Mako Burner

[bmac2]

Torontobuilder, Cogsy.
Take it the wrong way? How? I agree with both of you. In review I won’t be doing it again until I get my hands on some PPE, something to lift the crucible with, and a proper sand setup to pour in. I have a much better understanding now of just what 1500 degrees really is.

 

[RichD]

Good attitude towards the safety advice.

One small thing I noticed was when pouring, you started on the hole closest to you, then you had to reach across the just poured items to pour further out. Another exposure!
Rich

 

[RichD]

Last year I was given a brief tour of a small aluminum/brass foundry nearby. The top edge of the pot (as big as a garbage can) with the molten aluminum was ~chest high. There was a sturdy stone ledge all the way around the pot for protection and the ledge was used as a fulcrum for the dipping ladle handles. That added a lot of security for the workers since they only had to dip and rotate the handle using the ledge to support the ladle.

The ladles had handles about 36" (or more) long. The "spoon" end was just a section of pipe butt-welded to the end of the handle near the top edge of the pipe. The pipe was about 1-1/12" in diameter and about 5 or 6 " deep.

Your crucible is about twice a big as the ladles I've described, but you might be able to fashion a permanent handle to the top edge for pouring. They also had a pouring lip formed into the top edge like a regular measuring cup has.

Oh, and the most important part...the guy pointed to the ceiling about 30ft above and said...sometimes moisture in the pot makes it "spit". There was spattered aluminum stuck to the ceiling. It was a good tour, and my wife got to see how the custom bed frames were made in the factory.

Rich

 

[canadianhorsepower]

and see that he has added a blower to his furnace and it sure looks impressive.
https://www.youtube.com/watch?feature=player_embedded&v=ZjGT8ZAVnts

Nice build interesting
I dont know if you notice but he's using 220 volts source
If you plan to do the same thing youll go with out adaptor

cheers

 

[bmac2]

Hi Luc
Myfordboys in the UK so yep 220v. It sure looks to improve the performance of the furnace but I don’t think I’ll be looking at anything like that for a while. The Troll is made from a couple of coffee cans and I honestly feel that the Mako is almost too much burner for this small a furnace already. If I keep with this I’ll want a solider setup. I’ve seen a few rigs made from 20lb propane tanks and the size seems a good fit for hobby casting. I was talking to a local propane supplier about a new tank with no valve and he wasn’t sure (no one has ever asked for one before) but he figured it would be under $20.00. The idea of cutting into a USED propane tank just doesn’t appeal to me at all.

 

[Cogsy]

The idea of cutting into a USED propane tank just doesn’t appeal to me at all.

I have an out-of-date tank in my backyard that I'm going to attempt to cut open. It seems you can unscrew the valve reasonably easily and safely, then I'll flush it thoroughly and it should just be an inert metal cylinder.

It's on my to-do list for the near future so if I suddenly stop posting you'll know it went badly...

 

[bmac2]

I have an out-of-date tank in my backyard that I'm going to attempt to cut open. It seems you can unscrew the valve reasonably easily and safely, then I'll flush it thoroughly and it should just be an inert metal cylinder.

It's on my to-do list for the near future so if I suddenly stop posting you'll know it went badly...

I saw one where the guy cut the tank with an angle grinder while it was full of water.
I just thought “Great wouldn’t blow up, I just get electrocuted”:fan:
I had thought of using a nitrogen bottle after washing out and continuously flood the tank but I just don’t know if it would do anything except waste the nitrogen bottle.

 

[RichD]

Bob,
I retired after 42 years in the oil refining business. One thing I've done a lot of is prepare equipment for maintenance during process shutdowns. We would typically water wash the systems and related piping, drain, then steam until the towers were above 200 degrees F, then turn off the steam and follow with nitrogen until all the steam was expelled. You could then safely cut and weld once the equipment was properly isolated opened and aspirated with air blowers and eductors.

Equipment that was in LPG service such as propane/butane was typically just steamed out since there would be no traces left once all the hydrocarbons were boiled away by the steam.

In your case if you depressure the bottle, fill it with water, drill a small hole somewhere in the dome so the water has somewhere to go, then flood it for awhile, you'll be safe.

If you're still worried you can then purge it with with air for 30 minutes via the small hole used as a vent.

Rich

 

[Swifty]

Propane tanks are no problem, plenty of people make small wood burning camping stoves etc. out of them. But drums that have had petrol in them are another story, I wanted to solder a tap on to an old drum years ago, it had been used to store petrol. I washed it out several times with hot water and detergent, well as soon as I put a flame near the tap it soon cleared out any remaining fumes, the resulting WOOMP as the fumes burnt could be heard for quite a distance, the blast of air out the filler hole was quite something. Lesson learnt!!!!!

Paul

 

[bmac2]

Rich . . Paul . . . I’m getting tempted.
So what you’re saying is this is doable? scratch.gif
With no Kaboom?

 

[Swifty]

Yes, very doable. I've seen pictures of furnaces made out of propane bottles.

Paul.

