If any of y’all like this, I am building an open source 3D printed off road robot with in wheel motors and transmissions, and I post regular updates on the project on YouTube. The transmission is currently an 11:1 two stage planetary gearbox that is almost entirely 3D printed (aside from some bearings, screws, and metal pins). I recently drove 2.2 kilometers with it but I’m shooting for 20km and hopefully 50+kms between gearbox services. Can be made on a $1k printer and it’s all CC0 open source. Code is python on Raspberry Pi.
I liked that part of the DARPA-demo the best for sure. It seems obvious that vehicle suspension should be dynamically controlled by software anticipating the terrain. (Maybe cars already have this technology to some extent? I'm not sure.) What's the soft tech in your robot?
There’s been at least two attempts at active suspension I’m aware of. One is quite old. It came up in discussion on HN recently. Back shortly with a link.
> Maybe cars already have this technology to some extent?
It was banned in F1, that combined with the skirts for downforce meant for insane low ground clearances with grip off the scales. You could see cornering speeds going up seemingly without end.
some F1 cars had it briefly in the 1970s and it was outlawed. Cars would lean into the turns, nose up when braking, nose down when acclerating. crazy stuff.
Hello! I’m not sure I understand the phrase “soft tech”, but Rover uses some large springs for suspension and has big foam tires. I could build active suspension but it dramatically increases the cost and complexity of the robot, which goes counter to my goals. Some low cost active suspension would be helpful though! Right now I’m just focused on keeping the thing reliable. :)
I myself have some interest in the software side of this. I see the robot is remote controlled - but I think a large degree of autonomy would be required for a 50Km trip.
The current self driving technology relies on a trunk full of Nvidia cards sucking data in from a few dozen cameras, lidars or radars all working to create a coherent world view, the whole system drawing hundreds of watts of power.
I wonder if it's possible to capture 90% of the performance of that system with simple hardware that can fit such minimal hardware and other applications where failure is an option and has limited consequences.
A thing I'm thinking about lately are lightweight, electric self driving bikes (or more exactly, trikes) running on existing, dedicated bike infrastructure, augmented with some embedded instrumentation. As long as the speed does not exceed 15Km/h and they are guaranteed to never run a red light or run over any object crossing the path, they could be as safe as a human driven bikes.
Why would you want a self-driving bicycle? It’s not like you can relax and read a book during the ride, and it’s not very autonomous either (unless it can stand upright without moving).
Is the windscreen the defining feature of a car? It can be replaced with a plastic, zipper tarpaulin. I see the distinction more as a weight-power-danger thing.
That's not a bicycle, it's a tricycle. I guess you've solved the problem of balancing but I don't think many bicyclists would be happy with your design.
Well, I did say trike in the original post above. I think the relationship with the bicyclist community depends on the safety and weight/speed of the vehicle and how well it suits their own needs. Trikes and electric trikes are allowed on bicycle tracks depending on jurisdiction, an example upper ceiling of power is 250W.
Yes autonomy is super important for a robot like this! I build rover as a platform for autonomy research, as smaller robots I’ve built in the past didn’t have enough room for a high powered compute and an array of sensors.
I’m particularly interested in camera only navigation, localization, and obstacle avoidance, and I hope to get an NVIDIA Xavier board and multiple cameras to use as the sensing system. I’m trying to get myself in a position where I finally have to learn machine learning, and Rover is the project for that!
Thanks! I use a modified Monoprice Maker Select V2 and a modified TEVO Black Widow (which I don’t recommend due to assembly effort). The CR-10 and especially the 400mm version is what I recommend for building Rover!
Wow. Another awesome open source project that I will hopefully be replicating. What's the remote control that you're using? I see flutter support in your code and am unfamiliar with flutter.
Yeah, I’m using Flutter. I’m the person who made Flutter so I have a lot of them. I used to have bluetooth control from iPhone but I wanted a physical interface. Any remote is trivially easy to add though - the remote is a standalone python program that sends GRPC commands to the motors. I recently got a PS4 remote and may add support for that!
One advantage of electric transmission for military vehicle is that you don't have a single driveshaft to fail on you rendering you immobile, nor clutches, nor a chance that a single broken wheel will jam the rest of powertrain.
The last point is the biggest advantage of many wheels vehicles over tracks. A detracked tank is a sitting duck, but an 8x8 without a single wheel will happily run away after taking damage
These are probably brush-less motors, so in theory, they shouldn't pose any specific challenges in that scenario, as there are no exposed conductors, only sets of insulated coils/windings and permanent magnets that would end up being immersed in a river.
