While there was some discussion on ESE re transfer passages, I though that the location of these to the main central core in the mould is important and how to do it. Fletto obviously has his methods, but here is a way as well that we were involved in.
These were done on the basis that the main core incorporates both the exhaust and inlet passages, obviously for a piston port engine.
The darker core is a shell moulding and is around 25 years old. Initially the transfer cores were located into reliefs in the central core, but this provided a poor location and innacuracy. So, these being CL linered engines, we got a finished ported liner, slightly bored it out such that it fitted neatly over the central core and shortened it such that reached to below the BDC position, and locating over the simple parallel sided divided exh passage. The provided a location for the transfer passage cores. Unfortunately I have no cores for these to show.
The white (plaster) central core , for a 2 transfer port engine, is similar as is the location for the roof of the transfer cores. In this case, we 3D printed core boxes that incorporated an arc like wraparound extension to the core. This, in conjunction with the top end location produced an excellent alignment with the CNC machined ports in the liner.
Obviously these are really simple examples.
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