The Brennan self-balancing monorail [video](youtube.com)
youtube.com
The Brennan self-balancing monorail [video]
https://www.youtube.com/watch?v=kUYzuAJeg3M
60 comments
> With one rail, the models can't take power from the rails.
That immediately has me thinking about what sort of zany pantograph mechanism you'd need to get overhead power working. You might be able to get away with a really wide pantograph that has the right curve.
That immediately has me thinking about what sort of zany pantograph mechanism you'd need to get overhead power working. You might be able to get away with a really wide pantograph that has the right curve.
And here I thought that the gyro motorcycle that appeared a decade ago was a novel invention.
https://youtu.be/jICGl9jmulc
That second one is just gorgeous. That guy has every reason to look as smug as he does!
It really is gorgeous.
It's really a new build; the original had been abandoned and then hacked into being a no-gyro 3-wheeler. There are some parts from the original in the new one.
It's really a new build; the original had been abandoned and then hacked into being a no-gyro 3-wheeler. There are some parts from the original in the new one.
I once met a guy in Sault Ste. Marie that was rebuilding a Fox Moth from nothing more than the original manufacturers plate. Piece by piece, and every now and then someone would remember where a part of the original plane had ended up and then they'd go and collect it and make it like new again. Endless patience. He'd been at it for many years, his only wish was to either fly it or see it fly while he was still alive, the plane is now done and it is on display but it hasn't flown afaik.
I'm really happy someone took the trouble to rebuild this machine and to preserve it for the future, so much has been lost. Especially stuff made of steel.
Edit: here's the plane: https://bushplane.com/exhibits/bushplane-collection/dehavill...
When I last saw it in 2006 it was still mostly a frame and large collection of parts, it's amazing to see it in one piece, apparently they were going to fly it in 2019 but I can't find anything of that.
I'm really happy someone took the trouble to rebuild this machine and to preserve it for the future, so much has been lost. Especially stuff made of steel.
Edit: here's the plane: https://bushplane.com/exhibits/bushplane-collection/dehavill...
When I last saw it in 2006 it was still mostly a frame and large collection of parts, it's amazing to see it in one piece, apparently they were going to fly it in 2019 but I can't find anything of that.
Yeah, not a stretch to imagine someone could make a Star Wars Landspeeder version.
Well, that was the most annoying commercial break ever.
yt-dlp has sponsorblock integration, just saying
Yeah that was pretty jarring
Some things im curious about with this concept.
1) why not mount the gyro horizontally? 2) would the addition of a very large (say 10ft diameter) primary load bearing wheels (like a bicycle) assist with stability at speed 3) video mentions a need for gyros in each car, I wonder if such a system could only require a complicated active control system in the front (and maybe rear) car, and the rest could have simpler 'passive' gyro arrangements to assist in relative stability to the active controls? 4) could modern control systems materially improve upon this? For example, an all-electric drive for the intermediate gyros off a primary power unit is pretty trivial. 5) why wouldn't they want the flywheels higher up, like mounted over the roof? quicker reaction time and more force per rotation?
Thats all for now.
1) why not mount the gyro horizontally? 2) would the addition of a very large (say 10ft diameter) primary load bearing wheels (like a bicycle) assist with stability at speed 3) video mentions a need for gyros in each car, I wonder if such a system could only require a complicated active control system in the front (and maybe rear) car, and the rest could have simpler 'passive' gyro arrangements to assist in relative stability to the active controls? 4) could modern control systems materially improve upon this? For example, an all-electric drive for the intermediate gyros off a primary power unit is pretty trivial. 5) why wouldn't they want the flywheels higher up, like mounted over the roof? quicker reaction time and more force per rotation?
Thats all for now.
Wait, this isn't a Tom Scott video?
Didn’t he quit?
He didn't quit making videos entirely, he only "quit" releasing them to a set schedule.
... but hasn't released a single video since then, yet.
That's what I was expecting too.
Quite remarkable. Too ahead of its time? Wonder why it never got revisited
Seems like the requirement for gyroscopes in every car would be a deal breaker.
Could you make a gyro car? Akin to a locomotive? I don't exactly know how it would work but I was thinking we have locomotives so we don't need to put engines in every car. The thing I'm thinking about is that the gyro is kinda both a measurement device in a way, and also the system that actuates. Could these systems be separated, simplified, and scaled-down? I don't know, I'm not an engineer, just thinking aloud. :)
With the technology of the time I do not believe there is a solution.
