Governor Body

 Lack of blog entries are a measure of personal lethargy, rather than lack of progress, as followers of the Facebook page will know there’s lots of riveting stuff going on, but let’s get some of the blog backlog out of the way first. 

The previous blog entry described the high-tech CNC work undertaken to produce the fuel pumps. These sit on top of the governor casing, the reproduction of which has to date been a painstaking exercise of draughtsmanship, pattern making and founding (blog entries 16th February 2020, 17th October 2021, 19th January 2023). At every stage in the manufacture of this component the words ‘it’s a bit tricky’ seem to crop up. The most recent star of mastering something that is ‘a bit tricky’ is John Dunn of John Dunn Engineering who has patiently machined the casting.

Mounted on a horizontal borer, the first operation was to mill the top face, which will ultimately carry the fuel pumps.     John Dunn Engineering

Another view, showing how the casting was mounted and clamped to the table   John Dunn Engineering

With the casting rotated through 90 degrees the end of the casing, which mounts onto the engine is shown here being faced off. John Dunn Engineering

Now it starts to get tricky! The shaft carrying the governor runs along the whole length of the casting. To ensure that it aligns perfectly the bores on both the left and right hand side of the box area need to be bored without re-setting the machine. Consequently the right hand bore have been machined with a boring bar projecting into the casting. John Dunn Engineering

An ingenious boring bar set up to allow the internal faces of the casting to be machined. John Dunn Engineering

The rather long reamer in the photo above is required to finish the bearings for the spindle of the governor operator bell crank lever. This is the sub-assembly 619 – 622 in the spare parts diagram included in the blog entry of the 10th February 2020. The photo below shows the same area on the MBD2 engine and tries to illustrate and explain how this part of the mechanism works. The lever is on the end of the shaft and is part 620, the fuel reducing claw lever (the kill switch for the engine).

The arm of part 621, the governor operating bell crank lever (which is carried on the same shaft) can be seen (with the low ball joint) inside the casting. The crank arm passes from one cavity of the body to the other via the hole in the top RH corner of the photo with the boring bar. The casting is upside down in the boring bar photo.

This view shows the machined top face of the casting, ready to receive the fuel pump assemblies. John Dunn Engineering

The interior of the machined casting. This end of the body receives the drive from the engine and contains the governor weights.

Even machining up the face of end cover was not a straightforward task, seen here on a vertical milling machine fitted with a rotary table.

Job done! John Dunn stands here with the finished item and the deserved look of pride that is usually associated with big game hunters. It seems rather underwhelming to record just another component has been finished.