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February 2nd, 2014, 07:39 AM   #41
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Re: Definative main bearing thread

Originally Posted by bushmechanic
Hey John

that's crazy stuff from them sending out bikes with no crank end float

one thing Ive not mentioned yet is that sometimes the bearing outers move inside the cases when the cases are hot and settle at zero end float as the bike cools down

then the next time you start the bike you have zero end float until the cases get at least as hot as they were when the bearing moved.

happened to my bike once.. at around 80 hrs I think .... i thought it was going to be stuffed for sure ... could not get the bearing to move back until it bike was really hot.. took 30 min easy riding before the bearing moved again and I got the end float back by tapping the end of the crank with a mallet.

so if you rev a "warm" engine that happens to have settled with zero end float....
Interesting Just to ask a stupid question, can you tell what the end float is without splitting the cases? I'm assuming it wasn't that you noticed at 80 hours that the bike was acting was funny, split the cases, saw the bearing had moved, put it back together and gently rode it back into place ..?
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February 2nd, 2014, 02:27 PM   #42
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Re: Definative main bearing thread



just remove the ignition cover, put a dial gauge on the crank and measure the axial play.
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February 20th, 2014, 11:42 AM   #43
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Re: Definative main bearing thread

Just out of curiosity, what is the downside if you have too much axial play in the crank?

Earlier in this thread was mentioned that setup where one side bearing was locked in the crank.
What are your opinions on doing that on this engine?
I mean if you make a spacer between the left side bearing and the gear so the crank stays locked in the left side and the right side is free to move on a roller bearing?

I did that to mine and it hasn't broken down yet...
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February 20th, 2014, 02:32 PM   #44
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Re: Definative main bearing thread

none that I know of

however there have been some failures of the inner race where the lip has broken off (with "normal" axial play")

i think these failures are due to crank spread and lack of support of the lip but in theory the crank can develop more inertia if it can move further in the axial direction

however most of the development and testing of different mains configurations we have access to comes from the RFS builders with 540 - 640cc builds (there are simply more RFS engines being big raced and tuned than bergs) and none have found any problems with the mains at crank end floats set up to 1mm.

I ran 1mm float on rollers for 100 hours in my 700 nothing went wrong.

the setup you use I think is great if it works for you, and I'd like to be crystal clear that I think anyone who has found a setup to work for them should be happy with it.

IMHO the NTN rollers are the best option they are cheaper than the SKF bearings and to date there is no record of them failing in 1000s of builds even with floats down to 0.15 - 0.2mm. Orangeberg noticed the KTM race team using them in the finke desert race here in aust as they were fitted as OEM parts to the ktms.. no failures in the RFS bikes... the bergs in the same race fitted with SKFs had issues at similar end floats.
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February 20th, 2014, 02:34 PM   #45
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recap on ball/ roller

the advantage of ball on the drive side in theory is that it can handle misalignment + axial loading + radial loading all at the same time better than a roller

I wouldn't use the ball/roller personally for 3 reasons

1) because the ball bearing has a much lower load rating than the rollers around 22Kn for the ball, 44Kn for the roller and the spherical rollers I use are 84KN http://www.vxb.com/page/bearings/PROD/30mm/Kit10509.

Thomas of enginehardware found it was a good setup if changed every 100 hrs .. but generally people find the ball does not last as long as a roller

2) while the crank is locked to the ID of the bearing the outer of the bearing is not locked to the case and is only a very tight fit.. if it does move you have a problem .. potentially zero endfloat. (see pic in quote below)

3) the axial loading due to crank spread is shared between the 2 bearings so no matter what you put on the drive side, the ign side still gets the same axial loading.



Originally Posted by bushmechanic
the first one that was popular was the use of a KTM crate engine deep groove ball bearing on the drive side and an NJ 206 on the ignition side.

many jap bikes use this idea but they fasten the ball bearing to the cases and also to the crank so the crank cannot move.

they also have about 2mm room between the rollers on the roller bearing and the lip or.. no lip at all so the rollers never contact the lip in these bikes

in the husaberg the ball bearing is just a stupdly tight fit in the cases and on the crank but the crank is not actually locked in position and can move.. you wouldn't know about it though till the roller bearing failed.

it is also very difficult to measure the space between the ends of the rollers and the nj roller bearings lip... you still need the same amount of room for the crank to expand because the axial loading is shared by the 2 bearings and the NJ bearing still gets squashed into the lip

it has worked for some people but i have seen it fail in 20 hours
this shows the degree of force that is pulling the bearing out of the case

Originally Posted by bushmechanic



check how the bearings can be pulled inward out of the cases

Originally Posted by Bushmechanic
Interesting experiment i tried to retain the outer race of an Nj2206 with an alloy plate





you can see its cracked. the outer race of the bearing has been pulled
out of its bore by 1.5mm and with enough force to break the retainer.

