why are aircraft engines so noisy?

[Old Koreelah]

I know its getting away from the original thread but, no Harley will ever sound as good as a Ducati with Conti's !!!!!!!!!!!!!!!1

Ducatis are proper motorcycles.

 

 

[M61A1]

Ducatis are proper motorcycles.

Damn right. gotta have a 90 degree V and desmo valve gear to make the right sound.

[Old Koreelah]

Damn right. gotta have a 90 degree V and desmo valve gear to make the right sound.

One year at Bathurst I got to hear the difference Desmo makes. A couple of Ducatis in company with a pair of Moto Guzzi 850 Le Mans fitted with Conti pipes. Both 90 degree V twins of similar capacity. As they hurtled down to Forest Elbow and powered out down Conrod we got to hear the most beautiful of engines. Despite their similarity, the Ducati was quite distinctive.

 

 

[M61A1]

One year at Bathurst I got to hear the difference Desmo makes. A couple of Ducatis in company with a pair of Moto Guzzi 850 Le Mans fitted with Conti pipes. Both 90 degree V twins of similar capacity. As they hurtled down to Forest Elbow and powered out down Conrod we got to hear the most beautiful of engines. Despite their similarity, the Ducati was quite distinctive.

I think the distinctive sound comes from the way the desmodromic system has a much steeper ramp up on the cam. The valves open faster and stay open for longer than a similar valve spring system.

[boingk]

Its also an outdated technology from an era when you started to get valvefloat at 6,000rpm or so as they didn't have the materials needed for good valvesprings.

 

They're also a massive pain in the ass to service... much prefer Hondas or BMW's in that regard.

 

Do sound good though!

 

- boingk

 

 

[Virago]

My Virago XV1100 sounded pretty good with a set of shotgun pipes!

 

 

[M61A1]

Its also an outdated technology from an era when you started to get valvefloat at 6,000rpm or so as they didn't have the materials needed for good valvesprings.They're also a massive pain in the ass to service... much prefer Hondas or BMW's in that regard.

 

Do sound good though!

 

- boingk

Well they still do well in competition, and I've never had much trouble servicing them, all you need is basic maths and a micrometer, in fact I'd rather do desmo than bucket shims.

[boingk]

And I'd rather do screw and locknut than either. Its not the actual valves that are the problem but more the fact that you need to dick around so much with the bodywork, tank, and engine perhipherals before you even get the the valves.

 

I'm just not a fan of Ducati maintenance logic. My old XR600R, for example, had two bolts to remove the tank and then you were at the valve adjusters after undoing their caps with a large adjustable wrench or 27mm spanner. WHole process including an oil and filter change took 30 minutes. Thats servicing logic.

 

As for racing, they do still do well, but Yamaha and Honda are the ones dominating GP races, and Aprilia and BMW are killing the Superbike field stone cold.

 

- boingk

 

 

[dazza 38]

And I'd rather do screw and locknut than either. Its not the actual valves that are the problem but more the fact that you need to dick around so much with the bodywork, tank, and engine perhipherals before you even get the the valves.I'm just not a fan of Ducati maintenance logic. My old XR600R, for example, had two bolts to remove the tank and then you were at the valve adjusters after undoing their caps with a large adjustable wrench or 27mm spanner. WHole process including an oil and filter change took 30 minutes. Thats servicing logic.

 

As for racing, they do still do well, but Yamaha and Honda are the ones dominating GP races, and Aprilia and BMW are killing the Superbike field stone cold.

 

- boingk

I owned 2 Honda XR 250's and 1 XR 350 back in the day. Excellent design & simple valve adjustment.

 

 

[Old Koreelah]

One of the reasons there are so many former Ducati owners around is that, like sports cars, they we never meant to be a practical means of transport. "When your heart says Ducati, your head says Guzzi"- a much simpler machine to own.

 

I recently bought an old K75 and was told it will go forever, so don't touch it, just ride it. Almost true. Compared to the Ducati, the BM is a joy to work on. Simple modular design, easy to get at most things.

 

 

[cooperplace]

One of the reasons there are so many former Ducati owners around is that, like sports cars, they we never meant to be a practical means of transport. "When your heart says Ducati, your head says Guzzi"- a much simpler machine to own.I recently bought an old K75 and was told it will go forever, so don't touch it, just ride it. Almost true. Compared to the Ducati, the BM is a joy to work on. Simple modular design, easy to get at most things.

While it's fantastic to see so many people passionate about wonderful machinery such as Ducatis (and I don't claim they were great from an engineering perspective, merely seductive), it'd be nice to get back to the original thread topic. So I ask all the engineering geniuses out there (this clearly includes everyone who has contributed to this thread) the following question:

if the weight of a small plane, eg Jabiru or Rotax powered, could be increased by up to 5kg, and the cost increased by up to $5000, how much quieter could the plane be? Assuming no penalty in terms of safety.

 

These numbers I have plucked out of the air, on the basis of a rough guess of what might be acceptable to many pilots if push came to shove. If you see what I mean.

 

Opinions, anyone?

 

 

[cooperplace]

And I'd rather do screw and locknut than either. Its not the actual valves that are the problem but more the fact that you need to dick around so much with the bodywork, tank, and engine perhipherals before you even get the the valves.I'm just not a fan of Ducati maintenance logic. My old XR600R, for example, had two bolts to remove the tank and then you were at the valve adjusters after undoing their caps with a large adjustable wrench or 27mm spanner. WHole process including an oil and filter change took 30 minutes. Thats servicing logic.

 

As for racing, they do still do well, but Yamaha and Honda are the ones dominating GP races, and Aprilia and BMW are killing the Superbike field stone cold.

 

- boingk

I too have owned lots of Japanese bikes. While they were all so much better than a duke in many ways, I don't miss them as much. Maybe that just says something about me?

