Contra Rotating Propeller Drive for f3a 2m Pattern Planes
05-15-2013, 12:51 PM
#1126
Senior Member
RE: Contra Rotating Propeller Drive for f3a 2m Pattern Planes
ORIGINAL: MTK
What is less clear is where to place the TVC for the vertical stab. The standard single prop drives worked well with a TVC in yaw of around 0.8. The contra seems to require a TVC in yaw of well over 1. The easiest way to get that is with additional vertical area on the main fin, keeping all else the same. Fin shape also plays a role I believe: less chord and greater span,while increasing areaby 15% at least
What is less clear is where to place the TVC for the vertical stab. The standard single prop drives worked well with a TVC in yaw of around 0.8. The contra seems to require a TVC in yaw of well over 1. The easiest way to get that is with additional vertical area on the main fin, keeping all else the same. Fin shape also plays a role I believe: less chord and greater span,while increasing areaby 15% at least
Dean, did you include rudder area in your plank model?
05-19-2013, 01:18 PM
#1128
RE: Contra Rotating Propeller Drive for f3a 2m Pattern Planes
Interesting bits in this thread the past week....just reading it for the first time on a rainy Sunday.
My single prop Bravo in the foreground first flew in 2009, and immediately had a small vertical strake (about 2" high by 5" long) just behind the canopy. Before the end of 2009, it had the extension on the bottom of the rudder and ventral subfin on the fuse that extended about 8" forward of the rudder hingeline. At about that time, I also tried the fat rudder trailing edge...and immediately junked it....as others have said, there are far more efficient ways to add yaw stability (added side area is minimal drag compared to a fat trailing edge). In early 2011, the large TCan on the canopy was added which provided more knife edge power for the P11 Figure M, but also destabilized the airplane in yaw.....so I extended the subfin forward to the size seen in the picture.
My 2nd Bravo was identical to the first until 2011 when I added the Contra. I added the Contra and changed nothing else (save the added 3 oz of the Contra) and the #2 was actually divergent in yaw. After a lot of tinkering, the final configuration of bits that yield the knife edge power and yaw stability I like are what is shown in the picture. Compared to the single prop, ventral fin is longer, stab SFGs added, dorsal extension added. On the Contra, I very much prefer the wing SFGs vs the TCan - while they both yield similar knife edge power, the SFGs have slightly more yaw stability in turbulent air (I have no explanation for this). The Contra Bravo has ZERO mix for knife edge, and needs absolutely none, even in knife edge loops.
Both planes have a small bit of downthrust and a tiny bit of down elevator mix at low throttle. Neither have a throttle > rudder mix.
Regards,
My single prop Bravo in the foreground first flew in 2009, and immediately had a small vertical strake (about 2" high by 5" long) just behind the canopy. Before the end of 2009, it had the extension on the bottom of the rudder and ventral subfin on the fuse that extended about 8" forward of the rudder hingeline. At about that time, I also tried the fat rudder trailing edge...and immediately junked it....as others have said, there are far more efficient ways to add yaw stability (added side area is minimal drag compared to a fat trailing edge). In early 2011, the large TCan on the canopy was added which provided more knife edge power for the P11 Figure M, but also destabilized the airplane in yaw.....so I extended the subfin forward to the size seen in the picture.
My 2nd Bravo was identical to the first until 2011 when I added the Contra. I added the Contra and changed nothing else (save the added 3 oz of the Contra) and the #2 was actually divergent in yaw. After a lot of tinkering, the final configuration of bits that yield the knife edge power and yaw stability I like are what is shown in the picture. Compared to the single prop, ventral fin is longer, stab SFGs added, dorsal extension added. On the Contra, I very much prefer the wing SFGs vs the TCan - while they both yield similar knife edge power, the SFGs have slightly more yaw stability in turbulent air (I have no explanation for this). The Contra Bravo has ZERO mix for knife edge, and needs absolutely none, even in knife edge loops.
Both planes have a small bit of downthrust and a tiny bit of down elevator mix at low throttle. Neither have a throttle > rudder mix.
Regards,
05-21-2013, 06:02 AM
#1129
Thread Starter
RE: Contra Rotating Propeller Drive for f3a 2m Pattern Planes
We have a new set of props available.
