[v12-engine] Crankshaft damper

V12-Engine
1

My damper is still in good shape.
I have been looking at it while rebuilding the spare HE engine.

Going off at a tangent to organise a cheaper form of chain tensioner halfway
through the rebuild slowed things down.
The final tensioner parts ordered from the machinist should be delivered
next week and then there is work to make a welding jig.
Hopefully the rebuild kit will be ready about 5 weeks from now.

The HE block has the crank and pistons fitted, but since it is needed to
check the fit of the tensioner kit, the rebuild is in limbo for a while.
It pains me to look at the enormously heavy damper and pulley arrangement.
Lots of weight, gets in the way when working under the front of the engine,
and probably impedes radiator airflow to some extent.

Substituting an electric pump in place of the OEM mechanical one, only 3
belts are needed now, so it might be possible to turn off one belt groove
and get weight down.
More adventurous is the idea of using one multigoove belt to drive
alternator, aircon and PS pump, with a self adjusting adjustor.
That would clean up the front of the engine in a big way

The main problem here is the crankshaft damper. I have a sample mutigroove
pulley and damper from a Holden 3.6 litre V6 engine, which is a GM import
from the U.S. That has much less weight, but the pulley diameter is greater
and that gives more moment of inertia per kg than the Jag item, and it is
( I think ) the moment that more effectively dampens. The GM unit has a
straight bore and keyway which is smaller then the V12 crankshaft, so that
is a challenge. Boring the GM to size is feasible, but slotting for a
keyway is more tricky.

Then again, there is that complicated cone arrangement on the V12
crankshaft. The cone is, or was, no cheap part to manufacture so it must be
there for a reason. I can’t see the reason, so if anybody has a theory let
it rip.
Somebody told me there is a company in Melbourne can rework dampers by
injecting new rubber. I have not had time to follow this up; maybe they
only deal with common dampers they have tooling for, or maybe they can fix
up a one-off with no tooling needed.
If a one-off can be done, then I can cut up the old V12 arrangement and use
the tapered bore and adapt/fabricate other parts to finish up with what is
needed.

A crucial question is how exact is the design of a damper. A web search did
not help much . The best site just showed examples of an undamped
crankshaft mounted between knife edges ringing like crazy when hit with a
hammer, then not ringing when a suitable damper is bolted up to it. Perhaps
the damper is a seat of the pants issue and not designed to a strict
formula. Does anybody know ?

Richard Dowling, Melbourne, Australia, 1979 XJ-S & 1985 XJ6.

Visit the Jag Lovers homepage at http://www.jag-lovers.org for exciting services and resources including Photo Albums, Event Diary / Calendar, On Line Books and more !

2

In reply to a message from Richard Dowling sent Thu 28 Apr 2005:

Taper fittings are very common in industrial applications.
They do not slip at all, are quick and easy to assembly and
take apart. Look up Dodge Bearing, Browning, or Martin for
‘‘Taper Lock’’ or ‘‘QD’’ bushings for examples. You may even
find that the Jaguar crank taper is similarly sized to a
standard taper lock bushing.

Any reasonably copmpetent machine shop should be able to
broach a key slot. A really competent shop should be able to
turn the taper to mate up with the crank.

I’m sure there is a whole science devoted just to harmonic
balancers. I would be affraid to arbitrarily modify the
dampening characteristics of a proven design. You will not
see the ill effects of misapplication immediatiely and bad
results will be expensive and probably deadly to the engine
as you wipe out bearings here and there.

Using a crank pulley larger than design will affect the
drive ratios of all the belt driven accessories attached to
it. The alternator won’t like that but maybe the other items
will be OK with it.

Electric weater pumps would be a real neat addition to these
cars. Davies-Craig makes one as well as EMP-Stewart. The key
to these is how you control it. You may even be able to use
two small pumps and eliminate the thermostats entirely, or
including an electric thermostats would put you on the
cutting edge of cooling system design for a concept
unchanged in 100 years.

