Lightweight Pulleys

[Mik]

Mik,

Accellerate without more power you are saying no?

I think there is a little confusion here. Mass is a part of the equation. If we lessen the mass and apply the same power to it's accelleration it takes place faster.If the same engery is used and 'conserved' in the equation when mass is reduced,

accelleration (over a delta T ---- remember it's meters per second per second)

or velocity (moment-------meters per second) is increased to give the same value in a blunt expression. Variations of this sum occur according to round and round or linear motion but, pretty much thats what happens.

Tailshafts are hollow too, this means the outer edge contains the mass, the middle is air. Then there is the twisting forces on them which the flywheel doesn't have to cope with etc....

Propshaft wise it seems that there is more complicated equations involved than the simple approach we would taken. To save headaches on this thread I suggest that you email the guys at www.acpt.com they are the aerospace company that make the shafts for Mines and others.

All I can comment on is the experience I have had over the years making bits lighter and going faster as a result. The fact that people have trouble 'getting it' has meant I end up going quicker often in the same vehicle with less money spent and less power. Like people really ought to consider 'learning how to drive your car' as a mod of great value for money. This approach may have an up front cost but, it's free thereafter.

Extra power always costs you more for every second you use it.

Rev210,

I said that it is impossible to accelerate faster without increasing power…yes. BUT…we are talking about real power put down to the ground at any point in time. In theory, when you lighten something that the engine needs to accelerate in the torsional plane, you are wasting less energy, so can put more power to the ground. IE. This will be picked up on a dyno.

I wasn’t saying that the lighter prop shaft won’t have an effect. I was just saying that it won’t be anywhere near as much as that of a flywheel because it’s moment of inertia is so much smaller. I know the tailshaft is hollow, but assuming a radius of 30mm, then you could assume the average mass is 30mm from the axis (will actually be a bit less due the thickness of the material used). Now, Assuming a flywheel has a radius of 150mm, you could reasonable assume that the average mass is 100mm from the axis (I think this is exactly what it is, but I don’t have time to look for the formula, and it’s been years since I did it).

Of course, if you lighten the car, it will accelerate faster too. But the affects of lightened pullies on this are negligible. To be generous, say you can save 5kg. On a 1500Kg car, this 1/3 of a percent. It is the energy required to accelerate these items rotationally that makes the difference.

I didn’t disagree with you at all. Lightening things that accelerate in the linear plane will make them faster. And lightening things that accelerate in the torsional plane will make them accelerate faster by an even bigger degree. My point was that this power ‘increase’ will be able to be measure by a dyno.

[Roy]

What you are saying is absolutely correct, its basically 1st Year Mech Eng. But there is also another 1st year Mech Eng concept and that is the effect being negligible. Now I do think it would have an effect, but for the $1500 odd they would cost (curious to know the torsional strength as well) id want to be sure that it is a pronounced effect. $1500 in my eyes is a lot of coin.

If anyone know the dimensions of the two tailshafts its pretty simple to calculate the difference…ill work it when I get a minute over the weekend, see what the numbers say.

But gut feeling is the effect wouldn’t be that great as the radius is what 40mm or something. Id say its definitely at the “ive doen everything else, may as well give this a try “ end of the spectrum. But I I still say it would be interesting.

A point of interest, and I haven’t really formed an opinion, but when lowering the weight of the flywheel, the tailshaft etc etc, you are making it easier for the engine/drivetrain to accelerate…but you are also reducing the kinetic energy of things. So im curious to know how much more difficult are you making a powerful rwd car to get off the line, as there is reduced inertia so when the clutch is popped, wouldn’t it be more likely to bog down???? Like I said, its another aspect that on paper, the mass assists with kinetic energy, reducing the mass to nothing would be awesome for accelerating, but if you want to maintain a speed, or want to give it a punt off the line, ?!?!?!??!

[rev210]

We best leave the pocket book physics aside I think.

As I suggested earlier there is more physics involved than what we have been talking about. Especially the tailshaft. Mik you forgot to include the length of the tailshaft and the forces involved when trying to rotate it by one small area of the tip

Like I said, if you want to know more of the science ask someone who really knows (not me). I can tell you that for $2k you will be getting better bang for buck than some standalone mods for engine power of the same price. Remember that for the $2k you might spend on the engine power upgrade you will end up increasing the ongoing running costs of the car by a proportional amount to the power gain.

