Straight line distance from Cambridge to King's Cross is just shy of 50 miles. To do that in 20 mins, you're looking at an average speed of 150mph.......
No problem for my super train! You could even build it more or less along the existing alignment. The interesting bits would be around welwyn - I don't know if it's practical to interlock the slow lines with my super train as it makes a 30 second transition, but that would be my proposed solution (you could actually run it bidirectionally too to fit in with current timetable). Viaduct is no problem at all, just hang the coaster track off either side of the viaduct.
The gradients a rail-guided vehicle can manage are down to its speed. High speed lines can already be designed for much higher gradients than conventional rail. The G-forces would kick in at the vertical transitions between different gradients but this is really a second-order issue.
How is an elevated railway above narrow streets more helpful? Bear in mind the considerable additional structure needed to withstand the high lateral forces you envisage.
Also how will a mass transit vehicle have sufficient articulation to manage tight corners?
But any route through a built up area is going to be expensive no matter what route you choose.
Besides, the whole thing is unworkable as commuters are not going to put up with G-forces only usually experienced by fighter pilots.
Honestly, I haven't really thought in more than vague terms about what form the vehicle would take as I'd like to explore if this is even remotely possible in the first place (I'm not feeling optimistic so far but may as well run with it for a bit for fun) but as you point out it each coach will have to be considerably shorter than existing trains - and while articulated clearly there's no prospect of gangways etc - commuters will have to be strapped down. The elevated railway above narrow streets is useful because it doesn't incur much more cost than erecting very dense lamp posts - no need to buy property or demolish anything bigger than a letterbox.
Have you ever actually experienced 4G for more than a transitory?
Well, I always thought the DLR could do with a speedup, specially that run down to Bank...
I have done aerobatics when I was younger and fitter, that said even then 4G wouldn't have lasted long. But it wouldn't last long here either, only needed for the tightest turns. We can dial it down a bit if necessary and instead of flying around corners, use harsh accelleration and decelleration instead. 2G is perfectly ample in that case for the reason given in next quote.
If you are willing to pull several g, you don't need a 20 minute commute!
Even at 0.3g, in ten minutes you would be moving at ~1760m/s, or about 100km per minute.
Indeed when I did my calculations for that "GB Metro" maglev thing I bring up occasionally, I had to cut the acceleration of the maglev to that of the tube to make standing more practical.
Glad to see there's other great minds around!
