Python Carbon Fiber or Aluminum

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Definitely metal, so either aluminum or titanium, choice of which (for me) is driven by price.
I tend to steer clear of carbon fibre, as greases/oils, sunlight, water etc can cause the resin to break down. And of course a 'lack of talent' moment can cause delamination, loose fibres into the skin etc. Metal can be smoothed with a file, carbon not so much.
 
What bashing Brian said!

I think it's hard to beat woven carbon fibre for things like chassis plates, shock towers, and pin braces. Obviously, the lay-up for carbon fibre parts is crucial for how well it performs, but assuming it's done right for the job in hand, carbon fibre is extremely light and rigid. When carbon fibre flexes, provided it's not pushed to the point where it de-laminates, it won't stay bent like Alloy.

But - it's less tolerant to chemicals, requires sealing around the edges - including holes and countersinks - is highly conductive (of concern for electrical noise short circuiting) and unlike metals, is anisotropic rather than isotropic. As indicated above, this factoring in at the design stage and then appropriately laid-up.

For gears and transmission, it's hard to beat hardened steel for longevity. To a certain extent, clever machining can mitigate the mass associated with machined steel parts - this is especially relevant for reducing rotating mass on rotating parts.

For hubs, alloy is king. It's light enough (how light depends on how exotic you want to get - magnesium anyone?) and when machined can be more precise than moulded parts, yet lighter than steel so can keep the unsprung weight down.

Moulded composite parts where you need flexibility and/or weak link - something that's easy to replace.
 
KnowAir said:
Aluminum here. I like to make my own skid plates and body mounts from aluminum and Kydex plastic. I've been tempted to try CF but, I do use most of my rc's year round(snow) so.🤷‍♂️
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The only sensible solution is both. Preferably at the same time! 😝

IMG_20230331_195431.jpg
 
Jeffwazz said:
Definitely metal, so either aluminum or titanium, choice of which (for me) is driven by price.
I tend to steer clear of carbon fibre, as greases/oils, sunlight, water etc can cause the resin to break down. And of course a 'lack of talent' moment can cause delamination, loose fibres into the skin etc. Metal can be smoothed with a file, carbon not so much.
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Metal every time. Carbon may look nice but you can’t bend carbon back into shape if you happen to bend it. 7075 T6 will bend and straighten in a vice. Carbon will just snap. If you want it made out of a fancy material, use Titanium. Prices are getting reasonable. I prefer the black look of 7075.
 
chipster said:
Metal every time. Carbon may look nice but you can’t bend carbon back into shape if you happen to bend it. 7075 T6 will bend and straighten in a vice. Carbon will just snap. If you want it made out of a fancy material, use Titanium. Prices are getting reasonable. I prefer the black look of 7075.
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Carbon fibre, depending on the lay-up, can be far more flexible than 'metal' when required. We also need to be much more specific when referring to 'metal'.

The misconceptions around which materials are 'better' are down to the complexities around comparing metals which are isotropic vs carbon fibre which is anisotropic.

However, in relation to bending forces causing permanent bending/deformation, weight for weight, carbon fibre is up to 5 times stronger than 7075 alloy.

Shock towers, chassis, braces when made out of alloy can be bent passed a point where it can bend back.

To do this on proper quasi grade carbon fibre of the same mass, you'd have to apply 5 times more force.

Steel is 5 times stronger than 7075, but is also 5 times heavier.

Carbon fibre could theoretically be used to replace most RC car parts that are made out of 7075, especially those parts which are essentially just CNC machined sheets.

The only reason why this hasn't happened is because basher part manufacturers haven't yet adopted large stocks of pre-preg, skilled laminators to lay-up the parts and (very expensive) autoclaves and moulds.

For the avoidance of any remaining doubt, please see the table below.

Aluminium
Steel
Two-direction carbon fiber – common modulus
Two-direction carbon fiber – improved modulus
Two-direction carbon fiber – highest modulus
Stiffness against weight

(Specific Modulus)
Unit: 10 6 m2s-2		26255683120
Resistance to damage

(Specific Strength)
Unit kN·m/kg		214254392211126
 
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Just to add some real world comparisons.

Here you see a typical alloy plate brace.

IMG_20230316_201932.jpg

This 3mm part is 54g.
IMG_20230316_201843.jpg

The same part in 4mm Quasi grade carbon is 47g (50g with the plastic parts) and greater than 5 times stronger/stiffer.

