Aluminum driveshaft good for 800-900 hp?
05-13-2012, 12:24 AM
#23
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i dont know what are the gains from going alum, but when i got mine i weighted at my job and with all the packing and stuff it was 15 pounds, so im guessing the DS is around 10-12 lbs....it might seem not much of a difference on weight savings compared to other DS like CM driveshaft or steel...but when you have rotating parts even 2-3 pounds count.... when you take into account that it creates a rotating mass that can double the weight of the DS.... thats one of the advantages of the Alum and Carbon Fiber DS.
05-13-2012, 08:56 AM
#25
I have to disagree on that. Rotating weight is the most important weight to cut down on. So if you combine a lighter driveshaft with wheels/tires you'll see bigger gains vs that same weight on dead items of the car like carpet, seats etc. 30 lbs rotating weight > 30 lbs dead weight all day long.
05-13-2012, 10:04 AM
#26
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Just make sure it's a solid piece and do the upstaged yoke mentioned above. I run a mark Williams 3.5 accubond deal with chrome moly yoke. Pricey but worth every penny
05-13-2012, 10:38 AM
#27
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There is definitely a huge difference between rotating weight, unsprung weight and sprung weight!!
How much on a slower car, or non-max effort combination, I have no idea,
but there is definitely a difference that you will notice and it adds up!!
I do know at my level, we spend a lot of money balancing weight & strength.
We definitely play the bang for the buck game, when choosing parts like rods,
carbon fiber drive shafts, lightened gears/spools etc etc.
.
There is definitely a huge difference between rotating weight, unsprung weight and sprung weight!!
How much on a slower car, or non-max effort combination, I have no idea,
but there is definitely a difference that you will notice and it adds up!!
I do know at my level, we spend a lot of money balancing weight & strength.
We definitely play the bang for the buck game, when choosing parts like rods,
carbon fiber drive shafts, lightened gears/spools etc etc.
.
05-13-2012, 03:30 PM
#28
.
There is definitely a huge difference between rotating weight, unsprung weight and sprung weight!!
How much on a slower car, or non-max effort combination, I have no idea,
but there is definitely a difference that you will notice and it adds up!!
I do know at my level, we spend a lot of money balancing weight & strength.
We definitely play the bang for the buck game, when choosing parts like rods,
carbon fiber drive shafts, lightened gears/spools etc etc.
.
There is definitely a huge difference between rotating weight, unsprung weight and sprung weight!!
How much on a slower car, or non-max effort combination, I have no idea,
but there is definitely a difference that you will notice and it adds up!!
I do know at my level, we spend a lot of money balancing weight & strength.
We definitely play the bang for the buck game, when choosing parts like rods,
carbon fiber drive shafts, lightened gears/spools etc etc.
.
Go take a look at what people pick up going from a aluminum to a cf or even from a steel to a cf.
Driveshafts cannot be calculated in the same way as reducing weight out on the wheels or the brakes. Sorry, its been proven time and time again. Put some thought into where the weight is and how far the weight is out on the crankshaft centerline and you'll see why.
05-13-2012, 03:32 PM
#29
I have to disagree on that. Rotating weight is the most important weight to cut down on. So if you combine a lighter driveshaft with wheels/tires you'll see bigger gains vs that same weight on dead items of the car like carpet, seats etc. 30 lbs rotating weight > 30 lbs dead weight all day long.
05-13-2012, 05:17 PM
#30
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There's nothing to think about, people a lot smarter then you or me, and with a lot more experience
then both of us together have been proving it since the beginning of racing!!
Why do they pay triple for lightened cranks, why do they pay triple for titanium rods,
lighter D/S's, gears, wheels, bodies, etc etc.
Again, it's always been rotating weight, then un-sprung, then sprung!!
You also can't compare a 2 lb D/S difference, with a 50 lb sprung difference.
Like I said, it all adds up, but you must compare apples to apples.
.
There's nothing to think about, people a lot smarter then you or me, and with a lot more experience
then both of us together have been proving it since the beginning of racing!!
Why do they pay triple for lightened cranks, why do they pay triple for titanium rods,
lighter D/S's, gears, wheels, bodies, etc etc.
Again, it's always been rotating weight, then un-sprung, then sprung!!
You also can't compare a 2 lb D/S difference, with a 50 lb sprung difference.
Like I said, it all adds up, but you must compare apples to apples.