 

 

[Gnarly Gnu]

Opinions, anyone?

Muffler (for Jabiru at least) + line the inside of the engine compartment with faced glasswool.

 

 

[Old Koreelah]

if the weight of a small plane, eg Jabiru or Rotax powered, could be increased by up to 5kg, and the cost increased by up to $5000, how much quieter could the plane be?

Opinions, anyone?

Slower prop, larger blades. Better muffled engine. For volume manufacturers like Jabiru, a major redesign, costing heaps.

 

Wait for electric?

 

 

[Sapphire]

OK said: Wait for electric?

 

Electric is here [on this world] though the largest battery I've seen costs nearly $10,000 in USA and won't be cheaper here. Your cost accounting for a weed hopper would need to be revaluated.

 

 

[Old Koreelah]

Electric is here [on this world] though the largest battery I've seen costs nearly $10,000 in USA and won't be cheaper here. Your cost accounting for a weed hopper would need to be revaluated.

I meant wait for electric to become affordable. The price of rare earths is currently similar to fuel prices after the oil shocks of the 1970s. At that time many of us thought petrol was running out fast. Holden abandoned the big car and adapted a small German 4 cylinder car to be their flagship. High oil prices stimulated exploration and a generation later fuel was plentiful and cheap again.

Right now China dominates the supply of rare earths, but more will be found in other places; prices of motors and batteries will fall.

 

 

[cooperplace]

I meant wait for electric to become affordable. The price of rare earths is currently similar to fuel prices after the oil shocks of the 1970s. At that time many of us thought petrol was running out fast. Holden abandoned the big car and adapted a small German 4 cylinder car to be their flagship. High oil prices stimulated exploration and a generation later fuel was plentiful and cheap again.Right now China dominates the supply of rare earths, but more will be found in other places; prices of motors and batteries will fall.

perhaps if I could re-phrase the Q to:

weight increase up to 5kg

 

cost increase up to $5000

 

sticking with petrol engines.

 

Personally I can't ever see a kg of battery ever storing as much energy as a kg of petrol.

 

 

[Old Koreelah]

...Personally I can't ever see a kg of battery ever storing as much energy as a kg of petrol.

You are probably right, but an electric motor is a fraction of the weight of current aero engines.

When/if power, endurance and cost become competitive, designers will be freed from current limitations caused by a heavy engine and liquid fuel.

 

 

[cooperplace]

You are probably right, but an electric motor is a fraction of the weight of current aero engines.When/if power, endurance and cost become competitive, designers will be freed from current limitations caused by a heavy engine and liquid fuel.

interesting point; maybe <30kg could be saved, so if you wanted lots of endurance, this wouldn't be useful, but if you only wanted to fly for say 90 min, maybe it could work. if you know any well-considered discussions of electric motors in light planes, pls pass this on.

 

 

[bernieh]

Merlin symphony

 

 

 

[boingk]

interesting point; maybe <30kg could be saved, so if you wanted lots of endurance, this wouldn't be useful, but if you only wanted to fly for say 90 min, maybe it could work. if you know any well-considered discussions of electric motors in light planes, pls pass this on.

Check out 'cri cri electric' on YouTube.- boingk

 

 

[M61A1]

And I'd rather do screw and locknut than either. Its not the actual valves that are the problem but more the fact that you need to dick around so much with the bodywork, tank, and engine perhipherals before you even get the the valves.I'm just not a fan of Ducati maintenance logic. My old XR600R, for example, had two bolts to remove the tank and then you were at the valve adjusters after undoing their caps with a large adjustable wrench or 27mm spanner. WHole process including an oil and filter change took 30 minutes. Thats servicing logic.

 

As for racing, they do still do well, but Yamaha and Honda are the ones dominating GP races, and Aprilia and BMW are killing the Superbike field stone cold.

 

- boingk

That's not really comparing apples with apples. The Honda equivalent of most Dukes would be a CBRR (add more Rs if necessary) or an R1 if you're into Yamaha, now there's a pain to work on. I used to have a nice little Pantah, in 10 minutes, I could have the engine out and on the bench. Part of the beauty of the trellis frame design. I concur with Koreela though, the Guzzi in my 95.10 is very simple to maintain ( and it sounds good). I had someone ask the other day "is that your plane that sounds like a ducati going past?"(cruise @4800rpm)

[M61A1]

You are probably right, but an electric motor is a fraction of the weight of current aero engines.When/if power, endurance and cost become competitive, designers will be freed from current limitations caused by a heavy engine and liquid fuel.

Boeing have been working on a hydrogen fuel cell that is very promising. They have had UAV's in the air for extended periods using the fuel cell and electric motors. I think that this will be the best option. The hydrogen fuel cell just makes electricity, then use a large brushless motor (high torque/low rpm) to spin the biggest prop you can physically fit. It's been done, it just needs to become affordable.http://en.wikipedia.org/wiki/Hydrogen-powered_aircraft

 

 

[boingk]

Check out the gear at hobbyking dot com, they stock a large variety of very efficient large brushless motors.

 

I could see fitting a 95-10 out with some, to be honest. The largest expense though would be the batteries and the requisite high-power charger to keep them topped up.

 

CHeers - boingk

 

 

[facthunter]

Noise from engines is OK for a while but after hours and hours you are glad for lack of noise This is what you get in a glider or (almost ) in some jets where the engine(s) are way down the back. Low frequency vibration is annoying too. and it makes things vibrate, fret and crack. Electric motors will be a new dimension in quietness, but I'll never stop running outside to see anthing with ONE or MORE (preferrably the latter) BIG ROUND ENGINES. ( the ones with cylinders sticking out all around the crankcase) Nev