Technology is naturally more augmentation than automation. This is closer to the future of driving than the self-driving AI solutions. Our senses will be aided and some tasks out-sourced. This is already happening, has always been happening, e.g. anti-lock braking system or proximity detection with auditory feedback.
How are self-driving vehicles NOT an augmentation? We are not talking about self-living bodies here. Self driving vehicles augment our ability to transport ourselves and our stuff without the use of a part of our mental system. It's like walking on the automatic pilot, like in your home, except faster.
Yeah, it is certainly not a clear cut distinction. You know, I initially listed automatic transmission as an example of augmentation. So it goes both ways too. Anyway, they highlight different aspects and I find the notion elucifying.
What is so special? It looks like an advertisement for DARPA and military. Other firms around the world do that too : https://www.swincar.net/ (oh! And not to kill people)
Not only the vehicle would probably be lighter (batteries vs motor, gearboxes, etc) but it would have 2.81 more power, so it would probably vastly overperform current vehicles?
Did not realize how heavy modern batteries still were.
Tesla Model 3 batteries weight 480kg for 80.5kWh, density of 167Wh/kg.
The DARPA vehicle running for 1h at full power would require a whopping 2400kg of batteries! To give a comparison point, according to Wikipedia, 2400kg is the weight of an Humvee.
I guess it'll still take a little while until the DARPA concept becomes an actual vehicle...
Nothing that stops them from putting in a small turbine to generate electricity. If memory serves me right, this is what some modern tanks do, like the Abraham. Add in a somewhat small (compared to battery powered only) battery pack and you can use that to power the vehicle when idling.
Abrahams use mechanical transmission from the turbines. Some ships and trains use diesel electric drivetrains or even turbine electric but its not for weight or efficiency but controllability. My understanding hybrid electric drivetrains are around 80% efficiency, while normal mechanical drivetrains are in the mid 90's. This is why nearly all hybrid cars switch over to normal mechnical drive typically at highway speeds as it more much efficient, while in the city in stop and go the electric drive train beats it due to regeneration and stop light idling.
That has not been my experience. Diesel generator-motor sets are much heavier than a diesel engine with mechanical transmission and are less efficient. That does not even take into account a buffer battery weight which you pretty much need for power draw spikes and regenerative braking.
Just look at say a Cummins ISB with Allison transmission at 300hp, that's around 225 kilowatts. That combo weighs around 1500 lbs, maybe closer to 2000 with running gear if your comparing to hub motors. A bare frame generator putting out 200+ kw its going to be well over 4000lbs plus whatever hub motors and motor controllers and power systems and batteries weigh.
You can go smaller on the generator and make it up on the battery which means more weight, but even a 100kw generator is going to be around 3000lbs and you won't be able to utilize full power for long periods (long grades).
Perhaps some advanced generator might be lighter, but it essentially the engine with the same size and weight generator attached to it as needed for motors of equivalent power output. Mechanical transmission on the other hand are pretty light comparatively and have much less losses than the mechanical-electrical-mechanical double conversion.
This isn't a fair comparison, because you're considering a generator that's intended for stationary use.
Of course this is going to be heavier than one intended for a vehicle, because the weight isn't a consideration, and lighter is more expensive (more precise, higher-quality materials).
What you'd want to be looking at is train powertrains, which are uniformly diesel-electric, because this is the most efficient power configuration.
Or the Chevy Volt, for a smaller example which happens to run on gasoline.
Trains have 4+ driven axles mounted on bogies that swivel under the chassis. All wheels must be driven (steel on steel doesn't give you much traction) Diesel electric is used in trains because any mechanic transmission that can do that job would be a Rube Goldberg contraption.
A mechanical gearbox is more efficient way of transmitting power because if you've sized things right cruising RPM will be direct drive (no loss from gear friction).
Can you point me to a light weight 100kw or 200kw genset that is under 1500 lbs? Bottom line even if a 200kw genset plus motors and controllers was the same weight as a 200kw engine hooked to a transmission, it would have lower efficiency due to conversion losses unless we get practical superconductors.
Trains do not use diesel electric drives trains for efficiency or weight, the need precise traction control to prevent the steel wheels from slipping on the tracks to get moving, the electric drive train gives them that. The actual efficiency is lower than a mechanical transmission once up to speed due to double conversion losses. Modern mechanical transmissions are actually very efficient with very low losses.
The Chevy volt also bypasses the electric system at highways speeds due to the inefficiency of converting mechanical energy to electrical and back to mechanical as most (all?) production hybrids. The Gen 2 Volt actually more aggressively move to mechanical drive at lower speed as it was found to be more efficient. The Volt is also heavier then the Cruze even though they share the same platform.
