aluminum drive shaft - anyone?

[themadscientist]

Originally Posted by GT86_PRAGUE

Dude, I was not asking for engineers point of view!

This says a lot. Opinion can't stand up to science; I've heard that before.


How much of my money will you be needing for this "miracle?"

[JDKane527]

Originally Posted by GT86_PRAGUE

I didnt told I value more some guy who need to justified his purchase (or sell it like Rick) over an engineer. I just want to hear an opinion from someone WHO HAS IT and I would than make some assumptions myself.

I read the science above and I dont believe it either.
I can save 10kg on battery for 1/3 price of propshaft, so there must be more to this. Again, not asking for any engineering stuff, but possible oppinion of someone WHO PERSONALLY DID THIS.

As an engineer and someone who has personally installed lightened driveline components, dropping 10 lbs of rotating mass will make a bigger difference than dropping 10 lbs of static mass. But I'm an engineer...

[themadscientist]

Originally Posted by JDKane527

But I'm an engineer...

[GT86_PRAGUE]

Originally Posted by themadscientist

[burdickjp]

Originally Posted by JDKane527

As an engineer and someone who has personally installed lightened driveline components, dropping 10 lbs of rotating mass will make a bigger difference than dropping 10 lbs of static mass. But I'm an engineer...

But what is the benefit/cost ratio? Is it more than the battery?

[JDKane527]

Originally Posted by bur****jp

But what is the benefit/cost ratio? Is it more than the battery?

Battery
Pros:
Dropping weight off front passenger corner to shift center of gravity rearward to the driver side of the car
Mass is high relative to the car's center of gravity, so removing would lower it slightly

Cons:
Lower capacity battery
May require a special charger to balance charge


Driveshaft
Pros:
Dropping weight in rotational mass
Carbon driveshaft helps reduce shock to drivetrain

Cons:
Dropping weight from the lowest most central part of the car, so should in theory slightly raise the car's center of gravity
Aluminum driveshaft transmits shock and vibration through the drivetrain.


Would dropping 25 lbs in a battery be equivalent to dropping 12 lbs with a carbon drive shaft? Could you even feel either modification? You would more likely feel the effect of a lighter driveshaft did than you would the effect of a lighter battery.

I'm not sure what battery and if you were thinking about an aluminum or carbon shaft. I'll assume its a Ballistic life pack that weighs 3 lbs.
Battery (3lbs, 28-3lbs = 25lbs savings) - $250
Aluminum shaft (13.2lbs, 24.2-13.2lbs = 11lbs savings) - $420
Carbon shaft (12.1lbs, 24.2-12.1lbs = 12.1lbs savings) - $1000

Battery would net you most static weight drop per dollar
25 lbs / $250 = 0.1 lb/$
11 lbs / $420 = 0.026 lb/$
12.1 lbs / $1000 = 0.0121/$

Dropping rotational mass will make the most noticeable effect, but it would be to a very small magnitude still and difficult to quantify. If you were looking to drop rotational mass, get a lightweight clutch and flywheel to get mass that is rotating faster, and then get a driveshaft. If your battery needed to be replaced, then it would be a great time to get a lightweight battery. I have a lightweight battery and honestly didn't notice much of a difference in handling. Then again I haven't had the car corner balanced since installing it so that may have a part.

FWIW, I plan to get a carbon driveshaft in the future.

[stugray]

Originally Posted by GT86_PRAGUE

Dude, I was not asking for engineers point of view!

You asked a question, I answered with a fact.
If you cant handle the answer, dont ask the question.
YES a CF driveshaft will make a difference - less than 1/10th APPARENT hp.

Reducing rotating mass DOES NOT increase horsepower in any way. PERIOD. FACT.
Can it result in faster acceleration - yes.
Can it provide Higher engine RPMs - yes.

Do you think the engineers that designed the space shuttle tested the whole assembly before they launched it the first time, or did they CALCULATE the total thrust of all three SMEs + SRBs?

GUESS WHAT - THEY CALCULATED IT and ... wait for it.... they were RIGHT.

[cdrazic93]

Originally Posted by stugray

GUESS WHAT - THEY CALCULATED IT and ... wait for it.... they were RIGHT.

But but but...i dont believe you

[GT86_PRAGUE]

Originally Posted by stugray

You asked a question, I answered with a fact.
If you cant handle the answer, dont ask the question.
YES a CF driveshaft will make a difference - less than 1/10th APPARENT hp.

Reducing rotating mass DOES NOT increase horsepower in any way. PERIOD. FACT.
Can it result in faster acceleration - yes.
Can it provide Higher engine RPMs - yes.

Do you think the engineers that designed the space shuttle tested the whole assembly before they launched it the first time, or did they CALCULATE the total thrust of all three SMEs + SRBs?

GUESS WHAT - THEY CALCULATED IT and ... wait for it.... they were RIGHT.

You claiming to be an engineer doesnt mean that you are automatically right. You failed to understand I asked for someone with real experience and you didnt changed you propshaft obviously, you only crunch some numbers. So yes, you might be right on the numbers but thats not what I was asking for.

[cdrazic93]

Originally Posted by GT86_PRAGUE

You claiming to be an engineer doesnt mean that you are automatically right(1). You failed to understand I asked for someone with real experience(2) and you didnt changed you propshaft obviously, you only crunch some numbers(3). So yes, you might be right on the numbers but thats not what I was asking for.(4)

1. Being an engineer is being an applied mathematician. We go to school to get it right, over and over and over again. Eventually it becomes second nature to us, thus doing the math for a real world problem (LIKE THIS ONE) give numbers that (when all other factors are negligible) will give you minimal difference.

2. I still think you fail to understand, experience is biased no matter how hard you try and make it not be.

3. Here's a question from my physics textbook chapter 8 rotational kinematics, (the same principles used to do all this fancy unicorn work with the driveshaft);

The angular speed of an automobile engine is increased uniformly from 1170 rev/min to 2880 rev/min in 12.6 seconds. a) find the angular acceleration in rev/min^2 b) how many revolutions does it make in this time?

can you see how the math can numerically quantify a real world problem?

4. You're looking for approval for buying the driveshaft. You keep wanting someones experience review for it, yet this thread basically disproved its ability to significantly, even minimally improve acceleration. You've already made up your mind about it and refuse to believe that it doesn't do any good.

[GT86_PRAGUE]

Thanks for playing, I give up.

[cdrazic93]

Originally Posted by GT86_PRAGUE

Thanks for playing, I give up.

Here's a great idea, how about instead of looking for someone else's experience about the driveshaft, why not buy it and make your own experience. Don't look for approval in the internet.

[FRS Johnny]

just get both and be happy!

[themadscientist]

Originally Posted by stugray

Do you think the engineers that designed the space shuttle tested the whole assembly before they launched it the first time, or did they CALCULATE the total thrust of all three SMEs + SRBs?

GUESS WHAT - THEY CALCULATED IT and ... wait for it.... they were RIGHT.

They think you should get the CF driveshaft. Their slide rules all agree.