Line Boring of a Locomotive’s Diesel Engine Block

Our in-situ machining specialists recently carried out line boring of the main bearing pockets on a 20-cylinder, two-stroke engine. The engine is installed in an American-built diesel-electric locomotive and operates in Scandinavia.

Line boring became necessary due to the seizure of three main bearings. We performed the repair work in our workshop in Gothenburg, Sweden.

We routinely carry out line boring on all kinds of diesel and gas engines, mostly on main bearing and camshaft bearing pockets, or to install sleeves to stop water leaking along the cylinder liners into the oil sump.

This particular job stands out due to the innovative design of the engine. And not only is the design innovative, it was very successful too. Between 1965 and 1983, almost 29’000 such engines were built!

Engine particulars:

  • 20-cylinder V-engine
  • 2’900 kW (3’950 hp) output
  • 230 mm bore, 250 mm stroke
  • 900 – 950 rpm nominal speed
Line boring of the main bearing pockets
Line boring of the main bearing pockets

Innovative engine design

In a nutshell: This engine is very compact, very powerful and it runs at a rather high speed for this size of engine: 900 – 950 rpm. This results in a rather remarkable maximum piston speed of just over 12 m/S at mid-stroke1. Because of its high power and compact packaging, this engine has a high power to weight ratio. This is achieved through innovative design features that are worth looking at. Here we look at three of them.

1) 45 degree angle between A- and B-bank

V-engines are a common configuration for internal combustion engines. In a V-engine, the cylinders are arranged in two banks, which form a “V” shape when viewed from the front of the engine. The angle between these two banks is known as the “V-angle” and can vary significantly between different engines.

Most V-engines have a V-angle of 90 degrees. However, this engine type uses a V-angle of only 45 degrees. This design choice can have several implications for the engine’s performance and characteristics.

A 45-degree V-angle results in a more compact engine design compared to a 90-degree V-angle. This can be particularly beneficial in applications where space comes at a premium, such as in high-performance sports cars, in motorcycles or, you guessed it, in railway locomotives.

However, a smaller V-angle can also result in increased mechanical stress and vibration, as the forces generated by the pistons are not evenly distributed across the engine block. This can lead to increased wear and tear on the engine components, and may require additional mechanisms to counteract the imbalance.

In terms of performance, a 45-degree V-angle can potentially offer improved balance and smoother operation compared to a 90-degree V-angle. This is because the smaller angle allows for better primary balance and reduces vibrations.

In conclusion, while a 45-degree V-angle can offer some advantages in terms of compactness and potentially smoother operation, it also presents challenges in terms of increased mechanical stress and complexity of manufacture. As with any engineering decision, the choice between a 45-degree and 90-degree V-angle will depend on the specific requirements of the application.

2) Non-offset V-engine block

Some V-engine blocks have cylinders that are not offset (when viewed from above), meaning that the cylinders of both banks are exactly aligned. This design is known as a non-offset V-engine block. One advantage of this design is that it results in a more compact engine, as the cylinders are arranged in a more space-efficient manner.

However, there are also some disadvantages to this design. One potential issue is that it can result in increased mechanical stress and vibration, as the forces generated by the pistons are not evenly distributed across the engine block. This can lead to increased wear and tear on the engine components, and may require additional mechanisms to counteract the imbalance.

Overall, the choice between an offset and non-offset V-engine block will depend on the specific requirements of the application. While a non-offset design can offer some advantages in terms of compactness, it may also have some drawbacks in terms of increased mechanical stress and vibration. It is important for engineers to carefully consider these trade-offs when designing an engine.

3) “Blade and fork” connecting rods

The blade and fork type connecting rod arrangement is a unique way of joining two pistons to a single crankpin. In each pair of engine cylinders, a “fork” rod is divided into two parts at the big end and a “blade” rod is tapered from the opposing cylinder to fit this gap in the fork. This type of connecting rod has long found application on for example V-twin motorcycle engines (by BSA and Harley Davidson, among others) and V12 aircraft engines. The most famous example of a “blade and fork” engine is probably the Rolls Royce Merlin aircraft engine. Close to 200’000 such engines were built over many years. They were installed in many very famous aircrafts, such as the North American P51 Mustang, the Supermarine Spitfire, the Avro Lancaster and the Hawker Hurricane.

The advantage of this arrangement is that it allows both cylinders and rods to be in the same plane, as is required by an non-offset engine block. It also makes the motions of the two pistons identical. In the aircraft world, there were additional reasons for using fork-and-blade rods, rooted in history. Both Allison and Rolls-Royce produced V-12 engines which used knife-and-fork rods.

