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Tugboat Craig

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sammyk24/05/2009 19:00:44
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105 forum posts
34 photos
looking good barry looking good  regards sammyk
Peter Fitness25/05/2009 00:51:49
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510 forum posts
215 photos
Barry, what size prop and motor are you intending to use?
 
The build's looking first class, and I'm still tossing up whether to build one myself as my next project.
 
Peter.
Barry Foote25/05/2009 09:25:41
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161 forum posts
93 photos
Thanks fellas..

Peter,

I am going to use either a 60mm or 63mm brass prop. The moter I am thinking of using is an old 540 electric, as I have one and am trying to keep costs to a minimum. I am told I will need a 2:1 gear reduction on it, but will have to give it some thought.

Barry 
sammyk25/05/2009 12:45:24
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105 forum posts
34 photos
hi barry you would be better if the motor had a gear reduction on it thats a big prop to turn .the 540 will turn it but it will get very hot and the battery will go flat fast regards sammyk
Barry Foote25/05/2009 20:04:35
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161 forum posts
93 photos
Thanks sammyk,

Unfortunately as i have limited access to water, my builds tend to sail a couple of times and then end up in a case, so i think I will go with it. If I am fortunate enough to find a good sailing water, I can always change it.. 
Yabbie126/05/2009 02:02:47
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54 forum posts
14 photos
Barry,
 
sammyk is right - directly connecting a typical 540 motor to such a large prop would be a grievous mismatch requiring the use of fireproof paint in the engine room!
 
Given the great work you've done so far, it would be worth getting this right even if you will only sail it occassionally, rather than have to change things later.  There are quite inexpensive gearboxes available for these motors, designed for model aircraft, that bolt on to the end of the motor.  I would suggest about 3:1 ratio.  If you are concerned about possible gear noise you could use a toothed rubber belt drive.
 
The gear reduction will also give you better low speed control, important for a tug.
 
Yabbie 1
Barry Foote26/05/2009 08:32:52
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161 forum posts
93 photos
Yabbie 1,

Great to know you are still checking in. I really am enjoying this build, it rreally tests the brain and skill levels. I will do as you suggest and get a gear reduction for the motor. 

In the mean time, I will try to make some progress on the superstructure..... 
Peter Fitness27/05/2009 00:40:03
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510 forum posts
215 photos
Barry,
 
As Yabbie1 suggests, a belt drive is definitely the way to go for quiet running. I make all my own pulleys and use 1.5 mm or 2mm O rings as belts. If extra grip is required, such as in your case with a biggish prop, then I would use double belt pulleys. However, if you don't have access to a lathe, then a gearbox would be your alternative.
 
Peter
Barry Foote27/05/2009 08:54:05
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161 forum posts
93 photos
Thanks Peter, sound sa great idea, but I only have asmall lathe attachment for wood, so looks like I will have to get a gearbox. I think I will try ACTion Electronics......Mind you if I do that Dave will persuade me to part with big money....that said, his gear is great..
60watt28/05/2009 21:15:47
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253 forum posts
14 photos
Model
Voltage
NO LOAD
AT MAXIMUM EFFICIENCY
STALL
TORQUE
OPERATING
RANGE
NOMINAL
SPEED
CURRENT
SPEED
CURRENT
TORQUE
OUTPUT
EFF
RPM
A
RPM
A
mN-m
W
%
-
mN-m
RE - 800
12.0v
12.0v CONSTANT
5167
1.058
4289
5.28
-
82.08
36.84
58.2
-
482.8
 I think I've discovered another limit placed on forum posts.This is going to take more than one to make my point.
Barry,you can appreciate a 60mm prop wont do more than 2000 RPM so you have to gear a 540 until the shaft RPM is above 7000.
2:1 won't be the right ratio
540 and a 5-pole Mabuchi 775 to follow
 
An 800 and 775 are like a 540 geared 2.5:1 albeit a larger size and shaft diameter
A 775 will set you back $13 US and $11 airmail per packet at most






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