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bulldog426
05-24-2013, 12:07 PM
well a while back i rebuilt my boat engine, a 2 stroke and it was my first time tearing a boat engine down, and rebuilding, but i figured to myself that i have rebuilt car engines, 4wheeler engines etc before so i figured the boat shouldnt be hard, well i found the engine has roller bearings for the rod. and main bearings, which recieves lubrication from what litle oil gets to it from the fuel mix of the very thin oil, plus the bearings are packed with lithium grease on assembly, well it got me to thinking, why couldnt' we have v8 race engines with the cam, rod, main and wrist pins with roller bearings and either run a really thin oil, or pack the bearings every now and then? i mean on a race engine that would be torn down and rebuilt on a regular basis anyways, it would free up alot of horsepower if one would do that... i think it's a pretty good idea for a manufacturer to start making these for engines, you could practically eliminate the hp drain from an oiling system, plus all the freed up horsepower from less friction, plus not to mention the extended life from less friction and heat

John Kunkel
05-24-2013, 03:14 PM
Roller bearings might have less frictional losses but they won't handle the load that a plain bearing will due to the small contact surface of the roller.

bulldog426
05-25-2013, 12:29 PM
well think about roller bearings in a vehicle application, trailer etc, the bearings on my car trailer can't be any larger than what could be put in an engine and i've hauled some really, really heavy loads for quite some distance on them

Dart 360
05-28-2013, 07:43 AM
Rolls Royce were running roller bearings a few years back, not sure if they still are and those horrible vw's had a modification also to fit roller bearings on their flat 4's. the bearing surface is larger than you first might think.

340_GTS
05-28-2013, 12:09 PM
Commonly found in Formula One, also many hi-perf motorcycles. They use needle bearings, and I'm sure they are lubed just like any other bearing with engine oil.

bulldog426
06-20-2013, 03:07 PM
it would still reduce alot of friction and free up a good bit of power, and added durability, think about the extra durability and added power just by going with a roller valve train, imagine every rotating part having roller bearings. and you could run a thinner oil which would free up alot of power as well, i mean they have 300 horsepower boat engines that run the roller bearings that only get oil from what little bit of the thin thin oil is mixed into the gasoline that seeps past the piston rings and lubes the bearings and they last for thousands of hours. i bet one reason why companies don't make em is because it would dramatically extend engine life therefore people would run their engines alot longer not making the car manufacturers money when they want to replace or rebuild the engine, or the whole car. that is in a passenger vehicle sense... or imgaine the durability and life of a cummins with roller bearings

Dick
06-20-2013, 05:21 PM
I believe the bearings you are describing in the outboard are needle bearings, not roller bearings.

The bearings in your trailer or car axles are tapered roller bearings.

John Kunkel
06-20-2013, 06:31 PM
Things to think about when considering roller bearings:

-With rollers arranged around a shaft, only a small portion of the roller contacts the shaft whereas a bearing makes full contact all around the shaft.

-The space between each roller is a huge oil leak when using a pressurized oiling system, not an issue with two-poppers that carry the lube oil in the fuel.

-Most engines that use roller bearings are high-revers, not known for making lots of torque, so the small contact area of the rollers is less of an issue.

chirorod
06-21-2013, 08:19 AM
I believe that Mercedes experimented with needle bearings in the 50's but went back to the inserts. Somehow, the needles can't handle the loads. Probably, as John says, there's a lot more load area with an insert.

340_GTS
06-21-2013, 10:33 AM
When a needle bearing lets go, you will have many tiny fragments of hardened steel circulating thru the oiling system. Imagine the chaos this will create in an engine. Serious damage everywhere!

DartGT66
06-27-2013, 04:41 AM
In a 2-stroke engine, with the fuel/oil mixture doing the lubing, there is not much choice, it can't be done with a regular bearing that needs pressurised oiling. Also there is less load in a two stroke compared to a similar power level four stroke.