some already. In place of a visor I used a welding mask with two, clear glass screen in place of the tinted.
-
The apron should go over the boots. We used to use leather spats over leather boots as well. You don't want to get a boot full of molten aly.
-
Just wanted to run this idea past you quickly -
Get a used MAPP cylinder.
Grind the end off it
Weld on some sort of hoop for a 'handle'
Load it with swarf
Put in in the rayburn firebox
If i can melt the swarf down into even impure ingots, i think it will motivate me to go further.
So...
Assuming i have the MAPP cylinder in the firebox full of molten aluminium, then what?
My concerns are -
Stuff getting in there - should i fashion some sort of lid also?
Then what to cast the ingots in - i guess a cupcake tin, but any better ideas?
Is the degassing done at ingot stage, or at final cast? Ie can i just get on and do this, or should i buy some 'stuff'?
Thank you : )
-
Go for it if the Aga gets hot enough. My first experimental ali casting was done on the lounge hearth using a log fire, a tin can and a pair of mole grips (wearing gloves!)
Don't make the MAPP cylinder too deep, you'll need to scrape off the dross the melt. Recommend you make pair of tongs to grip the circumference of the cylinder you can use them to lift in and out and pour. A lid is a good idea to stop contamination from the fire.
I've not read this anywhere, but I suspect the amount of dross is related to the surface area of what you're melting, guessing the surface oxides, so swarf may not be the best feed stock.
Make an "L" shaped hook to scrape off the dross, preferably on to dry sand, but with ali you could probably use a steel tray.
I never tried a steel mould for ali but I guess it should work ... there's only one way to find out! As an alternative you could make an impression in VERY SLIGHTLY damp sand (better to get green sand or similar) or fashion one from a plaster and sand mix, but make sure it's thoroughly dry before pouring.
Any degassing additive should be added to the crucible after removal of the dross and stirred in but I never used it. Give it a go without, you've little to loose. If the casting is porous, then get some degasser.
-
Oh, meant to say ... don't know how you would ensure the MAPP gas cylinder was purged before attacking it with a grinder ... might be best to saw it by hand!
-
As j says you will have problems with swar due to the oxides and cutting oil if used. Better to try som bits of stock. Make sure whatever you pour it into is dry and if metal hot. I have seen aly poured into a damp ingot mould go up and come down as very hot rain. A bucket of dry sand to put the dross into and to hold the ingot mould is a good idea.
Have a go it is not as dangerous as perhaps we are making it seem but do take care.
-
The reason i want to use swarf is simply as i have loads of it!
Ive got off-cuts also, so i could also try them and see what the difference is (they are the same grade).
Id like not to sound like an idiot, but im not too bothered by the danger aspect.
Ill tape down the trigger on my torch to drain what i can from the cylinder, and then see what happens...
-
We're burning coal today, as, would you believe it, ive run out of glycerol!
(we accquired the coal, so its not so bad ; )
Anyhow, ive chopped the top off the cylinder, and its in the firebox at the moment (empty) as i thought id see how hot it got (using my IR thermometer - which only goes up to 560c, but it will be an indication at least) and then how easy, or otherwise, it is to manipulate the cylinder in and out. So, a dry run, if you will.
If it gets hot, ill put some metal in there and see what happens : )
-
Well, that did not take long - just looked in, and the whole base of the cylinder was glowing red.
Have now loaded it with a quantity of (damp with cutting fluid) swarf, and will see what happens next!
-
watching with trepidation from a safe distance as Julians kitchen fills with oily cutting fluid fumes.
-
It takes lots of swarf to make a usable amount of metal.
-
We went out, hence the lack of reports -
The swarf was dissapointing. Although it all glowed red, it did not form a liquid. It did somewhat bind together into a hard lump, which is now stuck in the bottom of the cylinder though.
Some of it i was able to knock out (dry crumbly stuff, that looked very much like it did when it went in, but dark grey, rather than silver) but the rest is still in the cylinder (i have not looked since it cooled though)
I then tried some a small offcut, which melted fine, pooling on top of the swarf lump at the base. I tipped this (small amount) out onto a tray, and it looked as you would expect - a lump of metal, but probably only 10-15cc of it.
So, in conclusion -
Offcuts melt fine.
Swarf does not. My hypothesis for this is that it oxidises (?) far too much whilst its heating.
Im wondering if this can be resolved somewhat by feeding it into a molten pool (rather than just trying with the swarf from the start) such as its bought up to melting point that much quicker.
But im wondering as to the dangers of doing this without it being properly dry first.
Its not like i have tonnes of the swarf - probably about 50 litres in volume. It has minor value at the yard, so i could just take it there, but if that 50 litres gave me 2 litres of product, id still be happy.
