Originally Posted by
the incubus
7075 and 6061 are different grades of aluminum and makes no reference to thickness and any allow can be made to any specs. T6 (6061)used to be the best and 7075 eclipses it by a bit but for all intents and purposes, for RC no one would know the difference really. The biggest difference is in the weld-ability between them. 6061 is easier to weld but 7075 is touch stronger.
If you look at most RC chassis, they have 1 of 2 things, and some have both…
angled sides or side plates in order to make the chassis rigid and exile less flex. Those that have both are even more rigid.
Concepts claim that their honeycomb chassis is stronger is predicated on the honeycomb design, but if you know in what way honeycomb is strong, you would know this claim is untrue. Honeycomb does not add strength or rigidity in the way the JC chassis features them. It does look kickass, but the other thing one has to realize is that the way it is done, the aluminum being milled out like that means it is unprotected from the elements and will eventually oxidize. This is an off-road car so probably not a big deal, but it is something I figured I'd mention just to be thorough. At the very least, JC should seal with clear ano.
Personally, I'd prefer a CF chassis so I could fine tune overall balance and weight bias myself.
How many hours did you spend running a 3mm thick 7075 chassis versus a 2.5mm thick 6061 chassis? I peg my testing time at 45 hours.
I would like to have an idea on your experience, before I take your claim that I'm wrong as fact. I have lap times, and back to back experience to go with my claim. I also have material science to tell me the differences are much much more than, "just different to weld with" like you say.
Here's some chart data on 6061 T6:
http://asm.matweb.com/search/Specifi...ssnum=MA6061t6
Easier to read:
6061 – Mechanical Properties
Ultimate Tensile Strength 45000 psi
Tensile Yield Strength 40000 psi
Fatigue Strength 14000 psi
Shear Strength 30000 psi
Hardness, Rockwell 40
Machinability 50%
7075 – Mechanical Properties
Ultimate Tensile Strength 83000 psi
Tensile Yield Strength 73000 psi
Fatigue Strength 23000 psi
Shear Strength 48000 psi
Hardness, Rockwell 53.5
Machinability 70%
And for 7075 T6:
http://asm.matweb.com/search/Specifi...ssnum=MA7075T6
Please, feel free to tell me, AND the ASM material data minds they're wrong - they're only required by law to make these numbers public. This is material used on a very light weight, overly sensitive 1/10th scale car. The rigidity of the chassis, with even a 3% change in stiffness can have a huge effect.
Oh, I also tested with the Xfactory chassis - it's really good...when you make it stiffer than box setup. Hence why they came out with the optional side plates.