> I see I sent this to the wrong address originally.
> Try again.
> I have a requirement to cast a special Aluminium* part. Very low tech
> and low tolerance requirement. Precision and material composition are
> suitably undemanding that I may even be able to do it with no prior
> experience of metal casting. But maybe not :-)
>
> Any comment on home casting to meet my requirement would be of
> interest. If this is ever going to happen (and odds are it isn't) it
> would have to be reasonably easily accomplished. This seems possible
> but past experiences with Murphy suggests otherwise.
>
> This page offers large amounts of apparently useful material on the
> subject.
>
>         http://www.backyardmetalcasting.com/index.html
>
> This page offers some brief but useful advice re the effect on iron
> content caused by using iron crucibles.
>
>         http://www.smokstak.com/forum/showthread.php?t=33715
>
>
>             Russell
>
>
>
> ___________
>
> FYI I'm (only) considering casting a "heat sink" for my wood burner to
> greatly improve it's useful heat output. This is a metal box with a
> high temperature 'glass' door. The firebox hangs inside a larger steel
> air sleeve. As built heat output from the fire is a very small
> percentage of that produced by the fire.
>
> Only the external top of the firebox is easily accessible.
> By placing various forms of heatsink on the top of the firebox and
> then blowing air around the air sleeve we get far far more heat out -
> probably about 5 times as much - maybe more. The informal heatsinks
> are OK but it's obvious that if I fitted a single heatsink covering
> the whole top of the firebox and suitably finned it that I could get
> an optimum amount of heat out by adjusting air flow. A cast aluminium
> top plate 'simply' needs to make good enough contact with the steel
> firebox top and have adequate finning. Fin surface need not be high
> quality or even especially even. The plate bottom may benefit from a
> post casting 'skim' but if it can be flat within a few mm overall it
> would probably suffice.
>
> Top surface is about 500mm x 500mm and total available height for
> heatsink is about 90mm. That's a LARGE heat sink by most standards.
> Doing this with commercial heatsink sections (even available surplus
> ones) would be prohibitively expensive.
>
> Heatsink could be cast in several smaller sections. Depending on fin
> to total volume ratio this could get rather heavy. Space described
> above is about 25 litres. At a 20% volume fill that's about 14 kg of
> Al. How dense the finning can or should be depends on airflow
> requirements and I haven't yet come to grips with what's required to
> calculate this. A modestly forced blown system (as at present) is
> probably best. The upper limit on air blowing rate is my wife's (low)
> tolerance of fan noise.
>
> An alternative is spot welded thin fins on a thickish Al sheet. Gets
> quite expensive if you can't utilise scrap.
>
>
>
> * Where you are it may be an Aluminum part. Here it's not :-)
>
>
>  

>I see I sent this to the wrong address originally.
>Try again.
>I have a requirement to cast a special Aluminium* part. Very low tech
>and low tolerance requirement. Precision and material composition are
>suitably undemanding that I may even be able to do it with no prior
>experience of metal casting. But maybe not :-)
>
>Any comment on home casting to meet my requirement would be of
>interest. If this is ever going to happen (and odds are it isn't) it
>would have to be reasonably easily accomplished. This seems possible
>but past experiences with Murphy suggests otherwise.
>
>This page offers large amounts of apparently useful material on the
>subject.
>
>        http://www.backyardmetalcasting.com/index.html
>
>This page offers some brief but useful advice re the effect on iron
>content caused by using iron crucibles.
>
>        http://www.smokstak.com/forum/showthread.php?t=33715
>
>
>            Russell
>
>  
>

> I see I sent this to the wrong address originally.
> Try again.
> I have a requirement to cast a special Aluminium* part. Very low tech
> and low tolerance requirement. Precision and material composition are
> suitably undemanding that I may even be able to do it with no prior
> experience of metal casting. But maybe not :-)
>
> Any comment on home casting to meet my requirement would be of
> interest. If this is ever going to happen (and odds are it isn't) it
> would have to be reasonably easily accomplished. This seems possible
> but past experiences with Murphy suggests otherwise.
>
> This page offers large amounts of apparently useful material on the
> subject.
>
>         http://www.backyardmetalcasting.com/index.html
>
> This page offers some brief but useful advice re the effect on iron
> content caused by using iron crucibles.
>
>         http://www.smokstak.com/forum/showthread.php?t=33715
>
>
>             Russell
>
>
>
> ___________
>
> FYI I'm (only) considering casting a "heat sink" for my wood burner to
> greatly improve it's useful heat output. This is a metal box with a
> high temperature 'glass' door. The firebox hangs inside a larger steel
> air sleeve. As built heat output from the fire is a very small
> percentage of that produced by the fire.
>
> Only the external top of the firebox is easily accessible.
> By placing various forms of heatsink on the top of the firebox and
> then blowing air around the air sleeve we get far far more heat out -
> probably about 5 times as much - maybe more. The informal heatsinks
> are OK but it's obvious that if I fitted a single heatsink covering
> the whole top of the firebox and suitably finned it that I could get
> an optimum amount of heat out by adjusting air flow. A cast aluminium
> top plate 'simply' needs to make good enough contact with the steel
> firebox top and have adequate finning. Fin surface need not be high
> quality or even especially even. The plate bottom may benefit from a
> post casting 'skim' but if it can be flat within a few mm overall it
> would probably suffice.
>
> Top surface is about 500mm x 500mm and total available height for
> heatsink is about 90mm. That's a LARGE heat sink by most standards.
> Doing this with commercial heatsink sections (even available surplus
> ones) would be prohibitively expensive.
>
> Heatsink could be cast in several smaller sections. Depending on fin
> to total volume ratio this could get rather heavy. Space described
> above is about 25 litres. At a 20% volume fill that's about 14 kg of
> Al. How dense the finning can or should be depends on airflow
> requirements and I haven't yet come to grips with what's required to
> calculate this. A modestly forced blown system (as at present) is
> probably best. The upper limit on air blowing rate is my wife's (low)
> tolerance of fan noise.
>
> An alternative is spot welded thin fins on a thickish Al sheet. Gets
> quite expensive if you can't utilise scrap.
>
>
>
> * Where you are it may be an Aluminum part. Here it's not :-)
>
>

>
> Russell,
>
> Probably 15-20 years ago I can remember my uncle casting a new mount for
> his outboard motor (essentialy a very thick wall alloy tube).  As he worked
> for my grandfathers agricultural engineering business, he probably had
> somewhat better facilities than you might, but it was a crude operation
> nonetheless.  The raw material came from old tractor pistons, of which a
> plentifull supply was available.  The alloy was melted in a heavy steel
> container using oxy-acetylene, and the mold was simply made using the outer
> steel housing of an old oil filter and a piece of steel tubing in the
> center, with one end capped.  After maching the mount was put into many
> years of service, and as far as I know is still working fine.
>
> Regards
>
> Mike
>
>