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  • May 20, 2019, 03:36:40 AM

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Author Topic: Counter Rotating Propellers for Stunt  (Read 3768 times)

Offline Matt Spencer

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Re: Counter Rotating Propellers for Stunt
« Reply #50 on: March 18, 2019, 05:53:25 PM »


Two high-density YASA electric motors are planned to provide the power for the P1e.

https://www.aerosociety.com/news/bright-sparks-the-quest-for-electric-speed/


Offline Matt Piatkowski

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Re: Counter Rotating Propellers for Stunt
« Reply #51 on: March 19, 2019, 07:18:11 AM »
Hi Matt,
It is always good to know what other people did and are doing.
Happy (electric) Flying,
Matt

Offline John Rist

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Re: Counter Rotating Propellers for Stunt
« Reply #52 on: March 19, 2019, 12:24:59 PM »


Two high-density YASA electric motors are planned to provide the power for the P1e.

https://www.aerosociety.com/news/bright-sparks-the-quest-for-electric-speed/

Now there's a candidate for an electric scale project.  Won't need a sound generator.
John Rist
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Offline Archie Adamisin

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Re: Counter Rotating Propellers for Stunt
« Reply #53 on: April 24, 2019, 07:01:16 PM »
What an interesting read.  Perhaps posting this pic and video are relevant.





Archie Adamisin
Burlington, KY
Archie Adamisin
Burlington, KY

Offline Steve Helmick

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Re: Counter Rotating Propellers for Stunt
« Reply #54 on: April 24, 2019, 08:12:17 PM »
It occurred to me to ask if having two props wouldn't make it more difficult to make the ideal 1 lap minimum glide for F2B competitions? But then, it's not always too easy to tell just when the power is definitely "off", since the prop on electrics typically windmills during the glide. Seems like the friction of the gear system would tend to stop the windmilling. A two motor counter rotating system sounds better than gears, but maybe higher weight. It would suck to be doing the OH8 when the gearbox suddenly went Tango Utah. 

Further, I recall somebody here writing that a windmilling propeller creates more drag than a stopped propeller, but I just don't see the logic of that. So glad I don't have to worry about this stuff!  y1 Steve
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Offline Matt Piatkowski

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Re: Counter Rotating Propellers for Stunt
« Reply #55 on: April 25, 2019, 07:25:15 AM »
Hi Archie,
Could you please provide some technical details regarding the contra system you are showing on youtube?
Specifically: the maximum continuous current, gear box ratio, weight and diameter and pitch of the props. used.

Thank you,
Matt Piatkowski

Offline T.J. Vieira

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Re: Counter Rotating Propellers for Stunt
« Reply #56 on: April 25, 2019, 08:50:01 AM »
there was a company at the Toledo show that had setups for this...

http://www.maxxprod.com/mpi/mpi-266.html


Offline TDM

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Re: Counter Rotating Propellers for Stunt
« Reply #57 on: April 25, 2019, 09:26:53 AM »
This subject really peaked my attention and looked over it and searched what is practical and what is not practical tried to see how could it be implemented and what are the benefits.
Starting with benefits By the looks of it No gyroscopic precession more laminar airflow behind the props.
Now for the practical side.
Two options: Firs is gear box drive and the second option two motors.
For the gear box the first thing that goes through my mind is something like this should work and is doable . For this one you must have some precision gears off the shelf preferably plus precision work to get it up and running. Several bearing must be used plus shafts that must fit props adapters special spinners in my book it translates to (it can be made but it is complex  heavy perhaps a little less than the weight of a second motor but you need a bigger motor to drive this whole mess the weight of the second prop,  weight+weight+weight+etc. did I mention weight?
For option two hack up two motors with some parts and go for it. This is the much simpler implementation it adds yet another motor another ESC, it is  pretty easy to make but you still have to mess with the spinner back-plate make some little parts for the motors assembly (no real issues here). But again did I mention weight of the second motor and ESC weight of the extra parts and this will be in the few ounces range.

This is the point where I always go back to some kind of aerodynamic device like the wing behind the canopy to clean up the air to the stab (tipping the scale at 10g maybe) and a Rabe Rudder setup (another 10g) both of which solve the same problems and are crazy much simpler to make and accessible to all. It can be fun to try counter rotating but for me I do not see the point my no BS thinking is saying that it is at best a novelty, o r i cant think about what otters are doing and how it can be implements. Maybe the guy at the wolds can tall us how he justifies and had implemented the concept. I am always want to accept new ideas and to things I don't see.
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Offline Matt Piatkowski

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Re: Counter Rotating Propellers for Stunt
« Reply #58 on: April 25, 2019, 01:47:59 PM »
Hi TDM,
shows exactly the straight (spur) gears and their configuration used in "Polish Contra". The latest gear box in this contra has helical gears and should be quieter but it is prohibitively expensive.

Hi Vieira,
The "two motors contras" (http://www.maxxprod.com) are very reasonably priced. CR3516-1030 system seems to be well suited for F2B but the extensive flight testing is needed to prove it.

Thank you,
Matt

Offline Howard Rush

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Re: Counter Rotating Propellers for Stunt
« Reply #59 on: April 25, 2019, 03:56:52 PM »
The latest gear box in this contra has helical gears and should be quieter but it is prohibitively expensive.

Expense does not prohibit the Jive Combat Team.
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Offline Howard Rush

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Re: Counter Rotating Propellers for Stunt
« Reply #60 on: April 25, 2019, 04:01:16 PM »
Archie,

Regarding video 78597:  You can't hand start it.  It's electric, and that's not how you start them.

