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Contra Rotating Propeller Drive for f3a 2m Pattern Planes

Old 10-11-2011, 03:16 AM
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Default RE: Contra Rotating Propeller Drive for f3a 2m Pattern Planes

Hi Brenner,

I`m active in the German f3A Circus. I got the contra from Ewald Trump. I`m testing the drive now(addiction from Delro)to get some experience for the next season. At first congratulations for the high mechancal quality of your system. I`m dealing with lots of CNC products every day and this is very good work for sure. I was lucky to manage some flights now and I realy feel comfortable with the system. I mounted it on a C50 14L. Due to this fact I have a question or concern. If you disassemble the gear of the C50 you see the main pinion on the shaft of the motor. This pinion fits in the back side of the gear box of the contra. The counterpart in the box does not have the same shape of this C50 pinion. Therefore my concern is that this C 50 main pinion (or even the loaded flank of this pinion ) will wear off due to the load which results from the load reversals during operation.
Does anybody has experience with that?
When I finished my testing I´ll install the contra in a mid rex biplane from oxai and will perform in the german championship next season. How is the supply with spare parts in general?

Christian
Old 10-11-2011, 06:27 AM
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Default RE: Contra Rotating Propeller Drive for f3a 2m Pattern Planes

Hey Christian,

I originally had this problem when I first ran my Drive, but I ran it dry without any lubrication. More recently I've been making sure to use grease at the spline interface, and I haven't noticed any wear.

Regardless though, any flank wear on the spline won't affect the operation of the Drive.

Brenner ...
Old 10-11-2011, 09:08 AM
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Default RE: Contra Rotating Propeller Drive for f3a 2m Pattern Planes

Hi Brenner,

wouldn`t it make sense (or is it possible)to desin the connection in that waythat the spline and the counterpart fit exactly to avoid any damages? The point is if the pinion at the c 50 is worn out you have to do a big service at the motor because ismounted fixto the shaft.

Christian

How is the availibilty of spare parts?
Old 10-11-2011, 09:59 AM
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Default RE: Contra Rotating Propeller Drive for f3a 2m Pattern Planes

Hey Christian,

Yes, you make some good points, but the problem that we have is that we need to accommodate both the Hacker C50 Competition motors, and the Neu f3a motors, and the splines are different for both of these.

We would like to design the system with a replaceable insert that can be swapped out but this would require us to change the size of the barrel OD of the pinion gear to make room for it, and this in turn would require us to change the number of teeth on the pinion gear, which means that we would have to upsize our ring gear, which means that the overall diameter of the gearbox would have to increase, which means that it wouldn't fit into the nose of most planes that use 82 mm spinners.

Anyhow, in the vernacular of consumer product design, it's a design issue that cascades across the entire system, affecting pretty much all the parts in the gearbox, resulting in our not being able to meet certain design requirements.

Anyhow, we're going to keep thinking about the problem, and with luck we'll find a way to do what you are asking.

Brenner ...
Old 10-11-2011, 12:11 PM
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Default RE: Contra Rotating Propeller Drive for f3a 2m Pattern Planes

Hi Christian,
I am flying an Oxai Ventura with the Contra.
I also have a Midrx Bp almost ready for it.
They are both very big airplanes at 87 to 90 dm\2 and 5000+g.
I am using the Neu motor for the extra power.
It is rated at 3Kw with a kv of 1300.
In the big biplanes it makes a real difference.
www.f3aunlimited.com sell it without the gearbox.
Brenner and Mike have been very good with parts and support.

Brian
Old 10-11-2011, 01:39 PM
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Default RE: Contra Rotating Propeller Drive for f3a 2m Pattern Planes

Yes, I forgot to mention about spare parts.

What we are doing is building parts in batches, depending on how many Contra Drives we project we will need, and how much money we have on hand to pay upfront CNC machining costs. (Right now it's the money that is limiting us ..)

Anyhow, when a batch of parts of manufactured, we don't build them all up into Drives. Instead we wait until we get orders, and then we build to order. This means that we have parts on hand until we finish using all the parts in the batch, and then we have enough money to kick off the next batch. So, this means that we don't expect to run out of parts before we make parts for our next batch, and consequently parts availability should always be good.

Brenner ...
Old 10-11-2011, 09:14 PM
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Default RE: Contra Rotating Propeller Drive for f3a 2m Pattern Planes

more power means more battery capa and this means more weight. In Gemany the style is very slow and constant. I hope that I do not need the extra power. Actualllly I fly a 4200 and only need 3000mA for the P13. How do you manage the CG of the mid rex with the contra. There is not much space for the battery.

Christian
Old 10-11-2011, 09:23 PM
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Default RE: Contra Rotating Propeller Drive for f3a 2m Pattern Planes

sounds as it is in the real life. What If I interested in a Proto of this Contra with a perfect fit to the C50?Actually Idesign my own plane (Proto should fly in the middle of2012). I`m able to react on a different diameter.
With the contra you have to redesign the nose anyway.

Christian
Old 10-12-2011, 12:32 AM
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Default RE: Contra Rotating Propeller Drive for f3a 2m Pattern Planes

ORIGINAL: Cross_link

more power means more battery capa and this means more weight. In Gemany the style is very slow and constant. I hope that I do not need the extra power. Actualllly I fly a 4200 and only need 3000mA for the P13. How do you manage the CG of the mid rex with the contra. There is not much space for the battery.

