Roller bearings for the stationary gears

[vex]

Is there any reason why there hasn't been any productions of roller bearings for the stationary gears? It would seem to make sense to me to reduce friction even more by using low profile roller bearings on these locations, but then again I know nothing of the forces or loads those bearings see.

Maybe a ceramic ball bearing to support the eccentric shaft? Good idea? Bad Idea? Reasons why?

[vex]

No opinions on this? I'm surprised. I'd be very interested in hearing everyone's thoughts on it. My personal opinion is it would be a significant reduction in friction forces, and if similar use was used in the rotor bearings it could significantly decrease friction and other taxing mechanics of the motor. However if the bearings were to fail, i'm not sure how well the engine would hold up.

[NoDOHC]

I would have to dig my machine design textbook out, but I think that it is hard to beat a well-designed journal bearing. Roller bearings would probably give less resistance, but would they last as long?

I am sure that Mazda used journal bearings because they are so much less expensive than roller bearings, but I can't help thinking that there must be another reason.

I have yet to hear of any production engine that used roller bearings for the main journals or the rod journals.

[vex]

I'm doing some more research on it, but it appears roller bearings on cranks are not all that unfamiliar. Supposedly race car engines use them:

http://www.finishing.com/301/90.shtml
http://forums.autosport.com/showthre...threadid=93001

However my research shows that F1 teams use high tech journal bearings.
http://www.powerenterpriseusa.net/pr...l/f1_metal.htm

As far as I can figure, piston engines cannot use roller bearings that well because they have too much orthogonal loading (Forces directly perpendicular to the axis of rotation). I don't think rotaries would suffer from this as the power stroke causes only a rotation of the parts and not a direct perpendicular movement of rotor against the eccentric shaft.

If the bearings is low profile enough, I think it may prove quite applicable to our engines.

[NoDOHC]

A Journal bearing can do nothing against orthogonal loading either. (Unless it has a lip on the side of the journal.)

It is an idea worth looking into. Although I would guess that ceramic housing coating would do more for decreasing rotating losses.

[vex]

Originally Posted by NoDOHC

A Journal bearing can do nothing against orthogonal loading either. (Unless it has a lip on the side of the journal.)

I'm not talking about concentric loading of the axis but orthogonal loads say from the piston engine firing directly perpendicular to the crank shaft.

It is an idea worth looking into. Although I would guess that ceramic housing coating would do more for decreasing rotating losses.

Absolutely. I think the next step after ceramic coating the housings and rotors would be the bearings and reducing friction there. Just some thoughts though.

[vex]

According to the SAE papers, the 13B already has lower friction forces applied to it than a Normal Piston engine. One would wonder if applying these factors would further increase the lead on reducing internal friction of the engine.

Also, Mazda has done some major work on the Housings which I didn't know they did. Apparently the housings have measures beyond the Cr plating. They have a solid lubricant which helps eliminate wear as well as micro pores to help in oil retention.

Would ceramic coating the housing be beneficial? That is now up for debate in my mind.

[classicauto]

A few people run cermet housings. I know charlie (busted7) runs a pair in his engine. 20lb spring, big turbo, 500whp on pump. There's upsides and downsides but I think in the case of the housing the gains or losses will be minimal.

The argument can go two ways:

1) By doing the coating, you're keeping more heat in the chamber, losing less energy to being absorbed by the housing, make more power.

2) By doing the coating you're keeping more heat in the chamber, raising the chances of preignition.

The friction factor I don't even know. Personally I think ceramic seals (which have a proven lower friction coeficient then OEM steelies) in OEM housings is the best - mathematically - for reducing friction with regards to housing vs. apex seal. I can't find any info saying that JHB cermet *IS* more slippery then the factory stuff, plus who knows if it holds oil as well, etc etc.

Personally, with the problems I've seen first hand with Cermet housings (older versions, but nonethelss) I wouldn't want to risk it. Buy a pair of OEM's and you know what you have. Its not like getting them coated makes it any cheaper - a pair of useable housing + coating (JHB) is about equal to a pair of new, plastic bagged, housings from the mother ship.

[Cp1]

i can give you all the answer you need. roller bearing slow the movement considerably when wet (oiled). this has been tried before with pretty dismal results on piston engines. first problem the strength of the bearing needs to be pretty good as the forces acting on it are extremely high. .

Secondly a roller bearing increases friction causing more heat and wear. this is simply because an oiled journal bearing the two surfaces dont actually touch when moving they are "sliding" on a very thin layer of oil which is also the same way some screw compressor superchargers work. a good hone will provide as good of benefit as a roller bearing without the cost or difficulty. yes it has been done but it is not economical nor is it durable.

F1 cars have used them true but the engine is also designed to last 1-2 races max and all of the fluids are pre-warmed before going in because of tolerances. your motor is nowhere near this and speaking from experience i would not recommend this.