What we have done is use the parametric solid model that we used to create the CAD models for our 22" series of props and used it to create a set of props that match the pitch and diameter of the APC Contra props. (see pictures..) These aren't clones, because the airfoils are different and the blade widths are different, but they are dimensionaly the same.
Mike molded the first set of props last Thursday, and I flew them in a contest at Muncie over the weekend, and I like them very much. They seem to work especially well with my Wind S Pro. The have better vertical performance than the APC props, and the throttle response seems to be more linear as well, which helps when using throttle management to match airspeed during large maneuvers.
They draw more mah's from my packs than APC props do. Energy draw is more in line with a set of 22x22 rear and 22x20 front props, but I don't consider this to be a bad thing because I don't like leaving performance on the table.
One of the biggest benefits is sound. There is no synchopating sound, and the overal noise is noticeably less than with our other carbon fiber props. In my view it's very similar to the noise that the APC props make.
Our next step is to make more props and get them into the hands of some top flyers who have a range of different planes that they can test them with.
Brenner ...
PS-> We had a Contra clean sweep at Muncie. 1st in f3a, 1st in masters, and 1st in Intermediate. (no Contra flying in Advanced..)
What we have done is use the parametric solid model that we used to create the CAD models for our 22" series of props and used it to create a set of props that match the pitch and diameter of the APC Contra props. (see pictures..) These aren't clones, because the airfoils are different and the blade widths are different, but they are dimensionaly the same.
Mike molded the first set of props last Thursday, and I flew them in a contest at Muncie over the weekend, and I like them very much. They seem to work especially well with my Wind S Pro. The have better vertical performance than the APC props, and the throttle response seems to be more linear as well, which helps when using throttle management to match airspeed during large maneuvers.
They draw more mah's from my packs than APC props do. Energy draw is more in line with a set of 22x22 rear and 22x20 front props, but I don't consider this to be a bad thing because I don't like leaving performance on the table.
One of the biggest benefits is sound. There is no synchopating sound, and the overal noise is noticeably less than with our other carbon fiber props. In my view it's very similar to the noise that the APC props make.
Our next step is to make more props and get them into the hands of some top flyers who have a range of different planes that they can test them with.
Brenner ...
PS-> We had a Contra clean sweep at Muncie. 1st in f3a, 1st in masters, and 1st in Intermediate. (no Contra flying in Advanced..)
05-22-2013, 04:59 PM
#1130
Thread Starter
RE: Contra Rotating Propeller Drive for f3a 2m Pattern Planes
Just recently I took my Drive apart to swap out the pinion gear insert, and so I had a chance to inspect the condition of my installation after about 100 flights or so. The results are shown in the attached pictures.
This Drive was greased with 3cc of Grease when the Drive was installed, and was regreased once, and after about 100 flights there was still plenty of grease inside the Drive to provide proper lubrication. However, as can be seen in these pictures, the outside of the Drive and the surrounding installation is still spotless, which to me is a good indicator that we are recommending the correct amount of grease.
We have have had some instances where grease has leaked out of the front of the Drive, and out of the rear of the gearcase, but in these cases we have been able to trace this back to me over greasing the Drive during assembly, causing grease to migrate past the cone that is inside of the rear hub behind the rear driveshaft bearing. (see picture ..)
This cone spins at 4000 rpm or so when the Drive runs, which causes any grease that migrates past the rear driveshaft bearing to fling off, and keep inside the Drive, but if grease gets past this cone, it can then migrate out of the Drive.
Brenner ...
This Drive was greased with 3cc of Grease when the Drive was installed, and was regreased once, and after about 100 flights there was still plenty of grease inside the Drive to provide proper lubrication. However, as can be seen in these pictures, the outside of the Drive and the surrounding installation is still spotless, which to me is a good indicator that we are recommending the correct amount of grease.
We have have had some instances where grease has leaked out of the front of the Drive, and out of the rear of the gearcase, but in these cases we have been able to trace this back to me over greasing the Drive during assembly, causing grease to migrate past the cone that is inside of the rear hub behind the rear driveshaft bearing. (see picture ..)
