14 replies to this topic

[Jhope]

I just finished reading a nice piece on the evolution of suspension uprights. From the time they were being made of steel, to the introduction of titanium, then hot wire cut titanium, to new titanium machining possibilities in the 90's. Titanium uprights were the norm in Formula One until Ferrari introduced Aluminum Matrix (AMC) units on all four corners during the 2002 Belgian GP. The increase in stiffness was not known at the time of the atricles publication. What shocked me was the weight saving involved. The old titanium uprights weighed in at 1.1Kg's. With the new AMC uprights, there was a weight savings of roughly 20% (900g).

Does anyone have any information on

1- the evolution of uprights in racing applications.
2- the importance of uprights in racing.
3- the use of AMC in other areas of the racing vehicle.
4- the perfromance v. cost of aluminum matrix.
5- the benifits of AMC(stiffness).
6- the manufacturing processes involved.
7- the use of AMC in Formula One and other high end racing series.


Most of the information I have searched for online leads me to commercial sites with no real educational material. So if anyone can point me in the right direction, I'd be greatful.

Oh, and I'm no engineer (son of one) or scientist. I'm just Joe Blow interested in somehting I find facinating.

[dosco]

Here is a link to the material properties: http://www.matweb.co...?bassnum=NAMC20

Cost? I dunno. Probably more than Ti, depending on the type of MMC (when on MatWeb, you can goto the home page and search for "nonmetallics" and find some more Aluminum MMCs......there are several types/"flavors").

I think the FIA has pretty much banned MMCs from pistons, crankshafts, engine blocks, wheels, and brake calipers. Put the stuff wherever else you want.

The importance of uprights? What do you mean? They're like important to keep the wheels attached to the suspension (and all the stuff associated with wheels, brakes, and suspension)....... what else do you want to know?

Hm. Manufacturing......I guess you could machine the stuff fairly easily. Cutting tool insert material and geometry could present issues, but I think that has already been worked out. I'm not sure if you can effectively weld the stuff, but I wouldn't rule it out. I'd imagine EDM (electric discharge machining) (wire, ram, etc) is also possible. If you can't weld it, you could probably hog-out a chunk of the stuff using various machining processes (lathe, mill, EDM) to get the shape you need.

[MRC]

Machining of Al-MMC's would be considered as far from easy as you can imagine. Waterjetting it is easy, but anything else requires expensive tools. Think about it, you are basically machining a chunk of aluminum with bits of stuff in that's basically like grinding wheel dust. Al-MMC's will destroy common tooling, including uncoated TiC tools. Look on the internet, as there is plenty of info on machining Al-MMC's. One company is doing a DLC coated TiC tool that outperforms some other coated TiC tools by a large marging.

I know that you can get some Al-MMC 20-25%SiC plate for around $80 a pound.

[CFD Dude]

The company my brother used to work for dealt a lot with MMC material, and depending on what was mixed into the aluminum (usually silicon carbide, but sometimes aluminum oxide and I think there were a few others) it wasn't insanely expensive. The problem came when trying to do anything with the parts after casting (which is also a pain 'cause the stuff likes to make bubbles... www.cymat.com). Like MRC said, it's incredibility hard to machine. You need special tools 'cause it'll dull any normal bit or blade in no time.

I'm surpised that Ferrari was the first to try this. I thought that BAR had been using MMC uprights for several years. Maybe they weren't using them on all four corners?

[Greg Locock]

Upright stiffness has a MEASURABLE effect on camber control and lateral compliance, at least on SLA type suspensions, where the upright (spindle) tends to be twice as tall as on an F1 car.

So correct design is important. Having said that it would act like a linear spring, so it is fairly easy to compensate for it. I suspect that in F1 they design for strength rather than stiffness on that component, and eat the compliance effects (The switching from steel to Ti or MMC would encourage this view)

[CFD Dude]

You're probably right. So long as the upright is stiff enough that it can hold everything together without fatiguing and it isn't eating bearings it's done it's job.

[hydra]

Jhope, what are the odds of you scanning/sharing this document with the rest of us? If anything we can put it in the tech documents section for future reference.

Also, what kind of bending stiffness can one expect from an automotive upright Greg? A ballpark figure would be most useful...

Finally as an aside, are there any other commercial suppliers of MMC brake discs besides Tar-Ox? An extensive google search has shown me that the "species" as a whole is all but extinct

[Jhope]

Alright. Let me get access to a scanner and I'll do it.

