Model Boat Mayhem

Technical, Techniques, Hints, and Tips => The "Black Arts!" ( Electrics & Electronics ) => Topic started by: Jezz2258 on February 12, 2017, 12:27:38 pm

Title: fuse blow
Post by: Jezz2258 on February 12, 2017, 12:27:38 pm

could any of you wizards out there please help an electrical novice ?

I have built a Fairey Huntsman 49" all wooden hull model boat and in stalled Action Electronic gear to run the boat and installed as per their wiring diagrams
the set up consists of-
2 600 M-tronic motors with 40mm props
P94 duel esc/mixer controller
P102 power distribution  board
P103 parallel power board
(the P94/P102 & P103 are contained in a waterproof enclosure.)
2x 12v 7Ah SLA batteries.
I have bench tested and all runs fine, I have not tested in open water yet but I have built a test tank ( 6" longer than the boat) and tested it in that.
the problem is that the 25A fuse blows at 3/4 throttle after 30 seconds.
could this be down to the fact that the boat is not able to move as much water in the tank as opposed to open water? causing more load on the motors.
The P94 has a 25A fuse for the power in and 2 20A fuses for the motors
why should the 25A fuse blow before the 2 20A fuses on the P94 PCB?
or have I wired up something wrong?
Title: Re: fuse blow
Post by: malcolmfrary on February 12, 2017, 03:39:17 pm
The two 20A fuses can each handle 20 amps.  If they are both pulling 20 amps each, thats 40 amps, which is more than 25.  To blow quickly, a fuse usually needs a lot more current through it than its rating, so if the total current is just a bit more than 25 amps, the fuse will take time to heat up enough to blow.  With the right current, about 30 seconds.
Title: Re: fuse blow
Post by: Mark T on February 12, 2017, 04:05:01 pm
I think a few pictures may help if you can post them.  If you are blowing fuses then too much current is being drawn.  This could be so many things such as the incorrect size wiring, a tight or binding propshaft or just plain old poor connections.  Get some photos up so that we can see your setup  :-)
Title: Re: fuse blow
Post by: John W E on February 12, 2017, 04:53:48 pm
Hi there

There are a couple of things I can think of that may cause problems - the first one is - if its the MTroniks M600 brush motors that I have just googled the stall current is 48 amps at 12 volts - so those motors driving a 40 mm prop I should imagine (off the top of me head) would be pulling something between 15 and 20 amps each.    very little there for amperage movement.   Have you had an amp meter on the motors when its been under test in the bath? to see what amperage is being drawn by the motors?    The second thing which you mention is that you have everything in a sealed container, is there sufficient air movement around the P94 mmmm cant remember what you call them - but it will come in a minute - heat sinks which stick out of the top of the casing or the P94  these must have adequate ventilation because they will be getting quite warm for the size of motors you are using.   If these output transistors which are connected to the heat sinks get too hot - they will go into thermal shut down if you are lucky :-)   Just a couple of things to look at.    Make sure you have ample ventilation.

Title: Re: fuse blow
Post by: Jezz2258 on February 12, 2017, 05:25:19 pm
ive had a look at the data sheets for the 600 and 500 motors and the 600 does draw more amps compared to the 500 motor, could be the motors.
there are no heat sinks on the esc/mixer protruding, so keeping it cool and waterproof could be another problem.
show me how to connect and ammeter please.
props run free and are well greased.
14swg wire used through out
Title: Re: fuse blow
Post by: John W E on February 12, 2017, 05:53:03 pm
hi there,

The box you have on its side, should have 2 metal tabs sticking from the top - these are the heat sinks - unless they have been removed.    If the box doesn't have, it may be the smaller version and its not the P94 - but I am going to check - the smaller version wouldn't handle the amperage of the motors.

/// Back from investigation :-)

The smaller version of the ACTion speed controller mixer is the P94 Lite - this doesn't have heat sinks on the top - but will ONLY HANDLE 10 amps per channel and if this is the version you have, I am so sorry but it will be no good for the motors you are running and those props.
Title: Re: fuse blow
Post by: Jezz2258 on February 12, 2017, 06:02:43 pm
agree, its the p94 lite
might give action electronics a call see if they can recommend an upgrade, or try smaller motors
Title: Re: fuse blow
Post by: John W E on February 12, 2017, 06:12:10 pm
Hi Jezz

you could try the 20 amp version of the P94 but before buying speed controllers do an amperage test on your motors.    To do this, you need an amp meter or a volt meter that has an amp meter reading on it of somewhere in the region of 20 amps.  Disconnect all your electronics from your motors, so you are only left with 2 wires from each motor; select the motor to measure the amps from; one side of the amp meter wire goes to the motor terminal - the other wire from the amp meter goes to the positive side of the battery.  The negative terminal on the battery is connected to the other terminal of the motor - thus completing the circuit.    Now, with the motor running - place in the test tank (bath) and see what amperage is drawn on the amp meter scale.

If you do a search of this forum there are numerous topics covering measuring amperage & wattage draw of motors in boats.

