Paddleducks
Old Yahoo Group => Yahoo Messages => Topic started by: Edward Matthews on June 14, 2005, 05:11:00 AM
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Hi all,
My model of the Forceful had it's first trials on water today.... And
it was a little disappointing :-(
I had the model running on 6 volts which seemed fine out of the
water, but it was way underpowered with the paddles actually having
to work in water.... So I put it on 12 volts and that certainly gave
enough power, but upset the trim of the model too much, since the
batteries sit in front of the paddles, it looked like a submarine
about to dive! :-(
I also had a problem with my gear drive system, one of the paddles
works fine (they are independently controlled), but the other isn't
meshing correctly which again only showed up when the paddles were
under load with the boat in the water :-(
I'm undecided wether to play around with my gear drive to get all the
faults ironed out, or switch to a belt drive system.... The gear
drive can be made to work, but because of the ratios it would require
12 volts to operate and the boat simply cannot take the weight unless
I can find a lighter 12 volt jell cell (or maybe change to nicads) -
Whereas the belt drive wouldn't be so highly geared and would
probably work okay on 6 volts.... Ho hum, decisions decisions...
I also found that the model (like all paddlers I've ever seen in
model sizes, and probably the full size vessels too?) is incredibly
sensitive to balance port and starboard.
Anyway, I did promise a report on the first sailing so here it is...
Once I've decided which way to go I'll post further updates with my
progress.
Regards
Eddy
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Thanks for first report Eddie - sort of typifies what we are talking about
in learning by each others mistakes - PJ has written & posted some very
basic but very useful text on matters like this
Six months ago during early construction (hull of PS Decoy) in the bath I
quickly realised she needed a dramatic weight reduction so I re-looked at
batteries
I found my 12V 7 amp/H could be substituted with a 12V 3.5amp/H battery
which was literally 60% of the size & but came in at 50% weight (however
since have found alternate ways to reduce weight & maintain the original 7
amp/H battery
These gel cells are great as they can be best positioned to present the
lowest C of G - I am sure you will find something suitable
I am planning on either a sewing machine segmented drive belt or a very low
profile multi V drive belt (as used in electric power planers) & hope to
have my first similar report about December on line 2001
regards Derek
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Hi Derek,
--- In Paddleducks@y..., "derekwarner" <derekwarner@b...> wrote:
> Thanks for first report Eddie - sort of typifies what we are
> talking about in learning by each others mistakes - PJ has written
> & posted some very basic but very useful text on matters like this
Exactly Derek.... Although I've had a minor setback, I hope it will
help someone else so they do not make the same mistakes I have.
Can you point me towards the information you talk about above? Either
message numbers, or a topic to search for please?
> I found my 12V 7 amp/H could be substituted with a 12V 3.5amp/H
> battery which was literally 60% of the size & but came in at 50%
> weight (however since have found alternate ways to reduce weight &
> maintain the original 7 amp/H battery
>
> These gel cells are great as they can be best positioned to present
> the lowest C of G - I am sure you will find something suitable
I'm toying with the idea of changing to nicads.... I can get those
really low in the hull and they should be lighter than the gel cells
I'm using now. But what about positioning of the nicads? Are they
better placed either side of the hull, or on the centreline of the
model?
Nicads will also give me the ability to do a rapid charge at the
pondside... Something I can't do with a gel cell.
>
> I am planning on either a sewing machine segmented drive belt or a
> very low profile multi V drive belt (as used in electric power
> planers) & hope to have my first similar report about December on
> line 2001
I think my original gear drive will be changed in favour of a belt
drive... It will save space and weight, as well as being easier to
setup and maintain. Just gotta find some suitable pulleys and belts,
but I'm off to a model boat show on sunday so maybe I can pick
something up there?
I look forward to hearing how you get on later in the year Derek,
it's always nice to see how others are tackling the various problems
associated with these vessels.
I'll keep sending regular reports on my progress.... This thing WILL
sail correctly if it kills me! :-) I haven't spent all this time
building it just to give up at the first little hiccup.
