Motor Costs Comparison

[John Pavlick]

Here are my thoughts on electrics:

Good points:

1. They are VERY quiet. This is a good thing. I've never heard of someone
losing a flying site because the planes were too quiet.

2. They are clean. The airframe will last longer because there's no danger
of being fuel soaked. Electrics are more "politically correct" in that they
don't pollute the air (although the energy required to charge the batteries
my come from something that does), and most of the new batteries are safe
when disposed of properly (to the best of my knowledge).

3. They produce less vibration, even when the motor is mounted directly to
the airframe.

4. Modern brushless motors have as much usable power as glow motors. When
properly matched to the airframe, an electric motor feels almost like a glow
motor.

5. They are easier to fit with a gear drive. This allows a wider range of
props that may be used.

6. Brushless motors require very little maintenance.

7. The C.G. doesn't change as the battery discharges.

8. They are easy to start.


Bad points:

1. An electric power system for large airplanes is VERY expensive. You can
buy a lot of glow fuel for the cost of a few battery packs. Batteries are
reusable, but they don't last indefinitely.

2. Power system design is much more critical. Props, gear ratios and current
draw must be considered very carefully.

3. Batteries must be charged. This takes a long time compared to how fast
they discharge. Owning a lot of battery packs merely delays the inevitable
truth: If it takes 10 times longer to charge than discharge, eventually you
will end up waiting for something to charge.

4. With LiPO's the energy density is fairly high (capacity wise) but it
normally takes quite a few packs in parallel in order to handle the required
current loads.

5. LiPO's must be handled with care. I don't need to elaborate on this one
although I personally don't think they're DANGEROUS. People are more
dangerous.

6. High output electric power systems are relatively heavy, although this is
improving at a rapid rate.


To sum things up - I fly glow and electric. I like them both. I have a few
S400 planes that fly very fast and track very well. I also have a few slow /
park flyers that are great when the air is calm. Small electrics are great.
Most of the time, however, I prefer glow motors. Mostly because of cost and
ease of use. A .40 glow motor costs $50.00 (used) to $100.00. A brushless
motor and battery that provides equivalent power could easily cost 3 times
as much. I don't like to wait for batteries to charge. I hated it when I
raced R/C cars and I hate it even more now. I don't mind wiping the slime
off of my plane at the end of the day. I do believe electrics may be the way
of the future. The key word is future. At the present time, I think the best
bang-for-your-buck comes from the glow stuff. There's a lot of energy stored
in dead Dinosaurs, and we pretty much perfected how to extract it in the
'70s. If money is not an object and you want to be a pioneer then fly 2
meter electrics. I think I'll wait until technology catches up with our
expectations.

John Pavlick
http://www.idseng.com

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