ROVER WHEELS: Monitoring changes over time, NOTE: Read back through the thread to avoid repeating misconceptions |
ROVER WHEELS: Monitoring changes over time, NOTE: Read back through the thread to avoid repeating misconceptions |
May 16 2013, 08:35 AM
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Junior Member Group: Members Posts: 22 Joined: 10-August 12 From: Australia Member No.: 6530 |
[MOD NOTE: This thread follows on a post by Ed Truthan containing a MAHLI mosaic of MSL wheels taken on sol 275.]
Ed: zooming in on that marvellous underbelly MAHLI montage, there appears to be further (and previously noted) deformation of the wheel surfaces. Damage is most evident in the view of the front-left wheel inner surface. Such wear has previously been discussed and concerns allayed. Nevertheless, the front left wheel surface *appears* to have been punctured. We've only done 700 meters, and have 7000 more to get to Mt Sharp..... Given that more odometry has now accumulated, is any (re-)new(ed) concern valid? DeanM |
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Jan 17 2014, 11:39 PM
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Founder Group: Chairman Posts: 14434 Joined: 8-February 04 Member No.: 1 |
It's big heavy arm and a lot of torque there if it's stuck out....but....if the rover moved enough for a wheel to get punctures during that process... we would see it in imagery of pre/post arm deployment. We've seen some motion...but only a tiny bit.
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Jan 20 2014, 05:34 PM
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Senior Member Group: Members Posts: 2542 Joined: 13-September 05 Member No.: 497 |
It's big heavy arm... Not doubting Doug at all, but just to put some numbers on that: according to http://www.esmats.eu/esmatspapers/pastpape...ling.pdf the arm mass without the turret is 67 kg, and the turret weighs 34 kg. So it is quite heavy, and I could imagine that it does load up some of the wheels pretty significantly in some poses. I'm not certain if the high-time-res rover orientation data makes it into the SPICE kernels, but if it does, it might be interesting to visualize how much movement the rover actually undergoes when it's nominally stationary. -------------------- Disclaimer: This post is based on public information only. Any opinions are my own.
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Jan 20 2014, 11:30 PM
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Member Group: Members Posts: 495 Joined: 12-February 12 Member No.: 6336 |
Not doubting Doug at all, but just to put some numbers on that: according to http://www.esmats.eu/esmatspapers/pastpape...ling.pdf the arm mass without the turret is 67 kg, and the turret weighs 34 kg. So it is quite heavy, and I could imagine that it does load up some of the wheels pretty significantly in some poses. That's the weight on Earth right? On Mars that give me a weight of 37,47 kg. While the weight is lower, the mass being the same so agreed, it is quite massive also compared to the ones mounted on the predecessor rovers. |
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Jan 20 2014, 11:38 PM
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Senior Member Group: Members Posts: 2542 Joined: 13-September 05 Member No.: 497 |
That's the weight on Earth right? A kilogram is a measure of mass, not weight (I misspoke in my post; the turret mass is 34 kg). The arm has the same mass on Mars that it does on Earth. You say this yourself but I'm not certain what your point is. That said, the resulting pressure on the wheel surface would be lower on Mars. Of course, something is making holes in the wheels; it's either pressure (depends on weight); impact forces (depends more on mass); or some dynamic combination. -------------------- Disclaimer: This post is based on public information only. Any opinions are my own.
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Jan 21 2014, 02:16 PM
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Member Group: Members Posts: 495 Joined: 12-February 12 Member No.: 6336 |
A kilogram is a measure of mass, not weight (I misspoke in my post; the turret mass is 34 kg). The arm has the same mass on Mars that it does on Earth. You say this yourself but I'm not certain what your point is. I am sorry, before posting I edited my reply into obscurity. I mail that part over to you. @elakdawalla: Thank you and I prefer the new number system. |
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