However, there are also some disadvantages to this arrangement. The underlying physics and manufacturing practice supporting plain journal bearings have improved to the point that big-end bearings no longer require the support of a full-width bearing. This means that side-by-side con-rods can now be used instead of fork-and-blade rods, which are more complex to manufacture.

Overall, the blade and fork type connecting rod arrangement has its advantages in terms of simplifying design and making piston motions identical, but it is more complex to manufacture than side-by-side con-rods. With advances in bearing technology, side-by-side con-rods have become a viable alternative. However, the choice between the two arrangements ultimately depends on the specific requirements of the engine design.

Work performed

The work that we carried out to get this 20-cylinder engine block back into good working condition consisted, broadly, of the following tasks:

  • Laser alignment and dimensional check
  • Hardness check and Magnetic Particle Inspection (MPI) to search for cracks
  • Line boring of the 12 main bearing pockets to remove existing fretting corrosion. We machined all main bearing bores to nominal dimension.
  • Blue fitting of the bearing caps

Read more about line boring

1This is an approximation calculated according to the formula PSmax = 250 x π x 950, where 250 is the piston stroke in millimeters and 950 is the engine speed in revolutions per minute

20-cylinder engine block at workshop
The 20-cylinder, welded engine block in our workshop. Note that the gear train is centrally located.
The block turned on its side with main bearing caps removed.
The block turned on its side, main bearing caps removed
Blueing test of the main bearing cap serration
Blueing test of the main bearing cap serration

Metal Baler Cladding and Machining Work

Cladding and milling work

With this short post, we introduce in-situ machining work that we have done recently on a piece of equipment installed in a metal recycling yard in southern Sweden. The assignment consisted of patch welding (cladding), followed by machining work. It was carried out in our workshop in Gothenburg, Sweden.

After many years of compacting car bodies and other metal components , the equipment in question, a metal baler, was in need of repair and modification work. Some of the surfaces on the baler’s crushing panel had been worn and needed to be restored. Thus, the customer sent the 8 meter long, 0.80 m wide and 15 ton heavy crushing panel (sometimes also called “press bar”) to our workshop for repair.

First, our Swedish colleagues replaced any worn material by arc welding (cladding) work. Thereafter, they milled it. In total, they milled off about 5’800 cm3 (350 cu in) of material along the crushing panel’s length and breadth. A portable, NC-controlled 3D axis milling machine was used for the task. The result was excellent and gives a new lease of life to this heavy duty metal baler.

With this post we conclude our short run of examples of us serving the various life cycle stages in the automotive industry.

The baler at its working location in southern Sweden
The baler at its working location in southern Sweden

Our commitment to the circular economy

QuantiServ is very committed to the circular economy. Our offering includes many modern machining and repair solutions that are applicable to almost all life cycle stages of many capital goods. During the last seven posts in this blog have we looked at how we support the automotive industry, all the way from a car’s manufacturing until the end of its life. The same is true for other industries as well and we are going to introduce some of them in the near future.

QuantiServ strongly focus on reusing, reconditioning and repairing in our own operations whenever possible. And we passionately encourage our customers to do the same. The great majority of the solutions in our offering help our customers to keep their equipment in use and to therefore consume less energy and raw materials. In turn, this generates less waste, pollution and emissions.

MERA membership since 2019

QuantiServ’s enduring commitment towards resource reduction and sustainability is demonstrated by our membership in the Association for Sustainable Manufacturing (MERA). We proudly carry MERA’s Manufactured Again Certification Mark, which is a recognizable symbol
that represents the quality, value and sustainability of our processes.

Our numeric controlled milling machine mounted on the 8'000 mm long work piece
Milling machine mounted on the 8 meter long work piece
Milling of the longitudinal side
Milling of the longitudinal side
Milling of the longitudinal side
Milling of the longitudinal side
Press bar about to be shipped back to the customer
Press bar about to be shipped back to the customer

Webinar from the Swedish Club: Dealing with Crankshaft Damage

According to statistics compiled by the Swedish Club, crankshaft damage is the most expensive class of engine damage, with an average claim cost of 1.2 million USD.

In a webinar held on 26 October 2022, a panel of experts from the Swedish Club and from QuantiServ explored the common causes and types of damage to internal combustion engine crankshafts. They also explored different repair options and what can be done to prevent damages from occurring in the first place.

