boatman's 1/72 HMS Tiger C20 build

[boatman]

I think you are kinda going at it the wrong way there Chris……..if you just up the fuse you are potentially going to melt the cabling and damage other things on the circuit. The fuse is there to protect the cabling and stop items being given too much electricity.

Give me the numbers and I’ll do the maths for you if you want……

What voltage is the system?
What wattage are the motors?

As W = V x A then A = W / V. To get the required fuse amperage just divide the motor wattage by the system Voltage, and there you go……

If the motor won’t run on the fuse amperage that this gives then there is something wrong with the motor.

HI Tim the voltage is 12v 12amp hr batt an ESC is rated at 320 amp an motor info is on the box in picture below an wirein is very heavy duty so i think ive covered your qeustions now can you give me an answer ?
CHRISB

[boatman]

Remember it quite well. I used to be an installation electrician. But that was a lifetime ago. And there is a whole lot of difference between Electrician and Electronics Engineer. lol
But OK 40A sounds a lot but I guess over the 4 motors that is only 10A a piece... Maybe an single inline per motor could point to one defect motor and save Chris a few bobs.
But as you wrote we need the power table for the motors or just which motors they are would help. 261 pages is a lot to wade through to find the info...



What does Tiger weigh in at sailing weight Chris? Which motors do you have? Who big are the props? Big props need low speed and high torque.

HI Ian well im afraid you got that wrong sorry but there are 2 x 40amp fuses in the fuse box an that is one 40amp fuse for just 2 x motors an then again another 40 amp fuse for the back motors an they have not blown a fuse its just the graupner 600 speed motors that are causein the 40 amp fuse to blow an you have got me an how heavy tiger is but lets just say she is very heavy an prop size are 33mm x 4 how's that ?
chrisb

[Ian M]

So a 9.6v motor on a 12v battery..... Could that be the issue?
Looking at the motors you have given the info on I Would say that they are under rated for the system. As it says on the box you posted nominal 8.4v operating range 6 and 9.6v If you are feeding them 12v they are not going to play nice but you know that.
I would suggest a look at these from Krick. Max POWER 500.

https://www.krickshop.de/MAX-Power-500-electric-motor.htm?shop=krick_e&SessionId=&a=article&ProdNr=42246&p=354

Pretty sure you can find them in the UK as well

I did not know that it was two motors per fuse and only two of the motors that are blowing fuses. (just guessing on the info given). Are the motors different form the ones that do not blow the fuse?

[boatman]

Chris, what actually drives the motors? Is it the ESCs? I'm surprised they don't have current limiting built in.
Pete

HI Pete well 12v 12amp hr batt is the power an it goes through the fuse box an 40 amp fuse an then to a 320 AMP ESC then to the motors best i can exsplain it
chrisb

[Tim Marlow]

HI Tim the voltage is 12v 12amp hr batt an ESC is rated at 320 amp an motor info is on the box in picture below an wirein is very heavy duty so i think ive covered your qeustions now can you give me an answer ?
CHRISB [ATTACH=CONFIG]n1202963[/ATTACH]

Gives me more questions than answers really Chris. You seem to be running 8.4 volt motors on a 12 volt system? They will therefore be able to draw much more current than they are designed for and quickly take damage. Are you sure that isn’t the root of your problems? What is the spec of the back ones that work successfully?

[boatman]

So a 9.6v motor on a 12v battery..... Could that be the issue?
Looking at the motors you have given the info on I Would say that they are under rated for the system. As it says on the box you posted nominal 8.4v operating range 6 and 9.6v If you are feeding them 12v they are not going to play nice but you know that.
I would suggest a look at these from Krick. Max POWER 500.

https://www.krickshop.de/MAX-Power-500-electric-motor.htm?shop=krick_e&SessionId=&a=article&ProdNr=42246&p=354

Pretty sure you can find them in the UK as well

I did not know that it was two motors per fuse and only two of the motors that are blowing fuses. (just guessing on the info given). Are the motors different form the ones that do not blow the fuse?

YES Ian the ones that dont blow the fuse are johnsons motors right up towards the rudder an the ones that blow the fuse are the graupner 600 motors but i think i will replace the johnsons as i dont think they are powerfull enough to power tigers wheight thats why im goin to get new 4 x new more powerfull motors if you get my meaning
chrisb

[boatman]

Gives me more questions than answers really Chris. You seem to be running 8.4 volt motors on a 12 volt system? They will therefore be able to draw much more current than they are designed for and quickly take damage. Are you sure that isn’t the root of your problems? What is the spec of the back ones that work successfully?

HI Tim the johnsons motors are the ones that dont blow the fuse an i cant tell you the specks as they come in a box with no intructions an ive used the grapner 600 ok in my nimtz an my norfolk so they should be ok but they are not direct drive as they are MFA mounting fitted in a cambelt drive so it 3 to 1 ratio an they go great only trouble is that ive only got one pair of cambeltdrive enough for 2 motors an not 4 as they are not made anymore
chrisb

[Tim Marlow]

Just did a fag packet calculation in my head…..do you know that each of those Groupners can stall at around a kilowatt each on their rated current…..added together that’s as much a draw as a two bar electric fire…..at best efficiency they each draw like a 100watt bulb.
If you are going to swap them out I would look for 12 V replacements. They should at least match your battery current then, and should simplify problem solving.

[Tim Marlow]

Don’t ya just love it when greenies talk dirty!!!

Er….what’s a greeny? Don’t mind being insulted, but it doesn’t really work if I don’t speak the lingo……

[Ian M]

If you are going to swap them out I would look for 12 V replacements.

Or at least a voltage regulator/limiter someplace between the power source and the motor.
What do you recon on the motors I linked to Tim? I read that they can handle a screw of upto 100mm so they should be able to handle the 33mm screws on Tiger in their sleep.

[wotan]

Congratulations Chris on a successful project launch.

John

[Tim Marlow]

Or at least a voltage regulator/limiter someplace between the power source and the motor.
What do you recon on the motors I linked to Tim? I read that they can handle a screw of upto 100mm so they should be able to handle the 33mm screws on Tiger in their sleep.

They look more suited to direct drive than the Groupners, revving much slower, so wouldn’t need the belt drive step down. They are half the power output….but if they are more efficient at converting that power into thrust than the Groupners (which are 75%), and are direct drive, which would also increase efficiency, then they could close that gap quite quickly. Trouble is, it’s poor old Chris’ wallet that has to play suck it and see…..

[Waspie]

Er….what’s a greeny? Don’t mind being insulted, but it doesn’t really work if I don’t speak the lingo……

Ok - ok, Sparky then!!!
Bloody civvies!!! :rolling: :smiling3: :smiling3: :smiling3: :smiling3: :smiling3: :smiling3: :smiling3:

[tr1ckey66]

Hi Chris
Tiger looks simply fantastic on the water - a magnificent and graceful looking model. Looks like you had a great day for it too.
It’s a shame about the fuse/motor issue cutting short the maiden voyage but I’m sure you’ll get it sorted.
Hope all is good with you and I’ve fingers crossed you’ll sort the motors in quick time.
All the best mate
Paul

[stillp]

HI Pete well 12v 12amp hr batt is the power an it goes through the fuse box an 40 amp fuse an then to a 320 AMP ESC then to the motors best i can exsplain it
chrisb

Chris, could you give me a part number for the ESC please, so I can find the full specification?
Pete