This cone spins at 4000 rpm or so when the Drive runs, which causes any grease that migrates past the rear driveshaft bearing to fling off, and keep inside the Drive, but if grease gets past this cone, it can then migrate out of the Drive.
Brenner ...
05-23-2013, 01:03 AM
#1131
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RE: Contra Rotating Propeller Drive for f3a 2m Pattern Planes
Hey guys
Brenner, thanks for these informations .
Regarding the props, true APC props are more noisy than carbon props on my plane.
Have you noticed too ?
I'd like to try these new carbon props when they will available.
Thanks to the guys who gave explanations about the design of an airplane with Contra Drive.
I incresead the area of the vertical stabilizer on my Integral (as shown on the attached picture) to see what will change.
Regards.
Brenner, thanks for these informations .
Regarding the props, true APC props are more noisy than carbon props on my plane.
Have you noticed too ?
I'd like to try these new carbon props when they will available.
Thanks to the guys who gave explanations about the design of an airplane with Contra Drive.
I incresead the area of the vertical stabilizer on my Integral (as shown on the attached picture) to see what will change.
Regards.
05-23-2013, 02:40 AM
#1132
Thread Starter
RE: Contra Rotating Propeller Drive for f3a 2m Pattern Planes
Hey Vincent,
If you get the chance you should consider trying this modification without the rudder strips as well to see if it can be used instead.
Brenner ...
If you get the chance you should consider trying this modification without the rudder strips as well to see if it can be used instead.
Brenner ...
05-23-2013, 02:18 PM
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RE: Contra Rotating Propeller Drive for f3a 2m Pattern Planes
Hi Brenner ,those props look nice. Can I assume they are similar weight as the normal carbon props we use?
05-23-2013, 02:20 PM
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RE: Contra Rotating Propeller Drive for f3a 2m Pattern Planes
ORIGINAL: servari
Hey guys
Brenner, thanks for these informations .
Regarding the props, true APC props are more noisy than carbon props on my plane.
Have you noticed too ?
I'd like to try these new carbon props when they will available.
Thanks to the guys who gave explanations about the design of an airplane with Contra Drive.
I incresead the area of the vertical stabilizer on my Integral (as shown on the attached picture) to see what will change.
Regards.
Hey guys
Brenner, thanks for these informations .
Regarding the props, true APC props are more noisy than carbon props on my plane.
Have you noticed too ?
I'd like to try these new carbon props when they will available.
Thanks to the guys who gave explanations about the design of an airplane with Contra Drive.
I incresead the area of the vertical stabilizer on my Integral (as shown on the attached picture) to see what will change.
Regards.
Cheers,
Jason.
06-04-2013, 01:32 PM
#1138
RE: Contra Rotating Propeller Drive for f3a 2m Pattern Planes
Hi Brenner,
Was at an open international in Kent - UK at the weekend.
Peter Hasse was there also.
His model is very interesting. It is completely symmetrical - side to side and top to bottom - so his desire for a contra system.
His contra is based on the Pletty Advance, with his own being a shortened version of the motor to meet his needs.
A simple (ish) gearing and belt arrangement is used to drive the props. Both props are at motor speed - one direct and the other via two side by side and 1 to 1 gears. The 2nd gear ,now reversed, then drives the 2nd shaft/prop via a belt again 1 to 1 ratio.
It is a bit like the one we saw in Austria, pictured early on in this thread, but for the gearing ratio.
There is no differential/power sharing.
It is made as lightly as possible - maybe 120g w/o props, spinners and nuts - though these are quite light.
It has plenty of power and the model is huge.
The front prop is 19x14 2 blade and the rear is 18x15.5 either 2 blade or 3 - when 3 it is 3 x 18x15.5 !!. He said this is a bit too much load for the motor.
In the air the noise is mostly motor and gear box. There is a low level syncopating prop sound.
The props have those little tiplets on. They are very fine tapering in section thickness from 1/2 the tip thickness at the point they diverge to almost 0 at the tip. They bend very easily and at the tip as easily as a sheet of fine paper. Hard to see how they retain shape especially from a centrifugal point of view - perhaps the taper does this.
