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Poppet Valve Engine - Cylinder

|Crank | Crankcase | Cylinder | Cylinder Head | Cylinder Liner | Flywheel | Spark Plug | Timing Gears

Nigel Taylor

Weirdly I started with the cylinder and the air cooling fins. These were a challenge in their own right as they needed quite deep parting tool cuts and my initial challenge was keeping the tool lined up and running perpendicular, it had a tendency to bend and go off at an angle.

Parting Tools

There are a number of key parameters to remember when using parting tools:

  1. height is exactly on centre
  2. cutting angle = 35 for aluminium
  3. ensure the holder is tight with just enough overhang to make the cut
  4. use plenty of cutting fluid
  5. Lock the saddle
  6. Low speed - 150rpm or less
  7. Use parting blades that are at least 12mm deep
  8. Check alignment, then check again
  9. Hone the tool on a diamond abrasive

Parting tool being used to make first cut

Larger parting tool used to complete the step

Design Note

  • Increasing the number of cooling fins increases the cylinder cooling. However, the cooling may decrease with an increased number of fins and reduced spacing at stationary to low speeds. This is due to the fact that the air does not flow well between the fins at low flow speeds.
  • At low speeds the temperature on the leeward side increases and this results in cylinder bore distortion.

Check the angle carefully to ensure you have set this at 3°.

Locking the saddle before machining the taper keeps everything stable.

The cylinder with all of the lathe operations complete.

The fins were finished with a fine wire wool whilst it was still in the lathe. A small amount of cutting oil works very well with wire wool as a final finish on aluminium.

Index Page for the Poppet Valve Engine

If you have made a similar engine and would like to share your experience we would love to hear from you - ed.