Carbon Fibre Tail Shaft

[Beer Baron]

sorry Gary you may be right. i remember though that when it was introduced the duty was dropped from 15% to 10% with a view to making it 0% in the future. I'm not sure what the time frame was though, it may have happend already.

but regardless of the actual rule the collection of taxes on small, low volume importing is a bit haphazzard.

[Swiper the Fox]

Is that 105 kg of rotating weight?

You really need to compare the cost per KG in reference to say, wheels.

Would you spend $2,500 to save 2.5kgs per wheel?

Doesn't seem unreasonable to me when compared to the price of a set of Volks.

cheers

<{POST_SNAPBACK}>

what does it matter...its sprung weight?? please tell me the difference, in a drag car we need as much inertia in the drive line we can get...thats why i run a VL atmo flywheel, its nice and heavy. The example you used is a wheel...this is unsprung weight and not a sensible example to use.

[ylwgtr2]

id like to see a busted one....i reckon i could make one and have thought about it before

[xr8eater]

i have prepreged yacht masts in carbon that held up to 12 tonnes but they never had much twist this was allways the cause of them faulting. i would also like to see one that snapped and where it faulted

Edited December 12, 2005 by xr8eater

[rev210]

what does it matter...its sprung weight?? please tell me the difference, in a drag car we need as much inertia in the drive line we can get...thats why i run a VL atmo flywheel, its nice and heavy. The example you used is a wheel...this is unsprung weight and not a sensible example to use.

<{POST_SNAPBACK}>

The wheel is a 'driven' rotational mass that is connected to the engine/drivetrain.Engine -flywheel-gearbox-tailshaft-diff-wheels.

Weight reductions in this area reduce inertia significantly. This is why it is not just 'unsprung weight'. This is why race cars like light wheels.

The extra inertia you have sought in the heavier flywheel was often used to assist overcoming issues of rev matching and bogging down with low amounts of power and large amounts of grip. I would lean towards turfing the cast iron (read very weak by comparison to chromemolly) flywheel and trying launch control, if off the line horsepower is the issue. Or turfing it in favour of very heavy steel rims (if you really must increase the weight which I don't agree with) ,the rolling intertia and extra weight potential is better than the slightly heavier RB30de flywheel. Contrary to old wives tales there is no loss of torque going lighter.

It would suprise me very greatly if you didn't improve your accelleration times by approaching the issue of reducing the rotational inertia. So far it is only my humble opinion that you might have gone the wrong way here? (and perhaps only here)

I hope that adds some usefull info for you, please feel fee to PM if you would like to question things a little more, I am very happy to try and help

Edited December 13, 2005 by rev210

[Sydneykid]

what does it matter...its sprung weight?? please tell me the difference, in a drag car we need as much inertia in the drive line we can get...thats why i run a VL atmo flywheel, its nice and heavy. The example you used is a wheel...this is unsprung weight and not a sensible example to use.

<{POST_SNAPBACK}>

Newtons law in action.

To accelerate the car, first the engine must accelerate the rotating assemblies. That's everything in between the harmonic balancer and the tyre. The lighter you make them, the less power is absorbed accelerating the rotating parts and the more power there is left over to accelerate the car.

Try it for yourself, jack the car up and free rev the engine with the clutch in. Then stick it in 4th gear as it is 1 to 1, sorry 5th gear in your case, you have close ratio gears. Compare how much slower the engine revs, because it has to accelerate all of the rotating parts.

Heavy components are useful for holding rpm, because they store kinetic energy. But when acceleration (or deceleration) is important you want the lightest rotating mass you can achieve.

cheers

[9krpm]

good to see that someone still remember Physics.

Yes you are absolutely correct sk. The further they are away from the centre of the rotation the more inertia also.

DiRTgarage, your heavier flywheel helps your launch because it has more momentum than a lighter one. Your propshaft however does not spin until you launch So the heavier it is the more bog you may have.

Edited December 13, 2005 by 9krpm

[ylwgtr2]

the pic of the shaft posted may not be prepreg....unless its been cleared

[Swiper the Fox]

cool...thanks guys for the lesson. i think ill still save my $$ and spend them elsewhere. We find that the heavy flywheel assists with launch and 60' times as well as slightly assisting with gearchanges. In the 1.4's with 60' and nearly into 9's with the ET's so we must be doing something right. Think ill have more of a benefit with a $3000 NOS setup than a bling tailshaft though.

