1936 BELLIS & MORCOM Overhaul
Unique complete engine overhaul on an operational 1936 water pumping engine for a large utilities company.
K.W Engineering Services were brought in by a large utilities company to assess the damage on a 1936 straight-six Bellis & Morcom engine after it had experienced a catastrophic failure. The engine itself had been used regularly but had not been overhauled for many years. The incident we were investigating was a seizure that had caused a cylinder head to lift off the block and broken both valve cages.
The initial investigation was a process of dismantling the engine and trying to find the cause of the seizure. The cause was apparent once the head was removed, one of the pistons had sheared in half and hit the underside of the head, lifting it off of its mountings and also punching the valves through the valve cages breaking the attachment points clean off. The total number of components written off during this incident stood at 1x Piston, 1x Connecting rod, 1x Cylinder liner, 1x Air intake, 2x Valve cages and 2x Valves. A report was sent to the client advising them on the extent of the damage and the fact that almost no spares were left in their store and no manufacturers of spares or drawings of spares existed.
The client requested the complete overhaul of the engine and the manufacture of the spares required.
The first job was the complete dismantling of the engine to see the extent of the damage sustained over time and find out which other parts would need repairing or re-manufacturing. This process did not prove to be an easy one as almost all the engine specific tools had been lost or broken over the years.
K.W Engineering Services developed a complete new set of tools to assist in the dismantling and rebuild of this engine.
Once the engine was apart and the damage assessed the rectification work began. All components that were not too large to move from inside the installation were transported back to the workshop for in-depth cleaning, further inspection and repairs if necessary. Work carried on at the installation on the crankshaft and crankcase to ensure all areas of the job were progressing and any faults or potential job stoppages could be encountered and rectified early on.
The main problem that we faced was the lack of spares. Luckily there was one replacement liner which we could use but other than that everything had to be manufactured from scratch. Both the pistons and connecting rods had to be reverse engineered from the existing serviceable components with new drawings developed to send off to the pattern makers. Once the new castings were received they were checked and machined by our skilled team of machinists. The valve cages with the broken attachment points were repaired through a method of cast iron welding and were once again serviceable.
The second problem that required specialist attention were the bearings and bearing blocks. Over the years the bearings had all begun to pick up causing large amounts of damage on the running faces. This damage can prove catastrophic if it is allowed to escalate too much as it will eventually seize the crankshaft.
The bearings were all cleaned and any debris that had accumulated was removed ready to be sent away to a specialist company to be re-white metaled (Babbitt). Once the bearings had returned their dimensions were inspected and the main bearings were put back in the crankcase ready for the fitment of the crankshaft.
To ensure smooth running of the crankshaft a process is carried out that involves applying engineers blue to the shaft and turning it in the bearings to locate any high spots. The crankshaft is then removed and the high spots are scraped by hand. This arduous process is repeated again and again until all bearing faces fit perfectly around the crankshaft.
Thorough crack detecting, using a couple of different methods, was carried out on all heads to ensure that no damage had been sustained during the incident. They all passed and were all then rebuilt and pressure tested. Any of the components that were damaged were repaired and all components were completely overhauled and inspected. The engine was then rebuilt with all brand new seals and put through a rigorous testing and commissioning process.
The finished article. A 1936 Bellis & Morcom straight six completely overhauled and in regular use to this day.
Since the overhaul of the first engine K.W Engineering Services Ltd have been commissioned to carry out complete overhauls on another two identical Bellis & Morcom engines at this installation with more to follow. All these engines are in regular use so maintenance planning and rapid turn around are the keys to successful completion and customer satisfaction.