Regards
Eddy
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Hi, Eddy,
Sorry to hear that Forceful wasn't everything you had hoped at the first
trial. Don't worry, though, she will come around. Remember, we don't learn
from our successes, only our "failures". I like your idea of going to
nicads. Thanks for letting us know how she did "right off the board".
All best wishes,
John
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Just a slight hiccup John.... I will get it sorted (famous last
words!)
As for only learning from our failures, you're quite right.... And I
must be the brainiest chap around if it's true :-)
The saga will continue until I get everything ironed out, or people
in this group get bored with my ramblings.... Whichever comes
first! :-)
Regards
Eddy
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Hi Eddy...okay let's have a look at this little wrinkle with
"Forceful".
Your twin 540 motors at 6V should be MORE than adequate to power the
wheels..so something is not quite right here. If anything is
misalligned in the drivetrain (gears not meshing as you say) or ANY
binding or friction in the paddle shafts this will REALLY slow your
wheels down as any problem gets compounded by the diameter of the
wheels and their friction in the water. It is essential that all
shafts and gearing must be geometrically alligned. The TOP 4 reasons
for power loss?
1) Motor underpowered (unlikely in this case)
2) Paddlewheel shaft(s) binding
3) Gears binding/belts wrongly tensioned/misallignment
4) Wrong gear ratio(s).
Paddle shafts.
I find that misalligned or binding paddle shafts are a MAJOR cause of
power loss in sidewheelers I have seen and it is absolutely essential
they run freely. Any power loss here is GREATLY compounded by the
diameter and resistance of the paddle wheels themselves. I've always
been tempted to run the paddlewheel axle shafts through roller
bearings which I've been collecting, but I've come up with the
following solution which works for me.
FIRST I don't support the axles at their outer ends of the sponson as
this will tend to throw weight OUTboard and I want to keep as much
weight as possible close to the keel line of the boat (for/aft axis).
I use 1/8" dia stainless stub axles which protrude into the wheel
bearing roughly half the width of the paddlewheel. Now this is okay
on my light styrene wheels but you may need to "beef up" the axle
diameter on metal paddlewheels which are heavier. I only use machine
grade stainless steel axles (forget BRASS or mild steel).
The wheel bearings (or hubs) should also ideally be S/steel but again
I'm paranoid about outboard weight so brass does fine. (hmmm
maybe aluminum tube would work too!) Remember, the RPM's at the wheel
are extremely slow so heat build up is not an issue. The stub axles
are locked on with a collar so the they can be slid out to release the
wheels from under the the paddleboxes.
Next and MOST important is the main paddle axle bearing(s)..the one
that goes through the hull..to me this is the INTEGRAL part of the
wheel system and HAS to be be correctly set in the boat so the wheel
ends up absolutely in line with the keel and at right angles to the
drive. If this bearing is NOT placed correctly in the hull, then the
whole paddle wheel and drive train will be skewed. For main bearings I
use brass tube which is TWO SIZES larger than the axle. This is so I
can place an intermediate bearing between the outer one and the axle.
I've also used two short intermediates inside each end of the outer
bearing with a grease bath in between and it also works fine and is
waterproof.
ALSO..if the bearing is too SHORT it won't support the axle properly
and friction will occur. My bearings are 1" long and mounted through
wood blocks which are glued under the deck and to the inside of the
hull walls. The bearing projects inboard through the wood block about
1/8" proud.
OKAY..so how do you get these bearings alligned? Well I CHEAT as it's
almost IMPOSSIBLE to get the bearings aligned by drilling the holes
correctly first time round. I drill the holes through the hull and
wood blocks a little bigger than they need to be so this allows the
bearing (tube) to "waggle" a bit. I insert the shafts, attach the
wheels and carefully allign the wheels and bearings using a precision
square. Once I'm happy with the alignment I set it at the inboard end
with a quick dab of hot glue around the 1/8" lip of the tube
projecting through the inboard end of the wood block. (DON'T GLUE THE
AXLE!!!)This is just enough to hold the bearing in place for testing
and if I have made a b**lls up of it I can still remove it and try
again.