Gasoline hybrids like the volt also typically rely on the Atkinson cycle to get better highway efficiency at the expense of torque which is made up for by the electric drivetrain. Diesels are even more efficient and have plenty of torque but also heavier due to a more robust design, this is why they are much less popular in hybrid configurations except in specialized applications like city buses with extreme urban start stop usage.
The Humvee is a 1970s design and uses an engine that was designed to prioritize fuel economy. Any modern power-train (and many not so modern ones) should vastly outperform a Humvee.
2nd thought: too bad it's gonna be military use first. I've often heard the argument being made that military applications (and even war itself) somehow drive innovation.
While that may be true to an extent, it always rang hollow to me as an argument. Why should civil life always just get the "crumbs" of science and engineering? Why not turn it around, spend most of the research money and brain time on things that benefit everyone (in the US, and worldwide) and then see which of those technologies can be repurposed for the military, not the other way around?
DARPA alone has a bigger budget than NASA, and I just googled "us military research budget" and the numbers for all the arms of the US military are quite staggering, really.
Interesting read so far. The fish farming story is a nice example. For further analysis around the same topic, https://equilibriabook.com is a great read.
>8. Arms races. Large countries can spend anywhere from 5% to 30% of their budget on defense. In the absence of war – a condition which has mostly held for the past fifty years – all this does is sap money away from infrastructure, health, education, or economic growth. But any country that fails to spend enough money on defense risks being invaded by a neighboring country that did. Therefore, almost all countries try to spend some money on defense.
>From a god’s-eye-view, the best solution is world peace and no country having an army at all. From within the system, no country can unilaterally enforce that, so their best option is to keep on throwing their money into missiles that lie in silos unused.
Funnily enough, we can come full circle and say that many developed nations can survive these days with very little military spending just because America's massive military is enough of a deterrent.
We have been warring before the dawn of civilization. I think it used to play a role in territorial resource usage/rights, evolutionary selection, population control and asserting your own set of morals.
I wish we all get over war, but realistically, as long as we differentiate between "good" and "bad", there will always be some source of enmity to start wars..
In almost all wars, the "bad" is that one group wants to take something away from another group. Sometimes that thing is their freedom, but even in those cases, there is usually an underlying material issue.
In almost all wars, the "bad" is the group that lost the war. And when it cannot be decided or doesn't matter anymore, those who control the discourse decide who is/was "good".
Taking something away is not good or bad per se. Sometimes both sides see the other part "taking something away" from them (see any rebellion vs central power conflict).
Actually, that's not really the case: warring started at the dawn of civilization. There aren't many clear cases of large scale destruction of human life in prehistoric times. The proliferation of war only happened as sedentism gained popularity. Sedentism is the start of civilization. It also creates economic stratification, which is probably the number one reason for war across nations and inside nations.
That sounds like a bit of a tautology given that humanity kept to relatively small bands at that time from logistical constraints.
Also amusingly technologically mutually assured destruction may have started with /fire/ and contributed back in ancient forest Africa. Essentially if there was a rival band to risky to fight and you have mastery of fire setting via a firebreak a contained wildfire would rid a threat and give remaining territory minus what was burnt into immediate uselessness.
> Why not turn it around, spend most of the research money and brain time on things that benefit everyone (in the US, and worldwide)
I think this is a quirk of the US political system where military spending is the only public spending that is acceptable to both parties in the duopoly. Hence the only stable source of public funding for research is probably in the military sector.
I'd argue opportunity cost from lack of innovation in medecine and e.g. car safety/car replacements kills more than US military involvements... Car deaths alone are >37K in 2016 in the US alone:
There are lots of reasons to spend money on military technology, but absolute reduction in deaths by U.S. citizens is not a compelling one — there are just too many civilians who die in preventable ways as compared to military deaths.
I think it’s kind of a silly comparison, tbh. I’d like to see us spend more money on both civilian and military research. I suspect that the military spends plenty of money on shit that is less impactful in the long term than research, and military research also often advances civilian technology.
I believe the argument is that the research is supposed to lead to a lower chance of the US or allied citizen deaths by preventing advisaries from attacking. We hope that the expensive nuclear capabilities, for example, are never used. How do we measure the potential loss if we had no such capability?
At least 50,000,000 were killed in WW2 alone. In WW1 around 16,000,000 were killed. That is over 65,000,000 people killed counting only the two biggest conflicts of the 20th century. If another global conflict broke out, the death count could easily be 100,000,000. If the money the US spends on military keeps a world war from happening in the 21st century it will be money well spent.
