aluminum drive shaft - anyone?

[Xinshadow]

Originally Posted by Poodles

One piece driveshaft doesn't make sense for big power as big power = higher speeds.


One can easily go over the critical speed of a one piece driveshaft in this car because of it's low final drive!




One word: Placebo




It's not hard for him and math and science is not opinion.




It's making it LESS safe as it's introducing a critical speed failure mode into the equation.





As I've already said, the center bearing is NOT for NVH, but for safety to raise the driveshaft's critical speed.




Well, if it's a BRZ you're only consuming 35w x 2, but that's the headlights only, but you still make a good point





1) 0-100MPH is published and he's done all his previous calculations with the same metric. Changing that metric would only confuse people.


2) Turbos have lag (which is quantifiable) and they void warranties meaning they can possibly be more expensive in the long run...





Axial strength is pretty pointless on a driveshaft. I'll say it again: DRIVESHAFT CRITICAL SPEED IS FAR WORSE.





RX8: Kinda carbon fiber (carbon reinforced plastic)
350Z: carbon fiber
370Z: same fing car...
GTR: Carbon fiber.
Z06: Doesn't count as it's a torque tube setup (tranny is in the rear)


Most of those are carbon fiber. Carbon fiber is used because it allows them to run a single piece driveshaft without having driveshaft critical speed issues. It's also fragile and has to have shields to prevent foreign objects from hitting it.





I don't see anyone breaking the stock driveshaft. It's also NOT stronger as (god I feel like I'm beating a dead horse here) driveshaft critical speeds will occur.


As none of the driveshaft companies want to give out their specs of the shaft (big surprise as it's probably unsafe), I'm guessing at the specs.


If someone wants to get me length, diameter, and wall thickness, it's easy to figure this stuff out...

So I see this critical speed thing pop up a lot and I get the gist, but how unsafe are they really as it relates to problems with critical speed? I mean I have 50+ buddies who circuit and drag race imports and domestic RWD and use aluminum (specifically not CF due to the drawbacks of price, lead time and additional hardware ), driveshafts, and not a single one of them in ten years has ever said they suffered a failure in that way. If and when they do fail it's always because they can't hold enough torque and twist up.

Not trying to be a ****, I'm genuinely curious if this is something that any of us can reasonably expect to encounter in a performance application or if this is something thats mathematically possible but very unlikely given our platform.

[twag4]

Golly this is a fun read!

[cdrazic93]

Originally Posted by Xinshadow

Not trying to be a ****, I'm genuinely curious if this is something that any of us can reasonably expect to encounter in a performance application or if this is something thats mathematically possible but very unlikely given our platform.

9.999999999/10 times, no. That .0000001% would account for possible defects, which are unlikely. The driveshaft critical speed is a speed that wouldn't be attainable with the power given to the car. Nor the transmission. This car tops at ~140 or so, so the critical speed of the driveshaft would be somewhere close to or north of 200mph to be safe. At the point of changing the gearing and aerodynamics of the car to get there, you would have already replaced the driveshaft anyway.

You are 100% more likely to twist the shaft from the resulting torque of the motor, or break the transmission.

When a driveshaft reaches critical speed; it reaches the natural frequency of the material it's made out of, making it unbalanced and you will quickly lose control of the car. Not something you want to have happen at that critical speed.


Folks who engine swap or build the piss out of this car end up replacing the stock unit with a stronger one anyway (in this case, a faster spinning one).

[cdrazic93]

Originally Posted by Manic

It's akin to taking a heavy shit and driving your car naked in hopes that the reduced sprung weight is going to improve your lap times. Technically you've reduced the sprung weight of your car. Does it have a practical benefit? Nope.

Best. Example. Ever.





Bu....but the guys on hondatech said....

[cdrazic93]

Originally Posted by Koa

Stu continually making haters out by being one of the realest people here.. straight up let 'em have it

Oh, he let em have it alright.