.
05-14-2012, 08:29 AM
#31
.
There's nothing to think about, people a lot smarter then you or me, and with a lot more experience
then both of us together have been proving it since the beginning of racing!!
Why do they pay triple for lightened cranks, why do they pay triple for titanium rods,
lighter D/S's, gears, wheels, bodies, etc etc.
Again, it's always been rotating weight, then un-sprung, then sprung!!
You also can't compare a 2 lb D/S difference, with a 50 lb sprung difference.
Like I said, it all adds up, but you must compare apples to apples.
.
There's nothing to think about, people a lot smarter then you or me, and with a lot more experience
then both of us together have been proving it since the beginning of racing!!
Why do they pay triple for lightened cranks, why do they pay triple for titanium rods,
lighter D/S's, gears, wheels, bodies, etc etc.
Again, it's always been rotating weight, then un-sprung, then sprung!!
You also can't compare a 2 lb D/S difference, with a 50 lb sprung difference.
Like I said, it all adds up, but you must compare apples to apples.
.
I hate to tell you this, but you're wrong, or at least being a little too defensive. The crank, not even looking at it as an internal engine component, has more rotational weight away from the crank centerline than a DS. same for the rods by a long shot. ?LOL at trying to compare the two to a DS....
You're glossing over something and completely missing the point I'm making. Which is the weight of a driveshaft is a negligble loss in weight in rotational weight vs downstream components....like a wheel...or brakes... It's relatively simple if you look at it open minded and not so "IT HAS TO MAKE A DIFFERENCE!!! IT'S LIGHTER!!!"
I didn't say it didn't, but i will say the difference is almost negligble in most setups. If there is a difference, I'd bet the improvement in harmonic vibration from a CF or AL driveshaft is where it comes from more than anything.
I would bet a stock smaller DS would be "faster" than a big/fat DS that might be marginally lighter. Of course, that's assuming that you could get it to live. Irregardless, I'm betting unless you have an incredibly consistent car....to the .005, that you couldn't realistically see the results.
read what i'm saying here: if you go from a 30 lb DS to a 20lb driveshaft...you lost 10 lbs...which is great. but i wouldn't look at it the same as rotational weight out on the wheels. losing 10lbs of rotational weight 2" away from the axis of the crank centerline doesnt mean ****.
05-14-2012, 08:36 AM
#32
another thread that may find a post i made useful.
here are a couple links that will describe these concepts better than my primitive understanding.
http://hpwizard.com/rotational-inertia.html
the above link has calculators that may be of some use.
using their calculators and assuming a 10lb difference in 5" diameter the difference when compared to static weight is only ~ 10.4lbs; 1.04 ratio.
this next link takes the potential saved energy by using lighter driveshaft and converts to horsepower.
http://www.w8ji.com/rotating_mass_acceleration.htm
this following is quoted from the aforementioned link.
"The original driveshaft weighed 30 pounds and we had to spin it to 6000 RPM. If we input that, we see it consumed (and stored) 5310 joules. 480 ounces in a 3.5 inch diameter RING (hollow center) and 6000 RPM.
That is 5310/746 = 7.12 horsepower-seconds to spin the shaft to 6000. Since the time was 13 seconds, the shaft soaked up 0.548 horsepower distributed over that 13 seconds.
Now we change to the aluminum shaft. Everything is the same except the weight, it is now 15 pounds or 240 ounces. Using that flywheel calculator we find we used 2655 joules. This is 2655/746 = 3.56 horsepower-seconds. Over 13 seconds, we "stored" .274 horsepower. The net gain in available energy over 13 seconds was about 1/4 horsepower."
another link some may find useful
http://hyperphysics.phy-astr.gsu.edu/hbase/mi.html#mi
here are a couple links that will describe these concepts better than my primitive understanding.
http://hpwizard.com/rotational-inertia.html
the above link has calculators that may be of some use.
using their calculators and assuming a 10lb difference in 5" diameter the difference when compared to static weight is only ~ 10.4lbs; 1.04 ratio.
this next link takes the potential saved energy by using lighter driveshaft and converts to horsepower.
http://www.w8ji.com/rotating_mass_acceleration.htm
this following is quoted from the aforementioned link.
"The original driveshaft weighed 30 pounds and we had to spin it to 6000 RPM. If we input that, we see it consumed (and stored) 5310 joules. 480 ounces in a 3.5 inch diameter RING (hollow center) and 6000 RPM.
