Making a foundry for a one off pour?

[simonl]

Hello Foundry people!

I'm in the process of cleaning, painting and repairing a Bandsaw. It's a Heska 260 Ha. The repair part is the most difficult part as it requires a replacement worm gear in the gearbox.

The gear details are as follows:

No. teeth: 40
Module: 3
Material Bronze, (Phosphor bronze I suspect)
Outer diameter: 130mm

Anyway, obtaining a piece of bronze 35mm thick and 150mm (allowing for machining) is either difficult to obtain as scrap or out of my price range for new.
I have a few other options up my sleeve, such as using other material etc but the preference is to make a replacement out of the same material. I can obtain scrap Phosphor bronze at reasonable prices which leads me to the question of pouring my own blank. I have always wanted to get into some foundry work but I'm not quite ready to build a proper foundry yet. I have been looking on youtube and seen a few videos of people doing "one off" castings with a make shift foundry dug in the ground using house bricks.

What are your collective thoughts for such an approach in my circumstances? Can I obtain the required temps using such a system? Also, I don't want to fuss around with a gas burner just yet, but look forward to making a Reil style burner some time later. Can I achieve such temps with say heat beads and a petrol blower or would I need coal or coke?

In terms of the pour and the casting, I have a stainless round and flat bowl that is about the correct size I need, can I just melt the bronze in this and let it cool inside the pot rather than pouring it into a mould and then carefully destroy the pot to remove the cast?

Lots of questions I realise. I guess the key questions are will this simple foundry work? Can I achieve melt temps with heat beads? Can I melt AND leave the bronze in the pot, as in can I use this pot as both a crucible AND the mould to keep things simple?

I can't wait to get into some casting andtake the time to make a proper foundry using correct refractory materials but right now I just want to cat a one-off gear blank.

In terms of protective equipment, I intend to wear a Kevlar impregnated firefighting garment, gloves and face shield. Any other safety considerations I need to work out would also be much appreciated.

Thanks guys,

Simon

[Oldneweng]

Simon I have made a single pour with brass, heated with heat beads and a vacumn cleaner blowing. I have a short length of steel pipe about 300mm in diam. I made a crucible from some 100mm pipe with a plate welded on the bottom. I only managed to melt a small amount but it was only a try out and did not have a lot of beads in plus a bit of time getting things working properly.

So I would say it was possible. I await the results as it was me who suggested casting a blank although you may have already considered it.

Dean

[Oldneweng]

Another easy method for a mould is known as lost foam casting. cut a bit of polystyrene foam to suit the blank. Bury this in a bucket of sand. poke a sprue (chopped off cone) made of foam to pour the metal in. One or more drinking straws also poked in to provide an exit for gasses. This is just a rough idea and can be researched on the internut. This will require a crucible of some sort though.

Dean

[SawDustSniffer]

steel crucible is not recommended for copper as the copper will alloy and desolve the steel , Stainless steel is worse than steel ,for a 1 off pour steel 6mm thick will work , SSpan wont , BBQ beads with forced air should get to the copper melt temp , you will add iron to your alloy

a simple sand mix mold will dry out and collapse before the melt has melted , so i would suggest a pour into a sand cast , yer a foam core sand mold

[simonl]

Hi all,

Thanks for the comments and help so far. I have made the "foundry". Whether it works is yet to be seen. I assume the biggest issue is heat loss and whether the heat generated can heat up and overcome the heat lost. Also, I hope I have not made it too big. The idea was to have just enough room from the crucible and the coal surrounding it. Be interesting to see what the bricks look like after. I'm not expecting them to survive much past a single pour?

It will be air fed by an old vacuum cleaner motor married to a steel pipe that's fed from underneath. As a crucible I will be using a CO2 extinguisher cut in half. It's about 80mm diameter. I worked out I need about 500ml or about 4.5 Kg of bronze for the pour. The casting part I have decided to use dry sand and mix my own bentonite (crushed up kitty litter) to produce the casting sand.

I'm thinking I will use briquettes. I'll be off to get some tomorrow, I assume they will produce at least as much heat as heat beads?

Some pics so far...

269795269796269797269798

Cheers,

Simon

[SawDustSniffer]

heat the bricks slowly as any moisture might cause the bricks to explode , a hand full of brickets for 2 hours with out forced air

heat loss should be ok , just add more fuel more air

the air should enter pretty well centered under the crucible , coal will insulate its self , strange stuff , you might end up with flame around the sides not in the middle ( no air ) i cant see where the air enter's

a cut down co2 extinguisher only lasted 3 pours in my furnace with aluminum , there only 3mm thick at the most , the crucible will burn through before it melts , 6mm min and i recommend a graphite crucible , steel will burn through

put some crushed brickets in the crucible on top of the bronze to stop it oxidizing, and hold the coal back when you pour with a flat stick ( 3 hands ) , or borax powered to form a cover , melting bronze takes a while so expect it to take time ( will have to replace the burn beeds 2x ) and when your about to give up , leave it for 20min

some sort of air control is needed , a flat stick 1/2 over the vacuum motor , encase the beads start to levitate from air pressure and blow out of the furnace

a flame shooting nice and powerfull about 1 foot out the exhaust is what you want adjust the air to get there ( a consistent job with beads ) , dont even check it for 45min , then every 15min , if its not melted in 2 hours , give up
http://i1033.photobucket.com/albums/a413/aussieCFviolin/PPE2_zps0ae9f5c4.jpg (http://www.youtube.com/watch?v=A796N_YZTm8&feature=youtu.be)
click on the image to view a utube of aluminum exploding for no reason

