Zane Laverda. Wive's Tale 1. Oiling Issues.

Dellortoman said:
but we're talking about big end bearings aren't we? The rod waggles back and forth but the crank still rotates within the big end. It doesn't come to a stop and start up again each cycle.
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My understanding is that, as the rod goes up say from bdc to tdc the rollers speed up to max speed about mid stroke, slow down to minimum speed as they go over tdc, speed up as they go down towards bdc, maximum speed at the centre of the stroke, and slow down to minimum speed as the cross under bdc. Up to 8000 times a minute, or 133 times a second.

My understanding is that at around tdc when the piston fires it creates enormous point load contact for each of the rollers. Zanes use a 5mm roller, which spreads the "fire" pressure over only a few rollers. Ducati's use a 3.5mm (?) roller which spreads the "fire" pressure over more rollers and therefore significantly less point load pressure???

Regards, Greg
 
I don't know about you blokes, but I get really bored reading through really long threads. They sort of seem to lose their punch, interest and objective.

Does anyone object If I start a new thread to continue on  with"Zane Laverda. Wive's Tale 2. Measurement Issues"

And, at what temperature does a big end roller run at in a hot bike? Does anyone know?

Regards, Greg
 
The more posts the better,those that object can just not read them. Beats those noisy crickets when there there nothing but for sale posts.
 
ghwallice said:
My understanding is that, as the rod goes up say from bdc to tdc the rollers speed up to max speed about mid stroke, slow down to minimum speed as they go over tdc, speed up as they go down towards bdc, maximum speed at the centre of the stroke, and slow down to minimum speed as the cross under bdc.
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Quite right Greg. That's exactly what happens. The angular speed of the connecting rod in relation to the crank pin does vary as you say. So the rollers speed up and slow down, but they don't get anywhere near an "almost stop" situation. In a typical engine where connecting rod length is about 2 x stroke, the speed variation is around +25% to -25%. Or to put it another way, if the crankshaft is spinning at 4000 rpm, the big end bearing will see a cyclic fluctuation from 3000 at BDC to 5000 rpm at TDC.

What effect this speed variation has on the fluid dynamics of the lubricating oil film is another question, to which I don't know the answer. But my guess is that it would probably not be significant.

 
CLEMTOG said:
Did anyone notice that the "mint, immaculate, fully restored etc etc" orange and silver Formula, that was on sale for an astronomic price, was it ?12,000 or ?14,000? now seems to be dismantled and is selling in parts on ebay, well not selling actually.
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I guess, Clem, that the seller doesn't realise that these things aren't worth much, even in bits - and that, simply because there are very few buyers out there!  E.g. ?399 asking price for a front cowl?  :o  Yeah, right ...  :-*

Unfortunately, by the time he does, he'll probably have junked the stuff rather than putting it up for sale at prices the market is prepared to pay.  Shame  :(.

Ciao

Craig (who is pleased to say he doesn't need a front cowl  :))
 
ghwallice said:
And, at what temperature does a big end roller run at in a hot bike? Does anyone know?
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You could safely assume at least at oil temperature... :D  Will be a bit of heat transfer from the piston as well, but as burnt oil is rarely to be found anywhere on the rods, that cannot be very much.  Also, normally no discolouring of bare steel to be found, so temps are well below 200?C (white to yellow-white sets in a 200-220?C, blueing starts at around 280?C).  But, difficult to tell exactly, the rods are entirely copper-coated.

Shouldn't be much friction in there if all is well.  Side clearance of the rod is nominally 0.15mm, max. 0.35mm.  This rarely changes, unless the crank pin or rod bore is tapered and/or the big end too tight.  In this case, the rod can/will wear sideways into the crank web.  Can be repaired, but is a right pita.

Don't think the actual roller dimensions are a problem.  Once fixed, these motors spin happily, almost forever, at max. revs, using stock cages and stock type rollers. 

piet
 
ghwallice said:
My understanding is that at around tdc when the piston fires it creates enormous point load contact for each of the rollers. Zanes use a 5mm roller, which spreads the "fire" pressure over only a few rollers. Ducati's use a 3.5mm (?) roller which spreads the "fire" pressure over more rollers and therefore significantly less point load pressure???

Regards, Greg
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SF, SFC and triples use 5mm rollers - (SFs are short, double-row, SFC and triples long single). Triples and SFCs have integral crankpins, same as Zanes, but the quality of the pins is incredible.

