Motor hardware for Billing 1/20 USCG Life Boat?
Rick Russell
So, I'm about to start building the Billing Boats US Coast Guard life
boat, a 1/20 scale ship. It's about 30 inches long (73cm), twin
screws, ABS hull.
I'm wondering about the powerplant(s). Since it's a scale or
near-scale model, I have no interest in blasting it across the water
like a deep vee powerboat. But I do want reliable performance with
good torque; I may occasionally use this model as a tug to push other
boats to shore.
Since the two props are opposite handeness, I'll need two motors, one
forward and the other identical except reversed. I'm looking for
something in the 6V to 7.2V range. I've considered RC car motors like
Mabuchi 540s or airplane motors like the GP Thrustmaster 550s, but
both of those options seem like they would be way too fast and suck my
batteries dry in minutes.
Astroflight offers "scale" marine motors for 6-cell applications --
but good grief! Each motor is 15 ounces! That's nearly two pounds of
motors. And they are awfully expensive.
Any ideas? I've found some references to scale marine motors on
British sites, but I haven't a clue where I would find them
locally. LHS is no help, as usual.
Rick R.
--
Rick Russell * peripher...@miningco.com
* http://peripherals.miningco.com
MIKE L.
44' USCG Lifeboat (33" / wood hull)? When I built that boat in '81
I used 2 Pittman 6v motors that had the DUMAS name on them.
For control I used the FUTABA electronic speed control unit...it
was rather bulky, but you could use 2 controllers with it for
independent control of each motor! The rc unit was a FUTABA
6 channel radio. Made a batt. pack with 5 - 1.2v, 4 AH 'D' cells
and hid them under the well deck...could run for more than an
hour, but never did. Oh, my beam is 9"x 33" long! Lights too.
BTW, that boat is a 'displacement hull' type...you wouldn't run
it at high speed because the prototype can't get out of its own
way! I was on a 41' CG utility boat racing to a 'May Day' call and
we passed the 44' boat that left the CG station 10 mins. earlier;
we beat it to the scene...the 44 footer was used to tow the vessel
back to port! The 41' boats are of a 'semi displacement' type hull
and could get up on plane and cruise with no problem where the
44' boats can't! SLOW IS NO PROBLEM, IT'S PROTOTYPICAL!
I had that same problem with speed until I saw the prototype in
action...I'm satisfied with the model's speed running it is with the
transmission that DUMAS sold as part of the 'running hardware'
for the kit!
Mike L.
Rick Russell
MIKE L. <mikeydell@'nospam'.com> wrote:
> Is this the same or 'almost the same' model of the DUMAS
> 44' USCG Lifeboat (33" / wood hull)? When I built that boat in '81
It sounds similar. It's an ABS hull about 73cm long. Electric motors
for a 33" version should work fine in this 29" model.
> I used 2 Pittman 6v motors that had the DUMAS name on them.
Sounds like what I need!
> For control I used the FUTABA electronic speed control unit...it
> was rather bulky, but you could use 2 controllers with it for
> independent control of each motor!
That's pretty cool. I don't really need that level of control,
though. I figured I'd slave both motors off a Tekin Rebel speed
control; the low amp draw of slow motors should be easy for the Tekin
to handle.
> 6 channel radio. Made a batt. pack with 5 - 1.2v, 4 AH 'D' cells
I was going to start with 6 cell RC car packs, and I figured I'd
custom-build my own battery pack from D cells later on. Great minds
think alike!
> 44' boats can't! SLOW IS NO PROBLEM, IT'S PROTOTYPICAL!
Yeah, I realize that. Slow is what I want. The 44' lifeboat is
designed for towing power and seaworthiness, not speed. I find it
fascinating that the (actual) boat can actually completely capsize,
but has all equipment required to sustain life support for the people
below deck.
DaveB29
He has some nice scale motors that are really cheap. Hope this helps.
David
Pentti....@kiipula.fi
Rick Russell wrote in message <6rk5o2$h1d$1...@joe.rice.edu>...
