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The sound of a paramotor


pegasus1
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Right Lads, don't get too technical on me here as I am only a girlie, but I would like to know if we can quieten our motors. Is it possible to fit baffles in the exhaust or use a 4 stroke engine which I would presume would give more torque, be more reliable and overall be quieter? This might already be in existance or a really simple answer as to why not, but I just wanted to know. Electric engines are in production although very expensive I have read. I find the motor extremely noisey personally and having just got back from the pub, it appears so do most of the locals!!!

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Hi Pegasus.

My thoughts.......small engines can be made very quiet. They sell electric generator sets that you can hardly hear, for camping etc. using exhaust baffles and sound proofing around the engine. You can even use electronics to deaden the sound. All these add weight and expense and use up power. But a lot of the noise does not come from the engine it comes from the prop. The wider the prop the closer to the speed of sound the tips get (generally). Some props really bark cos the tips are making sonic booms! reducing the diameter and the speed of rotation makes them quieter but then their intake area is shielded by the pilot.

One way is to put the prop in a tube (ducted fan), but much more expensive....and where to put the pilot?

Our machines are pretty expensive for what they are. Yes they could be quieter (but probably not much) at greater expense .

What to do? some suggestions. Dont fly over the same people every day. Use noise cancelling ear defenders (expensive ones that really work). Fly high and choose a sparsely populated flight path. If you have to fly lowish over a house or garden party fly directly over as the prop noise spreads out sideways and they hear it for a shorter period (not sure if thats all that effective actually).

Take up hill soaring its really peaceful. Learn to thermal ( fly to where the air is rising and switch off your motor), you can stay up for hours without any engine.

:D

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I did think of making a sound deflector.... not sure how effective it would be, simple enough to try.

Just a sheet of something bent to form a duct on just the lower section of the motors frame.

The 4 stroke idea sounds like a good one, but ( I think it has more 'Bass' or lower frequency sound waves, which go further through the air ) so can be heard for miles!

Having heard an electric Paramotor they are much quieter but as Francis says... as soon as you spin the prop up to full chat you can still hear the blades cutting through the air.

The Problem with 2 strokes and silencing the exhausts, is that the exhaust is a tuned part of the engine, and as soon as back pressures are altered (by the use of a bigger silencer for example) it all goes pete tong.

Rotary? no need for an exhaust..... in the same breath you can silence it as much as you like.. Rotary Paramotor some time away but I think that this would be the best way of getting a quieter Paramotor.

SW :D

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Thinking back to the old John Player Norton rotary days; Brian Crighton could make one produce serious hp, but they were very very noisy!! I think anything that is in a high state of tune has the potential to be very noisy; fourstrokes are heralded in the PPG world as quiet, yet some of the noisiest bike engines are 4 stroke!

There are some good ideas floating about from various manufacturers as far as I can see; exhaust outlets that point upwards is one, and one of the main sources of noise for a 2T engine after the expansion chamber, is the inlet noise; if you dont have an air box, fit one youll be amazed at the sound it reduces; and youll get more power too how nice is that :-)

I'm new to this but I think the key to prop noise is tip speed, and from what Ive seen and heard, the smaller engined machines seem to make the most noise; probably because the 100cc and below engines are spinning close to 10,000rpm to make sufficient power, whereas the bigger engines rev at lower rpm's and have a little more torque available to move a bigger prop.

Looking at Freshbreeze Simonini (everyone says theyre the quietest), the exhaust outlet points up to heaven, the expansion chamber is wrapped (kills noise and chamber resonance as well as its primary purpose keeing heat away from other stuff), the base of the frame has a noise deflector plate, and the engine revs have been reduced (I understand FB retunes the Sim to rev a little lower with increased torque).

I think Paramotors are like mopeds; passers by get much more irritated by a noisy moped than a noisy bigger bike, because the moped is around for longer; whereas the bigger bike has been and gone in a blink!!!

I was at a frinds microlight strip the other day, and the guy running it was asking how I was getting on with my PPG training I said 'fine; when Im airworthy should I drop in on you?' From the uncomfortable silence (similar to that after an impromptu fart escapes...) I gathered I would not be too welcome LOL My pal explained after it was because of the noise worries; yet have you heard a microlight at full chat??!!

Interesting topic Pegasus, let us know how you get on with your noise reduction.

Regards

Steve

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Thinking more on the rotary theme, the established problems that still need a solution are; tip seal wear, high fuel consumption, and the need for very specialist lubricants (not available as easily as 2T oil or 4T oil is at most garages).

The automotive industry has, with the exception of Mazda, given up on the rotary, and the old Norton Rotary is only used in target drones now where engine life is of no concern!!! (Some say its the best thing you can do to a rotary; how cruel!!)

There is an ongoing arguement as to what the actual cubic capacity of a rotary engine is; there are two schools of thought on this; one definition makes the rotary look highly efficient for its size, but with very heavy fuel consumption, whereas the other definition makes a rotary look inefficient for its size, but explains the fuel consumption !!!

I thnk were stuck with the old piston engine for a while yet; I think the future lies with better, lighter built four stroke engines; but the 2 stoke makes the most sense now (for me anyway)

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All taken onboard Steve. Makes for some very interresting reading. But don't forget the number one designer in the UK (IMO) designed and flew a rotary over Everest this year!

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Cant argue with that at all; a brilliant feat; but the needs of an Everest machine; and those of more normal users are quite different arent they?

Im sure the Everest guys werent worried about a bit of extra noise, long term rotor tip wear, availability of specialist oils and a bit heavier fuel consumtion!!

I must say that Everest machine looked the dogs doo dahs at Splash; but maybe my heart was just taken by that shiny pointed ally spinner on the prop LOL

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