My very generous brother game me his 'old' SFC crank when he secured a new one. The old crank was an early version and had square-ended big end rollers, which dragged on the cage sides and caused skidding and very obvious damage to the rollers, but the crankpins were pristine - I fitted good 2nd hand rods and new dome-ended rollers and the crank has done probably 100,000km. Crankpins are still perfect and it's now being upgraded to Carillos.

Sure, revs will be higher on a Zane, but 8000rpm on 5mm big-end rollers is not an issue, slinger-fed. I agree that oil pressure is limited by the slinger volume. Maybe it's time someone manufactured new centre webs for Zanes!! Better still - transplant a good motor into the chassis ...
 
Just remember:

Pressure = Resistance to flow, so not quite so desirable after all.

Of course pressure can be converted to flow, Mr Bernoulli taught me that.


I do have first hand experience of roller bearing failure. They can fail when they are too lightly loaded and I suspect they skid as a result.

(Example): Bearings on electric motors - one roller bearing and one ball bearing back to back on the inboard or drive end.
Motors ran happily for donkeys years with this setup.
We changed to laser alignment of the motor to pump and bingo! The motors failed on roller bearings one after the other - diagnosis = precise alignment took load off the bearings and rollers skidded.
So we changed to two ball bearings!!!! No problem.

I suspect Laverda had similar thoughts with main bearings on the crank for the triples, unfortunately it seems these bearings were more heavily loaded than they thought?
 
Piranha Brother 2 said:
The old crank was an early version and had square-ended big end rollers, "F" type rollers?which dragged on the cage sides and caused skidding and very obvious damage to the rollers,

new dome-ended"S" type rollers? rollers and the crank has done probably 100,000km.

Maybe it's time someone manufactured new centre webs for Zanes!!
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Interesting point about the end drag of "F" type rollers.

With the installation of "S" type rollers I would have thought that to fit them into the cages, that, as a result of the dome on each end, that the length of the flat area of the roller that runs on the pin would be significantly shorter and therefore increase the point load pressure? Or were the cages different as well?

New centre webs....I was just about to invest in a run of 20 new webs, cnc machined from e36, hardened and ground to oem specs (several thousand dollars :o ), when I discovered that the oem size skf 35*45*20 big end bearing was not available globally. Subsequent enquires to NTN, Koyo, INA (scheaffer), Nadella, IKO (Nachi, Timken) has left me empty handed and I am currently walking down the path of finding rollers and investigating getting cages cnc machined.

Bearing companies won't gear up for small runs, and I can't find a specialist bearing company that does small runs.

Regards, Greg


 
SimonR501 said:
They can fail when they are too lightly loaded and I suspect they skid as a result.

diagnosis = precise alignment took load off the bearings and rollers skidded.
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Another interesting point, and backed with an example!
 
I haven't found great differences between square or rounded rollers used in the Breganze bikes.  I reckon it's all down to which clearance they were initially fitted.  And to whether the pin and/or big end are parallel or tapered.

The cranks I work on are usually high-mileage items, as can usually be seen by the condition of the inner roller bearings.  In these cranks, I often find big ends that still run to too close tolerances, ie, with 0.010mm or less radial clearance.  This often results in the rod wearing sideways into one of the webs.  It only requires the slightest amount of taper on either the rod or pin to cause such a side thrust.  Very rarely are the webs or rods NOT worn when the big end bearing displays such tightness.  The bearings of rods that have worn themselves into the web also show excessive wear at one end of the cage slots, irrespective of type of rollers.  Apparently both types were used over the years, the 120? engines had 2 side-by-side rollers in the same cages, these all had squared ends.  Of course the rounded ends will cause less friction than squared, but the challenge is to cause no friction at all. :D

As the engine components of these engines were not yet manufactured on, by todays standards, hi-tech machinery, clearances/tolerances need to be a bit generous to attain long-term reliability.  A properly assembled Breganze crank will run happily for very many tens of thousands of km without the slightest issue.  Apparently, the Zane cranks were manufactured on clapped out machinery resulting in dimensional inconsistancy, making matters far worse all round.  With todays machining possibilities, far closer clearances could be used in the same basic design.

