First photo of HS2 tunnel boring machines
ianvisits.co.uk
ianvisits.co.uk
With Crossrail (now Elizabeth Line) nearly finished under London, the Channel Tunnel, and now HS2 tunnels, the UK is exposing some of its workforce to some great tunnelling projects. The skill these workers must have aquired working on these large-scale tunnelling projects is impressive. The UK could even be developing a comparative advantage in tunnelling.
It doesn't solve the factors outlined at the start, but it's a side affect few discuss in public discourse when deciding to fund an infrastructure project like HS2. The positive externalities of SpaceX's work or of NASA's work are not limited to the end goal (the fact we fly something to space), it's also that now we have more people with better skills. This is something that the media doesn't focus on when big breakthroughs happen, whether privately- or publicly-funded, and I think that's a shame.
Asides from London, plenty of cities and big towns suffer from poor public transport. Getting from one side of town to another without a car should not be a struggle. Right now, I think this should be prioritised above city to city public transport links.
The problem in south west cheshire is many places not only aren't on a rail line, they aren't dense enough to keep a bus service running, even with subsidies
I agree, but HS2 will provide a huge benefit local and regional rail services rather than what most people assume: Faster travel in and out of London.
Frankly we need a lot more investment into light rail (trams etc.) and buses as well as HS2 and NPR.
Midlands Connect say HS2 will improve services to 73 stations, 53 of which aren't connected to HS2 [1]
It also introduces capacity gains for commuter lines into Euston (can't find the link for that)
I'd encourage everyone to read Rail Magazine's take on why we should build H2S [2]
1. https://www.midlandsconnect.uk/publications/hs2-released-cap...
2. https://www.railmagazine.com/research-hub/comment/comment-sp...
Furthermore, I would guess that the post coronavirus emphasis on remote work would make it less important, only time will tell.
At least https://www.bbc.co.uk/news/uk-16485263 talks about capacity a fair bit?
> Furthermore, I would guess that the post coronavirus emphasis on remote work would make it less important, only time will tell.
It's worthwhile remembering that number of people heading into cities has been rising year-over-year for a long time. Even if we see a 25% decrease in travel, any freed up rail capacity would likely just be taken up by people moving from road to rail. And with a larger decrease, while rail might drop away from being at capacity for a few years it's highly likely to increase again in future.
HS2 is almost all about easing local commuter routes.
HS2's PR has been, frankly, awful. Hell, its name has been its biggest failure.
If you read any of the published reports into HS2 then you'll see that capacity is the reason for the project.
If the line is coming past you then you have to put up with the noise from it and the building and land use change issues, but you don't get to actually use it as there won't be any stations for you. It's not possible to add stations mid-line as that would slow down the "high speed" aspect.
You can see this in the survey results where regions like the midlands have higher levels of opposition and those at the end of the lines:
https://yougov.co.uk/topics/transport/survey-results/daily/2...
>If the line is coming past you then you have to put up with the noise from it and the building and land use change issues, but you don't get to actually use it as there won't be any stations for you. It's not possible to add stations mid-line as that would slow down the "high speed" aspect.
Except that's actually nonsense.
Most of the benefit comes from moving the intercity trains off of the WCML meaning more local and regional trains can be run.
While those in Milton Keynes, Northmapton, Hemel Hempstead etc will love the extra services and space to London, and the increased services and reliability on the Rugby->Wolverhampton and Bimingham-Nottingham corridors will be great, those somewhere like Wendover won't see any benefit.
The large-scale projects need to srart every 10 years or so... the UK is in desperate need of non-car infrastructure if it wants to be carbon zero by 2050.
I think that criticism goes beyond the government. Parties of all colours have been far too London/South East-centric. I don't know of any infrastructure projects of reasonable size in Wales or the South West for instance.
Forgetting about places is a very effective way to keep generating forgotten about places.
One of Europe's largest construction sites is currently in Somerset - Hinkley Point C.
I live in this area and do these routes frequently and yes I'd love them to be more connected too.
But realistically, like almost everyone else in the country almost all my travel is to and from London, because that's where most things happen.
I can't help but feel that if the trains had dedicated business carriages with reliable internet access, nobody would be all that fussed to get to London 20 to 30 minutes quicker
edit:
I don't mean First Class. I mean something like an all tables carriage or even just a fold down tables that can easily accommodate a 17" laptop (even if not many people have them, the space is what I'm after)
The majority of the nation's key institutions are in London. How does improving an East-West axis improve access to them, or encourage them to move?
