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Author Topic: Brushless Trial Boat  (Read 11425 times)

andyn

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Re: Brushless Trial Boat
« Reply #25 on: January 13, 2009, 03:55:55 PM »

Nope, if you want something really quick, then have a look at Mr Krabbs SAW

http://www.astecmodels.co.uk/catalog/product_info.php?cPath=2_89&products_id=210

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andrewh

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Re: Brushless Trial Boat
« Reply #26 on: January 13, 2009, 04:22:45 PM »

Subculture, or can I call you andy and thus distinguish you from andy, and andy and andy*1961*

Thanks for that - I'm sure it will go like stink, just wish my original BL had not got "whatever its got" as its small size and wild revs are just what's needed here. 
How about you distract AndyN  - perhaps by discussing names - whilie I liberate his Feigao?

I can see I will have to learn about flexibles, outdrives and other arcana sometime

andrew
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dreadnought72

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Re: Brushless Trial Boat
« Reply #27 on: January 13, 2009, 04:44:16 PM »

Oi! I'm not THAT old.

Andy, changing his name to NA553568B
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Enjoying every minute sailing W9465 Mertensia

Subculture

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Re: Brushless Trial Boat
« Reply #28 on: January 13, 2009, 04:47:16 PM »

I agree that you can't beat a hydroplane for speed. However they do need calm conditions, a monohull will handle a bit of a chop better, and they turn nicely too.

andrewh

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Re: Brushless Trial Boat
« Reply #29 on: January 13, 2009, 05:00:05 PM »

Sorry dreadnought72, I wasn't casting nasturtiums about anno domini. 

All andys/andrews/andres are valued highly, its just I'm suffering from ......... what's it called when you can't remember things?
andrew*1949*

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andyn

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Re: Brushless Trial Boat
« Reply #30 on: January 13, 2009, 06:17:35 PM »

I can see I will have to learn about flexibles, outdrives and other arcana sometime

How about now?

Firstly, Outdrives, don't bother.

Flexi's then, Illustrated by means of pictures.


Photo 1 shows a Stinger drive. These are complicated units that are usually much longer than Struts (Photo 3), and encapsulate the end of the Flexi and the solid propshaft part. The solid Propshaft (Black bit in Photo 2) is soldered onto the Flexi, which has a square end at each end. Some are round both ends, but are stupid because they slip around everywhere if everything is not tight. The prop is held on by a Drive Dog on one side, which screws by means of an allen nut onto a filed flat the solid propshaft, which keeps it in spin with the motor. Everything is then held in place with a nut on the very end of the solid propshaft. Leccy boys put a piece of silicon tube between the nut and the prop so there is a bit of give if the boat hits something. Proper boaters don't bother ;D The flexi goes though a piece of brass tube known here as a 'Stuffing Tube', which is bent to the required angle in the boat, and has a piece of lead teflon lining tube inside it. Flexi's must be taken out after each run and stored in a tube full of grease. Struts run on the same principal as Stingers, and most have a rudder attached to them. Both are adjustable by loostening off very slightly some allen bolts and adjusting the angle that they sit at, to adjust the thrust line to raise or lower the bows of the boat under power. With all surface drive systems, a wedge rudder is needed, that like the strut or Flexi is mounted on the transom of the boat (Photo 4). The Flexi is connected to the motor by means of a FlexHex, like a pin drill vise that connects to the motor, and depending on whether you have a round or square drive, the Flexi goes into the Hex and you tighten it up with a pair of spanners, which locks the Flexi in. The FlexHex connects to the motor with a grub screw

Struts and Stingers have far less friction in them and can spin faster, and because of the way the prop can draw in air and mix it with the water, you can go a lot faster and make some pretty nice rooster tails. While a flexi is spinning, it actually 'snakes' within the stuffing tube, this can reduce speed and wear things out faster. The problem however is that rooster tails are wasted energy. The other problem with Surface drive is Cavitation / Aeration, depending on whether the prop is too low / high (respectively) in the water.

Hope this helps

Andy *1992* :-))




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andrewh

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Re: Brushless Trial Boat
« Reply #31 on: January 28, 2009, 12:47:49 PM »

Sorry about delay in replying and trials - work and family needing my presence.

Andy - thanks for the hardware tutorial - excellent and understandable

Generous benefactor - thank you very much for the gift of two beautiful little speedboats.  I will have to distract Andyn and "borrow" his high KV Feigao brushless to do it justice.  White dwarf is VERY much like the little boat that you got at Warwick!

