Electrical failures

[facthunter]

Air cooled Mob is not nice. I don't recall seeing  too many flat four engines running unmuffled and with the carb underneath the muffler has only one place to go. Radials and Dehavilland inverted motors are often stubs or unmuffled  but you should  have to PAY for the sound of a radial motor It's that good..  Nev

[Area-51]

Longevity is not the driving factor in automotive where new materials and production methods are concerned; Price/Cost is and longevity is Cost driven to the point of the component lasting the period applied to Factory Warranty, which is covered, like insurance, within the Wholesale Price.

 

Material's Technology is also driven by End User Expectation... 600bhp from a factory 5.0 Coyote V8 is a User Driven result... 35mpg is a User Driven result... Powdered high pressure electrocast conrods are Cost Driven result...

 

A 1930's Royce or Bugatti motor, with all its ancient material's technology will still crap all over a modern engine in performance. The only modern components that can offer any real level of an uncompromised challenge here are computer generated stress optimised 3D printed alloy components. Everything else is old and already long done...

 

 

[facthunter]

Those Bugatti motors were CRAP. I've worked on them and they couldn't even cast a proper cored block and head combined. They use a screwed on steel plate all over the side. Their aero engines were useless and unreliable.  Bentleys had a bit of a reputation as some were supercharged but NONE of the put out high power anything like we see today. Nev

[Ian]

1 hour ago, Area-51 said:

A 1930's Royce or Bugatti motor, with all its ancient material's technology will still crap all over a modern engine in performance. The only modern components that can offer any real level of an uncompromised challenge here are computer generated stress optimised 3D printed alloy components. Everything else is old and already long done...

I'd be inclined to disagree with this statement. Most engines of this period were massively under-square with long strokes which generally isn't as efficient as modern oversquare designs.

Piston engines underwent rapid development in WW2 as well as the understanding of alloys and tribology. The tolerances used in the manufacture of modern engines is significantly better than that used in the 1950. This is obvious when you consider oil consumption, old engine designs chew through oil, modern designs do not.

Inspection methods such as xray etc. provided the ability to virtually eliminate flaws in castings and forgings which were a significant source of failure in old engines.

Because quality controls are higher there is no longer a requirement to overbuild so in many cases a modern engine is significantly flimsier than an equivalent 1930s engine however they will generally run longer.

Engine castings are generally more complex as techniques such as lost foam casting techniques were developed in the 1950s allowing more intricate water galleries and reduced machining. This has allowed effective temperature control at significantly higher power levels.

Sir Harry Ricardo was heavily involved in engine design over this period and was the reason why a significant number of engines during this period used sleeve valves. His research indicated that power outputs beyond 1500HP wouldn't be possible with traditional valved engines. However higher octane fuels and sodium filled valves allowed traditional designs to go significantly above this. He also did research on fuel octane and the octane improving qualities of water injection. 

 

That being said my favourite engine design is the Napier Deltic https://en.wikipedia.org/wiki/Napier_Deltic which evolved from the Junkers Jumo 204 aircraft diesel engine.

The part of the design story that I like is that a senior draftsman suggested that one of the crankshafts needed to rotate in the other direction to make the piston phasing work.

 

 

 

[facthunter]

Napier produced some of the best built stuff  of the period including AERO engines.   Some of the Ricardo "features"  which had copious patents was a bit questionable when subsequent work by people like Cosworth produced much more power from smaller capacity  multi valved engines and the Poppet valves went on from  there to remain pretty much universal. with gas flow figures far better than sleeve valves . The PLUG heads were always hard to cool and the little articulating rods working the sleeve valves  gave trouble in COLD places moving the large area sleeve valves with stiff oil. Rotary valves came and went too but hung around for a while in some 2 strokes induction till reed valves replaced them..  Nev

[kgwilson]

6 hours ago, skippydiesel said:

Comment on your  facts: 

"Air cooled engines usually have the exhaust system include...."

How can this be ? Air cooled engines usually have their exhaust systems made for the particular application - ie the weight of the installed engine will differ depending on the aircraft its fitted to.

 

"The Rotax 912 ULS is quoted at 56.6 KG.  But you have to add the exhaust system, water pump, oil cooler, oil tank, radiator, pipework, liquid coolant and airbox (if you want to get 100HP) which takes the total to over 90KG."

• The air box is certainly not required, its an optional extra. 
• Exhaust system weight, will vary with applicator just like the air cooled offerings - one point - most Rotax's will use the silencer ,unlike the air cooled mob.
• Water pump is included in the engine dry weight.
• Liquids & heat exchangers are additional (just like the air cooled engines oil coolers & plumbing))

If you want 100HP then the airbox is required.

The exhaust system including muffler is included in the weight of all Jabiru engines as well as the airbox, and Ram air ducts.