Modern technology might be able to turn the car couplings into something that can actively manage their tilt relative to each other, thus allowing them to propagate the balance beyond a single gyro car, but there's a lot of PID-controller-type [1] math that would go into determining if this was even possible with real, physical objects trying to control things the size and mass of train cars in a train track environment. The computations are probably not that difficult in 2024 but trying to actually deliver the correct forces in a timely manner may be difficult if not impossible. There aren't always solutions, or practical solutions, to the PID equations in the real world.
Plus, I'm sitting here imagining the size of the electric motors we're trying to torque the cars against each other with and it's hard not to say that we're better off just having two tracks and putting those motors on the wheel themselves. (Which then collapses to having a locomotive setup like we have now.) In the "power/control/price" triangle we're basically forced to take the max on power and control, so these are going to be ferociously expensive if they can be built at all.
And there's some bad failure cases that I just don't know that you can mitigate. Having 30 minutes after power loss to evacuate passengers is generally going to be enough, but cargo can't be evacuated on that timeline. And that's not the only failure case. A seized gyro is going to be catastrophic and even a single one could take the whole train down, even with that PID control system (which is going to be a stretch even without also having to build in buffers for failed gyros).
The fact that a 2-track-train can just sit there for extended periods of time with no power is one of those advantages you don't even think about until you try to take it away.
Guy was a genius though. It's basically an analog computer that keeps itself upright that you can ride. The final design is amazing with its judo-esque approach to using physics against itself. But I don't think it can be scaled up much beyond "neat tourist attraction". I'd ride one as a tourist attraction, though.
[1]: https://en.wikipedia.org/wiki/Proportional%E2%80%93integral%...
Modern technology might be able to turn the car couplings into something that can actively manage their tilt relative to each other, thus allowing them to propagate the balance beyond a single gyro car, but there's a lot of PID-controller-type [1] math that would go into determining if this was even possible with real, physical objects trying to control things the size and mass of train cars in a train track environment. The computations are probably not that difficult in 2024 but trying to actually deliver the correct forces in a timely manner may be difficult if not impossible. There aren't always solutions, or practical solutions, to the PID equations in the real world.
Plus, I'm sitting here imagining the size of the electric motors we're trying to torque the cars against each other with and it's hard not to say that we're better off just having two tracks and putting those motors on the wheel themselves. (Which then collapses to having a locomotive setup like we have now.) In the "power/control/price" triangle we're basically forced to take the max on power and control, so these are going to be ferociously expensive if they can be built at all.
And there's some bad failure cases that I just don't know that you can mitigate. Having 30 minutes after power loss to evacuate passengers is generally going to be enough, but cargo can't be evacuated on that timeline. And that's not the only failure case. A seized gyro is going to be catastrophic and even a single one could take the whole train down, even with that PID control system (which is going to be a stretch even without also having to build in buffers for failed gyros).
The fact that a 2-track-train can just sit there for extended periods of time with no power is one of those advantages you don't even think about until you try to take it away.
Guy was a genius though. It's basically an analog computer that keeps itself upright that you can ride. The final design is amazing with its judo-esque approach to using physics against itself. But I don't think it can be scaled up much beyond "neat tourist attraction". I'd ride one as a tourist attraction, though.
[1]: https://en.wikipedia.org/wiki/Proportional%E2%80%93integral%...
Can always count on you for a fantastic reply Jeremy. Thank you.
Indeed, the more I think on it the more difficult the edge cases seem, I hadn't even gotten to the power out thing, although from thinking on the spinning cube conversations in this thread[1], I had thought about magnets as a failsafe mechanism, but at that point....
"The fact that a 2-track-train can just sit there for extended periods of time with no power is one of those advantages you don't even think about until you try to take it away." <- This heh.
[1] https://news.ycombinator.com/item?id=39336139
Indeed, the more I think on it the more difficult the edge cases seem, I hadn't even gotten to the power out thing, although from thinking on the spinning cube conversations in this thread[1], I had thought about magnets as a failsafe mechanism, but at that point....
"The fact that a 2-track-train can just sit there for extended periods of time with no power is one of those advantages you don't even think about until you try to take it away." <- This heh.
[1] https://news.ycombinator.com/item?id=39336139
Because you have to replicate the same complicated mechanism for all the cars. Moreover, if a gyro in one of cars malfunctions the whole train is at risk.
Another problem is that the system is reactive, meaning that there is a lot of shaking and balancing that is quite unacceptable - think about drinking a cup of tea in such a wobbly train even on straight lines, while on curves it's not staying horizontal by design.
Yet another problem is that it can't share the current infrastructure without major switch changes while sharing the infrastructure the other way around is impossible.
