Model Boat Mayhem - Forum

Technical, Techniques, Hints, and Tips => The "Black Arts!" ( Electrics & Electronics ) => Topic started by: NobbySideways on June 22, 2015, 03:17:42 PM

Title: Powering Water pump via BEC
Post by: NobbySideways on June 22, 2015, 03:17:42 PM
So I have a rather beefy setup going into my Huntsman, including a couple of 4S Lipos feeding a 160A Water cooled ESC. Because of the complex route the cooling water needs to take plus the heavy demands placed upon it I decided to run a small water pump from 6V to allow me to prevent overheating at low speeds when just a scoop wouldn't be so efficient.


I had planned to run the water pump from a small battery pack but it seems daft when I have the best part of 8000mAh sat in my hull, the current drawn by the pump wouldn't make a dent on my runtime. As I want to run 6v to keep the pumping speed sensible I wondered about using one of the spare channels on my receiver purely to supply the pump with operating voltage.


Would this work? I believe the current should be within that delivered by the BEC, but I don't really want to drag huge amounts of current through the servo connectors. That said, many big servos draw serious current so surely that would be the same?


To clarify I'm not looking to use the receiver to control the motor, just utilise the positive/negative rails to supply power to the water pump.


Thanks for your replies in advance.


EDIT: Just realised, would a UBEC be the future here?
Title: Re: Powering Water pump via BEC
Post by: Tugtower on June 22, 2015, 03:33:50 PM
a water pump will just drain your batterys even more and I've never setup one to run through the BEC of the receiver.


you will be surprised how efficient a water scoop and a motor coil can be, if your worried about over heating,take a look at the zhenoah engines running and they have a water cooled cylinder head and it works just fine, and they get hotter then your electric motor ever will.


you just need to position the scoop behind the prop blade and run it to a cooling coil over the motor and esc (ESC first) motors are designed to run 'warm'.


As for your complex insides well it wont matter water will be thrown up that pipe in moments regardless of the route to take.
(its also less complex then trying an electrical water pump that might fail at any moment)

Title: Re: Powering Water pump via BEC
Post by: NobbySideways on June 22, 2015, 03:37:22 PM
The cooling system at the moment is going scoop, pump, one side of the esc, motor, other side of the esc, outlet. I've already installed most parts so I'm reluctant to move away from this course of action at the moment. Thanks for taking the time to reply.
Title: Re: Powering Water pump via BEC
Post by: Calimero on June 22, 2015, 03:40:54 PM
So I have a rather beefy setup going into my Huntsman, including a couple of 4S Lipos feeding a 160A Water cooled ESC. Because of the complex route the cooling water needs to take plus the heavy demands placed upon it I decided to run a small water pump from 6V to allow me to prevent overheating at low speeds when just a scoop wouldn't be so efficient.


There won't be any overheating at low speed. And scoops get water moving even at low speeds.


Unless it is designed for continuous operation, the only thing you're going to do is break your water pump.


Stick to water scoops if you really want water cooling (decently sized car ESC would probably do the job without water cooling).


What are you temperature readings on the ESC and motor with water scoops/no pump after  5 minutes of hard racing ?
Title: Re: Powering Water pump via BEC
Post by: NobbySideways on June 22, 2015, 03:45:19 PM
My pump is a unit designed for continuous operation. At the moment the system hasn't been run, I'm just over-engineering as usual.


I think I've answered my own question with the external BEC idea. Sorting out an efficient and technically interesting cooling system was a large chunk of the fun part for me, so although I will bear your advice in mind (and quite possibly utilise it if my technique turns out to be unsatisfactory) I'll persevere with the pump for now.


Thanks all
Title: Re: Powering Water pump via BEC
Post by: Tugtower on June 22, 2015, 03:46:54 PM
No worries but i think its a waste of time going the pump route.

I used to run fast electics using 4050KV motors on 220 amp esc's (old school burshless systems before they became more efficient ) and just cool the lot with a water scoop and they were bone cold after 10mins of caning it around the lake.

water pumps tend to not like long run times, unless they are designed to run for long periods of time,(and those ones are rather large)  most of the ones the size to fit in your boat only like up to about 60 seconds of run time before they start to over heat then fail.

well what ever you pick no worries, just remember 'K.I.S.S'
Title: Re: Powering Water pump via BEC
Post by: NobbySideways on June 22, 2015, 03:48:19 PM
No worries but i think its a waste of time going the pump route.


