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Old Sep 20, 2013, 05:04 PM
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Originally Posted by asanovrus View Post
I think example with palm is not very correct, they touch the stick in very small surface so it's not much difference the direction
But the brushes, which contact the rolling log in the "palm" reference, have friction, further increased by the current it is passing, and the stability is much better "pulling" the brush away from its mounting, which puts the thin metal of the brush arm in tension.

Reverse rotation puts the brush arm in compression, and since it is very thin, might fold up on itself.
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Old Sep 20, 2013, 05:09 PM
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in practice, on v262 thread they showed that v262 has only 1 motor for all 4 positions and lifetime of both CW and CCW is the same. and those brushes are different: more surface, more friction. I heard that theory about wrong direction motors living less but it all was only assumption afaik
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Old Sep 20, 2013, 06:56 PM
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Different designs will perform differently. I have lots of car and airplane motors that can be run either way. That doesn't mean they all can.
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Old Sep 20, 2013, 10:09 PM
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It is a fact that the motor brush design dictates whether it will function properly in a given direction. Certain 7mm motors will be destroyed in a short time when running "backwards" for example. Other types with 90 degree tension run effectively in either direction.
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Old Sep 20, 2013, 11:03 PM
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Quote:
Originally Posted by asanovrus View Post
in practice, on v262 thread they showed that v262 has only 1 motor for all 4 positions and lifetime of both CW and CCW is the same. and those brushes are different: more surface, more friction. I heard that theory about wrong direction motors living less but it all was only assumption afaik
All I saw was motors dying left and right. Nothing scientific with real controls, and sample size was fairly small.

The different motor sizes have different brush designs. The 7mm motors have much more fragile brushes than the larger sizes, but the N50 motors seem to just overheat and disintegrate. The 8.5mm motors have lasted the longest for me. Looking at the different brush designs it looks like the 8.5mm brushes would be the best candidate if you did want to run them backwards.

Just looking at the brush design for the 7mm motors I can see that it isn't the best idea to run them backwards. Once hot, metal is much more flexible, and I'm sure those thin little brushes are a bit warm during flight. Mix that with a commuter spinning several 10's of thousands of revs per minute and it looks like a recipe for disaster to me.

Do as you wish, but I definitely do not recommend running a motor with reverse polarity if you can help it.
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Old Sep 23, 2013, 07:34 AM
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I have an idea to make four-bladed propeller for x4 from 2 two-bladed props, putting one to top of other (cutting ang gluing them to each other). Will it work?
I want my x4 to be more stable with my external FPV and to fly with weight more than 10 grams (15 g).

...or to try hubsan with Syma X3 blades...
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Old Sep 23, 2013, 07:58 AM
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Hi S,
It might work. I did a four blade version with a much larger 55cm diameter quad 8 years ago. The obvious problem is it makes the props heavier. The motors need lightweight props to quickly and properly respond to the flight controller speedup/slowdown commands. Changing the props this significantly with the mass of four blades, would also require a software PID change to get the best performance. The larger Syma X3 tri-props would require a geared system or larger motors to work on a quad. With all that said, go ahead and have fun and experiment
Cheers,
Jim
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Quote:
Originally Posted by Syavick View Post
I have an idea to make four-bladed propeller for x4 from 2 two-bladed props, putting one to top of other (cutting ang gluing them to each other). Will it work?
I want my x4 to be more stable with my external FPV and to fly with weight more than 10 grams (15 g).
...or to try hubsan with Syma X3 blades...
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Old Sep 23, 2013, 08:50 AM
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jesolins,

I have experimented with "X-Props" on larger electrics and nitro motors, and they work great!
1. Smaller diameter for the same thrust gives more ground clearance.
2. Smaller diameter gives less torque reaction (maybe not good with a quad, which needs this) for less throttle-roll coupling.
However there are some tradeoffs:
1. Column of air over control surfaces is narrow - not good for 3D planes, misses the ailerons.
2. Gives a strange whine noise, but this is good on my SupreTigre 90 powered F-18 (pusher)

With props in the 10" diameter, I would drop 1"-2" in diameter to give the same thrust. On my electrics with 7" props, I would drop to 6" to get the same thrust at the same current draw.

If you don't lower the diameter, or the pitch, you will draw lots more current, which (may) mean more thrust, but you know the rest of the trade-offs there...

