New Turnigy Electric outboard project 6KW

Bazaki

Bazaki

10 kW
Joined
Dec 25, 2009
Messages
639
Guys,

My latest project with building an E-outboard has come to an end.
qocbcz.jpg

imag0561.jpg

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http://youtu.be/rb2FkCF-e58



It is an Agni 95 R with a 600A peak power Kelly controller with some HK 6s 5ah Lipo packs. But it makes some noise and it looks like an gasoline outboard, so every neighboor thinks that it is ilegal, ( only electric allowed at the lake )

So I want to go more silent and stealthy so I have a new idea and would like to hear what you people think about it.

newoutboard.jpg


http://continuouswave.com/cgi-bin/propcalc.pl
I use this calculator and add 20% slip ( not sure if that is right )


So I want to put one shaft through 2 Turnigy motors and rewind them for 51 RPM/Volt, I believe some people at the forum have done this successfully.
Each motor will get it's own controller, with my Agni 95 R outboard I draw 6000 watt to go 27 km/h which is fine for me, but that was with a gearing and imbalance, so a directdrive should be more efficient right ?

Any thoughts ? Maybe not an Turnigy RC motor but a stock motor that can handle these powers ?
It needs to be a small size diameter motor, the Agni motor is a pancake size and it to wide to put it under water.

Can one big strong brushless 8kw Kelly controller handle 2 motors at the same time ?
 
http://www.torqeedo-belux.com/technologie/Technology%20Torqeedo%20Motor%20Propeller%20Battery.htm

Torque%20engine%20with%20diameter%20700.jpg

Drive%20train%20details%20700.jpg


Something like this for example, maybe some sort of gearbox would be better, so I can use the original 170v/rpm from the Turnigy motor
How or where to get a Gearbox, does anyone know something about that ?
 
Ok nice ! And what about your under water housing, controller.
How much rpm you want to have at this prop ?

Please keep me updated :D
 
Good luck with this! I'd like to build a 12s 80-100 sea scooter one day. I'm interested to see how your setup comes out. Those Torqueedo's are sooo expensive for what they are :-D
 
Well, first I want to finish the E ouboard with my rewinded 55kv Turnigy motor. If everything runs fine then I will make with the same setup a electric surfboard, and later I also want to build a fast electric under water scooter. I already bought a stock waterscooter.

And Vax. What gear reduction will you get ? 1:3
 
very cool project!

i have been wanting to build something like this for a long time

i have two ideas.

1. use a magnetic coupler to on the output shaft, for complete mechanical decoupling of the output. this way you dont need a seal on the the shaft. and the motor will be in a 100% sealed box
with these magnets: http://www.kjmagnetics.com/proddetail.asp?prod=D84B-N52. theoratically you can tranfer 1,3Nm per set of magnets on a 100mm diameter circle with an 1.5mm gap between the magnets. (up to 20 magnet sets is possible with the 100mm diameter pitch circle)
something like this http://www.couplingtips.com/magnetic-couplings/ only diy. in the gap between the magnets will be a plastic separator.

2. put the stator in a epoxy cast, and just use it under water. this way you have good watercooling, and the copper/laminations will be protected from the water. and use stainless steel bearings
with this epoxy: http://www.mgchemicals.com/tds/tds-832tc-2parts.pdf (you can buy it at mouser, for 30 euros for 450ml. )
i have no idea if the epoxy is thermally conductive enough to keep the deltaT low beteween the windings and and the water. some tests need to be done.
 
7100601.jpg


Well I just bought a motor like this, and then a bigger version with a under water housing of 100mm diameter on the inside. Inside want to replace it with a C80-100 Turnigy motor.

My daily boat is in the water for years with a stock whispermotor under water for years too, so the sealing should't be a problem I hope.
 
yes my ideas are more suited for the underwater scooter, where the pressure on the seals is much higher.

what material is the black housing? if they are metal, you need a space beteween the motor and the housing because of eddy current problems (more losses)
 
Metal housing, I expect it tomorrow to arrive at my door.
The motor is 80mm on the outside, the housing is 100mm so there is some space in between if that is what you mean.

Why would there be more pressure on the seals at an under water scooter ?
 
Besides parasitic drag from the water there is no reason a brushless wont run submerged without a sealed casing is there?
 
E-racer said:
Besides parasitic drag from the water there is no reason a brushless wont run submerged without a sealed casing is there?
Click to expand...

in theory a brushless motor will work fine submerged.

a few thing though.
rust on the stator
need of stainless steel bearings
the seals of the bearings need to be able to handle the water pressure (0.1bar per meter of depth) or else water will enter the bearings, and shorten their lifespan

Bazaki said:
Metal housing, I expect it tomorrow to arrive at my door.
The motor is 80mm on the outside, the housing is 100mm so there is some space in between if that is what you mean.

