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Darpa Literally Reinvented the Wheel for Army Combat Vehicles

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Re: Darpa Literally Reinvented the Wheel for Army Combat Vehicles

#71

Post by ridgeguy »

qaq wrote: post #35
Swizec wrote: post #20

Earlier quoted context omitted.

Humvees get stuck a lot! The US donated (I’m sure with wink wink strings attached) to us, Slovenia, some years ago and it was quickly found that they are too large and cumbersome for our foresty mountanous terrain. They’d get stuck all the time on tiny roads or between trees. I think these days they’re used for paraded to show we have them but day to day the military keeps using their trusti Puchs from who knows when…

US is not fighting in areas where getting stuck between trees is a big issue.

Today.

Re: Darpa Literally Reinvented the Wheel for Army Combat Vehicles

#72

Post by UncleEntity »

sooper wrote: post #65
make3 wrote: post #53

That video at the end about the army throwing Humvees without properly setting up the chutes was pretty incredible

From what I read, not so much "without properly setting up", more sabotage: https://www.armytimes.com/news/your-army/2017/07/05/soldier-...

Makes me wonder why nobody checked their work, parachute failures get investigated pretty thoroughly so it's not like you're going to get away with burning in a few hummers.

Though "Never attribute to malice that which is adequately explained by stupidity." Back in '90 or so I was on the ground crew for a jump they were doing to impress some Soviet generals and they jumped with too high winds which resulted in two arty canons and a sheridan tank burning in (they got to oscillating so bad the chutes collapsed) and three planes worth of troops ending up in the trees. Bad day to jump but made for an interesting day on the ground.

Re: Darpa Literally Reinvented the Wheel for Army Combat Vehicles

#73

Post by tCfD »

namirez wrote: post #49
stefco_ wrote: post #46

Earlier quoted context omitted.

Note that the whole assembly rotates when in wheel mode. Making it radially symmetric (i.e. a triangle) in track mode means that it can switch modes with at most a 120 degree rotation rather than having to rotate through up to 360 degrees to get the flat bottom into position.

I didn't say anything about the design of it, which is by the way, very cool. I don't understand the point of the triangle. The same mechanism could be used to change the geometry of the wheel only at the bottom.

I suspect it may apply torque from the drivetrain to the mechanism with the most optimal geometric leverage against both the mechanisms internal frame and the contact patch on the ground during transition into and out of tread mode.

Re: Darpa Literally Reinvented the Wheel for Army Combat Vehicles

#75

Post by UncleEntity »

banku_brougham wrote: post #17
AndrewKemendo wrote: post #5

That thing looks like a maintenance nightmare.

And how often do humvees get stuck anyway? I like the product, but it’s obviously wasteful. During the Iraq insurgency what was wanted was armor plating. Literally just 1/4” slabs of steel. This is of a piece with the F-35.

I saw one get stuck so bad in the sand it took three tanks to pull it out over in Saudi. Was sitting with the frame on the ground so no way to dig it out (trust me, they had us try).

Re: Darpa Literally Reinvented the Wheel for Army Combat Vehicles

#76

Post by ryanmarsh »

Glorious news for all privates who’ve ever had to haul a Humvee out of a mud-filled ditch

I’ve seen plenty of tanks get stuck but honest to god I don’t ever recall a HMMWV getting stuck. I used to try to get my HMMWV stuck. That thing is geared so low it just walked out of soup up to the hood. Tracks are advantageous when more surface area is needed to spread the weight out, like soft wet ground (mud) or very fine loose (think sand dunes). It will be nice to have the added mobility for certain missions but I don’t see this becoming organic to most units. The vast majority of missions just don’t need these wheels and they look like they’ll break.

Re: Darpa Literally Reinvented the Wheel for Army Combat Vehicles

#77

Post by egypturnash »

namirez wrote: post #49
stefco_ wrote: post #46

Earlier quoted context omitted.

Note that the whole assembly rotates when in wheel mode. Making it radially symmetric (i.e. a triangle) in track mode means that it can switch modes with at most a 120 degree rotation rather than having to rotate through up to 360 degrees to get the flat bottom into position.

I didn't say anything about the design of it, which is by the way, very cool. I don't understand the point of the triangle. The same mechanism could be used to change the geometry of the wheel only at the bottom.

Changing it only at the bottom adds complexity: Which side is at the bottom right now? How can we know this; how can we know this in a way that will survive the tough conditions we expect this to be driven in? And then we need to have three separate actuator paths to transform just one part of the wheel.

We would also need to deal with the fact that just flattening one side of the wheel would make for a shorter perimeter than that of the circle; the tread is a loop of a constant length, and it needs to be kept fairly taut to function in both wheel and tread mode.

Re: Darpa Literally Reinvented the Wheel for Army Combat Vehicles

#78

Post by ryanmarsh »

gnarbarian wrote: post #69
namirez wrote: post #44

I don't understand the benefit of turning the whole wheel into a triangular track; would it not be sufficient to make only the bottom third flat?

If it wasn't symmetrical it would be far more difficult to balance properly for when it's rotating in "wheel mode"

Yah the real trick is seeing that thing spin perfectly at highway speed.

Re: Darpa Literally Reinvented the Wheel for Army Combat Vehicles

#79

Post by ryanmarsh »

UncleEntity wrote: post #72
sooper wrote: post #65

Earlier quoted context omitted.

From what I read, not so much "without properly setting up", more sabotage: https://www.armytimes.com/news/your-army/2017/07/05/soldier-...

Makes me wonder why nobody checked their work, parachute failures get investigated pretty thoroughly so it's not like you're going to get away with burning in a few hummers. Though "Never attribute to malice that which is adequately explained by stupidity." Back in '90 or so I was on the ground crew for a jump they were doing to impress some Soviet generals and they jumped with too high winds which resulted in two ar…

DZSO was either begging them to stop or should’ve been relieved for cause.

Re: Darpa Literally Reinvented the Wheel for Army Combat Vehicles

#80

Post by ryanmarsh »

jandrewrogers wrote: post #68
gpm wrote: post #43

Earlier quoted context omitted.

Given how much money the US spends on its military I'd expect them to be prepared to fight just about anywhere. Certainly in "foresty mountanous terrain" since that isn't particularly rare. Exists inside of the US. Exists on both borders of the US. Etc. Producing a military optimized for "blowing up unsophisticated enemies in desserts" seems like a very shorted sighted way to spend the military budget. (None of the a…

The US military has divisions that specialize in "foresty mountainous terrain". There are parts of the world (and US) that are effectively inaccessible to any mechanized units and the US military has large combat units that are setup to operate effectively in those environments. Terrain that is prohibitive to mechanized units is traditionally the domain of "light infantry" divisions (e.g. 10th Mountain Division), dis…

Yes unfortunately that makes for some miserable training.
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