Panelists:

  • Henrik Karle, Technical Manager, The Swedish Club
  • Peter Stålberg, Senior Technical Advisor, The Swedish Club
  • Johannes Roberts, Manager, QuantiServ Sweden
This webinar was brought to you by The Swedish Club in collaboration with QuantiServ Sweden. It was broadcasted live via zoom on 26 October 2022.
Special thanks to the Swedish Club for making it possible. Previous webinars from the Club’s Loss Prevention series can be found here.

Dynamometer Roller Machining in a Swedish Car Factory

Our in-situ specialists from Gothenburg, Sweden, carried out an in-situ machining assignment in a Swedish car factory.

The four rollers of an end of line (EOL) dynamometer had to be machined. Their surface had been found worn and the customer therefore asked us to undersize them by 1.0 mm, so that they could be plated again by thermal arc spraying.

Dynamometer rollers look deceptively small as only a small part of them is visible. They in fact each have a diameter of 1’500 mm and they are 900 mm wide.

Our specialists used one of our NC-controlled, mobile milling machines fitted with a lathe cutting tool for the task. This arrangement worked very well and led to a great result.

In-situ Machining the World’s Largest Four-Stroke Diesel Engines

Ø 64 cm bore, 90 cm stroke, 2’150 kW (2’880 hp) power per cylinder: The world’s largest four-stroke engines are very mighty machines indeed!

These powerful engines were built during the late 1990’s, mostly in a 6-cylinder configuration. With a nominal power output of 12’900 kW, they found popular application as single propulsion engines in multi-purpose cargo vessel of about 20’000 DWT size.

During 20 – 25 years of operation until now, these engines have accumulated more than 120’000 running hours each. In terms of number of engine revolutions, this is equivalent to a car driving for 1.8 million kilometers (1 million miles)!

In-situ crankpin polishing
In-situ crankpin polishing

It is therefore hardly surprising, that after that many running hours signs of wear were found on the crankpins of these engines. As is often the case on medium-speed, four-stroke engines, the crankpins were suffering from what is called “cam effect” or “ridge wear”.

Has your four-stroke engine accumulated around 60,000 running hours or more?

Although the crankpins might appear to be in good condition, it is very likely that they suffer from the cam effect (also known as ridge wear) and are in need of machine polishing. If this is not done, then you might face a failure soon!

Read more

Usually, then the cam effect will manifest itself in two ways:

  1. Through uneven wear in horizontal direction, with nearly no wear at the centre of the pin and at the edges, but with easily noticeable wear to the left and right of the oil bore.
  2. The pin is not affected evenly throughout its circumference. The cam effect is usually most pronounced at about 30 – 45 degrees after Bottom Dead Centre (BDC). For this reason it is called “cam effect” – the pin is not perfectly circular anymore.

QuantiServ appeals to owners and operators of medium-speed four-stroke engines to sensitize the crew about the cam effect. We highly recommend that the pins are carefully checked whenever an engine overhaul or bearing replacement is carried out. If any uneven wear patterns are detected, then the pin must be machine-polished to restore its proper geometry before any new bearings are installed and the engine is restarted.

If the cam effect is detected in good time, then machine polishing of the pins is usually sufficient to correct the problem. After machine polishing, the crankshaft will be ready again for several years of continuing operation. Whether standard bearings or undersize bearings will have to be installed after polishing will depend on the actual situation.

If, on the other hand, the cam effect goes undetected for too long, then a crankpin failure is almost inevitable. Such was also the case here on the first engine. Heat treatment and machining was therefore necessary and was swiftly carried out by our Swedish specialists. Having seen the excellent result and now aware of the cam effect, the customer tasked us to machine polish all pins on this engine and on the sister vessels, which is why we eventually polished about 70 pins in quick succession but in different ports.

In-situ heat treatment
In-situ heat treatment (annealing)
Crankpin machining
Crankpin machining
Completed crank pin
Completed crank pin

All work described above was carried out on board by our Swedish in-situ specialists. They were supported by our reconditioning experts that meanwhile worked on those engine components that were removed from the vessel for an intervention ashore. These components were sent to our reconditioning centre in Kruiningen, The Netherlands, where they underwent  thorough overhauling and machining works.

By the time of writing in August 2022, we have overhauled around 70 cylinder heads and have re-bored a similar quantity of big end bearing housings. Machining the big end bearing housings became a necessity due to excessive ovality in the bore.

