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Inverted LS2

F

fmarino1976

Well Known Member
I was looking at the GM performance catalog, and some tuned LS2 engines produce about 230 HP at 3000 RPM. This could be enough for a direct drive but the crankshaft location would be a problem. If one could install it upside down on a -10, what would be required to make a compatible lubrication system? Any other considerations?
 
You'd need a multi stage dry sump system to scavenge the oil from the valve covers and other areas. Most compatible props are not rated at 3000 unfortunately. Cool idea, maybe 4 psi of boost would give you 270 hp at 2700 rpm?

Probably should have a good bearing setup to take prop loads and supply oil for the prop unless you go electric.
 
The engine will wear down quickly because the crankshaft isn't designed to bear the thrust loads from the propeller and then you still have all the headache associated with inverting the engine which isn't a trivial matter...

Using a PSRU with offset and a slightly smaller engine might be a better idea.
 
Inverted engine

Many WWII aircraft used inverted V engines. You could get a smaller diameter three or four-blade prop which would easily convert the power to thrust very efficiently, even mounted normally. A 68" diameter prop would have a tip speed of M0.85 at 3000rpm and 200 mph TAS. A 56" three-blade could still produce the same static thrust as a 68" two blade, or the same with a 48" four blade, but these would have much lower tip speed and noise.
 
LPE was developing some inverted V8s based on the SBC 10 or 15 years ago, not sure if they are still around.

Most auto engines are dogs direct drive for their weight unless you go on a massive weight reduction program. Turbos or gearboxes help make things right with some added weight. The only direct drive V8 which has really impressed me is Gary Spencer's Ford small block Long Eze. He regularly trounces a number of traditional guys in races with the same size engines.

The stock LS2 only develops about 200 hp at 3000 rpm and about 175 at 2700. You need more cubes, some boost or more rpms to make it viable for an RV10. Not a fan of radical changes within an engine for aircraft use unless they have been very well proven in some other applications like off shore racing.

Some of the modern large V6s from Chev, Ford, Hyundai and Honda are around 300hp stock and would be considerably lighter than a LSX but you'd need a gearbox of course.
 
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Horsepower is one thing.........

But what you really need is torque and with direct drive, I don't think that you will get enough to swing the prop.
 
Skybolt Al said:
But what you really need is torque and with direct drive, I don't think that you will get enough to swing the prop.
Click to expand...

A 6L V8 producing 200 hp at 2700 rpm results in exactly the same torque as a 200hp Lycoming delivers at 2700 rpm. HP X 5252/ rpm= torque. (389 lb./ft. in this case) Please, let's not belabor this one any more! :eek:
 
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kristoffon said:
The engine will wear down quickly because the crankshaft isn't designed to bear the thrust loads from the propeller and then you still have all the headache associated with inverting the engine which isn't a trivial matter...

Using a PSRU with offset and a slightly smaller engine might be a better idea.
Click to expand...

I would hope somebody would not just bolt to the crank without some form of thrust bearings and flex plate.
 
Actually most cranks can easily handle the thrust as many clutch release mechanisms apply considerable force. Of more concern are the bending loads imposed by the prop as the aircraft changes direction. The prop is like a giant gyroscope and likes to remain as is while the forces concentrate at the end of the crank (more accurately behind the last crank throw).

These facts have been driven home in the last few years on Corvair DD installations after multiple crank failures. The fix is the famous "5th bearing" setup bolted to the end of the case. There are many DD engines flying with a lot of hours on them and no changes to the thrust bearings inside the engine and even a few flying with lightweight propellers and no radial support bearings but it is a scary thought as no testing has been done to validate the concept.

Fingers crossed is not the best method to approach these sorts of things in aviation so an engineered piece to take prop loads would certainly be a good idea.

Other mods to invert the engine would be to the crankcase breathing system and cooling system.
 
