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Mars 2020 Wheel Design, Improving on MSL
anticitizen2
post Jun 6 2015, 06:11 AM
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I was very interested when an MSL flight spare wheel appeared in a sandbox in our High Bay a few months ago.

Attached Image

(Note: this is a 3D printed copy after they were done with the real thing,
to see if they performed the same in order to make testing many iterations easier)


Those on the project have been finishing the setup of the testing system, which will measure the forces on the wheel as it turns and is pulled forward through the loose Mars-sand-analogue, simulating desired slip amounts.

They did many runs with the flight spare to get a baseline, and are moving on to different shapes and grouser layouts sent to them by JPL.
Of course 2020's wheels needs better flotation, traction, and durability. One option is to have a narrower, thicker wheel to keep the same mass.

Attached Image


I'm interested to see what other options are shipped to us.
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elakdawalla
post Jun 8 2015, 04:05 PM
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That is very, very cool -- thanks for sharing the photos smile.gif

I think this warrants a new thread, since it will undoubtedly be a recurrent topic of discussion as they develop Mars 2020! Getting to work on that now...


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Floyd
post Jun 8 2015, 07:15 PM
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I'm a PhD in microbiology, not mechanical engineering, but I have a wheel design of a significantly different geometry (not just changing grousers or their shape) that I think could be quite interesting for NASA to at least see. Anticitizen2 or anyone else at NASA--I'm happy to speak with you. I'd post my design here, but that would be a public disclosure and kill anyone's ability to patent it.

Floyd Dewhirst, DDS, PhD
Senior Member of Staff
The Forsyth Institute
Professor of Oral Medicine, Infection and Immunity
Faculty of Medicine, Harvard School of Dental Medicine


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anticitizen2
post Aug 19 2015, 06:22 PM
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A few more wheels in - looks like standard number of grousers and 2/3 of MSL's width.

Each wheel is printed in 5 segments, to explain the big seams you can see

I had been waiting for these 'weird' wheels to start coming in. A bunch more are expected, as the experimenting gets crazy before it starts honing in on a goal in a year or so, I'd guess.

Attached Image
Attached Image
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elakdawalla
post Aug 19 2015, 08:59 PM
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Thanks for sharing these photos. In the first image, the rear wheel seems to slope down from one rim to the other (that is, it seems to have a smaller diameter on one side than the other) -- is that real or a distortion in the photo?


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anticitizen2
post Aug 19 2015, 10:15 PM
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Distortion from the photo, I was standing to the left. So far they're all MSL radius, no varying radius.


Just to be clear, I'm not involved with this testing program. I work in the same building, it caught my eye, and I've asked some of the people about the status of the testing- e.g. If they're expecting more wheels soon. All comments have been my opinion or observation
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HSchirmer
post Aug 20 2015, 01:43 PM
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QUOTE (anticitizen2 @ Jun 6 2015, 06:11 AM) *
I was very interested when an MSL flight spare wheel appeared in a sandbox in our High Bay a few months ago.

Attached Image

(Note: this is a 3D printed copy after they were done with the real thing,
to see if they performed the same in order to make testing many iterations easier)


Those on the project have been finishing the setup of the testing system, which will measure the forces on the wheel as it turns and is pulled forward through the loose Mars-sand-analogue, simulating desired slip amounts.

They did many runs with the flight spare to get a baseline, and are moving on to different shapes and grouser layouts sent to them by JPL.
Of course 2020's wheels needs better flotation, traction, and durability. One option is to have a narrower, thicker wheel to keep the same mass.

Attached Image


I'm interested to see what other options are shipped to us.


Hmm, that reminds me of the mad-scientist-parody but-still-brilliant "DreadCo everlasting Tyre" NewScientist April 1, 1982

https://books.google.com/books?id=FCfWxhHWA...p;q&f=false

Interesting that the wheels are printed.
Will the next generation chem-cam laser have power similar to the laser in a 3-d printer?
Hmm, a rover that could patch its own tires.




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elakdawalla
post Aug 20 2015, 03:49 PM
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I'm certain that it's only the test article wheels that are being 3D printed, to rapidly run through a wide variety of tread designs in the sandbox. Anything sent to Mars will probably be machined titanium or aluminum, like the previous wheels.


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anticitizen2
post Aug 20 2015, 09:30 PM
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Yes, the printed plastic ones are only for testing.
Testing many iterations of machined aluminum wheels would get insanely expensive.

This is why, as shown in the very first picture, they tested an MSL flight spare against a 3D printed copy to first get some knowledge about the performance difference between materials before moving on to different printed designs.
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HSchirmer
post Aug 20 2015, 10:46 PM
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QUOTE (anticitizen2 @ Aug 20 2015, 09:30 PM) *
Yes, the printed plastic ones are only for testing.
Testing many iterations of machined aluminum wheels would get insanely expensive.

This is why, as shown in the very first picture, they tested an MSL flight spare against a 3D printed copy to first get some knowledge about the performance difference between materials before moving on to different printed designs.



Well, you can print aluminum...

3D Printed Aluminum Lattice Cube Weighs Just 3.9g & Holds up to 900lbs (408kg) – Over 100,000 Times Its Weight!
Attached thumbnail(s)
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djellison
post Aug 20 2015, 11:10 PM
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It also costs an order of magnitude more than printing a plastic one.
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anticitizen2
post Feb 8 2016, 06:10 PM
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New wheel on the scarecrow. Enlarged crop attached.

https://pbs.twimg.com/media/CataYkMUcAA8nd5.jpg:orig

Attached Image


Looks to be 2/3 the width, straight grousers, and with a crown, unlike the wheels in the first post.
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anticitizen2
post Mar 9 2016, 07:03 AM
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Last update from me on this topic, unfortunately. I'm no longer working next to the wheel testbed, but hopefully I can get some pictures of InSight or OSIRIS-REx

Attached Image


Hard see the distinction, but the grousers are different lengths. Wish I could have seen more crazy grouser patterns.

I wonder if the skinny wheels are here to stay. This testing will tell us if there is enough flotation and traction.
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elakdawalla
post Mar 9 2016, 08:26 PM
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Wow, those grousers are much deeper than previous wheels. People always told me the grousers only needed to be as long as the grain size was large, which is why the Curiosity grousers were so shallow. I guess that rule of thumb isn't true?


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Burmese
post Jul 16 2016, 03:33 AM
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Since the Rover 2020 design just passed review, are there any more concrete details available on the final wheel design, or is that something that can still be very much in flux at this stage even under review? I would imagine the review team paid particular attention to that aspect of the presentation.
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