ESC

[jimbo68Participant @jimbo68]

I have an ESC which I want to stop from getting wet. I am going to try and make sure no water can get in in the first place but it has just been repaired after it got wet after a torrential downpour of rain. I was going to make a casing for it, probably just out of plastic, but I’m not sure now because of overheating.

The obvious answer is don’t take it out in the rain but it’s a bait boat for fishing and I will maybe want to sometimes.

Any suggestions ?

[Paul TParticipant @pault84577]

Hello Jimbo 

You are correct in your assumption regarding overheating as ESCs do get very hot and would need to be cooled if enclosed in a plastic box, air cooling with a computer cpu fan is an obvious solution but you would have to be very careful to prevent the ingress of water through the cooling air ducts.

An alternative would be to water cool the ESC,as you might water cool an electric motor, by manufacturing a cooling coil or water jacket for the ESC. The downside to this idea is that the cooling would have to be constant and not just when the propeller is turning, for as you might not know the traditional method of pumping cooling water is to position the intake behind the propeller and use the prop wash to pump the water.

The traditional stop and go method of water cooling would present problems to the ESC and so a small water pump would be required, such as a car windscreen washer item, to maintain a constant flow of cooling water.

Paul

 

[ashley needhamParticipant @ashleyneedham69188]

Jimbo, What were the circumstances of the ESC dunking ?? was it the hull filling with rainwater or just rain on the innards while putting bait in or getting it going initially?? perhaps a box enclosure with ventilation holes might stop, for instance, rain ingress while setting up or loading bait/whatever but allowing cooling air in ?? ….    Ashley

[jimbo68Participant @jimbo68]

yeah, thanks ashley, is sits about  2in off the floor of the hull (if it’s called the floor, not up on my  jargon as yet) in like a tray with sides. It wasn’t the hull filling with water that did the damage, I’m certain it got in through its ‘ lid ‘ ???? . The water has dropped onto it.. I have been mulling it over and reckon just putting a ‘sloping roof’ over it so that any water that might come from above it will just run off into the hull. What d’ya reckon ??

[Mike DavidsonParticipant @mikedavidson22772]

Well Jimbo  I guess the solution is one of the ubiquitous little storage containers, Tupperware springs to mind, but our local pound shop has a pretty good range of sealale poly      boxes which I usein conjunctionwith a mastic gun, you know, the brilliant white bath sealer which you can mould with a wet finger, but dries waterproof.  Punch a hole for all your wires to come out from  and use a liberal amount of sealer inside and out  to achieve full watertight integrity after ensuring that all wires are  fully coated at the exit point, and giving the whole thing ample time to set. It’s a good idea to put your radio gear in one tooand your batteries too if it doesn’t make taking them out to charge too much of a dockyard job. Silicone grease MS4 from Midland Silicone is a magic waterproofer, and is available in an aerosol can too.    One last tip, When assembling my boats, I always design a coffer dam as the interface between hull and superstructure to keep as much water out as possible

[jimbo68Participant @jimbo68]

Hi mike, glad you’ve caught up .

Thats probably what I will do. The bloke who fixed the esc said to run the boat and if it gets too hot to touch then don’t enclose it. So I will see how hot it gets first before I do anything.

[Mike DavidsonParticipant @mikedavidson22772]

You have obviously thought a great deal about this little problem my friendand now, you are starting to see the whole picture I agree wholeheartedly about shunting the heat away from the ESC as there is a particularly nasty little animal called thermal runaway where the resistance in a circuit drops the hotter it gets, and as the resistance drops, the current increases. and as the current increases, it gets hotter, so the resistance drops and more current flowsso it gets hotter ad infinitumand the end result is that your output transistors turn themselves into a bit of fag ash on the end of three wires unless you can break the chain reaction, anywhere will do. I suggest that you get a piece of black anodised aluminium heatsink as big as you can fit in your enclosure,and some thermopath paste, smear the underside of your ESC with the paste and clamp it tightly to the heatsink, the paste will conduct the unwanted heat to the alumium fins which will radiate it into the surrounding air. Remember that all power devices need as much help as they can get to dissipate unwanted heat, look at any high power audio circuit and see the heatsinks. An idea has just flashed through my unconscious, and that is to squash a piece of copper pipe against the aluminium heatsink  ,not so that it splits, and put a scoop into the water at the front, and pipe the water through the copper pipewith thermopath to transfer the heat to the exhaust water as it’s left astern  ( sailor speak for behind you.)

