Carbon Fiber Driveshaft coming soon!

Jamal Hameedi stated they couldn't find a Carbon fiber driveshaft that was stiff enough. So is it possible that it may have negative effects with the operation of the dual mass flywheel?

Epiphany said:

Certainly. The reduced rotational mass and elimination of the center joint allows for faster acceleration over that of a steel driveshaft(s) or aluminum driveshaft. CF shafts are easier on the driveline as they twist and then return to their original state, reducing dynamic "shock" under certain circumstances. In essence, their NVH qualities are much better than that of steel. CF shafts also have much higher critical speeds, the point at which a shaft can bend or whip.

There is a certain "smoothness" to a well done CF shaft that you won't feel in a steel or aluminum shaft, especially in the upper rpm ranges, which is exactly where the GT350 wants to be. Much like the Cf wheels on the R model, a CF driveshaft has the potential to offer a substantial weight reduction, an increase in driveline durability, as well as smoother driveline altogether. As I mentioned, if DSS can come up with a stiff enough design that is robust enough to live behind the high winding 5.2 (and its inherent vibratory potential) it'll definitely be a part worth taking advantage of.

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I think these are generally the same things echoed by any vendor selling them and, so far, the opinions I have seen from buyers are pretty split between people who say they made a huge difference and people who wish they would have spent their money elsewhere. This is one of those mods that is hard to prove is beneficial - but I keep looking for reasons to justify it...because carbon fiber

From a weight perspective alone, I would probably consider it. There is no correlation between RPM of the engine and the smoothness of the driveshaft, however. The speed of the driveshaft is linear to the speed of the rear axle.

I don't buy the "reduced rotational mass" argument for a CF driveshaft. While not untrue, because the weight reduction is so close to the axis of rotation the change in inertial moment is tiny, tiny, tiny.

Compare that to a lightweight flywheel which has a very large radius and where small reductions in mass make a very large impact in inertial moment.

And remember, the driveshaft and flywheel are operating as one big connected system when the clutch is engaged. The overall inertial moment of the rotating mass between the front engine pulley and the rear differential yoke is calculated as one system. Reducing weight an inch or two from the axis of rotation just won't amount to much at all.

You want to save weigh? Great. A CF driveshaft will do that. You want the engine to rev faster? Get a lightweight flywheel.



Sent using the protocol module of my R2 unit.

Spacebird is right, a modification like lighter wheels and tires, or flywheel would likely affect rotating mass more than the CF driveshaft. It would be interesting to see the actual difference in moments of inertia of the stock and CF driveshafts though.

The engine RPM also doesn't have any effect on the driveshaft, other than its driving it through the trans. Driveshaft RPM is only dependent on vehicle speed or wheel RPM. 60 mph at 7500 RPM is the same as 60 mph at 2500 RPM to the driveshaft. So that doesnt seem like a likely reason to not use it, unless the 3.73 final drive ratio created an issue. However, vibrations due to the FPC may have been a reason the CF wasn't stiff enough. Even with all the dampers on the drivetrain, the vibrations from the crank may have been more than the CF shaft could withstand reliably.

this is great! i am interested to see all the mods that members on these boards do but and when i think i might want to do the same i just think back to all that jamal talked about leading up to this car. the choices made were not only for cost cutting but mainly engineered to work together.


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stanglife said:

There is no correlation between RPM of the engine and the smoothness of the driveshaft, however. The speed of the driveshaft is linear to the speed of the rear axle.

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Spacebird said:

I don't buy the "reduced rotational mass" argument for a CF driveshaft. While not untrue, because the weight reduction is so close to the axis of rotation the change in inertial moment is tiny, tiny, tiny.

Compare that to a lightweight flywheel which has a very large radius and where small reductions in mass make a very large impact in inertial moment.

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Reducing rotational inertia is very important on an engine that revs over 8,000 rpm (nobody is arguing that the driveshaft has no direct relationship to axle speed). Don't take my word for it but rather that of Ford Powertrain engineer, Jeff Albers (see comments under "dual-mass flywheel").





You can argue that the inertial moment between a flywheel and a driveshaft has a fairly substantial delta - I agree. But there are gains to be made via a CF shaft nonetheless. In the context of a completely engineered system, every bit counts.

65Terdlingua said:

However, vibrations due to the FPC may have been a reason the CF wasn't stiff enough. Even with all the dampers on the drivetrain, the vibrations from the crank may have been more than the CF shaft could withstand reliably.

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You're on the right track.

Epiphany said:

You can argue that the inertial moment between a flywheel and a driveshaft has a fairly substantial delta - I agree.

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So we agree. Very, very, tiny reductions in inertial moment can be had with a CF driveshaft.

But I'll say it again, and perhaps a bit more overtly: If your goal is to reduce rotating mass, a CF driveshaft should be the last modification you make. The most tangible benefit is overall weight reduction.