I goota run, the granddaughter is off to school!–
The original message included these comments:

It pains me to look at the enormously heavy damper and pulley arrangement.
Substituting an electric pump in place of the OEM mechanical one, only 3
belts are needed now, so it might be possible to turn off one belt groove
and get weight down.
More adventurous is the idea of using one multigoove belt to drive
alternator, aircon and PS pump, with a self adjusting adjustor.
The main problem here is the crankshaft damper. I have a sample mutigroove
pulley and damper from a Holden 3.6 litre V6 engine, which is a GM import
from the U.S. That has much less weight, but the pulley diameter is greater
and that gives more moment of inertia per kg than the Jag item, and it is
( I think ) the moment that more effectively dampens. The GM unit has a

–
Joe Bialy, ’ 87 XJ-S & '94 XJ-40
Grosse Ile, Michigan, United States
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–
–Support Jag-lovers - Donate at http://www.jag-lovers.org/donate04.php –

Visit the Jag Lovers homepage at http://www.jag-lovers.org for exciting services and resources including Photo Albums, Event Diary / Calendar, On Line Books and more !

3

Then again, there is that complicated cone arrangement on the V12
crankshaft. The cone is, or was, no cheap part to manufacture so
it must be
there for a reason. I can’t see the reason, so if anybody has a
theory let
it rip.

I assume it’s to increase the grip between the pulley and the crank,
using the principle of the incline… i.e., a little axial compression
produces a lot of radial force due to the cone shape.

A crucial question is how exact is the design of a damper. A web
search did
not help much . The best site just showed examples of an undamped
crankshaft mounted between knife edges ringing like crazy when hit with a
hammer, then not ringing when a suitable damper is bolted up to
it. Perhaps
the damper is a seat of the pants issue and not designed to a strict
formula. Does anybody know ?

I would guess that vibration control is one place where analytical design
is at its best. From what I know about the subject, in vibration
it’s not just the mass (moment for rotational systems) but also
the stiffness and friction (damping) that determines
the critical frequencies and amplitudes. Design to avoid severe
vibration amounts to adjusting these three parameters so that the
critical frequencies are outside the expected operational envelope.

There is an old story told by professors teaching this subjects. At the
center is a famous engineer/scientist (whose name I can’t remember) who
is called in to solve a vibration problem on a turbine/generator at
a new power plant. He studies it for a day or so, then pulls a piece
of chalk out of his vest pocket and puts an X at a spot on the
rotating assembly. He says “drill a 2” diameter hole 3" deep right there."
They do that and the problem goes away. He sends his bill to the accounting
department for $1000, but it is returned with a note asking for itemization.
He sends back a new invoice that says:

Chalk: $1.00
Knowing where to put it: $999.00

Ed Sowell
76 XJ-S
http://www.efsowell.us/ed/myJag.html

Visit the Jag Lovers homepage at http://www.jag-lovers.org for exciting services and resources including Photo Albums, Event Diary / Calendar, On Line Books and more !

4

In reply to a message from Richard Dowling sent Thu 28 Apr 2005:

Richard,
I had my V12 damper overhauled (rerubbered) through XJ Auto spares
in Sydney (02 9631 4600). They also supply exchange units.

They did a nice job, and it works well.–
The original message included these comments:

Somebody told me there is a company in Melbourne can rework dampers by
injecting new rubber. I have not had time to follow this up; maybe they
only deal with common dampers they have tooling for, or maybe they can fix
up a one-off with no tooling needed.

–
Colin Kennedy E-TYPE SIII ROADSTER
Sydney N.S.W., Australia
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–
–Support Jag-lovers - Donate at http://www.jag-lovers.org/donate04.php –

Visit the Jag Lovers homepage at http://www.jag-lovers.org for exciting services and resources including Photo Albums, Event Diary / Calendar, On Line Books and more !

5

Hi Richard,

The company in Melboune (can’t remember name) quoted me around AUD500 to
rebuild my existing damper or they would fabricate a new “race” one using
their various technologies. Unfortunately the taper fitting presented a
problem and they were talking of a couple of thousand dollars for a one off.
They did recommend using a small block Chev or something and machining the
taper. They also had one with a belt which you could add a taper to. I
didn’t ask them about mass, although someone else has mentioned that it is
more to do with stroke, that vibration is not a problem with short stroke
V12’s but is more an issue with 84mm+ conversions. Warning - this is all
heresay. I am looking more into this myself. Looking at the TWR V12 race
engines, there appears to be almost no damper there at all. There is also an
interesting article in the latest Race Car Engineering which seems to
challenge a lot of previous assumptions about “normal” dynamic balance of an
engine.