Edit i have been wanting to try boring out the stock journals and replacing with a fitted aluminum bronze bearing sleeve as aluminum bronze is much more durable and is much more slippery (can be honed finer)

[vex]

Originally Posted by Cp1

i can give you all the answer you need. roller bearing slow the movement considerably when wet (oiled). this has been tried before with pretty dismal results on piston engines. first problem the strength of the bearing needs to be pretty good as the forces acting on it are extremely high. .

Secondly a roller bearing increases friction causing more heat and wear. this is simply because an oiled journal bearing the two surfaces dont actually touch when moving they are "sliding" on a very thin layer of oil which is also the same way some screw compressor superchargers work. a good hone will provide as good of benefit as a roller bearing without the cost or difficulty. yes it has been done but it is not economical nor is it durable.

F1 cars have used them true but the engine is also designed to last 1-2 races max and all of the fluids are pre-warmed before going in because of tolerances. your motor is nowhere near this and speaking from experience i would not recommend this.

Edit i have been wanting to try boring out the stock journals and replacing with a fitted aluminum bronze bearing sleeve as aluminum bronze is much more durable and is much more slippery (can be honed finer)

Keeping this in mind, it seems counter intuitive with respect to spinning assemblies. I'm thinking of the recent technology that has occurred with ceramic ball bearing setups. Especially in turbo chargers. Journal bearings were old school and couldn't really effectively touch what the new ball bearings reach. The friction is kept low by the materials used, same as you have raised.

The viscosity of the oil in the bearing would definitely play a huge roll in the friction reduction, however that same viscosity is in the journal bearing and as it heats the viscosity reduces which also strips away protection from the bearing. Given those facts would we see a big decrease in friction loses? Probably not. But I'd still like to see real world tests performed on this.

I think biggest development would be ceramic ball bearings since their finish and heat resistance is top notch. Couple this with the ability to handle the forces and it is a rather nice setup to run on the bearing.

Granted though this is all conjecture I would love to read the SAE papers you have on this, or any articles concerning this.

[Cp1]

ceramic though extremely durable is also extremely brittle and cant put up much of a fight with the forces of the rotating engine mass but they are ideally suited to the high wear and low rotating mass of a turbo turbine.

If you take any engine even a rotary for that matter and remove any possibility of compression (take out the sparkplugs) you can quite easily spin it by hand (so long as it is in good condition) the most resistance you will feel is not due to friction but by the rotating mass.

I have seen rollerbearing cranks and engines before and the cost for the bearings because they either have to be assembled during the build (which is painstaking to do because they all have to be done simultaneously) or have to be designed in halves (to accomodate putting them in) all of which makes for an extremely costly build with minimal at best gains.

As a machinist i can tell you that on some things the old ways are the best ways. this has been thought of countless times by many people and yet in this day of age even a bugatti veyron with no price ceiling opted for a journal bearing.

I would start with trying different materials like i mentioned before, or trying helical oil grooves on the journals like ive done on a mkiii supra (it worked JUST AS WELL cant say it was better or worse but it did give a bigger contact patch from which to draw oil.)

[vex]

interesting. Thanks for the info!

I was coming to that conclusion and was wondering why people hadn't already done it. You answered that for me! I'm curious though if our engines are supposed to be balanced while rotating, wouldn't the mass become negligible at the bearings or is there too much torque being applied there from the combustion chamber of the opposite rotor?

[Cp1]

Originally Posted by vex

interesting. Thanks for the info!

I was coming to that conclusion and was wondering why people hadn't already done it. You answered that for me! I'm curious though if our engines are supposed to be balanced while rotating, wouldn't the mass become negligible at the bearings or is there too much torque being applied there from the combustion chamber of the opposite rotor?

yes the assembly as a whole is pretty well balanced but during ignition the force is pushing the rotor (or the conrod big end) directly into the bearing where it deforms slightly it is this force that a roller or ball bearings cant take over time and on a journal the oil cant be compressed enough to allow metal on metal contact. this force its akin to hitting it with a hammer to get it to spin. couple that with the increased wear from only having a very few points of contact on the bearing roller surfaces and you have extremely high pressure points. a ceramic ball riding in a steel v groove only has contact at two infinitely small points creating infinitely high pressure. so the ball or the groove must deform slightly to work.

Think of the forces acting on the bearings as engine knock. the rotating momentum is what saves the bearing like the engine from complete destruction as it transfers the force fairly quickly but it doesn't eliminate the shock or the "bang" altogether this force with each detonation will simply destroy an off the shelf roller bearing or any made for turbo ball bearing. and when coupled with the increased pressure it creates and the increased friction and design problems of assembling them into the motor it just isn't worth it.

[vex]

I see. I guess a little more thinking would need to be done on my part. I'm not too familiar with current technological trends when it comes to bearings.