It's really phenomenal to think about how many people died in WW2. It's literally difficult to even imagine. And your numbers there are a bit off. Estimates tend to start more around 70 million. And I think that's leading to you low ball the potential death toll in future wars. In 1945 the entire world's population was around 2.4 billion. Nearly 3% of the world was killed or died as a result of WW2. The world's population today is 7.6 billion. A war of the same effect would have an expected death toll of around 222 million people. And that's probably substantially lowballing it as we have far greater ways of killing each other now a days, even if we take nukes out of the picture.
Even just back to those 70 million, let's say 73 million as that's where Wiki starts and it seems reasonable. Just imagine that. That's a 9/11 scale of death every single day for 24,366 days. Or a 9/11 scale event every single day for 67 years. That's again difficult to even imagine. And all of that death, with a population 1/3rd of ours today, was compressed into 6 years. Such lessons should never be forgotten, but in a way it's difficult to learn from such things when we really cannot even imagine death and destruction on this scale now a days.
I think you're right but I'd phrase it as the military typically has very specific needs and constraints which helps design and sometimes those needs overlap with civilian life.
That's true. Military spending is the only kind of industrial strategy the US is willing to implement without one of the parties immediately blocking the effort. Pretty sad but it's the state of things.
Military research spending is also 'easy' to administer and simpler - have a bunch of siloed off portions investigating any remotely viable approach. Even investigating something that we later know is unfeasible like gyrorocket weapons or walking trucks it is known what it would get and that they have potential to be useful. Tore or less regular generations. Generally what makes it through is accurate, faster, or longer ranged but fundamentally very similar even if it is 'just' laser guided missiles from drones instead of blind dropped fletchettes from biplanes.
Civilian research is 'harder' in that the advances are less qualitative and more abstract. Is researching amphibian biology going to somehow improve medicine? (Axotls may be anywhere from a dead-end to bringing regeneration). The 'boring' solutions are already there and being worked on. Furthermore there rationalizing secrecy becomes far harder and anything that sounds stupid can be attacked for political points regardless of the underlying reality.
The 'treadmill for shrimp' for instance is attacked as an example of waste when it is the exact opposite - using an innovative way to cut expenses as part of examining the impact of water quality on the health and livelihood of species that are an economic lifeblood in many regions.
I try to think in terms of that which is not seen. What are the technologies that would be developed by the same minds, were they not directed toward military projects?
The same is true of the finance sector. How many brilliant minds are toiling away to generate alpha for the investors, when they could be unleashed in other more productive sectors of society?
It's invalid to claim that "X beneficial technology wouldn't have been invented if not for Y war or Z program." Rather, military spending might shift when a technology was demanded by the market. And again, it diverts brilliant minds to one thing, when they could have done something else (that which is not seen) for society.
The other angle is yes, this is awesome tech! But it could not compete in the market, since it is entirely impractical. It only exists because it serves the demands of a program manager at $AGENCY with tax money to spend.
Wow, I can't believe your comment is what we're discussing. I've seen some version of this on the Internet for 30 years now. I must have answered it a dozen times.
Can we turn this into an Internet FAQ? Basically, it wastes everyone's time. If everyone here agreed with you, would it change anything?
If you think the military spends a lot on research, you should see what they spend on non-research.
Yeah, that most probably reflects my bias. Being in academia myself, I have a hard time thinking of good reasons to work for the military vs virtually any civil application.
Also, I don't have 30 years of internet experience, so maybe it'll just take some more time for me to get tired of discussing this :)
Money spent here is the most abstract as it doesn't define a problem before it tries to solve it but rather looks for things we don't understand yet.
Military research:
The point of this research is maintaining power which means researching whatever might give you the upper hand. This is why AI is added to the research now. Whoever is furthest have the upper hand. Because getting the upper hand with regards to physical power can be a lot of things, whoever wants to be in power have to invest in a broad spectrum of areas.
Product/market research:
Solving problems perceptually or real, defined by the market itself or creating new markets but often using knowledge from what was created by governments and millitary (or ex. space travel). These are often accidental and byproducts.
Now here is the problem.
Just because you can define a market or a problem doesn't mean you can find a market for it. You have to find the customers who benefit from and who can pay.
If you took the money away from the millitary and gave it to solve "humanities problems" you would run the risk of loosing the monopoly of power because the problems of the humanity is not the same as those of the individual nation states.
Darpa should have open betting market for these concepts.
Only thing I might moderately bet on is electric motors inside wheels. Electric motors can be more durable, require less maintenance and perform better.