Christian
Hi Christian,
You have to check the Oxai recommended CG; I am not using it.
I have made a battery hatch by cutting the top of the fuz,, . It is a lot of work but it is the only way to get to a 'user friendly' model.
I use TP440O with the Neu.
The Hacker will work, but not well in the wind we get in Ireland.
The contra is a big 'prop' load and we found the Hacker made a lot of heat but the Neu runs cool - 45 to 50C.
I will try to get some photos at the week end if that is ok for you.

Brian
Old 10-12-2011, 04:50 AM
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Default RE: Contra Rotating Propeller Drive for f3a 2m Pattern Planes

Hi Brian,

I try to avoid cutting the top side of the fuz, because I want to sell the plane at the end of the season (I always do that). But I seriously think about getting me the Neu. Where do I get it and what kind of motor is it exactly. I´m not sure if I`ll manage the 5000g with this setup. Were is your CG? I won`t use the OXAI CG either!!

Christian
Old 10-12-2011, 05:17 AM
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Default RE: Contra Rotating Propeller Drive for f3a 2m Pattern Planes

Hi Christian,
You can fly slow/close in with the Neu also. The mAh usage will not increase. the difference is a lower throttle setting for the same speed and then the ability to fly across the top of the manoeuvres with complete authority.
www.f3aunlimited.com supply it without the gearbox.
The Oxai CG works out at 70mm back on the bottom wing.
25% MAC = 106mm on mine.
30% = 125mm.
The Ventura recommended is 128mm = 30% MAC.
I fly the Ventura at 120-122mm.
I will try the Midrex at 112mm at first- this weekend !.

Brian
Old 10-13-2011, 09:54 AM
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Default RE: Contra Rotating Propeller Drive for f3a 2m Pattern Planes

Hi,
Test
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Old 10-13-2011, 10:03 AM
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Default RE: Contra Rotating Propeller Drive for f3a 2m Pattern Planes

Can I have a shot?
Old 10-13-2011, 10:04 AM
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Default RE: Contra Rotating Propeller Drive for f3a 2m Pattern Planes

Hi,
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Old 10-13-2011, 10:05 AM
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Default RE: Contra Rotating Propeller Drive for f3a 2m Pattern Planes

Brian,

Great looking MidRex. Looking forward to your flight report.

Appears in your color scheme you requested OXAI to swap the white for yellow. Was there an extra fee for that?
Old 10-13-2011, 10:12 AM
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Default RE: Contra Rotating Propeller Drive for f3a 2m Pattern Planes

Hi,
Connection is real slow and can only upload one or two shots at at time ??
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Old 10-13-2011, 10:19 AM
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Default RE: Contra Rotating Propeller Drive for f3a 2m Pattern Planes

Hi Glen,
It is a long story, however to swap does not cost.
To change the pattern does.
I had them swap white to yellow, pink to red and dark blue to green.
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Old 10-13-2011, 10:27 AM
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Default RE: Contra Rotating Propeller Drive for f3a 2m Pattern Planes

Hi,
One step at a time !!?
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Old 10-13-2011, 10:34 AM
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Default RE: Contra Rotating Propeller Drive for f3a 2m Pattern Planes

Hi again,
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Old 10-13-2011, 10:44 AM
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Default RE: Contra Rotating Propeller Drive for f3a 2m Pattern Planes

HI,
Last of the day !
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Old 10-13-2011, 01:40 PM
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Default RE: Contra Rotating Propeller Drive for f3a 2m Pattern Planes

Brian, am I looking at an adjustable thrust line? If so can you show more details?

Jim

I guess not. Screws are to hold cowling on.
Old 10-13-2011, 04:17 PM
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Default RE: Contra Rotating Propeller Drive for f3a 2m Pattern Planes

Hi Jim,
Yes just to hold the chin cowl.
There was a flange/dowel/flange there.
These were lost when I cut back the front to remove the right thrust and to fit the contra. The Midrex takes a 75mm spinner and the contra is 82mm.
It is the exact same install as shown in post 272 here.
When I cut the top off I had to add stiffening to compensate.
The thrust line is easy to adjust.
For small adjustments to left/right up/down I simply move the rear support.
After that/in addition to that I shim the bobbins and move the rear mount.
It is a variation on Brenners original mount which allows the complete unit to be removed out through the front.
We did this to allow for quick interchange model to model.

Brian
Old 10-14-2011, 02:58 AM
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Default RE: Contra Rotating Propeller Drive for f3a 2m Pattern Planes

Superb job as usual Brian!

How did you keep the hatch shut lines so fine and how much repainting was involved?

Cheers,

Malcolm
Old 10-14-2011, 03:37 AM
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Default RE: Contra Rotating Propeller Drive for f3a 2m Pattern Planes

Hi Malcolm,
Thanks, I try to aspire to the standard I see on some Scottish models
I spent some time cutting it with X-scto blades, I used 3 or 4 new blades to keep a good edge/point.
I put down two lines of small fine line tape side by side - just touching each other and then cut between them.
The front end top red,orange,yellow,purple and clear were repainted.
I wrapped the purple down and underneath while darkening it towards the front to try to key to the drive.I masked outside the purple and worked in from there.The paint was applied it the order ; yellow,orange,red then purple.
I really love these contras and the least I can do for Brenner and Mike is 'package' them as nicely as possible.
They have/still do put in a lot of work to this and to us all. They really are great guys to work with.
So we must do our best in return - that's how I feel anyway.
Our new flying site is starting to take shape - you can see snippets in the photos.

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

The site looks superb Brian,

I wouldn't expect anything less!

Malcolm

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