Is there any particular reason that the whole rod needs to be bronze? Possibly if copying a design that was available as a casting kit then GM castings may have been provided but it would be cheaper to make a marine type steel rod  rod and keep with split bronzes.

I think you would be better off saying where you are and asking if anyone or their club nearby has casting equipment.

A mild-steel rod with bronze journals would be far more in keeping, too. Full-size engines never had all-bronze motion.

Have you all been reading this without looking at the advert at top right for the October issue of ME&W?

Casting is in reach with home-made gear if you have a suitable space.  My back garden is too small, and I try not to annoy the neighbours.   You need:

• A safe space
• A 5 litre or bigger steel can, lined inside and out with rock wool or similar.
• Tongs, crucible and suitable safety gear.
• A brave operator.  Ideally get a jackass who doesn’t believe in H&S to sign a disclaimer!  (Seriously, be careful when handling molten metal with home-made equipment.   Those tongs better not slip or bend!)
• The inside of the rock-wool plastered with a 4mm thick layer of cement, leaving a decent space in the middle.
• A hole in the bottom, protected by some insulating firebrick so the fuel doesn’t fall out or melt the can
• The can stood on some bricks, with a channel underneath connected to a blower.  Wife’s hairdryer will do.  Plug leaks in the channel with cement: a length of steel pipe would simplify.
• The can is filled with charcoal lumps about the size of a walnut and ignited.  Once going, plonk the crucible with a little metal inside on top and turn the blower on.
• An insulated lid with a small vent in the middle, say 25mm diameter, to keep heat in.
• When the initial metal melts, add more step by step.  Easier to melt small quantities of metal than a large lump.
• When melted, lift out the crucible and pour.
• Bigger the better!!!

The secret is the charcoal and the blower.  They produce a high volume of heat at high temperature.  The volume matters most!

• The temperature is easily reached, something over 1000°C.   A doddle with any flame.
• A few kilograms of charcoal contains the volume of heat needed to melt a 100 grams of metal, perhaps more, depending on how well the can is insulated.   A poorly insulated can won’t retain heat long enough, burning fuel to no avail.   Heat is measured in Joules, with charcoal at about 30MJ per kg.   (7kWh / kg)  Temperature is measured in degrees: they are not the same thing.
• The blower increases the burn rate, releasing heat faster than an ordinary fire.  Then the heat and temperature are contained reasonably well inside the can, and the crucible is immersed in it.

The apparatus won’t last long!   The commercial equivalent is made of thicker steel with better insulation usually fired with Propane. A big cylinder is needed.  A well-made gas furnace is needed for repeat work, but the bodge outlined above works.

Worth practising on Aluminium first.  Requires less heat and temperature to melt Aluminium than Bronze.

Bronze isn’t too difficult to melt though and a larger version of the same arrangement will melt cast-iron.  A few metres high, with a bigger blower, made of brick, and fired with coke.   I watched one demonstrated in Wales on holiday.   Impressive!   But the furnace was basically just an insulated tube with a blown fire inside and a lid.  Their version was continually topped up with coke and new scrap whilst two men poured molten metal into moulds.   I bought a trivet!   The scrap looked like mild-steel, but I think they started with some cast-iron, and then added steel to coke already in the crucible.  We grockles weren’t allowed close enough to see.  The men wore gauntlets, google, hats and what looked like thick leather aprons.

The tube approach fails miserably with Tungsten, mp 3400°C, which needs an electric arc.   Also do-able at home if suitably determined.  I’m not brave enough!   Not have I tried melting Aluminium in a microwave:  that works too. but it does the microwave oven a mischief and is a super-scary fire hazard.

Dave

Some people will find a reason to do nothing