Hi Robert-
Am I right to presume that you've run no damper? With your shift point,
your crank should last for years on a standard 2.5 litre damper. BEWARE of
late 2 litre dampers #154380 - available NOS for pin money - these play hell
on 2.5's. You can machine the outside diameter of #214479 to take a crank
trigger ring, but you'll really need a good original part - the repro items
don't seem to have enough thickness of elastomer to cope with the shearing
forces, and tend to fail early.
Also, if you need to regrind a crank, be certain that the radii are
perfectly formed as original- I've just had to junk a crank that a customer
paid someone #400 for that has virtually no radii left, thanks to careless
machining. If you're on a short snout crank, you should be able to find a
NOS #311322, or Tuftride & polish a mint original.
Float on the drive shaft: the shaft is the same length on every TR, O/D or
not. Only on the Herald/Spit & derivatives does it vary. I think as long as
you've enough plunge to clear the the gearbox tailflange when it's gearbox
out time, it's OK.
Finally, at the RPM's you mention, I don't think there's any problem with
water pump speed &c.
Hope this is of some help - if you're building a new motor for big RPM,
then the special kit is necessary BTW.
Regards
Jon
----- Original Message -----
From: "Robert Dardano" <19to1tr6@comcast.net>
To: "A.J.Wood" <wood@dandrade.freeserve.co.uk>
Sent: Friday, September 26, 2003 3:40 AM
Subject: Re: 6-Cylinder crank damper
> Hi Jon just busted the crank in late Aug and I am done for the season and
> starting a rebuild I would like to use a crank fire ing. Will your kit
work
> with that.I have run the motor with only a 3" dia aluminum pully. (24
> events = 3 seasons ) My shift points are low buy most standards 5500 to
6000
> On a chassie dyno I was making 150 hp 152 tor. at 5500. I shortened the
> drive shaft with this motor because I went to an A type OD but also
because
> I had to move the motor back because the pully was so close to the front
> cross member . How much float should I have on the drive shaft ? And can
> you tell me a little more about your kit, what it consists of and
thanks
> rob
> ----- Original Message -----
> From: "A.J.Wood" <wood@dandrade.freeserve.co.uk>
> To: "friends of triumph" <fot@autox.team.net>
> Cc: <kaskas@cox.net>
> Sent: Thursday, September 25, 2003 7:23 PM
> Subject: 6-Cylinder crank damper
>
>
> > Amici-
> > Thank you for the enquiries - briefly, we suffered a major failure on
a
> new
> > steel crank after only 4 hrs track time, several years ago, and decided
> that
> > something needed done.
> > After some research, we found that there is a problematic 3rd harmonic
> > torsional vibration on pretty much any inline 6-cylinder motor. The
> 6-cylinder
> > Triumph motor is especially susceptible since the crank has hardly any
> overlap
> > on the journals, hence is "floppy", for want of a better term. At 7200
> rpm,
> > the crank is twisting itself into a frenzy; the original elastomer
damper
> > cannot cope with the forces, so something has to give way. The first
> victim is
> > the flywheel, normally as a result of an early downshift, leading to
> failure
> > of the flywheel fasteners. So we go 8 bolts, dowels & so on. The
flywheel
> then
> > stays on. Then the rotor arm fails. Then the cam drive falls to bits in
> > various ways - cam sprocket drops off with the snout of the cam, or, in
> > extremis, the chain breaks - seen it , it's true!. The tensioner
smashes,
> and
> > even valve springs start to fail. I've seen one motor where the engine
> > backplate decided to part company with the engine.
> > OK - it's ad break time - my kit allows either original or billet
cranks
> to
> > rev through the critical rev point without risk of destruction. It's
easy
> to
> > fit, but the motor needs to go backward in the frame by around 10mm, and
> > there's some adjustment of pulley offsets to do. If you're unlucky, you
> got a
> > long drive shaft, which'll need shortening by a bit. Most are OK. Kit
> costs
> > #525 - I will be able to reduce this to FOT if we get a few orders.
Steel
> > crank = $3000 minimum - I think it's worth it, due to lack of collateral
> > damage...
> > Final puff- the TR-6 I drove at Mid-Ohio, which set fastest lap of
the
> week
> > (with a fat rusty old tub behind the wheel), has a standard, unlightened
> crank
> > in it, wearing said kit. The telltale said 7*00..
> > Please e-mail or whatever - I already posted the flywheel bolt specs &
> so on
> > a while back.
> > Roll on VIR!!
> > Jon Wood
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