Air cooled engines don't have radiators, liquid coolant or associated plumbing. Both types have oil cooler radiators & associated plumbing.

 

The point is the quoted weight of a Rotax 912 ULS is a long way short of the finished installed weight compared to that of most air cooled engines.

Edited April 26, 2023 by kgwilson

[facthunter]

Quite a few of the Common Flat motors don't have (or need) oil coolers and that's SAFER.  Reduction gears  absorb Power and it's a really bad idea to use a prop as a flywheel if its going through gears.   Nev

[skippydiesel]

4 hours ago, kgwilson said:

If you want 100HP then the airbox is required. Please expand on this?

The exhaust system including muffler is included in the weight of all Jabiru engines as well as the airbox, and Ram air ducts. You site an exception to the usual, what of LY-Con, etc?

Air cooled engines don't have radiators, liquid coolant or associated plumbing. Both types have oil cooler radiators & associated plumbing. Air cooled engines are more prone to shock cooling, are , in general, noisier, heavier, have a preference for leaded fuels, require more frequent oil changes.

 

The point is the quoted weight of a Rotax 912 ULS is a long way short of the finished installed weight compared to that of most air cooled engines. Its still got the best power to weight ratio when compared with other, reliable, engines in its hp range. Has a realistic/achievable 2000hr TBO without requiring "major surgery" to get there. High purchase cost aside, is cheaper to operate, quieter and smoother running - whats not to like?

 

[facthunter]

Shouting is rude unless you are at the BAR. I get your idea is that ONLY a Rotax engine is worth having. Nev

[kgwilson]

11 hours ago, skippydiesel said:

11 hours ago, skippydiesel said:

If you want 100HP then the airbox is required. Please expand on this?

 

I thought you would know this as a 912 ULS exponent. To develop the full 100HP cool air is required to feed the carburettors. There is plenty of comment out there in google land. Rotax will not provide any guarantee of 100HP unless their genuine airbox is fitted.

[skippydiesel]

4 hours ago, kgwilson said:

I thought you would know this as a 912 ULS exponent. To develop the full 100HP cool air is required to feed the carburettors. There is plenty of comment out there in google land. Rotax will not provide any guarantee of 100HP unless their genuine airbox is fitted.

Thought that might be the rational - BS of course, not the statement about temperatures effect on hp but the need for an air box. Sure some applications may benefit but definitely not all. Like so many observations/statements they are conditional on installation, configuration, etc. etc.

Edited April 27, 2023 by skippydiesel

[skippydiesel]

4 hours ago, facthunter said:

Shouting is rude unless you are at the BAR. I get your idea is that ONLY a Rotax engine is worth having. Nev

Its not shouting, its differentiating - if I could have used coloured text I would have.

 

I confess to a strong bias, for Rotax 9's, in the 100 hp range of offerings. Beyond 100 hp no particular preference. Have never flown behind anything bigger than 180 hp, so experience very limited.

 

I would be interested to hear some factual commentary on the larger Rotax offering.

[turboplanner]

8 minutes ago, skippydiesel said:

Its not shouting, its differentiating - if I could have used coloured text I would have.

 

I confess to a strong bias, for Rotax 9's, in the 100 hp range of offerings. Beyond 100 hp no particular preference. Have never flown behind anything bigger than 180 hp, so experience very limited.

 

I would be interested to hear some factual commentary on the larger Rotax offering.

You got some factual information but didn't absorb it.

 

If an engine, on bench testing pumps out X bhp at a RPM A

and pumps out more, Y BHP with increased intake pressure and Y happens to be 100 BHP, then it's correct to say that if you want 100 BHP in an operation, you need to use the device which allowed the engine to produce 100 bhp.

Similarly if someone designs and exhaust for sonic extraction, and the engine now produces Z BHP, if you don't fit it, you'll be back to your 100 bhp.

If you do fit it  and you cool the air you've managed to pack into the chamber so far it will expand more in the chamber, producing more pressure so you'll get   Z PLUS BHP provided you don't take off any of the earlier items. 

If Rotax has bench tested the engine and says, to get 100 bhp you need an airbox to increase intake-side pressure, and you don't fit it, you'll be getting less than 100 bhp. You might not think so because it takes about 30 bhp for a noticeable change at the seat of the pants, but that's what happens.

 

 

[turboplanner]

1 minute ago, turboplanner said:

You got some factual information but didn't absorb it.

 

If an engine, on bench testing pumps out X bhp at a RPM A

and pumps out more, Y BHP with increased intake pressure and Y happens to be 100 BHP, then it's correct to say that if you want 100 BHP in an operation, you need to use the device which allowed the engine to produce 100 bhp.

Similarly if someone designs and exhaust for sonic extraction, and the engine now produces Z BHP, if you don't fit it, you'll be back to your 100 bhp.

