Paddleducks
Old Yahoo Group => Yahoo Messages => Topic started by: Paulrjordan on June 14, 2005, 04:48:16 AM
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Here is a copy of a posting I put into Modelboats a few weeks ago. It
pretty well sums up my philosophy on electric motors for model boats
with a little "tongue in cheek!".
"I'm just going to repeat a comment I've made before about motors, and
this comes from having peered inside quite a few R/C boats and made
some pretty bad mistakes myself. I hope this won't arouse the wrath of
some of you Graupner, Robbe, Dumas and "whoever else sells commercial
motors for R/C boats" fans...but frankly I believe that many of the
motors available from Model Boat manufactuers are highly
inefficient...at least for many of the smaller models they're
recommended for.
In our fairly large Club in Victoria, BC, Canada, we have many
excellent modelers and "electronically adept" members..BUT start
asking questions about motor efficiency and you'd be surprised at the
number of BLANK stares you get back!!! I'm staggered by how few of our
members even own an AMMETER!!!
This results in a very strange phenomenon..I call it the "B-I-B
syndrome", a predominantly "male hang-up" known as "BIG is BEST".
Well, ask any woman you about "EFFICIENCY" and she'll tell you "it's
not the size of the poker but how you stoke the fire!" and when it
comes down to motors never was a truer word spoken. Seems alot of
fellahs go out to the Hobby store, plonk down a chunk of cash for a
shiny new Graupner, Dumas or Robbe motor and a thumping great gel cel,
get it home, plop it in the boat and never give it another thought!
See, many of them only run their boats for an hour anyway before they
have to go home to Sunday lunch!!!! Once a guy even tried to tell me
"the bigger the motor, the lower the current" ..say whaaaaa?
Ok.. ok..I know some of you are already itching to hit the reply
button and give me a scorching and, it's true, this is a bit of a
generalization..but you're getting my drift arent ya!!!
In MY opinion, model boat manufacturers' brand motors are often
overpowered for most small model boat applications and draw FAR too
much current for their efficiency! Shove an ammeter on a couple of
Graupner motors and pinch the shaft a little..woooo CHERNOBYL or
WHAT!!! It seems guys are driven by a comfort level that prompts them
to snag the biggest engine they can fit in the boat OR maybe what
LOOKS right in the boat!! Frankly I made this mistake THREE times
myself over motors bearing very well known European names at 30 - 40
dollars a piece! (Granted tugs are a little different as you need LOTS
of torque which can result in higher current draws...BUT unless you're
going to be towing a twenty foot model of a half sunken Exxon
Valdiz...you don't NEED a tugboat motor with the torque on a Cuisinart
to drive your little fishing trawler!)And Fast Electrics ?...well
that's simply revs and a subject I know ZIP about!
I've done dozens of motor current tests having plundered oodles of
engines from my kids' toys, computer and entertainment equipment and
even little dust buster vacuums. MOST of them (except the dustbusters)
run at far LESS current draw than the ones supplied well known Model
BOAT Manufacturer. I've heard people proudly proclaim they just went
out to the hobby store and bought a shiny new $40.00 motor and "it
only draws 4 AMPS!!!" Holy Miramachi!!!... I found little motors of
1/2" diameter drawing .04 Amps to drive models up to 36"..and they
only cost $1.00 each from an electronic surplus store!! (By the way,
you'd be surprised the size of boat you can drive from a tiny servo
motor as a main engine.)
In fact my own excellent hobby store in Victoria recently had a sale
on some tiny surplus micro motors they had bulk purchased ($2.00 each)
and they called me up to try one in a boat. Fantastic! these things
are torquey enough to drive a 24" model at scale. Diameter 1/2",
length 3/4", no load current draw .03 A and stalled at .35 A. These
were made for 12V but run fine at 6V or even 3V. They look absolutely
STUPID inside a boat, cos they're so small...but they DO THE JOB and
run hours and hours on a 4.8V home made "turbo pack" made up from old
AA size surplus cell phone batteries!
So some advice, for what it's worth (if you're still reading).. go
check out the local electronic surplus store and look at their bins of
surplus motors (specially ones with a little cooling fan on
them)..you'll recognize most of the well known electric motor
manufacturers with names ending in "ACHI,UCHI or ICHI" or other
Samurai sounding names). You see.. these people don't make engines for
model boats but for applications where low current draw/high torque
(and SIZE!) is often an issue and all at a fraction of the price you
pay for nicely packaged ones from Europe! Ohhh..and be VERY careful
buying used BOAT motors at Swap n' Shops.. you might just be buying
someone else's unwanted portable home heater..as I did!!
And if you really wanna have some fun? Ask a model boater what is the
motor(s) current draw in his boat under normal/stall load..and wait!!
I guarantee the FIRST sound out of his mouth be "Ummmm"!!! Also INSIST
on this info when you're buying from a store and ask them to SHOW you
the current draw on an ammeter, or at least make sure you can return
it when it starts to glow in the dark!
One final thought..If you don't own an ammeter (or multimeter), go out
and purchase one TODAY, 'coz without it you're living in a CAVE and
still GRUNTING!.. I sleep with one under my pillow and kiss her
lovingly goodnight..EVERY night! Azzif to allay my masculine
insecurity YET AGAIN, her little needle flickers and she whispers back
to me reassuringly "SIZE isn't EVERYTHING, babyyy" !!!!
PJ
PS This is in no way meant as derogatory of the fine Hobby Stores
throughout the world that sell model boat motors like the fine store
here in Victoria which still receives a good portion of my household
income..for everything EXCEPT model boat motors!!"