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Old Apr 23, 2012, 06:05 AM
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Quote:
Originally Posted by Lantsov Alexey View Post
Vladimir thanks for the reply.
1. your bearing to press, then measure the resistance.
2. the gearbox is problems in the red zone.
Do the gearbox at the rear.
Alexey, also thanks for the reply.
1. I did not realize that necessary to press in the bearing and the main thing why?
2. With the gear i agree that you are right the kinematic scheme should be changed.

The new version of the kinematic scheme is shown below.
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Old Apr 23, 2012, 07:36 AM
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1. the working condition of the bearing without gaps.
Dense planting outside, compresses the bearing.
If the electrical contact is inadequate then will make brushes.

2. it is not difficult.
We must help each other.
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Old Apr 23, 2012, 09:17 AM
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Quote:
Originally Posted by Lantsov Alexey View Post
...
Dense planting outside, compresses the bearing.
If the electrical contact is inadequate then will make brushes.
...
Additional pressure on bearings by mounting the will never have a reliable contact, because in principle they are not intended to serve as the contact site.
Steel - a very poor conductor of electricity.
Moreover, the balls are in contact through the dielectric grease.

And in general.
Bearings - it is a finished product with certain properties from the manufacturer.
In the list of these properties no have a parameter on the quality of electrical contact.
And the manufacturer of bearings will never guarantee a good contact.
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Old Apr 23, 2012, 10:07 AM
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Vladimir thanks.
There are many options to make good electrical contact
Graphite lubricant.
Graphite washer.
Brushes.
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Old Apr 23, 2012, 12:24 PM
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Graphite also is also a very mediocre conductive material.
Graphite is primarily- resistive material and is not conductive.
He never belonged to a good conductor.
So he, too, can not provide a nice touch.
http://www.montag-electro.com/apparaty-34.html
http://sermir.narod.ru/lec/lect7.htm
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Old Apr 23, 2012, 01:53 PM
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I will reveal to you the secret.
Brushes collection engines are made from graphite.
For certain conditions in graphite is added to copper, coal, and many more.
http://www.alibaba.com/showroom/graphite-brush.html
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Old Apr 24, 2012, 02:56 AM
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It is unlikely that you will be able to open for me are secrets in the field of electrical engineering.

Let me remind that we are discussing here.
Obviously that not of the contact rotating node made of graphite-copper composite.
We are talking about steel bearings, which you want to use as a contact site.
I have shown you that when it rotates there full electrical contact termination.
These breaks do you offer to compensate for a graphite lubricant.

Let me tell you multi secrets.
1) Nobody no made the rotating contact components, based on material from the steel due to its poor conductivity.
2) The graphite lubricant is used mainly to improve the slip, not to improve the electrical contact.
3) The graphite lubricant is a mixture graphite, but not with best electrical conductivity material (copper, silver, etc.) but with dielectric (oil) which more worsen it and without this bad conducting properties.
4) Indeed, there are special conductive grease on the basis of very good conductors (not graphite), but they are designed to improve the quality of contact, but not for its replacement.

I propose to end the discussion no off topic.
I just wanted you to help...
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Old May 07, 2012, 12:05 PM
"Free" in Christ! #F3P
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I have a silly question:

Why don't people use coaxial for freestyle?

Free
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Old Aug 24, 2012, 03:31 AM
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I have not been very active here during the summer, but with the F3A season ending, it seems about time to move my focus to indoor stuff again...

About the single motor gearboxes discussed above. The basic problem of any contra is that since one of the props is behind the other, the rear prop needs to either spin a lot faster and/or have a higher pitch for the torques to be even roughly equal. If the rear prop is only working half as much as the front one, you will not get the full benefit from the contra system and the adverse effects of a single prop (torque, P-factor, spiral slipstream, gyroscopic precession) are only partially cancelled out. Just having two props spinning in opposite directions might be good enough for a scale plane, but for precision aerobatics I think we want more.