[Captain Snooze]

Originally Posted by Manic

It's akin to taking a heavy shit and driving your car naked in hopes that the reduced sprung weight is going to improve your lap times.

Acceleration ∝ mass of shit.

[cdrazic93]

Originally Posted by Koa

http://openmymind.net/2012/4/18/Lear...-Than-Knowing/

I follow that mantra with a zeal in all I do, both professionally as an accountant, passionately as a gearhead and musician, and personally as a lover and friend. It's all about knowing (pun intended) how to learn

@Koa likes long walks on the beach, underground poetry coffee houses and hanging out with @Tcoat on the weekends.

[Dimman]

Err...

I did his big formula comparing the baseline 2800lbs (1272kg) to 100 mph (44.8 m/s)(I got 1279866.76 J total of system plus driveshaft and 79004.12 J/sec) vs a 15 lbs driveshaft reduction so 2785 lbs (1265.9kg) (1272059.76 system plus driveshaft).

1272059.76/79004.12 = 16.101 sec. One millisecond shy of an entire tenth. That seems like a big difference, and more significant than your 44 milliseconds zero mass driveshaft.

What's wrong with my math?

Edit: Would that be just over an entire car length ahead (174 inches)?

[Tcoat]

Originally Posted by cdrazic93

@Koa likes long walks on the beach, underground poetry coffee houses and hanging out with @Tcoat on the weekends.

Hey! How the hell did I get dragged into this!?
Like at work, I just enjoy sitting back and letting the engineers argue and then tell the winner he can't do what he wants anyway since the ROI is under 2 years!

[CBR600RR]

Originally Posted by Koa

uhh noo.. considering you haven't realized that with rotating mass vs sprung mass is a 1.1:1 ratio, some claiming 1.26:1 ratio... here's the takeaway: it literally does NOT make a difference.

Your "point" doesn't hold any water because it DOES NOT make a single difference. It's people like you who try to come here and make a "point" just for the sake of making a point. What is it you're really arguing? "clear cut obvious"- uhh no, it's clear cut obvious that your point sucks. Lol get used to it when you have that kind of mindset.

Refer to Razic's very eloquently stated and explained post about how you're so god damn wrong it hurts that you're still here >> http://www.ft86club.com/forums/showp...6&postcount=93

Try again

Look, I I'll say it again, understand that the difference would be very minute, even to the point of being almost non-existent. I never claimed anything in the contrary. What I did say is that one is better than the other, which is 100% true and no one can argue that, but everyone seems to think I said that a light weight drive shaft is the miracle go-fast mod. Go back and read all my posts in this thread, and tell me I am wrong about anything. Please do.

Again, my point was simply that one is better than the other when considering an equal amount of weight.... Put it in the perspective of the racing community. Do they all ignore reducing rotational mass because its effects are minimal? No. In the racing world milliseconds count, and racing teams like to add all these milliseconds up so that they may have the best advantage.

I really hope that we can all just get along...

When I say it is "clear-cut-obvious" I am talking about the physics of it, not the butt dyno feel of the drive shaft. Take two completely stock cars, made the EXACT same, all conditions are the exact same, all variables are the exact same, the driver input is the exact same, but, reduce the over all weight of one car by 15lbs, and then put a driveshaft in the other car that is 15lbs lighter. Put them in a 1/4 mile drag race. The one with the light weight drive shaft wins every time. Even if you have to measure the win by nanometers, it still wins every time. Am I missing something here?

And the 600rr is a blast

[industrial]

Originally Posted by CBR600RR

Look, I I'll say it again, understand that the difference would be very minute, even to the point of being almost non-existent. I never claimed anything in the contrary. What I did say is that one is better than the other, which is 100% true and no one can argue that, but everyone seems to think I said that a light weight drive shaft is the miracle go-fast mod. Go back and read all my posts in this thread, and tell me I am wrong about anything. Please do.

