An aluminium rotor that never wears out .......because it never rusts!?

http://articles.sae.org/15593/

Can't see the story it's showing me an error.

 

But iron disks don't wear out because they rust. They wear out because of the friction between the pad and the disk.

Ceramic disks won't rust ever, but they still wear out.

 

Aluminium is a pretty brittle metal but it's quite hard. It does still oxidise as well but unlike iron oxide it's doesn't flake off. It'll also burn if it gets too hot.

 

I suppose it would be possible to make disks from aluminium alloy. But if it was that easy I think they'd be using that before ceramic.

 

[edit] aluminium is nothing new

 

https://itstillruns.com/aluminum-rotors-vs-cast-iron-rotors-12214533.html

http://www.lotustalk.com/forums/f91/aluminium-brake-discs-31534/

Edited 26 October, 20178 yr by Aspman

@Ryeman - "Aluminium never rusts" - That's true, for certain values of true involving the fact that the word "rust" refers specifically to iron and steel.

 

Aluminium most certainly does corrode, and it's the fact that the layer of aluminium oxide which forms coats the bulk metal with a waterproof layer until it's rubbed off that makes the rate of corrosion low.

From reading the article, they're betting on regenerative braking taking most of the braking load in the intended applications, with the friction brake being called on for hard stops or to distribute braking forces between axles.

 

Their comment on corrosion is that lightly used steel disks suffer from poor braking when applied due to the rust layer shearing off before the brakes kick in. An aluminium disk with a cohesive oxide layer wouldn't suffer from this issue.

 

My biggest concern with the concept they've presented is how straightforward wheel changes will be with the setup. Looks like you'd need to unbolt the wheel at the edges as well as or instead of the hub which could be a real PITA.

Interesting that they wouldn’t mention the aluminium composition.

@chimaera - So how durable do we think the cohesive oxide layer actually is when regularly rubbed by a brake pad, and maybe road grit?

@Ryeman I can't speak for Chimaera, but I understood about the cohesive oxide layer without needing to read the article. I'd just forgotten the technical term when I wrote post #2.

Oh it'll abrade under those conditions, but the fact that it's not flaking off and creating a 'lubricant' layer the way rust on steel does should improve braking.

 

Another advantage to aluminium here that I haven't seen mentioned is the lower polar moment of inertia due to the lower density. For a disk that's such a large diameter, steel would be problematic in this regard.

@chimaera - Yeah I'll agree all that; what annoys me is people who's understanding of chemistry is so low that they think "I can't see a colour change so this metal doesn't corrode", or indeed that "rust" is a generic term rather than specific to ferrous metals.

and how long a pad will last rubbed by a layer of ally oxide ?

10 minutes ago, cheshire_cat said:

and how long a pad will last rubbed by a layer of ally oxide ?

 

On an EV with the regenerative braking doing most of the work the pads should last a long time as well.

 

If they can save weight on an EV they'll be looking at better range figures on paper as well.