Ok I know the obvious limitations of aluminum however in this day and age with all the advancements in coatings, treatments, and metalurgy couldnt someone come up with a better lighter material?

Down side
1. possible negative torque effects
2. expensive
3. heat

solutions
1. 3 rotor will make up for the torque
2. deal with it it is not for everyone
3. if you cryo treat them the strength will be there and ceramic coat the outside
the heat should not be that much of a factor.


Any opinions?

 

I think when aluminum gets really hot, it releases a flammable gas or someting... and that's bad for brakes on so many levels.

Seems like two-peice rotors with aluminum hats and steel rotors are the best solution if you can't afford carbon-carbon brakes.

 

frankly, i dont think there would be a signifiant enugh market for it. cost>benefit imo.

edit: we ARE talking about ENGINE rotors right?

 

Wrong rotors Valkyrie

As far as the market goes there isnt a huge market for aluminum plates but racing beat made them.

 

I found think..that under the insanely high temps, and the high speed constant bashing..they would be under a lot of pressure. I would expect the rotors to warp? But meh, if you can get proper coatings on it...


The benefits would be SUPER! The rotating assembly would be lightened a crapload! Teamed with an aluminum flywheel, and aluminum driveshaft...this thing would rev like a motorcycle!!

 

That is exactly what I was thinkinhg I just know there has to be a reason other than expense.

 

i don't know if aluminum could withstand the forces in a combustion engine yet still be lightweight and cool as well. remember the oil in the casting is what cools the rotors, too thick of a casting and it will not be able to disperse heat quickly and aluminum has a low melting point.

 

Thermal expansion of aluminum is ~2x cast Iron. Proper clearancing would be necessary.
It would get very soft with exposure to exhaust gas temps.
Apex seal slot would get pounded to hell fast.
Street? No way
No regard for cost racing? Maybe.

 

cryogenic treating only relieves areas of stress within the metal, it doesn't make the metal "harder". i could see some Al alloys being used if you were crazy and rich enough.

Titanium would be the ultimate rotor material... as far as strength and weight, i don't know about it's heat withstanding abilities.

 

I think the biggest reason why would simply be seals.

Even if you could make the rotor itself strong enough to withstand the heat of combustion for a good period of time, you'd have to change ALL of the material for each and every seal and spring, aside from perhaps the water seals. Othewise, say for example the oil seals, would basically fall out with the high expansion of the aluminum.

You'd have to do years for R&D finding material combinations that could hold together after heat-cycling.....it may be possible, it would just take boat loads of cash, paitence and persistance.

 

Right on the nose. With the expansion of aluminum, the clearances would be too large for a street car. It'd be like forged pistons with high silica content that expand alot, and thus the clearancing makes them slap when cold, though I'd guess it would be even more problematic with a rotary.

 

Mazda made aluminum rotors for their 1985 MX03 3 rotor 4wd 4w steering show car. Car actually functioned setting it apart from so many "concept cars".

They used ceramic inserts for the apex and cornerseal slots, sideseal slots were machined right into the aluminum.

Special compact (compared to 20B production engine) 3 rotor filled w/ aluminum and ceramic parts.




The MX03

 

Why not just make it out of the same material as forged pistons? Those are light and strong right?

 

yeah titanium seems to be the answer it weighs only about 57% as much as the steel we are running. Wall thicknesses and internal gussets could be thinned to shed even more weight since the material is stronger.

 

They expand a lot, too. Most new forgings are made from the same material types as castings, so they are brittle like castings. (Old-style forgings require a lot of clearance, are noisy when "cold", burn a lot of oil... BUT you can beat them with a hammer and they just bend instead of breaking. Kinda like steel)

They also have the benefit of being exposed to combustion temps on only one face, the other faces being exposed to oil or cylinder wall, giving a better avenue for heat transfer.

I would imagine that an aluminum rotor would have to have so much wall thickness that there wouldn't be much oil capacity left. Bad for thermal transfer.

 

Titanium is much weaker than steel for a given volume.

That is not a misprint.

Titanium is much lighter than steel for a given volume, too. It's the strength to weight ratio that is better for titanium than steel.

So basically, you need much more *volume* of titanium for the same strength as steel, but it will weigh less.

 

Y'know... I'm just going to flat out say it since I know noone looking in this thread is going to go to the trouble of stealing my idea.

Metal matrix composites, specificially aluminum reinforced with silicon carbide particles. Duralcan was one of the first of these, but http://www.mc21inc.com/ sells another similar product. It's castable, the coefficient of thermal expansion is about on par with cast iron, tensile strength and elastic modulus are way up there too, and it's machineable and severely wear resistant. You could effectively replace cast iron with it on a 1:1 basis, structurally speaking... which means rather severe weight savings as the density isn't all that much higher than plain aluminum alloys.

Downside is... well, the SiC particles sorta eat machine tools for lunch, so cutting the slots in would be a bitch and a half. Oh, and setting up casting facilities.

 

Rotor weight has absolutely nothing to do with torque,.......


This is extremely doable with modern ceramic coating etc, the only problem is cost,.. The development cost would be insane, and would probably have to go through many prototype failures which would probably take whole motors with them,..

 

Its also Incredibly expensive.

 

Woohoo! I just picked up a new copyright! CJ

 

Uh... not really. I mean sure, more than castable aluminum grades, or iron, but they're practicially free. From poking around some industry newsletters, Duralcan ingots were said to be going for for about $4-5 per pound. We're not talking AlBeMet here.

Yeah, setting up to cast the things is going to add cost that's going to have to be spread out... as is figuring out how to machine the damned things... but how much do lightened stock-based rotor sets go for again?

 

HOld up.....possible, perhaps, but the question is why not,and the reason why not is that it would throw off the weight distribution. lighter fron than rear....rite?

 

Yeah, I just realized I was looking at the wrong forum

 

It wouldn't be hard to drop some weight off the rear, and there's always ballast. Lightened rotors aren't just an overall weight advantage, there's a performance benefit too.

 

... mainly performance benefit. But even leaving that aside... assuming a vehicle lightened to the full extent practical, there's no point to adding ballast to maintain the oft touted 50/50 weight distribution given as how more rearward weight bias is actually preferable.