If you do fit it  and you cool the air you've managed to pack into the chamber so far it will expand more in the chamber, producing more pressure so you'll get   Z PLUS BHP provided you don't take off any of the earlier items. 

If Rotax has bench tested the engine and says, to get 100 bhp you need an airbox to increase intake-side pressure, and you don't fit it, you'll be getting less than 100 bhp. You might not think so because it takes about 30 bhp for a noticeable change at the seat of the pants, but that's what happens.

 

 

 

[BrendAn]

On 26/04/2023 at 5:11 PM, facthunter said:

Napier produced some of the best built stuff  of the period including AERO engines.   Some of the Ricardo "features"  which had copious patents was a bit questionable when subsequent work by people like Cosworth produced much more power from smaller capacity  multi valved engines and the Poppet valves went on from  there to remain pretty much universal. with gas flow figures far better than sleeve valves . The PLUG heads were always hard to cool and the little articulating rods working the sleeve valves  gave trouble in COLD places moving the large area sleeve valves with stiff oil. Rotary valves came and went too but hung around for a while in some 2 strokes induction till reed valves replaced them..  Nev

these might be a good aircraft option one day

[facthunter]

They've been tried pretty extensively. Mazda were about the only firm that hung in with the WANKEL The combustion chamber shape is bad. Too much area/volume and they are thirsty and use a bit of  oil. They are powerful for size and weight and if the start  they will get you home usually. I think they had some moments of glory in racing outboards. They don't like back pressure in the exhaust system. They are generally liquid cooled but NORTON made some aircooled ones. I  saw one in a Pterodactyl at Gympie once. Nev

[BrendAn]

14 minutes ago, facthunter said:

They've been tried pretty extensively. Mazda were about the only firm that hung in with the WANKEL The combustion chamber shape is bad. Too much area/volume and they are thirsty and use a bit of  oil. They are powerful for size and weight and if the start  they will get you home usually. I think they had some moments of glory in racing outboards. They don't like back pressure in the exhaust system. They are generally liquid cooled but NORTON made some aircooled ones. I  saw one in a Pterodactyl at Gympie once. Nev

watch the video, they claim to have solved the issues that rotaries had. 

[skippydiesel]

4 hours ago, turboplanner said:

You got some factual information but didn't absorb it.

 

If an engine, on bench testing pumps out X bhp at a RPM A

and pumps out more, Y BHP with increased intake pressure and Y happens to be 100 BHP, then it's correct to say that if you want 100 BHP in an operation, you need to use the device which allowed the engine to produce 100 bhp.

Similarly if someone designs and exhaust for sonic extraction, and the engine now produces Z BHP, if you don't fit it, you'll be back to your 100 bhp.

If you do fit it  and you cool the air you've managed to pack into the chamber so far it will expand more in the chamber, producing more pressure so you'll get   Z PLUS BHP provided you don't take off any of the earlier items. 

If Rotax has bench tested the engine and says, to get 100 bhp you need an airbox to increase intake-side pressure, and you don't fit it, you'll be getting less than 100 bhp. You might not think so because it takes about 30 bhp for a noticeable change at the seat of the pants, but that's what happens.

 

 

In your dreams - relatively cooler air contains more 02 (its denser) than warmer air. The denser air will allow/ facilitates a more complete (efficient) fuel  burn, releasing more energy from a given fuel charge - as far as I understand it does not increase pressure. To increase engine intake pressure you need a pump (eg turbo  supercharger). I believe we are talking about "volumetric efficiency" which can only be improved when a given swept volume is engineered to process a greater fuel air mixture

 

An air box to carburettor, will probably have a duct to outside (cooler) air  that will marginally improve combustion over a non ducted carburettor operating within the same environment (cowling). However there have been many clever designs that minimise the air temperature rise within the cowling, an air box in this context would just be an expensive talking point.

[Ian]

1 hour ago, BrendAn said:

watch the video, they claim to have solved the issues that rotaries had. 

As facthunter pointed out, the  rotary has are a high surface area to combustion volume so lots of heat gets lost from the engine. This engine suffers from the same issue so it is at an efficiency disadvantage. 

Combustion gets quenched close to the cylinder wall, and because of the more of the fuel remains unburnt contributing to emissions and lower efficiency.

It also has a single piston doing all the work, the other does the exhaust gases so you're going to get differential heat, similar the way that just one side of the rotary has to eject most of the heat, however because it's a piston it's much more difficult to cool.

It's still a cool looking engine though, but the fuel intake through the crank reminds me of the early airplane rotaries.

That being said wankel rotaries are less thirsty than turbines and have a significantly better power/weight and power to volume than conventional piston engines. They have many fewer parts and a rotary rather than oscillating cycle so there's always been the hope of turbine like TBOs. But other mechanical issues have been intractable.