That shaping wheel concept is obvious no go. I would bet serious money against it. Tank tread is the weak point even in modern main battle tank. Their design is simpler but they have problems with mechanical complexity and short lifespan and reliability. Tracks getting jammed or thrown track is relatively common.
Just take a that wheel to a drive across mud, sand and bushes with lots of sticks and stones and see how it goes. Low maintenance and reliability are high on military priorities.
The advantage over tracks is you can lock everything and use the wheel anyway over relatively short distances. So, you trade increased complexity for a vastly better failure mode.
Yea it's bad for the car and passengers, but being able to move even 1 mile after failure is a huge advantage.
Losing track on one wheel is not going to stop one of these things from moving in an emergency. Plenty of videos of people driving even normal cars on rims. ex: https://www.youtube.com/watch?v=-1BgwX3hHgo
You are focusing on very narrow concept and scenario.
The overall maintainability, durability and cost is the issue. The ability of brigades to operate long time independently with minimal maintenance logistics is essential.
I worked in Logistics simulation for a little while.
Humvee armor was a huge issue as it reduced speeds and increased fuel consumption. However, more armor on a small percentage of them was still extremely useful.
IMO, these are of similar value. You don't replace all wheels, but assuming they mostly worked you could swap them in a few vehicles during a monsoon for example then take them out.
Physical limitations of batteries vs air oxidized fuel. Dragging around your own oxidizer takes a lot of mass which severely limits power.
The real breakthrough will be a battery that can use atmospheric oxygen, like a zinc-air battery. But it hasn't worked out in the last 100 years and it's not clear if it ever will.
It's not really a "Moore's law" thing at all - it's more that, like every single other technology in history that isn't specifically semiconductors, batteries don't follow an exponential improvement curve. They also evolve slower than many other technologies even on a more typical growth trajectory, because battery chemistry has way less room for easy improvement. There's only a few battery chemistries that could even theoretically offer much better density than lithium-ion, and we've been trying to make them work for a long time.
I would bet on biodiesel for long distance highway transport, farm equipment, and other heavy industry; and electric in a bewildering array of form factors for short distance urban transport.
That extreme suspension vehicle looks like something out of Batman. Bet it's a hoot to drive.
I thought it was interesting that while they're doing a ton of research, it's all one-off stuff. In other words, they could have required all of the experiments to ter with one another using some standard framework. Then they could mix-and-match various experiments to see how well they work with one another. Instead, it looks like they're evaluating each one separately -- with some huge integration nightmare up head if any of them ever make it into the field. I wonder why they do it that way.
I don't know. I know that some mention was made of the pieces fitting already-existing army wheel specs. So obviously for some groups integration was a consideration.
And it's a mistake to think in all-or-nothing thinking here. I didn't say you needed to design a rock-solid integration system, only that it looked like integration was a minimal concern -- and that was an interesting choice.
I come from the tech community. The longer we put off integration, the more expensive things become.
Putting off integration is cheaper when it's not yet clear what you need to integrate with. Or to frame it differently: having requirements of "be everything for everyone" is a surefire way to fail.
This sub-thread reminds me of the monolith vs microservices kernel discussion I see a lot here. Doesn't Linux benefit from specialized pieces being piped together at will?
Yep. It's a spectrum and a scale. On various scales you want to apply various paradigms. It's not a yes/no thing.
We know for a fact that no matter what they pentagon does with wheels, they need to fit on a body and cost less than a million bucks or so. Even giving the R&D teams wide latitude for they're playing around in, we can start setting some reasonable guardrails up.
The unsprung mass of hub motors makes them terrible for handling, especially at speed (military vehicles top out at "slow person in the right lane" speeds). When you've got a teardrop shaped turd (or economy car, whatever your preferred pronoun is) that's riding 2in off the ground (because how else are you going to be aerodynamic enough to deliver reasonable range) and nearly nil suspension travel (relative to anything expected to operate off road) drive-train and power transmission packaging isn't really an issue (whereas that was the primary issue solved here by going electric).
You should expect to see centrally mounted motors driving the wheels via CV shafts as the dominant EV power-train for the foreseeable future.
113 comments
[ 0.19 ms ] story [ 246 ms ] threadPlease check it out if that sounds cool!
https://youtu.be/cU_0M1_TvD0
Update: link as promised https://news.ycombinator.com/item?id=17108828
bose electromagnetic suspension: https://www.youtube.com/watch?v=WOR8eKBLwXQ
student project: https://www.youtube.com/watch?v=IQ1eKddstxM
It was banned in F1, that combined with the skirts for downforce meant for insane low ground clearances with grip off the scales. You could see cornering speeds going up seemingly without end.
context: https://www.racefans.net/2007/05/17/banned-active-suspension...
