enginehistory.org

[gryan]

Is anyone building large piston engines for aircraft these days? The large piston engine still has a good niche if exploited correctly. I've read of Zoche aero-diesels, the Deltahawk and the like and they are interesting, if a little on the small side.

The Orenda V-8 from Canada seemed to be progressing but lately nothing more seems to be occurring there. It evolved from the Big Block Chev. Someone else did an aero engine based on the Chrysler hemi 426 in the 1970s but that seems to have stopped. And what about the Light Power Engines from Darius Zehrbach?

LPE had a 600cid inverted V-8 and a 1005 cid V-12. This may have been displayed at Oshkosh. I was told the LPE engines were based on some NASA designs. First I'd heard about that. Does anyone know the story behind the development of these engines?

What has happened since? I heard LPE got done-in over a court action or some such.

[jjuutinen]

While I don´t have answers to the question as such, I do have an idea. My ideal engine for e.g. 500-600 hp range would have following characteristics:
*V-10 four stroke diesel
*sleeve valves
*relatively low rpm
*small bore/long stroke
*common rail fuel system (it´s a lot simpler than the individual pump element system)
*turbocharged+intercooled with variable geometry turbine
*pressurized water cooling
*wet cylinder liners
*single lever operation
*weight in running condition (without coolers) should not exceed 0.5 kg/hp

Cruising SFC should not exceed 145 g/hp/hr and max power SFC 155 g/hp/hr. Achieving these figures should not be a problem as they are achieved by best truck diesls today with less sophisticated systems.

[gryan]

Yes. That would be a nice engine, but why only 10 cylinders?

[jjuutinen]

!0 cyls felt a good compromise, but why not 12, if feasible. As an aside, anyone else wondered how "modern" (quotations for obvious reasons reagrding any modernity in Lycoming or Conti flats) GA engines have fewer cyls that old ones in the same power range? E.g. about 250 hp is now covered with 4 cyl variant whereas in the 1930s 7 cylinder radials and V-8s (Argus engine used in Fieseler Storch) were common for the same power range. Another slightly off topic observation is how most WW Two fighters would be classified as STOL aircraft today. I was reading a newish edition of the Jane´s AWA, and I noted how an aircraft having a ground roll of 250 yds is described as "super STOL". Yet e.g. the Stinson Vigilant apparently took off with 50 yd ground roll and stalled at 28 mph IAS!!! What is even more, I have calculated mileages of many smaller GA aircraft and it seems that most current certified small GA aircraft have poorer mileages that older designs from the 1930s at comparable speeds. But, if you just look at the older craft, there were airplanes. These current ones are rectangular boxes thrown together. To put things into perspective, many GA aircraft have higher stalling speeds than slick design like the Spitfire despite considerably lower wing loading. This speaks volumes about their (lack of) design.

[gryan]

A V-10 can't be completely balanced. There are residual unbalances. You could put some balance shafts in there (need two rotating at twice engine speed) but if you are going to the complexity of adding all those parts why not just add two cylinders and have a V-12?

A V-12 has perfect balance up to the 6th harmonic and you can have any included angle between the cylinder banks and still have perfect balance (there have been 90 degree V-12 engines). To get even firing impulses you need to have the included angle between the cylinder banks at 60 degrees or some multiple thereof. Hard to better that!

There is the matter of dealing with torsionals, but that is manageable with good design.

As for GA engines and aircraft design:-

In the case of engines they use what is cheapest. More cylinders equals more components, more machining operations, more assembly operations etc. The GA engine market is relatively small and getting certification is expensive (as are insurances). Most of the cash goes elsewhere than engine design.

As far as GA aircraft are concerned, to most people they look primitive and unexciting. Many of them don't perform well. A care of looks wrong, is wrong perhaps? Put it this way, any UJM (Universal Japanese Motorcycle) or GT car excites more passion in the population than most of the GA stuff. Those are designs that look better. They are cohesive and they look like they will perform (which in general they do). 1930s and WW2 aircraft are designs that look right (and were) as well. I'm not surprised that people remain interested in them.

Perhaps it all comes down to the old adage that what looks right is...

