Pump it up

 

While the amount of work still required on both the locomotive and the main engine shell should not be underestimated, much of what we need to do on both aspects of the project is graft. The fuel pump and governor assembly is the last big challenge as it is a complex box of tricks and while we have made good progress with the box (casting complete, as blog entry 19 January 2023), there are a lot of components to go inside it; 90 according to the McLaren spares catalogue (see blog entry for 10 February 2020).

The governor/ fuel pump assembly is highlighted in red, with the fuel pumps themselves being the four small cylinders, mounted on top of the box, with the pipes running off to the cylinder heads.

The casting for the body is currently with John Dunn Engineering for machining.

The blog entry for 16 February 2023 described the progress made in producing new injectors. To function the injectors need fuel pumps. Unlike the injectors we have not been able to source any drawings and there has been a lot of patient backroom work going on to clone these high spec, close tolerance units from the samples borrowed from the MDB2 engine.

The role of the pumps is to deliver a measured amount of fuel to the injectors, at a pressure which is sufficiently high to be injected into the cylinder at the top of its compression stroke. In the case of the MBD4, the fuel is injected at 1,000 psi.

The work carried out by Grange Square Engineering on the injectors was impressive, in terms of price, quality and timescale and we had no hesitation in asking them to quote for the fuel pumps too. As you will have probably gathered from previous reports, finding suppliers who are interested in manufacturing small batches of intricate components can be challenging. The relief in placing an order with a Company, knowing that they will do what you want in a realistic timescale was enormous.

The extract below is from a spares catalogue for MDB2 engines. The columns are ‘Part Number’, ‘6’ is the illustration number (the relevant part of which is reproduced) with the final column being the number off required (for a two-cylinder engine).

Only eight bits, but they do need to be right, exactly right if there are to do the job. The original pump bodies (part No 595) were forgings. While we are particular about how things are made, four forgings is never going to happen and Grange Square have CNC machined these from solid. It looks like there must have been a lot of swarf produced relative to the component size.

Machining the body for one of the fuel pumps (McLaren spares number 595) (image courtesy of Grange Square Engineering)

Replica fuel pump (left) with original fuel pump (right) borrowed from the MDB2 engine.

Another challenging component is the rack which lifts the cam followers which drive the pumps. The arrangement of this rack is different in concept of the MDB2 engine which is our primary source of reference to the one fitted to the MDB4 engine in the Armley Mills winch. We’ve taken our lead from the MDB4 engine. Grange Square has manufactured the new rack from the solid rather than the original forging. It may be politically incorrect to say ‘can you see what it is yet?' But you may need to look at the final illustration to understand the machining process shown in the three photos below.

The end of the rack appearing out the block (Grange Square Engineering)

Radiusing the arm corners (Grange Square Engineering)

A lot of swarf later and things are shaping up (Grange Square Engineering)

The finished product. 

So, nine bits done, 81 bits to go!

MDB4 Progress

 

You have to do a lot of scrolling back to find the last progress report on the McLaren-Benz MDB4 engine, 3 September 2021. This described the decision to dispatch the engine to a specialist restorer of vintage IC engines, Formhalls, to have the bearings re-metalled & the cylinder liners fitted. They are based a Salisbury, which is close to Stonehenge and consequently time moves at a different speed in Wiltshire. Their six weeks of Wiltshire time is two & half years of Gwynedd time. Ironically, when they heard we had had a crankshaft made by Farndons, they had the gall to mock their lack of communication & delivery skills. Mr Pot, meet Mrs Kettle!

Enough bitching, on the 13th March the engine arrived back at Boston Lodge, new crankcase bearings, whitemettalled & bore, big ends re-metalled, and cylinder liners fitted. Credit where it is due, there also find all sorts of little cracks radiating from the cylinder head studs & these have been laser welded up.

Line boring the crankshaft (image courtesy of Farndon Engineering)

The completed crankcase and bearings (image courtesy of Farndon Engineering)

A very sexy row of crankshafts (image courtesy of Farndon Engineering)

Laser welded repairs to cylinder head (image courtesy of Farndon Engineering)

Cylindrical grinding of cylinder liners prior to fitting (image courtesy of Farndon Engineering)

Cylinder liners ready to fit (image courtesy of Farndon Engineering)

Fortunately the return of the engine coincided with a period of leave for Rick, who duly got carried away. Job number one was to remove the plugs giving access to the oil ways. How the lubrication system works was described in the blog entry for 5 March 2018.

The illustration above is diagrammatic; the ‘pipes’ which lead to the crank shaft bearings are, in practice formed of a series of interconnected oilways drilled into the crank case and engine block. There is an oil way from one end of the block to the other, with individual branches leading to each crank shaft bearing location. At the end of each run there is a plug. When you remove the plugs and poke a small bottle brush in this is what you get out:

The cylinder heads had been overhauled earlier in the project (blog 10 April 2021) and in a moment of wild excitement one was trial fitted onto the cylinder block, with one of the MDB2 rocker covers. The rocker cover castings are still in Chris Barrys’ workshop. Wife, Kids, Dog, 7.5” rebuilds, pah! Come on Rimmer pull your finger out.

A frenzy of painting has ensured, so the cylinder block now looks like this, complete with replica McLaren-Benz plate.

It is not just the block that has been painted, the cylinder heads look lovely too

As do the myriad of cover plates etc. Even the MDB2 rocker covers have had a look-in

Next on the agenda is gasket manufacture. One down,

Some way still to go!