I am planning to run dual electric water pumps, one into each bank, with
independent thermal controls. I’ll let you know how I get on. Also, I am
considering running the water into the heads and then out the block. Apart,
perhaps, from bleed issues, this would appear to offer an advantage in that
the coolest coolant works against the hotest part of the problem. I will
probably eliminate the front water pump entirely as well as the second
damper pulley.

Because I am running a dry sump, this cleans up the front of the engine
nicely and all I have is an alternator off the damper and a cogged belt in
front of that.

I don’t think this is anything new, I think the guys in the US have been
doing this in V8 racing for a few years.

What then comes to mind is whether anyone is running an electric drive on
the oil pump? You would be able to prelube the engine before starting, have
constant pressure regardless of rpm (assuming that was desirable)

Rgds
Mark-----Original Message-----
In reply to a message from Richard Dowling sent Thu 28 Apr 2005:

Taper fittings are very common in industrial applications.
They do not slip at all, are quick and easy to assembly and
take apart. Look up Dodge Bearing, Browning, or Martin for
‘‘Taper Lock’’ or ‘‘QD’’ bushings for examples. You may even
find that the Jaguar crank taper is similarly sized to a
standard taper lock bushing.
Electric weater pumps would be a real neat addition to these
cars. Davies-Craig makes one as well as EMP-Stewart. The key
to these is how you control it. You may even be able to use
two small pumps and eliminate the thermostats entirely, or
including an electric thermostats would put you on the
cutting edge of cooling system design for a concept
unchanged in 100 years.

Visit the Jag Lovers homepage at http://www.jag-lovers.org for exciting services and resources including Photo Albums, Event Diary / Calendar, On Line Books and more !

6

Thanks for all the feedback.

Points arising:

a) The V12 crankshaft is about 43mm diameter, the GM V6 is 35mm.
So boring out the GM unit to fit 43mm leaves very little metal, and
definitely no metal for a keyway.
Loctite could replace the key, but still a very iffy proposition.

b) Chevy V8 crankshaft as used in Holdens is about 38mm, so the mating
damper may not offer much more metal than the V6 but could be within the
realms of possibility. I can try and get one to look at.

c) The V6 damper is a much more intricate design than the V12.
It looks as if it gives about twice the moment of inertia, and a very
different design of rubber insert.
It does not seem as if the performance as a damper would be inferior.

d) The V6 unit is 3.5kg ( 8lb ), belt diameter 170mm, 80mm long.
The complete V12 pulley assembly is 7kg ( 15.5lb ), belt diameter 140mm,
110mm long.

e) A normal woodruff key and 35mm diameter is good enough for the V6
driving the same accessory loading as the V12.
The V12 uses a taper lock bush probably because the pulley is much heavier
and a very overhung load on the end of the crankshaft.

f) The idea suggested of using the later mutigroove alternator
pulley/damper is interesting. If that can be used to drive all the
accessories then the front part of the pulley with 3 belt grooves can be
tossed in the bin, saving around 4kg.
However, although I have not had a damper fail on me, many others ( really
or myth ? ) say they have.
So just driving the alternator is a struggle for that British rubber, and
adding the other accessories with about 5 times more load makes you pause
and rethink the idea.
That raises a question. Do they fail mainly with temperature, or with age,
or with load ?
That alternator with 14V and 100A is only a couple of BHP, which does not
require much torque at all.

There remains a couple of other avenues to explore next week.

Richard Dowling, Melbourne, Australia, 1979 XJ-S & 1985 XJ6.

Visit the Jag Lovers homepage at http://www.jag-lovers.org for exciting services and resources including Photo Albums, Event Diary / Calendar, On Line Books and more !

7

Richard,

Look at the damper of the Aston Vanquish S; there’s hardly a damper to speak
of. There is just 1 very long serpentine belt driven of it, it has an open
3-spoked centre and can’t weigh more than 2 kg’s.

Cheers!

Jack Verschuur.

Visit the Jag Lovers homepage at http://www.jag-lovers.org for exciting services and resources including Photo Albums, Event Diary / Calendar, On Line Books and more !

