Story edited in May 2013.
This story was written a few years ago and is about conversion of my nitro Llumar to electric. This is the boat that eventually got destroyed in the
US in 2012. The boat was originally built in ply, from scratch, from Newton Marine Plans.
The guts of Llumar ripped out ready to convert to electric. Cheap motor already on its way from Hobbycity in Hong Kong - a KB45 -17 XL 700 kV. ESC( ETTI HV 200-10-40) also on its way from South River RC. Boats.Lipos are on back-order.......
Some photos of the rebuild
Battery layout proposed
Motor installed - cheap KB45 17XL for testing only - a better motor on order (Edit: a Neu 1527/1.5Y was on order )
I'm going to try a square drive - a bit of square brass tube in a snug drill hole in the aluminium, fixed with two grub screws and the gap filled with epoxy.
Edit: Subsequently I replaced this with a second (stronger) version with the brass square tube inside a close- fitting circular brass tube, gap filled with solder rather than epoxy, then the circular tube held with two grub screws: I’m still using this home made square drive. It works perfectly.
She is one beast of a ESC - heavy duty soldering required...
Still awaiting arrival of the lipos ordered from HK (quite a few ordered !!! - some 5S, some 4S, & some 2S !!, Got a card from the courier when I got home tonight - so maybe...)
Edit. The false cowl (under hatch)is visible upside down in the picture above and provides ample room above deck level to conceal equipment protruding above deck level (eg batteries and ESC). If the vertical height within the tub had been sufficient I would have used a flat ply sheet instead.
About all that needs to be done is installation of receiver, receiver cells, and antenna and platforms to carry the lipos and a bit of plumbing etc, under-hatch is done.
Edit: I never ran the reddish motor shown above. It was a Turnigy outrunner.
No motor-mount cooling rigged at this stage - I have made some cooling fittings and have the necessary rods and special flux to "'solder", "braze" "weld" (call it what you might ?) aluminium, but I need to make another mount as you have to heat the parts close to the going 'limp' stage, and I want a spare mount before I try that in case of....well, "errors" shall we say.
Edit: I never did, I’ve only ever used a conventional cooling can around the inrunner motor body.
I note the Turnigy motor is 40 dia x 30 length while the more expensive (US$189)Scorpion HK4035 800 outrunner is 40 mm x 35 mm and is rated at 4200 watts (5.6 HP)!! The closest to the Turnigy 600 looks to be Scorpion HK 4025 890 which is rated at 2380 watts (3 HP), So I guess the Turnigy is probably safe to about 2500, maybe 3000 watts (4 HP). On 10S (36 volts) this means up to about 85 amps, or on 8S (29 volts) up to about 105 amps.
Should be interesting......
Well all the Lipos all turned up in a rush, but how do I fit everything in??
Those doubled up cables don't bend very easily and that ESC/capacitor bank is rather bulky!
I think layout below is the most practical layout without needing extension cables. CG is close, and there is room for some foam and packing.
Ran a first electrical test - all the right beeps and bleeps and NO SPARK WHATSOEVER with the resistor bypass.
Not much more to do....
Its going to be hard to fit it all in with the batteries fore and aft of the motor. I have seen pictures of the ESC on a tray on top of the motor to keep wires short.
First test run at Wattle Farm, 27 June 2010 - KB45-17XL & 10S1P on an X646 three blade prop - scared the crap out of myself. Goes just like a Nitro 1/8th. CofG not adjusted yet (too far aft), so rather flighty and speed not checked, but looked to be about 70k, maybe a bit more. Very pleasing first test run performance, for a US$45 motor!!
Final layout as below
Edit: Note the black under hatch (right way up)
We tried an Octura X452 three blade this time. Only a very short run as the radio did not appear to be completely reliable (yet to install the 2.4 gig futaba receiver) and I chickened out on the last turn as started to head a bit too close to the far bank !!!!
Hard to tell if speed better or worse, but was pretty ragged heading into the stiff breeze. Also looks like the ESC has a fairly gentle throttle curve as it seems to take a bit to wind up.
For info, the all-up weight is 8.0 kg (just under 18 pounds) with KB45 motor & two Zippy 5000 5 S packs
Neu Motor on order.
Edit: I only ever ran the boat a couple of times with the blue KB motor. It was not very efficient, and the Neu motor arrived not long after. The Neu transformed performance to effectively equal to good nitro performance.