That is 5310/746 = 7.12 horsepower-seconds to spin the shaft to 6000. Since the time was 13 seconds, the shaft soaked up 0.548 horsepower distributed over that 13 seconds.
Now we change to the aluminum shaft. Everything is the same except the weight, it is now 15 pounds or 240 ounces. Using that flywheel calculator we find we used 2655 joules. This is 2655/746 = 3.56 horsepower-seconds. Over 13 seconds, we "stored" .274 horsepower. The net gain in available energy over 13 seconds was about 1/4 horsepower."
another link some may find useful
http://hyperphysics.phy-astr.gsu.edu/hbase/mi.html#mi
An excellent read. I don't know about you, but if you can see less than 1hp on your timeslip...you're better than me!
while we are discussing driveshafts, DS size is also something to consider. this relates to my point on weight away from the crank centerline or axis: from Bill Edgeworth on classracer.com:
I don’t think you can really make a blanket comparison between steel and aluminum drive shafts. Beneficial to some not to others, there is a lot of things to consider when swapping them out and seldom are the new and old physically comparable. One would first think that if its lighter it will take less energy to accelerate… well not necessarily if you take a small diameter steel shaft and replace it with a lighter large diameter shaft.
Here is an example
7000 rpm a 3” shaft will have a surface speed of 5498 feet per minute
7000 rpm a 4” shaft will have a surface speed of 7330 feet per minute a 33% higher speed
Using basic physics equations like Ke=1/2mv^2 if they weigh the same and most of the mass is in the tube not the end yokes the 4 inch shaft will take roughly 78% more energy to accelerate to 7000 rpm.
If you do all the math the 4” shaft would have to be about 40% lighter to take the same amount of energy to accelerate as the 3” shaft.
What this exercise shows is that most comparisons are apples to oranges you probably won’t see any gains unless you are replacing your current shaft with something lighter and the same or smaller diameter.
And this is without taking into consideration what’s going on in the rest of the car.
Here is an example
7000 rpm a 3” shaft will have a surface speed of 5498 feet per minute
7000 rpm a 4” shaft will have a surface speed of 7330 feet per minute a 33% higher speed
Using basic physics equations like Ke=1/2mv^2 if they weigh the same and most of the mass is in the tube not the end yokes the 4 inch shaft will take roughly 78% more energy to accelerate to 7000 rpm.
If you do all the math the 4” shaft would have to be about 40% lighter to take the same amount of energy to accelerate as the 3” shaft.
What this exercise shows is that most comparisons are apples to oranges you probably won’t see any gains unless you are replacing your current shaft with something lighter and the same or smaller diameter.
And this is without taking into consideration what’s going on in the rest of the car.
Last edited by tim99ws6; 05-14-2012 at 08:53 AM.
05-14-2012, 09:19 AM
#33
And this is what makes drag racing a sport. People having different opinions on what makes a car faster. If everybody thought the same exact things then everyone's car would run the same. This is why I love seeing everyone's set-ups and seeing how they got to their ET.
05-14-2012, 10:26 AM
#34
So it's win-win for everyone here to run the 3.75" PST carbon shaft!
I run one, Mark Koehler just switched to one from a MW cm, and several other of our customers.
What we have seen is the harmonics of the steel shaft in the f-body cars tends to be a bigger issue more than the weight savings or parasitic gains. The factory put aluminum shafts with a cardboard liner inside to absorb vibes that a similar cm or steel shaft won't. The point of resonance between the two materials is the difference and it is a known fact that these cars are better off with an aluminum shaft and even better with a carbon. Carbon shafts have the highest critical speed spec of all of them.
The carbon shafts are much safer as well. If a steel or aluminum shaft fails the parts become flying shrapnel and have the potential to come through the floors. If a carbon shaft fails it will just turn to fabric.
So... who's ready for a nice carbon PST shaft? MWC has the best deal for you guys on any shaft from Strange or PST. Give me a call!
I run one, Mark Koehler just switched to one from a MW cm, and several other of our customers.
What we have seen is the harmonics of the steel shaft in the f-body cars tends to be a bigger issue more than the weight savings or parasitic gains. The factory put aluminum shafts with a cardboard liner inside to absorb vibes that a similar cm or steel shaft won't. The point of resonance between the two materials is the difference and it is a known fact that these cars are better off with an aluminum shaft and even better with a carbon. Carbon shafts have the highest critical speed spec of all of them.
