OT - Combustion Pressure in Modern Gas Engine?

[wheels17]

Can't speak to current engines, but Mercury outboard engines used needle roller bearings on wrist pins and big ends on the con rods, and ball bearings on their crankshafts at least into the 80s. Left the business back then. Still a lot of old Mercs running out there. Try this for 50 year old motors. Hmm. No sleeve bearing Johnson/Evinrudes there that I see...

https://www.youtube.com/watch?v=Lv1weHS8Dqw&feature=player_detailpage#t=95

 

[kustomizingkid]

Plain bearings are cheap, and they work.

 

[steve-l]

Tonytn36,
Actually, you're not even close with your guess. Cylinder pressures in a stage turbo charged diesel can reach in excess of 10,000 PSI peak pressures. I develop engines as a hobby and have been doing this for many years. I was involved in the design of a diesel replacement for the Lycoming flat six small aircraft engine about 12 years ago, as the availability of aviation high octane gasoline was becoming scarce, because of environmental rules (lead content). The idea being to design an engine with the same weight, size and power of the flat six and use jet A fuel. This meant 250 HP, under 250 Kg at 2500 RPM, which was a daunting task. The basic engine design was an inverted V4, stage supercharged, two stroke diesel. The team encountered 20 metric tons of ignition pressure, which caused a complete redesign of the cylinder head and block to prevent bending moments.

Vancbiker,
Rolling element bearings are used in your reference engines because of the limited lubrication available, not because rolling element bearings offer less friction than hydrodynamic bearings. In fact several attempts by several engineering groups to replace the oil bearing with rolling element ones have definitively proved that there is no advantage in reducing friction. I believe the last attempt was made by Honda during their development of their F1 engines between 2000 and 2004. That's not to say that this technology is not in use today in four stroke designs, it is, specifically by Kawasaki in their liter motorcycle I4 engines. Even in that case, when using the engine for racing, it is common practice to weld the crankshaft throws after assembly to prevent dynamic re-indexing under load, which as you can imagine, can be very exciting when it happens between your legs at 10,000+ RPM.

 

[jim rozen]

"The basic engine design was an inverted V4, stage supercharged, two stroke diesel."

Wasn't there a german aircraft engine just about that description around WW2?

As for smart cars being safer than motorbikes, can't say - but I love being behind one
when I'm riding a motobike as I can see right over the top of those things.

$300 key? That's about what one costs for a corolla these days. I've said it before
and I'll say it again: cars should not have software.

 

[Vancbiker]

Vancbiker,
Rolling element bearings are used in your reference engines because of the limited lubrication available, not because rolling element bearings offer less friction than hydrodynamic bearings. In fact several attempts by several engineering groups to replace the oil bearing with rolling element ones have definitively proved that there is no advantage in reducing friction. I believe the last attempt was made by Honda during their development of their F1 engines between 2000 and 2004. That's not to say that this technology is not in use today in four stroke designs, it is, specifically by Kawasaki in their liter motorcycle I4 engines. Even in that case, when using the engine for racing, it is common practice to weld the crankshaft throws after assembly to prevent dynamic re-indexing under load, which as you can imagine, can be very exciting when it happens between your legs at 10,000+ RPM.

I absolutely know and understand that. My post was intended to counter the post stating that rolling element bearings could not sustain the high speeds and pressure peaks that occur in an IC engine.

 

[Ron B.]

I have worked on Buggatti type 35 engines ,even one last year. it is correct,the engines were developing big HP in 1928 but oil additive technology wasn't at point where it could maintain the film thickness required in the bearings so rollers were used. Over the decades lot of type 35's were either parked up or repowered because of the work require to repair the bearings which would brinell ,often without warning before throwing a rod through the side of the engine.

 

[Fulmen]

This meant 250 HP, under 250 Kg at 2500 RPM, which was a daunting task. The basic engine design was an inverted V4, stage supercharged, two stroke diesel.

Oh mama. I love the idea of small 2stroke diesels, with current level of turbo and compressor technology, this sound like a interesting approach to combustion engines.

 

[Mark Rand]

One wonders what the problem is with using a non-inverted V4 at higher speed to get the power and a geared reduction drive to the propellor. It worked for 150,000 Merlins.

 

[Tonytn36]

Tonytn36,
Actually, you're not even close with your guess. Cylinder pressures in a stage turbo charged diesel can reach in excess of 10,000 PSI peak pressures.

Steve, I didn't say that was max pressure. I said at 225 bar, you are in steel piston territory (low end, also depends on temps, but still....). I also have a significant amount of experience in this field.

 

[steve-l]

One wonders what the problem is with using a non-inverted V4 at higher speed to get the power and a geared reduction drive to the propellor. It worked for 150,000 Merlins.

Mark,
The reason for the inverted V4 was to not obstruct the forward view of the pilot. The power at 2500 RPM was to enable direct drive of the propeller. At the time Renault was also trying to develop an aircraft diesel, but were destroying gearboxes with torsional vibrations.