Any suggestions?
-
Probably the best way would be to do it under an inert gass. How to do it I don't know. One of the problems is that it does not weigh much so it is difficult to get much in the pot and it does not conduct the heat through so has lots of time to oxidise. You could try compressing it somehow before heating.
-
Dry casting? Forget that, use plenty of water!
http://www.youtube.com/watch?v=WUVUYH_vvZE
-
Just gave it another go.
I started with offcuts, got a good pool at the bottom, and then added some swarf.
I was real dissapointed to find that everything in the tin seem to have gone hard. And then i realised why...
(http://static4.fjcdn.com/thumbnails/comments/3947037+_d7c415f29874075459f3a65003c7792d.jpg)
That photo was taken in the basement of the reactor at Chernobyl, where the molten reactor core solidified into a structure later named as the "Elephants foot"
I have something similar (but a little less of concern to the world at large) in the ash compartment of the rayburn!
It seems small gas cylinders are not as tough as i had hoped.
-
...i suspect this may be the last time i try this stuff indoors.
(well, probably not, but ill give it a while anyhow!)
I think i will try and make a proper furnace using one of the oil fired boiler burners i have here. Ive got a couple of gas cylinders (for the body of the furnace) but they are some way away. Freecycle will provide though, im sure! : )
I need to find a better crucible also. The aluminium was only on the cusp of melting when the MAPP cylinder failed, so it did not take much at all.
-
Your steel cylinder possibly failed as a result of a eutectic type reaction with the molten aluminium. Perhaps better to try with a ceramic type container or don't use thin steel containers more than once.
-
I have just read that iron is soluble in molten aluminium. Id assumed this was only once it was at its melting point, but maybe not.
I should probably see if i cant acquire a proper ceramic crucible, and some matching tongs.
I have a load of night storage heater bricks about here. By their nature, they are supposed to absorb heat, rather than insulate, but the are physically stable at higher temperatures (although the one in the firebox of the rayburn is falling apart)
Or i should just get a propane cylinder and do the job properly.
-
Coming back to this (ive been clearing out the shed here, and have much more brass than i thought) -
I understand that a reasonable lining can be made from perlite and fire cement (if i can get these things locally, im more likly to get them). I think the ratio suggested is 4:1. 4kg of fire cement is about a tenner (toolstation), but, depending on the size of the furnace (obviouly!) ill need more or less than that.
Julian, you mention a 20 ltr tin. Obviously i have a few of them, but i wondered about getting an empty propane tank off freecycle? Something like this -
(http://i.ebayimg.com/t/GAS-CYLINDER-7KG-EMPTY-/00/s/MTIwMFgxNjAw/z/UpUAAMXQVERSyWVp/$_12.JPG)
?
I wondered if the thicker metal wouldnt be easier to work with etc? Less likly for all the grog to fall out at the first knock?
ps. i know this is taking me a while. i have too many things to be doing at the moment as it is!
-
I think you'd just be making more work for yourself. Once fired, the grog lining is quite solid. After many years sitting under cover in the garden, my tin rusted away and left the lining intact.
The fire cement idea sounds very expensive. Have a read here ... http://www.artfulbodgermetalcasting.com/9.html second half of the page. Looks like you can get away with clay dug up from the garden (or someone elses if you're not on clay) and some of your fire bricks crushed up. As I said before my grog contained what looked like pea shingle.
Infact have a look at the whole site, there are quite a few furnace designs and snippets of information on there ... obviously things have moved on since I was doing it.
-
Just had a quick scoot through that site it's really quite good!
If you want a quick and easy way to start ... dig a hole! ... http://www.artfulbodgermetalcasting.com/8.html
Near the bottom of that page he suggests using bricks and there are photos elsewhere of a waste oil (WMO) burner.
In fact the more I read, the more I think I like this chap ... he's built a powder coating set up at home ...
http://www.artfulbodgermetalcasting.com/resources/Powder+coating+oven.doc
-
Next time i have a spare* score, i think ill buy his book.
Im sure i read something on the site about making cast crucibles, but i cant find it now.
I have a fair bit of cast scrap about here also. Indeed, i seem to have a selection of metals, inc a minuscule amount (ie not worth doing anything with yet) of gold.
*spare as in without somthing more pressing to spend it on!
-
Yes, I saw the mention of making crucibles, but didn't notice any details.
Where's KH? He must have dozens of VW bits that would benefit from powder coating. Been reading up on that, looks like a piece of cake!
If you get the book, I hope you'll share some of the info.
-
Of course.
I did put a post on freecycle, and have just received a mail from someone in a nearby settlement. They say they have loads of 'big' ones, but one smaller one. I did mention that i was after a 10-15kg unit...
