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[malcolmfrary]

From the test figures you quote, you should be safe with a 20A ESC, and a 15A fuse in the battery lead.
As a further check, measure the resistance and do a bit of Ohms law to figure the stalled current.  It does sound like if you fit a nice sharp prop any weed/plastic bags/fish/fingers should not be a problem, as it will be minced.

[cassf1]

Hi

Was looking on the net and found this (http://www.robowars.org/wikka/DewaltDrivetrain) says stall current is 250a does this mean i wont be able to use 20a mtroniks marine viper ESC with 15a fuse as i don't expect motor to stall or does ESC need to handle 250a when in neutral.

 Mass = 470g (18.8oz (1.175lb))
- Terminal resistance = 0.072 ohms
- Stall Current = 250 amps
- Stall torque = 2.1Nm
- No load current draw = 2.6 amps
- Peak Power = 1100w
- Peak Efficiency = 81%
- DeWalt Part # = 393111-01
- Voltage = 18vdc (can be overvolted)
- Nominal Voltage = 24vdc
- RPM = 22,000 ungeared
- Length = 78mm (3.07")
- Diameter = 46mm (1.8")
- Output pinion = 16 tooth gear
- Shaft = 5mm dia x 7mm
- Torque Constant = 1.2 ozf-in/Amp
- Stall Torque = 300 ozf-in
- Angular-velocity Constant =1100 RPM/v
- Peak Power = 1.5 HP

[malcolmfrary]

250 amps.  The battery will likely not supply this, and if it did, the wiring would object.  Current sensing in the ESC should limit maximum current to a value safe for the ESC, the fuse protects everything at a slightly lower value, but not as quickly as the ESC protection.  If it stalls, everything simply switches off.  If the condition persists, the fuse blows to prevent incineration.  If the motor can be repeatedly switched on and off under load without blowing the fuse, there will be no problems in operation.
There is a difference between electronics and wire warming up - it was truly said that "any transistor will protect any fuse" meaning that the electronics would react by dying first.  A protection circuit harnesses this speed by protecting at semiconductor speed.  To blow quickly, a "normal" fuse takes about 2X its rated value.
This motor will probably be OK, but as Mr Jacket says,for model use, motors designed for use in models usually work better than motors designed for other applications.

[FullLeatherJacket]

As I suspected, this motor is designed to be run through a gearbox - read the remainder of the Robot Wars thing. The no-load RPM without one is excessive for direct drive on its nominal voltage, which itself is relatively high for an average car-boot-sized model. BTW its peak power of 1.5HP > 1Kw, which is one bar of an electric fire. Makes you think, dunnit?
 
Unless you are experimenting with a high-speed model or you have a lot of practical experience selecting and operating DC motors then I would STRONGLY advise anyone to buy a known-brand motor from a specialist model boat retailer. IMHO saving a couple of quid buying an unknown quantity by way of a motor is a false economy unless you really get lucky. One blown ESC will gobble up any saving in a flash (often quite literally.....)

Suit yourself - I still reckon it's best only for ballast!

FLJ

[stallspeed]

 It seems ok for a high power boat motor on 6 volt but seat window and radiator motors are better for the bigger models with big props.
Compare with some of the more familiar model motors in the same olde worlde units here

Without the 2-ratio gearbox it's nothing special nor out of the ordinary.It has the same torque as a model trade motor.You can change the brushes but the spur gear is a pain if you want direct drive.

The bit you missed the bit about the gear train......

GEARBOX SPECIFICATIONS
For Motor # 18v (old style)
DeWalt Part # 380264-13
Input accepts 16 teeth
Output Shape X
Low Gear RPMs 450
High Gear RPMs 1600
Low Gear Ratio 15.3125 : 1
High Gear Ratio 45.9375 : 1
Max Torque 400 inch pounds
Lubrication Grease
Weight 7.25oz or 0.4531 Lbs

[cassf1]

Hi

Thanks for all your advice, i know when its time to listen to the pro's looks like it will be graupner 900BB as i can get one £20.
Do you think this will be best choice for me using sealed lead acid battery 4.5ah

boat spec
1.5kg weight
18inch length
8inch wide
5inch deep

Boat needs to carry 1-1.5kg max

Thanks

[stallspeed]

You may change your mind yet. What is your prop like?

[cassf1]

hi  stallspeed

Haven't got one yet why what you thinking

Cheers

[stallspeed]

The motor power output is dependant on your prop size/pitch.
If your prop was a 30mm low pitch 3 blade you would get away with a cheaper motor and the 900bb might not have the right revs anyway.Prop first then motor and gear ratio follows.

The 900 will probably do the job, but to draw sufficient power you might have to use 12 volts and a big prop whether that is called for or not.
By the way, bec is ok on 12 volts.

[cassf1]

Sorry suppose to say 12v 4.5ah sealed lead acid, so do you think 45mm propeller and do you mean BEC in receiver or ESC
receiver i have is futaba R136F

[Stavros]

Oh for goodness sake throw the dammed thing in the nearest bin and use one of marks motors MMB
Listen to this then 60mm 4 blade prop running on MMB motor does in ACTUAL sailing length 5miles of walking and the batt did no go flat...............FACT
Power...................................Enough for your needs ...FACT
Duration of running.................Well over 5hrs running...FACT



So throw it in the bin as FLJ has said and listen to what the ones in the know have to say.


On average the carper in the uk will not take his bait out further than 100yds BUT in Foreign places distances can vary from 50yds to 300yds.So lets look at this logically shall we.
1500mtrs if I am not mistaken is 1 mile so therefore on a MMB motor you should get 7200mtrs which in real terms lets allow for line drag windage etc so lest call it 6000 mtrs
So therefore if one is fishing in the UK for example with 3 rods as most carpers do you should therefore if fishing at a distance of 100yd get in theory 600 runs out of the boat .3 rods would in theory give you 2000 runs of 100 yds.

Now on average a Carper will arrive at his or her location and bait up and leave till the morning unless a fish is caught.This procedure would be redone in the morning and yet again at the evening and the following morning.this to me would equate to a weekend session arriving Fri evening and departing sun aft.So in total you would use the boat 12 times so it would have travelled a total distance of 1200 yds so in theory you would only charge your boat every other week

So my conclusion is simple get a proper Motor form MMB throw the drill motor in the bin and go fishing





Stav

[stallspeed]

Sorry suppose to say 12v 4.5ah sealed lead acid, so do you think 45mm propeller and do you mean BEC in receiver or ESC
receiver i have is futaba R136F

For a non-scale boat at 12 volt I'd use a 545 and a 30mm prop.
ESC bec is ok at 12 volt,not the receiver bec,  but that depends on what the maker says.

[cassf1]

Thanks again for advice stallspeed, Stavros thanks for the input but think you missed my 3rd last post