Again, my point was simply that one is better than the other when considering an equal amount of weight.... Put it in the perspective of the racing community. Do they all ignore reducing rotational mass because its effects are minimal? No. In the racing world milliseconds count, and racing teams like to add all these milliseconds up so that they may have the best advantage.

I really hope that we can all just get along...

Take two completely stock cars, made the EXACT same, all conditions are the exact same, all variables are the exact same, the driver input is the exact same, but, reduce the over all weight of one car by 15lbs, and then put a driveshaft in the other car that is 15lbs lighter. Put them in a 1/4 mile drag race. The one with the light weight drive shaft wins every time. Even if you have to measure the win by nanometers, it still wins every time. Am I missing something here?

And the 600rr is a blast

The fact that this mod makes the car ever so slightly faster and responsive has been long established in this thread. What everyone is getting their panties bunched up about is trying to prove with numbers whether someone else can feel the difference or not and therefore, based on the numbers which prove the amount of mathematically proven feeling difference™, discover the true worth of this mod. Great stuff.

[tennisfreak]

An easy real world test that any of us can do to help better understand rotating mass, weight, circumference, etc..

Go to your local playground (must be one with a merry-go-round).

Now you can spin it yourself and hop on or have a friend spin it while you are on it.

The merry-go-round when spinning is rotating around in a circle.

Start out at the very center.
As the merry-go-round is spinning slowly try and work your way out from the center to the edge.
Note how in the center you feel little if any forces pulling you out toward the edge.
As you work your way out towards the edge not how the forces gradually then rapidly increase.
If your friend is spinning the merry-go-round he should notice as you work your way to the edge it requires more force to keep the merry-go-round rotating at the same speed.

It may not be a perfect test but it is an easy one to see the correlation between the mass and relationship to the center/perimeter of rotation.

The point of the test is to show how even at the same weight there is a significant difference in the amount of force required to rotate something as weight moves from the center to the perimeter.

Another valid test is to spin the merry-go-round with nothing on it.
Then have someone stand dead center on the merry-go-round and spin it.
You will be surprised to notice that it requires very close to the same amount of force to spin it with someone on the merry-go-round as with someone off even though there is a big difference in weight.

[Koa]

Originally Posted by industrial

The fact that this mod makes the car ever so slightly faster and responsive has been long established in this thread. What everyone is getting their panties bunched up about is trying to prove with numbers whether someone else can feel the difference or not and therefore, based on the numbers which prove the amount of mathematically proven feeling difference™, discover the true worth of this mod. Great stuff.

"ever so slightly responsive and faster.. The true worth of this mod..."

Worth of expenditure and 'feel' are subjective.

Physics and the laws of motion are not.

Notice we're not saying the 15 pounds savings isn't worth ANYTHING. We're saying the cost per benefit is absurd for something that Rrealistically cannot be felt by those who are incapable of feeling the power increase that amounts to 44 milliseconds through a typical 0-100 run. That is an opinion. Definitely.

So there's that... you can indeed prove with mathematics what nature PROVES of this mod's worth. The real issue is that you come here saying you can actually feel a performance gain because unless you're a superhuman capable of feeling 44 milliseconds throughout a 0-100 run, you are just placebo tricking your mind. Probably NVH. There's that.

Come back with some "real world" track data to back up your claims and prove us, including physics, wrong. That you really won the race against yourself at the end of the day.

--

Here's the fatal blow to your position: A FUNDAMENTAL grounding principle of the scientific method: If the trial is not able to control all variables, which in this case would be driver error, it is no good. Show me a driver that is consistent to less than 100 milliseconds and I'll show you a liar. Prove me wrong in this.

