brake disc material

[Ajay]

wht material to use for manufacturing brake disc
420/250 series stainless steel
Al 400 series
Al 6061
plz suggest

is their any problem in conventional drilling of holes
what manufacturing process would be best for drilling holes in disc

[Greg Holden]

Ajay,

That's a pretty open ended set of questions. Here are some for you to answer first:

1. How many disks are you using?
2. What size wheels are you using?
3. How much does your chassis weigh?
4. What calipers are you using?
5. Are you using floating rotors or calipers?

You might want to figure some of those out before you worry about the type of material you use.

As far as drilling rotors, we do it on the CNC. But do you know the reason why people do it?

You may find your answer by simply searching the forums for brake rotors. This topic has been discussed in length before.

[Jersey Tom]

what manufacturing process would be best for drilling holes in disc

Drilling is usually a good process for drilling holes. For holemaking and disc making in general I reccomend waterjet.

If you use aluminum rotors you're going to have to use fancier pads I'd imagine, or some real thick surface treatment.

We use waterjetted HRS discs. Cheap as hell, works great.

[SNasello]

in terms of which material to use, you need to answer all of the questions in the above post to determine what kind of forces you are looking at under maximum braking (with a safety factor included) and then look at material properties. Also consider thermal properties.

[Vinnie]

we use custom made floating discs; the disc is made out of steel ST50 (don't know the american notation of it) the float buttons are made out of al 7075-t6 and the carrier is made out of al 2024-t6

the MIL-handbook gives a good description on the good and bad properties of many materials. The thermal and fatigue* (*depends on how much testing you think you gonna do) properties are the most important ones for the centre of the disc, for the rotor you also have to look at the hardness of the material

vinnie

[Travis Garrison]

Why stainless steel or aluminum? Mild steel can work just fine.

If you really want to go aluminum off the top of my head I'd guess either 2024 or 7050 series would be the grade that can handle heat. I believe that to do it correctly you'll want to do a plasma spray coating (I think cu based).

The other aluminum option is a SiC reinforced metal matrix composite of some kind. There are a few companies that make these already you might try talking them.

Straight uncoated aluminum however could be very risky (loads up conventional break pads) and most likely will be something you have to go to great lengths to defend in the design tent...your time could probably be better spent elsewhere.

Personaly, I would waterjet some mild steel rotors and be done with it. Machining works fine, but it can be time consuming for such a simple flat piece of metal. Put some effort into making them as thin as possible and you'll save a little weight and get your brake temps into the correct range for most pads.

[LU-Bolton]

Ajay,
I would advise against the use of aluminum for your discs. Take a look at a chart which plots yield strength versus temperature of the three common aluminum alloys we use. 2024, 7075, 6061. You will find that shortly after 200 degrees F, all three alloys lose strength drastically. I'm telling you that once you get your rotors up to temperature on the track, you might as well have made the rotors out of some garbage aluminum stock you found on the side of the street. Our rotors are seeing temperatures well above 200 degrees F. To prove it, you would have to do a finite element model of your aluminum disks with some strength values which take into account the heat they will see. My guess is that a disk even 0.250"(6-7mm) thick made from aircraft grade aluminum will not hold up.

To save on unsprung weight, buy lighter calipers, use lighter wheel bearings, shave some rubber off your tires, lathe some material off your aluminum rims.... just don't use aluminum rotors. http://fsae.com/groupee_common/emoticons/icon_wink.gif

Aaron Cassebeer

[Jersey Tom]

I'll throw in there that 2124 has much better strength retention at temperature than the other high strength alloys, IIRC.

[Travis Garrison]

Aluminum rotors can and have been done with at least a degree of success. And if you're willing to get a little trick they can be very good:

http://www.swancomposites.com/

For fsae though, I would agree aluminum is probably not worth the effort.

[conekilr]

We have been using aluminum metal matrix composite rotors for the past two years. One of the sliding calipers on the '05 car didn't "agree" with the MMC rotor and ate the (insert 4 letter word) out of it. So that car was fitted with steel late in its year. The '06 brakes are much improved however and have performed near flawlessly throughout the autocross season, FSAE East and West, and UTA weekend where we were braking hard from ~90 mph in the texas heat.

There seems to be more concerns with the aluminum MMC though, mostly because it can't handle as much heat as steel and will expand a surprising amount during long sessions like endurance. In our case the front disks expanded so much on one occasion that they were "machined" by near by tie rod bolts; design oversight you could say. Also, it's a bitch to get regular brake pads, machine the material off, send them away to have the proper material applied, and then wait for them to be returned.

Despite the expanding issue and being able to smell the MMC sometimes during hard driving I believe that the material has been a success. Based on our work a well designed MMC rotor is a pinch lighter than a well designed steel rotor. But that's a pinch lighter rotating and unsprung at each corner I guess. However I also think that the aluminum has been a bit of a pain in our backs at times and more complicated. This is just my not-so-technical opinion based some experiences.

*Oh ya, ductile iron is another possibility.*

[kwancho]

Jared, are these the rotors?
http://img295.imageshack.us/img295/1082/img0323wo3.th.jpg (http://img295.imageshack.us/my.php?image=img0323wo3.jpg) (click for bigger pic)
Did you make them or buy them? Also, out of curiosity, what bike is that caliper off of?

[NetKev92]

Stoptech speaks very highly of cast iron rotors although they may or may not have played with aluminum. Several of the papers are good.

http://www.stoptech.com/tech_info/tech_white_papers.shtml

For FSAE autocross, you can probably get away with a lot less braking capacity than track events. That kinetic energy really builds up with increased speed.

[conekilr]

Alex,

Ya those are the fronts of the '06. The rotors were manufactured by an outside source and I believe the calipers are from a Suzuki GSX-R.