> I can't help but feel that if the trains had dedicated business carriages with reliable internet access
There are dedicated business carriages on London trains. The internet isn't fantastic but it's fine. But I'd rather not be on the train long enough to need it.
One is access for "everyone". Many don't need that.
The other is access to a large enough labour pool.
That said, the easiest way for government to use government departments for district development policies, is to simply move them.
E.g. this is where the Norwegian equivalent of Companies House plus assorted similar registries is located:
https://www.google.com/maps/place/Br%C3%B8nn%C3%B8ysundregis...
If you zoom out you'll notice there are no major cities nearby.The nearest major city - Trondheim - is ~6h-7h drive South. It's smaller than Nottingham.
Norway has "just" relocated government departments out of Oslo as an intentional policy for decades, and it takes effort but it generally works quite well.
Transport policy then follows depending on how this changes transport patterns, rather than lead.
As to if enough will move given any particular link, that is a hard question requiring complex studies and so cannot be answered.
If transport links are good between Liverpool, Manchester, Sheffield, Leeds and maybe Hull then you have a significant pool of people available to work in any of those locations, though bigger pool is going to be Manchester, Sheffield and Leeds. This could encourage a move as the transport links to London are already pretty good.
> There are dedicated business carriages on London trains. The internet isn't fantastic but it's fine.
You might not have seen my edit, I didn't mean First Class. The internet access was, until 2018 when I was on the trains regularly, pretty, pretty bad, even in First class. Constant drops, issues sending emails, etc ...
> But I'd rather not be on the train long enough to need it.
It's not about need is about using the time productively. I could be on the train to London and use the close to two hours to catch up on emails and do a lot of admin. Essentially for me, it was the difference between attending a customer meeting in London, then spending the next day catching up and just having a normal day the day after the meeting.
One of my guys refused to work on the train as he would get motion sickness, so clearly YMMV
I don't think people are that fussed. From QZ.com[0]:
"In the mornings, a train leaves London for Birmingham approximately every 15 minutes. The 7:23 am fast train leaves Euston and arrives at New Street station one hour and 22 minutes later, at 8:45 am—this would be shortened to 45 minutes with HS2.
The train is full of commuters and business travelers with a confusing range of opinions about HS2. Most point out that the journey from London to Birmingham is already quite fast. 'We have this train, so I question why we need it,' says Ben Brown, who commutes to Birmingham two to three times a week. 'It’s not as if the train that we’re in…is particularly slow,' echoes Damon Lacey, a human relations consultant from Portsmouth."
[0] https://qz.com/1803712/birmingham-shows-why-the-uks-hs2-plan...
It might be on HS2's route to the North, but it's certainly not on everyone's.
>Proponents of HS2 will point out ad nauseam that the point isn’t the journey time; it’s the increased capacity that a new railway will bring, allowing faster trains to shift on to their own track, and rendering the network more efficient. “We’ve been working off Victorian infrastructure on our national rail network and demand is increasing at an unprecedented scale, and we need more capacity,” explains Adam Tyndall, program director for transport at London First, a business advocacy group.
All things being equal, sure, but a high speed line is going to be more expensive, specially at the speeds required.
I'm not sure that any potential changes in working patterns given covid-19 will be taken into consideration but they should.
In any case, we'll no doubt fall into sunk cost fallacy territory soon and it will be £100Bn before this is done
I think the thing to understand here is that mixing speeds is awful for capacity. There are some fast trains now, and everything else has to be scheduled around them, which means they each eat up many slots, to clear the line a safe distance ahead. There's lots of demand for more slow trains, which can't be run.
If you built a new slow line, you would still have this problem. And the slow trains want to stop many places, so you can't build the line through open fields, and building through towns is really expensive.
So you build a new fast line. And then it may as well go a little faster than the existing fast trains. But this increment isn't the main point.
Or at least that's my understanding. I don't doubt the price will grow. I have also heard there may have been other not-quite-as-fast options, refurbishing a disused line instead?
It's actually not that much more expensive...
Fast train routes in the north will allow Manchester to become a replacement for most things people go to London for.
This is an unhelpfully abstract way to look at things. It doesn't matter what caused London to be the centre of the universe for UK society. What matters is that it currently is.