And in the end all of this effort for trying to fix a problem that doesn't really exist, at least not in Europe where most of the rail infrastructure was already built 100 years ago.
Another problem is that the system is reactive, meaning that there is a lot of shaking and balancing that is quite unacceptable - think about drinking a cup of tea in such a wobbly train even on straight lines, while on curves it's not staying horizontal by design.
Yet another problem is that it can't share the current infrastructure without major switch changes while sharing the infrastructure the other way around is impossible.
And in the end all of this effort for trying to fix a problem that doesn't really exist, at least not in Europe where most of the rail infrastructure was already built 100 years ago.
> ”while on curves it's not staying horizontal by design”
Worth noting that modern tilting trains do this quite successfully (on two rails!), in order to run faster on tracks with tight curves. By “leaning in” to curves, you make the ride more comfortable, not less.
Tilting trains are used extensively on the UK’s West Coast Main Line, for example.
Worth noting that modern tilting trains do this quite successfully (on two rails!), in order to run faster on tracks with tight curves. By “leaning in” to curves, you make the ride more comfortable, not less.
Tilting trains are used extensively on the UK’s West Coast Main Line, for example.
> By “leaning in” to curves, you make the ride more comfortable, not less.
That is the intention, but many people report discomfort due to the non-ideal adjustments, at least for the tilting trains in germany.
That is the intention, but many people report discomfort due to the non-ideal adjustments, at least for the tilting trains in germany.
I'm one of those people.
I commute 50 mins each way on a Pendolino in the UK (into and out of London) and find that if I'm doing work on my laptop, or responding to emails on my phone as the train tilts I feel uncomfortable and dizzy.
The "slow" Desiro trains that don't tilt take 2 minutes longer to get into London, because whilst their top speed is 15Mph lower they accelerate faster.
I commute 50 mins each way on a Pendolino in the UK (into and out of London) and find that if I'm doing work on my laptop, or responding to emails on my phone as the train tilts I feel uncomfortable and dizzy.
The "slow" Desiro trains that don't tilt take 2 minutes longer to get into London, because whilst their top speed is 15Mph lower they accelerate faster.
Do you still feel uncomfortable if you cannot see outside the train at all (i.e. not even in peripheral vision)? My understanding was that the effect was caused by the scenery outside the window moving in a way that's incommensurate with what your sense of balance is telling you.
It's connected to how our attention works. Attention is very much tied to vision and, for instance, if you are rotating around your central axis (like a Sufi) and can manage not to focus visually on anything around you and do some "proprioceptive attention adjustments", you can keep spinning for quite a long time w/o getting dizzy. Of course you'll have to slow down slowly rather than just abruptly stop the rotation.
It tends to be better if I look out the window, it's the looking at a screen and my inner ear sensing the movement that mucks me up I think.
Interestingly, I don't get motion sickness in VR, which is the opposite problem (movement visually, none in reality).
Interestingly, I don't get motion sickness in VR, which is the opposite problem (movement visually, none in reality).
Ideal adjustments (full compensation) are more uncomfortable.
Thought to be so, because there's a mismatch been visual and inner ear inputs. That is: you can see you're going around a corner, but you don't feel it. Resulting in motion sickness. Since all people have different tolerances of motion sickness, it's impossible to have a "correct" amount.
Almost all systems compromise between zero and full compensation, but passenger comfort is just one of many factors, and not the most significant. The discomfort on German tilting trains is probably because they are too close to "ideal".
Thought to be so, because there's a mismatch been visual and inner ear inputs. That is: you can see you're going around a corner, but you don't feel it. Resulting in motion sickness. Since all people have different tolerances of motion sickness, it's impossible to have a "correct" amount.
Almost all systems compromise between zero and full compensation, but passenger comfort is just one of many factors, and not the most significant. The discomfort on German tilting trains is probably because they are too close to "ideal".
Ideal (in the sense of fully compensated) is worse, but ideal in the sense of at the right time, with smooth interior motion, is much better. A "perfect" tilting train shouldn't feel much different than superelevation to the same level, but it does.
One of the issues with the German tilting trains is that they try to compensate up to 8° without track knowledge (BR 612) thus the first carriage (the one after that less so) swinging abruptly to compensate when entering or exiting a curve. Not sure how the class 390s solve that problem.
One of the issues with the German tilting trains is that they try to compensate up to 8° without track knowledge (BR 612) thus the first carriage (the one after that less so) swinging abruptly to compensate when entering or exiting a curve. Not sure how the class 390s solve that problem.
So you're saying the rate of change of compensation (or "jerk rate" when entering and exiting a curve, as people enjoy calling it) is worse on tilting trains?