Newly overhauled cylinder heads in our workshop
Newly overhauled cylinder heads in our workshop
Big end bearing bore machining
Big end bearing bore machining

Comprehensive Repairs: We Succeed Where Others Fail

Example of a Comprehensive Crankshaft Repair Assignment, Started and Then Abandoned by a Competitor

During the last days of 2020, our in-situ repair specialists out of Gothenburg, Sweden, repaired a damaged crankpin on a Korean-made four-stroke engine. The engine has a 32 cm bore and a 40 cm stroke and is installed on a 5 year old, 9’200 TEU container vessel.

When contacted by the ship owner, we proposed to carry out an inspection on board. The shipowner agreed, whereafter our specialist from QuantiServ Panama carried out a thorough inspection in Panama. To our disappointment, the ship owner then awarded the repair work to another company. Their technicians machined the pin to – 0.80 mm undersize and then gave up and disembarked from the vessel.

Finding himself in a tight spot, the customer came back to us and asked us if we could continue the repair that was abandoned by the other company. We took the opportunity to demonstrate that we succeed where others fail. Two in-situ specialists from QuantiServ Sweden joined the vessel and successfully carried out the repair work while  underway from Lima, Peru to Manzanillo, Mexico. They solved the problems as follows:

Issue Action taken Result
Damaged surface and cracks Machining Crankpin under-sized to – 3.00 mm
Excessive hardness Heat treatment (Annealing) Hardness Reduced from 620 HB to 255 HB
Bent crankshaft Peening Run-out reduced from 0.27 mm to 0.03 mm

The customer was very happy with the skills and performance of our specialists. He therefore kept them on board for subsequent reassembly and overhaul works and he also asked us to supervise an  overhaul of a similar engine installed on a sister vessel.

Jaw Crusher In-situ Machining, 700 Meters Underground

In November 2018, our in-situ specialists carried out machining work in one of the world’s most modern underground mines, located in central Sweden. The mine processes about 2.5 million tones of ore annually and produces gold, silver, zinc and lead.

The assignment lasted about a week and consisted of milling, drilling and tapping work on a large jaw crusher located at a depth of 700 meters. There, the ore is crushed before it is hoisted to the surface for further processing.

Our specialists machined the upper section of both the stationary and the moving jaw. On each jaw, they milled off about 26,000 cm3 of steel and then drilled and tapped them so that a newly fabricated section could be bolted on.

QuantiServ’s In-situ Machining Specialists are Very Highly Trained

The last few weeks have been a busy period for our internal trainers at our in-situ training center in Gothenburg, Sweden. Courses were scheduled back to back. In-situ machining colleagues from around the world were undergoing refresher training on a variety of topics: in-situ crankpin machining, in-situ heat treatment (annealing), engine block machining, etc.

At QuantiServ, we very highly value formal training. All our in-situ machining specialists undergo rigorous training and assessment when they first start to work for us. And it does not stop there. As we constantly keep on further developing and improving our tools and processes, we regularly call the in-situ machining specialists that normally are stationed all around the world back to our in-situ training centre in Sweden to equip them with the most updated skills and knowledge.

This was the case with colleagues from Italy and Brazil that joined a training course last month. Even though some of them already work for us for ten years or more, there are always new tricks that they can pick up. A lot of knowledge sharing and networking takes place during these courses too. The trainees meet with our designers and tool developers and provide them with valuable feed-back and experience from the field. This information then flows into the next generation of tools so they become ever better and more efficient. It is highly trained machinists and cutting edge tools that keep QuantiServ at the forefront of the in-situ machining industry.

Crankpin machining training

Crankpin machining training

Crankpin machining training

Crankpin machining training

 

 

 

 

 

 

 

 

In-situ heat treatment training

In-situ heat treatment training

In-situ machining specialists from Italy

In-situ machining specialists from Italy

 

 

 

 

 

 

 

 

Our Brazilian colleagues proudly showing off their renewed certification. Notice the quality of the pin surface.

Our Brazilian colleagues proudly showing off their renewed certification. Notice the quality of the pin surface.

 

 

 

 

 

 

It’s All in a Month’s Work for QuantiServ’s In-situ Machining Crew!

On board various ships and oil rigs, in power plants and in factories: Far from being idle during the holiday season, during the month of July our in-situ specialists were maintaining and repairing our customers’ equipment in 26 different countries, across four continents. No other in-situ machining company has such global reach and completes more projects than QuantiServ. Wherever the location, whatever the damage – it’s all in a month’s work for us!

Explore the interactive map below and discover what services our in-situ engineers have been providing to our customers during the month of July 2017.