TR6 crankshaft pulley & damper

[Ianseventy6man]

Hi, can anyone tell me how the damper works? Looking at my steel pulley there is what appears to be a rubber ring which looks a bit perished, but I can't quite see what this whole item does apart from transmitting crankshaft motion via the fan belt. How does it damp? What does it damp? Are there any alloy alternatives available if so from where? Any advice or help would be much appreciated.

[Richard71]

Hello Ianseventy6man,

 

I'll try to explain, I say try as I'm not the greatest at explanations, but I will try. The true name for the component you ask about is a "harmonic damper" (the pulley part is incorporated in convenience by the manufacturer to drive fans, superchargers, aircon etc or whatever drive belts may be required). Anyway, during the four stroke or even a 2 stroke cycle engine the linear motion of the piston/conrod to the crankshaft (crankpin) ultimately results in rotational movement. But hey, you cant have 1 or up to 32 pistons and conrods battering down on a crankshaft without the key word "deflection" (think Rolf Harris and is wobble board), the crankshaft bends during these stokes, it deflects from form and that small rubber seal bonding the two counteracting components of theTR6 damber absorbs that. Every engine from 2 - 20,000hp I have worked on has some kind of two piece damper, be it they're rubber/silicone filled or oil, they do they same thing ,and that is dampen harmonics from crankshaft deflefction. Thus protecting big & main bearings not to mention the dreaded thrust washer TR syndrome.

 

There is an alloy alternative available from Racetorations, I know because I bought one, I expect it to be a good piece of kit when fitted, though a little disappointed they negated to at least degree the thing!

 

Richard.

[jambo]

I'm on the lookout for a decent used one if anyone has one they don't need. Cheers.

 

Jim

[Denis]

Great explaination Richard!

 

I had cause to get mine welded when the keyway elongated that caused a bad knocking noise!

 

And only last month I had to fit a new Damper Crank Pulley to my Diesel Peugoet as it had started to sound like a Machine Gun!

[AlanT]

Imagine a ruler held over a table-top. Ping the end and get a musical note.

 

Now get a rubber ball and stick it on the end, ping it and get a dull thud.

 

Damping relies on a component that produces forces related to speed, not position like with

a spring.

 

Rubber does this a bit, fluids are even better, hence hydraulic dampers of various kinds.

 

First job I had as a graduate was on a Mag-Lev train. Problem was to get some suspension damping.

Now you must do the "damping" with high-voltage electrical power.

Edited February 7, 2014 by AlanT

[JRCWeedon]

I'm on the lookout for a decent used one if anyone has one they don't need. Cheers.

 

Jim

Hi Jim

I am pretty sure I have got a competition one in my box of spares which I have never used. It may be a racetorations one but I am not sure. Send me a pm if you are interested and I will look it out.

Regards

John

[JRCWeedon]

Hi Jim

I am pretty sure I have got a competition one in my box of spares which I have never used. It may be a racetorations one but I am not sure. Send me a pm if you are interested and I will look it out.

Regards

John

 

Hi Jim

I should have looked at your location first!

I presume you do not wish to pay postage from UK it is quite heavy.

Regards

John

[Tom Fremont]

GOODPARTS have one which supposedly allows another 1000 rpm on the 6-pot engine. Costs a great deal but if it works may justify the price.

 

There are a couple of places in the U.S. which re-rubber and repaint the marks on the original pulleys. One is known as Damper Dudes. Whether they've done the diligence on rubber durometers to arrive at the correct one for this application isn't something I'd wager money on, however. I chose to buy NOS when I could get my hands on them but the effects of age are another question .

 

MOSS U.S. sold some repros at one time ( may still ) but they didn't have holes ( spokes ), weren't balanced nor marked either. I've got (2) which I had balanced and marked, never used if anyone is interested ( PM me ).

[Richard71]

Funny you mention that Denis, I had a collapsed damper on a diesel Peugeot 406 a few years back, they're probably still using the same part.

 

Richard.