The current self driving technology relies on a trunk full of Nvidia cards sucking data in from a few dozen cameras, lidars or radars all working to create a coherent world view, the whole system drawing hundreds of watts of power.
I wonder if it's possible to capture 90% of the performance of that system with simple hardware that can fit such minimal hardware and other applications where failure is an option and has limited consequences.
A thing I'm thinking about lately are lightweight, electric self driving bikes (or more exactly, trikes) running on existing, dedicated bike infrastructure, augmented with some embedded instrumentation. As long as the speed does not exceed 15Km/h and they are guaranteed to never run a red light or run over any object crossing the path, they could be as safe as a human driven bikes.
With solar panels and the right weather, it barley needs to recharge.
https://github.com/tlalexander/rover_control
I’m particularly interested in camera only navigation, localization, and obstacle avoidance, and I hope to get an NVIDIA Xavier board and multiple cameras to use as the sensing system. I’m trying to get myself in a position where I finally have to learn machine learning, and Rover is the project for that!
If the wheels were bigger, it could be double-sided / flippable (no "this side up").
EDIT: Nvm. https://codeduino.com/news/hardware/flutter-the-wireless-ard...
http://flutterwireless.com/index.php?route=product/manufactu...
All products out of stock.
Yeah, I’m using Flutter. I’m the person who made Flutter so I have a lot of them. I used to have bluetooth control from iPhone but I wanted a physical interface. Any remote is trivially easy to add though - the remote is a standalone python program that sends GRPC commands to the motors. I recently got a PS4 remote and may add support for that!
The last point is the biggest advantage of many wheels vehicles over tracks. A detracked tank is a sitting duck, but an 8x8 without a single wheel will happily run away after taking damage
Very easy. There are submerged electric motors for marine propulsion after all.
Wikipedia states the humvee has a 142kw motor.
Not only the vehicle would probably be lighter (batteries vs motor, gearboxes, etc) but it would have 2.81 more power, so it would probably vastly overperform current vehicles?
Tesla Model 3 batteries weight 480kg for 80.5kWh, density of 167Wh/kg.
The DARPA vehicle running for 1h at full power would require a whopping 2400kg of batteries! To give a comparison point, according to Wikipedia, 2400kg is the weight of an Humvee.
I guess it'll still take a little while until the DARPA concept becomes an actual vehicle...
As a general rule, diesel-electric is lighter than pure diesel for a given rating, because the generator doesn't need a powertrain.
Just look at say a Cummins ISB with Allison transmission at 300hp, that's around 225 kilowatts. That combo weighs around 1500 lbs, maybe closer to 2000 with running gear if your comparing to hub motors. A bare frame generator putting out 200+ kw its going to be well over 4000lbs plus whatever hub motors and motor controllers and power systems and batteries weigh.
You can go smaller on the generator and make it up on the battery which means more weight, but even a 100kw generator is going to be around 3000lbs and you won't be able to utilize full power for long periods (long grades).
Perhaps some advanced generator might be lighter, but it essentially the engine with the same size and weight generator attached to it as needed for motors of equivalent power output. Mechanical transmission on the other hand are pretty light comparatively and have much less losses than the mechanical-electrical-mechanical double conversion.
Of course this is going to be heavier than one intended for a vehicle, because the weight isn't a consideration, and lighter is more expensive (more precise, higher-quality materials).
What you'd want to be looking at is train powertrains, which are uniformly diesel-electric, because this is the most efficient power configuration.
Or the Chevy Volt, for a smaller example which happens to run on gasoline.
Trains have 4+ driven axles mounted on bogies that swivel under the chassis. All wheels must be driven (steel on steel doesn't give you much traction) Diesel electric is used in trains because any mechanic transmission that can do that job would be a Rube Goldberg contraption.
A mechanical gearbox is more efficient way of transmitting power because if you've sized things right cruising RPM will be direct drive (no loss from gear friction).
Trains do not use diesel electric drives trains for efficiency or weight, the need precise traction control to prevent the steel wheels from slipping on the tracks to get moving, the electric drive train gives them that. The actual efficiency is lower than a mechanical transmission once up to speed due to double conversion losses. Modern mechanical transmissions are actually very efficient with very low losses.
The Chevy volt also bypasses the electric system at highways speeds due to the inefficiency of converting mechanical energy to electrical and back to mechanical as most (all?) production hybrids. The Gen 2 Volt actually more aggressively move to mechanical drive at lower speed as it was found to be more efficient. The Volt is also heavier then the Cruze even though they share the same platform.
