Weathering the Dogger Bank challenge I was interested in the article on the Mono Bucket wind-turbine support system (“Firm foundation,” PE July). If the Mono Bucket is successful, then these revolutionary supports could make a big contribution to the success of the wind-turbine arrays to be constructed on the Dogger Bank, and hence also to the UK renewable energy programme and the economy.
The article was understandably upbeat and enthusiastic about the prospects for the Mono Bucket.
There was, however, no mention of the setback that occurred when one of two Dogger Bank meteorological masts using the Mono Bucket support system was severely damaged during installation and had to be returned to Belfast for repair, thus missing a critical weather window and delaying completion of that part of the project by several months.
If the Mono Bucket support system runs into difficulties when applied to a relatively light met mast, is it really the optimum support for massive wind turbines of up to 8MW rating? A met mast is not subject to lateral forces or overturning moments comparable to those generated by the wind force on the rotor of a large wind turbine.
Apparently the Dogger Bank seabed is not a homogeneous smooth surface. Some of it is composed of a striated mixture of hard rock and loose sand, which can pose serious difficulties for any structural support system.
After severe storms, the seabed level can apparently change by as much as 8m overnight, potentially transforming what was nice smooth sand or gravel one day into hard uneven rock the next. How would an Mono Bucket support system behave in such a situation?
Ian Crossley,
Camberley, Surrey
Spring failure mystery
I am intrigued as to why it is common now for car suspension coil springs to fracture during service.
Having had two such failures on a Vauxhall and one failure on a Ford within the past three years, I have asked both franchise and non-franchise garage staff for their views.
I was amazed how common these failures are across modern car fleets. Although the information was anecdotal, all repair organisations I spoke to said this was now a big problem, whereas it had not been one in the past.
The reasons suggested by the repairers were, typically, “the poor/cheap steel that is being used in these springs”, “the heat treatment is incorrect” or “the preponderance of potholes in modern roads”.
I feel the first two reasons are implausible but am open-minded regarding the third.
Suspension designs have changed as cars have become larger/heavier and ride/handling has been changed. I compared the front coil springs from a 1978 MGB and a 2008 Vauxhall Vectra. The shear stress in the latter was 1.5 times greater than that in the former, for the same load.
I wonder if any research/failure analysis has been done relating to this problem.
Martin Walters, Derby
Salt’s role in nuclear power
I have read several articles on nuclear power recently in PE.
There are many advantages to using nuclear reactor fuel that is dissolved in molten salt. Some of these advantages are:
• Such reactors can operate at atmospheric pressure so they don’t need an expensive pressure dome.
• Molten salt coolant can circulate by thermo-siphon, eliminating the absolute need for pumps.
• They have a negative feedback characteristic, in that the hotter the salt the less dense it is and the slower is the reaction, thus mitigating inherently against meltdown.
• They can use a much wider range of fuels, including the waste from existing reactors, so helping to solve the problem of what to do with that waste.
• They can use thorium, which is four times as abundant as uranium.
• The fuel can be 80% used up in the reactor instead of the 2% (typically) in a solid-fuelled reactor.
• The waste that is produced by small modular reactors needs to be safely stored for only a few hundred years as opposed to a few thousand years for the waste from solid-fuelled reactors.
In the 1960s and 70s, two designs of small modular reactor were built by Oak Ridge National Laboratory in the US. One of them, a 7.4MW reactor, ran without fault for the four-year experiment. The programme was closed by the US government because, at that time, it needed the big advantage of solid-fuelled reactors – a source of weapons-grade fissionable material.
With these advantages, why are we not developing this technology? The previous government funded studies and came out in favour of more research. I hope the existing government will not confine these reports to the drawer marked “don’t even think about it – it will cost money”.
The UK must not get left behind, yet again, in the development of a new technology that could save us from our otherwise catastrophic fate.
Jim Elsworth, Arusha, Tanzania
Compression solution
Regarding the Douglas Anderson split-cycle engine, one aspect is the additional compression work required to discharge the external compressor chamber (“My bright idea,” PE May). At the 5:1 compression ratio mentioned, compression work is more than doubled. This becomes a significant loss when this additional work
acts against the direction of engine rotation.
A second issue is that only a few degrees of crank angle are available for the induction phase at around 45° before top dead centre (TDC), creating difficulties for valve actuation.
One way of returning to in-cylinder compression work levels with split-cycle engines is to employ a switchable clearance volume between adjacent compressor and expander cylinders.
This can be achieved with a valved clearance volume that straddles both cylinders and an expander that lags the compressor by, say, 30°. Then, during compression, the clearance volume communicates with the compressor (inlet valve open). It is then sealed at compressor TDC for fuel mixing and initiation of combustion (30°) before the outlet valve opens at expander TDC.
The clearance volume outlet valve does require oil cooling, as it is exposed to peak combustion temperatures when open.
However, the split-cycle engine lends itself to the Atkinson cycle, where peak temperature would be lower for a given thermal efficiency owing to cooler compression and a low compression/high expansion regime.
Keith Hall, Maidenhead
Two-stroke rumbles on
Everyone interested in automotive powertrain is waiting for news from Zhongding Power in China, which in 2013 proclaimed that it would begin production in 2014 of two-stroke diesel engines for trucks in a new $200 million facility.