I would love to see some data - I assumed this was a solved problem, but I wouldn't be too surprised if the tolerances were revised to fit the problem.
I forgot to mention the 'interesting' part of this problem: that the effects are measured cumulatively. That is, against passenger journey length. Drivers and other staff are not considered as far as I know!
I would love to see some data - I assumed this was a solved problem, but I wouldn't be too surprised if the tolerances were revised to fit the problem.
I forgot to mention the 'interesting' part of this problem: that the effects are measured cumulatively. That is, against passenger journey length. Drivers and other staff are not considered as far as I know!
And there's zero redundancy. If 1 of those piston seals or valves fail, the whole train is at risk for catastrophic failure.
Clever engineering without a necessary, defensible, competitive business advantage usually becomes either a hobby or an art project.
Clever engineering without a necessary, defensible, competitive business advantage usually becomes either a hobby or an art project.
And if one rail has a gap or defect.
Yes, the part of the video that said this would work on existing infrastructure is entirely wrong.
It could be interesting with it's own infrastructure, though my first thought is that it might be better suited to tunnels, being able to maximize use of the tunnel profile.
It could be interesting with it's own infrastructure, though my first thought is that it might be better suited to tunnels, being able to maximize use of the tunnel profile.
The double flange wheel wouldn't work with existing rail switches.
What's the benefit?
In the video it explains it only uses half the track material since it only has one track instead of two. It can also go faster since it leans into corners and doesn't derail like two track trains.
> leans into corners
Modern trains do that too. https://en.wikipedia.org/wiki/Advanced_Passenger_Train eventually led to https://en.wikipedia.org/wiki/Avelia_Liberty, which is being deployed for Acela in the US.
Modern trains do that too. https://en.wikipedia.org/wiki/Advanced_Passenger_Train eventually led to https://en.wikipedia.org/wiki/Avelia_Liberty, which is being deployed for Acela in the US.
It also required the complex gyro for each car, not just the engine, which is why the video states ultimately it was killed. I'm not sure the situation has changed with that.
No. Watch the video.
Do e-scooters and the like self-balance in this way?
It would be cool to have self-balancing rollerblades.
It would be cool to have self-balancing rollerblades.
Anything with rolling wheels will have some tendency to continue straight once the wheels are spinning, but they don't help to stabilize in corners. On small wheels, the effect is very small in any case, especially since the scooter and its batteries are relatively quite heavy.
The gyroscopic effect of wheels has a minimal impact on the tendency of things like bicycles to remain balanced; the majority of the effect comes from the rake of the front wheel (i.e. that the point where it touches the ground is ahead of the pivot point of the front post).
That gyroscopic effect of the wheel works well when the whole device is wheel (think hoop rolling), but when you start adding weight that's not spinning (like someone riding a scooter), the effect falls off.
Edit: it seems that neither the gyroscopic effect nor rake are sufficient to explain bicycles' self-stability: https://en.wikipedia.org/wiki/Two-mass-skate_bicycle
That gyroscopic effect of the wheel works well when the whole device is wheel (think hoop rolling), but when you start adding weight that's not spinning (like someone riding a scooter), the effect falls off.
Edit: it seems that neither the gyroscopic effect nor rake are sufficient to explain bicycles' self-stability: https://en.wikipedia.org/wiki/Two-mass-skate_bicycle
« the point where it touches the ground is ahead of the pivot point of the front post »
The other way around -- the contact patch of the tire is behind the projection of the head tube onto the ground.
I love that there are actually three different stability mechanisms. I wonder if there are others!
The other way around -- the contact patch of the tire is behind the projection of the head tube onto the ground.
I love that there are actually three different stability mechanisms. I wonder if there are others!
see https://2swiftboards.com/, which is an electric scooter with no handlebars.
At low speeds, a high-friction headset adds stability by damping the tendency to turn and flop.
At higher speeds, the reverse fork rake and spinning wheels provide stability.
This is my read on it, as someone that uses a 2Swift as a commuter vehicle, but the physics-based explanation may differ.
At low speeds, a high-friction headset adds stability by damping the tendency to turn and flop.
At higher speeds, the reverse fork rake and spinning wheels provide stability.
This is my read on it, as someone that uses a 2Swift as a commuter vehicle, but the physics-based explanation may differ.
Incredible. Sometimes it seems like we were more advanced in the past.
This is occasionally true, but that is very infrequent.
The example I like to cite is swords. Despite swords playing no role in modern combat, modern swords (the real ones, not knockoff/costume swords) are of a higher quality, fit, and finish, than anything a knight or samurai would have been able to obtain. While being dramatically cheaper, in the sense that someone would have many fewer hours to work to obtain one.
