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Harmonic Damper


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What is your opinion?

1. Keep it and use it as is,

2. Scrap it and buy a new one?

3. Refurbish it, where?

I know Ed had some thoughts about minor damage to the external rubber, which does not really say anything about the internal rubber. I am a little hesitant sending the damper to "Damper Dudes" in the US. Eventhought they have a good reputation. But maybe there are some UK based companies who can refurbish. I am not looking into buying a new one, especially with the quality standards of some of the known suppliers. Unless someone has a true respectable source.

Jochem

RS1.jpg

RS2.jpg

RS3.jpg

RS4.jpg

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Jochems,

You may have seen my article on damper pulleys in TRaction (Issue 320, p.41) You can read it in the online archive of previous issues:   https://www.tr-register.co.uk/tr-action-index     There I showed this graph:

image.png.ca5487ee92245360bef9b6169f11d4a9.png

Please  read the artical for more detail on damper testing.

As can be seen, damper 1 has a  significantly poor response compared to the Control damper, while 7 closely follows it.     However, the rubber on 1 looked fine, while that on 7 was swollen and looked deteriorated.     That reflects my experience of testing pully dampers, that the visual appearance is no guide to function!    These dampers are at least fifty years old, time spent in the aggressive environment of the engine bay, being attacked by heat and oil, so that any of them still work is remarkable!

I think I'm the only person, outside manufacturers and commercial damper rebuilders, who can test a Triumph pulley damper.      I will be glad to test yours, and reassure you or advise replacement, if you will PM me.

John

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6 hours ago, john.r.davies said:

Jochems,

You may have seen my article on damper pulleys in TRaction (Issue 320, p.41) You can read it in the online archive of previous issues:   https://www.tr-register.co.uk/tr-action-index     There I showed this graph:

image.png.ca5487ee92245360bef9b6169f11d4a9.png

Please  read the artical for more detail on damper testing.

As can be seen, damper 1 has a  significantly poor response compared to the Control damper, while 7 closely follows it.     However, the rubber on 1 looked fine, while that on 7 was swollen and looked deteriorated.     That reflects my experience of testing pully dampers, that the visual appearance is no guide to function!    These dampers are at least fifty years old, time spent in the aggressive environment of the engine bay, being attacked by heat and oil, so that any of them still work is remarkable!

I think I'm the only person, outside manufacturers and commercial damper rebuilders, who can test a Triumph pulley damper.      I will be glad to test yours, and reassure you or advise replacement, if you will PM me.

John

:blink::o Very interesting, thanks John !

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  • 2 weeks later...

Thank you Jochem for the clear titel of this thread,

and thank you John for the information and help to Jochem.

Please could you John exlain me in 3-5 short and simple sentences what the the harmonic damper does.

Thanks in advance, Marco

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Jochems

Would you be kind enough to measure the diameter of the pulley on the rear side, I want to make a timing tape, to stick on the outside but I need an accurate diameter please. I dont have any timing markings except for the TDC mark.

John 

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Z320,

Since Torsional Vibration was the subject of my dissertation for the engineering degree I took after I retired, it's not easily condensed into a post here.  So may I refer you to the article I wrote for TRaction, published in Issue 320, March/April 2020, pages 41-4?     The TRR has all back issues online at https://www.tr-register.co.uk/tr-action-index, so please start there.    I'm glad to explain anything that I didn't make clear in the article!

John L,

The 2.5L damper has a diameter of 165mm.  So 1.44mm/degree at the rim.   But, wouldn't it be easier to set the crank to TDC, and mark the damper inertia ring at the pointer?   Then, with the damper on the bench, mark out as many After and Before degrees as you wish?     I like to paint them with 'Snopaque', the paper-white typing correction fluid, scrape off the excess and paint over with a clear coat of varnish.

352502061_Highlightingtimingmarks.jpg.68d57a700d76b490e0dc2f3d383c4edc.jpg

 

Edited by john.r.davies
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Hi John,

thank you very much, but I'm not member of the TR-Register UK,

like some other visistors of the forum too. This is why I can't read your article.