I find this interesting as there is no easy way to apply a force to the outer race
in this direction. there is a lip but it can only push the bearing into its bore not
out



also I was running 0.8mm crank endfloat so for the outer race to move any
more than 0.8mm out of its bore means there is some extraordinary flexing
going on.
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February 23rd, 2014, 12:18 AM   #46
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Tech description of Types of Misalignment

if you enjoy reading technical stuff

this comes from The American Bearing Manufacturers Association standards and explains the different types of misalignment and how they affect the load capacity of roller bearings.

in short 2 main types of misalignment and 3 resulting less than ideal scenarios to explain how overloading occurs in the mains and causes the ends of the rollers to dig in

I posted it up in 2009 somewhere but it should go here as well.

ABMA standards state that optimum dynamic capacity C values refer to roller bearing mountings so designed and executed that uniform load distribution over the active roller length is assured. it is further stated that if misalignment is present a reduction in the capacity value should be made.

2 types of misalignment: A location misalignment, and B deflection misalignment.

location misalignment implies misalignment in a plane at right angles to the direction of the load. this type is assocoated with skewing of the rollers on the roller track and resultant distortion of the contact area. location misalignment may arise as a consequence of 2 bearing supports some distance apart being out of line. though very undesirable this type of misalignment is not as serious as deflection misalignment and does not result in large bearing capacity reduction.

Deflection misalignment misalignment in the same plane as the direction of the load. this type is ascocitaed with a tendancy toward digging in of the roller ends on the roller tracks with resultant high stresses at these points. with straight non crowned, cylindrical rollers this condition is much more exaggerated than in designs incorperating crowned cylindrical rollers.

deflection misalignment is encountered when moderate to heavy external radial loads exist on small diameter shafts and/or bearing supports are remote from the point of load application
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April 9th, 2014, 10:42 PM   #47
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This is one helluva thread, I'm very happy I read it before attempting any rebuilds.

I have seen it mentioned somewhere, as usual having difficulty finding it again, about the inner races spinning on the crank. Is this the same cause as the bearing failures, the rollers pinching the inner race and spinning it when the crank flexes, or would it be because the fit between crank and inner race is not tight enough? Or maybe a little bit of both.

Also, regarding the main bearing cages, what would be the best cage material, brass, poly or metal? I would say poly would be safest in case of a bearing failure, I can only imagine what damage a collapsed metal cage can cause...
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April 10th, 2014, 02:54 AM   #48
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given how tight the fit on the crank is IMHO they can only spin if the bearing is refusing to do its job

both the crank and the inner race are steel so the interference fit can only really change if the bearing is the main heat source .. a ball or roller bearing overloaded axially.

if the bearing is a ball race or a spherical roller then there actually needs to be a slip fit to allow axial movement without damage

yes poly cage is going to cause the least damage but is more prone to embrittlement from heat, and not as good at maintaining alignment of the rollers, id also think that in these bearings the rollers and the inner races fail first not the cage.

Ive used brass caged "rollway" nj206s in C4 they were very good, the nachi 22206s have a steel cage
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April 10th, 2014, 04:07 AM   #49
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What would one do regarding the slipping inner race? should I change to a ball bearing setup in this case, or try rechroming that part of the crank and machine it back up to spec?

I noticed the Honda 450X inner race is a slip fit on the crank, it can rotate freely by hand, but then I suppose the crank was made to work like that, so having a slipping race on the BerG crank would not be ideal..
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April 10th, 2014, 08:59 PM   #50
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I know the Honda engine.. the roller bearing never sees any axial loading because the ball bearing on the other side is fastened securely to the crank and also to the case, there is 2mm+ room between the end of the rollers and their "lip" so the inner race doesn't have a reason to slip and because its loose anyway there is no damage caused if it does slip.

I use a 1/2 thou slip fit for the spherical roller bearing this works very well

IMHO they only spin on the crank if there is something wrong so I run bigger axial play to reduce axial loading

after that you have 2 options .. make the inner race proper loose and let it slip = less damage to crank and bearing if overloaded axially

or make it tighter and try to stop it spinning which is just fighting with the problem, it will surely stop the race spinning and reduce the radial clearance in the bearing but its not really an elegant solution.

something to watch is the radial play, not sure if I put the specs above but the recommended radial clearance as installed is 0.04 to 0.07mm.

I tried to tighten up the inner race on one bearing by heating the inner slightly and dropping it over the crank with loctite,

radial play was 0.02mm .. this bearing was on the less loaded ignition side but wore out more quickly than its partner which had 0.05mm radial play.

from that I figured it is not possible to get enough crush to stop movement unless you go to a C4 bearing because the radial play is reduced when you increase the crush
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