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Contra Rotating Propeller Drive for f3a 2m Pattern Planes

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Old 03-29-2011, 04:54 PM
  #201
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Default RE: Contra Rotating Propeller Drive for f3a 2m Pattern Planes

I'm planning on it. Might make the Victorville contest this weekend if everything works out.
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Old 03-30-2011, 08:07 AM
  #202
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Default RE: Contra Rotating Propeller Drive for f3a 2m Pattern Planes

Here's a picture of John Martin's Wind S Pro with his new Contra Drive installed. (John said I could post this ..) The gold spinner is perfect match for the yellow paint scheme, and I love how the lines of the spinner blend in with the profile of the fuse. This is a very good looking plane.

Currently John only has five or so flights on the system. He says that he will report out on RCU when he has a little more stick time.
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Old 03-30-2011, 02:46 PM
  #203
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Default RE: Contra Rotating Propeller Drive for f3a 2m Pattern Planes


Quote:
ORIGINAL: serious power
On a hard surface it sounds like a big ,in line,4 cylinder motor cycle engine.A very pleasant sound.In the air it sounds just as I remember Seba's ,so that's the same sound/noise but with a lot more performance.
I will do noise tests in the next week or so.
This is good to hear. I hope your noise test will confirm this. This system seems to have the propellers closer spaced then the e-factor unit (silvestri) and thus should have more “blade interaction noise”. I have tested varying the prop distance on a smaller (indoor) counter rotating motor and, as expected, decreasing distance resulted in a seemingly exponential noise increase. There are more factors involved then just the blade distance so hopefully I’m wrong and, as you say, this system is as good as the e-factor. Either way I still want one!

/David
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Old 03-30-2011, 03:21 PM
  #204
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Default RE: Contra Rotating Propeller Drive for f3a 2m Pattern Planes

(Cross-posted in both forums)
Brenner, any plans to make a Contra Drive for the sibling Wind S50e? I'd love to have one for mine!!
Rick

Quote:
ORIGINAL: Brenner

Here's a picture of John Martin's Wind S Pro with his new Contra Drive installed. (John said I could post this ..) The gold spinner is perfect match for the yellow paint scheme, and I love how the lines of the spinner blend in with the profile of the fuse. This is a very good looking plane.

Currently John only has five or so flights on the system. He says that he will report out on RCU when he has a little more stick time.
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Old 03-30-2011, 06:39 PM
  #205
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Default RE: Contra Rotating Propeller Drive for f3a 2m Pattern Planes

Hey Rick,

There are no immediate plans to make a downsized version of the Contra, but that's because we have our hands full right now with the 2m version. If this version proves successful, then I'm sure we'll find the time to downsize it, and maybe even upsize it.

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Old 03-30-2011, 07:34 PM
  #206
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Default RE: Contra Rotating Propeller Drive for f3a 2m Pattern Planes

Sure hope so! I have a GP Sequence with a little Neu geared inrunner just screaming for a contra drive! You'd have to fly this model to believe how good it flies now. Can't imagine how good it would be with a contra!
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Old 03-30-2011, 11:03 PM
  #207
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Default RE: Contra Rotating Propeller Drive for f3a 2m Pattern Planes


Quote:
ORIGINAL: Reko


Quote:
ORIGINAL: serious power
On a hard surface it sounds like a big ,in line,4 cylinder motor cycle engine.A very pleasant sound.In the air it sounds just as I remember Seba's ,so that's the same sound/noise but with a lot more performance.
I will do noise tests in the next week or so.
This is good to hear. I hope your noise test will confirm this. This system seems to have the propellers closer spaced then the e-factor unit (silvestri) and thus should have more “blade interaction noise”. I have tested varying the prop distance on a smaller (indoor) counter rotating motor and, as expected, decreasing distance resulted in a seemingly exponential noise increase. There are more factors involved then just the blade distance so hopefully I’m wrong and, as you say, this system is as good as the e-factor. Either way I still want one!

/David
Hi David,
No I'm not saying that this is as good as the E-Factor unit.
I have seen Seba,and team mates,fly the E-Factor a lot. We shared practice sites in Austria and I saw quite a lot of it in action in Portugal (meet you there ?).
I'm saying this is way better.This has awsome performance.It is not loud. This can be matched to personal preference,model choice and battery choice by a combination of prop and/or gear changes.
I believe these props are more efficient in their own right.

Brian
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Old 03-31-2011, 12:56 AM
  #208
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Default RE: Contra Rotating Propeller Drive for f3a 2m Pattern Planes

Brian, yes we met in Portugal. We always ended up at that “fancy” Chinese restaurant

I expressed myself imprecisely. I meant “as good” in terms of noise level. The efactor system already seems to be close to the limit in noise tests (requires innovative throttle curve?). If the Brenner system is equivalent in sound but better in power that is just awesome! I have to argue with my wife about how to spend the family budget this summer.

/David
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Old 03-31-2011, 02:36 AM
  #209
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Default RE: Contra Rotating Propeller Drive for f3a 2m Pattern Planes

Hi David,
Good to talk to you again and I hope the 'negotiations' go well for you
Seba 't-curve' at the noise test would give the impression that he has to try extra hard.
I think he is trying to impress upon the world that his system is super quiet,he is a little inclined to be demonstrative.
However if you check his actual readings (they are on the EC website) you will find they are in the low 80's ???

Brian
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Old 03-31-2011, 09:56 AM
  #210
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Default RE: Contra Rotating Propeller Drive for f3a 2m Pattern Planes

Interesting comments about noise.