The simplest gearbox would turn both props at same RPM, you could make one with just 3 bevel gears. The problem is that the only thing you can play with to adjust the torque/power distribution between the props is the propeller pitch. With same RPM you need a lot more pitch on the rear. Also adjusting it is not very simple, you need to try various props to achieve a hopefully good enough compromise.

A similar system using spur gears, like Free suggested and shown in Vladimir’s drawing, would have the added benefit of allowing a lower gear ratio to be used for the rear prop, allowing it to spin faster. By experimenting with different gear ratios for front and rear, plus different pitch props you might again be able to reach a good enough compromise. Adjusting it precisely will not be easy though, since you need to play with the gear ratios and props.

With my geared dual motor system, the benefit is that you can further trim it for zero torque from the radio, by using one mixer to limit the top end on the motor driving the front prop. You do not have to change props or gear ratios, just a few clicks on the transmitter until satisfied. This ease of adjustment is one of the main reasons why I ended up with a dual motor system. Also the gearboxes, although there are two of them, are simple with only one stage and thus very good efficiency. On the downside is the need for a second speed controller and spare channel, but with the smallest ESC's weighting 0.7g and sub 2g receivers with 6 channels, I do not see that as a huge problem.

The one limitation/compromise is that you can only trim it at one static condition, like hover or a slow upline. It does not automatically adjust when the loading/speed etc changes. However with the narrow speed range of F3P planes, I think trimming it in the static condition is enough.

To do a proper single motor gearbox, it might be better to use a single planetary system like the F3A contras, the Contra-drive by Brenner Sharp (I’m using one in my Wind S Pro and I love it!) and the E-Factor system by Michael Ramel. In those the front prop is attached to the planet carrier and the rear prop to the ring gear, motor is driving the sun gear. That would have the additional benefit of self adjusting the rpm of the props, so the same power is absorbed by both props in all flight conditions. Not sure if that is easily achieved in the weight/size range F3P models require.

On the dual direct drive outrunner systems, Fabien Turpaud’s system is the lightest of that type I have seen and also the only one that swings reasonably sized props. The other ones, like those on Vladimir’s photos, are either heavy for F3P or swing tiny props.

On the co-runner concept, I’m happy to hear that several people are exploring that idea further. I’ve seen photos of at least two different prototypes, so I think we will see more of those in the future. That was the whole idea why I published the concept here, I did not have time to work on it further myself, so it’s better to have others working on it than just sitting on it.

Personally I really like the geared solution, so if I’m to make another version, I will most likely be based on the same concept (geared dual motors). Just need to make it even lighter and hopefully a bit quieter.

Free, I do not think the contra offers any benefit to freestyle. It’s about flying to music, not about ultimate precision.
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Old Aug 24, 2012, 10:01 AM
"Free" in Christ! #F3P
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Thanks, that was helpful!

Free
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Old Aug 24, 2012, 11:33 AM
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Kimmo,
Thank you for your information.
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Old Sep 04, 2012, 11:42 AM
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Have you seen this brushless glavak counter rotating motor?

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Old Sep 04, 2012, 04:08 PM
"Free" in Christ! #F3P
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Neat!

I only see one motor???

Is there a vid?

What does it weigh?

Thanks,

Free
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Old Sep 04, 2012, 04:25 PM
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netherlands
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Quote:
Originally Posted by Free View Post
Neat!

I only see one motor???

Is there a vid?

What does it weigh?

Thanks,

Free
it is only 1 motor, with 1 esc!! the bell and stator are counter rotating. inc the props and motormount 23 grams. Because there is no gearbox used is the motor very quiet.
for more info mail the builder and seller Sergej & Alex Glavak [Glavak@gmx.net]
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Old Sep 04, 2012, 04:39 PM
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That seems to be built after Kimmo Kaukoranta's Co-runner principle/idea. I bet this is one of the prototypes Kimmo is talking about above.

In my opinion, this is a very clever way to build a contra drive for F3P. The only weakness is that you need 3 brushes. If you can build the brushes to last, with low friction and weight in the same time, you've got a winner. One ESC, one motor and prop torque as well as all other negative effects of a single prop cancelled out just like the Brenner system does for F3A.
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