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Old May 14, 2011, 06:24 PM
Fly & Have Fun..Enjoy the Ride
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Quote:
Originally Posted by daddyrabbit1954 View Post
This is what I do to reverse a servo:

http://www.youtube.com/watch?v=hnd1zwouWV4

Alternatively, you can buy a reverse servo, or you can buy one of the servo reversing units that attaches between your servo and receiver. Option 1 is my favorite method as I don't need to order additional parts.
Exellent video, very well done...that's exactly what I've been explaining to lot's of folks asking about the reverse servo situations and to do it without reversers or buying a reverse servo
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Old May 14, 2011, 07:40 PM
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tx yes i did look on youtube and was the same video look easy i did try but lost 1 servo and make 2 work
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Old May 15, 2011, 01:49 PM
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Friends,

I intend to use 02 batteries 3S 5000 45C nano-tech in my Mig-29. What do you think? I must have a range of how many minutes?

Hug
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Old May 15, 2011, 04:13 PM
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hey guys.
been following this thread for a while.
but it's grown faster than i could keep up with.

i'm working on a second Mig.
my first was bone stock.
now, i want to go for all out speed.
will do all the necessary mods for the airframe and control surfaces to handle the load.

i am used to flying very high speed 90mm setups on 8S and 10S.
so i am hoping to get that kind of speed from this twin 70 mig.

questions i have are regarding power setups.
twin motors running off a single battery source VS one battery per motor.

initially, i was looking at an 8S setup.
but when i crunched the numbers, the components for the 8S setup would be quite expensive as i would need 2 HV ESCs.

From everyone's experience here, i have a couple questions:

1. what are the problems with running both motors off a single power source. IE: 2200kv motors on 6S (2x 3S 4000 in series). i'm concerned that the batteries would be overstressed from dumping so much energy into TWO motors simultaneously. Though i understand that a SERIES setup distributes power more evenly, so that the output on both motors is almost identical.

2. INDEPENDENT POWER SETUP: how reliable is this? I've had WW2 bombers set up this way, and have experience occasional motor failures. some resulted in total losses, others were recovered by gliding down.

my current battery stockpile is composed of 4S 4000 and 6S 4000.
i have ALOT of these.
so i'm hoping to come up with a power system using these batteries.
i honestly would prefer an 8S HV setup since i prefer lower amp draw.
and if the cost of getting two HV ESCs is lower than having to buy all new components for the "standard voltage" setup, then all would be well.

if i go with 4S singles, i was looking at HET fans and motors.
anyone try these in the MIG?
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Old May 15, 2011, 04:20 PM
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Ive tried HET ones .. they draw a little less than the wemos and rotate really fast
now if you go 1 batt per motor there is always that chance that 1 motor is more powerfulthan the other even a little bit so you got a (-) there as concern stability

now If I were you I would go with 2 HETs on 6S... you can' texpect close to 300km/h as your 90mm I suppose unless you go for the ultimate amp consuming hoffman magnetics The Beast on 5S and the HET fan.
that would be 137amps amp draw EACH!!!! and 2330watts EACH.
you will definetely need thrust tubes and maybe cheater holes to feed the fans with enough airflow
you will have a total of 274 amp draw what kind of battery can handle this thing?

so for me.. all out speed for this model is not that possible. A faster than stock is easy to do but don't expect too much. it's not that easy to do.
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Old May 15, 2011, 04:23 PM
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Hello there,
Quote:
Originally Posted by ale_nevesbr View Post
I intend to use 02 batteries 3S 5000 45C nano-tech in my Mig-29. What do you think? I must have a range of how many minutes?
One rough data point was posted by me in post number 3039 ("capacity usage was 700mAh per minute at 50% throttle"). In other words, with a 5.000mAh battery you might get up to 7 minutes if you coast around. But I had a different power system than the stock MiG, so numbers can't be extrapolated that easily.

