Custom carbon fiber driveshaft

[Performance nut]

I have been researching this for awhile and seen folks have asked a similar question but not in the way I intend it. I'm looking for a lighter driveshaft for my car that is going to remain naturally aspirated. I have seen the debate about whether or not an NA car needs/benefits from a carbon fiber driveshaft. Though my question isn't about using a carbon fiber driveshaft that is rated for 1000+ HP on an NA car. What I'm wondering is if it is possible to build a carbon fiber driveshaft that is rated for say 600-700HP.

I figure by having a lower HP target, you would be able to further reduce weight and possibly use techniques/parts that would never work on a 1000+ HP application but could work on a 600-700HP application. This is coming from a person that has an understanding of composites but not a full understanding of driveshaft design requirements. Most people way overengineer their parts because they want to be conservative or just don't understand composites.

Does anyone have any familiarity with this? Someone told me that the diameter is a function of length which I sort of understand but not really. I think what they meant to say is that the market is based on certain dimensions and we build around what is available. For example, you could technically build a 2" diameter driveshaft but good luck finding yoke ends that would work for my application.

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[Flyhalf]

Great question. I'm buying tomorrow qa1.
But your thought makes totally sense

 

[Barrel]

Could you build a slightly lighter CF driveshaft with lower HP/TQ requirements? I'm sure it could be done. Is the juice worth the squeeze? I doubt it. The QA1 unit (which I run on my car) is very light already.

 

[Performance nut]

Could you build a slightly lighter CF driveshaft with lower HP/TQ requirements? I'm sure it could be done. Is the juice worth the squeeze? I doubt it. The QA1 unit (which I run on my car) is very light already.

Well, that is the million-dollar question right there. It really will boil down to how much weight savings and function. The way I have been approaching this is process. Carbon fiber matrix weight savings will likely be small unless you get someone who understands, calculates, and tests the carbon fiber matrix to understand optimal setup. The other part that I have been wondering about is the yokes. If you could somehow make the yokes smaller (or at least a different shape where there is less material), you could open the door to more exotic materials that are even lighter but just as strong. Less material means cost may become more manageable. What if there was a way to make a true one-piece carbon fiber driveshaft that is wound end to end? I mean if you can make a wheel out of carbon fiber, it would literally be how you structure the build. May look different but its function would be the same.

Don't think anyone on here is in a position to build something like this but it would be interesting to hear people's thoughts on the matter.

 

[galaxy]

As mentioned, juice not worth the squeeze. It would be a huge financial undertaking (R&D, tooling, etc) for extremely little (dare I say, if any) gain. I’d bet a paycheck the weight savings/performance increase between your 2” vs the current 3.5” shafts on the market are negligible. Plus there’s no market for it. Why not go strong? Why would I run a smaller dia (when space is already not a factor), weaker, driveshaft with zero weight savings?

 

[Cory S]

Waiting for someone to manufacture a slightly lighter 2 piece aluminum shaft. 60% of the aftermarket 1 piece shafts are garbage and create nothing but problems.

My original stock 2 piece shaft from 2016 with 24K on it, has held up to numerous beat downs.

 

[Angrey]

The weight savings you'd get by squeezing the shaft diameter would be negligible and it frankly wouldn't be worth the additional risk.

Driveshaft design isn't as much a matter of horsepower as it is critical speed.

Yes, the ends, the attachments, etc, those all are chiefly power/torque, but the shaft itself is designed to withstand the natural vibrations and flex inherent in rotational lengths of materials.

The critical speed (rotation) is that which the vibrations become constructive and create a node, like a guitar string. The longer the shaft, the stiffer it needs to be in order to withstand the natural tendency to want to flex and bend like string.

Stiffness is primarily a function of the type of material and the diameter. There's some other aspects that go into where the forces are carried (a pipe of equal weight to a rod is going to flex less and have more rigidity for torsion for example).

I'm a fan of overthinking things and thinking outside the box.

Could you shave a few ounces off the shaft by going with a lesser joint? Sure, but I think you'll end up finding the impact and effect are either negligible or virtually unnoticeable.

The best shaft on the market (and it's not even close) is the QA1. Their materials, their methods for joining the ends, their relationship with 3M (and proximity to them) their testing methods, etc. I don't think I've ever read a complaint about one of their products. The others can be very good, but it's hit or miss.

Remember, part of the reason the shafts on S550 need to be so robust is because of the excessive length. By going to a short format transmission, yes, they saved some weight there, but you add some back in that the shaft now has to withstand a much lower critical speed. Ford decided to split the shaft to avoid critical speed challenges and simplify/cheapen a crucial part.