The guys using these paddles c/w tiplets on Petty's also had very good performance. With a wind blowing at from 10 to 25 Kph directly in all that could be heard from the single prop variants was motor noise - super quiet.
There were several magazine columnists there and at lunch on the 2nd day one of them was at our table when he took a call from his editor.
Part of what he said in his chat , and I quote, was ; ' there are 31 pilots here and only two of them are using IC - and get this; there are 6 contras 5 of which are that guy Brenner's '.
Brian
Was at an open international in Kent - UK at the weekend.
Peter Hasse was there also.
His model is very interesting. It is completely symmetrical - side to side and top to bottom - so his desire for a contra system.
His contra is based on the Pletty Advance, with his own being a shortened version of the motor to meet his needs.
A simple (ish) gearing and belt arrangement is used to drive the props. Both props are at motor speed - one direct and the other via two side by side and 1 to 1 gears. The 2nd gear ,now reversed, then drives the 2nd shaft/prop via a belt again 1 to 1 ratio.
It is a bit like the one we saw in Austria, pictured early on in this thread, but for the gearing ratio.
There is no differential/power sharing.
It is made as lightly as possible - maybe 120g w/o props, spinners and nuts - though these are quite light.
It has plenty of power and the model is huge.
The front prop is 19x14 2 blade and the rear is 18x15.5 either 2 blade or 3 - when 3 it is 3 x 18x15.5 !!. He said this is a bit too much load for the motor.
In the air the noise is mostly motor and gear box. There is a low level syncopating prop sound.
The props have those little tiplets on. They are very fine tapering in section thickness from 1/2 the tip thickness at the point they diverge to almost 0 at the tip. They bend very easily and at the tip as easily as a sheet of fine paper. Hard to see how they retain shape especially from a centrifugal point of view - perhaps the taper does this.
The guys using these paddles c/w tiplets on Petty's also had very good performance. With a wind blowing at from 10 to 25 Kph directly in all that could be heard from the single prop variants was motor noise - super quiet.
There were several magazine columnists there and at lunch on the 2nd day one of them was at our table when he took a call from his editor.
Part of what he said in his chat , and I quote, was ; ' there are 31 pilots here and only two of them are using IC - and get this; there are 6 contras 5 of which are that guy Brenner's '.
Brian
06-04-2013, 06:51 PM
#1139
Thread Starter
RE: Contra Rotating Propeller Drive for f3a 2m Pattern Planes
Hey Brian,
Excellent! I'm very glad to see so many Contra Drives in one place. I think this ties that record as far as I know. (We had six Contras at one constest here in the American Midwest..)
I've been flying our new APC size carbon fiber props, and so far I am very pleased with them. They have similar performance to a 22x22 rear with a 22x20 front set of props, but they are as least as quiet as the APC plastic props. Also, there is no synchopation sound at all to speak of.
I've won two contests in a row with them, and between myself and Mike, we have a record of 11-6 for rounds won-lost.
We haven't had a chance to measure the sound on the ground with a sound meter yet, but as far as sound in the air is concerned, a Contra Drive with these props isn't any different from an inrunner single prop setup.
Peter's Drive sounds very interesting. Based on a the weights you quote, I'm thinking that the weight of his system should come out close to what our unit weighs, but it's hard to know for sure without knowing the weights of the other components in the system.
Are Peter's gears exposed, or enclosed? I'm thinking that they probably should be enclosed to avoid grease getting flung onto the inside of the plane, and also to keep the gear mesh noise down.
Brenner...
Excellent! I'm very glad to see so many Contra Drives in one place. I think this ties that record as far as I know. (We had six Contras at one constest here in the American Midwest..)
I've been flying our new APC size carbon fiber props, and so far I am very pleased with them. They have similar performance to a 22x22 rear with a 22x20 front set of props, but they are as least as quiet as the APC plastic props. Also, there is no synchopation sound at all to speak of.
I've won two contests in a row with them, and between myself and Mike, we have a record of 11-6 for rounds won-lost.
We haven't had a chance to measure the sound on the ground with a sound meter yet, but as far as sound in the air is concerned, a Contra Drive with these props isn't any different from an inrunner single prop setup.
