Cylinder Liner Fitting –Good News & Bad

 

With the engine block back at Boston Lodge, job No 1 (or more precisely job No 2, after the painting epic) has been to fit the new liners. The manner in which the liners are fitted is a little unusual, as they are secured into the bottom of the block with an arrangement which is akin to a gland. The photo below shows the arrangement before dismantling. The liner clamp is secured by the four studs with the natty, shaped washers and there is a coil spring (in compression) between the washer and the clamp. Looking at the second picture, which shows the clamp being removed, may help understand the arrangement.

With the locked nuts, natty washers and springs removed the liner clamp can be lifted out.

The clamp both holds the liner in place and also compresses an ‘O’ ring, fitted around the liner to form a seal between the liner and the cylinder block water jacket.
The cylinders are off-set slightly from the line of the crankshaft (to ensure that the full force of the cylinder firing it put to good use) and to accommodate this each liner is slotted at the lower end to accommodate the movement of the piston rod. It goes without saying that ensuring the alignment of the liner is correct is critical. Rob Bishop fabricated this simple jig, which locates on the studs and then ensures that the slot in the liner is in the correct location.

With the liner in, the ‘O’ ring can be fitted, some sealant applied and the liner clamp re-fitted. Simples! The need for the jig can clearly be seen in the photo below where liner number 2 is clearly out of line.

One of the liner clamps had a crack;

So Rob fabricated a replacement. The old, cracked liner clamp on the left, new, fabricated replacement on the right.

The photo below, showing the new liner clamp being bored out on the lathe makes the welded construction more apparent.

Back on the engine, this view below shows the fitted liner and ‘O’ ring.

Things don’t always go to plan, the liner clamps are in compression, but the lugs are in shear and cast iron is the best material in shear. When the liner clamps were being fitted the lugs started breaking off. It looks like this one may have been cracked too.

The solution? We are going to get some new ones cast in ‘SG’ cast iron, which is more ductile than the normal stuff. Why didn’t McLaren use SG iron, you may ask? It was not invented until 1943, 15 years after the engine was built. In addition to the change in material the clamp has also had a modest size increase, to beef it up a bit. Thanks to Andy Williams for making a pattern for the replacement component so quickly.

As I expect the majority of people reading this will know, The Ravenglass & Eskdale Railway also had a Kerr Stuart Diesel (Standard Gauge, MDB6 powered) which if you didn’t know, takes a bit of taking in. Thanks, or possibly no thanks, to Neil Glover who forwarded an extract from a contemporary record (reproduced in the R&ER Magazine). It starts…

'we returned to Ravenglass a few days later after a pleasant holiday and discovered that the MacBenz engine had been in trouble.The water joints on the cylinder head and the liner joints had been leaking water into the sump’. After a vivid description of the rather unpleasant task of sorting the mess out it goes on to say ‘the job of renewing the joints was always with us, probably caused by vibration of the engine and also to some extent by a shortage of oil, causing the pistons to get hot. We always had a good stock of rubber joints to replace the faulty ones and as oil often stood on the cylinder heads from the tappets, the rings to seal the water often became impregnated with oil and were made useless’.

Maybe we are about to find out why liners were not often fitted like that. Let’s hope that improvements in rubber & sealants may give us a little bit of latitude.

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.

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!

A Trip Across the Cob

 It would be churlish not to note 4415's trips from Boston Lodge across the Cob as part of the WHR100 celebrations on the 24th & 25th June as progress. 

All of Rob Collins’ lovely paint job will be getting grit blasted off in the next twelve months if we stick to the current plan to rivet up the body next winter, so here are a few views at least to capture some of the many completed components enjoying a trip out rather than languishing in the finished parts store. 

Seen below, meeting up with former Dinas shed mate ‘Russell’ at Boston Lodge at 08:54 on Saturday morning.

Optimistically coupled to a rake of 1920s style coaches below, it looks the part, and is the only decent photo I have showing the radiator & the replica ‘MACLAREN’ plate (cast using an original plate from the road roller).

In the end it ‘double headed’ with Welsh Pony, being somewhat lacking in the engine department.

In addition to allegedly inspiring the streamlining on the A4s, the iconic look of KS4415 may have inspired the architect of Snowdon Wharf.

Eventually the sun came out, just as the loco returned to Boston Lodge on Saturday evening and a posed for a few minutes by the cliff.

Sunday saw 4415 going off shed with the full line up of surviving of Ffestiniog Railway early IC motive power.

The head turning impact of early IC motive power can be fully appreciated when you see the platform in this view of the 1917 build, 40HP petrol powered Motor Rail Tractor and the 1927 build 60HP Diesel 4415. It’s a niche market.

Some of the ‘facts’ in this blog may be made up.