When I was making the flea eyes, I also cast a simple rectangular bar of aluminium with a second crucible of metal.
Although it was quite a good casting it was open cast and hence had a rounded top and due to some sand movement the bottom was ridged. I set to work on this with the grinder and flapdisk to get something that was a little more regular which will be of more use when I want to make something from it or machine it. This week I showed off the work in progress at the PSTOIC annual get together.
One of the questions was how many disk drive cases did I have to melt to make a block that size?. I did not actually know so I measured the weight of the block (160g) then weighted some of the casings. The casings varied between 90g for the lightest to about 200g for one of the more solid ones. So an estimate is that the block just took a single drive to make.
I also did a quick density calculation as that was one of the recommendations from the Home Foundry and Casting Group for checking the material type.
160g = 0.16Kg
95x30x20mm = 57000mm³ = 57ml = 0.000057m³
Density = m/v = 2807 = 2.8g/mL
The density of Aluminium should be 2700 kg/m³ = 2.7 g/mL so mine is in the right ballpark but could be a little dense. This could be a calculation error or I may have impurities such as denser metals like zinc, nickle or tin. Due to the accuracy of the scales the best thing would be to have more material to get a better measurement. More casting is planned for 2010.