ROVER WHEELS: Monitoring changes over time, NOTE: Read back through the thread to avoid repeating misconceptions Options

[DeanM]

[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

[Ant103]

The dents may be reflecting bits of bright sky which makes it look like there are punctures.

It can't be. We are seeing these things in shadow, and from where there are, impossible to have the sky in sight. Because of the wheel itself, and the rover body.

I'm wondering about the material used to build theses wheels. At first, I thought they where designed in the exact same way as the MER's : a metalic monobloc.

[djellison]

It can't be

It is. That 'hole' is a dent, the stress of the dent has popped the anodized coating off the inside of the wheel and we have bare aluminum reflecting the sun. That dent isn't in shadow. Those that are can reflect the bright martian sky off them. Just because something is in shadow - it doesn't mean it can't 'see the sky'.

Look at it - it's not even the same color as the terrain behind it.

And even if it IS punctured - it doesn't matter.

Once of the test-bed rovers at JPL had flight like wheels whilst dealing with 3x the effective weight of a real rover. The wheels were punctured, dent ridden, ripped, torn, dinged, bashed, smashed, crunched. You could put your finger thru the holes in places - you could see clean thru them.

And they still worked absolutely fine.

That testbed now has tougher wheels simply to deal with terrestrial gravity. The lightweight scarecrow rover has flightlike wheels.

I'm not sure how long it's going to take until saying 'the wheels are fine' before it gets boring. Infact, I think it might already have passed.

[Jimbo1955]

It is. That 'hole' is a dent, the stress of the dent has popped the anodized coating off the inside of the wheel and we have bare aluminum reflecting the sun. That dent isn't in shadow. Those that are can reflect the bright martian sky off them. Just because something is in shadow - it doesn't mean it can't 'see the sky'.

Look at it - it's not even the same color as the terrain behind it.

And even if it IS punctured - it doesn't matter.

Once of the test-bed rovers at JPL had flight like wheels whilst dealing with 3x the effective weight of a real rover. The wheels were punctured, dent ridden, ripped, torn, dinged, bashed, smashed, crunched. You could put your finger thru the holes in places - you could see clean thru them.

And they still worked absolutely fine.

That testbed now has tougher wheels simply to deal with terrestrial gravity. The lightweight scarecrow rover has flightlike wheels.

I'm not sure how long it's going to take until saying 'the wheels are fine' before it gets boring. Infact, I think it might already have passed.

I certainly don't know the coating or type of specific anodizing used, but anodizing in general is not a coating that can be "popped" off. Anodizing involves an etching process process to create a sponge-like texture into the metal. Dyes or other other additives are infused into the spongy porous surface of the metal. Could the anodized metal have a coating applied over it? Sure. I would rather suspect that a gouge in the metal which removed the anodized metal to expose the un-anodized surface.

-J

[mcaplinger]

I certainly don't know the coating or type of specific anodizing used, but anodizing in general is not a coating that can be "popped" off.

Anodizing is an electrochemical process whereby the top layer of aluminum is converted to alumina (AlO2) -- http://en.wikipedia.org/wiki/Anodizing
There are several types and they tend to produce different thicknesses of alumina. In my experience, you can get a thin layer to pop off if you work at it, but I suspect that these dents are just specular highlights off the intact anodizing, since the black anodizing is not very matte.

[mcaplinger]

Doug has seen the damaged VSTB wheels in person and I haven't, so he's in a better position than me to know if the anodizing is actually broken off or not.