Cheers,
Henrik
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Old May 15, 2011, 04:27 PM
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ofcourse now I think about it
2xHET6904
2x 2w-23 motors would be a nice choice

will be fast.. will sound fairly better than stock and will give some good flying times.
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Old May 15, 2011, 04:38 PM
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2W-23 2800kv on 4S?

whoa. i just looked at the specs on the HET site.
it will run on 5S.
but there is a warning saying not to run at WOT for more than 30s.
which is completely within reason actually.
but i do find it odd that HET says this 2800kv motor only draws 70A on 5S.
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Old May 15, 2011, 04:53 PM
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Quote:
Originally Posted by Brutikus View Post
now, i want to go for all out speed.
Why the MiG then? I don't think that the airframe will ever go fast. Just look at the thick profile of the wing and the slats. That is not a fast wing. If you want a fast wing, take the Su-47. It is a beast and only knows fast or faster, otherwise it falls out of the sky.

Apart of that, I wouldn't worry so much about using twin batteries, one for each ESC and motor. Even if you have a power differential in flight, the effect should not be so pronounced as in a regular twin, because the engines and thus the thrust vectors are so close to the central symmetry axis. That is not a lot of leverage, and if really warranted, you could use a gyro on the tv rudder for compensation.

Cheers,
Henrik
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Old May 15, 2011, 05:08 PM
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yes I meant 5S..

so you want something on 4s?
if yes the only good choices that will not break the bank are the 2w-20 het motor with the fan Or the new 68mm RCLander DPS systems.
I own both. both perform relly well
A guy a tthe meteor thread used the DPS system on 5S and at 80% throttle we dopplered him at 113mph but the passes were not good for dopplering .. so.. he might have broken the 200km/h barries and on full throttle (with high risk-personally I wouldn't do that even though cooling on those EDf units is very good) he might reach 240km/h
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Old May 15, 2011, 05:09 PM
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Quote:
Originally Posted by hklagges View Post
Why the MiG then? I don't think that the airframe will ever go fast. Just look at the thick profile of the wing and the slats. That is not a fast wing. If you want a fast wing, take the Su-47. It is a beast and only knows fast or faster, otherwise it falls out of the sky.

Apart of that, I wouldn't worry so much about using twin batteries, one for each ESC and motor. Even if you have a power differential in flight, the effect should not be so pronounced as in a regular twin, because the engines and thus the thrust vectors are so close to the central symmetry axis. That is not a lot of leverage, and if really warranted, you could use a gyro on the tv rudder for compensation.

Cheers,
Henrik
+1 on that point
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Old May 15, 2011, 05:51 PM
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i meant speed on this particular airframe.
i know this one is quite draggy.
but thanks for the input either way.

5S i would have to buy new batteries.
i'm actually leaning toward 6S but i doubt the frame can carry 2X 6S 4000.

i was also considering those Lander fans.
i have a few in 90mm.
love the construction and the sound.
i noticed that the have a 68mm and a 72mm version
is there a major performance difference between the two?
i might as well start another thread specifically for that discussion.
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Old May 15, 2011, 06:02 PM
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Originally Posted by Brutikus View Post
i'm actually leaning toward 6S but i doubt the frame can carry 2X 6S 4000.
The carrying of the weight will be less of a problem. You got lots of wing area, so your wing loading should be okay. The problem is where to put the batteries. If you put twin 6S in the front, you will be only be able to launch straight up , otherwise the nose will be too heavy. Also, the nose will break off if there is any hard landing or bump on the runway.

So you'll have to cut open the back of the airplane to make at least one extra battery compartment.

Cheers,
Henrik
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Old May 15, 2011, 06:19 PM
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yes.
planning to make a hatch to mount the batteries closer to the middle of the fuselage.

i know what you mean about landing that heavy.
i had a crazy 10S 4000 F16 90mm that had the front section separate on touchdown from the canopy forward.
and considering that plane had oleo struts, it was definitely a lesson learned.
i rebuilt it and sheeted the battery compartment with carbon fiber.
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Old May 16, 2011, 07:05 AM
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the new dps fans are great. the new dps 68mm is only at 4s. The older one had three versions 6, 4 and 3s
Now the new dps (you can tell by its blue colour) puts out 1.73kg of thrust on 4s
The 72mm one is on 6s and puts out 1.9kg of thrust at as low as 52amps. So you can have something below 4kg of thrust on 5000mah battery and some good flying time also
Not to mention the nice sound of them
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