8

At 07:54 PM 29/04/2005, you wrote:>Richard,

Look at the damper of the Aston Vanquish S; there’s hardly a damper to speak
of. There is just 1 very long serpentine belt driven of it, it has an open
3-spoked centre and can’t weigh more than 2 kg’s.

Cheers!

Jack Verschuur.

Now seriously Jack, you reckon there is much chance I could pick one up in a
wrecker’s yard ?
It will take a year’s salary to buy a new one as a spare part.
I was hoping for an el cheapo solution.

However, you raise a good point. Only 2 kg is on the small and light side.
Maybe there are very few broken crankshafts around even when the rubber
turns to sponge and it is obviously useless as a damper.
Are dampers generally an overkill ?

Richard Dowling, Melbourne, Australia, 1979 XJ-S & 1985 XJ6.

Visit the Jag Lovers homepage at http://www.jag-lovers.org for exciting services and resources including Photo Albums, Event Diary / Calendar, On Line Books and more !

9

At 10:21 PM 29/04/2005, you wrote:>Hi Richard,

I think that the reduced amount of “overhang loading” from driving all of
the accessories from the Multi-Vee grove on the newer Damper types would
actually promote longer life of the Damper rubber. There is also the fact
that the later-year parts have the benifit of much tighter quality control
due to Ford’s greater involvement in the manufacturing processes.

-Don Buresh, 1991 XJ-S V12 Coupe, Classic

In the case of the V12 the overhung 3 belt pulley is a metal to metal thing,
it does not float on rubber.
Only the alternator drive belt pulley is actually on the rubber. Looking at
it there is a lot of rubber and it is lightly loaded to drive a 2BHP
alternator. It is beyond me why they fail.
However, perhaps very few fail. My 1979 car still has the original and so
far no headaches.

Richard Dowling, Melbourne, Australia, 1979 XJ-S & 1985 XJ6.

Visit the Jag Lovers homepage at http://www.jag-lovers.org for exciting services and resources including Photo Albums, Event Diary / Calendar, On Line Books and more !

10

Good Idea Jack, I’m sure a couple of neighbours around here have one of
them in the garage for a weekend blast!

Shane Jarvis
Engineer
Abigroup Contractors
Albury Wodonga National Highway Upgrade
www.abigroup.com.au
02 9499 0805
0423 175 115

-----Original Message-----
From: owner-v12-engine@jag-lovers.org [mailto:owner-v12-engine@jag-
lovers.org] On Behalf Of The Wirewheel Shop
Sent: Friday, 29 April 2005 7:55 PM
To: Richard Dowling; v12-engine
Subject: RE: [v12-engine] Crankshaft damper

Richard,

Look at the damper of the Aston Vanquish S; there’s hardly a damper to
speak
of. There is just 1 very long serpentine belt driven of it, it has an
open
3-spoked centre and can’t weigh more than 2 kg’s.

Cheers!

Jack Verschuur.

Visit the Jag Lovers homepage at http://www.jag-lovers.org for exciting services and resources including Photo Albums, Event Diary / Calendar, On Line Books and more !

11

Richard, Shane,

You guys live in pretty grotty neighbourhoods if there is NOBODY in your
street with a new Vanquish S. Tough deal!

Really, the posting was just intended to demonstrate that at least one V12
can run without a humongous damper like on the Jag V12 without destroying
the crank. (and it’s just 2 bl**dy Ford V-6’es stuck together…)

Also, it can’t be too difficult to machine something like the Vanquish has
from billet steel or aluminium. Or cobble it together from a belt
wheel/pulley and an old Jag damper.

Next thing I’d like to know is, do we really need the damper, and does it
really need to be that heavy?

Cheers!

Jack. (off to the neighbour in order to find out if he has replaced his
Triumph Herald with a Vanquish S)

Good Idea Jack, I’m sure a couple of neighbours around here have one of
them in the garage for a weekend blast!

Shane Jarvis

Visit the Jag Lovers homepage at http://www.jag-lovers.org for exciting services and resources including Photo Albums, Event Diary / Calendar, On Line Books and more !

12

From Jack:

At 12:39 AM 30/04/2005, you wrote:>Richard, Shane,

You guys live in pretty grotty neighbourhoods if there is NOBODY in your
street with a new Vanquish S. Tough deal!