Why would there be more pressure on the seals at an under water scooter ?
Click to expand...

yes sorry my last post wasn't very clear. if the rotor of the motor is in close proximity of a stationary metal object, the magnetic field of the motor will cause eddy current losses. 10mm should be enough with these motors, but if you encounter excessive heating of the housing this could be the problem.

what i meant with pressure on the sealings is: for every meter of depth the pressure between the inside and outside of the motor housing will rise with 0.1 bar.
so the deeper you go, the harder water will try to enter the housing. therefore a stronger seal (with more friction losses) is needed.
 
ahh yess. I overlooked the rusty stator problem. I like that the torquedo uses an outrunner :D
 
Ok I see ! I never thought of that, a metal casing can disturb the magnets of an outrunner ? Ok, well I hope 10mm space is enough.
 
some motors leak more magnetic flux than others, a good test to see if your motor leaks flux, try if a paperclip will stick to to the outside of the rotor.
if it barely sticks, you have noting to worry about. but if it sticks pretty strong keep an eye on the heat. but with the motor underwater, the housing will be cooled pretty good.
 
I tried, nothing attach to the outside of the outrunner, so I'm good with that.
As for the cooling, the housing will have a very good cooling, but inside is the outrunner, I'm afraid this will become very hot.
But we will see what happens.
 
you could run the motor in a bath of oil to help tranfer the heat to the housing.
there are some posts of putting oil in a hub motor, there is no reason it could not work here.

edit:

found the thread:
http://endless-sphere.com/forums/viewtopic.php?f=30&t=34369&hilit=cooling
 
have you thought about the deflection/stress in the vertical pipe the motor is connected to? with the extra thrust of the bigger motor, there wil be more strain on the pipe.

did a quick calculation:
pipe: round 30mm wallthickness:1.5mm
400mm beteween center of the motor to the first point it is clamped to the boat.
a thrust of 480N (found on the internet: 750W->10kg thrust) for calculating i used 60% efficientcy so 6000W input/3600W output. this will lead to 10*(3600/750)*9.81=~480N


this will lead to a deflection of 3.6mm
and induce a max stress of 210N/mm2 (the max for steel is 235N/mm2)

the 235N/mm2 is the absolute maximum. you want to stay atleast 30% form this point. so 160N/mm2

could you confirm my guesses for all dimentions are in the ballpark?
 
I never made calculations or expectations about this.
I just want to put the Turnigy 55kv in the 100mm housing, add a shaft to the outside with a water sealing and add a prop.

I just made calculations about, volts/ amps / rpms / prop pitch etc.

Maybe this is too simple ? I don't know, if you see some errors please let me know.
 
+1 to nieles for pro engineering tip of the week! I've actually experienced a similar situation when I modded a gas 2 stroke trolling motor. The motor mount (cast bit that bolts to the transom) failed catastrophically.
 
Well, a small screw does not attach to the Turnigy outrunner, but when I put the turnigy in my metal housing, see picture, it does get stuck to the housing, when I centre it to the middle I think I feel resistance when rotating the outrunner :(

So perhaps this metal housing isn't a very good idea, or maybe someone knows a solution ?
Maybe I can find someone that can make this same part but made out of aluminium. That would solve the problem.

imag0368e.jpg
 
it doesnt matter if the housing is steel or aluminium. all electrical conductive materials will have the Eddy current problem.
here is a youtube vid explaning what is happening:
http://www.youtube.com/watch?v=otu-KV3iH_I&feature=related


but with the airgap of 10mm i would just test the motor in the current housing. do a no-load test to confirm the housing doesnt get too hot, and you will probably be fine. (with the housing in the water it will be cooled pretty good)
 
Thank you ! I never knew that, I almost invested lot's of time and energy to get this metal housing made out of aluminium.

I will do some no load test with and without the housing, the heating of this outer housing is not a problem but if it will get warm, that mean lot's of energy get wasted.

At the video the last few seconds they showed a copper pendule with gaps, maybe I can make gaps or drill holes in my housing and fill it up with epoxy.
 
that would be possible, but isnt it easier to make one out of fiberglass and epoxy

fiberglass cloth:
http://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=9786

layup youtube vid:
http://www.youtube.com/watch?v=67Nd5pqYtCc

you could use the steel housing as mold. but then the fiberglass housing will be slightly bigger.
 
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