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Ross,
One issue that never seems to be addressed in alternate engines, whether direct drive or geared, is a torsional vibration analysis and/or test of the engine/prop system. Of course it is done on certified engines/propeller combinations as part of the certification process. And if you read the history of the Allison V-1750, the Rolls-Royce Merlin and Pratt and Whitney R-2800 there were lots of failures that were caused by torsional vibrations which resulted in component redesign before the engine was fit for service.
When I worked in the marine propulsion business, it was done as a matter of course, and I am puzzled at the lack of knowledge of this in the experimental aircraft community.
What is your view of the necessity of performing a torsional vibration analysis/test?
Terry
 
rv6ejguy said:
A 6L V8 producing 200 hp at 2700 rpm results in exactly the same torque as a 200hp Lycoming delivers at 2700 rpm. HP X 5252/ rpm= torque. (389 lb./ft. in this case) Please, let's not belabor this one any more! :eek:
Click to expand...

They just never or will not learn, do they Ross?
 
terrye said:
Ross,
One issue that never seems to be addressed in alternate engines, whether direct drive or geared, is a torsional vibration analysis and/or test of the engine/prop system. Of course it is done on certified engines/propeller combinations as part of the certification process. And if you read the history of the Allison V-1750, the Rolls-Royce Merlin and Pratt and Whitney R-2800 there were lots of failures that were caused by torsional vibrations which resulted in component redesign before the engine was fit for service.
When I worked in the marine propulsion business, it was done as a matter of course, and I am puzzled at the lack of knowledge of this in the experimental aircraft community.
What is your view of the necessity of performing a torsional vibration analysis/test?
Terry
Click to expand...

Absolutely agree. I mentioned validation loosely before (and the crossed fingers part) meaning that a full engineering analysis should be done including TV studies. Dan Horton here on VAF should be credited with opening people's minds on TV and you'll find a lot of discussion if you search here on TV from the last 2 years or so. Dan asked the hard questions of some vendors of gearboxes, sometimes with embarrassing results for the vendors.

Most of the new gearboxes developed in the last 2 years incorporate absorber couplings now and a number have undergone TV testing or at least run some math on the matter. Previously, only a handful of drives had much science behind them.

Direct drive setups still invariably have no TV studies done, people thinking without a gearbox, they will somehow be immune.

Dan was getting along with some math models to hopefully predict high amplitude rpm zones but needed some more practical data to validate the accuracy of the models. Not sure where that got to? Dan?

Ignorance is bliss as they say- until the crank snaps.:eek:
 
Power Sport PSRU

rv6ejguy said:
Absolutely agree. I mentioned validation loosely before (and the crossed fingers part) meaning that a full engineering analysis should be done including TV studies. Dan Horton here on VAF should be credited with opening people's minds on TV and you'll find a lot of discussion if you search here on TV from the last 2 years or so. Dan asked the hard questions of some vendors of gearboxes, sometimes with embarrassing results for the vendors.

Most of the new gearboxes developed in the last 2 years incorporate absorber couplings now and a number have undergone TV testing or at least run some math on the matter. Previously, only a handful of drives had much science behind them.

Direct drive setups still invariably have no TV studies done, people thinking without a gearbox, they will somehow be immune.

Dan was getting along with some math models to hopefully predict high amplitude rpm zones but needed some more practical data to validate the accuracy of the models. Not sure where that got to? Dan?

Ignorance is bliss as they say- until the crank snaps.:eek:
Click to expand...

Ross,
This is an area were plenty of otherwise good engineers fail to understand the forces involved. On the PowerSport internal ring gear PSRU, (similar to the Marcotte you use in most respects), there were a whole series of TV tests done. It was interesting that the system WAS stiff enough for the 2 rotor 13B rotary. The 20B three rotor with it's longer e-shaft (read crank) did require a second order damper. Thankfully it is much smaller than the one for first order problems!
Bill Jepson
 
Rotary10-RV said:
Ross,
This is an area were plenty of otherwise good engineers fail to understand the forces involved. On the PowerSport internal ring gear PSRU, (similar to the Marcotte you use in most respects), there were a whole series of TV tests done. It was interesting that the system WAS stiff enough for the 2 rotor 13B rotary. The 20B three rotor with it's longer e-shaft (read crank) did require a second order damper. Thankfully it is much smaller than the one for first order problems!
Bill Jepson
Click to expand...