Unlike the alloy counterpart, there is no fatigue limit either. This means that the part can flex an infinite number of times within it's limit and not suffer fatigue.

The alloy part is not only heavier, it is weaker ie - it's more likely to exceed the elastic limit - a point where it stays bent.

Even when kept within it's limits, all alloy parts that are flexed will suffer fatigue, so effectively have a shelf life, even if they aren't bent 'too far'.

There are parts on a car where you just don't want flex. Pin braces made of carbon fibre with bushes do a far better job than 6061 or 7075. It's irrelevant whether that be on a street racer or a basher - it's just not an area of the car where you'd want it to flex.

And the weight savings soon adds up:

IMG_20230316_211606.jpg

So, in terms of strength/weight advantages, there is only one winner.

The problem is availability.

Machine shops tooled up for 6061 parts are going to prefer that customers believe that Alloy is king.

Strategic use of steel, alloy, composite nylon and carbon fibre - depending on what part you're talking about - is the only way to go on a quality rig.

chipster said:
Really then it’s down to personal preference.
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Alloy parts are just too shiny to say no to. 🤣

Shiny alloy and carbon fibre look lovely together.

But in terms of 'moar better' - the numbers don't lie.
 
That’s great shaving a couple of grams off here and there. Let’s say 25 grams saved changing what you can to carbon. The next improvement that needs to come is lighter better batteries. My 6000mah hard case lipo weighs a great deal. A battery half the weight but more efficient would be a true breakthrough if they were available to the everyday RCer. I have 2 3S lipos that are quite light but only 3000mah combined. Less weight and less time having fun.
As for the Carbon, ok I am convinced but having just spent £350 on the 7075 stuff it will be a while before I swap it all. Hopefully by then more Corally carbon parts will be available in the UK. Mainly it’s just Corally themselves selling them. In time UK suppliers will also get on board.
 
chipster said:
That’s great shaving a couple of grams off here and there. Let’s say 25 grams saved changing what you can to carbon. The next improvement that needs to come is lighter better batteries. My 6000mah hard case lipo weighs a great deal. A battery half the weight but more efficient would be a true breakthrough if they were available to the everyday RCer. I have 2 3S lipos that are quite light but only 3000mah combined. Less weight and less time having fun.
As for the Carbon, ok I am convinced but having just spent £350 on the 7075 stuff it will be a while before I swap it all. Hopefully by then more Corally carbon parts will be available in the UK. Mainly it’s just Corally themselves selling them. In time UK suppliers will also get on board.
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It all depends on the application - as stated above. It's not practical or desirable to make every part out of carbon fibre due to certain limitations.

Below is a helpful summary of real world applications where each material has the advantage, as stated by a producer of light aircraft - DarkAero Inc.

There are likely other factors which aren't listed - please feel free (anyone/everyone) to point out any others that you can think of.

Carbon:

●Compound curves
●Thin parts
●Lower precision tolerances
●2D stresses
●Low - medium temeperatures
●Bonded assemblies
●Non-wear parts
●Weight critical
●Stiffness
●Fatigue critical

Alloy:

●Small, detailed parts
●Thick parts
● Higher precision tolerances
●3D stresses
●High temperatures
●Serviceable, bolted assemblies
●Wear surfaces

So people need to think carefully about what would make their rig better, how does changing from stock parts impact weight, strength, responsiveness and handling?

Is what's best for landing from 40 foot high necessarily what's best for speed/handling? Is it possible to make a rig lighter, stiffer, better handling and more durable?

I believe it is possible, but you can't be of a mindset that concludes 'only carbon' or 'only alloy' is best. You have to intelligently select the right material for the job, knowing what the limitations are. 👍👌
 
in relation to the ongoing debate about the pros and cons of 7075 v Carbon. On the front Chassis brace for the Python and others made from 7075 there is a post about half way along that is threaded. What is this for

74F687EA-E352-4847-95B9-542DFD08C0CE.jpeg
 
chipster said:
in relation to the ongoing debate about the pros and cons of 7075 v Carbon. On the front Chassis brace for the Python and others made from 7075 there is a post about half way along that is threaded. What is this for

View attachment 4192
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It's for a tower brace for the trucks

Screenshot_20230709-055608.png
 
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