Exactly right.
The best was when a young couple moved into the small townhouse next door 6
years ago for a short time. They had a nice HE XJ-S.
At the time mine was back in the factory being rebuilt from top to bottom,
so we could not wow the neighbours with an exhibition of fine cars side by
side.
There is somebody about 50m down the road with a new S type, but that is the
best we can do nowadays.

Really, the posting was just intended to demonstrate that at least one V12
can run without a humongous damper like on the Jag V12 without destroying
the crank. (and it’s just 2 bl**dy Ford V-6’es stuck together…)

Also, it can’t be too difficult to machine something like the Vanquish has
from billet steel or aluminium. Or cobble it together from a belt
wheel/pulley and an old Jag damper.

Next thing I’d like to know is, do we really need the damper, and does it
really need to be that heavy?

Ah, but it not so heavy. Most of that 7kg of ironmongery hanging on the
front of the crankshaft is the 3 belt fixed pulley.
The actual damper is only the alternator pulley plus a layer of rubber about
8mm thick. That is 2.5kg at most.

If I can find a modern multigroove pulley/damper with a bore close to 43mm,
it can be tried.
More than likely most engines have a smaller crankshaft diameter, but if not
much smaller the pulley can be put in a lathe and bored out.

The only major problem would be lining up with the waterpump pulley, which
has no fore and aft adjustment.
The other accessories are hung on brackets which can be modified to make
things line up.

Since my rebuilt HE engine is destined for an electric pump, there is only
one problem: The new pulley/damper itself.

Jack. (off to the neighbour in order to find out if he has replaced his
Triumph Herald with a Vanquish S)

So now we have the truth of it.

Richard Dowling, Melbourne, Australia, 1979 XJ-S & 1985 XJ6.

Visit the Jag Lovers homepage at http://www.jag-lovers.org for exciting services and resources including Photo Albums, Event Diary / Calendar, On Line Books and more !

13

Geez, you’re lucky Richard, there’s a bloke down the road from me who
just bought a 1978 Torana, what’s even better about it, it’s registered!
All the other toranas around here seemed to have lost their wheels.

Shane Jarvis
Engineer
Abigroup Contractors
Albury Wodonga National Highway Upgrade
www.abigroup.com.au
02 9499 0805
0423 175 115

-----Original Message-----
From: owner-v12-engine@jag-lovers.org [mailto:owner-v12-engine@jag-
lovers.org] On Behalf Of Richard Dowling
Sent: Saturday, 30 April 2005 9:32 AM
To: v12-engine@jag-lovers.org
Subject: RE: [v12-engine] Crankshaft damper

From Jack:

At 12:39 AM 30/04/2005, you wrote:

Richard, Shane,

You guys live in pretty grotty neighbourhoods if there is NOBODY in
your> >street with a new Vanquish S. Tough deal!

–

Exactly right.
The best was when a young couple moved into the small townhouse next
door
6
years ago for a short time. They had a nice HE XJ-S.
At the time mine was back in the factory being rebuilt from top to
bottom,
so we could not wow the neighbours with an exhibition of fine cars
side by
side.
There is somebody about 50m down the road with a new S type, but that
is
the
best we can do nowadays.

Visit the Jag Lovers homepage at http://www.jag-lovers.org for exciting services and resources including Photo Albums, Event Diary / Calendar, On Line Books and more !

14

Richard,

You’re going with electric waterpumps; why not take it a step further? I’m
assuming elec fans as well.

Mount the alternator back to front on the crank, and install electric power
steering? Voila, no more belts to worry about. Oops, forgot the A/C
compressor. I’m sure there must be electric versions of those around by now
as well.

Now run that whole set-up on LPG mixed at the throttle and get rid of all
the EFI stuff, and you’d have a pretty neat looking V12!

Cheers!

Jack.

Visit the Jag Lovers homepage at http://www.jag-lovers.org for exciting services and resources including Photo Albums, Event Diary / Calendar, On Line Books and more !

15

So far:

a) Tried an Australian manufacturer of fancy racing/street dampers with
serpentine belt pulley.
They mentioned about US$1,000 for a V12 custom edition and I lost interest.

b) I tried a manufacturer of industrial pulleys to see if they can make a
pulley which I can fit to the existing crankshaft damper.
About US$250 made from malleable cast iron, and it would be very heavy.
Can make in aluminium for extra money but not sure how it would wear.
Not very encouraging.

c) Went back to the Holden V6 damper I have.

