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Old 07-12-2003, 11:49 AM   #1
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Default Graphite VS. Aluminium?

whats the big differnces in a graphite chassis and an aluminium one?

pros and cons?

only thing i know is that the aluminiums are alot more...
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Old 07-12-2003, 12:38 PM   #2
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Here are the pros and cons of each.

Alloy Pros -

It keeps all the main weight to the bottom of the car for better CG
It wont break in a hard impact unless the material is really brittle.
It is comparatively cheaper than Carbon
It is better suited to bumpy unprepped tracks

Alloy Cons -

It is heavy compared to Carbon
It doesnt give the best performance handling due to unneccessary flex on smooth permanent tracks.
It will bend in a hard crash and tweak the cars set up (can be un-noticeable by eye until you put the car on a tweak station).

Carbon Pros -

It is lighter
It wont bend in a hard crash
It is stronger if designed right
It gives better handling on a flat smooth permanent track with good grip.

Carbon Cons -

The cost is higher
The chassis retains more heat than an alloy version which hurts the engine (This can be overcome by the correct design of the airholes in the chassis and the correct design of the engine mounts).
It will shatter or at least splinter in a hard crash.
It is too rigid for unprepped permanent tracks.
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Old 07-12-2003, 01:26 PM   #3
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Well said modellor
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Old 07-12-2003, 01:37 PM   #4
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thanks modellor, that really helped.
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Old 07-12-2003, 02:02 PM   #5
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i do now see why anyone would use a carbon fiber chassis on a nitro car

for electric, its fine
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Old 07-12-2003, 02:07 PM   #6
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Quote:
Originally posted by B
i do now see why anyone would use a carbon fiber chassis on a nitro car

for electric, its fine
i don't understand your first sentence...
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Old 07-12-2003, 02:28 PM   #7
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The concept of racing is to have the chassis as stiff as possible as this gives the best handling on a smooth permanent track. Alloy is the best material available that offers good rigidity but there is still an element of flex available for less smooth tracks for the best of all situations.

However, Carbon Fiber has shown to be a better chassis on smoother tracks on Nitro cars due to it being really rigid at 4mm. However, it has not been used much due to it retaining too much heat from the engine which in return hurts the engines performance.

But now we are starting to find ways to use the Carbon Fiber without causing too much overheating in the engine by the design of the holes in the chassis and by the design of the engine mounts. Due to the cost of Carbon Fiber the chassis has to be made in two 2mm halves so that the underside can be replaced much cheaper when it becomes too badly scratched and weakens.
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Old 07-12-2003, 09:33 PM   #8
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oops, i mean "Don't"

well, i do not think that re designed chassis and cooling fins will do that much of a difference in cooling down the engine's heat

we have cooling fins and very tiny air ventilation slots on the alloy chassis and engine mounts already dont we?
and they do not work ........or just a TINY TINY TINY bit


and i would not be surprised if carbon fiber will snap in a 1/8th collision down a straightway

even alloy have snapped....
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Old 07-13-2003, 08:18 AM   #9
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I have to disagree with you B.

The current mounts dont have the correct shape or size fins for extra cooling and as far as heat dispersion, alloy will take the heat away from the engine more letting the engine run cooler whereas Carbon does not do this.

I do agree that a Carbon chassis on a 1/8th will definately snap in a collision but with 200mm you dont have the same distance between mounting blocks so things dont flex the same and the chassis has more support along its entire length.

The majority of holes on most Alloy chassis' are not designed as airholes. They are normally just cut outs to reduce the weight and dont act like efficient airslots. In fact I have only seen 3 chassis' come standard that act like airholes (Trinity Reflex, Kyosho V1RR and STS Pro 10) as they are slanted to allow air to be directed up into the case of the engine. But again these are only doing a little bit of work and the holes are not completely effective due to the location and design.

The Carbon chassis' were originally designed with the Lola/GTP shell in mind as the engine sticks through the shell and gets enough cooling from airflow over the shell to reduce the heat levels. This is the main reason the Carbon has not been offered for these cars yet as most people run TC shells still that retain more heat around the engine.
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Old 07-13-2003, 10:16 AM   #10
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so what chassis would your recommend for the NTC3?
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Old 07-13-2003, 10:29 AM   #11
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There are several NTC3 chassis' available on the market. If you have the money to spend you could get the chassis from BMI. It is $170 I believe.

Or if you want something cheaper but a lot better than the stock chassis then for $40 you could get the MPP chassis. This is 4mm and really stiffens up the chassis to reduce chance of stripping the gears as much.
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Old 07-13-2003, 10:47 AM   #12
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Quote:
Originally posted by modellor
The concept of racing is to have the chassis as stiff as possible as this gives the best handling on a smooth permanent track. Alloy is the best material available that offers good rigidity but there is still an element of flex available for less smooth tracks for the best of all situations.