The carbon shafts are much safer as well. If a steel or aluminum shaft fails the parts become flying shrapnel and have the potential to come through the floors. If a carbon shaft fails it will just turn to fabric.
So... who's ready for a nice carbon PST shaft? MWC has the best deal for you guys on any shaft from Strange or PST. Give me a call!
05-14-2012, 10:29 AM
#35
So it's win-win for everyone here to run the 3.75" PST carbon shaft!
I run one, Mark Koehler just switched to one from a MW cm, and several other of our customers.
What we have seen is the harmonics of the steel shaft in the f-body cars tends to be a bigger issue more than the weight savings or parasitic gains. The factory put aluminum shafts with a cardboard liner inside to absorb vibes that a similar cm or steel shaft won't. The point of resonance between the two materials is the difference and it is a known fact that these cars are better off with an aluminum shaft and even better with a carbon. Carbon shafts have the highest critical speed spec of all of them.
The carbon shafts are much safer as well. If a steel or aluminum shaft fails the parts become flying shrapnel and have the potential to come through the floors. If a carbon shaft fails it will just turn to fabric.
So... who's ready for a nice carbon PST shaft? MWC has the best deal for you guys on any shaft from Strange or PST. Give me a call!
I run one, Mark Koehler just switched to one from a MW cm, and several other of our customers.
What we have seen is the harmonics of the steel shaft in the f-body cars tends to be a bigger issue more than the weight savings or parasitic gains. The factory put aluminum shafts with a cardboard liner inside to absorb vibes that a similar cm or steel shaft won't. The point of resonance between the two materials is the difference and it is a known fact that these cars are better off with an aluminum shaft and even better with a carbon. Carbon shafts have the highest critical speed spec of all of them.
The carbon shafts are much safer as well. If a steel or aluminum shaft fails the parts become flying shrapnel and have the potential to come through the floors. If a carbon shaft fails it will just turn to fabric.
So... who's ready for a nice carbon PST shaft? MWC has the best deal for you guys on any shaft from Strange or PST. Give me a call!
This post is spot on! I'll take one. Feel free to ship it on down. You have my address..
05-14-2012, 12:48 PM
#36
I think what Tim is getting at is that there are more crucial areas that we could focus on that will net more gains. Often ignored are axles, ring gears, differential carriers, transmission planet carriers and engine internals. Your common guy isn't going to think about that kind of stuff because it's hard to access and lighten, but there is a lot more inertia stored in a lot of those items than a driveshaft due to larger diameter and/or the weight being placed along the circumference of said items. Reduction of rotational mass almost never gets us anywhere one component at a time, but when you have a complete lightened package, you can get recordable results.
05-14-2012, 01:31 PM
#37
Screw a PST drive shaft!!! You couldnt pay me to run of those pieces of crap again. Mine broke on the first launch taking out my brand new transmission, exhaust, brakes, and rear end. Had a driveshaft made locally out of DOM tubing and never looked back.
PST had nothing but excuses on why it broke blaming the car. Well 5 years later hundreds of passes later never had a single issue, safe to say it wasnt the car.
PST had nothing but excuses on why it broke blaming the car. Well 5 years later hundreds of passes later never had a single issue, safe to say it wasnt the car.
05-14-2012, 02:06 PM
#38
Well personally I asked is because I already have lightened wheels, spool, gears, brakes etc etc and want to keep on the path I'm shooting for so I wanted to make sure they are good to use. But I agree, one component isn't gonna set the world on fire but in my case everything I bought so far was light weight so my end result will net better gains vs. your typical bolt-on car with one. Thanks guys
05-14-2012, 03:01 PM
#39
Well personally I asked is because I already have lightened wheels, spool, gears, brakes etc etc and want to keep on the path I'm shooting for so I wanted to make sure they are good to use. But I agree, one component isn't gonna set the world on fire but in my case everything I bought so far was light weight so my end result will net better gains vs. your typical bolt-on car with one. Thanks guys
05-14-2012, 03:31 PM
#40
I totally understand what your saying however I need to buy a driveshaft, not upgrade mine so at this point in my build I'll buy one now. If I already had a CM one then no I wouldn't buy it. Plus not to mention that other 10 lbs you speak of would help out even more on top of a lighter driveshaft lol.