Model Boat Mayhem
Technical, Techniques, Hints, and Tips => DC Motors (Brushed) and Speed Controllers => Topic started by: Coxn John on February 15, 2015, 06:13:45 pm
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Today my 20amp speed controllers fried all wiring to the motors AND the motors, im very lucky the whole boat didn't catch fire, severe cable melting took place, please advise me.
New motors im fitting now are 6volt RS-550SH brushed motors
Battery power is 6volt 12amp/hour
What amp speed controllers do I need ?
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always fit fuses then you wont have that problem again.
mike.
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What size propellers were you using?
{:-{
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What size fuse would you fit please ?
Im using 50mm props (which the motors previously had no problem with using mechanical power controllers)
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What size fuse would you fit please ?
The spec sheet I've found says they draw about 6A at max efficiency, could be a bit more if not best, say 10A.
Stall current is about 50A.
To be safe I guess you'd need a 50A controller (depends if it is specced as stall or running), but I'd use a 10 or at most 15A fuse (per motor).
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Thankyou, i'll search for 2 x 50amp controllers, probably go for the 'Tornado' ones from Howes unless anyone has any suggestions re others
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Ok WHAT make was the speed controllers you were using.....Personlly I would NOT use the tornado esc's as it's chineese Amps that you are dealing with use ACTion 20 amp ones obviously using fuses of 15amp
Dave
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The ones I was using were 'RCmodelparts 20 amp'.
Im surprised you say use 20amp again Stavros, as it seems something was overloaded (to burn out wiring & motors) surely it was the controllers no ?
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ACTion appear not to do one for my voltage with BEC, as space is at a premium I need BEC.
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I would get one of these find out what amps you are pulling easy to fit then bung the boat in the bath. less than a tenner Paper readings dont apply to our models http://www.4-max.co.uk/gt-mini-voltage-current-meter.htm (http://www.4-max.co.uk/gt-mini-voltage-current-meter.htm)
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Thanks Jaymac, sensible idea, I will.
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Hi John
If you had no trouble up till today, is it posible you picked up some weed or line round the props?????
Had no problems with the Tornado ESC and the similar blue ones, but as Stavros said they are chinese amps. Only go back to the water after testing your current draw, 550's can be thursty beasts, but a 15 ah fuse should be more than adequate
Mark
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John
As has been said it isn't speed controllers which fry wiring - it's the load on them. Don't dismiss ACTion ESCs because they don't have BEC. You could fit one of these pretty much anywhere and it will do the job better than any one fitted inside a speed controller http://www.componentshop.co.uk/3a-max-5a-universal-battery-eliminator-circuit-ubec.html (http://www.componentshop.co.uk/3a-max-5a-universal-battery-eliminator-circuit-ubec.html)
DM
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Just to state the obvious, fuses go between the battery and the ESC.
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There was nothing round the props,
Iv ordered a 'current draw tester' as recommended -)
One more snag that's raised its head, many of the speed controllers are only 20% power in reverse, that's no good for this boat as its props are a matched pair, so left (port) prop is always in reverse, so im still searching for affordable speed controllers which will work....eeeee I hate modern technology, bring back mechanicals, Bobs Boards all is forgiven !
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Hi John
Rather than run one speed controller in reverse to achieve contra-rotating props could you not just switch the +ve and -ve wires on the relevant motor and then run both controllers in forward mode with the motors running in the desired direction of rotation?
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If the ESCs survived the mellting of the wire to the motors, there is nothing wrong with the ESCs other than that they can probably handle a lot more current than they need to. The wire needs to be heavier, or it will act as a fuse (which is a bit of weak wire that melts when you pass too much current through it). If running two motors in parallel off one ESC, each motor needs its own fuse. Otherwise, a fuse is only really needed between the battery and ESC. Fuses are not really there to protect what they are feeding, they are there to protect what is supplying them, and, by preventing fires, what is surrounding them. Most ESCs today incorporate some form of current limiting, so don't need any fusing between themselves and a single motor, but a high rated ESC might well be capable of supplying enough current to do damage in a fault situation.
If the motors got fried, and the system is running on the same voltage, there is something severely wrong with the mechanical setup causing the motors to stall, or go into a near stall condition when they will pull a lot more current.