 

[Cory S]

The weight savings you'd get by squeezing the shaft diameter would be negligible and it frankly wouldn't be worth the additional risk.

Driveshaft design isn't as much a matter of horsepower as it is critical speed.

Yes, the ends, the attachments, etc, those all are chiefly power/torque, but the shaft itself is designed to withstand the natural vibrations and flex inherent in rotational lengths of materials.

The critical speed (rotation) is that which the vibrations become constructive and create a node, like a guitar string. The longer the shaft, the stiffer it needs to be in order to withstand the natural tendency to want to flex and bend like string.

Stiffness is primarily a function of the type of material and the diameter. There's some other aspects that go into where the forces are carried (a pipe of equal weight to a rod is going to flex less and have more rigidity for torsion for example).

I'm a fan of overthinking things and thinking outside the box.

Could you shave a few ounces off the shaft by going with a lesser joint? Sure, but I think you'll end up finding the impact and effect are either negligible or virtually unnoticeable.

The best shaft on the market (and it's not even close) is the QA1. Their materials, their methods for joining the ends, their relationship with 3M (and proximity to them) their testing methods, etc. I don't think I've ever read a complaint about one of their products. The others can be very good, but it's hit or miss.

Remember, part of the reason the shafts on S550 need to be so robust is because of the excessive length. By going to a short format transmission, yes, they saved some weight there, but you add some back in that the shaft now has to withstand a much lower critical speed. Ford decided to split the shaft to avoid critical speed challenges and simplify/cheapen a crucial part.

Did you know that QA1 gets 10% of their driveshafts returned? TEN percent..... 1/10 have more than .020" run out.. Stock shaft has been mid 8's numerous times. Just need an aluminum version with the strength of OEM, but only about 5-7lbs lighter for under $900, and they would be the most ideal shaft ever made.

 

[drive_55_not]

As mentioned, juice not worth the squeeze. It would be a huge financial undertaking (R&D, tooling, etc) for extremely little (dare I say, if any) gain. I’d bet a paycheck the weight savings/performance increase between your 2” vs the current 3.5” shafts on the market are negligible. Plus there’s no market for it. Why not go strong? Why would I run a smaller dia (when space is already not a factor), weaker, driveshaft with zero weight savings?

I agree the weight difference would be negligible, There isn't much of weight difference between aluminum and CF DS.

I installed a GForce 4" DS on my 2018 A10 and my notes show it weighed 24.5lbs.

Light weight wheels weighing 20lbs or so OTOH I can see making a difference.

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[Angrey]

Did you know that QA1 gets 10% of their driveshafts returned? TEN percent..... 1/10 have more than .020" run out.. Stock shaft has been mid 8's numerous times. Just need an aluminum version with the strength of OEM, but only about 5-7lbs lighter for under $900, and they would be the most ideal shaft ever made.

I agree, an Aluminum two piece would have a very good place in the market. It wouldn't save as much as eliminating the center joint and going to CF, but the weight savings would be considerable over the steel and it would have less critical speed and half critical speed issues.

Remember, a lot of "returns" or issues with driveshafts aren't the shaft. It's the 1/2 critical speed, which is dominated by the two angles at the trans and the diff.

Ideally, for any "U joint" to function properly, it has to feature a little bit of angle to lube itself. If the corresponding counter angle at the other end isn't very close to being equal and opposite, you get what's referred to as half critical speed issues.

CV joints ("constant velocity") joints don't have that problem. But in order for a CV joint to be equally as strong as a 1310 or worse a 1350 joint, it has to be very large and heavier.

Honestly, the BETTER solution (to me) is to return to a tail section transmission.

The tradeoffs honestly aren't worth the weight savings for eliminating the end section.

MOST die hard manual guys are going to add very robust (and heavier) shifters and assemblies or braces to improve shifting feel and performance (thus adding back weight that was the whole point). The longer shaft makes the driveshaft issue MUCH MUCH more complex.

With a Magnum XL, my shaft length is about 36" and even though QA-1 hadn't done any testing on it (because it's a custom product) the gentleman I spoke to indicated he was quite confident it would test out well over 200 mph (in 1:1 or even over drive).

The worst condition the shaft can see is redline in 1:1. In theory, redline in overdrive would be worse, but few people have enough sauce to get the car into overdrive and that high rpm.

But I agree, if someone made an improved two piece, I'd have to seriously consider it if I was still running a 3160 or a 6060 (or god forbid an MT82).

 

[Performance nut]

The weight savings you'd get by squeezing the shaft diameter would be negligible and it frankly wouldn't be worth the additional risk.