[Peter Cobbold]

Its called a 'torsional vibration damper' and damps out the twisting of the crankshaft caused by the torque from the pressure on the pistons:

"Crankshaft torsional vibration has been a problem
with aircraft engines since before World War I.
Crankshaft torsional vibration happens because each
power stroke tends to slightly twist the shaft. When
the power stroke subsides, the crankshaft untwists.
One would think that something as massive as a
crankshaft would not twist significantly, but any piece
of metal always deflects a bit when a force is applied,
and when large amounts of power are generated, the
forces can become huge indeed. The effects of
torsional vibration can be amplified by a phenomenon
called torsional resonance. Each crankshaft design
has a natural torsional frequency like the note of a
ringing bell or sound of a vibrating guitar string. If this
natural frequency coincides with the torsional
frequency of the crankshaft, the effects can be
devastating, resulting in broken crankshafts, lost
propeller blades, sheared....."

 

Dampers have to be tuned to the crankshaft in the development lab using a torsiograph set up on an operating engine, at loads and rpm that are typically expected.

This is expensive and tricky: see "aftermarket r&d" section 7 here:

www.bhjdynamics.com/downloads/pdf/tech/BHJDynamics_Damper_Info.pdf

 

So we know what data would be needed to design a repro damper. If the torsiograph data used by Triumph stlll exists in the archives for their various engines it would be very useful for manufacturing repro dampers.

 

I have found my own solution:

section4: "Blower Drives – Mechanical blower drives for Roots type blowers can actually help the
damper by acting as more damping at the front of the crank. Mechanically driven blown
engines generally are no worse, torsionally, than normally aspirated. Turbos usually are
worse."

 

Peter

Edited February 7, 2014 by Peter Cobbold

[jambo]

 

Hi Jim

I should have looked at your location first!

I presume you do not wish to pay postage from UK it is quite heavy.

Regards

John

PM sent John - i have a UK shipping address but live down under. Cheers,Jim

[Steves_TR6]

This was an interesting thread!

 

In the spring im considering building a mapped ignition system for my 6, and to do so will need to add a toothed ring to a crank pulley.

 

Ideally i'd like to source a spare damper pulley to modify.

 

Has anyone got a spare serviceable 6cyl damper pulley?

 

Regards

 

Steve

[Richard71]

This was an interesting thread!

 

In the spring im considering building a mapped ignition system for my 6, and to do so will need to add a toothed ring to a crank pulley.

 

Ideally i'd like to source a spare damper pulley to modify.

 

Has anyone got a spare serviceable 6cyl damper pulley?

 

Regards

 

Steve

 

Hi Steve,

 

I've been reading the recent threads on EFI kits and the need for trigger wheels attached to the pulley/damper for measuring engine speed.

 

Have I missed something???

 

A hole drilled in a convenient location on the bellhousing where a magnetic pick-up can be fixed can measure the engine speed off the ring gear.

The Gurus who develop these ECU gizmos can surely programme in the amount of teeth on the ring gear and speed can be easily & accurately measured thus, and without the trigger wheel and extra rotating weight.

 

Like I said, maybe I've missed something, it's perhaps been covered before and there's good reason for not using that method???

 

Richard.

[Sapphire72]

Here are (2) USA sources for quality rebuilding of harmonic balancers/dampers:

I have no idea what round-trip shipping would cost.

 

Damper Dudes have a good reputation with TR6 owners.

 

http://damperdudes.net//index.php?cPath=41

 

Dale Manufacturing in the Pacific NorthWest is seasonal, read their webpage carefully.

 

http://hbrepair.com/

[TriumphV8]

 

A hole drilled in a convenient location on the bellhousing where a magnetic pick-up can be fixed can measure the engine speed off the ring gear.

 

Richard.

 

That is possible but its easier to use a trigger wheel.

It is required that the teeth have usuable shape.

If it works at idle it may cause trouble at high revs.

The number of teeth must be able to be divided by cylinder/2

An additional information of TDC is necessary, too.