Title: Re: fuse blow
Post by: John W E on February 12, 2017, 07:07:52 pm
Hi ya there Jezz, have a look at this article written by Dave M the old man :-)  --  it explains an awful lot about electronics in a model and how to measure things such as amps and volts :-)  :-)) :-))'t-understand-electronics/18054

Title: Re: fuse blow
Post by: Jezz2258 on February 14, 2017, 08:08:46 pm
Thanks bluebird, very interesting, thank you for the link.
Waiting for the weekend to connect up an ammeter to check the motor draw, might be a bit scary putting the motor to full speed in a test tank.
Had a word with Action and they seem to think it could be down to the motors and to keep an eye on the P94 for over heating.
Last option could be to sell the P94 Lite and up grade to the 20A version, i would like to keep the 600 motors for the planing effect, i dont know if 540 motors would do the same. Precedent recomend a single 700 motor.
Ive redesigned the forward compartment to a splash proof one and incoperated a 40mm 12v cooling fan from a pc to draw air off the electronics over the motors and out through the air intakes and upped the wiring to 12awg, over the top but its what we yorkshire men call " belt & braces".
Will keep you posted.
Title: Re: fuse blow
Post by: Jezz2258 on February 15, 2017, 05:55:50 pm
right , done some testing with my ammeter. could nt wait till the weekend
the data sheet for the 600 motor states-
no load   1.2 amps
at max efficiency  5.9 amps
my results - on the bench give or take 0.2 amps for both motors
motor on its own  2 amps
motor and prop connected     7.5 amps
in the test tank- ( boy it was scary)
full throttle straight from the battery.........................................................48 amps   %%
I don't think the tank is big enough. the water at the stern has no where to go and causes a vortex
the tank is only 150mm longer than the boat.
Title: Re: fuse blow
Post by: Mark T on February 15, 2017, 06:27:16 pm
So you just need a 50 amp fuse and its sorted  %% %% %% %%   Only joking  {-)  but at least now you know what the issue is
Title: Re: fuse blow
Post by: John W E on February 15, 2017, 06:53:59 pm
hi there

Just been re-reading through the postings and a couple of things have just come to mind - are you using lead acid batteries?  or, SLAs.   If so, these are going to be a little too heavy for your boat.   Also, the amperages that the motors are drawing - they aren't going to last physically very long before they go 'pop' - better off with NiCads.   

Also, how about dropping the size of your prop down to say 35 mm - your speed controllers ACTion don't do one that is going to handle 40+ amps per motor - you may be looking at Chinese speed controllers - from Ebay or somewhere - unless you can reduce the amps.

Title: Re: fuse blow
Post by: malcolmfrary on February 15, 2017, 07:08:31 pm
Looking at the motor spec - - I would guess that the motors are overloaded with 40mm props.  35mm tops, probably better with 2 blades.  A bit less acceleration, more top speed if it can get there.  Less weight will help speed.  Lose the SLA ballast and replace with NiMH.  Even a lower nominal AH rating will give better performance due to firstly weighing less, second by being able to sustain a higher discharge rate without damaging themselves.  Smaller props spinning faster will give a longer run time as well, another benefit of reducing the current draw.
Title: Re: fuse blow
Post by: Stavros on February 15, 2017, 09:02:11 pm
1. Bin the motors (they are flea-market crap) and the batteries (fine for home alarms and tugboats; too heavy and gutless for anything else, especially a Huntsman 46").

2. Sell the ACTion stuff or keep it for another model, because it's not appropriate for the power train that this one needs.

3. Fit 2 x brushless motors, 2 x brushless ESCs and 2 x LiPo batteries. Suggest 1300-1800W total.


Title: Re: fuse blow
Post by: chas on February 15, 2017, 11:40:49 pm
Jez, here is what I would do, and I run similar models.
1. Follow Malcolm's advice, he is correct on all counts, the props and the batteries are the first things to address.
2. If, when the model is running correctly you want more performance, consider brushless, come back on here and ask about motors.
3. I get the performance I want, I.e realistic in my eyes, not " bat out of hell"  with a similar set up. Brushed motors, NIMH batteries, and keeping the weight down works for me.

Title: Re: fuse blow
Post by: Jezz2258 on February 16, 2017, 08:29:24 am
What size NiMh batteries do you run?
Title: Re: fuse blow
Post by: Stan on February 16, 2017, 09:52:47 am
I do not agree the motors are Flea Market Crap after all there are lots of motors out there that could fit that description. In essence its all about doing you homework on you motor  then matching you speed controllers, prop sizes and battery type for your model. I have to agree that lead acids are fine for large slow scale models  but not for a model that needs a fair  turn of speed. Reference the question on NIMh batteries they are normally sub c size and the voltage ranges from 4.8 volts to 12 volts and the highest capacity is 5 amps. You can get bigger cells up to 9 amps but again its trial and error. Check out the Component Shop web site they offer a good service on batteries.

Title: Re: fuse blow
Post by: chas on February 16, 2017, 06:45:38 pm
Hi again Jez , I use 4.6 and 3.3 ah packs, from component shop. They are very popular with lots of us on here.
 For the record, I don't think the motors are crap either. My compliments on your deck, nice job.

Title: Re: fuse blow
Post by: John W E on February 16, 2017, 07:38:19 pm

I don't think there is anything such as a poor motor - just a motor which is being used for the wrong purpose and in the wrong environment.   We had a discussion on this forum a long while ago and it was discovered that there are basically 2-3 manufacturers of these canned motors.  One of the leading manufacturers was Johnson - so basically Companies such as MFA, Graupner and other companies like that would purchase the motors from say Johnson by the thousands and re-classify them.   Basically the motors that you see cheaply on Ebay will probably come from the same manufacturers - but haven't been classified correctly.  The motors which are being used in this model are adequate for it, and will do the job.   

It is the speed controller section which has been misunderstood by the owner - maybe the owner was under the impression he was buying a higher amperage speed controller and his understanding of the batteries wasn't up to scratch and maybe he has been now pointed in the right direction.  We all learn and have made similar errors.

If we go on to Ebay there are several speed controllers which can do the job.   The thing is, you have to purchase a separate mixer from ACTion if independent mixing in the model is wanted.