>
>So, I'm about to start building the Billing Boats US Coast Guard life
>boat, a 1/20 scale ship. It's about 30 inches long (73cm), twin
>screws, ABS hull.
SNIP...
>Any ideas? I've found some references to scale marine motors on
>British sites, but I haven't a clue where I would find them
>locally. LHS is no help, as usual.
>
>Rick R.
>
>
I built one about 5 years ago, and have since been using it every summer.
My model uses twin Robbe Marine 12v motors, that look like somewhat
lengthened Speed 400:s, but are actually 5 pole designs.
No gearing, just direct drive, Robbe (frame rate, bipolar drive stage) ESC,
and
8 cell 4000mAh battery. I get around 80 minutes endurance on normal
scale-like cruise speed, and around 30-45 minutes full speed.
I did not use the rather dismal props and prop-axles that came with
the kit. Substituted them with home-made brass propellers (lotsa work)
and better axles.
My setup gives scale displacement withouth adding any ballast.
I am planning to throw away the rx battery and adding one or two cells to
the drive battery by using either a separate BEC or incorporating
it to a better high-frequency ESC.
Differential control to engines would be nice too, but it would
necessitate some quite fancy electronics.
-Pentti.
mac thomson
They suggested their #2004 motors and #2335 gear reduction unit. The gear
reducer also gears the two motors together so that both screws go the same
speed. Otherwise the faster motor would pull the boat to that direction. I
don't know if it will fit in the Billings model. These motors are lower rpm
than the 550 type motor.
Mac Thomson
Rick Russell wrote in message <6rk5o2$h1d$1...@joe.rice.edu>...
>
>So, I'm about to start building the Billing Boats US Coast Guard life
>boat, a 1/20 scale ship. It's about 30 inches long (73cm), twin
>screws, ABS hull.
>
>I'm wondering about the powerplant(s). Since it's a scale or
>near-scale model, I have no interest in blasting it across the water
>like a deep vee powerboat. But I do want reliable performance with
>good torque; I may occasionally use this model as a tug to push other
>boats to shore.
>
>Since the two props are opposite handeness, I'll need two motors, one
>forward and the other identical except reversed. I'm looking for
>something in the 6V to 7.2V range. I've considered RC car motors like
>Mabuchi 540s or airplane motors like the GP Thrustmaster 550s, but
>both of those options seem like they would be way too fast and suck my
>batteries dry in minutes.
>
>Astroflight offers "scale" marine motors for 6-cell applications --
>but good grief! Each motor is 15 ounces! That's nearly two pounds of
>motors. And they are awfully expensive.
>
>Any ideas? I've found some references to scale marine motors on
>British sites, but I haven't a clue where I would find them
>locally. LHS is no help, as usual.
>
>Rick R.
>
>
MIKE L.
>necessitate some quite fancy electronics.
>-Pentti.
Try the Futaba speed control...you can get independent control
of each motor with only 3 pieces (1 large unit and 2 small controller
units)! It's been a while for me, maybe now Futaba has streamlined
this control set-up.
Mike L.
Pentti....@kiipula.fi
imported. Anyway, being an incurable tinkerer, and electronics engineer
I will have a shot at it myself some day..
Besides, my guess is that this Futaba ESC is frame rate and
probably also voltage challenged (7.2 - 9.6v) so it would not suit
my purpose to eventually drive the boat with something like
12-13.2v. The current bipolar Robbe unit can take up to 14.4v.
-Pena.
MIKE L. wrote in message <01bdcfbd$7acd85e0$10324f0c@default>...
MIKE L.
It is the FP-MC4-P10 and can take a maximum input of 24 volts from
the drive batteries!
"One controller can control up to 2 power amplifiers" ...Futaba
The unit came with a Power Amplifier (67.0 x 72.0 x 41.5 mm),
a Controller (53.5 x 34.5 x 18.5 mm), a filter coil and a 20 amp
fused power cord.
It works like a charm running either 2 motors at once, or using
2 Power Amplifiers and controlling each motor individually!
Mike L.
Pentti....@kiipula.fi
-Pena.
MIKE L. wrote in message <01bdd14a$40239220$5cf34e0c@default>...