Thats wrong.

Personally, no I dont know of any Romac balancers that have failed. I have used a few of them on various engines. From the engines that I have built and fitted these romac balancers to, I have had 1 that needed to have a very small amount taken out of it (small drill mark) when the crank etc was balanced.
I like them but in the end bit is up to you if you want to invest in one of these balancers/damper/etc.

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http://www.youtube.com/watch?v=nDMkVq1jRGU

Wait !!! I just found my reading glasses. This changes everything.

I'll have to take back everything I said before. Never mind.

& , on a side note but still relevent to balancer failures & (Just for anyone interested in learning about "real life" experiences & not just reading torsional vibration websites)

another reason why balancers can fail --> sometimes (the average Joe/Jane Doe engine builder with very little real life mini engine building experience) can/will leave the shims on the front end of the crank when sending it off to be hardened,,, making them very brittle,,, now """IF""" they`re not removed before building the donk, then they can (& usually do) break up, fall out, & the balancer will obviously come loose,,, vibrate it & the crank to death.

Now this can (& quite often does) also effect the centre main bearing & the other end of the crank (Flywheel & clutch assy)

I don`t actually use those shims myself at all when building mini donks,,, i set the crank gear hard up against the crank & align the cam gear by means of using a suitably worn cam thrust & machining the cam gear to line up with the crank gear

this helps """reduce the chances""" of the front pulley comming loose

Hope that helps anyone who is intending to build a mini donk in the future

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No offence intended here but--> anyone writing a book about minis 30 years ago may not have experienced such worn or stuffed-with components as we are finding these days.

You should put your heart & soul into everything you do.

Matt,

If its the varying quality of the replacement gearsets which upset the alignment....if you machine the cam to suit the gearset, doesn't this cause a problem at the next timing gear change out further down the track?

Shims removed before hardening (or replaced if dodgy) should remove the problem altogether?

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SooperDooperMiniCooperExpertEngineering

All garage work involves equal measures of enthusiasm, ingenuity and a fair degree of irresponsibility.

just as using too short a bolt or failing to Loctite or safety wire the damper bolt can cause the damper to come loose and wreak havoc.

Mick, i machine the """cam-gear""" down to align it all

i leave the cam & crank alone

but you "usualy" need a slightly worn cam thrust plate to do it,,, it`s not an issue tho, been doing it this way for about 35 odd years.

& yes if you take the shims out before hardening then cool,,, but my thoughts are that why should you have something in there that doesn`t need to be in there??? & also why have something in there that "could" still cause a problem, if it don`t need to be in there?

It`s not a difficult job to do & it really is the way to go,,, the factory add these shims for "ease" of, & speed building a few million mini engines,,, there are other varia\bles like the different thickness of different batches of front plate gaskets etc ,,,

Shimming the crank gear is definately not the best method tho, """Especially"" if the shims have gone through the hardeneing process with the crank.

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No offence intended here but--> anyone writing a book about minis 30 years ago may not have experienced such worn or stuffed-with components as we are finding these days.

You should put your heart & soul into everything you do.

I gotcha now, I misread what you meant...
It would be nice to own a surface grinder one day. There's so much you can do on a mini engine rebuild..

cheers Matt

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SooperDooperMiniCooperExpertEngineering

All garage work involves equal measures of enthusiasm, ingenuity and a fair degree of irresponsibility.

great discussion guys

i have the following questions

* how well known is it about the backing plate being centred & the holding straps remaining in position when the assembly is broken down after balancing?
do all balancing shops know this

Of the 3 cranks i have had balanced in the past, this was only mentioned once & this guy ended up welding weight onto the diaphragm to correct the imbalance on the diaphragm

*how good are the std BMC damper pulleys? Matt says he has seen enough failures, are they any good if they are in good condition?

*what is the story with bike engines?
do they use damper pulleys?

we are all learning

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1275

I have had a number of mini engines balanced over the years and i have balanced a few myself along with various hotted up 6 & V8 engines when i worked in the jobbing shop at RPM engines, using a Repco machine.
I allways use supply a new diaphram and a new clutch plate when i have my engines done and i cant recall any weight being added or removed from a mini diaphrams, they are only ever marked for correct re assembly. I use a std harmonic ballancer or a 'S' type depending on the engine and rarly do these need more than a small amount removed. Most of the weight comes off the crankshaft, & usually a small amount of the flywheel, tho usually the flywheel is new and is very good to start with.

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Have a Nice Day.
If already having a nice day please disregard.

OK now here is another little teaser. Who has the clutch plate independantly balanced before assembly.It is not going to remain in the same position when the whole assembly is initally balanced.

Now another thing to have a look at. If you have a old flywheel or a back plate accurately measure the width of the wear mark from the clutch plate, then measure the width of the clutch plate friction material.

Back to subject about dampers.I have seen many dampers fail on allsorts of engines. In most cases [apart from ones that have rotted away] the damping material has broken down. IE the rubber has cracked or the silicon fluid has leaked out. In all cases it has been due to some ab-normal vibration in the engine,bent rod/crank broken piston or some type of clutch /pressure plate problem.

RULE No 1 never asume that the damper has "just worn out" I saw what happened to a blackstone 8 cyl. engine that had a damper that came loose and fell to bits. The engineer assumed that the damper was at fault. So fitted a complete new assembly and started the engine. It run well for a couple of days then broke the end off the crankshaft.

Years ago when I was racing my mini during practice the damper came loose[the eng had been completely re-built] I thought I forgot to tighten it. Next day ,first race and the clutch felt "funny". Second race and the whole flywheel/ clutch exploded and bits came thru the fire wall.
Thats when a engineer showed me the clutch problem.The bolts on the metal straps had worked loose and the back plate was moving around.
After that all my flywheels/clutches were matched and machined to the crank.I have done this on all the engines I build up. not just minis.

