Electro UHU, Speed 600 Motor, Graupner Power Switch, 7-cell SCR (Black) 1700 mAH
Mike Luckham
I've finally finished building this ship, my first electric. Electro UHU is 2-meter,
dihedral, rudder & elevator only.
These are my experiences so far, in ground tests. Perhaps someone can make a comment,
and give me advice about motor run-times during actual flights.
The motor was broken in by running it in the direction of prop rotation for 1 hour using
4 Energizer D-cells (approx half the normal voltage).
New battery pack was charged once using a peak-detection charger [TEKIN BC100L]. I
thought the pack would charge in about 15 minutes, but after 20 minutes at 5 amp charge
rate the battery pack was quite warm so I took it off charge even though the charger
didn't shut itself off. I was monitoring the battery voltage via the terminals on
the front of the charger and using a digital voltmeter...10.48 Volts...should it
have been higher? TEKIN's instructions warned that new battery packs "might not have a
peak" and that charger might have to be turned off manually. I hope the charger will
work properly the next time.
I put the pack in the plane, stuck the business end (prop) in a safe direction, and
turned on the motor. Scared the heck out me, almost dropped the plane! I wasn't
expecting so much torque kick and such a lot of WIND! Good thing this wasn't a BIG
motor :-) !
Motor ran for about 5 minutes before the power switch did an auto-cutoff. I had thought
it would run longer (10 minutes)...maybe the battery pack wasn't fully charged after
all. The motor was quite hot, and also the battery pack although not too hot to hold in
my hand. I wouldn't want to try holding the motor :-) !
All this is normal, right? And I should do a few more charges/discharges on the battery
pack before the first flight, to get a longer flight time. What battery pack voltage
should I expect to see, at the point where the peak-detection charger turns itself off?
Since it is my first electric, I would like some advice on flying this plane. (I've
flown only gliders before...Gentle Lady, Paragon, Sagitta 3-meter, 2-meter scratch
built, 1-meter scratch built HLG).
How long should the motor runs be? Is it better to use 1-minute motor runs and thermal
around, or to use 3-minute motor runs to get more height. With shorter runs, I should
be able to climb 6-7 times...but how high? With longer runs, everything will be
hotter...is that good?
When climbing, what angle of attack is best to get good height? Is it better to move
FASTER and therefore generate more wing lift, or to move SLOWER and make the motor work
harder to pull the plane up?
The motor instructions mention a "stator ring", and that the motor will be more
efficient (run longer) with it. Can I make such a stator ring myself, and if so, what
does it look like?
Thanks for any assistance.
mike
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hi mike,
The figures you mention seem normal to me if you use the standard
graupner power kit: it is originaly meant for 6 cells.
don't worry tough your ok you will get more peps for climbing.
the additional rings are thin steel sheet rolled in a split tube that
force fits on the motor to increase the magnetic field .
If you use a 7.2v speed 600 I would recommend using it on 7 cells.
If you use the standard amp tin plated connector tamiya or graunper type
change them asap for the gold plated one of graupner or even better
sermos connetors(us made).
For the flight keep the uhu flat and let the speed build up it's a clean
ship that will climb better on its wings than on the motor.
Beware of laning no brake and it slick forsee a long flat approach or
learn to split "s" on the glide path .
very good bird but small so stay quit close and as mentioned quit fast
for a glider.
happy landings
Josef Hoelzl
Re: Electro UHU, Speed 600 Motor, Graupner Power Switch, 7-cell SCR
(Black) 1700 mAH
Hi,
A lot of guys in our club begun with an electric Uhu.
Use the 3:1 Graupner gear and a big prop and you have a very good
performance
But I think it will also work with direct drive.
I ask my club members if they have another ideas to help you.
Look at my electric homepage. (you will find some motor data of Graupner
motors)
http://members.aol.com/jhoelzl1/private/home.htm
Josef Hoelzl from germany
jbul...@icaen.uiowa.edu
In article <31A870...@rad.net.id>, Mike Luckham <luc...@rad.net.id>
writes:
If you are in the US or Canada try giving Jim Porter a call on the SIG Modelers
Hot LIne at 1-800-524-7805. Five minutes on the phone will answer more
questions than two days of net chase.
Max Feil
Mike Luckham (luc...@rad.net.id) writes:
> The motor was broken in by running it in the direction of prop rotation for 1 hour using
> 4 Energizer D-cells (approx half the normal voltage).
Is this a typo? 4 D cells will give you 6 volts, which is more than half
the nominal 8.4 voltage of a 7 cell NiCd pack. You should still be fine
though. I broke my motor in by letting 2 D cells run dead (no load).
> Motor ran for about 5 minutes before the power switch did an auto-cutoff. I had thought
> it would run longer (10 minutes)...maybe the battery pack wasn't fully charged after
> all. The motor was quite hot, and also the battery pack although not too hot to hold in
> my hand. I wouldn't want to try holding the motor :-) !
This sounds very normal. I get 3.5 to 4 minutes on my UHU with 6 cell 1400 SCR
Sanyo packs.
> Since it is my first electric, I would like some advice on flying this plane. (I've
> flown only gliders before...Gentle Lady, Paragon, Sagitta 3-meter, 2-meter scratch
> built, 1-meter scratch built HLG).
The UHU flies pretty fast compared to pure gliders. Land as gently as possible
because the battery pack's weight can do some damage.
> How long should the motor runs be? Is it better to use 1-minute motor runs and thermal
> around, or to use 3-minute motor runs to get more height. With shorter runs, I should
> be able to climb 6-7 times...but how high? With longer runs, everything will be
> hotter...is that good?
I usually climb until I hit lift, or for about 2 minutes (whichever comes
first). I like to leave some juice in the batteries since I use a BEC, i.e.
the rx and the motor run off the same pack.
> When climbing, what angle of attack is best to get good height? Is it better to move
> FASTER and therefore generate more wing lift, or to move SLOWER and make the motor work
> harder to pull the plane up?
The UHU is heavy and likes to fly fast, so keep it flat. On direct drive
the motor won't have much pull.
> The motor instructions mention a "stator ring", and that the motor will be more
> efficient (run longer) with it. Can I make such a stator ring myself, and if so, what
> does it look like?
I have one of these but don't use it due to the added weight. It does not
seem to make much difference.
I have been flying my Elektro-UHU since 1989 (this is its 8th season)
and have been very happy with it. It has allowed me to fly in locations
and test the air in places I could not otherwise have flown.
Regards,
Max
--
Max Feil
ah...@freenet.carleton.ca
Ottawa, Canada.