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Old Apr 20, 2012, 04:47 PM
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Doh!
Check out the contents of the accessory bag which I overlooked before.
Appears to have adapter stand-offs for a regular servo, along with screws. This changes everything.
I'll still go to the pond but this boat could be gutted before the day's out and real RC gear installed.

Cheers,
David
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Last edited by KiwiDavid; Apr 20, 2012 at 04:51 PM. Reason: Oops - forgot the pic
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Old Apr 20, 2012, 07:56 PM
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Hi,
Well I headed down to the lake with the new NQD and what can can I say? Exhilarating, responsive, nimble - certainly none of those.
The boat has digital speed control - as in OFF or ON (no medium). Digital steering too - centre(ish), hard left, hard right. Estimated speed was around 12kph. I have a Chris Craft which does 13.4kph and it would be slightly quicker than the NQD.
Handling is awful, full throttle or nothing and rather orthogonal steering. I also felt it was either not fast enough to fully get on the plane of it needed weight at the nose - it was decidedly pointing high. Perhaps when the motor is run in?

I stopped off at a model shop on the way back from the lake and bought a servo so I may have more detailed pics to come when the boat is gutted.

I also tried the old white boat with the rudder modified - definitely better but perhaps not enough to relax about. This thing eats the NQD and only uses a 540 motor also.

Cheers,
David
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Old Apr 20, 2012, 11:59 PM
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Hi,
Regular servo now fitted and all other electronics removed. Decided against using the paired stand-offs supplied with the model and instead used some nylon hex pillars. The reason was that the kit ones set the servo arm a tad low for good travel of the actuator rods. The original "servo" had the servo saver on top which increased its height.
This looks tidy and I tested it with a receiver borrowed from another model and it is very smooth - quite pleased.

I have a bit of egg on my face - when I got the boat yesterday I was surprised how tight the prop was to turn over but put this down to the gearbox, something I have never used before. Well......today I found that the drive dog and the shaft retaining collar were hard against the plastic at both ends stopping the prop from freely rotating. Had I picked up on this at the lake I could have seen a more sparkling display. I guess I have to apologize to NQD for comments about the poor performance and instead target their poor assembly and quality control.
I still should have picked up on this but what if.....an accountant had bought the boat?

Tomorrow I'll do a PWM drive for the motor but first have to remove it to see what is hanging off the back of it. I can see the usual disc cerami caps for noise suppression but there's something bigger - a radial electrolytic cap. No problem for a relay/battery drive but I don't want it there when I'm PWM switching at 4kHz.
What an exciting 24 hours for that boat - unwrapped, tested, gutted and partially rebuilt.

Cheers,
David
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Old Apr 21, 2012, 06:00 AM
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Hi,
All done! Conversion complete......after stealing the receiver and controller off my Brave Class fast patrol boat.

I've attached the last pic of the motor before it went back in to the boat. The big thingy across the motor is an old ultra fast diode. I normally put an axial mount 8A Schottky directly across the motor terminals (no reverse) but had run out of them so this will have to do until the motor upgrade. The electro cap I spotted across the motor was a 47ufd, 16V non-polar cap. Have never seen this before.

To change the motor I have to open up the gearbox as I think it's screwed on from inside the box. Will leave this sticky job for another time.
Running the motor at low speed there is a bit of vibration from the outdrive and I get the feeling the shaft coming out of the transom is a little too high to line up with the drive itself. I may be able to get a little movement but not much and I'm still learning about these things.
At full left or right rudder the motor also slows down when running at low speed but I would expect a universal to present more friction at higher angles.

The little circuit board in the pic is my PWM controller. It uses a single 3milliohm fet and I've used it on motors with stall currents up to 60A without problems. It's very cheap but has most of the features of a brushed controller - one off Tx learn mode, parameters stored in EEPROM, low battery indicator (cuts power to about 1/3rd), throttle inertia (for big boats) and loss of signal failsafe.

Will head off to the lake tomorrow again and hopefully freeing up the shaft will see an improvement in speed. I know the handling will be better with proportional steering.

Cheers,
David
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Old Apr 21, 2012, 07:58 PM
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Hi,
Final report. The boat performed surprisingly well with full proportional steering and speed. Top speed was perhaps about 20-22kph, not the 30mph some sites advertise but still an exciting run.Appears to be very stable and turns very sharply when required. The water cooling also seems to be working with the higher speed but I question how effect water cooling is for a brushed motor given the very limited heat conduction via the bearings and brushes. The boat has a gentle bobbing movement at top speed on a glassy lake.
All up I very pleased with it now but I may still change the motor or battery or both.

If you can pick one up cheap (discontinued stock) then the upgrade is relatively easy thanks to the standard servo mount being molded in already. The performance won't disappoint.

Cheers,
David.
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Old Jun 03, 2012, 06:06 PM
Fly, crash, rebuild.
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Super Hawaii Revived with Feigao 10XL 6S 240A ESC Turnigy Marine X447 prop
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Old Jun 04, 2012, 01:38 PM
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Sneek, Netherlands.
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Quote:
Originally Posted by KiwiDavid View Post
The water cooling also seems to be working with the higher speed but I question how effect water cooling is for a brushed motor given the very limited heat conduction via the bearings and brushes.
David.
Hi David,

Good to hear your modifications worked out!

You are right regarding the cooling; a simple coil is not very effective, unless you add some heat conductive paste to enlarge the contactsurface.
Cover the coil with a piece of heatshrink, which presses the coil on the can (a little) and covers the past, which is nasty stiff specially on your clothing...



Much more effective is adding brushtab cooling, which draws heat from where it's generated, the brushes, just solder a piece of brass tube to each brushtab and connect them to the cooling circuit.

Regards, Jan.
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Old Jun 05, 2012, 05:05 AM
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Hi Jan,
I guess brushes and copper losses are the main heat sources but to be honest I'm not sure this boat needs much cooling.
I understand it's a 550 type motor so naturally lower revving and higher torque than the 540 (??) It also has the gearbox so the motor is well buffered from heavy loading.
It's not spectacular but I can give the controls to anyone and it will turn at any speed. It also has a good duration on a charge so I'm fairly happy with the outcome. (wonder how my spare Speed 500 would go in it?)

Cheers,
David
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Old Jun 05, 2012, 10:54 AM
Boaters are nice people.
Sneek, Netherlands.
Joined May 2004
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Hi David,

No problem, if a boat can do without watercooling, don't bother...

I just wanted to show you the option.

Regards, Jan.
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Old Jun 06, 2012, 03:29 AM
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Hi,
I appreciate the cooling ideas conveyed and have other boats that are more in need of it than this boat.

So why can't they make square section aluminium/aluminum cooling pipes? Surely this would provide a much greater contact area than a mere tangent to a pipe. No more thermal gloop. Perhaps square section won't bend easily.

Cheers,
David
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Old Jun 06, 2012, 05:50 AM
Boaters are nice people.
Sneek, Netherlands.
Joined May 2004
4,878 Posts
Hi David,

Bending square piping into a coil would be quite a challenge...
The next best/better thing would be a cooling jacket, where the water runs directly on the fluxring of the motor (which is shielded against rust with a thin layer of polyester tape).

This is so effective, that the moisture in the hull will condens onto the jacket, specially in spring, when the water is still very cold.



Regards, Jan.
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Old Jun 07, 2012, 05:07 AM
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Hi Jan,
Dare I say it? .....that looks cool.
Thanks for the tutorial on motor cooling.

Cheers,
David
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