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Poppet Valve Engine - Timing Gears

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

Nigel Taylor

Maching the timing gear directly onto the crank was rather brave for me.

This gives you a feeling for the size of the gears.

The crankcase nose was now machined to allow the timing gear to slot in and mate with the gear on the crankshaft. A hole was then drilled through the nose and a bearing slotted in. At this point I realised that my alignment was not great and so I had to move the hole slightly, luckily it was under size.

Instead of using a drill, I clamped the part to the mill table, fitted the original sized drill bit and aligned the head to the original hole. I then moved the table over the required distance and used a 3mm end mill. This allowed me to realign the hole.

This was all done on a Unimat 3 mill, a very useful small milling machine.

I machined a 4mm caphead bolt down to 3mm diameter and left a 3mm length of thread next to the head.

Even after machining the head of the bolt down I had to create a recess in the crankcase.

The two parts ready for assembly - not finished yet, but a nice feeling to get the timing gears working as this was worrying me.

The crankshaft now rotates, the timing gear meshes and rotates at half crank speed, all looking good, how hard can it be.

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.