> Fast train routes in the north will allow Manchester to become a replacement for most things people go to London for.
The problem you're missing is that you don't need fast routes in the north, you'd need fast routes to the north, from everywhere, as you currently have with London, if you want to compete. You don't one new train line to Manchester, you need the thirteen or so routes in London has.
And then you also need a serious airport.
What is wrong with Manchester Airport ? It is the next busiest after Heathrow and Gatwick and already has two runways.
It's a joke. Cramped, dirty, unprofessional. I'm embarrassed when I ask colleagues to fly into it. The terminals are packed with bloody fruit machines. Massive smoking areas blocking all the entrances. Weird half-shut-down roads to the terminals. No decent dining or bar options. The security screening seems to be done in a dungeon about three stories underground. The terminals were cut in half in a strange way to accomodate changes to international I think so they're now a depressing maze and you have to go down steps into a basement to go from one side of the corridor to the other. Most of the terminals don't have a proper business lounge. I don't think there's a BA first-class lounge at all! The flag carrier has no first lounge!
It's not even very useful - few serious international routes. It doesn't have direct flights to essential business destinations like San Francisco. There's not even a flight to Washington DC anymore as far as I know!
It just isn't a serious international airport. I fly to all these incredible places around the world and come back into Manchester (via somewhere else as nothing is direct) and every time I think 'wow what a grimy, amateur operation - how embarrassing is it that this is all we can achieve'.
Not joking - I sometimes recommend colleagues fly into Heathrow and take the train so they don't get this first impression.
I guess maybe it's third in the UK, but it's like 1% of what Heathrow is.
Says it all, really! Even BA can't really be bothered with Manchester Airport.
But wouldn't you be entitled to use a First lounge if you were connecting via Heathrow in First?
BA doesn’t sell any first-class seats out of Manchester, and hence there’s no F lounge there?
And since Manchester is so terrible that you can hardly fly anywhere useful directly, lots of people are doing this.
And to the extent any investment is done in the Greater London region that it gets limited to better connecting the circle of towns on the outer rim of London.
A bit self serving, as I live in Croydon, but one of my pet examples is that Croydon, Guildford, Woking and towns in between are all within easy commuting distance by train and there's track between them, but there's either no direct trains or nothing suitable. Committing to a commuter time-table between groups of towns in that situation for enough years to allow companies to risk opting for these towns instead of the centre of London would do far more to alleviate London of commuter traffic than the same amount spent on line upgrades.
But all of the upgrades in London just draw in more traffic until things are just as bad again, but even more expensive to fix.
The idea is that hs2 would be new track that would free up slots on the existing network.
It always surprises me how many existing unused tunnels there already are under the Pennines. It's as if every generation is compelled to digg a train tunnel there as a rite of passage of something.
There is a congestion problem at Paddington in the West and with St Pancras/Euston in the north of London. So even if HS2 only gets to do its work at the London end before politicians cancel it then this part of the north-west London will be done, unblocking access to London for express trains. If they started in Birmingham and got cancelled they would not get this bit done.
There is also property speculation to consider, already far out places like Reading are now more accessible for London due to HS2, driving up house prices. A half completed HS2 that doesn't get to Birmingham will have a similar effect.
The only significant tunnelling is at the London end, and in the Cotswolds. It doesn't really make much sense to begin in the middle.
The approach to Birmingham will be almost entirely on the surface.
I can't find the link but it was recent - it was something along the lines of: for every pound spent on transport infrastructure in the UK, in the South East the investment returns more than 10x the return of other regions in the UK.
So the money is 'well spent' in the South East. It's a vicious spiral for the rest of the country.
"A faster connection between already well connected cities" HS2 is not.
Okay, well it is, but only as a side-effect.
HS2 is all about capacity; The West-Coast Mainline (WCML) is full.
Intercity trains have to compete for paths with regional and local trains (plus freight trains) which run slower and stop much more frequently.
Moving the intercity trains to their own dedicated track means they won't be slowed down by slower trains, it also means we can put more trains on the WCML.
This in turn means that, although HS2 is a North-South track, East-West trains will benefit. Hell, trains going in and out of Wales will benefit even though HS2 goes nowhere near Wales.
So why is HS2 high-speed if it's about capacity and not about speed? The simple answer is: Why not?
