I was out at the schoolyard some time ago flying the Rare Bear with an IPS
DX-A setup and two Lipo cells. It was pretty blustery and overcast, and I
was trying to get some altitude - I kept it full throttle all the way up,
and it had to fight to get there.
After that, I just shut down the throttle and let it come down in a nice,
long glide. Near the ground, I went to apply some throttle again, and
noticed the prop wasn't spinning! I managed to get a nice landing in, but
the motor never turned under power again. I could turn it with the prop,
but it was definitely stiffer.
So, when I put the new motor in, I decided to check the temperature after
some minutes of flying the other day. It was too hot to touch, although
since then I've given this one a workout too, and it hasn't siezed yet.
Is it normal for these little motors to get that hot? This is the stock
setup, except for the battery pack (7.4 lipo versus 7.2 Ni-something). I
did recently switch from a 750 E-Tec to a 730 Thunder Power.
Great little plane, though!
A few of us are just getting started on pylon racing with the Fan-Tastic AT-6
which was designed by the same guys as the Rare Bear. Mine also has the DX-A
power unit and I'm flying it with a Etech 700 two cell pack. We are using the
GWS 9x7 slow flyer props which provide decent speed and the power system seems
to handle this well. What are you using for a prop? You may need to prop down
some to decrease the load. Try reducing either the prop diameter or pitch
somewhat. The Rare Bear should fly well on the 9 x 7.
Keep in mind that GWS recommends a 150 mah 7.2 volt battery for this motor.
Perhaps their logic is that the motor will get a chance to cool after every 150
mah of fuel consumption.
I've gotten over 70 hours out of one of these $9.00 motors in another
application (slow flyer). But I don't expect that kind of life in a warbird
racer. The plane flies for at least 30 minutes on the Etech pack, but I stop
every 7 or 8 minutes to let the motor cool.
I suspect one mistake was to just shut down after a hard work out. I would
have run at low throttle for a few minutes to help cool the thing down.
Keep thing circulating so to speak. Also, I do hope you have adequate
cooling holes for the motor!
I bet you're right Mike - the plane's performance on the LiPo's is
surprisingly greater than on the NiMH's (attributable to the .2 volts?), and
I have flown for twenty solid minutes at a stretch some days. The day I
seized the motor I was fighting the wind exceptionally hard, and trying to
reach the cloud base - which I believe I did!
I'm using the supplied three-blade, which, I believe is a 9x7, but maybe
going to a two-blade would lighten the load on the motor.
Pylon racing! I'll bet that's a blast, particulary with Bearcats and
Texans! Is this indoor or out?
I think you're right - had I let it idle, it may have cooled in the "moving"
position - when I disassembled the motor (post-mortem, you know) the end-cap
plastic around the bearing was melted and wallowed out, not to mention all
the metallic flakes that appeared inside the can.
That's a bit of a "design flaw" with this model - the spinner meets up
almost exactly with the cowl and the fuse behind the firewall is pretty much
airtight - there is NO AIR moving around inside this plane! I may have to
put a scoop to the side of the cowl and cut an exit hole in the fuse
Does GWS make a heat sink for this class motor? if so, might want to
add one, assuming that you have some decent airflow around the motor to
carry the heat away from the sink!! The small GWS motors are very
sensitive to heat so you must provide adequate cooling .
A friend has one of the Fantastic Models AT-6's. Can't wait for him to
get it together.
The performance increase was probably not due to the negligable increase in
voltage, but rather the lipoly's ability to put out the amperage required by
the motor. These things need cells that can reliably put out 2 amps over the
complete discharge cycle to get full power. That takes a pretty big nimh pack
(relative to this tiny airplane). We have been trying to settle on a
non-lipoly cell (recent AMA terror alert scared off some club members) for the
racing events and found that 160 mah nimh cells were no where near up to the
job. Going up to eight of the 160 cells (9.6 volts nominal) still couldn't get
performance anywhere near the performance of the 700 mah, 7.4 volt lipolies.
Next experiments will be with (6) 150 mah nicads and (7) 300 mah nimh cells.
Track down a GWS heatsink as another poster suggested. Limit full throttle runs
with the 3 blade prop, or get the two blade prop.
We are racing outdoors. It sure is a hoot to see a group of these things
rounding a pylon! It is also fairly easy to convince others to make the meager
investment to join in after they have seen the spectacle.