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Contra Rotating Propeller Drive for f3a 2m Pattern Planes

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Contra Rotating Propeller Drive for f3a 2m Pattern Planes

Old 11-26-2021, 02:39 PM
  #2001  
Brenner
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Hey John,

Try putting the pinion gear bolt back in and then loosen it up a few turns. Then tap on the head of the bolt with any handy tool. You should be able to knock the bronze insert free.

Brenner ...
Old 11-28-2021, 06:15 PM
  #2002  
ltc
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Hello
I have another quick prop question

I noticed that you can purchase 21” and 22” props with the same pitch front and rear
Is there an advantage or reason why you would want the same pitch front and rear?

I normally see different pitch between the two with the rear prop always having more pitch , like 20 front and 22 rear

As always, thank you
Old 11-28-2021, 06:46 PM
  #2003  
Brenner
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Originally Posted by ltc View Post
Hello
I have another quick prop question

I noticed that you can purchase 21” and 22” props with the same pitch front and rear
Is there an advantage or reason why you would want the same pitch front and rear?

I normally see different pitch between the two with the rear prop always having more pitch , like 20 front and 22 rear

As always, thank you
When a Contra Drive is operating air is accelerated as it passes through the disk of the front prop so when this passes through the disk of the rear prop it is moving faster than it was when it was moving through the disk of the front prop. If the pitch of the rear prop is the same as the pitch of the front prop the rear prop must spin faster to match the torque from each prop. If the pilot wants a setup where both props spin at the same rpm and deliver the same power, then the pitch of the rear prop must be greater than the pitch of the front prop.

The V4 Contra Drive uses a planetary gearbox that automatically adjusts the speed of each prop so that the torque from each prop is equal and opposite, canceling each other out. This means that a V4 Contra Drive will automatically compensate for differences in the pitch of both props. If an Adverun style Contra Drive is used then no compensation is done. The setup will be more sensitive to the selection of prop pitch and prop diameter, and there will be prop effects that can be noticed by the pilot when the pilot transitions from full throttle to low throttle. For this reason, prop selection is more critical with an Adverun style Drive.

Brenner ...
Old 12-04-2021, 07:57 AM
  #2004  
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Question for Brenner: Will the V4 drive be offered with a motor suitable for 12S flight packs?
Old 12-04-2021, 08:14 AM
  #2005  
Brenner
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Originally Posted by FLYERSG View Post
Question for Brenner: Will the V4 drive be offered with a motor suitable for 12S flight packs?
Yes, there are two motors that are being considered. One is being offered for sale right now.

They are both Pyro 600 size motors, but they have been redesigned. The rear bearing has been upsized so that it is now the same size as the front bearings, and the front bearings are held in with a retainer clip. Internally these motors are designed with a threaded assembly that clamps the stator, which eliminates the need for the small cap-screw that retains the stator in the Pyro 600 motor. The windings are rated for 250C continuous and 300C intermittent, and the magnets are rated for 150C intermittent.

These motors also come with a redesigned collapsible collet for attaching the motor to the Drive. This collet clamps the motor shaft in two places, which guarantees perfect alignment between the motor and the Drive, even after severe prop strikes.

There is a 750 rpm/V motor that is available right now that matches the performance of the current 10s V4 Contra Drive, and there is an 812 rpm/V motor that is being tested for pilots who run the D3 rpm governing ESC. This motor is probably too powerful for use with a regular ESC but when used with a D3 ESC it gives the D3 lots of headroom that it can use to govern speed regardless of flight attitude or condition.

Anyone interested in the 750 rpm/V motor can get one through f3a Unlimited. However, you'll probably have to call Mike Mueller directly, because it's not listed on the website yet.

Brenner ...

Last edited by Brenner; 12-04-2021 at 08:18 AM.
Old 12-04-2021, 09:12 AM
  #2006  
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Thanks for the information. I also fly precision aerobatics with helicopters and run all of my Kontronik Kosmik and Jive Pro ESCs at 80% in Idle Up 2 to allow the governor to work so while I don't use the D3 ESC, I understand the need for its headroom. Might there be some advantage to using the 812kv motor with, for example, a Jive Pro and limit the throttle end point to provide for a prop RPM equivalent to a typical V4 10S setup? Then, on a very windy day, one would have the option of increasing the throttle end point as needed to gain a bit more speed. Just a thought.

Mike
Old 12-04-2021, 09:24 AM
  #2007  
Brenner
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Originally Posted by FLYERSG View Post
Thanks for the information. I also fly precision aerobatics with helicopters and run all of my Kontronik Kosmik and Jive Pro ESCs at 80% in Idle Up 2 to allow the governor to work so while I don't use the D3 ESC, I understand the need for its headroom. Might there be some advantage to using the 812kv motor with, for example, a Jive Pro and limit the throttle end point to provide for a prop RPM equivalent to a typical V4 10S setup? Then, on a very windy day, one would have the option of increasing the throttle end point as needed to gain a bit more speed. Just a thought.

Mike
The 812 motor that's being tested right now really has way too much power to be used without some sort of rpm limiter. My concern is that there's no practical way to guarantee that it wouldn't drive the motor way past it's rpm limit under certain flight conditions (for instance, diving at full throttle..) to recommend it's use without something like a D3 ESC, which has a specific rpm limiter built-in.

The 750 motor has more than enough power for anyone. I can say with good confidence that no one is going to complain about the power that's available with the 750 motor.

Brenner ...
Old 12-04-2021, 09:56 AM
  #2008  
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One more question. What capacity 12S flight pack do you recommend (I fly Masters)?
Old 12-04-2021, 11:12 AM
  #2009  
Brenner
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Originally Posted by FLYERSG View Post
One more question. What capacity 12S flight pack do you recommend (I fly Masters)?
Unfortunately, I don’t fly Masters so I can’t speak from personal experience. However, Tony Frackowiak has been having success with 4400 6s packs.

Brenner…
Old 12-05-2021, 10:33 AM
  #2010  
ini
 
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Where can you use 12S batts in competition?
Old 12-05-2021, 12:18 PM
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Brenner
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Originally Posted by ini View Post
Where can you use 12S batts in competition?
In the United States the AMA is going to allow 12s packs in pattern competition starting in 2022...

Brenner ...
Old 12-06-2021, 01:01 AM
  #2012  
ini
 
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Good to have choices. Benefit of 12S over 10S seems to negligible. Same ESC, same size motor, maybe cable could be thinner.

At least in Europe you can find decent 5S 5Ah packs 570g/20oz. 6S packs are not any lighter.
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Old 12-06-2021, 03:07 AM
  #2013  
Brenner
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Originally Posted by ini View Post
Good to have choices. Benefit of 12S over 10S seems to negligible. Same ESC, same size motor, maybe cable could be thinner.

At least in Europe you can find decent 5S 5Ah packs 570g/20oz. 6S packs are not any lighter.
The primary benefit is that the system runs cooler. This is a benefit here in the United States because ambient temperatures regularly exceed 40C.

Brenner ...

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