Building a high-speed track is actually not that much more expensive than building to the standards used on existing mainlines, but it does provide better long-term economic benefits.
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Now, a dedicated high-speed East-West line in the North is also well overdue. Northern Powerhouse Rail (NPR; aka HS3) is what's planned here but they can't finalise the plans until the detailed plans for Phase 2 of HS2 are themselves finalised.
Why? Because there's no use in building NPR if it won't properly join up (both literally and figuratively) with HS2 which is the most pressing infrastructure need.
This repeats an old pattern. The UK used to have a nationalised rail system with world-class R&D. The R&D was effectively given away when the system was privatised, and then the technology was bought in when it was needed later - from foreign companies which were now charging the UK for IP it had developed at home.
Even if that weren't true, the UK would be competing in a tiny space with even larger projects - like the Brenner Base Tunnel, which is currently burrowing through 55km of solid rock under the Alps.
The reality is there is very little real payback in terms of jobs and future opportunities - certainly much less than spending the money on world class broadband infrastructure and technology training.
The infuriating thing about HS2 is that it's basically just pork for party donors dressed up as a strategic and patriotic wonder - because the ruling class just can't deal with the fact that the 19th century is over.
Meanwhile the strategic areas the UK is actually a significant player in - including plenty of science and technology, and not a little engineering, but also the arts, finance, and law - are being starved of investment, opportunity, and effective management.
Skilling up people in the world of STEM, finance, arts are all as important, if not more so than tunnelling.
(Am Brit)
Previous world powers came to pre-eminence when less of the world was known and later world powers are nuclear and haven't really directly invaded, fought or attacked like the British did.
This map brings it home more than most https://i.redd.it/75nqzhfp42r21.png and it only covers a single instance for many of those countries, the British (English first, rest of UK later) and the French spent most of a millennia beating each other up when they had no one else to fight - I mean Churchill gave orders to shoot French military if necessary months before the end of WW2 (between VE and VJ day) during the Levant Crisis.
Just not (mostly) the British government (though the UK government also regularly has to step in to take over for failing operating companies...)
E.g. the Dutch, German, Italian, French, Quebec (via Keolis; a joint venture between French owned SNCF and a Quebec pension fund), Hong Kong governments all have significant ownership in UK rail franchises. Only a handful of franchises are run by purely privately owned operating companies.
Also, these are only the train operating companies, the rail and infrastructure itself is owned by Network Rail, which is state owned (and by the UK, not France!)
It's not like the French TGV/Thalys or the German ICE would run HS right into and out of the cities either.
Maybe in China and Japan, but hey, they are different.
https://www.railway-technology.com/features/feature-top-ten-...
Let's see how the Japanese do with their https://en.wikipedia.org/wiki/SCMaglev on the https://en.wikipedia.org/wiki/Ch%C5%AB%C5%8D_Shinkansen in a few years.
(In the Shanghai case it's practically laughable, because it's such a short journey the top speed is practically irrelevant: it spends half its time accelerating/braking)
https://weownit.org.uk/why-public-ownership/successful-examp...
(See https://publications.parliament.uk/pa/cm201719/cmselect/cmtr...)
Make of this trend what you will.
Fare increases have vastly slowed (versus inflation) since British Rail. https://books.google.co.uk/books?id=vAlCWxoV1NYC&lpg=PA277&p... shows average annual fare increase and RPI for the last 14 years of British Rail.
Over the last ten years of BR, fares increased 102% versus RPI of 62% (thus increasing 25% in real terms based on RPI; CPI didn't exist till the final five years of BR).
Over the past ten years, fares have increased 40% versus RPI of 31% (thus increasing 7% in real terms based on RPI, or 16% based on CPI).
Having said that, it's good that the work is happening; nothing is more corrosive to the long-term health of an industry than stopping all projects of a particular type. Some skills are embedded in the organisation rather than the individuals. This lost us much of our rolling stock industry, for example.
Obviously quality is tradeoff you need to be careful not to lose with cheap, but evidence is countries that don't speak English do this at much less cost and if anything better quality.
If you define benefits as ability for people to get from point a to point b, often, quickly and safely a lot of costs are not needed. Note in particular I artistic stations are not a benifet to me - some would disagree.
We know that by my definition Spain is able to build rail for much less cost.