So Douglas Anderson is right to express an interest in two-stroke engines (“My bright idea,” PE May) even though there has been little development on the surface since the engines of Junkers before World War Two, Napier (Deltic), Rootes (T3) and Orbital Engine Company (gasoline engines) of Australia.
However, since the first announcement there has been little forthcoming in terms of finished hardware from the facility in China. China is a long way from the UK, but the implications of its attempts to build the EcoMotors Opoc opposed-piston two-stroke diesel engine at the rate of 3,000 a day cannot be taken lightly. One has to assume the Chinese know what they are doing, even if the pledged production date has shifted from 2014 to 2015.
Notwithstanding the efforts of EcoMotors of Michigan, there are others in the US beavering away at two-stroke engines. They include Achates Power of San Diego and Pinnacle Engines in San Carlos, both in California. Also, earlier this year, Cummins of Indiana announced it had partnered with Achates, which has been awarded a $14 million project to develop next-generation engines for tactical and combat vehicles. Achates claims this brings to six the number of concurrent customers whose contracts encompass five different engine applications: passenger vehicle, light commercial vehicle, heavy commercial vehicle, military, and marine/stationary power.
More than likely someone, somewhere will make a go of it. Whether the engines develop their promised performance in terms of reduced complexity and parts count, fuel economy and emissions remains to be seen. But two-stroke engines have not gone to sleep.
John Mortimer, Whaddon, Buckinghamshire
Shopfloor risk persists
Other readers have, rightly, written to condemn the lack of workplace health and safety measures in many parts of the world, as illustrated in PE May.
However, Mick Hibbert (Letters, PE July) is too quick to claim that such practices in UK establishments would be immediately stopped – I can only assume that he has never worked on the shopfloor, or that, if he has, he has had the good fortune to work in the most progressive companies.
The difference between the UK and developing countries is that such practices are universal in the latter, but they are far from uncommon in Britain. I have seen too many cases of arc-tan on exposed skin – and even, sadly, some
of arc-eye – to recollect them all here.
However, my most surprising account is that of an electrician who, in 2015, taught apprentices to test for live components by touching them with the back of their hand. He had his reasoning, I suppose. That way, if their hand spasmed with the current, at least they would pull it away from the wire rather than clamping their fist around it.
While I agree with the sentiment of Hibbert’s letter, and the UK’s attitude to workplace safety is second to none, we cannot afford to be complacent. Although in developing countries the cause of accidents is most often ignorance, in the UK it is more commonly sheer bloody-mindedness – and this attitude is still unacceptably common.
Aidan Reilly, Newcastle upon Tyne
Politician’s bad example
I have become inured to articles bemoaning our perceived status, but recently I saw the epitome of ignorance regarding an engineer’s place in modern society.
In the Western Mail on
17 July, Owen Smith, shadow secretary of state for Wales, wrote an article on trade unions and their place in democratic society. What really caught my eye was the list highlighting types of workers who donate to unions: “cleaners, engineers, care workers, and call-centre staff”. You can draw your own conclusion from this on where Smith places engineers in the professional hierarchy.
With this misunderstanding of our profession from such an influential individual, no wonder the public is none the wiser about this fundamental issue for all engineers.
Given this example, and others in the media, why would youngsters want to study for years to become an engineer when ‘similar professions’ are trained in months?
Gareth Halliwell, Marcross, Glamorgan
Consign spanners to the bin
The Observer on 19 July highlighted the lack of women in engineering, and its cartoon showed men and women in hard hats working on bits of machinery with spanners and other tools.
When will this outdated stereotype of engineering, and what professional engineers do, be consigned to the bin? Is it any wonder that so few women go into engineering when that is what they think it involves? How about a cartoon showing a nice modern office?
Patrick Barbour, Cardiff
Deniers put us in danger
The most recent four issues of PE give the impression that many engineers are in denial that production of carbon dioxide and methane are warming the planet.
I believe that statements in Soundbites (PE May), such as “The scientific evidence is overwhelming that there is no man-made climate change” and “We still cannot prove global warming is due to the emissions”, together with letters, have been damaging to the credibility of engineers and scientists worldwide.
I thank Ken Mitchell and Christos Dimitroulas (Letters, PE June and July) for reminding us how uneducated and unprofessional we appear.
Not publishing letters may seem like censorship, but there must be a level that is acceptable and sensible.
Here in Australia, the present government has become expert at closing down renewables and supporting the coal and fracking industry – to its own short-term political and financial advantage – by relying on the public uncertainty regarding climate change that this institution might be seen to confirm.
Permits for massive new open-cut coal reserves are still being granted, in my view at the cost of the best agricultural land and of the Barrier Reef, which will affect the world in future generations.
John Kubale, Tapitallee, New South Wales, Australia
Superjumbo delays
Regarding the article “Superjumbo ‘still the future’,” has anyone sought the views of passengers on being on one of these huge aircraft (News, PE July)?
When flying internationally on 500-seaters, it is bad enough sitting on the plane for an hour before take-off and taking a similar time on arrival to get through immigration. So how about almost doubling these times when flying on a superjumbo?
Terry Doyle, British Columbia, Canada