If you want more thrust, maybe you could find a lower pitch prop, which will trade speed for thrust, something helpful for FPV.
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Old Sep 23, 2013, 11:00 AM
Tri-Quad-Hexa-Octo-copters!!
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Hi D,
My comments were specific to the multicopter application where the motor/prop combo has to follow the flight controller spedup/slowdown commands as closely as possible. Yes the four blades do make an interesting sound on the quads too. I can see how they would work fine for aircraft applications. I mainly tried them on my multicopters to see if prop blade redundancy and reliability was improved. The EPP props that we used back then were notorious for spontaneous inflight breaks on multicopters that were above 1kg AUW. The trade-offs were not positive between the added expense and poorer flight performance. For those reasons and the relative ease of balancing, I prefer two-bladed props on all my multicopters. Again, all that said, I do think experimentation from others to verify or improve is always a worthy thing
Thanks and Cheers,
Jim
Quadrocopter and Tricopter Info Mega Link Index
Quote:
Originally Posted by dbacon View Post
jesolins,

I have experimented with "X-Props" on larger electrics and nitro motors, and they work great!
1. Smaller diameter for the same thrust gives more ground clearance.
2. Smaller diameter gives less torque reaction (maybe not good with a quad, which needs this) for less throttle-roll coupling.
However there are some tradeoffs:
1. Column of air over control surfaces is narrow - not good for 3D planes, misses the ailerons.
2. Gives a strange whine noise, but this is good on my SupreTigre 90 powered F-18 (pusher)

With props in the 10" diameter, I would drop 1"-2" in diameter to give the same thrust. On my electrics with 7" props, I would drop to 6" to get the same thrust at the same current draw.

If you don't lower the diameter, or the pitch, you will draw lots more current, which (may) mean more thrust, but you know the rest of the trade-offs there...

If you want more thrust, maybe you could find a lower pitch prop, which will trade speed for thrust, something helpful for FPV.
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Old Sep 23, 2013, 11:12 AM
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imo the most efficient (lift per weight ratio) props are 2-blade props. 3-blade props are less efficient and used when need smaller diameter (like when prop guards are used). and more blades make prop more fragile.
there are so many different props to try (check MO's frankenquad thread) so I don't see reason to experiment with mods (I tried some prop mods and it was waste of time and props;-))
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Old Sep 23, 2013, 11:34 AM
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Tried to do one 4-bladed prop - air flow started to be much stronger, than with 2-bladed prop on same rpm.
It will be Hubsan 4x4 soon
Anyway, I'm doing it with my old props.

asanovrus: Hello from Sevastopol!
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Old Sep 23, 2013, 12:05 PM
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Quote:
Originally Posted by Syavick View Post
Tried to do one 4-bladed prop - air flow started to be much stronger, than with 2-bladed prop on same rpm.
It will be Hubsan 4x4 soon
Anyway, I'm doing it with my old props.

asanovrus: Hello from Sevastopol!
lol man only now noticed .
be careful, make sure motors don't get hot. even yd717 props make difference.
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Old Sep 23, 2013, 12:09 PM
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HI GUYS... I am wanting to purchase 650 dynam quad arf from xhelihas huge 11inch rotors...Can someone point me in the correct direction for all the setup info i will need..I have JR x9303 2.4 uses same rx's as spectrum radio's..I know i will need a gyro and a mother board...i think they come together...My only experience is with rc planes,car and fp heli's.and a week flying hubsan x4..any help is appreciated thax for all the help thus far....
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Old Sep 23, 2013, 12:57 PM
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Nothing changed with four-bladed props. Hubsan became heavier and flies at 5 cm from floor at full throttle. (upd: with FPV gear)
How can I increase Hubsan's power?
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Old Sep 23, 2013, 01:16 PM
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Syavick,

Sounds like it loaded the motors too much. Every motor has an optimum load and RPM, and a person can laboriously chart it all out to see if there is a better operating point. I suspect the Hubsan motor/prop combination has already been optimized. If this is true, any prop changes will be less than optimum. To modify the motors will (probably) take a larger ESC, and that is quite a change.

I am waiting for the Hubsan FPV, but I have had my money held by OoModels for a few months so far... To me, this is the easiest way, but there are lots and lots of bigger quads, and forums for them too. This forum doesn't have much on the other types.
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