The thing i really want to be able to make is aluminium blocks, but of a reasonable size - about 4 litres. I know i have not done anything yet, but if im going to put any effort in at all, i may as well make it large enough to do what i primarily want out of it.
I might do well to mention - my cnc machine took me about 18 months to build, which, compared to the <18days it took you to sort the reprep... well, all im saying is dont hold your breath!
-
ps.
I would like to be able to use my boiler burner on the unit.
I know the book linked to gives plans of a waste oil burner, but i figure i have a burner with a fan, electronic ignition, etc. currently, so, if i can use that, it would make life simpler.
-
This is another good site for info
http://www.backyardmetalcasting.com
Ive been following this thread with great interest, please keep us up dated..
-
Ive been clearing up further today, and realise that i have far more night storage heater bricks than i thought.
Im now wondering about laying them out and pointing my biodiesel fired burner in...
Ive been reading more though, and think that what i probably need to acquire first off is a crucible. That was what went wrong with the rayburn attempt - rupture in the container, and spilt metal.
Im also aware than the furnace has to match the crucible.
-
Have spotted this on ebay -
(http://i.ebayimg.com/t/Vintage-French-Bread-Meat-Loaf-Tin-Mould-/00/s/NzUwWDEwMDA=/z/AIYAAOxy0NtTFZrU/$_12.JPG)
#281278661513
Im pretty sure thats cast, right?
If so, if it were structurally sound, it would make a fine crucible for me. What do you think?
-
seller sent me another photo - unfortunately, it has a crack : (
-
Found this site -
http://www.plansandprojects.com/My%20Machines/Unaltered%20Becket.html
(http://www.plansandprojects.com/images/unaltered%20Becket/00009.jpg)
Chap using a boiler unit on a furnace (as i mentioned intending previously).
Im convinced that's got to be my simplest path way in.
And, yes, i know im doing more talking than action - i still need to find a crucible. Since Rachel has passed her driving test, im getting out far less (single [working] car - which she takes to work, not working from home and all that...)
I have to pick up oil tomorrow, so im going to look for some cookware in charity shops.
-
Cunctatious perhaps!
Just get a flower pot, pack some clay or fire cement in the bottom and fire it. The world will have invented a replacement for metal, by the time you get round recycling yours!
-
So you mean use the clay pot as a crucible, rather than the furnace lining?
You think the bottom would be water (molten metal) tight?
I know i can melt stuff - i managed that with the MAPP cylinder in the rayburn, but id like things not to go wrong (again), so i was looking for a more suitable container.
I found the meaning of "Cunctatious" at a site entitled "Obsolete Word of the Day" - we cant all go building fancy 3d printers overnight, you know?
-
They fire Thermite in clay flower pots, and you're only looking for about 600-700°C.
However, I've just googled it and the concensus seems to be that a flower pot is not a good idea and most suggest a steel pipe. You could try lining the that with fire cement. Most fire cements seem to be good to 1200°C and from experience they stick like the proverbial to a blanket.
-
If i use steel, im thinking it will just flake like the MAPP cylinder.
Someone recommended stainless, which, i assume, is less reactive, so does not flake. Or cast. So both are on my charity shop list.
-
I actually purchased a cast iron pot the dump yesterday...
I got it home, and she said, "Thats a nice pan..."
...and i no longer have a cast iron pot.
Will see what is about at the 'boot sale' tomorrow morning. The lost unit was a reasonable size (7.5" dia) but may not have been the best shape for lifting / pouring.
Photos -
(http://www.alloyavenue.com/vb/attachment.php?attachmentid=10298&d=1394915610)
(http://www.alloyavenue.com/vb/attachment.php?attachmentid=10297&d=1394915606)
-
Oh, and id already got her one of these -
(http://www.ecookshop.co.uk/ecookshop/products/large/xlarge/201242309.jpg)
RRP £75, ill have you know.
It seems ive now lost both pans! So that's £3 ill never see again.
-
If you got your arse into gear you could cast her some pans!
-
Have got afore mentioned book now, and revised my plans.
Current best plan is to make inner lining from night storage heater bricks, and outer lining from perlite / fire cement mix.
It seems that the perlite probably wont stand up to the temperatures involved for the inner lining, and possibly wont for the outer either - however, if it burns out in the mix, then i cant see that being too much of an issue, as all i want on the outside is insulation (if i had cash to throw at it, id use ceramic blanket)
-
Gave it another go last night, as i found an empty disposable argon/co2 cylinder.
That did not even go through one session before rupturing and spilling its contents into the ash tray of the raburn.
Still have not collected the kiln bricks i have lined up for the proper furnace, but that may happen later in the week...