Having completed the engine frame and base my next job was to machine the cylinder. The cylinder bore on the plan is given as 3/8″ – 9.5mm. As I have a 10mm reamer I upped my bore size to suit. This I have done a few times with Elmer’s engines and it has never given me a problem. The depth of bore is critical and I stuck with the plan dimensions and finished off my bore with a 10mm end mill to give a nice square cut to the bottom of the hole. I took great care to ensure that the depth of hole was spot on or as near as I could get it.
I decided to add a bit of interest to the outside appearance of the cylinder by adding fins. I seem to have a thing about fins on engine cylinders. I guess it’s because ultimately I would like to build a model of an internal combustion engine. However, here are some pics of this next stage. Click on image for larger pic. By the way I have used a new edge finder on this project. My pal Bogs alerted me to this little gem, available at a very reasonable price from Arc Euro Trade – usual disclaimer.
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- After centre drilling I drilled with a 3mm bit with a brass tube sleeve to ensure correct depth.
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- I progressively increased drill size up to 9.5mm reducing lathe speed for the larger drill sizes.
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- Reaming finished bore at 10mm with a very slow speed setting.
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- The bore of the cylinder was bevelled at the base to provide clearance for the con rod.
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- A useful, and easy to make, carriage stop enables repeat turning cuts to the same point. Here I set the travel to 4mm using a 4mm drill bit as an accurate measure.
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- Using my new edge finder I locate the centre distance between the vice jaws which is the same as a centre point of the brass bar. Spot on for locating the inlet hole.
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- A 1mm rotary saw blade is used to cut dummy cylinder head cooling fins. A little bit of work is needed with the calculator to ensure correct spacing.
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- Finished cylinder with engine frame mounted on base.