[simonl]

Thanks Sawdust,

What would be better for this, heat beads or briquettes? What has better energy/kg output?

I reckon once I get this pour done and sort out my worm gear I think I'll get the foundry bug and make a proper one with proper materials. I was looking at an old washing machine tub I have & was thinking it may make a nice foundry... :rolleyes:

Edit: I forgot to add that the air intake goes into the bottom just off centre. I should have taken a pic on a different angle so it showed up! Air should enter central under the crucible? I was going to sit it on the brick base. Does it need to be set up above the ground, say on a brick?

Simon

[SawDustSniffer]

beads , bricks , coal ,. it dosnt matter , all within 10% heat out put ,
They will burn where the air is , and insulate where there is no air , if the air comes in from the side , you will get a hot spot on that side with fast burning fuel and smoldering fuel out of the air supply , got any scrap steel peaces you can lay on the bottom under the fuel so air can spread evenly across the floor ? the air will cool the steel and prevent it melting , the heat is above , a steel tube with air holes across the floor ? a peace of mesh ?

if you get the bug , bye a decent PPE then a graphite crucible or 3 , then gas or oil power your hole in the ground , then build a decent furnace

[Oldneweng]

Thanks for the advice from me too, SawDustSniffer. Any suggestions on where one would go to for a graphite crucible?

I have plans to build a waste oil fired furnace eventually as I have lots of it here. First I need to start filtering the oil as that will take some time. Never enough time to do things, sigh.

Cheers

Dean

[SawDustSniffer]

i got my A#10 graphite clay crucible's off ebay for $60 each + postage , the postage is huge for 1 but they bundle mutable purchases
a A10 holds 10pounds of aluminium ( 4.5kg) or about 2lt

my crucibles were made in India , and shipped from USA , you might be able to find a Indian seller of the Salamander A## graphite crucibles

[Oldneweng]

i got my A#10 graphite clay crucible's off ebay for $60 each + postage , the postage is huge for 1 but they bundle mutable purchases

my crucibles were made in India , and shipped from USA , you might be able to find a Indian seller of the Salamander A## graphite crucibles

Thanks SawDustSniffer. I will look into it

Dean

[SawDustSniffer]

you cant pick up a clay graphite crucible with a pair of pliers , when hot there quite soft , and you and squash them easily , you will have to make or bye a set of " lifting tongs " , and a " pouring shank " there easy to make




http://i1033.photobucket.com/albums/a413/aussieCFviolin/PPE3_zpsb0b4dc3a.jpg (http://www.youtube.com/watch?v=A796N_YZTm8&feature=youtu.be)
click on this image for a Utube of aluminum exploding for no reason

[simonl]

Thanks Sawdust. I was wondering what sort of things can go wrong.... and how bad it can get if they do go wrong...

Simon

[SawDustSniffer]

i was trying to show how easily things can go wrong
i drew that up in CAD in hope it works better than me typing "ware face shield , glasses , gloves , apron , chaps , and boots " and newbies saying yer yer i will

i have to add click on this image to the graphic , linking the graphic to a utube was an after thought , copy them at will and post them your self , on any site


too much water in your molding sand will spit molten metal at you as well
judging by the colour of the crucible , that was real hot aluminum , ( yellow 1200c it should have been orange 800c) in a cold ingot pan , wiped out with rag to remove water
1200c is what your aiming for to melt bronze

put any thing the metal will touch over the exhaust port while your waiting for it to heat up , ingot pans , tongs , dross spoon to remove any trace of moisture


lol it hasnt spat at me YET , but it will

i would recommend you you do 3-4 aluminium/ zinc pours before trying copper/bronze , an old muffin pan for an ingot , dross spoon the top , degass with pool chlorine( aluminium ) in a tube ( stand back it spits ) , just practice , learn too crawl before you attempt run

[simonl]

I searched on youtube for foundry explosions and aluminium was very prominent and quite spectacular (as long as you weren't next to it!) I am getting a good appreciation for what can happen and I am gaining much respect for molten metal! Next week I will attempt a phase change of some aluminium!

Simon

[johnc]

Nothing much to add, my experience is limited to lead and some forge work. A clagged vacuum makes a very good air source, hard to beat. i think the vacuum idea will work quite well and if it doesn't you probably will just need to fiddle with the air.