[Mike DavidsonParticipant @mikedavidson22772]

You have obviously thought a great deal about this little problem my friendand now, you are starting to see the whole picture. I agree wholeheartedly about shunting the heat away from the ESC as there is a particularly nasty little animal called thermal runaway where the resistance in a circuit drops the hotter it gets, and as the resistance drops, the current increases. and as the current increases, it gets hotter, so the resistance drops and more current flows so it gets hotter ad infinitumand the end result is that your output transistors turn themselves into a bit of fag ash on the end of three wires unless you can break the chain reaction, anywhere will do. I suggest that you get a piece of black anodised aluminium heatsink as big as you can fit in your enclosure,and some thermopath paste, smear the underside of your ESC with the paste and clamp it tightly to the heatsink, the paste will conduct the unwanted heat to the alumium fins which will radiate it into the surrounding air. Remember that all power devices need as much help as they can get to dissipate unwanted heat, look at any high power audio circuit and see the heatsinks. An idea has just flashed through my unconscious, and that is to squash a piece of copper pipe against the aluminium heatsink  ,not so that it splits, and put a scoop into the water at the front, and pipe the water through the copper pipewith thermopath to transfer the heat to the exhaust water as it’s left astern  ( sailor speak for behind you.),  Do make sure that you have not built in any leaks, cos you know what they will do don’t you?and just for you, the floor is the deck, and walls are bulkheads, jus so we don’t leave you behind / astern.           Mike   D

[Vinnie BraniganParticipant @vinniebranigan92297]

Mike, temperature increases cause more resistance, not less.  You have the phenomenon correct, but not the cause.  If what you said was correct, toasters woudn’t work.  Or kettles, electric fires, heaters, hairdryers….the list goes on.

Vinnie

[ashley needhamParticipant @ashleyneedham69188]

Chaps, I am thinking that a bait boat ESC shouldnt really be getting hot at all. Speed cannot be an issue here so even a very modest 15A ESC should be coping with whatevers fitted in said bait boat. I wonder what you do have in there, and if its a bit too powerful you could usefully change it for something more modest. Then there would be no overheating of any components and boxing in these items would not be an issue, if there ever was one. Not that I know much about bait boats, but I think that we shouldnt be comparing them to "normal" scale boats at all, as they are built for a specific job.  They are simply a delivery system for fish food, and need to simply be stable, reasonably manoeverable and have a long endurance (so they last the day without wasting valuable time fishing because you are changing batteries) . As a pointer, it is always best to keep the water OUT of the boat first, and then a simply cover (as you suggested) would be all that it needs to keep the bits dry on initial setup.  I cant recall seeing any tupperware on many boats unless they were powerboat type offshore racers.  Mind you, if you are going down the box route, Tupperware is a great choice.   If anyone wants a party thrown……?   Ashley

[Mike DavidsonParticipant @mikedavidson22772]

Hi Vinnie thanks for joining in, that’s what forums are about, but thermal runaway as I described it is as it was taught to me in the radio school, the direct opposite of superconductors running at absolute zero

[Vinnie BraniganParticipant @vinniebranigan92297]

Mike,

I’m not talking of superconductors. It’s elementary physics.  Students, (in any type of school   ) are often offered simplified explanations to aid understanding. These are then built upon and corrected as knowledge deepens.  Sadly, some students miss the end of the course. 

Vinnie

[jimbo68Participant @jimbo68]

Hi vinnie, right then, I don’t see me having a problem with enclosing the esc. It has a heatsink and as ashley said it hasn’t been built for speed – 3 metres per second top end.

 I may drive it out 150 ft at most so a 300ft round trip every 15 mins is the most work it will have to do. Other times it may be a lot less depending on where I am fishing and how often I am baiting the area. I don’t know what size the motor is but it’s a biggun. Bigger than a 7.2 and its a brushed motor.

It runs off two 6v lead acid batteries (which provide the ballast – Yes Mike ???) and like I said the motor is a brushed motor that is bigger than a 7.2 (by maybe 3/4 inch longer) and this gives me approx 3hrs operating time

[Vinnie BraniganParticipant @vinniebranigan92297]

Aw!  Unfair!   I know Physics, but I know bugger all about boats!

Vinnie

[jimbo68Participant @jimbo68]

know anthing about tupperware ?

[Vinnie BraniganParticipant @vinniebranigan92297]

I have a very nice young lady that does?

Vinnie

[jimbo68Participant @jimbo68]

The mind boggles 

 Tupperware is well known but there is also betterware and rubbermaid.  Betterware may be a little cheaper but have they compromised on quality ?. And I’m not sure about the durabilty of a rubbermaid box ! What does everyone else think ? got an opinion ?

[Penny LeeParticipant @pennylee76979]

jimbo68 wrote (see)

The mind boggles 

 Tupperware is well known but there is also betterware and rubbermaid.  Betterware may be a little cheaper but have they compromised on quality ?. And I’m not sure about the durabilty of a rubbermaid box ! What does everyone else think ? got an opinion ?