However, Carbon Fiber has shown to be a better chassis on smoother tracks on Nitro cars due to it being really rigid at 4mm. However, it has not been used much due to it retaining too much heat from the engine which in return hurts the engines performance.

But now we are starting to find ways to use the Carbon Fiber without causing too much overheating in the engine by the design of the holes in the chassis and by the design of the engine mounts. Due to the cost of Carbon Fiber the chassis has to be made in two 2mm halves so that the underside can be replaced much cheaper when it becomes too badly scratched and weakens.
Hmmm . . not sure about this.
As I understand it, the object of the exercise in chassis design is for absolute rigidity, any flex being an uncontrolled variable and therefore to be avoided.
With a theoretically rigid chassis, any track conditions can then be accommodated with suspension settings - i.e. we don't need uncontrolled variables influencing these settings.
Sorry, that was a bit pedantic, I guess - in real life we always get some chassis flex.

Iíve often thought, if we could overcome the undesirable thermal dissipation properties of carbon fibre in a nitro car chassis, a square tube section, closed at both ends, could work very well - a bit like current F1 technology.
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Old 07-13-2003, 11:00 AM   #13
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Quote:
Originally posted by modellor
There are several NTC3 chassis' available on the market. If you have the money to spend you could get the chassis from BMI. It is $170 I believe.

Or if you want something cheaper but a lot better than the stock chassis then for $40 you could get the MPP chassis. This is 4mm and really stiffens up the chassis to reduce chance of stripping the gears as much.
ive heard about the BMI chassis, and im going to have to check it out ( they have them at the local track) ive hard good things about the GH (golden horzions) chassis, any good?
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Old 07-13-2003, 11:01 AM   #14
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Quote:
Originally posted by Taylor-Racing
Hmmm . . not sure about this.
As I understand it, the object of the exercise in chassis design is for absolute rigidity, any flex being an uncontrolled variable and therefore to be avoided.
With a theoretically rigid chassis, any track conditions can then be accommodated with suspension settings - i.e. we don't need uncontrolled variables influencing these settings.
Sorry, that was a bit pedantic, I guess - in real life we always get some chassis flex.

Iíve often thought, if we could overcome the undesirable thermal dissipation properties of carbon fibre in a nitro car chassis, a square tube section, closed at both ends, could work very well - a bit like current F1 technology.
I agree with you. But is this not what I just said.

Quote:
The concept of racing is to have the chassis as stiff as possible as this gives the best handling on a smooth permanent track.
But using just the springs to compensate for bumps on some tracks is not enough as the softer springs will allow the car to bottom out and in effect reduce the overall grip and handling of the car in corners. For this reason we allow chassis flex to absorb some of the bumps (like on the first cars with no suspension - the secret is knowing where and how much flex to build in) so that harder springs can be used for better cornering ability along with softer tires.
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Old 07-13-2003, 12:32 PM   #15
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Quote:
Originally posted by modellor
I agree with you. But is this not what I just said.

But using just the springs to compensate for bumps on some tracks is not enough as the softer springs will allow the car to bottom out and in effect reduce the overall grip and handling of the car in corners. For this reason we allow chassis flex to absorb some of the bumps (like on the first cars with no suspension - the secret is knowing where and how much flex to build in) so that harder springs can be used for better cornering ability along with softer tires.
Understood, but the differences we are talking about here, is that any chassis flex is uncontrolled and therefore must be considered in addition to any suspension settings made.

In your first example (to compensate for bumps), I'm imagining a car moving along a flat track and then encountering a bump.
I'd think it is likely that the flexible chassis will hit the ground first - since it will be bending in the middle, presumeably. There is no damper on the chassis. I say the remedy is in springs and damping - something you can control.

In your second example (the first cars with no suspension), while the environment is somewhat more controlled, the situation is still the same. In these cars (and I'm not familiar with them), the tyres essentially are the suspension - a bit like current F1 cars.

In either of these cases, we must remember that there is only a finite amount of grip available. You can't suddenly find some extra grip because the chassis moved as opposed to the spring. In fact you can move the tyre to the track with a spring much faster than by moving the whole chassis. The vast differences between sprung and unsprung weight is the primary reason we have suspension systems, surely.

When you talk about building in some chassis flex, the ramifications can be extremely difficult to control.
For instance:
Can the flex can be limited to a single plane?
Can you permit single plane flexing and at the same time maintain torsional rigity?
Can you control squat and dive at either end of this chassis (the wave effect) together with their interactions?
Since the chassis is acting as a spring, how do you damp it?

Generally, Im saying that, idealy, any suspension settings made must be performed on a stable platform - any flex in that platform must diminish the relevance and effectivness of those settings as it is uncontrolled and largely uncontrolable.
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