I used to run fast electics using 4050KV motors on 220 amp esc's (old school burshless systems before they became more efficient ) and just cool the lot with a water scoop and they were bone cold after 10mins of caning it around the lake.


water pumps tend to not like long run times, unless they are designed to run for long periods of time,(and those ones are rather large)  most of the ones the size to fit in your boat only like up to about 60 seconds of run time before they start to over heat then fail.


well what ever you pick no worries, just remember 'K.I.S.S'


Thank you, I may end up going back to something simpler yet.
Title: Re: Powering Water pump via BEC
Post by: Stavros on June 22, 2015, 03:56:42 PM
Y lead to your esc use another esc to your water pump and power it from the 6v batt then the faster you go the quicker it will pump used this set up on a Sea Queen I had
 
 
Dave
Title: Re: Powering Water pump via BEC
Post by: NobbySideways on June 22, 2015, 04:00:41 PM

Now thats lateral thinking!
Title: Re: Powering Water pump via BEC
Post by: TugCowboy on June 22, 2015, 04:01:48 PM
Nobby,

I too have been looking to over-engineer a large tug which I'm currently in the process of making and have run into the same thing.
Many replies of "It's been tried and a scoop pickup is the best way" over all the forums I could find on the internet (perhaps should be a hint there we're barking up the wrong tree!)

Anyway I have recently sourced a small diaphragm water pump designed for an aquarium.
Supposedly designed for continuous running. I got a couple of spares in case but  it seems like it should work ok:
http://www.aliexpress.com/store/product/New-Aquarium-12V-R385-Laptop-DC-diaphragm-pump-pumps-water-fish-tank-small-micropump-1-5/914980_1342784358.html (http://www.aliexpress.com/store/product/New-Aquarium-12V-R385-Laptop-DC-diaphragm-pump-pumps-water-fish-tank-small-micropump-1-5/914980_1342784358.html)

At low speeds it will certainly give less flow than a scoop but it will be continuous and predictable so I'm looking forward to giving it a try.

Alex
Title: Re: Powering Water pump via BEC
Post by: NobbySideways on June 22, 2015, 04:05:33 PM
Certainly. I'm keen to stress I'm not knocking any of the replies I've received, I'm grateful to anyone who takes the time to do so, it just wasn't the question I had asked. The most sensible route is not always the most interesting technically..... As for keeping it simple my '72 GT6 is way more simple than my '08 Toyota but the Toyota has a better track record on getting me home...  {-)
Title: Re: Powering Water pump via BEC
Post by: Martin [Admin] on June 22, 2015, 04:14:48 PM
 
Also, remember you won't need much cooling at low speed... because you're running at low power too!
Title: Re: Powering Water pump via BEC
Post by: inertia on June 22, 2015, 04:17:07 PM
Nobby
You have a model there which is the size of a baby's bathtub. You could lose a 6v battery pack inside it - even a big one. The smallest pump will take maybe 2-3A from the batteries which is enough to compromise your run time quite significantly whereas a 5-cell 3300maH NiMH pack will cost a few quid and leave your beefy motor setup untouched. Stavros' idea has merit in that event.
That said, I heartily agree with everything that's been said about the efficiency of scoops, not running pumps all the time etc etc. If you insist on using a pump then first measure its current draw on load and make sure that the UBEC you buy (for it will need to be such a device) can handle that current continuously.
Then there's the pragmatic approach; compare the price of a pump and battery pack (or UBEC) with that of a scoop - you will, of course, need the water outlet and plastic tube either way.

Wanna bet? I know where my money's placed!  8)
DM
Title: Re: Powering Water pump via BEC
Post by: Martin [Admin] on June 22, 2015, 05:30:56 PM
 
WHATS a UBEC  and Who Needs Them ?
 http://www.wattflyer.com/forums/showthread.php?t=39138
Title: Re: Powering Water pump via BEC
Post by: NobbySideways on June 22, 2015, 06:10:07 PM
I'll go measure the current draw on the pump loaded. You say the model is huge, I've no idea how you guys cram so much in these things; mine is looking pretty stuffed. I'll see if there is somewhere for a motor battery.


