Were the Lunar Rovers faked?

[Allan F]

I can't really follow that calculation, but it seems you have forgotten that each wheel had 1/4 horsepower. Also, the mass of the LRV is too low, and you have forgotten to add the weight mass of the astronauts.

[onebigmonkey]

anywho, let's recap:

So you went to The rover wasn't strong enough to support two astronauts' weight in 1G.

     You failed to support that assumption (they made a 1G rover for training.... and photos).

For the 100th time, it was not me who said that the rover could not support the rovers weight in 1g, it is NASA, all I am saying is that it makes no sense for them them to say that the lunar rovers were too weak to support the astronauts weight but then they can take it to the moon and slam it into craters at 10kph.

No, they didn't say that, you did.

anywho, let's recap:


So you went to The Moon is slippery as ice so the rover wouldn't have worked.

     You failed to support that assumption (you admit no knowledge of lunar surface conditions).

So you went to The rover had to pull over 5 times it's weight, which it couldn't do.

     You failed to support that assumption (a = F/m).

I admit I was wrong about the drawbar pull coefficient needing to be 5 to accelerate (longer post coming when I have time, which will show that traction on the moon is indeed comparable to ice on earth), but it is still true that the rovers need power and traction to pull the entire mass of the vehicle, which on the moon is 6 times the weight. That is irrefutable.

Once again, with feeling, what evidence will you be using to demonstrate that the lunar surface exhibits the qualities you so desperately want it to have? How on Earth (no pun intended) do you draw the conclusion that a surface composed of jagged particles and rocks has absolutely no friction? Sources pelase, links, whatever.

Secondly, the mass may be 6 times the weight, but can you please remind us again by how much, proportionately, the resistance to moving that mass provided by gravity is compared with Earth?

So you now have gone to The tire chevrons were chosen to look cool instead of assisting operation.

     You have yet to support that assumption (and how would that help prove fakery?).

I didn't just say the were a triumph of style over substance, I gave my reasons, the chevrons cover 50% of the fictive surface, they recess the remaining 50%, they are smooth and they are thin so provide very little by way of tread.

They're just plain dumb, an elegant solution might have been to put the chevrons on the inside of the mesh but when it's all a farce, why bother?

Do please provide us with a manufacturing method that would allow the chevrons to be placed inside the mesh.

e2a: Let's be honest here. it wouldn't matter which tyre they'd chosen, it wouldn't matter what tractive capabilities the LRV possessed, you'd still be arguing that it was incapable of doing it. If they'd gone for the straight mesh, you'd be saying that the LRV would have sunk in to the ground.

You just plain old don't believe it, and this is the thing you've latched on to as your big 'a-haa' moment.

[anywho]

I can't really follow that calculation, but it seems you have forgotten that each wheel had 1/4 horsepower. Also, the mass of the LRV is too low, and you have forgotten to add the weight mass of the astronauts.

The mass I used is 1/4 the total, the rover is 1600lbs total fully loaded.

I worked it out on 1 wheel with 1/4hp having to accelerate 400lbs, instead of 1hp having to accelerate 1600lbs.

[Abaddon]

anywho, let's recap:

You started with The motors were too small.

     You failed to support that assumption (it was shown that they weren't too small).

It was never "shown that they weren't too small", not only are the motors ridiculously small for such a large mass but the wheels are ridiculously large, I have (admittedly) belatedly done some calculations.

1/4hp @ 125rpm = torque 10.5 lb.ft, tyre radius 15inch, mass fully loaded 400lbs.

F = 10.5/1.25= 8.4

8.4/400 = 0.021

0.021*32.18 = 0.68 ft/s/s  or  0.2m/s/s (more than 13s to make it to 10kph)

You last line is the most egregious. You have multiplied an acceleration by an acceleration, yielding units of ft²/s⁴ which is pretty meaningless.

[ka9q]

For the 100th time, it was not me who said that the rover could not support the rovers weight in 1g, it is NASA, all I am saying is that it makes no sense for them them to say that the lunar rovers were too weak to support the astronauts weight but then they can take it to the moon and slam it into craters at 10kph.

