GEN 2 will there be a carbon-fiber driveshaft available?

[Vash]

I would think the strength argument of aluminum vs steel would only hold true for shafts of the same diameter and wall thickness. Most applications that I've see where either steel or aluminum is an option will use a thicker shaft for the aluminum option.

Also, the thinner steel driveshafts can potentially have a whip or jump rope effect at the middle of the shaft depending on length and due to the increased energy required to keep the shaft spinning. This can cause added vibration.

 

[crash457]

it's not added weight to the overall vehicle that the benefit comes from, it's the reduction of spinning mass that improves overall mileage, performance...

somewhat like a lighter flywheel in a manual transmission vehicle...

Again with a 400hp 600ft/lbs diesel, not much of an impact on performance. The engine already has alot of rotaribg mass. I have bent aluminum driveshafts off road and had to limp home on fwd. I have beat the hell out steel driveshafts with only scratches. Now in a street vehicle, it makes sense to reduce weight (sprung and unsprung, rotating abd stationary). But for a truck that will go off road, no thanks.

 

[Toadster]

Again with a 400hp 600ft/lbs diesel, not much of an impact on performance. The engine already has alot of rotaribg mass. I have bent aluminum driveshafts off road and had to limp home on fwd. I have beat the hell out steel driveshafts with only scratches. Now in a street vehicle, it makes sense to reduce weight (sprung and unsprung, rotating abd stationary). But for a truck that will go off road, no thanks.

agreed - this is for a street truck, not an offroader...

 

[Ruger]

I've never heard of a failed aluminum driveshaft without 1000 Hp and a drag strip being involved, so - not worried.

That's street thinking, bud. Remember, these are off-road vehicles.

 

[EricM]

I've never heard of anyone breaking an aluminum driveshaft off road either. I'm sure people do at the time, but not around here. There's no desert to do 120 MPH through, and no huge boulders to rip up your drive train either. Given I'm in the rust belt, I prefer my aluminum driveshaft despite it's potential to fail compared to steel. No rusty, nasty BS to deal with when doing u-joints.

 

[Vash]

It's also worth considering there doesn't even appear to be a steel driveshaft option for anything beyond supercab wheelbase length. In that case, the "which is better" argument is moot unless you do own a Supercab.

 

[2011SuperCrew]

call me crazy, but the high-revving EcoBoost V6 TT may have some great benefit from a carbon-fiber driveshaft...



any thoughts? crazy?



Carbon Fiber 1350 Driveshafts

Um, not sure if you realize this, but driveshaft rotational speed is determined by the rear-axle ratio. Engine speed has NOTHING to do with it. In this case, the rear end of the Raptor has a same 4:10 ratio as before, so driveshaft RPM remains unchanged.

I'd ALSO add that the EcoBoost doesn't rev very high. Chances are most folks will average a LOWER engine RPM due to the huge increase in low-end torque.

Given all these facts, a CF driveshaft will make almost no difference. Your money is better spend on lighter wheels/tires or lights.




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[Toadster]

Um, not sure if you realize this, but driveshaft rotational speed is determined by the rear-axle ratio. Engine speed has NOTHING to do with it. In this case, the rear end of the Raptor has a same 4:10 ratio as before, so driveshaft RPM remains unchanged.

I'd ALSO add that the EcoBoost doesn't rev very high. Chances are most folks will average a LOWER engine RPM due to the huge increase in low-end torque.

Given all these facts, a CF driveshaft will make almost no difference. Your money is better spend on lighter wheels/tires or lights.


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Because the driveshaft is a rotating mass, a lighter driveshaft results in less rotating mass (much like your choice to go with wheel/tire combos are are lighter - this all allows for slightly greater acceleration.

Secondly, aluminum does a better job at vibration dampening, thus allowing for a smoother ride at all speeds, but particularly so at higher speeds.

Aftermarket aluminum driveshafts can be stronger than their steel counterpart, but stiffer too, meaning more efficient transfer of power to the wheels. But if you're traversing rocks, bendability needs to be taken into consideration...

To summarize:

Less weight = less rotating mass; less rotating mass = greater acceleration
Stronger: can handle more power
Stiffer: can better transfer power
Smoother: less vibration and noise

Carbon fiber driveshafts offer all the same advantages as an aluminum driveshaft, but to an even greater extent. An aftermarket carbon fiber driveshaft is lighter, stronger and stiffer than aluminum, but also more costly!

 

[DrippinRaptor]

that's street thinking, bud. Remember, only a few of these will ever be off-road vehicles.

ftfy.

 

[StrikerHawk]

Because the driveshaft is a rotating mass, a lighter driveshaft results in less rotating mass (much like your choice to go with wheel/tire combos are are lighter - this all allows for slightly greater acceleration.

Secondly, aluminum does a better job at vibration dampening, thus allowing for a smoother ride at all speeds, but particularly so at higher speeds.