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only 20% power in reverse, that's no good for this boat as its props are a matched pair, so left (port) prop is always in reverse, !
May be wrong John but the fact the prop is handed and wired to run in reverse to its neighbour methinks does not matter to the speed controller its sending out forward polarity to both
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'cuppa' I hadn't thought of it like that, yes, that's what I was doing....
'malcolmfrary' The wires melted right up to the ESC so cant use em again, mostly only bare wires left ! Iv ordered 2 inline fuses which I intend to fit between ESCs & battery, correct ? Props etc seem fine, still turn ok, but they'll have to come out anyway to fit new motors.
'jaymac' Yes, I'll need to pay special attention to that when refitting.
Thanks guys, mostly got in my head whats needed now, but would appreciate you all telling me what makes of ESC (with BEC) you all recommend, or have had probs with, please.
John
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So Far Mtronics in 5 boats seem ok the chinese 50 amp had 2 go bananas as did a Graupner which put my PT boat full astern one third submerged.You might also consider for trials the mini circuit breakers at Maplins less then Ģ2 each 10A and auto reset bout the size of you thumbnail and about 1/4''thick
http://www.maplin.co.uk/p/100a-auto-reset-circuit-breaker-ak13p (http://www.maplin.co.uk/p/100a-auto-reset-circuit-breaker-ak13p)
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Thanx jaymac, iv just studied their Viper Marine range, looks good, but having ordered a 'current draw meter' now i'll wait until iv done a test with that before I decide which one. Im gonna avoid all the cheapies, theyre too much hassle, + if you could see how little room iv got to work in inside the boat you wouldn't want to do it twice...this will be my 3rd 'empty the hull' session >>:-(
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Even if some others told you, Iīm going to repeat it.
It seems that there is nothing wrong with your ESC if the wires and motors died of overcurrent.
Itīs impossible for the ESC to fry anything, itīs the motor that draws the amps.
Generally 50mm sounds too big for a standard 550 motor. If these are brass props with high pitch your motors will die again, this is way too much load on them.
Youīll need low rev motors for such a huge prop.
In what kind of boat are you using them? Pure displacing hull, half gliding/gliding?
If itīs a fast gliding boat, just decrease the size of the props.
If itīs a slow displacing hull, youīll probabaly need low rev motors.
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Brass props, on the Lifeboat shown in my profile pic, but the motors were fine with those props before I upgraded to ESC & 2.4gig
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The props are definetly much too large.
35mm would fit and produce maybe 1/4 load at same speed of the boat.
I cant explain why it worked with other ESC (or did you use those 80's variable resistor controllers??) but your motors are definetly overloaded.
These large props work like a brake on your motors (since the hull canīt go as fast as it should be @ 10.000 rpm > 20 km/h with those props, hull will maybe run half of it) and increase the amps.
Different ESC will not help anything, the motors will go up in smoke again!!!
If you want to use the 50mm props you need bigger motors with slower rev.
E.g. Robbe Power 755/40 (but @ 12V).
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It was on 'Bobs Boards' if you remember them
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Its not supposed to be fast, the real boat only managed 9 knots
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I thought it would be half gliding at around 20 knots :embarrassed:
The motors are even more wrong with a displacing hull.
You should get motors which make 3000 1/min max at 6V.
Something like this should work perfectly
http://www.componentshop.co.uk/mabuchi-555-dc-motor.html
Or you try motors with "better quality" like Buehler or coreless (Faulhaber...)
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Thanks Tobias, i'll certainly explore your link
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Tobias, are you saying buy these 12volt motors but run them on 6volt ?
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Yep, why not?
Rpm looks good on 6V.
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Ok, just wanted to check, sounds like a win win idea to me :)
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Right, iv ordered those :}
Now tell me which ESC (inc BEC) you would use on this set-up please Tobias ?
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I should say ESCs cos i'd need 2
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Well I don't know your suppliers in the UK so well.
But these motors will probably draw less than 3-4A depending on the weight of your boat.
So everything above 10A rating should be fine.
If you are open to order in germany I'd use those here
Www.modellbauregler.de
http://www.modellbau-regler.de/shop/product_info.php?products_id=90
These are the best ESC I know, since their PWM frequency is above what you can hear.