There are counterexamples of products which would have been cheaper at a given quality in the past, or readily available when they're difficult to obtain in the present. But once you rule out things made with ivory and whalebone, these are scarce indeed.
The example I like to cite is swords. Despite swords playing no role in modern combat, modern swords (the real ones, not knockoff/costume swords) are of a higher quality, fit, and finish, than anything a knight or samurai would have been able to obtain. While being dramatically cheaper, in the sense that someone would have many fewer hours to work to obtain one.
There are counterexamples of products which would have been cheaper at a given quality in the past, or readily available when they're difficult to obtain in the present. But once you rule out things made with ivory and whalebone, these are scarce indeed.
It reminds me a bit of TRIZ thinking https://en.wikipedia.org/wiki/TRIZ. It's not that we were "more advanced", it's just that Brennan had a clear-headed approach to use mix of elements (gyroscopes, differential/asymmetry, pneumatics)
yeah, these old mechanical control devices seem like a real life 'steam punk'.
Where do you get that from? We still come up with crazy designs all the time (that are rejected in favor of robustness, compatibility, etc.)
The crazy designs from 100+ years ago though were more impressive though because of the limitations imposed from not yet having electronics, computers, software.... They had to be incredibly clever mechanically. I too was impressed from the video the way the guy iterated in clever ways to address issues that came up. And, as I say, iterated within a relatively narrow realm of options.
Ads a counter-example, I watch hobbyists on YouTube these days that build and fly various R/C contraptions that would not have been do-able in the days of small gasoline engines and huge, heavy radio receivers. It's like today you can take a sheet of foam from Lowes, strap on some high efficiency brushless DC motors, double-sticky-tape on an ESC, receiver and be flying that sheet of foam by the afternoon. Too easy.
Ads a counter-example, I watch hobbyists on YouTube these days that build and fly various R/C contraptions that would not have been do-able in the days of small gasoline engines and huge, heavy radio receivers. It's like today you can take a sheet of foam from Lowes, strap on some high efficiency brushless DC motors, double-sticky-tape on an ESC, receiver and be flying that sheet of foam by the afternoon. Too easy.
There must be enough people that were similarly amazed and/or fascinated to vote it to front page. Maybe my phrasing was not to your liking.
I'm sorry you've lost your sense of wonder.
I'm sorry you've lost your sense of wonder.
Are you kidding? I freaking love this invention. I just don't think it's evidence for some kind of civilizational decline.
"civilizational decline"
OH. Didn't realize that is how you took it. That was not my intent.
What I really meant, is the old style 'mechanical controls' do seem very inventive compared to today, because todays world is so much 'electronic controls'. Some of these solutions from 100+ years ago, seem revolutionary now, because we have forgotten that 'method' of solutions.
I am not sure current engineers could come up with some of the same "old-fashioned" solutions that worked 100 years ago. Maybe because we are so advanced now, that it is almost like "that knowledge is lost"?
Could go on, it is a worry I do have about actual collapse. Lets say we lost power grid or supply chain disruption. It would be huge task for current engineers to figure out how to re-build things again, with old technology.
OH. Didn't realize that is how you took it. That was not my intent.
What I really meant, is the old style 'mechanical controls' do seem very inventive compared to today, because todays world is so much 'electronic controls'. Some of these solutions from 100+ years ago, seem revolutionary now, because we have forgotten that 'method' of solutions.
I am not sure current engineers could come up with some of the same "old-fashioned" solutions that worked 100 years ago. Maybe because we are so advanced now, that it is almost like "that knowledge is lost"?
Could go on, it is a worry I do have about actual collapse. Lets say we lost power grid or supply chain disruption. It would be huge task for current engineers to figure out how to re-build things again, with old technology.
Ah, I see what you're saying. I'm... not actually sure, though. There's a huge amount of recorded work to draw from, and just a larger number of people working on things. It might be that we're actually better off in our collective ability to develop mechanical solutions even if the median talent in it among engineers is lower.
I wonder if gyro drift would eventually cause problems?
What happens on a power failure?
The video says the gyros would continue spinning for 30 minutes (inertia) in the event of power failure. Enough time to get the kickstand down I guess.
With one rail, the models can't take power from the rails. They run on AA batteries.
There's also a drivable 2-wheeled gyro-balanced car from the late 1960s.[2]
These things work, but wobble too much. With active control, though...
[1] https://www.youtube.com/watch?v=ifroNPpK9jQ&list=PLE006F2D73...
[2] https://www.youtube.com/watch?v=TTCVn4EByfI