Peter's Drive sounds very interesting. Based on a the weights you quote, I'm thinking that the weight of his system should come out close to what our unit weighs, but it's hard to know for sure without knowing the weights of the other components in the system.
Are Peter's gears exposed, or enclosed? I'm thinking that they probably should be enclosed to avoid grease getting flung onto the inside of the plane, and also to keep the gear mesh noise down.
Brenner...
06-04-2013, 06:58 PM
#1140
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RE: Contra Rotating Propeller Drive for f3a 2m Pattern Planes
Hi Brenner,
Peter's drive looks to be open to me. I'm friends with him on FB and he said his drive meets the 94dB limit by 10dB....
I'll post a picture from FB. I'm sure he won't mind. Seems to be another very nice piece of Engineering.
Cheers,
Jason.
Peter's drive looks to be open to me. I'm friends with him on FB and he said his drive meets the 94dB limit by 10dB....
I'll post a picture from FB. I'm sure he won't mind. Seems to be another very nice piece of Engineering.
Cheers,
Jason.
06-05-2013, 12:10 AM
#1141
RE: Contra Rotating Propeller Drive for f3a 2m Pattern Planes
Hi Brenner,
As Jason has shown they are open.
No lube is used - just a plastic to metal gear then metal to belt to metal.
I'm not sure of the 'plastic' type but this is how most model heli's are done. He is happy with life span.
I think his is probably a bit heavier. His spinners are a little lighter as the rear one is carbon and then the front prop goes directly on the shaft (so no middle piece) with the front spinner being the retaining nut and front cone.
So he has a little less weight in in spinners and props say 25g but has a 580 g motor + 120g (approx) gear box.
I did not do a like for like comparison with him as he was very open and informative. I did not want to give the impression in any way of being into a p*****g contest.
I should have said in the earlier post that Peter is a very interesting guy but above all he is just a wonderful character. One just has to admire his innovation but he is mostly in it for the fun - he just loves to have a laugh.
We were not noise tested but these paddles c/w winglets are quiet. The single prop ones ,while in the air, sounded like a motor on a bench run without any prop.
Brian
As Jason has shown they are open.
No lube is used - just a plastic to metal gear then metal to belt to metal.
I'm not sure of the 'plastic' type but this is how most model heli's are done. He is happy with life span.
I think his is probably a bit heavier. His spinners are a little lighter as the rear one is carbon and then the front prop goes directly on the shaft (so no middle piece) with the front spinner being the retaining nut and front cone.
So he has a little less weight in in spinners and props say 25g but has a 580 g motor + 120g (approx) gear box.
I did not do a like for like comparison with him as he was very open and informative. I did not want to give the impression in any way of being into a p*****g contest.
I should have said in the earlier post that Peter is a very interesting guy but above all he is just a wonderful character. One just has to admire his innovation but he is mostly in it for the fun - he just loves to have a laugh.
We were not noise tested but these paddles c/w winglets are quiet. The single prop ones ,while in the air, sounded like a motor on a bench run without any prop.
Brian
06-05-2013, 09:18 AM
#1142
RE: Contra Rotating Propeller Drive for f3a 2m Pattern Planes
Hi,
Was sent this by a friend.
I'm posting it here as his motor choice is interesting.
I can only assume that he has made this choice for the low to mid range torque the motor gives.
Apparently this is a glow converted to electric so this may at least be a factor in the choice.
I think this is relevant to those considering the contra as an option.
Anyway here it is.
Was sent this by a friend.
I'm posting it here as his motor choice is interesting.
I can only assume that he has made this choice for the low to mid range torque the motor gives.
Apparently this is a glow converted to electric so this may at least be a factor in the choice.
I think this is relevant to those considering the contra as an option.
Anyway here it is.
06-06-2013, 10:38 AM
#1144
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RE: Contra Rotating Propeller Drive for f3a 2m Pattern Planes
ORIGINAL: Brenner
Peter's Drive sounds very interesting. Based on a the weights you quote, I'm thinking that the weight of his system should come out close to what our unit weighs, but it's hard to know for sure without knowing the weights of the other components in the system.