My Bell motor has been grafted into the PT boat - it is a low KV device - for a small BL motor - about 1200KV so I have great hopes that it will turn a reasonable prop well.  So I am giving it a try on the 35mm graupner 2-blade fitted and will see what happens on various voltages


And tell you!
andrew




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andyn

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Re: Brushless Trial Boat
« Reply #32 on: January 28, 2009, 02:19:05 PM »

I think perhaps the Dyco coupling will be a little too big, and will probably draw too much power from the motor.

I'll have a look for you I think I have a much smaller one.
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andrewh

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Re: Brushless Trial Boat
« Reply #33 on: February 03, 2009, 01:15:19 PM »

Thanks, Andy.

Its OK for trials - I just thought that it looked a little more "pukka" than my usual silicone-tube-and-tiewraps device.

Report on trials of 1/32nd PT boat with BL "bell motor"

The boat is my unfinished 1/32 Higgins PT boat
http://www.modelboatmayhem.co.uk/forum/index.php?topic=12272.0
Original motor:  Graupner S600, 7.2 Eco
Prop (?graupner) 2-blade  - 35mm dia racing prop

This trial:
Brushless "bell" motor - 2508/21 1250KV - rated 100W
10A forward only speed controller, cheap, chinese - no identifying marks
Batteries used - 8X1000mah nicad pack , 6 x 2100 Nicad Buggy pack

I took the pt boat for a hurrl on a wet weekend morning just to see if the setup had promise.  My aero ESCs wear 3mm gold plugs, so I made a tamiya-to-3mm adaptor to fit the batery packs

8 cells - (9.6) V
VERY sprightly performance  - no measurements, but speed and "sit" on the plane appeared to be very similar to performance with S600 motor.  I did the test in 3 or 4 very short bursts, checking the motor, ESC and battery pack for temperature with my digital thermosensory facilities (fingers) 
At all times the motor was completely cool, ditto the ESC and the battery pack just a few degrees above ambient.
This set my mind at rest that the prop was NOT too big for the motor (it is essentially a low KV motor - very similar KV to the Eco 600)

6 cells - heavier, lower voltage but greater capacity
Still good speed and continuous planing.  Less speed, but again comparable to the S600.  No sign of heat in any component and I terminated the trial when the ESC started "stuttering" - presumably low voltage, so I brought her in.

I have read a post where a mayhem gent showed a picture of a bell motor, and asked "will this power a boat?"

 Despite searching the I have not been able to find the post again - but the answer is a palpable YES!
For excitement more volts would be good - I was clearly nowhere near the 10A continuous of the ESC (still less the 15A burst) so I am crocheting some Li-ion packs for her. 

These are made from reclaimed laptop battery packs, I am using 3S,2P to give good capacity and more volts.  I believe the capacity of a single cell is about 1500MAH so this pack is 12V, 3000 mAH
If I am drawing 7A I should get nearly 1/2 hr running with considerable velocity

I will mention that this bell motor gets its name from the shape (looks like a bicycle bell), the weight (weighs the same as Big Ben) and the NOISE - it is very noisy when running!  This is a characteristic of this make and model of motor only - it is not true of any other BL motor!

more as it happens - with pics and video
andrew
 
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andrewh

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Re: Brushless Trial Boat
« Reply #34 on: April 16, 2009, 12:58:27 PM »

ahem.  Now where were we?

Ah yes, doing real trials of dirt-cheap brushless motors with actual boats.

(Remember,  I have only one aero BL ESC without reverse; but trials of the andrew- Werdna system are promising and should be availble tomorrow :})

Following retirement of the Razor footy trial hull (it has gone to a good home for re-conversion to a footy racing yacht) I have two trial boats: 

White Dwarf -
epoxy/glass, beautiful german moulding.  White (surprisingly)
2mm shaft, Graupner 29mm racing carbon prop (George Turner) as used for S400 racing
Motor - homemade GoBrushless 22mm kit  (2208-15) (Newbie wire) Kv unknown - guess at 1500
Cells:  2S 650 mah Lipo or 3SLi-ion (salvage cells ?1500mah) or 7cell Nicd 350Mah
rudder/esc/werdna reverser - 3 channels

Trails took the form of a pair of 13-year old boys on the controls and me on the camera, so there is an element of randomness about both parts.
What I can say is that the full speed is impressive, the turning ability breathtaking, even on 2 cells.  I never did run the 650 MAH lipo right down in the time we dared to run it - we stopped at about 3.5 v/cell (still 1/4 full)

internal layout - batteries sit on the velcro strips as far towards the rear as possible

on the water - nice sit, maybe a little tail down

Video clip gives you an idea of the turnability :}
more on the PT boat later
andrew


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andrewh

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Re: Brushless Trial Boat
« Reply #35 on: April 16, 2009, 01:07:44 PM »

Just to whet the appetite - here is the Higgins 1/32 with bell motor






details follow
andrew

sorry about the rats-nest wiring configuration in the white dwarf
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