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Harmonic damper and thin belt conversion kit


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Thanks trolley bus. I've contacted a classic Holden parts outfit in Hamilton to see what they say. I assume that the spacer is for the timing cover seal so it would have to be a grind and polished finish, not turned. I'm not sure I want to mutilate my original pulley as I like to keep all the old bits in case I or a subsequent owner (when I drop off my perch) can put it back to original condition if so desired.

 

The Australian technical tips book sounds useful. Is it possible to get one?

 

Cheers, Tony.

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  • 2 weeks later...

I talked "to the horses mouth" on this subject 20+ years ago and the only reason they use MGB pulleys are they are a direct fit to the TR crank and then you just slide a sleeve over the seal face to bring

that dim up to the correct size for the TR front cover seal.

I had a spare pulley (off the three bearing version), made a water pump pulley and fitted an alternator from the start.....I'm really going to shoot myself in the foot here but 57,ooo + miles and fine.

I agree, I cant see it has any dampening effects as not designed for this engine, but it fits and its cheap, ding dong

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Well, I looked at the TR register australia inc website as suggested by Graham Harris and according to the in depth article on the conversion using a red engine Holden balancer, the balancer bore is around .006 thou undersized for the 1.125 inch crankshaft nose on the TR. it is suggested that you take it to a machine shop to have it "polished" to fit, though I would image reaming or boring out would be more appropriate. Dayco, Australia, list a couple of uprated variations of this balancer - a fast street performance one rated up to 6500 rpm, part no PB17AST, and another for flat out racing engines. BNT auto parts in NZ have a PB17AST they are getting down for me to look at tomorrow. It is a reasonably priced (IMO) NZ$150 (ish). Luckily I am able to bore it out myself and have contacted Dayco tech dept asking for advice on whether rebalancing afterwards is advisable or even whether it is advisable to attempt the modification at all on a finely balanced component. There is a local aircraft engine rebuilder who does precision balancing, they would probably be a better bet than your average auto engine rebuilder.

 

It seems to me that harmonic balancers are designed for an engine in as much as they are designed to fit. I don't believe they are built to be tuned to any particular harmonic frequencies generated by any particular engine but please prove me wrong if you know better.. Also the variation in price between units for a given application are due to quality of materials eg SG cast iron or other, the type of bonding material and the bonding method used, and the care taken to balance the unit. In any event, the Dayco offering appears to me to be much superior the the offering from Moss, etc.

 

Tony

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Well, I looked at the TR register australia inc website as suggested by Graham Harris and according to the in depth article on the conversion using a red engine Holden balancer, the balancer bore is around .006 thou undersized for the 1.125 inch crankshaft nose on the TR. it is suggested that you take it to a machine shop to have it "polished" to fit, though I would image reaming or boring out would be more appropriate. Dayco, Australia, list a couple of uprated variations of this balancer - a fast street performance one rated up to 6500 rpm, part no PB17AST, and another for flat out racing engines. BNT auto parts in NZ have a PB17AST they are getting down for me to look at tomorrow. It is a reasonably priced (IMO) NZ$150 (ish). Luckily I am able to bore it out myself and have contacted Dayco tech dept asking for advice on whether rebalancing afterwards is advisable or even whether it is advisable to attempt the modification at all on a finely balanced component. There is a local aircraft engine rebuilder who does precision balancing, they would probably be a better bet than your average auto engine rebuilder.

 

It seems to me that harmonic balancers are designed for an engine in as much as they are designed to fit. I don't believe they are built to be tuned to any particular harmonic frequencies generated by any particular engine but please prove me wrong if you know better.. Also the variation in price between units for a given application are due to quality of materials eg SG cast iron or other, the type of bonding material and the bonding method used, and the care taken to balance the unit. In any event, the Dayco offering appears to me to be much superior the the offering from Moss, etc.

 

Tony

Tony,

A harmonic balancer is most definitely tuned. It is tuned to a engine running at full throttle across its rpm range. The balancer counteracts the 'twist' imparted on the crank by each firing stroke. The tuning involves measuring the crank nose 'twist' as the engine runs on a dyno. It is an expensive business requiring a 'torsiometer'.

Because the twist is imparted by firing forces it will depend upon the gas forces acting on the piston, stroke, crank throw, crank length, crank bearing locationss, the 'stiffness' of the crank itself, and flywheel. mass/diameter. And rpm.

http://www.bhjdynamics.com/index.php?main_page=page&id=4

 

The rpm at which the twist is worse depends upon number of cylinders.

Fig 3 shows small peaks at 2200rpm and 3000rpm on a 6-pot.

http://nippon.zaidan.info/seikabutsu/2000/00430/contents/177.htm

To allay TR6-ers' worrying about cruising at 2200rpm, these data only apply to an engine at full load ( wide open throttle). Few road TRs spend much time at a fixed rpm at wide open throttle. The resonances will still be there at those rpm at cruise, but the forces and crank twist will be much less.