Note that I picked consultants arbitrarily as something to pick on. Unions have been blamed. EPA has been blamed (I'm not sure what the UK equivalent is). Bribes have been blamed. There is plenty more.
There are always costs to projects (money spent on wages to UK taxpayers, money spent on imports, environmental damage, political damage from nimby campaigns, opportunity costs from people working on this project instead of another one - say crossrail 2)
There are always benefits to projects (money generated from more passengers, benefit of more space on existing lines, movement of freight from road to rail, movement of passengers from air to rail, benefits politically from spending money outside of London)
This is the same no matter what project, or who is funding it. Musk presumably includes "being able to go to Mars in his lifetime" as a benefit of starship, as that's his stated goal.
You could reduce the cost if you said "we don't need to go to mars", but that would remove the main benefit, and Musk isn't going to put as much as he does into it.
Clearly if you can reduce costs without reducing benefits it will increase the viability of a project, but reducing costs on its own does not necessarily increase the viability.
One is the frequency of service (HS2 Phase 1 is built for 18tph in each direction, and post Phase-2 higher passenger numbers than almost any other high-speed line),
Another is the cost of land (especially at the London end), as unlike many other international projects a dedicated line is being constructed all the way into the terminal (in part because existing lines don't have the capacity),
And finally the increased amount running in tunnel through the Chilterns versus the original proposal (as a result of legal challenges, themselves costly).
The price difference is much less extreme if you compare like-for-like (i.e., compare urban construction with other urban construction, rural with rural), for example.
Most comparisons are with "track only" schemes.
Judging by the cost and speed of tunneling projects of the last century or so, one would have to conclude that we are in fact somehow getting worse at it. Nearly across the world, tunneling is happening slower and at greater cost than previously.
Honest question: does this actually involve lots of UK workforce for the core jobs? I would think specialized crews move wherever these tunneling projects go. I know that already happens with specialized concrete pouring in high-rise building construction.
That makes sense for both companies, who want to work with experienced personnel, and workers, who do not want to move to lower-paying jobs if there isn’t any tunnel being bored in the UK for a while.
"from just inside the M25 to South Heath in Buckinghamshire"
South Heath is here https://www.google.com/maps/place/South+Heath/@51.7054459,-0...
We are going to tunnel through open country due to the politics and objections from land owners.
It is no surprise that the costs have risen.
Voters can decide if they want to pay an extra few billion pounds or to keep a little farm village.
And you know full well it's never the Lords and Lady's in this country at risk of their shooting grounds getting a train through it.
HS1 only has 4 significant tunnels, St Pancras to Rainham, the Thames Tunnel, Bluebell Hill, and the approach into Ashford International. Some of the major costs was moving some houses out of the way (by using pistons), and moving and removing bridges.
HS1 followed the Regents Canal out of London, the A2, and then M20 motorway through Kent.
Looks like HS2 isn't following any significant roads.
Nope. The tunnelling is uneconomic, but locals were able to ban the line from being built on the surface on the grounds that it's in a designated Area of Outstanding Natural Beauty (a status that is disproportionately applied in the rich south of the country).
The property tax for a house in 16 acres of pristine AONB in Buckinghamshire, worth £8m [0], is £3806 a year -- 0.04%
The property tax for a 2 bed terrace in Stoke-on-Trent for £65k [1] is £1107 -- 1.7%, 42 times higher.
[0] https://www.rightmove.co.uk/property-for-sale/property-62169...
[1] https://www.rightmove.co.uk/property-for-sale/property-80532...
Would be impossible to have an alignment suitable for 400km/h like that (and even if it were, difficult to build without disruption the M1 significantly).
Of course, why we'd want to pay $100B for a slower, more dangerous [1] way to travel around CA is beyond me (and I say that as someone who loves to travel by train).
However, people need practice and real projects to stay skilled. And if a country only has 1 major rail project every 30 years, you're not going to be able to maintain that workforce or national skill -- unless that workforce finds projects outside the country to work on. (Or attract people to that field. Maintenance alone is not very interesting to many people.) It becomes a very boom/bust talent pool that loses its sharpness because of lack of wood to chop.
I think advanced countries will find these kinds of skills (rail being just an example) attritting to developing countries like China, India where growth means that 10,000 rail-specific engineers have places to practice their skills on real projects that keep on coming. They stamp out an elevated rail bridge every month.