 

Edited November 30, 2016 by TriumphV8

[Steves_TR6]

Thanks for the replies everyone.

 

Andreas's picture shows exactlynwhat i am aiming at, a 36-1 toothed wheel on the bacl of the standard pulley.

 

Andreas, how did you address the tdc sensing thats needed for sequential injection/ignition, or are you using wasted spark/squirt?

 

Regards

 

Steve

PS, im leaning towards the Nodiz system but they have yet to release their 6cyl version, has anyone used Nodiz especially with Coil on Plug ?

[Bill Bourne]

Vibration Free do a "rattler" Expensive though.

 

http://vibrationfree.co.uk/sterling-rattler/sterling-rattler-shop/#!/Triumph/p/61592039/category=16322085

 

Best Bill

[DaveN]

I bought a new one in the States, delivered FOC to the hotel in Florida where my daughter was staying. and two year old grandson had to carry it back in his rucksack.The TSA never batted an eyelid.. Result!

I fitted it and checked the markings and it was spot on. However if I was going to rebuild the engine I'd opt for a Rattler for the peanuts it costs in the greater scheme of things.

 

I recently had to replace the Dynamic pulley on my 530d ...I have never experienced such heavy steering it was a real two handed job to get any change of direction even at speed. (Its a known failure item on bmw. )

[TriumphV8]

Andreas's picture shows exactlynwhat i am aiming at, a 36-1 toothed wheel on the bacl of the standard pulley.

 

Andreas, how did you address the tdc sensing thats needed for sequential injection/ignition, or are you using wasted spark/squirt?

 

 

TDC sensing is done by the missing tooth.

 

As I use a Megasquirt I can key in a delay in degrees

to give a precise position of TDC.

No need to make the wheel itself adjustable.

 

If you use EDIS the position of the missing tooth must be precise

to establish the limp home mode, what is a constant 10 degree advance

if EDIS receives a trigger signal outside expected range.

 

In that case you have to make long holes into the trigger wheel to rotate it

into position or make the VR sensor position adjustable.

If I am right the VR sensor must point on the fifth tooth after the missing one

at TDC.... Can be found in the Megasquirt manual under ignition with EDIS

[Steves_TR6]

Thanks Andreas

 

Are you running wasted spark?

 

If not, how does the megasquirt know which cylinder to fire this rev, ie is no1 on compression or exhaust?

 

Wasted spark is fine, and i may go with it, but i do like the idea of a full sequential 6 cylinder ignition system, not a 3 cylinder system where each output fires 2 cylinders!

 

To do this tdc sensing isnt enough, it'll need cam sensing or similar?

 

Steve

[TriumphV8]

Hi Steve, you are right, if you do not go wasted spark you will

need an additional cam signal.

I do not see any advantage of that, the individual coils are established

because the dwell time of the coil is at the limit in a TR6.

With wasted spark and the modern coil dwell control you are

fully in the range that you do not have to worry about that.

 

Many things are nice to have but I can say for my TR6 there was no advantage to

do all those swaps from my MegaSquirt 1 in the early days to that modern and faster

things. A lot in the forum is just for the modern cars and needs to be done to integrate

the MS into the existing loom. I would go the easy way because it solves all the

problems we had with the PI in the early days and is not too complicated.

My recommendation is to spend that time into testing and setting the MS details.

 

I take the ignition signal from the MegaSquirt and go into the MSD6 and than to the

Blaster2 coil and than into the normal distributor to get it to the proper sparkplug.

[Alan Jones]

Really interesting thread, but has it gone a bit off piste?

I have a Revotec fan fitted so the original fan and extension has been removed. Does this affect the harmonics of the crankshaft and should I be worried? I don't take it much above 5k rpm and then only occasionally.

Regards,

Alan

[DaveN]

In short......no!

[mike3739]

Without doubt a big No No!

 

Cheers

 

Mike

[Guest ntc]

It depends on the type of washer used.