But you never bothered to find out why the lunar rover could not support the astronauts on earth, did you?

If you had, you would have discovered the reason was the tires. You want your tires to normally deflect a certain amount, so because of the lower lunar gravity they had to be made softer. This also made them subject to bottoming out and damage if the astronauts sat on the rover in 1-g on earth.

The fact that the rest of the rover was quite strong is proved by the existence of the 1-g training rover, which is largely identical to the lunar model and has no special structural reinforcements. The differences between it and the lunar version were primarily the tires (ordinary pneumatics designed for 1-g) and differences in equipment for environmental and operational reasons (the training rover operated in air and had a much longer service life).

So this is all really very simple, but you didn't bother to find any of it out.

[Jason Thompson]

For the 100th time, it was not me who said that the rover could not support the rovers weight in 1g, it is NASA,

But you didn't bother to find out why they said that, did you? You didn't go off and figure out what it was about the rover design that made it unable to be sat on here on Earth, and why that would not necessarily be a problem on the Moon, did you?

Why?

I admit I was wrong about the drawbar pull coefficient needing to be 5 to accelerate

Hurrah! It's only taken days of us constantly battering you with counter-examples and explanations and so on...

but it is still true that the rovers need power and traction to pull the entire mass of the vehicle, which on the moon is 6 times the weight. That is irrefutable.

Yes, they need to accelerate the mass, but as we have repeatedly said, if the traction is there the mass can be accelerated by any force.

They're just plain dumb,

Since that opinion is clearly based on no engineering or physics expertise of any significant level, I think we can safely discount it.

Once again, there is film of that tyre design working very nicely. Why do you dismiss it as dumb when it clearly works?

[Jason Thompson]

I have (admittedly) belatedly done some calculations.

Now do them again and show all your work. You've got numbers in there with no explanation of what they are or how you obtained them. Your presentation would be ignored by any competent scientist or engineer for that reason. Show your work. All of it.

(more than 13s to make it to 10kph)

So what? The rover wasn't a drag racer.

[Mag40]

It was never "shown that they weren't too small", not only are the motors ridiculously small for such a large mass but the wheels are ridiculously large, I have (admittedly) belatedly done some calculations.

1/4hp @ 125rpm = torque 10.5 lb.ft, tyre radius 15inch, mass fully loaded 400lbs.

So the torque is worked out from the 10,000rpm of the motor via a 80:1 harmonic drive.
T = 5252 x HP /  rpm

F = 10.5/1.25= 8.4

OK, with you so far. This is the Linear Force equation and 1.25 is the radius in feet(15 inches).

8.4/400 = 0.021

So this is supposed to be acceleration=linear force/mass.

0.021*32.18 = 0.68 ft/s/s  or  0.2m/s/s (more than 13s to make it to 10kph)

Now I'm lost. 0.021ft per second * 32.18 feet per second. You appear to be multiplying the acceleration of one wheel on the LRV by the gravitational acceleration on Earth.

Is that right and why? What is this 32.18 figure if not the gravity of Earth?

[anywho]

But you never bothered to find out why the lunar rover could not support the astronauts on earth, did you?

If you had, you would have discovered the reason was the tires.

The fact that the rest of the rover was quite strong is proved by the existence of the 1-g training rover, which is largely identical to the lunar model and has no special structural reinforcements. The differences between it and the lunar version were primarily the tires (ordinary pneumatics designed for 1-g) and differences in equipment for environmental and operational reasons (the training rover operated in air and had a much longer service life).

So this is all really very simple, but you didn't bother to find any of it out.

Do you have a reference for any of this?

I have never read any document that specifies the wheels as the problem, and the two NASA quotes I supplied suggest that the structural problems go beyond the wheels

It is often said that if astronauts could not even sit on a Lunar Rover here on Earth because the Rovers were built of such lightweight construction that they "would have collapsed in 1 g if the crew sat on it." (1), and that the " The vehicle could support its own weight on earth, but no more" (2).