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Research is the difference between speculation and investment. Anyone who copys some one else will always be second
www.minisprintgt.com

Mini7boy I am taking a guess that this is your response to my answer of your ORIGINAL question?

Below is your original question which from the way it has been written is all "hear say" no physical proof or any fact has been put in the below question/statement.



My answer to your question is below which I guess is what you were looking for as it is from my experience from using these balancers/dampers.


-------------------------------------------------------------------------------------



Do you think in your obviously vast knowledge of mechanical components and thier job on any engine the fact that it was being raced (high rpm) and the crank (and possibly other components) was obviously not very healthy and or the engine was either quite worn or very poorly put together may have contributed to the "impending failure"
(as you said) of the balancer/damper?

Now a simple Yes or No will suffice mini7boy with out trying to baffle everyone with bullsh1t with your vast mechanical knowledge as you have been trying to do previously, as you more than likely wont get this info out of a book but you may find something on the net....with pictures to help you understand what you are talking about.

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http://www.youtube.com/watch?v=nDMkVq1jRGU

All this talk is scaring me I had every thing lightened and balanced. HB rebuilt and balanced -the whole sysem balanced together (except the clutch plate) I hope GR put the HB bolt in proper and I hope I've tightened the clutch straps and .......

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David L


My greatest fear in life is that when I die my wife will sell my Mini and tools for the price I told her I paid for them!

hee hee,,, well,,, it`s all just a matter of making sure you build the engine to the best standards you can,,, components are good & correct clearances addhered to,,, you can only do what you can do,,, "IF" theres a failure of some sort , well then Sh!t happens,,, you`ve done what you could & all these old bits & pieces can fail from previous fatigues

David, you are sooo right

73GT,,, centering the clutch package is a Must & is quite well known throughoiut the mini scene,,, most "Normal" cars (as David said) have their diaph doweld to the flywheel so they have it a little better off in that dept, reducing the chances of being "Out-of-whack",,, but we as mini repairers & mini engine builders "MUST" take care when setting the clutches up that`s for sure.

The typoical engine balancer (the bloke who actually balances the engine componenets) will "Usually" do a fairly decent job,,, however i`ve known some guys be a little (how should i say this?) Maybe "Casual" could be a good description

The Stock mini balancer is generally pretty good,,, however, they`re getting old,,, they have usually had a good long swim in some oil leaks over the last 500million years of use & abuse, so you can bet there are some pretty crappoy old things still "floating" around on mini donks today ("""Floating""",,,hee hee,,, i`m good hey ? ) the best "Factory" type (in my opinion) is the "S" type 2-piece one, they`re pretty strong, can usually handle 8000rpms & most i have here are (altho very old) still in good nick,,, & yes they all need to be balanced with the rest of the recipricating mass (ie: crank, flywheel etc) It would be lovely if they (each seperate part of the rotating package) were all balanced lovely & true seperately & then add each item to the crank & balance it, then add the next item & balance again & so on & so forth,,, but i believe that these days you will find that they balance the crank, add the flywheel & front pulley & balance again & they reckon their job is done we`re all slowly becoming a very lazy race (sad but true)

most of the late Bike engines have very very small flywheel (almost none) & also the crank assy (pistons & rods) are very small & very lightweight in comparison to the average mini donk, Also they are very finely machined & balanced at their respective factorys,,, so less need for vibration dampeners in them,,, the smaller the donk & the more fine tuned & balanced they are, the less need for more weight to be flung around off the end of the crank

Mick,,, no worries , we all miss-read stuff now & then hey? & only a lathe is needed to machine the cam-gear,,, it takes a few minutes to clock it into the lathe nice & true & even less time to skim some meat off it... just have to measure it right first easy-peasy

Ballistic,,, now now,,, be nice

Edit--> Hey , Cranks can (& do) just break,,, previous fatigue in old cranks making them crack & break is becomming more & more common the older & the more abuse we give them... sometimes they just break... sometimes there is no other reason,,, but other times there is a path of destruction which can be "read" by looking very hard & long you can trace the cause back to it`s origin

Don`t forget the fact that Mini cranks swing in only 3 main bearings,,, "Normal" cars have 5 or more (depending on the number of cyls) so they have it a fair bit easier than our flexy wobbly p!$$y design,,, all we can do it "Let" them flex,,, if you try to make them or force them "NOT TO" flex,,, then you will surely end in tears somewhere along the way.

let em swing i say

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No offence intended here but--> anyone writing a book about minis 30 years ago may not have experienced such worn or stuffed-with components as we are finding these days.

You should put your heart & soul into everything you do.

When I had my flywheel disintergrate I did modifications to the set-up that I now know caused the problem. Things like just machining off chunks to lighten it without understanding what happens when things are changed and doing it properly.

After a very knowegable engineer explained the problems and many years later when I studied engineering I was able understand the physics and calcs to the practical aspect.

What we have is a 50+ year old designed engine that was intended to just putter around with some old granny driving the car, not some rev-head screwing the ring off it. Things break no matter how carefully it is assembled. I have blueprinted race engines and had them blow-up and other engines that are thrown together over-nite and hang in for many races.

As for a damper failure, yes when they are past their useby date, but good units when they have failed there has been some other underlying cause to the failure. Do not just assume the manufacturer is at fault, do a complete check of all the componets as it may occur again.

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Research is the difference between speculation and investment. Anyone who copys some one else will always be second
www.minisprintgt.com