I never argued that a rotating mass reduction was the mainstay in terms of reasoning for this mod. It may be a small reduction but it exists and as Albers pointed out it also has an effect on vibration at the shifter. The weight reduction is substantial as is the increase in critical speed over that of an aluminum or steel shaft.

Epiphany said:

... as is the increase in critical speed over that of an aluminum or steel shaft.

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Over a one-piece AL or steel shaft, but can the same be said about a two piece shaft?


I exceeded the critical RPM listed for my Dynotech 1-piece AL driveshaft in my 2011(with 3.73's) when I did the Texas Mile. If top speed is the goal I'd either keep the two-piece shaft or drop the rear gear ratio to reduce driveshaft RPM's.

I disagree...

CF will absorb the vibrations where as steel will resonate the vibration.

Tap a steel tube with a hammer. Hear the ring? Now try that with a Carbon tube...

Grimace427 said:

Over a one-piece AL or steel shaft, but can the same be said about a two piece shaft?


I exceeded the critical RPM listed for my Dynotech 1-piece AL driveshaft in my 2011(with 3.73's) when I did the Texas Mile. If top speed is the goal I'd either keep the two-piece shaft or drop the rear gear ratio to reduce driveshaft RPM's.

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I'd consult with a manufacturer I felt comfortable with when considering a shaft (or shafts) for an event such as the Texas mile. You can come fairly close numbers wise (having all the specifics - material properties, wall thickness, diameter, etc, will get you a more accurate number, obviously) by plugging in numbers for steel, aluminum, cf, length, etc, with a calculator such as this...

http://www.wallaceracing.com/driveshaftspeed.php

PP0001 said:

Interesting comment.

Did Ford not supply a one piece carbon fiber drive shaft in the late GT500 cars which certainly had much more torque than the new GT350?

:shrug:

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Exactly...

Couldn't get it stiff enough for what?

Ford already Stated that the CF shaft used on the GT500 offered improved NVH (noise,VIBRATION,harshness). and we all know carbon shafts are much stronger than steel so... Stiff enough for what???

SVTDSM said:

I disagree...

CF will absorb the vibrations where as steel will resonate the vibration.

Tap a steel tube with a hammer. Hear the ring? Now try that with a Carbon tube...

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The ring you hear is due to excitation of a natural frequency (correct on the resonance). If you don't hear it with a carbon tube it likely not because the CF is absorbing the vibration, but instead it has a higher natural frequency and was not excited. A lighter/stiffer DS will have a higher natural frequency, thus less likely to add additional NVH via forming standing waves and getting unbalanced. However having it attached to an existing vibration source, it will be more prone to directly transmit it elsewhere.

Certainly. The reduced rotational mass and elimination of the center joint allows for faster acceleration over that of a steel driveshaft(s) or aluminum driveshaft. CF shafts are easier on the driveline as they twist and then return to their original state, reducing dynamic "shock" under certain circumstances. In essence, their NVH qualities are much better than that of steel. CF shafts also have much higher critical speeds, the point at which a shaft can bend or whip.

There is a certain "smoothness" to a well done CF shaft that you won't feel in a steel or aluminum shaft, especially in the upper rpm ranges, which is exactly where the GT350 wants to be. Much like the Cf wheels on the R model, a CF driveshaft has the potential to offer a substantial weight reduction, an increase in driveline durability, as well as smoother driveline altogether. As I mentioned, if DSS can come up with a stiff enough design that is robust enough to live behind the high winding 5.2 (and its inherent vibratory potential) it'll definitely be a part worth taking advantage of.[/QUOTE]

After installing a 1 piece carbon fiber drive shaft in 2 of my Boss 302 cars I certainly agree with all of your above comments.

The smoothness noticed on acceleration was really noticeable and even though I have no scientific proof that each of my Boss cars accelerated quicker it sure seemed that way to me and I have owned many Boss 302 cars.

If memory serves me right (this was a couple of years ago) when I weighed the stock 2 piece steel drive shaft that used probably some ~18 pounds of ballast for vibration purposes I recall it being around ~45 pounds.

I believe the CF one piece unit was ~24 pounds so pretty much half of the rotating mass compared to the 2 piece stock unit.

Both CF units came out of DSS in Salisbury, N.C. and I recommend them highly as my experiences so very good.

Any idea of what the stock 2 piece steel unit will weigh in the GT350 versus the a new 1 piece CF unit from DSS?
:cheers:

krt22 said:

The ring you hear is due to excitation of a natural frequency (correct on the resonance). If you don't hear it with a carbon tube it likely not because the CF is absorbing the vibration, but instead it has a higher natural frequency and was not excited. A lighter/stiffer DS will have a higher natural frequency, thus less likely to add additional NVH via forming standing waves and getting unbalanced. However having it attached to an existing vibration source, it will be more prone to directly transmit it elsewhere.

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You are correct but it's not the ring (the type of noise) I was referring to, it is the fact that the sound resonates (continues).

A stiffer shaft will transmit more of the vibration through the driveline. Fact...