 

[RichD]

If you follow all the advice points posted you shouldn't have any problems.

Bear in mind that the local fire department probably has the same "sniffers" we used in the refinery to determine "LEL" (lower explosive limit) and "VOC"(volatile organic combustibles) prior to welding. You could ask them what they think. Maybe they'll check it for you...or throw you straight in jail for just thinking about it.
Rich

 

[bmac2]

Holly paradigm shift Batman! :wall:
Funny how you can see something every day but after 3:30 it’s out of sight out of mind. We use gas detectors all the time, I just never thought to sign one out for the weekend. It must be just that I’d dismissed a used tank thinking that cutting it was too sketchy.

 

[bmac2]

Well I dropped some coin and topped up my PPE. Not much choice when I know my wife reads these threads. AND I do not want to be these guys. Torontobuilder DON’T LET YOUR WIFE LOOK!

 

[bmac2]

I know I screwed up on my first pour but . . . . OMG.
Anyhow, armed with my new sleeves, split leather apron and chaps (feel nervous wearing backless chaps in the province they made the movie “Brokeback Mountain” in) and my old face shield, gloves, Kevlar boots (trust me, you don’t want steel toed where it can hit -30) my wife will let me go outside to play. Also made a lifting fork and hook for the crucible.

The ingots from my first melt are pretty soft but it was extruded to begin with so I wasn’t expecting much from it. I’ve been reading about ways to improve the quality of cast aluminum this past week and it looks like the best bets are adding silicon, magnesium, zinc or copper.

Silicon hummm nope, don’t have any.
Magnesium, that’s not going to happen, I’ve seen a magnesium fire, so no.
Copper, I can do that.

So my game plan is to try four melts pouring two ingots of each. Three with copper at 1, 2, and 3% respectively. And one with zinc, ok I’m going to toss in a couple of pennies so technically it will be Al-Zn-Cu. Canada doesn’t use pennies any more so I shouldn’t get arrested. ;D
The 1% melt was already in the Troll before I thought to take a picture. Sorry no vids, I forgot to put the chip back in the camera and the internal memory is very limited.

 

[bmac2]

The three pictures below are:
Raw extruded aluminum, very soft and gummy
1% copper, better grain and not as gummy
2% copper looks and cuts much better.

 

[bmac2]

Unfortunately this is as far as I got with my experimenting with alloys. On the third melt something went very wrong. I fed the Troll the first ingot and was waiting for it to melt before adding the copper and the second one. When the first one looked ready I went to give it a stir and as soon as I touched it with the rod it froze. The whole thing turned to 244 grams of thick sludge. I know I’ve read something about this happening but I can’t remember. I’m not sure if the crucible is salvageable. I might try putting it in the Troll upside down and see if I can melt it out. It must be the kid in me but I was really looking forward to tossing in those pennies.

 

[Swifty]

The third picture looks like you were almost there, would you be better using aluminium from old mower crankcases or similar instead of extruded. I have no idea what happens in the casting process to the additives in the parent material, are certain elements burnt out or do they remain. If you started off with a good grade of aluminium, do successive melts and repours lose some of the elements in there, like copper or zinc.

Paul.

 

[bmac2]

The third picture looks like you were almost there, would you be better using aluminium from old mower crankcases or similar instead of extruded. I have no idea what happens in the casting process to the additives in the parent material, are certain elements burnt out or do they remain. If you started off with a good grade of aluminium, do successive melts and repours lose some of the elements in there, like copper or zinc.

Paul.

Hi Paul
Ya I really wish I got the last 2 melts done. I think the 3% copper would have been a keeper. And I’m still going to run them I just have to solve that happened with that last melt first.
I think it says in the Backyard Foundry Bible somewhere “thou shalt cast upon thy molds that which has already been cast”. I’ve got a small stash of good cast scrap but I’m saving it for when I know what I’m doing. I’ve found that you don’t have to even look for extruded aluminum it will find you. As soon as word gets out that your building/have built a foundry suddenly all your family, friends and neighbours remember the old aluminum screen door they replaced that’s been sitting in the corner of the garage for 5 years. Ok. First they think you’re crazy, and then they remember the door, bent ladder etc. We are literally surrounded by the stuff and if you’re willing to clean it up . . . . .
I’ve got a couple of good sources (auto industry) for cast scrap but I haven’t asked them for more than a couple of pieces yet for fear they will come by one night and fill my back yard.
I’m no expert on metallurgy (I read a book once *club*) but I do know that one of the ways to purify an alloy is to burn out the impurities. Zinc I think would cook out pretty quickly if the melt was over heated. A lot of the stuff I’ve been reading lately on improving alloys is still all Black Cats and Pointy Hats to me but with one session open to the article and another on Wikipedia I’m stumbling forward.

 

[bmac2]

Winters back. With highs chasing -20 over the past couple of days I’ve had lots of time to think about my crucible freeze. Looking over my notes (yes I take notes) and comparing them to my first melt I think with a little help from Alloy Avenue, I’ve come up with what went wrong. At no time in my second melt did the Troll look like this.