Yes, I still have the articles on the PowerSport drive and the TV testing done. To my knowledge EPI, RWS, PowerSport, Autoflight, GAP, MPS and the soon to be RDM have considered TV in their design and used various methods to combat it. Most have a Lord or Lovejoy coupler/ absorber or use another means such as a quill shaft or calculated backlash to minimize TV amplitude within the operational rpm range. Details on what many companies do in this regard are either sketchy or simply not released.

Getting back to DD auto engines, I can't recall a single case where anyone ever instrumented one for TV with a prop installed.
 
hmm...

The main reason I was thinking about DD was for weight savings, but after adding an oil scavenging system, maybe a thrust bearing and shaft/coupler capable of handling the thrust and TV forces, and maybe adding a supercharger or turbocharger to increase the HP in the 2700 RPM range, maybe there is not much weight to be saved compared to an upright V8 with a gearbox...
In any case, thank you for the education.
 
Stupid Question

Just a "lurker" here on alternate engines. Personally, I will stick to Lyclones, but I still am interested enough to read the discussion. And I do get the relationship between hp and torque. :p

It seems to me that the engines are not the problem, but the coupling of the engine to the prop that is the problem. The WWII radial engine nose cases transferred literally a couple of thousand horsepower to the props, and at the same time absorbed the thrust loads, with relatively small gears, usually in a planetary arrangement.

My stupid question is: Why is it so hard to design/build a gear reduction system for a 300 hp engine?:confused:

Maybe this should be another thread??
 
I think the chevy gearboxes have had pretty good success rates in the past few years. I don't know of any failuresrecently but Ross may know of some. It's just the added weight that people are trying to get rid of.
 
Gear Reduction System for 300 hp Engine

PCHunt said:
My stupid question is: Why is it so hard to design/build a gear reduction system for a 300 hp engine?
Click to expand...

It's not that hard in as much as the design principles of sizing the gears, shafts and bearings are well known. The loads can be calculated, including the thrust and gyroscopic loads of the propeller. Analysis should include finite element analysis of the gear case and a torsional vibration analysis. Then you build a prototype(s) and instrument and ground test it. You analyse the results of the test and redesign the components if required. Build another prototype(s) and make sure the redesign has the results you expect. Then you flight test it for hundreds of hours to ensure its reliability. Now most of this stuff is done on new designs of industrial gearboxes, but the difference with aircraft gearboxes is that they must be reliable with minimum weight. So every component is critical and the design stresses are generally higher than an industrial gearbox.

Now you are into it for a bunch of money and you are ready to bring it to market. From your potential customers you will probably hear:
-It costs HOW MUCH?
-I'm not an engineer, but I think I'll make my own toothed belt drive
-You're rating it for 300 hp, I guess that means it will take 500 hp if I supercharge the engine.
-Why did you pick engine X? I'd rather have engine Y.

So I think the real answer to your question is that the market for an aircraft gearbox is very small and will not bear the design, development and test costs.
 
It's difficult to design a production gearbox for Do It Your Self type persons who pick their own engines, props, mounts, airframes etc.
I'm not saying it can't be done, but the variables make it a thought provoking process.
I chose Tracy's planetary drive because it has a good track record and support with Mazda 13B engines, which I use. Time in service is also a legitimate way to verify a gear's reliability. ;) In fact, it is the only real way.
I see from his site that a few other engine types are mounting his gear. I would consider this a new application, and failures here would not reflect on the gear as applied to a 13B per se.
Now accelerometers are cheap and we all have lap top computers, so is there a program application that we can use while testing (including flying) to put this issue to bed???:confused:
 
Software for measuring Vibration

Here is the first thing that came up on Google for measuring via a laptop:
http://www.justmeasure.net/
Now I've seen pro consultants use accelerometers and laptops to detect bearing and gear faults at work. They have shown me the data, and I've used that to make maintenance decisions, but that's all.
I'm wondering what data you have to input (like the mass of the relevant parts, number of gear teeth and number of bearing rollers on each component in question? Or do you derive that from the data?
Constructive comments?
 
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