Difference between revisions of "Casting a venturi"
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== Core geometry == | == Core geometry == | ||
Whilst the dimensions of venturies will vary depending on the performance of the pump and the size of pipe work with which they are used, the basic geometry remains the same. The inlet cone should be 60° inclusive, and the discharge cone 10° inclusive. | Whilst the dimensions of venturies will vary depending on the performance of the pump and the size of pipe work with which they are used, the basic geometry remains the same. The inlet cone should be 60° inclusive, and the discharge cone 10° inclusive. | ||
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[[File:Venturi_geometry.jpg]] | [[File:Venturi_geometry.jpg]] | ||
Revision as of 20:35, 14 November 2010
This method of venturi manufacture comprises casting lead into a copper pipe mould using cores which create the specially shaped internal voids.
With care these can be manufactured with only the minimum of hand tools. The method involves melting lead (around 327°C) so suitable precautions should be taken when carrying out this process.
Contents
Cores
Cores can be made from several materials, steel, aluminium, wood or even plaster. Each has its benefits and drawbacks:
Steel
Will give an excellent finish to the internal faces of the venturi and is durable. It requires the use of a release agent without which there is risk the lead adhering, making it impossible to remove the cores. A lathe will be required to manufacture steel cores. The ends should be drilled and tapped to accept bolts to facilitate removal after casting.
Aluminium
Will give a reasonable finish but may degrade with multiple use. It doesn't require a release agent but a lathe will be required to make the cores. The ends should be drilled and tapped to accept bolts to facilitate removal after casting.
Wood
Will give a poor finish and can only be used once. Charring may evolve gas as the molten lead is pored worsening the finish. Wood cores do not require any special tools and can be made quite simply by whittling, filing and sanding. A wood csrew can be inserted into the ends after casting to facilitate removal.
Plaster
I haven't tried this yet but if a wood core is pushed into some Plasticine, plaster can be poured into the mould to create a core. Plaster cores will probably not give a smooth finish and will most likely be destroyed when removed. The plaster must be thoroughly dry before pouring the molten lead.
Core geometry
Whilst the dimensions of venturies will vary depending on the performance of the pump and the size of pipe work with which they are used, the basic geometry remains the same. The inlet cone should be 60° inclusive, and the discharge cone 10° inclusive.
Cores dimensions should be as follows:
Where the two cores meet at the throat, some form of location is required to ensure concentricity. The arrangement shown above is better suited to metal cores.
Wood or plaster cores could have flat ends and a small nail or panel pin to aid location.
Body
Casting
Finishing
--Bio-rich-time-poor 12:25, 13 November 2010 (UTC)