[desmo]

Originally posted by dosco


I think the FIA has pretty much banned MMCs from pistons, crankshafts, engine blocks, wheels, and brake calipers. Put the stuff wherever else you want.

I can't recall anything in the rules that would prohibit MMCs for blocks, pistons or calipers, specific modulus limits aside.

[scarbs]

Upright development could a classic example of materials and simulations driving design. Upright stiffness is as critical as with any other load bearing chassis component, i.e. critical. Additionally uprights provide a stiff mounting point for the brake callipers which if designed correctly will make the brake stiffer despite the limitation on only using two fasteners, hence a good upright will also improve braking (plus brake cooling mentioned later on).
You seem to have picked up the story up to the point where technology is so new the teams won’t talk about it. Aside from the cast Ti upright popular since around 2000 and remains so even now, MMC is the next step. Ferrari, BAR, Toyota and recently McLaren have adopted this material. MMC is not specifically banned for use in chassis components, but must not exceed the regulated maximum stiffness (40Gpa IIRC..?). Using MMCs means the teams can tailor the material right up to the stiffness limit. The stiffnessweight ratio is probably well documented by MMC suppliers, but other benefits are the mouldingcasting (which is the right term?) using similar rapid prototyping techniques to Cast Ti that allow fine tolerances and wall thicknesses, also this work can be reliably sub-contracted and hence does not clog their fabricators production schedules with making uprights. While the material cost is probably higher than that of other materials, the investment casting techniques are cost effective and relate well to long hours of fabricators time. However the downside is that MMC is tough to machine, requiring special diamond tipped tools and cannot be welded. As the teams are unable to make the usual vane mounted bearing carrier, the teams have adopted a different fundamental design in getting cooling air to the brake, instead of passing through the vane sin the upright, the upright is waisted and air passes around it through a carbon duct into the brake.
MMCs are used elsewhere on the chassis from suspension rockers, Callipers, wishbone inserts (not flexures) and other inserts into carbon mouldings. MMC gets chosen for either its stiffnessweight or for its thermal expansion properties (i.e. in carbon inserts). I am not aware of other racing series that have adopted MMC either due to rules or the costbenefits involved.

[david_martin]

Originally posted by scarbs
MMC is not specifically banned for use in chassis components, but must not exceed the regulated maximum stiffness (40Gpa IIRC..?)

Its a specific elastic modulus limit of 40 GPa/cc - within that limitation the stiffness is unlimited. The only specifically banned chassis material is magnesium sheet < 3mm in thickness.

[scarbs]

Perhaps Golfball could expand on the some of the finer points of MMC use in F1....? C'mon Geoff told me where you use it..?

[Greg Locock]

It is probably worth developing your own guidelines for component stiffness, but if I run through the basics for camber you can apply the same thinking elsewhere.

Lateral force at the CP = Fy. (200 kg*4g*9.81)

Rolling radius =R (.4 m)

Moment at stub axle = Fy*R

At max latacc we probably want to limit the camber error to 0.2 degrees (this should be done as part of a budget, but that would be a place to start)

so the desired rotational stiffness of the spindle is something like 200*40*.4 /(1/300), or 900 kNm/radian. (This sounds about right)

In context, it is very hard to design rose joints and their mountings to exceed 30 kN/mm, so you can start to build up a budget including these and the arm stiffnesses. Just using the rose joints, there are effectively 1.5 per wishbone, to give an overall compliance for each wishbone of 20 kN/mm, excluding arm stiffnesses. If the spindle is 0.3 m tall then the rose joints alone will give a camber stiffness of about 90 kN m/radian, so that WAG was in roughly the right ballpark, or I've screwed up my maths, or both. FWIW that sounds a bit /too/ flexible - I can't believe a 2 degree camber error due to body mounting point compliance etc. Oh well, find the error then you'll know how to work it out properly.

As I said before, you can compensate for these compliances by moving the hardpoints, but it is much nicer not to have to.

You could put the camber compliance limit into context by looking at the camber changes due to tyre deflection, and making some sort of guess about which is more important.

Incidentally this stuff is measurable. You apply forces at the contact patch, and can measure the resulting joint deflections using some fancy pants laser thingo. This gives a breakdown of the contribution /by component/. Then the real fun starts.

[hydra]

So... Any luck scanning the article?

[Jhope]

Funny you mention that...Monday evening. I was having minor scanner issues. But it will all be yours. No worries.