Racing is another matter.

 

Peter

 

4-cylinder:

http://www.epi-eng.com/piston_engine_technology/crankshaft_torsional_absorbers.htm

""Many of the automotive 4-cylinder engines don’t require such an absorber, primarily because of their inherently higher stiffness-to-mass ratios. However, several automotive manufacturers have initially omitted a torsional absorber from early engine runs, only to find that crankshaft life was unacceptably short. The Nissan folks discovered this with the early 240-Z engines, which didn’t have an absorber, and therefore lasted only about 100 hours in automotive (i.e. VERY LIGHT DUTY) service.""

 

http://www.ijer.in/ijer/publication/v2s6/IJER_2013_602.pdf

- note stresses around #4 journal and web

Edited by Peter Cobbold
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...4-cylinder:

http://www.epi-eng.com/piston_engine_technology/crankshaft_torsional_absorbers.htm

""Many of the automotive 4-cylinder engines don’t require such an absorber, primarily because of their inherently higher stiffness-to-mass ratios. However, several automotive manufacturers have initially omitted a torsional absorber from early engine runs, only to find that crankshaft life was unacceptably short. The Nissan folks discovered this with the early 240-Z engines, which didn’t have an absorber, and therefore lasted only about 100 hours in automotive (i.e. VERY LIGHT DUTY) service.""...

 

Maybe that's because the original Datsun 240Z was an inline 6-cylinder engine.

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Maybe that's because the original Datsun 240Z was an inline 6-cylinder engine.

Don, :D Thanks for that clarifaction. I didnt know, nor did those aeroengineers on that website. That's good news for the 4-cylinder owners. And may explain why Triumph did not fit a damper, the 4-pot shaft is too short for serious torsion to develop. Peter

Edited by Peter Cobbold
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Hi Tony,

a simple bent sheet of mild steel or Ali will do fine.

 

Roger

 

Revington alternator heat shield with an additional piece of heat resistant sheet from Merlin Motorsport attached to it, does the job for me. Easy to fix too.

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Look, I don't mind making a idiot of myself by airing my ill informed opinions in public providing it results in someone else bringing forth useful information which exactly what Peter Cobbald has done, so many thanks for that Peter. I do wish you had chimed in earlier in the thread though! I don't understand a lot of it, but the bit on BHJ dynamics website was very illuminating. I could understand it. I wonder if this thread has had so many views because people are keen to see what ridiculous statements I am going to make next.

 

Anyhow, I went to BNT today to measure the street performance damper for the Holden and it is indeed 6 thou undersize. The tech dept at Dayco say if I dial it in properly with a DTI to maintain concentricity it shouldn't need rebalancing, and that to their knowledge 17 of these units have been sold in Aus for this very purpose. However, in the light of Peters post I am now leaning towards the "don't bother with them" brigade, now especially because, as others have also pointed out, they haven't been tuned for the TR engine. The Holden one isn't even tuned for any 4cyl, but for a 6 cyl, which it seems are the ones that need them most. I am wondering if the prime purpose of the Aussies fitting them is in fact to get a pulley for a thin belt as much as it is for the supposed harmonic damping effect.

 

So I'm teetering towards just sticking the old boss back on without the fan and extension but in case anyone thinks I have been over come by a bout of clear thinking and sanity I am now toying with the idea of making pulleys for a poly vee belt. I just need a hunk of aluminium big enough to make the crankshaft pulley.

 

Tony

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Tony, I didn't chime in earlier because there was a long thread a while back, and I realised I did not fully understand HDs then. Still dont, at least not to the point of being confident a given aftermarket absorber will actually do the job.

http://www.tr-register.co.uk/forums/index.php?/topic/46104-about-crankshaft-dampers/

4-pot MGB: post #34

Peter

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I did not know about the thread you refer to Peter, sorry for resurrecting it again. In my defence I did enter harmonic dampers in to the search facility but nothing came up. I flicked through previous topics but obviously not back far enough, there are so many. I am much better at losing things than I am finding them as Mrs B will testify. I've looked at the thread, it is very informative.

 

I wonder if anyone knows anything about the harmonic damper kits sold by British Frame and Engine located in California. I have emailed them several times but cannot elicit a response.

 

Tony

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I'm glad you think so Roger, I don't want to be the register bore.

I've had another change of tack in light of the thread Peter directed me to and have just sent a email to ATI enquiring about their dampers designed for this engine. It's been a long journey so far but I feel I am finally beginning to get somewhere. I am glad I didn't just stump up for the Moss kit. Thanks everyone for your contribution, the Register and its members really are a fantastic resource and mine of information.

 

Cheers Tony.

