the 370z comes with a CF dshaft stock - it has no rock/debris shield and no heat shield and is located in close proximity to the exhaust thats from minivan who has one
Hmmm I just got a 1 piece aluminium driveshaft from Z1 thought these would be ok, spose to be just as strong as the stock ones?
To explain the heat thing a little for those that don't know/understand: When a carbon fibre composite part is made the resin needs to be cured at a given temperature for a given period of time. These temperatures and times vary depending on what the part is to be used for & its size etc. Once the curing process has been completed the part will achieve its designed strength at the proposed operating temperatures. It is critical for the strength of the part to not exceed a certain temperature that will normally be just under the curing temperature used, if the temp is exceeded the resin will loose strength and the component will begin to fail. These temperatures are normally surprisingly low as an example most modern light aircraft using carbon fibre components are limited by ambient air temp & are not allowed to fly if the air temp exceeds a given value (~ 40 degrees c in some cases). Temperature is so critical that care has to be taken when choosing paint schemes for the craft, some parts can only be painted white to avoid the extra heat that would soak in from being a dark colour such as black. Lets hope these guys have been curing these shafts at some fairly decent temps....
They wont be as strong as a stock one I can guarrantee you that. To be as strong as a steel shaft the walls of the alloy pipe would have to be 2 1/2 times as thick. Same as CARBON fibre. Carbon fibre is used for a lot of things NOT cause its as strong as steel, but becxuase it is VERY stiff. It isnt very elastic in fact the matrix of carbon and resin will allow only a very small deflection before it fractures. Carbon fibre isnt any stronger than say Fibreglass weight for weight BUT it is about 5 times stiffer. This is why weight for weight Steel is pretty damn good. A carbon drivshaft made at the same weight as a steel one will be a lot stiffer but there isnt much point seeing you are changing it to save weight. Steel = very strong shaft, quite elastic, will deform and recover very well before stresses are enough to briung about failure. Uni cups very firmly bonded to the shaft. Aluminium= (same thickness as the steel one) quite strong but not as strong as steel ( by about half) quite elastic but elastic limit will be reached much quicker than steel. To reach strength levels of steel tube wall thickness needs to be 50% greater negating much of the point of getting it lighter. Uni yoke must be alloy for decent fixing therfore not as strong as steel. Carbon Fibre= To reach same deflection strength as Steel the tube thickness would have to be 50% thicker than Steel. Minimal elasticity to absorb shock loads causing delamination of the matrix and failure. Extra thickness brings extra weight defeating some of the advantages. Difficulty bonding Uni Yokes to the carbon matrix causes stress risers at the ends. Post curing of cloth and resins in an autoclave increases strength but cannot enhance shock loading abilities.
why would you bother with a carbon fiber tail shaft if it has come to that , that the last thing weighting you down and your going to spend 1000 on it your mad
Just a few further points about using Carbon fibre. Carbon fibre is VERY good at applications where the fibres are in tension ( stretched) it is very POOR at applications where it is in compression. ( pushed inwards from the end of a fibre) The consequence of this is that in environments where there is a HUGE torsional load such as a drive shaft The majority of the weight of carbon cloth used in construction needs to be laid with a 45degree bias. This gives greater torsional strength but at any one time under acceleration only 50% of the fibres that are in tension are taking a majority load. Those that are in compression are not carrying their fair share. Under deceleration the opposite occurs and the fibres reverse roles with alternate fibres in tension and compression. Therfore to have a strong carbon matrix in these applications you need 50% more cloth to accomodate this NON linear sharing of load. Also to enhance the longtitudinal strength there will be quite a few carbon tows ( unidirectional cloth with all the carbon running one way ) added along the drive shaft to give it a bit more stiffness lengthwize. In all Carbon ISNT the be all and end all for a tail shaft application with large torsional loads without a much greater weight of material than you would think should be used. Stiffness ISNT strength! BTW Mungy's post is right on the money. Dont see many dark coloured composite planes for a reason. Unless a resin/carbon matrix is post cured the likely resin failure temp is around 140C depending on the resin used. Catalized epoxy resins begins to loose their ability to continue at its room temp strength at approx 60-80 degrees C, slowly increasing to failure at around 150C. The only way to get around this is to use prepreg material which has a much higher temp rating but are hard to use with an autoclave and other specialized equipment required.
Emailed PST regarding heat and C/F Shaft this was the reply: Rob, Yes, you need to protect the bond at the ends of the shaft from heat, there are several wraps that you can use. Mark
That is a worry. SO they are worried about radiant heat from the exh system at ~ 1m from the engine... what about the heat that eventually transmits through the gearbox and directly into the universals/yokes !? Glad I don't have a CF shaft feel a little worried for those that do
well the thing is ,, its more the money i would say , and the inconvenience of it breaking on you , and where , ( away from home ) . Well now that this has come to our attention , maybe people with C/F tail shaft's will take note and see what they can do to prevent this from happening to them , lets put it this way, i would rather see a C/F one break then a metal one , i can tell you that now . so either way for me , if Chris was going to break one, i would rather he break the C/F all day ,
well the bonded ends aren't close enough to the exhaust (gearbox & diff seperates the exhaust ) and I dont think the heat from gearbox is the hot enough to do damage. any C/F tailshaft I've seen broken is in the middle not the ends (probably from side impact)
Can we now expect an enormous outcry/witch hunt from outraged potential customers, for "honesty and truth"?
nah ... just whack 27 disclaimers on it ...... ... or, alternatively wrap it in a heap of tunnel vision ...
Heat does effect carbon fibre, was told this with my motorbike exhaust, it would severely impact the life and strength of it so keep it / park it out of the sun.
Good analogy Mungyz, I was going to make the same one myself particularly with light aircraft such as the Sting etc. What are your thoughts on the new Boeing 787's and their use of upto 80% carbon fibre in overall construction? ?50% carbon-fiber composite, in the fuselage, wings, tail, and interior components ?20% aluminum, primarily on the wing and tail leading edges ?15% titanium, primarily in the engines ?10% steel ?5% other materials By volume, carbon-fiber components make up 80% of the 787 Dreamliner.