Aftermarket aluminum driveshafts can be stronger than their steel counterpart, but stiffer too, meaning more efficient transfer of power to the wheels. But if you're traversing rocks, bendability needs to be taken into consideration...

To summarize:

Less weight = less rotating mass; less rotating mass = greater acceleration
Stronger: can handle more power
Stiffer: can better transfer power
Smoother: less vibration and noise

Carbon fiber driveshafts offer all the same advantages as an aluminum driveshaft, but to an even greater extent. An aftermarket carbon fiber driveshaft is lighter, stronger and stiffer than aluminum, but also more costly!

Structures isn't my specialty, but I beg to differ...

Less weight = less rotating mass; less rotating mass = greater acceleration - CONDITIONALLY TRUE (see below)
Stronger: can handle more power - FALSE (see below)
Stiffer: can better transfer power - CONDITIONALLY TRUE (see below)
Smoother: less vibration and noise - CONDITIONALLY FALSE (see below)

Citing Metallic Materials Properties Development and Standardization (DOT/FAA/AR-MMPDS-01), the replacement for DEPARTMENT OF DEFENSE HANDBOOK, METALLIC MATERIALS AND ELEMENTS FOR AEROSPACE VEHICLE STRUCTURES (MIL-HDBK-5J)...

4130 Low Strength Carbon Steel (perhaps the most common steel)
Table 2.3.1.0(c2), Tubing (AMS-T-6736)
Strength, Tension, Ultimate = 180 ksi
Strength, Tension, Yield = 165 ksi
Strength, Bearing, Ultimate = 342 ksi (e/D = 2.0), 277 ksi (e/D = 1.5)
Strength, Bearing, Yield = 284 (e/D = 2.0), 257 ksi (e/D = 1.5)
Elongation, e = 8-10%
Modulus of Elasticity, E = 29x10^3 ksi
Modulus of Rigidity, G = 11.0x10^3
Poisson's Ratio, u = 0.32
Density = 0.283 lb/in^3

9Ni-4Co-0.03C High Strength "Chromoly"
Table 2.4.3.0(b), Bar, forging and tubing
Strength, Tension, Ultimate = 220 ksi
Strength, Tension, Yield = 190 ksi
Strength, Bearing, Ultimate = 440 ksi (e/D = 2.0), 346 ksi (e/D = 1.5)
Strength, Bearing, Yield = 322 (e/D = 2.0), 291 ksi (e/D = 1.5)
Elongation, e = 10%
Modulus of Elasticity, E = 28.5x10^3 ksi
Modulus of Rigidity, G = Not Provided
Poisson's Ratio, u = Not Provided
Density = 0.28 lb/in^3

6061-T6 Aluminum
Table 3.6.2.0(c1), Drawn Tube
Strength, Tension, Ultimate = 42 ksi
Strength, Tension, Yield = 35 ksi
Strength, Bearing, Ultimate = 88 ksi (e/D = 2.0), 67 ksi (e/D = 1.5)
Strength, Bearing, Yield = 56 (e/D = 2.0), 49 ksi (e/D = 1.5)
Elongation, e = 10-14% (depending upon wall thickness)
Modulus of Elasticity, E = 9.9x10^3 ksi
Modulus of Rigidity, G = 3.8x10^3 ksi
Poisson's Ratio, u = 0.33
Density = 0.098 lb/in^3

With these numbers in hand...

1. Less Weight - Conditionally True
This answer is directly coupled to the answer regarding Strength below.

2. Stronger - Not even close
An Aluminum driveshaft will NEVER be as strong as even a low-grade Steel driveshaft if they have the same diameter and wall thickness. Both strength and inertial properties are functions of both the material properties and the geometry. For an Aluminum driveshaft to be as strong as a steel driveshaft, it must either be larger in diameter or have a larger wall thickness, likely both for an optimal solution. It may still be lighter overall despite this additional volume due to a considerably lower density.
I suspect that driveshaft design focuses on achieving an outer diameter and wall thickness that provides the strength required for the application and whatever the inertial properties are, they are. Minimizing overall weight would also be an important design consideration I'm sure, thus inherently minimizing inertial properties as an unintended benefit.

3. Stiffer - Conditionally true
While aluminum does technically have a lower Young's Modulus (Modulus of Elasticity), meaning it deforms less under similar loads than a higher Modulus of Elasticity material, I'm not sure this becomes a real issue unless the driveshaft is damaged to the point of being knocked out of balance and/or alignment.

4. Smoother - No material difference here
The smoothness you're referring too comes down to balance of the driveshaft. Both steel and aluminum can be cast, or in our case, drawn, over a mandrel and held to very tight tolerances. Final machining of both can improve on this final balance even more. Thus, smoothness is simply a function of balancing at the end of the production cycle to ensure that other features of the driveshaft design haven't introduced some a-symmetric trait.

Respectfully,