[wallan]

The V-10 only makes sense in a very limited application.
The reason that F1 cars went to V-10 engines of 3 litres is due to the fact that the swept volume for each cylinder is nearer to the ideal than the V-8 or V-12. It used to be that for a high-speed 4-stroke engine the ideal size for each cylinder was around a third of a litre. (something sticks in my mind to say that at around 12,000 rpm, it is 325cc) As speeds increase this reduces to nearer three-tenths of a litre. For 3 litres, a V-8 cylinder would be 375cc, and a V-12 would be 250cc, so the V-10 made better sense. Now, to slow the cars down, but to allow them to use previous parts in the new engines, they are V-8s of 2.4 litres. This also has other benefits to the sport. The V-8 angle will be 90 degrees, making the engine wider causing greater drag, or reducing downforce. I, also, think that as most teams won't use a flat crank in their V-8, they can’t use the ideal exhaust harmonics on separate banks, perhaps leading to the return of the ‘bunch of bananas’ type exhaust systems, which will also cause more drag.
Personally, for aviation engines, I think the ideal would be a box or deltic style, overblown CI, (Diesel) with supercharger, turbocharger, sleeve valves or piston ports, with selective injection to allow 2-stroke operation for high-power, and 4-stroke for cruise and economy. (yes, and intercoolers, which would also double as the source of energy for heating and cooling for the cockpit)

[kmccutcheon]

Henry Ford filed for a patent on an aircraft V-10 back in 1943. Please see US 2,434,038.
_________________
Kimble D. McCutcheon

[jjuutinen]

Wallan, do you mean H engine with that box form? E.g. 16-cylinder H form engine would make a nice and compact engine, though not too simple:)

[wallan]

No, I mean the opposed piston CI engines, similar to the Junkers ones, but with 3 or 4 crankshafts, forming a triangle or square.

[gryan]

Wallan

My understanding is that a flat crank V-8 of 2.4 litres rotating at 18,000 to 19,000 rpm produces (or rather transmits to surrounding structures) 30% greater vibration than the old 3 litre Cosworth flat crank V-8 at 10,000 to 11,000rpm. And that higher vibration (oscillating force) is at a far higher frequency. The flat crank V-8 has a nasty unbalance which is delivered at twice engine rpm.

If the F1 teams use flat crank V-8s they will encounter some really destructive forces. I recall the Cosworth V-8 was famous for wrecking its own cam gear early in development. This took a lot of effort to resolve. It also used to consume oil pumps, brackets, chassis parts, drivers (eyes and kidneys) and anything else that was excited and resonanated! The DFL at 3.9 litres even destroyed its own harmonic dampers.

These engines demanded careful design of all surrounding components. Many parts (car as well as engine) were short lifed.

The two plane crank gets around this issue and can be completely balanced. As you indicate, the cost is uneven firing impulses along each cylinder bank leading to poor exhaust system harmonics. This would force a centre or valley exhaust system design so that evenely spaced exhaust harmonics could again be exploited. The Ford Indy engine was a design which did that. It would be good to see this layout revived again. The only design issue outstanding would be the torsionals of a two plane V-8 at super high rpm. Interesting to see whether that would be a problem.

BTW, whey were the V-12s of the 60s valley exhaust designs? There was no need to do that from the standpoint of exhaust harmonics of a V-12.

If the centre exhaust V-8 were revived in F-1 I wonder how long it would be before a road car GT would feature a similar engine; up front!

Packaging of this type of V-8 could be aerodynamically advantageous in F-1. You could remove the airbox from behind the driver's head to gain better air flow to the rear wing. The loss of exhaust manifolds outboard would tidy up the rear sidepod area (which is very tight currently) allowing for better radiator exit flow. Now you can have a smaller radiator. The induction would be housed in the forward sidepod area (high pressure area). This all results in smaller sidepods, smaller radiators and less drag.

Trouble is, once the V-8 architecture and installation is definatively decided, that's the end of any innovation in F-1 for the forseeable future.

You mentioned that there was an ideal cylinder size. From your comment it appears this size is related to engine rpm. How is this derived? Is there a formula, rule of thumb or mathematical relationship?

Thanks for an interesting post.


Gerald

[jjuutinen]

[gryan]

Here is a new piston engine for aircraft. It's only 444 cid but it does have twelve cylinders!

http://www.nagelengine.com/home.html

[jjuutinen]

I don´t like that engine: it has too high rpm, only 2 valves/clylinder, low boost, side by side conrods (I accept only fork and blade)! If they want opposed cyl engines, why don´t they copy Fedden´s sleeve valve boxers?

[szielinski]

It does seem somewhat low-tech and barely one dick of boost. Nevertheless, it is no mean feat to make ANY engine from scratch.

[gryan]

re RPM

How high is too high? Surely it is a matter of piston speed as opposed to rpm? ie if the stroke is short enough you can run high rpm reliably.

re Conrods

What is the objection to side by side rods?