Earlier quoted context omitted.
> Let NASA have high zoot. NASA does really rather well with high reliabilty. The Martian rovers have managed without a service.
To be fair, nobody has been shooting at them.
And yet, they've had wheel problems.
Darpa Literally Reinvented the Wheel for Army Combat Vehicles
191–200 of 220 posts
Re: Darpa Literally Reinvented the Wheel for Army Combat Vehicles
#192As a military officer, I pray these never make it past Test and Evaluation. They took essentially one part and turned it into 1000 parts. Anyone who has seen what 20 year old Marines do with these machines, let alone what happens in war, will appreciate that this is a fantastically horrible idea in a war zone. I need high reliability, not high zoot. Let NASA have high zoot.
These were my thoughts also. During WW II German tanks were technologically superior to Russian tanks. However Russian tanks were easy to repair in the field and that was one of the reasons why Russian armour prevailed over German armour.
This talks about this a bit, and many other examples of Russian military equipment simplicity:
http://militera.lib.ru/research/suvorov12/06.html
I have heard the book this is from is somewhat inaccurate, but it makes for a good read.
Re: Darpa Literally Reinvented the Wheel for Army Combat Vehicles
#193Earlier quoted context omitted.
>But what if test and evaluation prove they are more reliable than tires filled with air? That won't happen. Just the fact that there are so many moving parts, controlled by microcontrolelrs, all with multiple independent fail points makes the idea that these are more reliably just absurd. The only question is, is the trade off of less reliability worth the advantage they provide. I don't see it, but maybe there are…
Today's cars are so much more complex than old cars. Yet almost all of them are much more reliable than old cars. I don't think simple == reliable. A wheel made of solid wood is very simple. But the choice of material is poor. So there are a lot more factors involved to make something reliable. Getting stuck in the dirt might be more dangerous than a wheel with 1000 parts that gets you out of a nasty situation. Also:…
One major difference, reliability-wise, of modern vehicles is electronic engine management---electronic fuel injection, electronic ignition, etc. These are, in fact, much simpler than their previous mechanical counterparts.
Materials are better, as are engineering, but those are a wash complexity-wise.
The major complexity increase has been antilock braking/traction control/stability control, all of which are (I hope!) designed to fail back to their older mechanical state. Their reliability has improved considerably, but my 2004 Corvette may need another brake controller rebuild and the brake controller on my 1995 BMW motorcycle's primary purpose seems to be to test for low-voltage conditions when I start the bike.
Re: Darpa Literally Reinvented the Wheel for Army Combat Vehicles
#194As a military officer, I pray these never make it past Test and Evaluation. They took essentially one part and turned it into 1000 parts. Anyone who has seen what 20 year old Marines do with these machines, let alone what happens in war, will appreciate that this is a fantastically horrible idea in a war zone. I need high reliability, not high zoot. Let NASA have high zoot.
Yeah this is cool looking but isnt it just as effective and simpler to just have big knobby tires with adjustable pressure?
Boring, exists for decades already.
Re: Darpa Literally Reinvented the Wheel for Army Combat Vehicles
#195Earlier quoted context omitted.
But there are millions of young males in the US alone who are more careful than millions of young females. The effects of testosterone are far from as simple as you suggest. It tends to lead to higher competitiveness. This is not quite the same as recklessness. Meanwhile during normal usage the driver (of whatever gender) is likely to be getting shot at. This will tend to have a larger affect than their gender.
> there are millions of young males in the US alone who are more careful than millions of young females Yes, and millions of young men in the US who are shorter than millions of young women. What’s your point? Young men are still disproportionately more likely to be in road traffic accidents. Re testosterone, the keywords you should be searching for are “risk taking behaviour”. I’m curious also what percentage of tim…
Looking at a few studies, the data is much more complex. For example, higher levels of circulating testosterone were associated with lower risk aversion among women (r = −0.1793; P = 0.01), but not among men (P = 0.11). However at comparably low concentrations of testosterone the gender difference in risk aversion disappeared, suggesting that testosterone has nonlinear effects on risk aversion regardless of gender.
Or to make a summery of the summery of the study: there is an association of risk aversion when going from low levels of testosterone to very low levels, but "male with high testosterone" is not supported in that study as increased risk taking behavior vs males with normal levels of testosterone.
Re: Darpa Literally Reinvented the Wheel for Army Combat Vehicles
#196Earlier quoted context omitted.
Yeah this is cool looking but isnt it just as effective and simpler to just have big knobby tires with adjustable pressure?
Boring, exists for decades already.
That's a good point. There's got to be a way I can replace these wheels with some sort of modern javascript framework.
Re: Darpa Literally Reinvented the Wheel for Army Combat Vehicles
#197Earlier quoted context omitted.
Wouldn't you still have that same problem if an ordinary wheel gets damaged?
I think the probability of damage is higher is what they are thinking. I would say that the complexity is far higher in this case, so it is easier to pop 5 bolts and swap a tire then swap.....bolts, then unhook whatever is controlling them.
We're now just guessing how easy or hard it is to swap these wheels. It might be that the replacement mechanism was reinvented as well so it's easier to swap than a standard wheel. But equally you might be right that there are more parts to unhook. Either way it is just guesswork.
Re: Darpa Literally Reinvented the Wheel for Army Combat Vehicles
#198As a military officer, I pray these never make it past Test and Evaluation. They took essentially one part and turned it into 1000 parts. Anyone who has seen what 20 year old Marines do with these machines, let alone what happens in war, will appreciate that this is a fantastically horrible idea in a war zone. I need high reliability, not high zoot. Let NASA have high zoot.
As former military, I also concur. There is no time to read a manual or tinker. It must be simple so that anyone in the field can adapt, improvise and overcome. Or at least, quickly limp away from harm. Also, the H1 already breaks enough without adding more crud. I had the H1 wagon and replaced damn near everything on it. I can't even fathom taking that nightmare apart in the mud. CTS and runflats were enough fun.
Re: Darpa Literally Reinvented the Wheel for Army Combat Vehicles
#199Isn't the advantage of using tracks supposed to be the increased surface area for traction and weight bearing? This seems to only slightly increase the surface area. It doesn't seem that this would have enough traction advantage to make the complexity worth it.
Back of the envelope:
One car weighs ~3500 lbs. If I keep 35psi of air pressure in the tires, that works out to ~100in^2 of contact patch. With four wheels, that's 25in^2 per wheel or 5in square.
This looks like the tread-extended contact patch is more like 12in long times the original width, or 60in^2. That halves the weight per square inch.
Re: Darpa Literally Reinvented the Wheel for Army Combat Vehicles
#200Earlier quoted context omitted.
These were my thoughts also. During WW II German tanks were technologically superior to Russian tanks. However Russian tanks were easy to repair in the field and that was one of the reasons why Russian armour prevailed over German armour.
Define technically superior? The German tanks had massive reliability problems, not just ease of repair they broke down under non-striker's situations. They were technical nightmares.
You can be a technological nightmare if you get to shoot a kilometer before the enemy.