 

[CalG]

Yup that IS an Audi, seriously over-engineered with little common sense. Vehicles have done similar for 20+ years, but most trigger it via the door switch as they should. If I need to pull my keys so the kid at the gas pump can get the locking cap off, she needs my keys to run back into the house for the 3rd time after Im in the truck, or one of 50 other reasons, I can sit comfortably with the a/c or heat blowing residuals and listen to the radio.

Audi fuel filler doors unlock with the same controls as the rest of the doors etc. No need to pull the key, And the filler door locks again when you lock the doors whether from inside the vehicle, by remote, or a twist of the key in any lock tumbler as you depart.

But you do need to be smart enough to own an Audi, or the dealer will own you. ;-)

 

[pistonskirt]

That's not to say that this technology is not in use today in four stroke designs, it is, specifically by Kawasaki in their liter motorcycle I4 engines. Even in that case, when using the engine for racing, it is common practice to weld the crankshaft throws after assembly to prevent dynamic re-indexing under load.

There is a current in line 4 Kawasaki engine with rolling element crankshaft bearings ? .........surely not since the 1980's Z1100 engines.

regards

Brian

 

[kustomizingkid]

I haven't seen any modern 600 or 1000 sport bike engines with any roller bearings. Plains on the crank and either plain or just bored al on the rods. Always bored al for the cams with no bearing.

I would have loved to see some cylinder pressure from the 400hp 1.8t golf I helped build. At 28 psi it was a lot of fun and was a decent sleeper.

 

[Mark Rand]

A fact that isn't widely appreciated is that a journal bearing has zero load bearing capacity at half the rotational speed. Oddly enough, the major harmonic of the load of a four stroke big end bearing is at half the rotational speed!

Thanks to Professor Harry Marsh of Durham University's, GEC sponsored, short tribology course for that one.

 

[matt_isserstedt]

Pretty much every gasoline two-stroke engine I've ever seen uses rolling element bearings. Most of them rev higher than a four-stroke of similar displacement. Most of them have higher output than a four-stroke of similar displacement. Properly cared for they seem to last just fine.

.

I'll argue that the peak pressure on a 2 stroke isn't as high as a 4 stroke. Scavenge cylinder filling is kinda iffy. The specific output is just due to a larger number of combustion events per rev. I've never been inside a Yahama 2 stroke outboard marine engine...do those use roller bearings?

To your point, though, there are some other factors involved.

 

[Vancbiker]

I'll argue that the peak pressure on a 2 stroke isn't as high as a 4 stroke. Scavenge cylinder filling is kinda iffy.

I don't have numbers for pressure, but at the peak of development of 2 stroke GP motorcycles, the 500cc 4 cylinder bikes were producing over 200hp. For a 31 cu. in. displacement engine to make better than 6.5hp per cu. in., it has to be doing a fine job of filling the cylinders. I'll grant you that crank and rod bearing longevity beyond a few hundred miles is not a design criteria in that application. On a more pedestrian note, Stihl chainsaw with produces more than 2hp per cu.in. Only a few production 4 strokes do that without resorting to forced induction.

I've never been inside a Yahama 2 stroke outboard marine engine...do those use roller bearings?

As far as 2 stroke outboard boat motors I've dealt with Mercury and Suzuki. Both used ball bearings on the crank mains, cylindrical roller bearings on the big end of the rods, and caged needle bearings on the small end of the rods.

 

[stephen thomas]

A fact that isn't widely appreciated is that a journal bearing has zero load bearing capacity at half the rotational speed. Oddly enough, the major harmonic of the load of a four stroke big end bearing is at half the rotational speed!

Thanks to Professor Harry Marsh of Durham University's, GEC sponsored, short tribology course for that one.

Mark I'm missing something here, how does one determine full rotational speed to derive the 1/2 point?

smt

 

[Mark Rand]

Not half rotational speed as in 5000rpm vs 10000rpm. Half rotational speed as in every other revolution. Like the combustion strokes in a four cycle engine or the nasty phenomenon of half-speed whirl

 

[CalG]

Not half rotational speed as in 5000rpm vs 10000rpm. Half rotational speed as in every other revolution. Like the combustion strokes in a four cycle engine or the nasty phenomenon of half-speed whirl

One half rotational frequency then, Speed is a vector.----------------->.;-)

 

[magneticanomaly]

Tonytn36 still comes closest to actually answering the OP's question.

Re: rolling vs plain engine bearings, Wisconsin engines for many years used Timken-type tapered roller bearings for mains, one at each end for one, two, or V-4 cylinder engines. The V465d added a center plain main, which in my experience failed to hold up. The tapered roller bearings never needed replacement unless they got rusty.
IHC built tractors in the 1920's and 1930s with I-four-cylinder engines, with only two mains, one ball bearing at each end of the crank, and I have one and use it, and have never heard of a main bearing failure on one of that design. But neither the Wisconsins nor the tractors were designed for cheapness, high-speed, or high horsepower per unit weight or displacement.