Double Eccentric for the Burrell

A double eccentric for the Burrell will give forward and reverse. As this engine is tiny I machined the pair as one. This was machined from a piece of 1/2″ diameter mild steel. My steps were:

  1. Cutoff ~50mm length of 1/2″ diameter mild steel round bar
    1. More length than required to ensure stable holding in collet
  2. Machine collar step for grub screw – Warco WM240B
  3. Mount in square ER25 collet block
  4. Mount square collet block in independent 4 jaw chuck
  5. Centre round bar using DTi (I used a digital DTi)
  6. Relax one of the jaws on the 4 jaw chuck
  7. Rotate so this relaxed side aligns with the Dti
  8. Move the jaw opposite the relaxed on inwards 1mm
  9. Rotate the chuck by hand and check the offset both sides
    1. carefully tighten all jaws and recheck the measurements
  10. Machine the eccentric
  11. Now repeat steps 6 to 10 moving the part to a 1mm offset in the opposite direction.

Hopefully the video will give an idea of the workholding and DTi arrangement.

I need to carefully clean up this double eccentric for the Burrell, drill and tap for the grub screw and then I can get on to making the eccentric straps.

silver soldered crankshaft

Crankshaft from Parts

Making the Burrell crankshaft from parts has allowed me to then have a split. The split is at the crankpin end allows me to then have a single piece connecting rod. Over 12 months ago I was concerned with the crankshaft to firebox clearance. Splitting the crankshaft means I can have a single piece conrod big-end.

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