This may be off the wall, but What's the efficiency difference between roller and floater bearings in an engine. Say you replaced the main bearings with rollers. What would it do for efficiency? What would be required for oiling? Would the forces exerted on the crank pound the roller bearings? Has this ever been done on a large engine? I know it's common on things like 2 cycles that are smaller.

 

This might be considered by some to be a LARGE Engine:

http://people.bath.ac.uk/ccsshb/12cyl/

It uses a Conventional Bearing Shell Design.

Some race engines have tried needle bearings on the large lift camshaft journals (1" total lift at the valve) with restricted oiling at the journal locations.

Hardest part of doing a needle bearing or roller bearing design for the crankshaft
main bearings is figuring out a way to assemble the bearings/ crankshaft in the engine. Typically the conventional crankshaft is supported by a layer of oil in the bearing shell so the actual losses are not very high.

http://en.wikipedia.org/wiki/Hydrodynamic_lubrication

"A large advantage of journal bearings is longer life than antifriction bearings (needle and ball). If the oil is kept clean, the journal bearing will operate for many miles/hours. The engines that currently use needle bearings generally are shorter life engines in order to gain high efficiency and power output. Journal bearings are also more forgivening of impulse loading than antifriction bearings."

That brings up another point. Conventional Bearing have the ability to "eat trash"
that will be inside any new engine no matter how well you try and clean them. The bearing material is soft enough that the particles are absorbed into the bearing. The foreign material might lightly scratch the crankshaft but typically the engine keeps running for many many miles. The needle bearings must be kept clean or they will score or wear rapidly.

Good topic for discussion though.

Tom Vaught

 

Vauxhall did a full roller bearing engine in 1917 Grand Prix engine, Kawasaki Z900 had roller rods, Okrasa had roller cranks for VWs so lots of engines have used them. Todays Formula 1 engines use plain journal bearings so thats something to think about efficiency wise. Floating bearings is a variation of the journal bearing, Ford used floating rod bearings on the early flathead V8s.

 

Quote:

"Floating bearings is a variation of the journal bearing"

Please explain further.

Tom Vaught

 

I think you know what he means. I hope so at least.

 

Tom, you're kidding, right? If Henry finds out about this, you could be visiting his office for some remedial reading. 59A rod bearings.

 

http://www.brighthub.com/engineering/mechanical/articles/12353.aspx

This is a Hydrodynamic Bearing:

Hydrodynamic Bearings are named so because of the lubricating principle involved in the bearings. Apart from the construction that acts as the bearing, the lubrication plays a very vital role in the construction to act as a bearing.
Before we proceed to look into what a hydrodynamic bearing is, let us know about Hydrodynamic lubrication.
Hydrodynamic Lubrication is formed basically due to the dynamic motion or action of the moving parts. When sufficient quantity of lubricant is present between two surfaces in which at least one surface tends to move, the relative velocity of the moving surfaces tends to pump the lubricant between the two surfaces separating the two surfaces by a dynamic film of the lubricant.
Typical Construction Features of a Hydrodynamic Bearing: Click here to see..
A typical hydrodynamic bearing consists of the following:
1. The rotating member - Shaft
2. The supporting bearing '“ Outer Sleeve
3. Lubricant
Working Principle of the Hydrodynamic Bearing:
1. Before the shaft starts to rotate, both the shaft and the outer sleeve are in contact due to the self weight as shown below in the figure. Click here to see..
2. As the shaft tends to rotate the lubricant in between the shaft and the sleeve tends to get squeezed and ultimately forms a boundary lubrication between the shaft and the sleeve but still a slight amount of metal to metal contact remains as shown in the figure.Click here to see..
3. As the shaft tends to rotate rapidly, the fluid lubricant is pumped by the shaft. The lubricant surface near to the shaft has a velocity which differs from the surface velocity of the oil surface near the sleeve. This causes a pumping action in the lubricant. The pumped lubricant ensures that the shaft and the sleeve remain out of contact. This phenomenon of the lubricant pumping itself to keeps two mating surfaces out of contact is termed as 'Hydrodynamic Lubrication' and hence the name 'Hydrodynamic Bearing'. See Figure below.Click here to see..
This principle ensures that the shaft remains out of contact when required i.e. during running. But a problem exists in this, the oil in between the sleeve and shaft tends to flow towards you or away from you when you look at. Hence a copious-continuous flow of the lubrication has to be ensured for the bearing to work perfectly compensating the lubricant loss.
Applications of Hydrodynamic Bearings:
Though all of us may not have seen the hydrodynamic bearing, they tend to work in some of the harsh and well know environments to us.
'¢ The crankshaft and camshaft bearings in an automobile engine is a very good example for Hydrodynamic bearing
'¢ All hand operated lube oil pumps do posses hydrodynamic bearings.
Design and Selection Aspects:
This is a type of bearing where all parameters are to be selected by the designer for designing the bearing. This is more of a bearing made for a application rather than the one which is taken from off the shelf.
'¢ An important note for the design of hydrodynamic bearings, the hydrodynamic bearings are good in handling radial loads but will not be able to carry any axial load. Hence necessary precaution is to be taken during design of hydrodynamic bearings for accommodating the axial loads generated.