Hi fellow early riser,

No opinion on that but you could….

• run your boat in water for a minute

• moisten the tip of your finger and hold it against the two power devices on the heatsink

If  the device starting LM29.. rather than the transistor that your pal replaced that is hot then I’m afraid a lot of hot air has been wasted…..go figure!
Where am I going with this?

[Vinnie BraniganParticipant @vinniebranigan92297]

Why am I thinking Ann Summers?

Vinnie

[jimbo68Participant @jimbo68]

I don’t know Vinnie, you tell me !!  I was talking about plastic containers 

hmmm, I will have a think about that one Lee, this is better than Eggheads or whatever it’s called on the telly.

[Penny LeeParticipant @pennylee76979]

Mike,

I make excuses and leave when that program comes on.

If a part like an LM2940 (battery eliminator chip) is a heat source preventing the use of a hermetic enclosure you can add a 4 pen cell battery to the receiver and the problem goes away.  Your speed control has that option but you need to disable the battery eliminator as per instructions.

Regards

Lee Penny

[60wattParticipant @60watt]

Jimbo,

Your battery eliminator chip has probably fried your drive transistor because you ran it at 12 volts.

Disable it and use a 4 cell receiver pack or use a 6 cell drive.

Tom

[jimbo68Participant @jimbo68]

Not being funny, I am grateful for all the input I have about this problem, but I am getting a bit baffled about a lot of it – some of it is just the terminology. Lamens terms would be better.

All I know is it was the FET which was blown, It’s fixed ( still waiting on the post mind you so I haven’t put it in the boat yet but apprently it’s working fine in a car). The other thing is do I put it in a box to stop it getting ‘dunked’ – which I think I will decide when I have run it and know how hot it gets – not much I suspect because of the size and speed the motor will run at.

I am genuinely intersted in how all the radio system works and what all these bits n bobs are but slowly slowly catchy monkey   Complete Novice plz remember – capital C capital N

[60wattParticipant @60watt]

Hi Jimbo,

I’m not being funny either when I say you don’t make it any easier yourself. It takes a while to search the meagre snippets of info in your various posts and use Google to decypher the munged up part numbers and manufacturer names. It’s a good exercise in detective work,though!

 All the jargon would be in your speed control instructions,complete with diagrams which you could have got by email from Astec.

To put it in layman’s terms would take ages.OK but you did ask for it :-

I’ll try predicting your answers if only to duck the cranks on the forum. I see two varieties on this thread.

Bear in mind everything below is conjecture based on what you might answer to questions.

So you have got a 12 battery? Y/N  

If YES then what powers the acoms receiver? Do you have 4 pencells? Y/N

If NO your speed control is supplying it with 5 voltsthrough the red on the 3-wire connector. If so, that is the root of the problem.To do that (work your boat with one battery) you have a 5 volt supply via an LM2940 or LM340 or 7805 to supply the receiver,servo and all the electronics and relay coils within the speed control.

That device has a thermal cutout that will operate at 150 celcius and so it is placed on an aluminium heatsink. Without the heatsink it can only self-dissipate 2 watts and supply 250mA (1/4 amp) when its input voltage is 13 volts.(2x six volt lead acids)

Your acoms receiver is probably a 20 year old one drawing 110mA ,add the rudder servo and those relays that give the clicking noise and you have in excess of 500mA. That 500mA comes from a 13 volt battery…..OK so far?

That 500mA causes the 5 volt supply component to draw 6.5 watts,supply 2.5 watts and burn off 4 watts.

    That’s why the piece of aluminium is scalding hot and needs ventilation.

   1. Supply that five volts from a receiver battery and disable the battery elimination circuit (bec) and you can then use a sealed box. OR
   2. Reduce b.e.c. heat loss by cutting your drive battery so it is nearer to 5 volts 

That 4 watts is what sent your drive transistor over its temperature limit to destruction because it needs a heatsink for large motor currents too,not a 4 watt heat source bolted to it.

What knowledge does yor repair guy have? Did he see any sign of a thermistor to prevent that happening? – probably not.

What you have is a piece of equipment that is poorly equipped for the folk who use it. I note from this both you and Penny Lee have witnessed the unfortunate "malfunction" behaviour of these units that  auto store there setting and loose it when there is a power supply disturbance.

Who else has noticed this?

Tom

After typing that I have no enthusiasm to for the long version on your battery charger Lee wants in that link.

[Paul TParticipant @pault84577]

Cranks ????

Tom 

You can’t mean us….and everybody speaks so highly of you…..

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