What I understand from Wikipedia in one sentence:

long crankshafts of 6 and 8 cylinders engines suffer from internal vibrations and torsion and a therefor special designed damper helps to reduce them.

I guess (please correct me):

- this is less the case on (short) 4 cylinders crankshafts (I own a TR4A)

- and less the case with a crankshaft bearing between each con-rod (TRs have two conrods between each bearing)

I know there was a harmonic damper to buy for the 4 cylinders coming with the small belt set - made of aluminium.

This may be a "product of hope", because the damper benefit is related on weight, diameter and elasticity of the rubbber.

I know 2 four cylinder drivers with broken crankshaft, if I remember right it broke where the rear crankcshaft bearing is situated.

This is why I bought an old TR4A engine to have one as a spare part.

Your rating about my thought is well appreciated.

Ciao, 

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Marco - the breakage of four-cylinder cranks at the rear bearing is probably nothing to do with torsional vibration or the presence or absence of the fan extension. This old thread explains:

 

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Z320, and Rob,

Just before the pandemic hit the fan, I was being helped by a member with a TR4, who agreed to let me add sensors to his car, and measure the vibration.   The plan was to do so with and without the extension, and nail this controversy for good.    But I regret that I have not been able to contact him again, and I fear that Covid may have got him.

I have asked before if anyone else with a TR4 (or 3) would let me use in their car for this project, in the interests of scientiific knowledge!     I was able to design brackets to bolt onto my collaborators car, never to test fit them, but the design objective was complete removal after the test runs with no residue.     Are any owners who would be willing to cooperate?   Would you please PM me?     As none in the NorthWest will volunteer, I'll travel anywhere in the UK!

Z320,

If you will send me an email address by PM, I can send you a copy of my TRaction article.    Briefly, and in response to your post above, this is Torsional vibration, on the axis of the  rotating crank, so the addition of more main bearings is no protection.    

John

Edited by john.r.davies
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1 hour ago, Z320 said:

I know there was a harmonic damper to buy for the 4 cylinders coming with the small belt set - made of aluminium.

This may be a "product of hope", because the damper benefit is related on weight, diameter and elasticity of the rubbber.

 

The one supplied as an option with the thin belt kit is actually an MGB part and not specifically for the TR engine.

Stuart.

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1 hour ago, stuart said:

The one supplied as an option with the thin belt kit is actually an MGB part and not specifically for the TR engine.

Stuart.

I've seen that at Moss, to use without fan extensions, but currently not available.

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This is really good and useful work, John, and really interesting to me.

I often wonder if the makers of new or rebuilt dampers actually have the expertise or equipment to do these measurements.  It seems that if they did, they would say so in their marketing materials.  Most of fhem don't mention it.

Ed

Edited by ed_h
clarification
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Thank you, Rob!    

Readers of that paper may like to note the comment in the section on measurement "Aftermarket R&D"  that, "This can be done in a day or two on the dyno, but is not exactly cheap. Torsiograph equipment goes for around $30,000 if you buy it, $500 - $1,000 a day if you rent it with an operator and dyno time is $1,000 a day or so. Don’t forget the price of the motor and experimental dampers and the fuel."   At present, I'm glad to do these tests without charge, only asking for the owner to pay post & packaging, which is significant for a heavy damper!   But it does take about half a day for each test, and certain quantity of fuel!

Copies of my TRaction article sent o Mario , and Jochem.

May I repeat my appeal for a willing TR4 or 3 volunteer?    Glad to discuss the project either by PM, email or phone - PM me for my contact details.  This technique could contribute real data to the controversy about Triumph four cylinder crank failure!

John

Edited by john.r.davies
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This thread together with the TR Action article and the other referenced info are really fascinating and of great educational use.  I bet very few of us knew even the basics of what dampers really do for engines  A perfect gem to show off the value of the Tech Forum to the world at large.  The work done by John is magnificent.

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