This is a floating bearing:

http://www.ferret.com.au/c/Treotham/Floating-bearings-for-better-accuracy-n682502

A NEW generation of DryLin floating bearings made by igus, represented by Treotham Trading , is designed for use in parallel shaft/rail linear systems to simplify the design and manufacture of machines.

A unique sliding bearing compensates for misalignment between two shafts by as much as six millimetres, and due to a swivelling suspension device, the bearing can operate virtually independently of an uneven or unfinished surface.
The possibility to perform service life calculations, a practice traditionally restricted to jobs using ball bearings, provides the designer with an assurance that the application will work satisfactorily.

A swivelling suspension device of the actual bearing allows angular movements of ±2º. However, the main feature of the bearing is the lateral compensating movement perpendicular to the shaft.


http://www.freepatentsonline.com/WO2008011400.html

FLOATING BEARING CARTRIDGE FOR A TURBOCHARGER SHAFT

A bearing system for use in high speed rotating machinery, such as a turbocharger (14), wherein a shaft (12) is rotatably supported by a floating bearing cartridge ( 10) having axially spaced angular contact bearings (16, 18) each with a set of bearing balls (30) supported between inner and outer races (32, 34). The bearing cartridge includes an inner spacer sleeve (42) for axially spacing the inner bearing races, and a rotationally floating outer sleeve (46) having a pair of radially inwardly open grooves (52) for removably receiving snap-type retaining rings (54) which engage and axially space the outer bearing races. The axial dimension of the inner spacer sleeve is elongated slightly relative to an axial dimension defined between outboard faces of the installed retaining rings, thereby slightly unloading the sets of bearing balls from their respective outer bearing races. Such slight axial unloading enhances smooth- running operation with minimal bearing wear, while accommodating transient loads during operation.


http://www.wipo.int/pctdb/en/wo.jsp?wo=2002012741

The invention relates to a floating bearing for a slide (9) that is steered by two shafts (4). Said floating bearing comprises a linear bearing (3), which is directed along one of the shafts (4) and a bearing housing (2), which accommodates the linear bearing and is connected to the slide (9) by a connection device (1). The aims of the invention are to ensure a long service life of the bearing, to guide the slide with precision parallel to the plane defined by the two shafts and to permit relatively low assembly costs. To achieve these, the connection device (1) is configured in such a way that the bearing housing (2) is located so that it can be displaced transversally to the longitudinal direction of the shaft concerned (4) and parallel to the shaft plane (7) defined by the axes (5, 6) of the two shafts (4).

Tom Vaught

 

O'¦K'¦. So it's not 59A rod bearings'¦..Sorry'¦'¦I was just trying to play it up that Henry was doing it 70 years ago. I remember the first time I took one of those apart. I was about 11 or 12 and I thought something was wrong. My father thought it was funny I was so worried that the bearings spun and I couldn't figure out how they healed themselves up.