Hope this helps.
The Jive Combat Team
Making combat and stunt great again

Offline Archie Adamisin

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Re: Counter Rotating Propellers for Stunt
« Reply #61 on: April 28, 2019, 10:04:11 AM »
Hi Archie,
Could you please provide some technical details regarding the contra system you are showing on youtube?
Specifically: the maximum continuous current, gear box ratio, weight and diameter and pitch of the props. used.

Thank you,
Matt Piatkowski

Matt,
 
Max continuous current is 50 amps.
Gear ratio 1:1
Weight as shown with props and spinners 10.5 oz.
Front propeller 10 x 5 APC
Rear propellor 10 x 5.8 Pusher APC

Archie Adamisin
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Offline Archie Adamisin

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Re: Counter Rotating Propellers for Stunt
« Reply #62 on: April 28, 2019, 10:06:09 AM »
Archie,

Regarding video 78597:  You can't hand start it.  It's electric, and that's not how you start them.

Hope this helps.

Howard,

Maybe if I found that glow igniter.  Dang, that's where  I screwed up.  Or I could have pushed the magic red button.  That always goes well.

Archie Adamisin
Archie Adamisin
Burlington, KY

Offline Archie Adamisin

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Re: Counter Rotating Propellers for Stunt
« Reply #63 on: April 28, 2019, 10:13:24 AM »
Hi TDM,
shows exactly the straight (spur) gears and their configuration used in "Polish Contra". The latest gear box in this contra has helical gears and should be quieter but it is prohibitively expensive.

Hi Vieira,
The "two motors contras" (http://www.maxxprod.com) are very reasonably priced. CR3516-1030 system seems to be well suited for F2B but the extensive flight testing is needed to prove it.

Thank you,
Matt

I think the concept of this Himax is great.  I have one.  It is a 3S setup.  It is a monstrous pull system.  I'm pretty sure my bench moved when I ran mine on the supplies props.  Need a big 3S pack.

Archie Adamisin
Archie Adamisin
Burlington, KY

Offline Matt Brown

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Re: Counter Rotating Propellers for Stunt
« Reply #64 on: May 01, 2019, 03:30:14 PM »
This thread got me thinking and looking on EBay. I ran across this unit and thought a smaller one could be built relatively easy compared to the polish unit. I like the simplicity of the gear/belt arrangement too.

Matt

Offline Chris Wilson

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Re: Counter Rotating Propellers for Stunt
« Reply #65 on: May 01, 2019, 11:18:17 PM »
I would like to see if counter rotation improve ducted fans enough to be viable.

In theory it should.
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Offline Matt Piatkowski

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Re: Counter Rotating Propellers for Stunt
« Reply #66 on: May 15, 2019, 12:13:00 AM »
Hello everybody,
The first of the two Himax CR3516-1030 systems has been flight tested by one of my colleagues in Poland without me being present. The system used two Spin66 ESC, one Igor's active timer and 3S 4000 mAh battery. 12x6 carbon composite two blade propellers were used. The RTF weight of the model was 2025 grams (71.5 oz.), wings span = 60" and the wings surface area with flaps = 690 in^2. The lines length = 64', eye-to-eye.

The tests were done in a hurry, without bothering to check the ground current and, unfortunately, one of the motors was burned in flight. The motors were mailed to the guy who specializes in rewinding and rewinded with thinner copper wire to get the Kv=500. I saw three flights using these motors and 6S 2700 mAh. Zippy battery. The ESC, timer and props were the same. This time the tests were successful and the quality of the pattern maneuvers - exceptional. Judging from the battery use after landing, the average in-flight current in each motor, with the ESC connected PARALLEL was no more than 13 Amps. The total average in-flight power was, therefore, about 625 Watts (2x13Ax24V). This calculation assumes the average voltage of the 6S battery to be 24 Volts. 625 Watts converts to 8-9 Watts/oz. in this model. Because every contra system generates more thrust in the direction of flight than a single prop systems, the plane, weighting 71.5 oz., flew easily every maneuver with exceptional stability.

More flight tests are planned in the next two weeks.

Regards,
M

Offline Brett Buck

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Re: Counter Rotating Propellers for Stunt
« Reply #67 on: May 15, 2019, 09:01:28 PM »
l. Because every contra system generates more thrust in the direction of flight than a single prop systems,

  Huh?

    Brett

Offline Paul Walker

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Re: Counter Rotating Propellers for Stunt
« Reply #68 on: May 15, 2019, 10:36:13 PM »
Because every contra system generates more thrust in the direction of flight than a single prop
Regards,
M
[/quote]

If it generates MORE thrust, wouldn't it fly faster thus requiring you to reduce the thrust to fly slower????

Offline Matt Piatkowski

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Re: Counter Rotating Propellers for Stunt
« Reply #69 on: May 16, 2019, 02:31:47 AM »
Yes, Paul. The plane with contra can fly slower than the plane with a single prop and still will have enough speed for the overhead maneuvers.
Reducing the thrust reduces the current and this is the Holy Grail of the entire exercise. Less current, less battery drain. Less battery drain - smaller capacity battery can be used. Smaller capacity - lighter battery.

Best Regards,
M

Offline Brett Buck

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Re: Counter Rotating Propellers for Stunt
« Reply #70 on: May 16, 2019, 04:15:43 AM »
Yes, Paul. The plane with contra can fly slower than the plane with a single prop and still will have enough speed for the overhead maneuvers.
Reducing the thrust reduces the current and this is the Holy Grail of the entire exercise. Less current, less battery drain. Less battery drain - smaller capacity battery can be used. Smaller capacity - lighter battery.


   I thought you said it *increased* the thrust - now it is *decreasing* the thrust?  And all to accomplish a small weight reduction in the battery? This weight reduction in the battery exceeds the additional weight of the gearbox or concentric shafts? And this is somehow the Holy Grail?

   I think you need to show math, and the numbers, because I am having a hard time understanding what you are saying.

      Brett


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