You can actually tell when the wheel is "running free" because when
you put on the power the revs increase. When I am sure of the
allignment I then permanently glue the bearing into the wood block.
This is primitive to say the least..but dammit..it worked for me.
I don't care how you accomplish all this..just be conscious of the
possibility of creating unwanted friction by misalligned axles.
Next thing..MAKE sure there's NO BINDING between the paddlewheels and
hull faces. I use lightly greased stainless slip washers which I first
chuck in a drill to polish their friction faces with 0000 steel wool.
I allow the TINIEST bit of sideplay in the wheels but make sure they
are not attached too tight to the hull.
GEARS/BELTS - this is pretty self explanatory..if the gears/pulleys
are misalligned, worn or working too tight, then unwanted friction
will occur. Do the paper test with gears (try to avoid metal gears if
you can...too heavy and noisy!) and with belt drives make sure your
motors are on fully adjustable slide mountings so you can achieve the
optimum belt tension...THIS IS CRITICAL for good performance.
> So I put it on 12 volts and that certainly gave enough power, but
>upset the trim of the model too much, since the batteries sit in
>front of the paddles, it looked like a submarine about to dive! :-(
I BET it did!!
GEAR RATIOS - if the wheels slow down too much when you drop the boat
in the water, then either the motor(s) are too weak or the gearing is
wrong.
You should have absolutley no need to power the boat with a 12V
system. My own preference is for paddlewheel rotation at approx 180
RPM out of the water. This should drop by a maximum of 30% as you
drop the boat in so you end up with about 120 RPM in the water at
maximum throttle. Frankly I have no prob with wheels turning faster
than that, except they will eventually cavitate and lose efficiency
especially once the boat reaches hull speed...BUT you can always ease
BACK on the throttle if they're churning too much air.
Batteries ? well I make up my own packs from nicads out of discarded
cell phones or (even better) camcorder batteries which are made up of
1.2v cells. Call your local cellphone people and ask them. I get
mine free and after I've tested each cell, I solder up the terminals
in series to give me the voltage I want. I then tape and shrink tube
them. I have tried to wire them up in parallel to get extra capacity
for low voltage apps...but these packs did funny things (namely to do
with heat!!) when I tried recharging them! If your system is running
right then a small 2 Amp/hour gel cel (or a couple of 1 A/H gels in
parallel) should do the trick... but I still prefer nicads for THIS
kind of application. I would also separate your receiver/servo
circuit onto its own 6 v power.
> I also had a problem with my gear drive system, one of the paddles
> works fine (they are independently controlled), but the other isn't
> meshing correctly which again only showed up when the paddles were
> under load with the boat in the water :-(
Remember..problems of friction in the drive train will be compounded
by the paddlewheels in the water.
>
> I'm undecided wether to play around with my gear drive to get all
> the faults ironed out, or switch to a belt drive system.... The gear
> drive can be made to work, but because of the ratios it would
> require 12 volts to operate and the boat simply cannot take the > >
> weight unless I can find a lighter 12 volt jell cell (or maybe >
change to nicads) -
> Whereas the belt drive wouldn't be so highly geared and would
> probably work okay on 6 volts.... Ho hum, decisions decisions...
Eddy, you don't need to go to 12v as a 6V system will work fine...but
the secret is finding small, lightweight, low revving, low current,
hi-torque 12V motors and running them at 6 volts to half the revs. My
own pref is for belt drives but that's only coz I'm too lazy to make
up the gear boxes.
> I also found that the model (like all paddlers I've ever seen in
> model sizes, and probably the full size vessels too?) is incredibly
> sensitive to balance port and starboard.
I have replied on the "balance" issue to you privately..but since it's
so critical to sidewheelers, I'm going to post it here too.
Like I said..with a little bit of patience, you WILL get your
"Forceful" running as fine as she looks... and if she's anything like
my smaller 1/64 "Director" she'll be a joy to behold on the water..a
real crowd pleaser and KILLER in steering competitions!!
Keep us posted, buddy!
PJ