Casting Scrap Aluminium

[Jamie]

I was wondering whether any one have any experience melting and casting scrap Austin Seven castings; damaged pulleys and water manifolds especially, and if so, how it went.

I made a small press tool from Polymorph originally and although it worked it is intolerant of any misalignment. A cast aluminium version would be more robust.

I should be interested in hearing of anyone's experiences.

Jamie

[Chris KC]

Experience, no. I do have a book which I can't immediately lay my hands on, it's called something like "The Backyard Foundry", and is aimed at projects of this sort. I once flirted with the idea, but soon realised that actually doing it would require a little more commitment than I had available. It can be done though and I wish you luck.

[Colin Morgan]

I imagine that you will have already watched relevant Youtube videos on the subject?

https://www.youtube.com/watch?v=FHADGpudizU

[Malcolm Parker]

My good friend the late Stan Whinham had searched for years for a hub cap for one of his vintage Humbers.   Stan decided to cast one out of scrap aluminium.   Having made the mould he banked up the open fire in the lounge, opened the under-floor draught and sat his crucible in the glowing coke.   When the scrap had melted he decided to skim the dross off the top using a piece of bent steel strip.  This resulted in a major pyrotechnical display of sparks and flames upon which Stan's wife Betty, who bore more than a passing resemblance to Thora Hird, came into the lounge and gave him a major rollocking.  Suffice to say that the next day Stan was in B and Q buying paint and the next few days were spent redecorating the bungalow rather than playing in his garage.  He told me that he may have had some scrap magnesium amongst the aluminium he decided to melt.   The irony is that at the next autojumble he attended he found one of the elusive Humber hub caps!
Happy days!

[Andy Bennett]

As a piece of art, a few years back I decided to cast different materials into the shape of a gold bar, title was 'All that glitters'.
I carved a wooden version with suitable logo and 'certification' carved in as markings etc and then made moulds in different materials. The glass version mould was made from silica and took a week to heat and cool down degree by degree in what was our new glass kiln. Luckily we had just had our solar panels installed so I waited for a sunny week.
I also made 2 from metals, one in lead and one in aluminium. The mould was made from a home made green sand mix into a home made wooden box. Both metals were from scrap, the lead came from our roof after an extension and the aluminium from discarded window frames, so not as old as you are thinking of but there were paint contaminants.
I used my forge to melt the scrap so no specific thoughts there other than I made up a solid container to melt the metals in and waited. Skimming off the contaminates was simple, and then just pour into the mould. You have to be quick as it solidifies quickly.
Inspired by my success I also cast a tree stump from the remaining lead I had in stock. That was much more difficult as I had to make a split mould with a couple of risers to let the air out and had to do it in stages as the lead was simply too heavy to pick up too much at a time, but it was really all common sense. That one now sits in the garden and isn't moved very often.
Whilst it didn't concern me you do have to think of shrinkage of c 5-10%.
Lots of caveats regarding fumes and hot metal splashing around etc etc apply.

[AustinWood]

In the mid 60s I used to drive up and down between Cambridge and Dundee where I was at University. I had a 1930 fabric saloon and on one of these trips I drove in company with my friend George in his 34 Box saloon.
We diverted from the A1 to visit Kirby Wiske for various spares.
George needed aspeedo worm drive from the gearbox. John Dalby pulled a gearbox out from the floor onto his bench and smashed it to pieces with a large hammer. He rummaged through the debris for the worm.
He said he always dismantled them that way as he had so many and used the aluminium for casting fan pulleys etc.

[Jamie]

Thank you for all of the replies.

Colin: I haven't watched any videos, but have done some reading on-line. Thank you for the link, which I shall watch.

Andy: thank you for the detailed descriptions. I was thinking of using plaster-of-Paris for the mould, which will be essentially a shallow, shaped dish shape. I had not considered shrinkage, though. Did your finished product turn out smaller than planned or did you just need to pour more metal than perhaps would be expected?

Jamie.

[Nick Lettington]

I thought I had posted about this at length once before. I have several photos of my home set up on an old laptop hard drive... the Speedex projects are taking far too long! 

I'll try to find them later.

Don't use plaster of Paris unless you read up on drying it out. Green sand vents steam... plaster of Paris apparently can shatter with the steam unable to escape.

A split wooden box and green sand work well. You will have to read up on percentages, but you do need to allow for shrinkage. Make up a wooden spree former and put it next to your former so that when you pour the aluminium in it weirs over into the thing your casting and you'll get much a better surface finish.

[Andy Bennett]

Jamie: i made my own green sand from a bag of play sand and a bag of bentonite clay (also known as cat litter) I bought from ebay, total cost less that £15 if I recall and of course can be reused. I have used plaster of Paris in glass casting but it is a pig to dry and can shatter under the first bit of extreme heat if not 100% dry. For glass casting you also have to mix with silica sand and wire mesh for strength.
Regarding shrinkage, I didn't have to worry too much as I was making 'art' rather than something that needed to be of engineering performance or size but certainly I saw a dipping of the top flat surface of the block I was casting. I think that shrinkage is also a more complicated subject causing porosity and/or dipping of flat surfaces, rather than simply making the mould 5% bigger for example. If yours is a large dish shape then you will have to decide if a concave finish is OK or if you make it thicker and machine it back to flat.

[Nick Lettington]

You need to create air vents too... if you position one in the middle of the top and pour until the aluminium flows up out of the vent, you can minimise the dishing of the top surface...