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Boat weighs about 15 pounds (prob about 8kg).
Im not unwilling to order from abroad but don't speak german so a language difficulty, but my g/f will know how to google translate it, as long as they will post to UK ?
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Mtronic Marine Viper 15 is fairly universally available, easy to set up, not overly expensive, compact and reliable. Just the usual caveat that when using more than one, the red wire of the servo lead should be disconnected on one of them. They do run in the audible range, personally I don't mind that - it lets me know that something should be happening.
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One of the very best ESCs on the market IMHO http://www.microgyros.com/ (http://www.microgyros.com/)
Mike prefers a telephone call to an E-Mail.
DM
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Boat weighs about 15 pounds (prob about 8kg).
Im not unwilling to order from abroad but don't speak german so a language difficulty, but my g/f will know how to google translate it, as long as they will post to UK ?
@8kg you can count with around 20-25W to bring the boat to hull speed, so probably 3A per Motor.
Iīm sure that Michael from modellbauregler.de will speak english and probably also post to UK.
If you need a translation to german just send me a PM.
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malcolmfrary, Not sure what you mean by 'disconnect servo lead' Why ? How will it get its independent control ? Does this apply to ALL makes of ESC ?
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Coxn John , all Malcolm was explaining was , remove one red wire from one of your two speed controllers.
http://www.mtroniks.net/download.asp?ResourceID=1945
The above link may help you understand a little better . I use the fr40 micro gyro speedos as suggested above , and also various other Acton products ( good on yer DM :-)) )
Aid
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Thanks Aid :-))
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Hi John
Disconecting one red wire is needed so that you dont get 2 BEC feeds to the reciever, dont cut the wire just release the tag on the plug and withdraw it from the plastic holder.
Mark
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Hi John
Disconecting one red wire is needed so that you dont get 2 BEC feeds to the reciever, dont cut the wire just release the tag on the plug and withdraw it from the plastic holder.
Mark
And tape it back along the servo lead so it is insulated
Ned
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A picture is worth a thousand words - as long as they're very cheap words...........
( Disabling Battery Eliminator Circuit BEC / ESC)
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Thanks Inertia, that's good
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Inertia
My reply was ok but what is the purpose, IE what does the double red wire cause????
Mark
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Inertia
My reply was ok but what is the purpose, IE what does the double red wire cause????
Mark
The BEC is there to supply a stable voltage to the system. Due to manufacturing tolerances, each one is likely to be a few minute fractions of a volt different to all the others. Each will "see" the others voltage and try to regulate it. Even though it might only be a millionth of a volt or so, it can wind up being fatal to one of them. Since the regulated voltage only appears on the red wire, that is the one to disconnect on ONE of the ESCs. The ESC with the disconnected wire still works because it has its own BEC to work its own electronics.
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So now i know!!!!!
Thanks for keeping it simple(like me)
Regards
Mark
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UPDATE -
This post taught me a lot about electronics & their tricks, a BIG THANKYOU to all you guys who participated, especially Tobias :-))
The Lifeboat is now working (yet to try on water but I don't forsee a problem as the props appear to be spinning fast enough).
What Iv ended up with is Mabuchi 12volt motors (555) running on 6volt power, ESCs from Modelbauregler in Germany, & each one fitted with its own 15amp blade type fuse.
Thanks again guys :}
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Full test on our lake carried out today, excellent result, & more controllable than before :-))
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Where's the photos ????
Ned
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Here you are Ned
https://www.youtube.com/watch?v=xjV60nQhvXw&list=FLwMRcD9BzgL0F8YklzGjz1A&index=3
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Looks good John
Ned
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Thanks Ned, I'm pleased with it :)
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Hi John
Looked superb, wonderfull finnish, slight worry that you may lack a bit of power in strong wind????
Scale speed they were never ment to be speed boats, well done great job
Regards
Mark
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Haha, tell you what Mark, if theres a strong wind, I'll tell the Coastguard I aint going... :}
The real boat only did 8 knots (9 after being re-engined) so I never wanted it to be fast, & having been to sea on the real one twice, & also on 37-03, 8 knots up the side of a 25 ft wave is quite fast enough for my stomach :-))