We did a fair bit of testing last year with regard to noise, and we also found that the noise due to blade passing frequency was inversely proportional to the spacing between the front and rear props, but we also found that beyond a critical separation distance this component of noise quickly reduces to a small value.

We added an additional 25mm of separation distance between the front and rear props on our prototype unit, and the prop interaction noise was pretty much eliminated. All that was left was the noise that is typical with 2m electric single prop setups.

However, we also found that once you have enough separation between the props, that the design and the rpm of the propeller blades starts to dominate, and it is possible to still have noise coming from the system that's due to just the props alone, especially since there are two props instead of one.

So, we concluded that prop separation was critical up to a certain clearance, but that propeller design and rpm was critical regardless of separation distance because there are two potential noise sources in a Contra system instead of one.

This was one of the reasons why we stuck with 22" diameter props, with high pitch to keep the rpm down.

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Old 04-03-2011, 10:14 AM
  #211
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Default RE: Contra Rotating Propeller Drive for f3a 2m Pattern Planes

Hi,

Some pics from integral with red contra-drive.

Vincent
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Old 04-03-2011, 10:28 PM
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Default RE: Contra Rotating Propeller Drive for f3a 2m Pattern Planes

Hi Vince

Where did you buy et how much is it ?
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Old 04-04-2011, 12:50 AM
  #213
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Default RE: Contra Rotating Propeller Drive for f3a 2m Pattern Planes

Hi Mr Cuinet,

How do you do ?
Everything is shown on this forum. Mr cuiui would abandon his beloved YS ?
It is never too late to do well.


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Old 04-04-2011, 01:02 AM
  #214
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Default RE: Contra Rotating Propeller Drive for f3a 2m Pattern Planes

Hi Mister Vince

I go on with YS CDI.
No electric motor for me. Just because time of flight is short. And charge batterie is binding to survey them.
I do many flights and until 20 mn per flight if i wish in one day on field with 5 liters of fuel.
Claude
my new one named Avenir
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Old 04-04-2011, 01:49 AM
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Just joke, I love also YS.

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Old 04-04-2011, 02:05 AM
  #216
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Default RE: Contra Rotating Propeller Drive for f3a 2m Pattern Planes

YS = Y(Why) Suffer?

Isn't this an electric forum?

Cheers,
Jason.
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Old 04-04-2011, 02:57 AM
  #217
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Default RE: Contra Rotating Propeller Drive for f3a 2m Pattern Planes

Hi jason

You're right. I think me and friends of mine who love YS are masochist (joke) !
Friend of mine Franck did the same plane with electric motor.
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Old 04-08-2011, 11:50 AM
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Default RE: Contra Rotating Propeller Drive for f3a 2m Pattern Planes


Quote:
ORIGINAL: TonyF

Sure hope so! I have a GP Sequence with a little Neu geared inrunner just screaming for a contra drive! You'd have to fly this model to believe how good it flies now. Can't imagine how good it would be with a contra!
Hi Tony,
Have you tried to mix the props yet.
If not can you try the 22x18 in front and the 22x20 rear.
I have and it is going very well with a very different sound,and a very nice sound.

Brian
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Old 04-08-2011, 01:19 PM
  #219
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Default RE: Contra Rotating Propeller Drive for f3a 2m Pattern Planes

Brian that's good to know, I was planning on trying that to equalize the loads and hopefully the rpm of the two props.

Dave
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Old 04-08-2011, 02:19 PM
  #220
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Default RE: Contra Rotating Propeller Drive for f3a 2m Pattern Planes

Hi Dave,
Yes have a go, I could not believe the change in sound.
I have the 10.15 gear set in also.

Brian
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Old 04-08-2011, 07:25 PM
  #221
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Default RE: Contra Rotating Propeller Drive for f3a 2m Pattern Planes

I'll try it the next time I get out. It's been extremely windy here the last few days. Even some sleet last night!
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Old 04-08-2011, 08:00 PM
  #222
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Default RE: Contra Rotating Propeller Drive for f3a 2m Pattern Planes



Tony,

Gotta love the high desert of California this time of year. We always had wind and weather in Ridgecrest that would surprise everyone once in awhile.

Californian living in Sunny Florida.

Mike P

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Old 04-09-2011, 06:26 PM
  #223
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Default RE: Contra Rotating Propeller Drive for f3a 2m Pattern Planes

We have a Logo! These are the first props that Mike has made with our new logo.
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Old 04-10-2011, 10:12 AM
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Default RE: Contra Rotating Propeller Drive for f3a 2m Pattern Planes

You guys are well ahead of me with mixing the props sizes. Right now I'm stuck in India for the week, so I won't be able to try anything until I get back this weekend.

Dave is right in that having a higher pitch prop in the rear will help equalize the rpms of the props at a lower speed. The relative rpm of the front and rear props will always be changing as a function of airspeed, but if both props are the same pitch then the relative rpm difference will only be minimized at max horizontal speed.

One way to know when this is happening is to listen for a "synchopating rhythm sound", because this sound can only be generated when the rpm of the two props approaches being equal.

In theory, this would be the speed at which the Drive is performing most efficiently, so ideally we would want to hear this sound when the Drive is absorbing the most power, probably during the vertical climbs.

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Old 04-12-2011, 03:49 AM
  #225
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Default RE: Contra Rotating Propeller Drive for f3a 2m Pattern Planes

Hello
Where is it possible to buy the contra rotating system?
What change in lenght is it from a "normal" electric setup?
Any prices?

Regards
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