Now for a 'reality check'. This is the part where I give you some real world proof.

RE:Bogging down/launching:

Pro-stock drag cars are one example I can think of off the of of my head that use a carbon tailshaft,all the NHRA cars in the US run them because there is alot of money in the sport at that segment and above and therefore propper engineering behind that category The one instance locally can I remember in pro-stock (still sort of a thing backyard guys can do here in australia) a guy dropping time off his 60ft and overall et by switching to a carbonfibre unit, . Not exactly what you call bogging down at a 60ft of 1.06 and a 7.4 second 1/4mile.

Now for the GTR example; I can tell you that the inertia reduction is the ratio of (0.57:1.00). The center bearing is made redundant also making for a more instant power delivery to the rear axle.The GTR people who have actually fitted these things 'rave' about them even the ones who already have built engines with bucket loads of power, presumably because it compensates for the lag, however there are guys with hardly laggy setups with the same attitude.

Think again.

[Roy]

RE:Bogging down/launching:

Pro-stock drag cars are one example I can think of off the of of my head that use a carbon tailshaft,all the NHRA cars in the US run them because there is alot of money in the sport at that segment and above and therefore propper engineering behind that category The one instance locally can I remember in pro-stock (still sort of a thing backyard guys can do here in australia) a guy dropping time off his 60ft and overall et by switching to a carbonfibre unit, . Not exactly what you call bogging down at a 60ft of 1.06 and a 7.4 second 1/4mile.

Now for the GTR example; I can tell you that the inertia reduction is the ratio of (0.57:1.00). The center bearing is made redundant also making for a more instant power delivery to the rear axle.The GTR people who have actually fitted these things 'rave' about them even the ones who already have built engines with bucket loads of power, presumably because it compensates for the lag, however there are guys with hardly laggy setups with the same attitude.

Think again.

Ah interesting, but is it fair to be using supercharged big blocks when looking at launching/bogging down. We are talking completely different types of power deliveries...arent we. Im not beign argumentative, just bouncing ideas around. Its an itneresting point. The power delivery of an RB is worlds apart from a S/C BB

As for the GTR guys raving about the performance, cool. But again its a subjective measure. I have no problem believing they think there is a difference...but are there any tangible results showing performance gain? Any differences in circuit times, drag times etc?

LOL...as for pocket book physics...im not the smartest cat around...a long way from it. But the mechanics of what we are discussing is not that complicated. And normally the numbers speak volumes when it comes to making sense of changes. Like for instance the example you gave regarding GTRs running the carbon shaft. How much is the carbon shaft, and how much is the change from 2 piece to 1 piece?

LOL...give me a carbon shaft and im happy to trial it Ive got a data logger as my seat of the pants feel for things is pretty hopeless...the numbers dont lie like my gut does

ditto why im interested in this, as im curious to give these pulleys a go, just have to suss out the different belt types between GTST and GTR. Its not going to be overly expensive to give it a go, if the carbon tailshaft was only $150-200 more then the shaft i will be needing when i get an RB25 box, then i would gladly give one a go. In case it happens to yield reasonable imnprovement. But the new tailshaft will already be a one piece which talking to ppl that have done the RB25 gearbox conversion, they confirm what the GTR ppl you have spoken to have said about the 2piece to 1 piece tailshafts

[rev210]

Ah interesting, but is it fair to be using supercharged big blocks when looking at launching/bogging down. We are talking completely different types of power deliveries...arent we. Im not beign argumentative, just bouncing ideas around. Its an itneresting point. The power delivery of an RB is worlds apart from a S/C BB

As for the GTR guys raving about the performance, cool. But again its a subjective measure. I have no problem believing they think there is a difference...but are there any tangible results showing performance gain? Any differences in circuit times, drag times etc?

LOL...as for pocket book physics...im not the smartest cat around...a long way from it. But the mechanics of what we are discussing is not that complicated. And normally the numbers speak volumes when it comes to making sense of changes. Like for instance the example you gave regarding GTRs running the carbon shaft. How much is the carbon shaft, and how much is the change from 2 piece to 1 piece?