THEREFORE,

With such a minuscule gain, this is an untestable claim that the driveline provides a perceived, "felt", benefit. Facts only become facts after artefacts and claims are subject to trials of strength, by various actors and laboratories and anti-laboratories. Only after the fact-to-be is able to be championed by those willing to test the claim, and survive the onslaught of trials of strength (testing), can the artefact become a FACT. Then, the fact can be altered and moved 'downstream' via positive modalities, or called out via negative modalities. Those are important themes to what's happening here. You're taking a fact that this type of reduction produces a gain, NO MATTER HOW MINISCULE, and moving that forward, via a positive modality, to "one is able to feel this gain throughout the driving experience- not just an increase of NVH, but an actual felt increase in power".

Bruno Latour, father of the discipline Science and Technology Studies, an increasingly important scientific discipline under the STEM cirricula, wrote at length about this in his landmark 1984 work, "Science in Action". I recommend you read this to understand the absurdity of your claims of real-world versus conceptual facts surrounding this case.

Conceptually, it's un-perceptible. It is supported by hundreds of years of scientific studies that humans' margins of errors in time tests exceed the milliseconds we're talking about here. Does that not ring a bell for you? Because that's a VERY important part of this discussion.

Can't argue with the scientific method.

[industrial]

Originally Posted by Koa

"ever so slightly responsive and faster.. The true worth of this mod..."

Worth of expenditure and 'feel' are subjective.

Physics and the laws of motion are not.

Notice we're not saying the 15 pounds savings isn't worth ANYTHING. We're saying the cost per benefit is absurd for something that Rrealistically cannot be felt by those who are incapable of feeling the power increase that amounts to 44 milliseconds through a typical 0-100 run. That is an opinion. Definitely.

So there's that... you can indeed prove with mathematics what nature PROVES of this mod's worth. The real issue is that you come here saying you can actually feel a performance gain because unless you're a superhuman capable of feeling 44 milliseconds throughout a 0-100 run, you are just placebo tricking your mind. Probably NVH. There's that.

Come back with some "real world" track data to back up your claims and prove us, including physics, wrong. That you really won the race against yourself at the end of the day.

--

Here's the fatal blow to your position: A FUNDAMENTAL grounding principle of the scientific method: If the trial is not able to control all variables, which in this case would be driver error, it is no good. Show me a driver that is consistent to less than 100 milliseconds and I'll show you a liar. Prove me wrong in this.

THEREFORE,

With such a minuscule gain, this is an untestable claim that the driveline provides a perceived, "felt", benefit. Facts only become facts after artefacts and claims are subject to trials of strength, by various actors and laboratories and anti-laboratories. Only after the fact-to-be is able to be championed by those willing to test the claim, and survive the onslaught of trials of strength (testing), can the artefact become a FACT. Then, the fact can be altered and moved 'downstream' via positive modalities, or called out via negative modalities. Those are important themes to what's happening here. You're taking a fact that this type of reduction produces a gain, NO MATTER HOW MINISCULE, and moving that forward, via a positive modality, to "one is able to feel this gain throughout the driving experience- not just an increase of NVH, but an actual felt increase in power".

Bruno Latour, father of the discipline Science and Technology Studies, an increasingly important scientific discipline under the STEM cirricula, wrote at length about this in his landmark 1984 work, "Science in Action". I recommend you read this to understand the absurdity of your claims of real-world versus conceptual facts surrounding this case.

Conceptually, it's un-perceptible. It is supported by hundreds of years of scientific studies that humans' margins of errors in time tests exceed the milliseconds we're talking about here. Does that not ring a bell for you? Because that's a VERY important part of this discussion.

Can't argue with the scientific method.

We are going around in circles. The math that's parroted over and over again in this thread by stu is barely applicable. I disagree with your position and feel absolutely no need to prove anything to you or anyone else here. I know for a fact this mod is beneficial. That's enough for me. Whether or not I can feel it is another story. 5hp from run to run would not be discernible so does that make it not worthwhile? You have to understand your position is ridiculous. Just because you can't feel the benefit doesn't mean there isn't one or that it's not worth pursuing. Vote with your wallet and move on for fucks sake.