I just got back from 4 weeks gone and am diving back in.
Here's the axle deal: Axles come through-hardened (like a Strange alloy axle)
or induction-hardened (like an OE axle). The Rockwell on a racing alloy axle
will often be lower than on a production axle because racing axles are often
designed for drag racing where the axles need to give, or twist just a bit, to
survive a launch. Because they are softer all the way through, they can twist
further than an induction-hardened axle before they reach the yield (which is
the point at which they bend and do not return to their original shape). With
an induction-hardened or surface-hardened axle, there is a brittle outer shell
with a very soft core. The outer shell is where the strength is. However, the
hard shell can easily crack when twisted. Once it cracks, it's all over. The
soft core of the induction-hardened axle has very little strength. Materials
and tempering affect the point at which this becomes an issue.
The other factor in axle strength is diameter. When you say "a 31-spline axle
is stronger than a 28-spline axle," the real point is that the 31-spline axle
has a larger diameter throughout, and is therefore stronger. In the case of a
Ford 9-inch, the larger axle will generally also have a better bearing design,
which for land-speed racing, is probably more important (less roller-bearing
speed thanks to a larger surface.)
Here's another thing I'm not too sure about: Strange once told me that some
racing axles are not good for impact-loading perpendicular to the axle
centerline. That means hitting a pot-hole, like perhaps on a bad day at El
Mirage. So maybe an OE axle is a decent choice.
But here's what I'd do: Use aftermarket 35-spline axles (the same price as 31s
if you buy a centersection at the same time) that are gun-drilled for lightness
and that have nice, big bearings.
Still, most axle breakage comes from shock-loading under acceleration, and I
don't think that's an issue in LSR, even at Maxton. That's why Keith's
28-spliners have yet to hurl a tire into the gradstands.
DF
>>> "Keith Turk" <kturk@ala.net> 9/5/01 1:58:22 PM >>>
Okay....... Here is what I know....
28 spline axles in a 3200lb car are good to 200.445mph at Maxton ,they are
good to 205.878 mph at Muroc and 228.304 mph on the salt in a 3800lb
car....... Yes I am sure they will fail.... if you ever get any real
traction .... with large tires...that are VERY STICKY
I agree with Joe's comments on Bullet Proof..... yeah there are a ton
better axles out there and I am going to install a set this year.... BUT as
often as I swap gears and look at these axles.... I have NEVER seen the
slightest thing to tell me they are BAD AXLES.... I am swapping mine
simply to make the car more bullet proof.... not because I personally think
they will fail.... I don't.... I just expect a BIG number pass next year
and want the car to have Zero issues...
I know it's only my opinion.... but if your looking to spend money just to
spend it you have picked a right place.... but based on the real answer
here Bill....I honestly dont' think you need them.... we have run over
750 hp with 200+ of that coming from a Nitrous hit and never had the first
moments problem with these.
Keith
----------
> From: Joe Timney <joetimney@dol.net>
> To: ardunbill@webtv.net; land-speed@autox.team.net
> Subject: Axles
> Date: Wednesday, September 05, 2001 10:30 AM
>
> Bill,
>
> Both Strange and Moser make a good product. I have used both in customer
> cars for
> many years. From Street, Stock Eliminator, Comp Eliminator, Alky
> Dragster, Alky
> Funny car, LSR Racing. The only axles I have seen break were ones that
> should
> have been replaced...twisted from years of abuse, bad bearings that had
> spun on
> the hub, or badly bent housings. Or 28 spline axles!!!!! For a Ford
> rear, do not
> use 28 spline axles for anything but a little old lady car...they will
> break...only a matter of time!!! The 31 spline axles are fine for what
> you are
> doing.
>
> Mark Williams axles are absolutely superior to any on the market...but I
> wouldn't
> spend the money for them unless I was building a NHRA ProStock car.
>
> Personally, Moser is the best bang for your buck...they will make any
> bolt
> pattern, dual pattern if needed at no additional price. They will
> install the
> studs and bearings so you get a drop in assembly.
>
> joe
>
> ardunbill@webtv.net wrote:
>
> > Hi Folks, wanted to ask the veterans out there what the BEST racing
> > axles are for my 9" Ford. At the moment I have streetrod reworked
> stock
> > Ford (shortened, resplined 31 spline) ones in there and Flatlanders
> told
> > me they "might" eventually break sometime when locked and in a serious
>
> > racing application. If one breaks, it is "not good" because then only
>
> > one rear wheel will drive which could be hazardous at high speed from
> > the sudden steering effect.
> >
> > So, I need some custom-length superduty never fail axles as reliable
> as
> > the sun coming up in the morning, complete ready to shove in my axle
> > housings, studs, bearings, seals, retainers, etc. Your thoughts will
> be
> > appreciated. Final responsibility is mine. Ardun Bill
///
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