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I would speculate that the motor controller would overheat and shut itself down long before the forklift motor would be hot at those amperages. I'm interested to hear how your first test went whenever it happens!
 

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I would speculate that the motor controller would overheat and shut itself down long before the forklift motor would be hot at those amperages. I'm interested to hear how your first test went whenever it happens!
the motor needs RPM to cool itself (or external fan).

problem is at low RPM you need lot's of current to make power. high current = high losses = heat.

but 12 inch motor...that's a beast!!
 

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Its what was available, and the RPM was right, plus it was nearly new, its a drive motor with fan, and the job of putting a flange on it was easy, I am hoping that the warm/hot air will be ducted to the batteries to keep them warm, LifePo4s which give their best at 20 degrees or so. I was hoping that cruising would have an RPM of 700 or so and not to large a current draw, I will soon know fingers crossed for success
 

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the motor needs RPM to cool itself (or external fan).

problem is at low RPM you need lot's of current to make power. high current = high losses = heat.

but 12 inch motor...that's a beast!!
Well today the motor was spinning in anger and it can certainly strain the ropes, tomorrow I will have the meters in place so will know what amps its drawing, as for a beast you did say go for a big one, so I did..........:eek:
 

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So Yesterday I had a trial run, it performs well draws 52 amps 3.3KW at approx 3mph, the temp of the motor was 72 degrees C at the end of an hour run, controller was 32 degrees.
It can draw over 300 amps but the breaker triggers at that, I suspect I will have to replace that breaker for a 400 amp one which is the maximum the controller can supply.
The boat performed well and performed as I expected it would, however I have bought a 24 volt blower motor to cool the motor down, I also have a slight out of alignment issue which I will sort next week.
So questions
1/ should I fit the 400 amp breaker or leave it at 300 amps?
2/ should I test it without the breaker to see what the motor really does draw at speed?

3/ Is 72 degrees to hot after an hour or is it normal? will running cooler help performance and life of the motor
 

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So Yesterday I had a trial run, it performs well draws 52 amps 3.3KW at approx 3mph, the temp of the motor was 72 degrees C at the end of an hour run, controller was 32 degrees.
are you measuring motor amps or battery amps?
did you measure RPM?
dit you measure motor voltage (should be pretty linear to RPM)

it sounds like it's working well! 72 degrees C was measured on the outside or the rotor / stator windings? I bet you could smell the motor ;)

1/ should I fit the 400 amp breaker or leave it at 300 amps?
2/ should I test it without the breaker to see what the motor really does draw at speed?

3/ Is 72 degrees to hot after an hour or is it normal? will running cooler help performance and life of the motor
cooler is better, try the fan. this also depends on how the motor is mounted (free flow of air or restricted)

I like to be able to draw full power for a short period, maneuvering (stopping!) needs power. you could make some 'spring return' on the throttle lever so it doesn't stick to full power.

Check the controller specs on continuous power rating.
 

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I was measuring Motor amps cant, as yet measure RPM but will do as soon as I can work out how to do it reliably.
The fan will be here towards the end of the month, the motor has lots of air and room to breath in but as you say cooler the better so fan will be fitted.
I will do a trial to see how many amps the motor draws flat out, I want a cut out in the wiring, as if some rope gets caught in the prop it will cut out as the amps rise.
 

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are you measuring motor amps or battery amps?
did you measure RPM?
dit you measure motor voltage (should be pretty linear to RPM)

it sounds like it's working well! 72 degrees C was measured on the outside or the rotor / stator windings? I bet you could smell the motor ;)


cooler is better, try the fan. this also depends on how the motor is mounted (free flow of air or restricted)

I like to be able to draw full power for a short period, maneuvering (stopping!) needs power. you could make some 'spring return' on the throttle lever so it doesn't stick to full power.

Check the controller specs on continuous power rating.

So I have ordered a tacho kit which is easy to fit, wont be here until the beginning of next month. At full throttle the motor is running at 370amps! I will be I suspect be repitching the prop to enable it to spin at aprox 2000 rpm. In the meantime I am fitting the steering wheel and hydraulics to convert it from a tiller. I will let you know how things go when the tacho kit arrives and can tell you what its current motor RPM is;)
 

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Thanks for those, great videos, did you ever get out from under that bridge? I had, like you thought of doubling up on motors, it seems from that video they work very well together. We will be taking a video shortly so I will post it for you
 

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Ah yes, but while doing steel-work on the boat, it was nice to be out of the rain...and with hot weather it was also a perfect work location. (only west / east winds could get chilly)
Cant fault you, on a number of occasions whilst getting soaked, I have wished for an instant boat shed!
At the moment I have a problem with vibration on my drive flange to the propshaft, it is running very slightly off center and its driving me mad! Tomorrow I am going to visit propshaft technology in a hope that they can sort it out for me. I do have a centraflex coupling that removes some out of balance issues, but bearing are easily damaged so an expert is required in this case
 

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Ah yes, but while doing steel-work on the boat, it was nice to be out of the rain...and with hot weather it was also a perfect work location. (only west / east winds could get chilly)
Right everything is back and assembled tacho connected, the motor spins at 933 RPM flat out, my prop is 19 x 10 if I remember right, the motor should spin at 1600 rpm so what do think for a repitch? 19 x 7? or maybe less even. Look forward to hearing your thoughts.

As an afterthought the prop used to spin at 1500 rpm with the 50 hp diesel so it hasnt lost much in conversion
 

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So today I acquired a 16 x 14 prop, I have decided to give it a go and have been removing the prop through the weedhatch, so much fun as you probably know, I will post the result next week when I get the old prop off with the puller!!!:mad:
 

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So in the end I cut down my original prop from 19 x 10 to 16 x 10 ish, this achieved a good upping of the RPM. I have been out for a run from Rotherham to Sheffield and the boat performed well, the batteries recharged from the solar quickly enough to make the boat fit for what I want which is 2 -3 hours cruising daily. I have to fit some change over switches so that all the solar can be for drive or domestic use, which is a job for next week.
 

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So its pretty well sorted, I had a high pitched whine from the motor after about 7 minutes, I stripped the motor out and stripped it down, it has been reconditioned, but I changed the bearings and removed the fan as it was slipping on the armature. The cooling is taken care of by an electric blower, and the removal of the fan has increased the airflow through the motor.
The whine is still there but looking at some forums and talking to Cedric Lynch he seems to think its the pwm curtis controller that is causing this, its a frequency thing he says, only time will tell if it is a problem. In the end running this motor at a nominal 60 volts it using 24KW 381 amps flat out cruising is achieved at about 3KW so the conversion is a success for me :cool:
 
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