[xr8eater]

the pic of the shaft posted may not be prepreg....unless its been cleared

<{POST_SNAPBACK}>

cleared?? clear epoxy

i dont understad/\

[rev210]

cool...thanks guys for the lesson. i think ill still save my $$ and spend them elsewhere. We find that the heavy flywheel assists with launch and 60' times as well as slightly assisting with gearchanges. In the 1.4's with 60' and nearly into 9's with the ET's so we must be doing something right. Think ill have more of a benefit with a $3000 NOS setup than a bling tailshaft though.

<{POST_SNAPBACK}>

ok.

Back on topic then.

[rev210]

I got an email from James Martin the product manager at ACPT regarding some of the questions and rumours raised in this thread..

He very kindly responded in the email as follows;

We have 2 applications for all the Skyline models. The smaller

application will handle up to 800hp, and the bigger application will

handle over 2000hp. So if you order a shaft we will need to know what

size you want. Also, the bigger shaft is about $200.00 more than the

price that I quoted you earlier. ACPT has been making the Skyline

shafts for years and we do not require the stock shafts. We have been

making the driveshafts for Nismo and Trust for a while now and this is

why we don't need your stock measurements (unless you have a different

rear end or transmission than the stock application.) The person

claming to have broken 2 of our shafts bought the smaller shaft because

it was cheaper and was hoping that it would work. This is why we have 2

applications, if you have under 800hp and you do not plan on exceeding

this much horsepower, than the smaller application is for you. If you

know that you will exceed 800hp, then you will need to use the larger

application. If he had something rubbing on the shaft like an exhaust

bracket or a sway bar, that would have caused it to break as well. ACPT

is the original maker of the carbon driveshaft over 20 years ago. Also,

ACPT is not a driveline shop; we are an aerospace company that typically

builds parts for rockets, space shuttles, government assault vehicles,

ECT... The same engineers that develop the parts for the aerospace

companies are the same engineers that work on the driveshafts. All ACPT

deals with is composites and all of our driveshafts are built in house

including the winding of the driveshaft tubing. I do not know much

about the UK company making a carbon shaft other than it looks really

pretty (but you will never see it underneath you car) and it is really

expensive. If I am not mistaken, I believe our driveshaft is about half

the price of their shaft and is proven to handle what ever kind of

horsepower you can get out of your car.

[Beer Baron]

well if i hadn't spent about $6K in this last week on air tickets and car related stuff i would buy one in a second. they look like a very nice product.

[xr8eater]

thanks for clearing that up rev201 sounds like an after xmas thing for me $2000 is cheep

[keith cowie]

I got an email from James Martin the product manager at ACPT regarding some of the questions and rumours raised in this thread..

Hi rev210

The Guy that i was dealing with at ACPT was called Peter it is funny

because when i asked them i had to send the 2 ends from my shaft

and they only made one size,they were going to look at making a large

shaft and get back to me,i never heard from them again.

Keith

[m&m]

I'll be getting one from ACPT in the New Year,If there is a group buy,great,If not,I'm still getting one.

I have never seen a tacho move as fast as that Mines GTR,its my inspiration.

[9krpm]

I am keen on a GB as well.

Can't afford it now but if there is a GB\, I dfinitely get one. I will try to do some overtime make up for it . Reducing rotational mass is always good.

[manage13]

I am keen on a GB as well. 

Can't afford it now but if there is a GB\, I dfinitely get one.  I will try to do some overtime make up for it .  Reducing rotational mass is always good.

<{POST_SNAPBACK}>

I'm also in!

[ferni]

This is a bit off topic I guess, but.... how can you say a lightened flywheel doesn't cause driveability issues.  You could say that in your case (and probably many other cases) it hasn't.  But, if you are passing on accurate information to those who haven't had experience, then you should add that a lightened flywheel "can" cause issues.  Consider the basic physics.  Using an extreme case to illustrate the point -  If there were no flywheel the engine would have very little momentum and trying to get the clutch out (from a standing start) without stalling would be nearly impossible.   

Things that will affect whether driveability is impacted by a lightened flywheel are:

1. How much lighter the flywheel is, and

2. What type of clutch you are using

I have a 5.5kg billet flywheel and a fairly bitey 5 puck clutch and the difference is quite noticeable.  It is a track car, so I don't care.  I personally would not use the same configuration for the street, as I would find it annoying to use in traffic.

<{POST_SNAPBACK}>

Exactly, I had a lightened flywheel in my car, it shit me on the street, when going slow, couldn't go below 2000rpm without the car shuddering/labouring.... im back to a stock flywheel now.

[xr8eater]

what a waist of $$$$$$$ eh

i suppose it's just like shocks good for the track shit for the road