Material for uprights

[B.A.]

Greetings,

I wanted to know what is the best aluminium alloy to use to manufacture a upright using CNC machining.

Tks in advance,

BA

[Fyhr]

You go find a few datasheets, here's one in swedish that you won't be able to understand: http://www.uddeholm.se/swedish/files/Alumec-swedish_000815.pdf

Take an evening thinking about what sort of material properties you need, consider your operating conditions.

Find a suitable compromise.

murpia wisely wrote in another thread about engines: "Go on, be an engineer, you know you want to...

Engineers analyse problems using the tools of physics, mathematics and common sense. Then they propose solutions for peer review with a series of pros and cons, and a consensus is reached. At least, that was what I was taught in the years before the internet..."

[Chris Allbee]

any annealed 3000 series should do you just fine....with 4 flute cutters...and no coolant...

[Marshall Grice]

I hear wood is a great material for uprights. I'd recommend oak as you want something pretty strong.

[Mike Flitcraft]

I'd suggest walnut over oak http://fsae.com/groupee_common/emoticons/icon_smile.gif

[Steve Yao]

Oh come now Chris, we all know the best upright material is "Rich Mahogany". http://fsae.com/groupee_common/emoticons/icon_wink.gif

[jowen]

I think magnesium would be a great material with its low weight and high stiffness in bending. If you want to use aluminium then 7075 has good machineability but the strength might be overkill of you are dimensioning it for stiffness.

[Jersey Tom]

The stiffness to weight ratio for steel, aluminum, and magnesium are all just about the same.

I'd go with the highest strength aluminum alloy you can find. 7075, 7475, or 7068. You can design it around that and have a very stiff structure with a reasonable FOS of about 1.4.

If you have the right machines and tooling, a billet 4130 upright would be pretty wicked. I wanted to fool around with one but didnt have the time.

[TG]

Originally posted by Jersey Tom:
The stiffness to weight ratio for steel, aluminum, and magnesium are all just about the same.

They would be just about the same in tension... NOT in bending or buckling. Weight normalized equations are:

Tension: W₁/W₂ = ρ₁/ρ₂*σ_t2/σ_t1
Bending: W₁/W₂ = ρ₁/ρ₂*(σ_b2/σ_b1)^(1/2)
Buckling: W₁/W₂ = ρ₁/ρ₂*(E₂/E₁)^(1/3)

If you look at various materials in these equations, titanium *generally* comes out ahead in tension and magnesium *again, generally* is usually ahead in bending and buckling (discounting beryllium alloys). This obviously doesn't account for many other important characteristics that factor into design, but for uprights where the design isn't dominated by the need of airflow for brake cooling, I would have to give the go ahead for magnesium.

[Jersey Tom]

Good point, overlooked that.

I still wouldn't go with magnesium http://fsae.com/groupee_common/emoticons/icon_smile.gif Kinda expensive and hard to come by, and dicey to machine. I worked in and ran a shop 4 years, only machined mag once, and it was at sloooow speed and I was keepin an eye on the thing the whole time.

I think wrought alloy aluminum gives you the best mix of strength, stiffness, availability, price, and machinability. AND your British friends can call it "aluminium." Hard combo to beat.

[TG]

I wouldn't completely discount it for those things. The price of magnesium is becoming more and more reasonable as the price of aluminum keeps on going up. Yes it might slow down your machining, but we are designing race cars here. I will say that you do have to consider corrosion prevention so surface treatment becomes an issue. And I too can't get enough of the aluminium talk, especially from the British car shows on the tele.

I'm looking at using composites in the upright structure: MMC, PMC, and even CMC. From what I've heard aluminum MMC is all the rage in F1 uprights these days, although if you wanted uprights like theirs you would need a heavy investment of PCD tooling. Alternative design can help get around that, but the design would be somewhat compromised, but by how much is for one to determine. Also, molding of PMC's like carbon fiber with co-bonded metal inserts allows for geometric advantages like hollow structures like fabricated uprights with improved accuracy if done correctly and without the hassle of setting up the parts to weld.

[Jersey Tom]

Yes it might slow down your machining, but we are designing race cars here.

We are designing race cars.. student built and manufactured race cars where every day of test time and every dollar is precious. When I redesigned the wheel assembly of our car in 06 and 07, I DFM'd the crap out of it. In 04 and 05 for the machined uprights, it would take upwards of 40 man hours of machine time PER UNIT to fabricate. I got it down to about 1.5. Huuuge savings in tied up manpower.

Yea, MMCs are pretty popular in Champ Car for brake calipers and F1 for uprights, though they also like investment casting them out of Titanium..

http://www.crptechnology.com/sito/images/stories/ElementiFissiHome/materiali/portamozzotitanio_cut01.jpg

Or, EDM out of a solid f'in block!

http://www.moldmakingtechnology.com/mag_images/040508b.jpg

I say if you can get the thing strong and stiff enough out of conventional, commercially available and relatively inexpensive materials, then why use somethin different.

And I'm still a huge fan of CNC billet pieces over weldments. Know the mechanical properties through the part sooo much better. And anything that I can press the "start" button, walk away for a couple hours, and come back to a finished part.. ROCKS.

[TG]

Originally posted by Jersey Tom:
I say if you can get the thing strong and stiff enough out of conventional, commercially available and relatively inexpensive materials, then why use somethin different.

Well, the whole point at looking at alternative materials is to create something better. You can create an entire car out of steel... it's just going to be fairly heavy.

And yes, while those uprights with extreme cutaways will work well, they still aren't as light as they can be, were it not for the need to get airflow through to the brake rotor. It's all about efficiently placing material to where it is most effective.