Cascade Crew

[blue89]

I'm having a discussion with a nissan oriented friend. He gave me the link http://www.amsperformance.com/store/index.php?cPath=24_60_308 where it says that the aluminum driveshaft will flex 20* while the steel flexes 5-7*.

Is this correct? I just can't come to terms with this. Seems like the aluminum would twist the same if not less, but have less elasticity causing failures. Woudn't Carbon Fiber driveshafts be even worst? Stronger, but way less elastic?

[Dewey316]

Not enough information to say. If they gave test specifics, temp, alloy, etc. Where did it twist, what is the wall thickness, etc.

Sure alum will "bend", some alloys more than others.

Check out http://www.matweb.com you should be able to look up most of the specs on the diffrent metals, but that won't inlude design diffrences between the driveshafts in question.

Just for comparison
6060 Alum. (which it says the alum shaft is made of) has a Module of Elasticicy of about 69 GPa. Steel should be in the 200-220 GPa (it will depend on the carbon content, etc along with the heat treatment and so on.

So based on that number along, at the same force the alum will deflect much more.

GPa is actualy the ammount of force needed to "bend" it a certain amount. Given those numbers it isn't "unreasonable" to say that if steel bends 7* that alum would bend 20*.

But without better data it is very hard to say. That is just what the information says. on Matweb they have lots of bending to yeild data and such on the diffrent metals.

--John

[blue89]

Thats what I was thinking. I personally would not want a driveshaft that flexed 20*!!!! I also noticed that even though it says aluminum flexes 20*, it states in the paragraph below that "if your looking for that extra snap to DRIFTING "........ what extra snap? They just stated that the aluminum shaft twists 400% MORE than the aluminum. Silly ricers.

[Dewey316]

I edited and added more and you replied while I was doing that...

--John
(where is qwktrip at, he might have more insite as to which material information would be more accurate for a twisting type of test, as he is the degreed engineer of the group. I'm going over to my Parents tonight, all chat with my Dad (PE, structural, with a ton of steel design work), and my Brother (senior civi student). They may be able to give more info what data to look for on matweb.)

[91RSVert]

I found that my 2.5" steel shaft only weights 1lb more then the 3" LS1 aluminum shaft. Not worth my money.

I do wonder what I CF shaft would do, hum.

[blue89]

Aluminum
69 GPa
.0975lb/in^3

Steel
220 GPa
.284lb/in^3

So aluminum is 3 times lighter and weaker than steel. This COULD explain how they put 20* and 5-7* for the twisting. But if the steel driveshaft weights in at 15lbs and the aluminum at 11lbs, that means they put almost twice the thickness of aluminum as steel in there. 15/.284=52in^3 of steel and 11/.0975 = 112.8in^3 of aluminum! 112/52 = 2.15 so the 69GPa of aluminum times 2.15 would be almost 140GPa. So maybe it should only deflect twice the steel counterpart.

Still sounds like their part description is inaccurate.

[Xophertony]

the Aluminum shaft is not the same physical diameter as the steel shaft. in addition to being thicker (maybe?) it has a much wider diameter.

[redlava]

Aluminum is a lot weaker then steel yes, but aluminum will not deform as much as steel it will just crack. Where as the steel will be the one to deform. For example if you put the 2 different drive shafts to a machine and twisted the drive shafts. The aluminum would break with out deforming and the steel would deform greatly before braking.

[Twilightoptics]