 

Oddly enough Hydrogen as a fuel solves some of the rotary's problems, but I still don't like hydrogen as a fuel.

 

 

 

 

 

 

 

 

[Ian]

On 21/04/2023 at 3:03 PM, Bruce Tuncks said:

I just read a report about a "battery failure" that caused a twin to crash...  there is a real downside to using fuel injection setups which need electrical power to work. I well remember Rod Stiff rejecting the idea on reliability grounds, and this sure proves him  right.

But we have come a long way from the original thrust of this thread which is talking about modes of failure and the fact that a failure in a more complex electrical system can be bad.

This failure can be put into the same basket as someone running an engine at the wrong air fuel mixture and having an engine failure.

Single points of failure can be managed by in most cases by design and procedures, and I think that electronic systems can manage engines and other systems better than people. However poor design and a lack of effective redundancy can lead to poor outcomes. I think that the key question here is whether someone is likely to take off shortly after jump-starting an engine.

Engines like O-360s operated with fully electronic ignition, fuel injection, knock detection and oxygen sensors running in a closed loop have the ability to significantly increase the reliability of aviation powerplants and reduce accidents. But most if not all of these advantages will be lost by DIY implementations.

Wouldn't it be nice if engine telemetry was good enough to warn you that your engine was likely to fail 10 minutes in advance.

 

 

 

[Ian]

2 hours ago, skippydiesel said:

The denser air will allow/ facilitates a more complete (efficient) fuel  burn, releasing more energy from a given fuel charge - as far as I understand it does not increase pressure.

Are you talking about internal engine pressure?

If more energy is released and more power appears at the crank the only way it can get there is through increased pressure or faster rotation.

Work = Force x Distance.

So if the distance remains the same the force must have increased.

The area of the piston head has remained the same so the pressure acting on it must have increased.

So more pressure.

 

[aro]

11 hours ago, kgwilson said:

To develop the full 100HP cool air is required to feed the carburettors. There is plenty of comment out there in google land. Rotax will not provide any guarantee of 100HP unless their genuine airbox is fitted.

Every engine needs an efficient intake and exhaust system to deliver rated power. The difference between Rotax and other makes is 1) Rotax state it explicitly and 2) They supply an optional airbox.

 

Is the intake system on your average Lycoming as efficient as the one use to measure rated power? Who knows - but odds are it isn't. So your average Lycoming probably isn't delivering rated power either.

[BrendAn]

3 hours ago, Ian said:

As facthunter pointed out, the  rotary has are a high surface area to combustion volume so lots of heat gets lost from the engine. This engine suffers from the same issue so it is at an efficiency disadvantage. 

Combustion gets quenched close to the cylinder wall, and because of the more of the fuel remains unburnt contributing to emissions and lower efficiency.

It also has a single piston doing all the work, the other does the exhaust gases so you're going to get differential heat, similar the way that just one side of the rotary has to eject most of the heat, however because it's a piston it's much more difficult to cool.

It's still a cool looking engine though, but the fuel intake through the crank reminds me of the early airplane rotaries.

That being said wankel rotaries are less thirsty than turbines and have a significantly better power/weight and power to volume than conventional piston engines. They have many fewer parts and a rotary rather than oscillating cycle so there's always been the hope of turbine like TBOs. But other mechanical issues have been intractable.

 

Oddly enough Hydrogen as a fuel solves some of the rotary's problems, but I still don't like hydrogen as a fuel.

 

 

 

 

 

 

 

 

do you honestly think these people have have put all this effort into their engine design without any consideration at all. 

Edited April 27, 2023 by BrendAn

[Ian]

6 hours ago, BrendAn said:

do you honestly think these people have have put all this effort into their engine design without any consideration at all.

No not at all. The engine is light weight with high power output and can run on diverse fuels. I'd think that the military would be a key market. If you look at their history the military has given them grants.

However they will have issues with all of points that I've mentioned above. It will be less efficient than your run of the mill diesel engine and cooling will be an issue and sealing the combustion chamber will be difficult, however that doesn't mean there not a market for it.

 

It just like saying that, all other things being equal, a conventional diesel engine will be heavier than a conventional piston engine for a given power output. This is because the pressures are higher in a diesel engine so you have to make the engine stronger by putting more material in the block or using tougher, heavier material like Compacted Graphite Iron. Also diesels revs slower as combustion is slower as it relies on the diffusion and ignition of the fuel in the combustion chamber. You can get around this to some extent by forcing more air into the cylinder through turbocharging however then you need an even stronger heavier engine. 

 

Most engines are air pumps.

 

[facthunter]

I think that rotary is a long way from being viable. Sealing and heat of the ROTOR will be an issue. Just running on no load proves nothing... The wankel did proceed to a working motor  but the NSU version didn't last in the market as well as the Mazda. Nev