Driveshaft design isn't as much a matter of horsepower as it is critical speed.

Yes, the ends, the attachments, etc, those all are chiefly power/torque, but the shaft itself is designed to withstand the natural vibrations and flex inherent in rotational lengths of materials.

The critical speed (rotation) is that which the vibrations become constructive and create a node, like a guitar string. The longer the shaft, the stiffer it needs to be in order to withstand the natural tendency to want to flex and bend like string.

Stiffness is primarily a function of the type of material and the diameter. There's some other aspects that go into where the forces are carried (a pipe of equal weight to a rod is going to flex less and have more rigidity for torsion for example).

I'm a fan of overthinking things and thinking outside the box.

Could you shave a few ounces off the shaft by going with a lesser joint? Sure, but I think you'll end up finding the impact and effect are either negligible or virtually unnoticeable.

The best shaft on the market (and it's not even close) is the QA1. Their materials, their methods for joining the ends, their relationship with 3M (and proximity to them) their testing methods, etc. I don't think I've ever read a complaint about one of their products. The others can be very good, but it's hit or miss.

Remember, part of the reason the shafts on S550 need to be so robust is because of the excessive length. By going to a short format transmission, yes, they saved some weight there, but you add some back in that the shaft now has to withstand a much lower critical speed. Ford decided to split the shaft to avoid critical speed challenges and simplify/cheapen a crucial part.

This is what I've been looking for in a sense. I was hoping someone had seen an engineering blog or something that goes into detail the engineering behind one of these. Sort of like what Mishimoto does on their engineering blogs. My curiosity stems from what you said about critical speed, vibration, and stiffness requirements based on the length of the driveshaft. My reasoning is that there may be different engineering goals in mind when these are designed. But I don't know for sure because like you said there is likely a critical dimension that is a must no matter what power level you are at due to other factors like length or rotational speed.

I'm starting to think that the reason I can't find this information is less because they are aiming for high horsepower applications and more to do with IP concerning their manufacturing processes. No one probably wants to share for fear of duplication and losing market share.

 

[Angrey]

This is what I've been looking for in a sense. I was hoping someone had seen an engineering blog or something that goes into detail the engineering behind one of these. Sort of like what Mishimoto does on their engineering blogs. My curiosity stems from what you said about critical speed, vibration, and stiffness requirements based on the length of the driveshaft. My reasoning is that there may be different engineering goals in mind when these are designed. But I don't know for sure because like you said there is likely a critical dimension that is a must no matter what power level you are at due to other factors like length or rotational speed.

I'm starting to think that the reason I can't find this information is less because they are aiming for high horsepower applications and more to do with IP concerning their manufacturing processes. No one probably wants to share for fear of duplication and losing market share.

Again, what's dominating the shaft design has nothing to do (directly) with power, it has to do with how fast they anticipate the shaft will spin. Yes, in order to reach 8,000 rpm in 1:1 ratio at typica rear end gearing, the car has to have at least some elevated level of power, but the shaft manufacturer is chiefly concerned with ensuring the shaft doesn't flex and fly apart at high speed, (not how much it can withstand in a torque slam during a drag launch). Strength for torque loading is a secondary consideration/benefit.

In fact, MOST big boy race teams that are running CF as much for safety reasons as for flex/strength/weight. When CF fails, it shreds into pieces instead of beating the car to death. Then they only have to contend with the steel components bouncing around and destroying stuff.

 

[80FoxCoupe]

Got a qa1 carbon for sale fyi. 2015-17 6r80 car, perfect shape!

 

[galaxy]

Did you know that QA1 gets 10% of their driveshafts returned? TEN percent..... 1/10 have more than .020" run out..

Prior to you stating this in a couple threads now, I have never heard this before about QA1. Not gonna dispute it, but seems…odd…to me at least. I’d bet a paycheck there’s not 1/10 returned from this community. Maybe company as a whole? Maybe DSS has those numbers, LOL. I couldn’t be happier with mine and the noticeable difference over stock is certainly noticeable.

 

[Cory S]

Prior to you stating this in a couple threads now, I have never heard this before about QA1. Not gonna dispute it, but seems…odd…to me at least. I’d bet a paycheck there’s not 1/10 returned from this community. Maybe company as a whole? Maybe DSS has those numbers, LOL. I couldn’t be happier with mine and the noticeable difference over stock is certainly noticeable.

This was literally quoted from the sales associate there.

If you got a good one, that's great. My buds literally destroyed his pinion bearing within 20 miles. Took him 3 months to get them to take it back claiming his measured runout of .022" was acceptable.....

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