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Some of you following this thread may be interested to know that I've heard from ATI performance and they tell me as I am in New Zealand it is easier and cheaper to get their parts from Summit racing (don't know where they are yet) as ATI dont accept foreign credit cards (so much for the global economy). The part no is 918569 and includes the hub. I asked a couple of techie questions but didn't get an answer, perhaps Summit racing will be more forthcoming.

 

Tony

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...Summit racing (don't know where they are yet)...

 

Summit Racing Equipment is US-based,. Headquartered in Northeastern Ohio (near Akron, in Summit County). They have three retail stores and a huge mail-order business.

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Just to put some fuel to the fire... When I had my car's engine restored, the guy at the shop notice a very imbalanced flywheel. In his words: "...when we put them (= flywheel and crank) on the tester, the flywheel was so imbalanced, it wanted to jump of the tester and walk out of the shop." They attached all components to the crank and tried again and hoped for improvement. In the end, the flywheel proved to be the culprit and it needed rebalancing.

 

In short: are you shure that the whole contraption is (more or less) balanced when you start working on the front of the crank? No rubber donut can compensate for a wobbly flywheel @ (let's say) 3000 rpm!

 

Menno

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I did not know about the thread you refer to Peter, sorry for resurrecting it again. In my defence I did enter harmonic dampers in to the search facility but nothing came up. I flicked through previous topics but obviously not back far enough, there are so many. I am much better at losing things than I am finding them as Mrs B will testify. I've looked at the thread, it is very informative.

 

I wonder if anyone knows anything about the harmonic damper kits sold by British Frame and Engine located in California. I have emailed them several times but cannot elicit a response.

 

Tony

Tony,

No need for the apology. Some threads are repeated many times. It all helps to build up a picture of the main failure modes on our TRs.

Peter

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we'll make an Englishman of you yet.

Thanks, I'm trying! And I don't mind when a forum member tells me that something is not correct. I'm not 'hurt' when I'm corrected. So just tell me when it should be different/better.

 

I've just read this on TZ-UK, a watch related forum with a heated discussing about the use of 'a' and 'an': Grammar: the difference between knowing your **** and knowing you`re ****!

 

Back on topic: What I wanted to say is that I am not sure about the harmonic damper. I've told it before: Revington has a note about it on the website:

 

 

 

A word about Harmonic dampers versus solid machined crank pullets

We don t usually use Harmonic dampers on the crank. If one is fitted to an engine we are working on and it is not giving problems we will leave it there.

I have raced my TR2 for over 30 years with a standard type crank without a rubber mounted pulley. I recon I have done 200,000 miles in the car a lot of which would be racing, hill climbs, sprints, rallies as well as fast road work and I haven t had a problem yet. The issue as I see it is that engine manufacturers go to a lot of trouble to design a harmonic balancer when an engine is designed to get rid of unwanted harmonics. Here is the clue; harmonics are frequency dependent so the damper has to eliminate specific frequencies. Obviously not all engines produce the same harmonics and therefor one damper does not fit all. In fact you could put a damper on and introduce unwanted harmonics! Who knows what if anything is right for a TR? I certainly don t, so I leave them alone.

Neil Revington

 

So...

 

Menno

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Nice reference Menno. Neil does know his stuff and like many I believe this thread is discussing a solution looking for a problem. (Evidenced by the number who view and the lack of contributors.)

I remember well that Mg 3 bearing cranks had an issue, the same was used In the Morris Oxford....my father hated one he had as a company car....he knew (and did 3 times)how to break a crankshaft. Get it to just 90mph on a down hill stretch of motorway and bang! Goodbye crank

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Iain, I like it, a solution looking for a problem. I read Neil Revington's comment before I started this thread and I have a lot of respect for Neil and his opinions. He has built a successful business from them.

 

The price of a damper from Summit is $US 430. The place referred to in the thread Peter directed me to that makes "rattler" dampers (I can't remember the name) want £450 for one - by the time you've added shipping I ain't (just for you Menno) gonna get no change out of $NZ 1000. That's a lot of money to add something which as Neil said could make things worse, not that they are bad now.

 

Before I was talked into rebuilding my engine (don't ask, it's a long and painful story, there are people waiting to rip you off waiting around every corner these days it seems) I had, many years ago before the dawn of speed cameras done an indicated 100mph along the flat on the M6 ( I think). The tacho was in agreement with the indicated speed, and it was a smooth as you could expect any 4 pot to be, from what you could feel through the floor anyway.

 

So, asking the obvious again no doubt, where do you chaps get a pulley for a thin belt which will fit the boss without buying one attached to an aftermarket harmonic damper. I know moss do a conversion but is around the same price as the harmonic conversion kit.

It's all beginning to do my 'ead in and my iPad typing finger is now very tender indeed.

 

Cheers everyone, Tony

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Tony, Could you get a local machine shop to turn you one up from aluminium alloy - using the old one as a pattern ? Someone on here will be able to give you the profile of the narrow groove, its od and its distance from the rear face. Peter

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