This is an excellent breakdown of the Volt operating modes, in CS2 and CS3 mode the engine is driving the wheels mechnically: https://gm-volt.com/2015/02/20/gen-2-volt-transmission-opera...
Gasoline hybrids like the volt also typically rely on the Atkinson cycle to get better highway efficiency at the expense of torque which is made up for by the electric drivetrain. Diesels are even more efficient and have plenty of torque but also heavier due to a more robust design, this is why they are much less popular in hybrid configurations except in specialized applications like city buses with extreme urban start stop usage.
2nd thought: too bad it's gonna be military use first. I've often heard the argument being made that military applications (and even war itself) somehow drive innovation. While that may be true to an extent, it always rang hollow to me as an argument. Why should civil life always just get the "crumbs" of science and engineering? Why not turn it around, spend most of the research money and brain time on things that benefit everyone (in the US, and worldwide) and then see which of those technologies can be repurposed for the military, not the other way around?
DARPA alone has a bigger budget than NASA, and I just googled "us military research budget" and the numbers for all the arms of the US military are quite staggering, really.
http://slatestarcodex.com/2014/07/30/meditations-on-moloch/ is why not
>From a god’s-eye-view, the best solution is world peace and no country having an army at all. From within the system, no country can unilaterally enforce that, so their best option is to keep on throwing their money into missiles that lie in silos unused.
Funnily enough, we can come full circle and say that many developed nations can survive these days with very little military spending just because America's massive military is enough of a deterrent.
https://en.wikipedia.org/wiki/Pax_Americana
I wish we all get over war, but realistically, as long as we differentiate between "good" and "bad", there will always be some source of enmity to start wars..
Taking something away is not good or bad per se. Sometimes both sides see the other part "taking something away" from them (see any rebellion vs central power conflict).
Also amusingly technologically mutually assured destruction may have started with /fire/ and contributed back in ancient forest Africa. Essentially if there was a rival band to risky to fight and you have mastery of fire setting via a firebreak a contained wildfire would rid a threat and give remaining territory minus what was burnt into immediate uselessness.
I think this is a quirk of the US political system where military spending is the only public spending that is acceptable to both parties in the duopoly. Hence the only stable source of public funding for research is probably in the military sector.
I think it is the incentive that drives this innovation. The consumer market does not face large scale death if it does not innovate.
https://en.wikipedia.org/wiki/Motor_vehicle_fatality_rate_in...
the american military is better because of the technology we have.
The technology we have is because of DARPA spending over the last 80 years.
do you see the flaw in your logic?
I think it’s kind of a silly comparison, tbh. I’d like to see us spend more money on both civilian and military research. I suspect that the military spends plenty of money on shit that is less impactful in the long term than research, and military research also often advances civilian technology.
My point was meant to be quite narrow.
Maybe like the civil war, where both sides were equal and 750,000 Americans died?
Or WW2, fighting against an arguably better Nazi and Japanese military killed 400,000 Americans?
Or WW1, where the stalemate between both sides led to 120,000 american deaths?
You must be right because all those american deaths are preferable to only 2,000 americans who died in the wars in Afghanistan.
/s obviously
Even just back to those 70 million, let's say 73 million as that's where Wiki starts and it seems reasonable. Just imagine that. That's a 9/11 scale of death every single day for 24,366 days. Or a 9/11 scale event every single day for 67 years. That's again difficult to even imagine. And all of that death, with a population 1/3rd of ours today, was compressed into 6 years. Such lessons should never be forgotten, but in a way it's difficult to learn from such things when we really cannot even imagine death and destruction on this scale now a days.
Civilian research is 'harder' in that the advances are less qualitative and more abstract. Is researching amphibian biology going to somehow improve medicine? (Axotls may be anywhere from a dead-end to bringing regeneration). The 'boring' solutions are already there and being worked on. Furthermore there rationalizing secrecy becomes far harder and anything that sounds stupid can be attacked for political points regardless of the underlying reality.
The 'treadmill for shrimp' for instance is attacked as an example of waste when it is the exact opposite - using an innovative way to cut expenses as part of examining the impact of water quality on the health and livelihood of species that are an economic lifeblood in many regions.
We should be actively increasing funding towards programs that benefit youth.
https://www.brookings.edu/research/spending-on-children-and-...
The same is true of the finance sector. How many brilliant minds are toiling away to generate alpha for the investors, when they could be unleashed in other more productive sectors of society?