This is possibly a US made item, since Holden imported V6s from the U.S.A.
before making their own.
It is an interesting design, and well made.
The pulley itself looks like it is made of cast steel, it is mighty hard and
a fairly thin section.
The pulley has 4 spokes which connect to a central hub, and the hub is bored
to take a bearing, possibly a double row ball bearing.
Through the centre of the bearing is a shaft connecting to the inner hub
which is keyed onto the end of the crankshaft.
Hence the pulley would normally be free to rotate around the crankshaft
mounted inner hub.

So that torque can be transmitted, a thick rubber web connects the inner hub
to the outside of the pulley.
This web also acts as the damping medium.
The design is quite intricate, such that if the rubber web fails the pulley
is constrained by cast arms on the inner hub so torque is still transmitted,
albeit with much noise.
In this design the rubber has an easy life since it can only move in one
dimension, not the 3 dimensions of the V12 damper.
It does have to transmit torque to all accessories, not just the alternator,
so it must transmit 5 times the torque at least.

Taking this apart to use only the pulley occupied over an hour.
I put the pulley in the small factory lathe to skim it where an adaptor
needs to be fitted, but the pulley material is too hard to easily machine on
such a large diameter so I will take it to a machinist.
It looks as if a reasonably simple adapator plate can be made by laser
cutting two pieces of 5mm mild steel, and this I can machine on the small
lathe and true it all up to fit on the end of the V12 damper.

Well, that is the theory. Next thing is to check if suitable multigroove
pulleys can be found in the wrecker’s yards to fit the accessories.
I don’t have time to do this, but I know somebody who likes trawling through
the yards looking for bits.

Richard Dowling, Melbourne, Australia, 1979 XJ-S & 1985 XJ6.

Visit the Jag Lovers homepage at http://www.jag-lovers.org for exciting services and resources including Photo Albums, Event Diary / Calendar, On Line Books and more !

16

I felt brave enough to put the V6 pulley back in the small lathe and give it
a try.
This time in the much heavier 4 jaw chuck which grips better, and with a
bigger tool.
The tool was a piece of high speed tool steel made in India ( yes, you heard
it right ) and so cheap at a Sunday market I bought 3 pieces and a couple of
parting tools for almost peanuts. I have a very nice German parting tool
holder with a tool bit that is height adjustable, very elaborate and the
guys in the factory have a habit of digging it into soft material and
busting the tool bit which is a very hefty German price to replace. The
Indian ones are simple and so cheap who cares.
The same market vendor had Russian micrometers at cheap prices, so one of
those was added to fill a gap in the factory tool lineup.
Being Russian it had to be metric, which is not quite so easy to read as an
inch variety. If I measure a couple of thou clearance on a diameter I know
what it means. If a metric micrometer tells me 0.15mm, it is hard to grasp
before multiplying by 40 to get 6 thou which conveys meaning.

A quick grind of the tool steel to make a cutting edge and then try cleaning
up the pulley casting for fitting on the V12.
The tool was screeching which means cutting is marginal, but luckily the
casting was accurate so did not need much machining to true it up. The
other bits needed to complete the job are being laser cut from 5mm steel and
include a couple of spacers to get the pulley clear of the original damper
which has to stay in place.

There is a new Sanden A/C compressor for the front of the engine, but it
came with a double vee pulley and I need a mulitgroove style pulley for the
serpentine belt.
Initial checking around reveals a complete new compressor with clutch/pulley
is worth A$300, and a clutch/pulley unit as a spare part is A$200. Not good
value for money. Perhaps a swap can be arranged for minimum dollars if I
can find a repair shop with spare multigroove pulleys.

Today the rest of the machined parts for the chain tensioner kits turned up
a week late. Next week the laser cut parts for the welding jig are
promised, so that will keep me quiet a few weeks - or maybe busy rather than
quiet.

Richard Dowling, Melbourne, Australia, 1979 XJ-S & 1985 XJ6.

Visit the Jag Lovers homepage at http://www.jag-lovers.org for exciting services and resources including Photo Albums, Event Diary / Calendar, On Line Books and more !