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[treeboa]

right guys,im converting a 1/35 schnellboot, i have mounted three motors to the shafts, outers a pair of mtronics 400`s and the center an re380, eventually got the wires right to give me two rotating clockwise and one anticlockwise - how i could spend thirty mins with three pairs of wires and only after swearing get the correct rotation is beyond me but it happened  , anyway im in the postion were i have two new esc`s i can use, i know in therory as long as the combined draw is lower than the max of the esc im ok, however im wondering if having it running three motors if one or the other would be the better option, both are brand new,  the options are
mtronics viper marine 25 amp  or a ripmax `xtra` quantum ( which if the blurb is to be believed is 128amp !!)

which ever esc i use the other is going into a still to be finished robbe PT-15 thats carrying a robbe 600/24 motor/gearbox

[Tug-Kenny RIP]

Are you suggesting that you want to use only one ESC to control all three motors ?

Ken

[treeboa]

yep just the one, ive had both linked on and had the motors/props revolving in the correct rotation +2 -1, both work in forward and reverse,the 2mm shafts are  turning graupner 30mm plastic 3 blade props,2mm less dia and a lot less pitch than the correct to scale props ,ive had its bum in the sink and it shifts a lot of water( dont have a bath only a shower in a wet room) 5 mins on a good power and niether the motors or either esc getting hot or even warm really

[Tug-Kenny RIP]

I would be very interested to know the Amps that these three motor pull when in the water. Any chance you could connect an ammeter for us.

I am building a three prop boat and have three ESC units and I would like like to reduce the weight and thought of just one myself.

Cheers

ken

ps         if you upgraded to metal props you would get more thrust, as I believe plastic props torque under stain.

[treeboa]

I would be very interested to know the Amps that these three motor pull when in the water. Any chance you could connect an ammeter for us.

I am building a three prop boat and have three ESC units and I would like like to reduce the weight and thought of just one myself.

Cheers

ken

ps         if you upgraded to metal props you would get more thrust, as I believe plastic props torque under stain.

one thing i dont have is an ammeter 

way it was moving water in the sink - soz out of the sink  i dont think a lack of thrust is going to be a problem, i did a rough as hell way of testing the amps, i have a single 10amp blow fuse on the poss line of the esc to the motors at the moment and even with a snap start to full revs on all three motors it did not blow, not accurate i know but its close enough untill i make a powerboard with triple fuses - 1 to each motor

[wombat]

Just had a look at the Ripmax - no way it will do 128A continuous with that Heatsink - it will be dissipating 10s of watts at full bore even with the best FETs in it. However, it should be good for 20A or so.  Both ESCs will do

If you are using the single ESC, I would fuse the input at 15A and each of the motors at about 8A - that way if one gets weeded or jammed, its fuse will go and you can limp home on the others .

Wom


 

[Tug-Kenny RIP]

Thanks for all the info Guys.  Very helpful indeed.   

ken

[grasshopper]

If you have a voltmeter or multimeter, quick way of checking your current draw is to stick a 1ohm resistor in the line and measure the voltage drop across it - using Ohm's law the voltage drop will the same as the current passing through it - but use the biggest wattage resistor you can find, it could get hot!

[treeboa]

If you have a voltmeter or multimeter, quick way of checking your current draw is to stick a 1ohm resistor in the line and measure the voltage drop across it - using Ohm's law the voltage drop will the same as the current passing through it - but use the biggest wattage resistor you can find, it could get hot!

only problem with that for me is these motors are fed from 7.2 volts, if say the voltage drop is over 7ish then im "xxxxx",  however i have just discovered my multimeter thatdoes amps  dc, lilyann had put it away safe -back the cupboard !!!

wombat - my thoughts that as well, footprint wise its about the same as the viper, maybe its a much copied print error and it should be 28amp, good thing is niether are getting much above warm