Greg, now you have realised the obstacles involved, you might more appreciate OCTs standpoint on the issue.

piet
 
Piet,
I do understand OCT's stand on the issue, and OCT is without doubt the best fix for Zane cranks, and will continue to remain so.

I personally am quite stubborn ( and somewhat stupid) when it comes to the DIY project. I am finding researching and analysing the theories and the evidence quite intriguing, and I probably will not give up until I succeed and fix my own cranks, or fail and send a number of cranks to OCT for repair :( :-\

Regards, Greg
 
Greg, you would only be one in a long row of customers going the same route trying that. With an exception of 1 I think, they all ended up going to OCT... Unless you fix 50 or more cranks, the tools and needles needed are way more expensive than sending the cranks to OCT and getting them fixed there.
 
Greg,

I am a pretty good engineer, I have a excellent range of skills and experience.
But I do have at least one weakness - reciprocating combustion engines! Now, there is no doubt if I put some effort in I could be a very good 'engine man' indeed, but I don't feel I have to prove anything.

There are a number of people in the Laverda community that use their considerable skill and experience every working day to keep our machines on the road.
Cranks are obviously very specialised  - why would I not want to use them to get it right first time?
 
Hi Greg,
I looked at this issue ten years ago I started my 668 race bike project.  I too felt that there was a lot of misinformation around regarding oiling issues and I agree with Piet above.
You mention the "Alto" oiling mod.  This was actually first developed by John Baines and manufactured for the 3Cross / Baines Racing 750 Formula.  One of the two Baines bikes was eventually sold to Ben and became the initial basis of the Alto racing effort and Ben continued to make and sell the Baines oil "filter" mod.
I looked into the engineering of the amazingly fast Baines bikes (I think still the fastest ever Laverda race bike round a track) and found these to be a combination of lots of work/trial and error and inspiration.
I spoke to John about why he implemented the oiling mod and he told me about the discussion he had with the Laverda factory about this issue.  The Baines bikes had suffered repeated crank failures  - the team even changed cranks in the pits at several rounds!  John described finding signs of overheating in the failed big ends he examined and so he ascribed this to insufficient oiling.  He also described how he observed the oil flow to be intermittent under some conditions (running the oil system open circuit I think) and his solution was the oiling mod.  John claimed that the mod improved the crank failure rate - and so sixteen years later many bikes now run the "Alto" oil filter mod... (Including 668s!).

John said the Laverda factory never bought into his theory about the oiling and I must say, I wasn't convinced either.  So hardly an "Old Wive's Tale"  - because John Baines' bikes were the fastest Laverdas around -  but hardly a proven fact either  :)

Hope this is interesting, as I believe it is a key source of the "Tale", and once you know all this, you can make your own mind up.

By the way, we always ran the oiling mod on the Inzane race bikes (why not?), but on my road going 668 I run a Champion C302 filter....
Ian.





 
rider668 said:
Hi Greg, Ian, as part of my response I have cut sections of your post out. please advise if you are concerned about this
I too felt that there was a lot of misinformation around regarding oiling issues and I agree with Piet above.As do I
the "Alto" oiling mod.  This was actually first developed by John Baines and manufactured for the 3Cross / Baines Racing 750 Formula.  One of the two Baines bikes was eventually sold to Ben and became the initial basis of the Alto racing effort and Ben continued to make and sell the Baines oil "filter" mod.A really nice and appreciated piece of emperical history
I looked into the engineering of the amazingly fast Baines bikes (I think still the fastest ever Laverda race bike round a track) and found these to be a combination of lots of work/trial and error and inspiration.Where are they now, who has them?
I spoke to John about why he implemented the oiling mod and he told me about the discussion he had with the Laverda factory about this issue.  The Baines bikes had suffered repeated crank failures  - the team even changed cranks in the pits at several rounds!  John described finding signs of overheating in the failed big ends he examined and so he ascribed this to insufficient oiling.  He also described how he observed the oil flow to be intermittent under some conditions (running the oil system open circuit I think) and his solution was the oiling mod.  John claimed that the mod improved the crank failure rate - and so sixteen years later many bikes now run the "Alto" oil filter mod... (Including 668s!).I still don't think it is the answer. If I was to make any mods to the oiling system it would be to enlarge the hole in the main bearing outer race that feeds oil into the slingers. This is a bottleneck to me, and it is (alledgedly) about oil flow, not oil pressure

John said the Laverda factory never bought into his theory about the oiling and I must say, I wasn't convinced either.  So hardly an "Old Wive's Tale"  - because John Baines' bikes were the fastest Laverdas around -  but hardly a proven fact either  :)

Hope this is interesting, as I believe it is a key source of the "Tale", and once you know all this, you can make your own mind up.

