Crank Bearings - do we have the correct info?

[DangerRanger]

Ball Bearings to handle axial and radial loads combimed, where we all know that any axial load on a roller will cause it to fail quicker, and infact causes bind. the motor torque and load from tranny etc cause axial load in the motor and we all know the cases and plates flex...some considerably, so the ball makes more sense....but if you could gurantee that the crank spins 100% true, the plates and case are aligned perfectly, no axial load is being placed on crank then yes the roller would be better...but since this isn't a perfect world nor a perfect motor, the ball bearings are a better fit, of course this is IMO, and also info from several motor builders, and after talking with a couple of our mechanical techs at work. so all quads have round tires...and cdale decided to use octagonal...will they work....well yes, but not near as well as the tried and true round wheel.

[Jaybr]

If you want to use tires as an example, how about if you put Z rated Corvette tires on an F250? The Z's are rated for much better speed just like a roller bearing, but nowhere near the load rating of the truck tires (like a roller bearing). They will probably work ok as far as rolling the truck, but what happens when you load up the bed of the truck or pull a large trailer?

Using this example it's obvious the Z rated tire is not right for the F250. It's obvious because we can easily calculate the loads presented to the tire on the F250 under various conditions, and we can check the specs on the tire and determine if it meets requirements.

All I'm asking for is the same calculations here to determine the best bearing for our motor, until then I'll assume the engineers knew what they where doing.

[cannondale27]

I was looking into the physical size(Dia.)of our crank mainbearings
they are small compared to most 4st.

Here is a Banshee main bearing which is not only bigger but there are more of them.

[cannondale27]

Here is a pic of YFZ crank bearings. Didn't have a bearing on hand to compare them to but they are a lot bigger than even the Banshee one shown.

[cannondale27]

Other one. Also notice how the screws which hold the bearing tabs in are peened into the tab. (plug for stage8)

[protraxrptr17]

Don't really have much knowledge on what stresses each bearing can withstand. I do know that I have seen the cages fail in the ball bearings several times though. Seen it happen twice in a Banshee as a matter of fact. It just seems like one more thing that can come apart. I would think that a roller bearing has more surface area per roller therefor having a higher load capacity. But I'm no expert so.......

[cannondale27]

That's my point. If these big ball bearings fail it would make sense to me that smaller ball bearings like would replace stock Cannondale roller bearings would fail sooner.

[claas900]

..I may be wrong here, but I think a larger bearing turns faster, not in rpm's but in mph faster..so a larger bearing may take the load better but its turing faster..but again that shouldn't matter..if it's meant to go 15k rpm's then it should be fine..But I also think there's a fine line when building a motor, a larger bearing is more friction which is hp loss...so I think they keep that in mind also?...I dunno.. But I do know the YZF isn't the answer..how are those Hondas doing again?..lol

[cannondale27]

Hondas seem to be real good but they are not as fast as even a stock Cannondale. Maybe reliability the limits of 4st 450cc in quad have been reached at about 40 hp?Maybe Honda knows this.Something made them detune it so much!
A larger bearing mph wise turns slower than a bigger one=less heat.

[timbomoose]

Allmost all, if not all, late model snowmobiles use roller bearings on the clutch side where all the drive force is. A lot of these motors are 150+ horsepower.