First you see the expertise moving to the private sector because government no longer engages in the building of infrastructure. Then even the private sector talent moves overseas to follow the projects. Even an org like Parsons almost cannot compete with this. And that's why you see rail projects going to such countries' companies as top bidders possessing the necessary expertise -- ready to go right now, rather than taking 1 year to even find the people.
Talent and ability follows the need (and money) for it.
These are usually custom made one off machines that don’t have much of a life span beyond each project.
That was on some level the whole point of the boring company Elon said it was crazy that these machines were discarded or sold for scrap.
That said since recovering them would be much easier than landing a rocket I don’t know if there is actually financial motivation to recover them.
When they are sold they are usually sold for their effective scrap weight (metal worth minus the cost of getting them offsite and breaking them down).
Yeah, I don't like that thinking.
I don’t imagine the paint for the Sistine Chapel ceiling cost much compared with the cost of painting it.
What I don't like is the thinking of people who rush for the sign off, and paycheck date.
These machines are also custom built for the diameter, soil type and probably a plethora of other variables so it’s unlikely that you could reuse them.
They are also not built to be recovered and reused from what I gather which complicates things further.
What's there to break? The cutters on the face of the TBM, and bearings would likely be replaced few times during boring. Aside from that, what's there to break? Hydraulics is sure to outlast even the longest boring.
Pumps, gearing, sealing, etc should all be easily replaceable.
These machines are constantly serviced and aren’t operated one minute past their life spans.
I really don’t think you understand how many hours these things operate for....
To put things into perspective machines have a single digit meters per hours top speed and not high single digits to boot, and if you are digging in rock you are looking at sub meter per hour figures.
If you have a source to contradict this I’ll be happy to read it but honestly every source from articles to documentaries pretty much paints the same picture these machines aren’t worth their weight in scrap once they are done with.
Then consider the Bertha problems in Seattle. Two year delay because they needed to dig a rescue pit to get at it after it broke down. Ask would you want to start a tunnel project with an 'used' TBM? Likely not.
https://commons.wikimedia.org/wiki/File:TBM_Cutter_Head_at_C...
People say this all the time but as someone who tends to follow quite a few tunnelling projects I can't recall one in recent memory. Typically TBMs are scrapped or returned to the manufacturer for refurbishment.
I think I remember reading back in the day that they buried/parked the machines near the center of the Channel where the French side and the English side met at the middle.
EDIT: Dogma replied on this as I was typing
"In December 1990, the French and British TBMs [tunnel boring machines] met in the middle and completed the Channel Service Tunnel bore. In all of the tunnels the French TBM was dismantled while the U.K. TBM was turned aside and buried"
I wonder if it was simply time management to have both sides meet at the middle or politics/symbolism. The former?
That tunnel is over a kilometre long, and they met in the middle of a hill!
Boring - see Civil Engineers
And with the current electoral situation, if merely being a Tory constituency got you a tunnel, HS2 would be in a tunnel from the M25 all the way to the outskirts of Birmingham.
Train lines don‘t take up much space and their impact can be mitigated with landscaping before we go to the expense of tunnels under fields
https://www.dailymail.co.uk/news/article-2084959/HS2-Tory-sh...
see japan: incredible surface transport options (that are also a sight to behold) and an incredible care for nature.
It'd be nice if PEOPLE could remain above-ground.
Only a million people live in Birmingham. That's £100k each.
Even in Kent now, after HS1 has been around for 10 years, you'll be hard pressed to find anyone that complains about it.
It's also added £300m to Kent's economy over the last decade, and the bulk of that has been in the last 5 years as traffic has ramped up.
[https://www.telegraph.co.uk/business/2017/09/13/hs1-provides...]
And being able to build hundreds of miles of high speed lines for single-digit billions of pounds/dollars tells you everything about wages, and compensation for home owners on the route.
(1) http://scotgov.maps.arcgis.com/apps/webappviewer/index.html?...
There's a bunch.
> Or are there good physics reasons why TBMs can't be much more efficient than they already are?
Mostly that tunnelling through unknown ground is risky (even if you're taken samples, you don't know what every meter is like!) so you don't want to move too fast, you're having to move vast quantities of spoil out, you need to keep the cutting blades cool (they're under immense pressure and friction so they get _hot_, and cooling is hard when you're in a confined tunnel) and we only have materials so hard (so you can't speed up the cutting head)…