By the way, we always ran the oiling mod on the Inzane race bikes (why not?), but on my road going 668 I run a Champion C302 filter....Yes, the old 302 should be enough
Ian.
Click to expand...

Unfortunately, the breatherlyser lock for the keyboard is off, and I'm probably running about 4% bac...oh fuck!

Mains bearing clearances is a major issue. If I use, for a 35mm pin:

IKO calculations. 28 to 40 micron
NTN calculations. 18 to 33 micron
Recommendations from a lad that builds Ducati (Super) race bikes. ! micron per mm, therefore 35 micron
A Harly bloke I know, 20 to 30 micron
An experienced triple laverda bloke I have recently met 15 to 18 micron

And, it gets blown out of the water by a lad with an enormous amount of experience with old bike rebuilds, including the Irving Vincents, and V8 supercars, who uses the FAG recommendation, which, based on that, would be happy with up to 75 micron clearance for a 35mm pin. (which is way outside the Laverda recommended wear limit)  Where does it stop, where does it start?

I am undecided on a lot of the above, and if I was to set up a Zane, at the moment, I would look at about 25 micron for a street bike and about 37.5 micron for a race bike.

BUT, I THINK ALL OF THE ABOVE IS BULLSHIT. I don't believe the clearance is the major issue. I think it is the roller cages. They are copper coated steel. They are made for the id of the rod, and not the od of the pin. The clearance in a new motor would be about 12 thou total inside the rod. a bit of rocking, some heat expansion, the rods are not that solid, so a bit out of round under high rpm, (impounding on the issue). steel will pick up on steel, the cage feathers, the cage slows, the rollers slow, the rollers skid, and WTF, you've got a fkd crank, ( I need another beer..)

And " her indoors" wants me to watch telly with her. I hate telly....

I'm just trying to promote thought, feedback, and conversation....:)

Regards, Greg












 
I'll buy into this, no direct small Laverda twin experience but 40 plus years of roller bearing cranks...

Cages - rod guided every time for me. The outer side of the cages is the one which will have the most oil around it.
I've seen quite a few cages seized onto the pin over the years...
Cage finish is important too. If you're not using alloy cages but steel, silver plate the cage. Makes a world of difference.

From what others have posted about the accuracy of the later OE crankpins I'd have no hesitation identifying this as the source of problems. Of late years most of the roller big end pins I've seen have been miles better than even say the 1980's.
Clearances - largely depends on how stiff your crankcases are...
I've seen new KTM bigends at .008in...
Anything from .002in to .003in radial clearance is fine.

Oiling - roller bearings don't need much oil. Irving postulated that if there was an optimum amount of oil, there should also be a "pessimum" amount which would lead to failure. In his experience it was usually too much oil that could be a problem.
Cooling the bearing should not be done exclusively by oil - it needs a good airflow through the cases as well.

Just my 2c worth...
 
I'm not an engine rebuild expert, nor have I studied roller bearing design in any kind of detail. But I find the subject interesting.

GregT
I'm not sure what you mean by "rod guided" bearing cages. I'd have thought the cage is guided by the rollers and shouldn't touch either the rod or pin. Or more accurately, it's the other way around. The cage is there to guide the rollers, but it is held in place by the rollers themselves and can't move very far radially.

The cage may move axially, but only until it comes in contact with the faces of the crank webs. A sliding contact, but one of minimal load. I suppose you could think of it as guiding contact rather than sliding contact.

The only other sliding contact that should happen in a roller bearing is roller against cage. But in a healthy bearing there shouldn't be any force in that contact so it's no big deal. However, it could become a problem if the bearing gets worn and rollers and/or pin get out of shape or alignment. In that case there may be forces trying to steer the rollers off track which will put load on the cage and eventually beat it to death. Once the cage fails, I can't imagine the bearing doing any more than a few revolutions before something catastrophic happens.

Other Greg (ghwallice)
If you can still write a sensible and well thought post with few spelling mistakes while pissed, you're a better man than me.  :D

 
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