It's invalid to claim that "X beneficial technology wouldn't have been invented if not for Y war or Z program." Rather, military spending might shift when a technology was demanded by the market. And again, it diverts brilliant minds to one thing, when they could have done something else (that which is not seen) for society.
The other angle is yes, this is awesome tech! But it could not compete in the market, since it is entirely impractical. It only exists because it serves the demands of a program manager at $AGENCY with tax money to spend.
Wow, I can't believe your comment is what we're discussing. I've seen some version of this on the Internet for 30 years now. I must have answered it a dozen times.
Can we turn this into an Internet FAQ? Basically, it wastes everyone's time. If everyone here agreed with you, would it change anything?
If you think the military spends a lot on research, you should see what they spend on non-research.
https://www.npr.org/2011/06/25/137414737/among-the-costs-of-...
If we could turn all of our military spending into non-military R&D, the future would get here so fast! But alas, ...
https://news.ycombinator.com/item?id=3808787
Notice my observation: "Consider that the US economy is $15 trillion. The US handbag market is bigger than DARPA's budget."
Instead HN rewards comments that qualify every achievement with an IF, AND or BUT, or even worse: PFFFT.
Dear HN, you have permission to not be the smartest person in the room. Its actually liberating.
To the people at DARPA who built this - amazing! You are much smarter than me.
I normally think about it like this:
Government research:
Money spent here is the most abstract as it doesn't define a problem before it tries to solve it but rather looks for things we don't understand yet.
Military research:
The point of this research is maintaining power which means researching whatever might give you the upper hand. This is why AI is added to the research now. Whoever is furthest have the upper hand. Because getting the upper hand with regards to physical power can be a lot of things, whoever wants to be in power have to invest in a broad spectrum of areas.
Product/market research:
Solving problems perceptually or real, defined by the market itself or creating new markets but often using knowledge from what was created by governments and millitary (or ex. space travel). These are often accidental and byproducts.
Now here is the problem.
Just because you can define a market or a problem doesn't mean you can find a market for it. You have to find the customers who benefit from and who can pay.
If you took the money away from the millitary and gave it to solve "humanities problems" you would run the risk of loosing the monopoly of power because the problems of the humanity is not the same as those of the individual nation states.
Only thing I might moderately bet on is electric motors inside wheels. Electric motors can be more durable, require less maintenance and perform better.
That shaping wheel concept is obvious no go. I would bet serious money against it. Tank tread is the weak point even in modern main battle tank. Their design is simpler but they have problems with mechanical complexity and short lifespan and reliability. Tracks getting jammed or thrown track is relatively common.
Just take a that wheel to a drive across mud, sand and bushes with lots of sticks and stones and see how it goes. Low maintenance and reliability are high on military priorities.
Yea it's bad for the car and passengers, but being able to move even 1 mile after failure is a huge advantage.
Having tires with adjustable air pressure, or just adding extra pair of wheels (you may lift them up) to the vehicle seems like simpler idea.
The overall maintainability, durability and cost is the issue. The ability of brigades to operate long time independently with minimal maintenance logistics is essential.
Humvee armor was a huge issue as it reduced speeds and increased fuel consumption. However, more armor on a small percentage of them was still extremely useful.
IMO, these are of similar value. You don't replace all wheels, but assuming they mostly worked you could swap them in a few vehicles during a monsoon for example then take them out.
Ferdenand Porsche in 1900 presented a sportscar fitted with four electric wheel-hub motors, it was the first all-wheel drive passenger vehicle.
Where is the progress? The cars should have been flying by now.
The real breakthrough will be a battery that can use atmospheric oxygen, like a zinc-air battery. But it hasn't worked out in the last 100 years and it's not clear if it ever will.
I thought it was interesting that while they're doing a ton of research, it's all one-off stuff. In other words, they could have required all of the experiments to ter with one another using some standard framework. Then they could mix-and-match various experiments to see how well they work with one another. Instead, it looks like they're evaluating each one separately -- with some huge integration nightmare up head if any of them ever make it into the field. I wonder why they do it that way.
And it's a mistake to think in all-or-nothing thinking here. I didn't say you needed to design a rock-solid integration system, only that it looked like integration was a minimal concern -- and that was an interesting choice.
I come from the tech community. The longer we put off integration, the more expensive things become.
We know for a fact that no matter what they pentagon does with wheels, they need to fit on a body and cost less than a million bucks or so. Even giving the R&D teams wide latitude for they're playing around in, we can start setting some reasonable guardrails up.
You should expect to see centrally mounted motors driving the wheels via CV shafts as the dominant EV power-train for the foreseeable future.