(1) http://ares.jsc.nasa.gov/HumanExplore/Exploration/EXLibrary/docs/ApolloCat/Part1/LRV.htm

(2) http://www.hq.nasa.gov/office/pao/History/SP-4204/ch23-3.html

And why would the wheels be damaged by astronauts sitting on the rover in 1g anyhow? If they can withstand being driven into crater walls at 10kph with the same mass then they too should be able to be sat on.

[anywho]

It was never "shown that they weren't too small", not only are the motors ridiculously small for such a large mass but the wheels are ridiculously large, I have (admittedly) belatedly done some calculations.

1/4hp @ 125rpm = torque 10.5 lb.ft, tyre radius 15inch, mass fully loaded 400lbs.

So the torque is worked out from the 10,000rpm of the motor via a 80:1 harmonic drive.
T = 5252 x HP /  rpm

F = 10.5/1.25= 8.4

OK, with you so far. This is the Linear Force equation and 1.25 is the radius in inches.

8.4/400 = 0.021

So this is supposed to be acceleration=linear force/mass.

0.021*32.18 = 0.68 ft/s/s  or  0.2m/s/s (more than 13s to make it to 10kph)

Now I'm lost. 0.021ft per second * 32.18 feet per second. You appear to be multiplying the acceleration of one wheel on the LRV by the gravitational acceleration on Earth.

Is that right and why? What is this 32.18 figure if not the gravity of Earth?

It's a fraction of G, I will probably describe it wrong so I will give a demonstration instead.

If the force equalled 400lb and the mass to be accelerated was also 400lbs then it would be 400/400 = 1, then to convert 1g to ft/s/s you would multiply it by 32.18.

Or, if F/m was 200/400, it would equal 0.5, then 0.5*32.18 equals 16.09 ft/s/s (or 0.5g)
 
This formula is not restricted to earths gravity, it is still a=F/m, it's just what you have to do when using lbs.

[Jason Thompson]

And why would the wheels be damaged by astronauts sitting on the rover in 1g anyhow? If they can withstand being driven into crater walls at 10kph with the same mass then they too should be able to be sat on.

And you still don't get the difference between a short sharp load that allows the wheels to deform and then spring back elastically and a sustained load that leads to plastic deformation, do you?

[Jason Thompson]

If the force equalled 400lb and the mass to be accelerated was also 400lbs then it would be 400/400 = 1, then to convert 1g to ft/s/s you would multiply it by 32.18.

And your reason for leaving the unit 'g' off in your original post was what, then?

Your presentation of equations is sloppy to say the least.

[Echnaton]

but it is still true that the rovers need power and traction to pull the entire mass of the vehicle, which on the moon is 6 times the weight. That is irrefutable.

Anywho,  have you ever looked a powered trailer dollies?  Using a 1.5 HP motor they can move 11K lbs trailers.  The smallest of the ones I've seen have 1/4 HP motors and are used to move small boat or RV trailers.   All on earth.  There is simply no argument by analogy that can hold in claiming that the LRV was underpowered.  We await your belated analysis.

For your Reference

[Mag40]

The mass I used is 1/4 the total, the rover is 1600lbs total fully loaded.

When was it fully loaded? The figures on wiki come in at 1543lbs total.

But so what, with the only visible speed evidence on the Moon being the LRV Apollo 16 grand prix, we have one astronaut on board, 200lbs mass per wheel and 6.5 seconds to get up to 10kps.

And? What was your point?

[gillianren]

It's a fraction of G, I will probably describe it wrong so I will give a demonstration instead.

Oh, dear.  You just really don't know the physics on this at all, do you?  You've learned an equation or two; well done.  But you don't know how to apply them or what they mean, do you?

And for the umpteenth time, why do you assume that you're right?  When engineers from around the world, including countries hostile to the US, disagree with you, why do you assume that you're right and they're wrong?