LOL...give me a carbon shaft and im happy to trial it Ive got a data logger as my seat of the pants feel for things is pretty hopeless...the numbers dont lie like my gut does

ditto why im interested in this, as im curious to give these pulleys a go, just have to suss out the different belt types between GTST and GTR. Its not going to be overly expensive to give it a go, if the carbon tailshaft was only $150-200 more then the shaft i will be needing when i get an RB25 box, then i would gladly give one a go. In case it happens to yield reasonable imnprovement. But the new tailshaft will already be a one piece which talking to ppl that have done the RB25 gearbox conversion, they confirm what the GTR ppl you have spoken to have said about the 2piece to 1 piece tailshafts

Roy,

You ask me a question and I'll try to answer .You wanted to know about drag racing and boggin down I only mentioned an example for that. The pro-stock example I mentioned that runs 7.40 is naturally aspirated 540cui via a tunnel ram and twin dominators, had a powerglide 2 spd. There are plenty of other racing categorys where carbon shafts are used exclusively, most competitive racing at a high enough level of engineering will see these in everything in that competition, from circuit 2L to NASCAR, forced induction and NA.

How many other racing categorys do you want me to meniton?

As for the GTR,Way back in Group A racing of the R32 internationally saw the use of carbon tailshafts in the pursuit of faster times. It's reduced inertia benifits are far greater in the circuit environment.

Mines didn't get a shaft put into their parts line up for subjective or bling factors (you can't even see the thing). Nor did the guys whack a carbon shaft into the Veilside Drag GTR for those reasons. They are only two profile companys with examples I know about there are probably alot more.

When I get around to installing mine I will do a dyno before and after detailing the time taken to accellerate to a given rpm in gear. I have seen info on this done with a flywheel and clutch change over to lighter weight and the results are quite impressive.

Something else to consider Roy is that the EL or later? ford falcon tailshafts are alloy and may be able to be cut down in length to suit you conversion, you would need to confirm the strength of these on the ford forums but, I have heard of someone utilising one on a smaller race car with good results some time ago. Sadly I can't remember where I saw it, perhaps google?

I am keen to help other owners get onto a good thing and equally keen to steer clear of money wasting. If you saw the state of my GTR you would know how much of a cheap bastard I am

[Roy]

Yeh im not saying you are wrong You have experience that i dont, so using you as a sounding board for some of the things i have thought about as being cons

You ask me a question and I'll try to answer .You wanted to know about drag racing and boggin down I only mentioned an example for that. The pro-stock example I mentioned that runs 7.40 is naturally aspirated 540cui via a tunnel ram and twin dominators, had a powerglide 2 spd. There are plenty of other racing categorys where carbon shafts are used exclusively, most competitive racing at a high enough level of engineering will see these in everything in that competition, from circuit 2L to NASCAR, forced induction and NA.

How many other racing categorys do you want me to meniton?

As for the GTR,Way back in Group A racing of the R32 internationally saw the use of carbon tailshafts in the pursuit of faster times. It's reduced inertia benifits are far greater in the circuit environment.

LOL... ok but its a powerglide and big atmo drag car...i suppose i should eleborate on whaty i thinking... say you have dialled up the revs for launching. The flywheel is storing a lot of energy, so when the cltuch engages the revs are less likely to plumet. So along with the ..ok answered my own problem here..check.

But i have read in racing/engineering journals (i know its not practical experience ) that part of the reason why cars like 2L Tourers, F1 cars etc etc, are to launch/get off the line is because of their peaky power delivery mixed with the the super light drivetrains. But for the scope of this i think i understand why this is now...and its not really anything to do with the driveshaft...how can it, its idle

Something else to consider Roy is that the EL or later? ford falcon tailshafts are alloy and may be able to be cut down in length to suit you conversion, you would need to confirm the strength of these on the ford forums but, I have heard of someone utilising one on a smaller race car with good results some time ago. Sadly I can't remember where I saw it, perhaps google?

Interesting to know...friend works at ION so he will be able to help me out iwht info.

I am keen to help other owners get onto a good thing and equally keen to steer clear of money wasting. If you saw the state of my GTR you would know how much of a cheap bastard I am

... try beign a tight ass with a R32 GTST