Peter's Drive sounds very interesting. Based on a the weights you quote, I'm thinking that the weight of his system should come out close to what our unit weighs, but it's hard to know for sure without knowing the weights of the other components in the system.
06-06-2013, 11:48 AM
#1145
Thread Starter
RE: Contra Rotating Propeller Drive for f3a 2m Pattern Planes
Not a bad weight.
Ours is about 770g with a Nue f3a motor, and not including motor mount hardware.
Brenner ...
Ours is about 770g with a Nue f3a motor, and not including motor mount hardware.
Brenner ...
06-09-2013, 08:55 PM
#1146
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RE: Contra Rotating Propeller Drive for f3a 2m Pattern Planes
Jason,
Thanks for posting that pic. I love my Pletty Advance. I have a Neu but have not flown it. I was watching Tony fly his Episode with his contra. He is really flying better than I have seen him ever fly. Pretty impressed with his setup and countless hours of work on his flying.
I would really be interested in a Pletty contra. Hope that comes out somewhere at some point. Cheaply I may add. haha
Not trying to hack Brenners thread/work. My hats off to him for his awesome design. Watching Tony makes me want one.
Chris
Thanks for posting that pic. I love my Pletty Advance. I have a Neu but have not flown it. I was watching Tony fly his Episode with his contra. He is really flying better than I have seen him ever fly. Pretty impressed with his setup and countless hours of work on his flying.
I would really be interested in a Pletty contra. Hope that comes out somewhere at some point. Cheaply I may add. haha
Not trying to hack Brenners thread/work. My hats off to him for his awesome design. Watching Tony makes me want one.
Chris
06-10-2013, 02:54 AM
#1148
Thread Starter
RE: Contra Rotating Propeller Drive for f3a 2m Pattern Planes
I think the inrunner / outrunner controversy is a little mute when it comes to the Contra Drive because both motors are going to need a gearbox of some kind.
Brenner ...
Brenner ...
06-10-2013, 07:24 AM
#1149
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RE: Contra Rotating Propeller Drive for f3a 2m Pattern Planes
With the Pletty being an inrunner, maybe that makes it the easiest to build a gearbox setup for with the bolt pattern on the rront of the motor. I figured someone at some point would come up with something. Although I know it is a huge cost of time and money, there are a ton of Advance motors in use. And while yes, we use them for their ease of use and great power, I would think a contra gearbox would sell well.
Nice work Brenner. I dont get to see any contras usually, so always great to see Tony fly his. Your setup is really a work of art.
Jason, I will try to look Peter up. Thx
Chris
Nice work Brenner. I dont get to see any contras usually, so always great to see Tony fly his. Your setup is really a work of art.
Jason, I will try to look Peter up. Thx
Chris
06-11-2013, 02:30 AM
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RE: Contra Rotating Propeller Drive for f3a 2m Pattern Planes
ORIGINAL: Jason Arnold
That is the modification I was talking about! Will be very interesting to see your results.
Cheers,
Jason.
ORIGINAL: servari
Hey guys
Brenner, thanks for these informations .
Regarding the props, true APC props are more noisy than carbon props on my plane.
Have you noticed too ?
I'd like to try these new carbon props when they will available.
Thanks to the guys who gave explanations about the design of an airplane with Contra Drive.
I incresead the area of the vertical stabilizer on my Integral (as shown on the attached picture) to see what will change.
Regards.
Hey guys
Brenner, thanks for these informations .
Regarding the props, true APC props are more noisy than carbon props on my plane.
Have you noticed too ?
I'd like to try these new carbon props when they will available.
Thanks to the guys who gave explanations about the design of an airplane with Contra Drive.
I incresead the area of the vertical stabilizer on my Integral (as shown on the attached picture) to see what will change.
Regards.
Cheers,
Jason.
Increasing vertical fin area doesn't give any good result.
Knife edge requires a lot more travel's servos, then more drag.
In knife edhe the wings tends to flat back. The trend is very strong.
Rolls are barrel.
Humpty bump and spin more difficult too.
I removed this part. I'm going to add a little bottom area as Tony said just before the tail wheel . I have no other place.
Vincent ....
