F3A--Electric.

[JOddino]

How about a rev limiter?  Probably easy to implement in an electric.  I
always thought it was dumb to run a noise test at full throttle without a
real load.  We don't, or shouldn't fly that way either.
Jim
----- Original Message ----- 
From: "Troy Newman" <troy_newman at msn.com>
To: <discussion at nsrca.org>
Sent: Saturday, August 09, 2003 7:37 PM
Subject: Re: Re:F3A--Electric.


> I don't know for sure about the gear reduction drive....There may be some
> noise from the gear reduction drive yes.....I would bet the majority is
> still from the prop....I listened to the Carerra E setup that Quique has
> flown...To me the noise was from the prop....Now I know the setup that
Jason
> is running is different from that in the Carerra E...but my belief is the
> noise we are getting is from the prop.....I just found it very telling
> running different props on the same model...same setup....and same
> RPM....those with tip speeds up near the 400mph mark were the noisy
> ones....if you busted the 400mph mark it busted the 94db(A) mark as well.
>
> When the tip speeds were down in the 370-380 range the readings on the
sound
> meter were significantly lower like in the 90db(A) range...Now remember
that
> it is a log scale....so the level of the sound is exponentially higher at
> 93-94 than 90.....
>
> Personally I think that the gear reduction unit is significant in the
noise
> the department but I doubt its the noise (93db) the meter is seeing....Now
I
> do understand what Earl has said regarding the frequency...and I would
agree
> with it....
>
> I just see it interesting that I found the main noise contributor on two
> different models as the prop noise.Compared that with other models guys
were
> running where the numbers said yep he's too noisy and yep he was on the
> meter just by looking at the rpms and the prop used.......
>
> Running the number on Jason's hearsay RPM of around 6000, and its a 22"
prop
> that tells me the tip speed on the prop is the same as my setup with he
> 17-12 or the 16.5-12W on my 140DZ.....That being the case, its the same
tip
> speed, is it coincidence that he is reading the same noise levels as what
I
> am getting on my DZ setup?
>
> Now there is no question in the air I bet he is much quieter....but we are
> not measuring anything that has number associated with it in the
air.....its
> all 3 meters away and 30cm off the surface....meter is on the right side
of
> the model (which is the opposite side of the YS exhaust header by the way)
> and the mic is pointed right at the model 90deg to the flightpath....So
> basically the meter is pointed right behind the prop....
>
> I will concede that once you reduce prop noise there is another noise
right
> behind it that takes over as the bully in the system and that is most
likely
> the exhaust and or Vibration in the airframe.....And this is where as Earl
> stated the Woody was 2db lower consistently.....I think what has happened
is
> if we tame the prop noise to say 370-380mph depending on the prop of
> course....the other sounds like vibration resonating in the hollow
composite
> fuse and exhaust noise become the key noise makers to reduce next.
>
>
> I am curious to play with the electric setup....and see why the noise is
> where it is....But I think its really prop noise...the similar setup on
the
> Carerra E,  I have heard in person sounds like a whoosh or a turbine
> sound.......its all prop noise to my un-calibrated ear. There is a whinny
> sound from the gear box but I don't know that this is really the
culprit....
>
> it will be interesting to tell.....the real test would be different gear
> boxes...I think the number I have heard is 6.7 to 1 or something...What
> happens when you change gear ratios and keep the same tip speeds..this
would
> require different props for sure....but if the gear box is turning at
> different speeds and the noise meter bumped up or down significantly then
I
> could assume it was the gear box...but if the noise stayed the same I
would
> think it was still Prop noise....because the prop is still doing its
> 390-400mph thing....
>
> Just some thoughts....I really no nothing about the electric setup and
where
> the noise is coming from....I just thinks its a little ironic that the
prop
> tip speeds are the same as my DZ and the noise meter is hitting the same
> values....
>
> Troy
>
> ----- Original Message ----- 
> From: "Bjorn Lehnardt" <blehnardt at att.net>
> To: <discussion at nsrca.org>
> Sent: Saturday, August 09, 2003 10:03 PM
> Subject: Re: Re:F3A--Electric.
>
>
> > Jason is getting a fair bit of his 93db from the belt reduction drive,
no?
> >
> > ----- Original Message ----- 
> > From: "Troy Newman" <troy_newman at msn.com>
> > To: <discussion at nsrca.org>
> > Sent: Friday, August 08, 2003 8:08 PM
> > Subject: Re:F3A--Electric.
> >
> >
> > Nope weighed with batteries in it....
> >
> > FAI sporting code is available via the NSRCA website and other
> locations...
> > It has the rules regarding the event of F3A...Continues to Surprise me
how
> > few read the FAI sporting code rules for F3A...they are shorter than the
> AMA
> > rule book
> >
> > In some cases the Battery pack is the flight pack also....therefore you
> > don't weigh a model without its flight pack....This is a challenge in
> > Electric F3A models because the batteries are the weight....There are
not
> > many full blown 2M models that will make weight on a full tank of
fuel....
> >
> > Yet the Electric model takes off at under 5kg and flies the entire
flight
> at
> > under 5kg...and lands at under 5kg....Adds a little to the consistency
> mark
> > eh?
> >
> >
> > Also some have claimed its silent flight....Tony said the sound meter
was
> > tipping 93db(A)...That means prop noise is our greatest noise
issue....Who
> > cares about in flight noise...the Sound meter is 3M away from the
> model....
> >
> > Just some FYI.....YS 140DZ turning a 17-12 at 7800rpm is 92-93db(A)...OS
> > 140RX same 17-12 at 7800rpm is the same 92-93db(A) this is roughly
394mph
> > tip speed....
> >
> > Jason is using a 22" prop at around 6000rpm its hit 93db(A) and if you
> > calculate the tip speed its 392mph.
> >
> > So guess what prop noise is the kicker....its not silent flight when you
> are
> > tested at 3meters.
> >
> > This being said I think this is some cool stuff and has some real
> > possibilities...servo pots that last 200-300-400 flights....Airframe
> > vibration is less(still some due to the prop)...can't really build
models
> > much light with the electrics....as they still need to stand up tot he
> > flight loads....I mean how much lighter are you going to build the
> > wing?....Firewalls still need to hold the motors and the thrust
> loads....Yes
> > you can trade pipes, Hyde mounts, and fuel tanks...but you gain the
> battery
> > system....
> >
> >
> > its all very new stuff....Its neat to see someone sticking his neck out.
I
> > wish I had the Brass ones to do it!
> >
> > TN
> >
> >
> > =====================================
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> >
> >
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