One thing to consider about the current draw; although I'll be drawing (maybe) 2A loaded, thats at 6V using a DC to DC converter, so its actually taking in the 14.7V at closer to 1A. I would still like to maximise run time, so I'll investigate a small battery pack to use.
Title: Re: Powering Water pump via BEC
Post by: NobbySideways on June 22, 2015, 06:17:44 PM
Just another little thing to think over, what about profiling a spare channel to mix in the motor to run at lower (main) motor speeds? So when the boat is running slowly the pump runs, at higher speeds it would switch off to conserve battery and rely on high speed water flowing into the scoop? Would conserve the battery.
Title: Re: Powering Water pump via BEC
Post by: inertia on June 22, 2015, 07:23:01 PM
Yes - all very clever (and complicated) m'duck but, as someone pointed out earlier, you don't need any cooling when the motors are running slowly. If you regard the scoop and prop respectively as the intake and the impeller of a pumped system then you already have the solution to the cooling problem. Why make things more complicated?
Please yourself.
DM
Title: Re: Powering Water pump via BEC
Post by: NobbySideways on June 22, 2015, 07:37:39 PM
Yes - all very clever (and complicated) m'duck but, as someone pointed out earlier, you don't need any cooling when the motors are running slowly. If you regard the scoop and prop respectively as the intake and the impeller of a pumped system then you already have the solution to the cooling problem. Why make things more complicated?
Please yourself.
DM


Please don't take my questioning the basics as being disrespectful of those kind enough to show their past experiences, that certainly isn't the case. I'm reading this forum like a sponge and sucking up information all over the shop; I'm learning things that are incredibly interesting to me. Everything said here makes sense to me so far, however designing the cooling system was one of the fun bits and I'd like to see it in action. I forgot to add that the system is already switched on a spare channel from the receiver so it doesn't have to run all the time; a bathtub trial I've just done seems to suggest that the pump acts as a good booster but, as mentioned, the prop efflux creates good flow too.


I'm interested in all aspects of this; and whilst many (myself included) agree that I'm overcomplicating this, that is part of the interest for me. So far my model has been a combination of using the vast experience of members of this forum, and throwing in a bit of personal innovation that will either sink it or prove an interesting talking point. I'm having a lot of fun in the process, and I thank those contributing for their input into my enjoyment.
Title: Re: Powering Water pump via BEC
Post by: NobbySideways on June 22, 2015, 07:47:17 PM
I forgot to say, the motor was drawing 800ma at 6v.
Title: Re: Powering Water pump via BEC
Post by: Tugtower on June 22, 2015, 08:15:45 PM
There's no harm in playing around and experimenting with ideas, however over engineering something to give you the same result as something that's a Proven method just seams pointless and rather complex to problem solve when it goes wrong.

I'ld rather you enjoy the model then come back in a few weeks asking for help when it starts to go wrong

There is no set ' right answer here' a lot or Real life boats use water pumps to cool them, others use prop driven water flows, but were talking on a model where truth be told simple tends to be better, think long term, maintenance, repairs etc etc, the more complex a boat becomes the more time, and money end up being spent to keep that one boat running.

When you have a fleet of 40+ reaching past 50 like I do. that's a lot of boats to keep repaired if i innovated on all or even half of them i'ld never be able to afford or have the time to keep them all running,
Simple works and simple means easier to repair/ fix, problem solve and overall cheaper, as well as not spending days or weeks fixing something when you could be onto something else.
 
I've done that when i was a Lot younger and spent a year fixing 1 boat over something as simple as changing a prop shaft which i stubbornly refused to do ( ball raced shaft seized up and i swore blind it was the motor and the shafts were just' stiff') until my old man basically told me dead i was wrong and to listen to his experience, something I've never forgotten since. Fyi he was right, changed the shaft boat ran fine a week later.

You may not always like the answers to questions dosnt mean they are wrong.

just my 2 cents here, sounds a bit Bla now i read it back..  {:-{  i really really really just don't wanna say ''i told you so''
Title: Re: Powering Water pump via BEC
Post by: NobbySideways on June 22, 2015, 08:31:11 PM
just my 2 cents here, sounds a bit Bla now i read it back..  {:-{  i really really really just don't wanna say ''i told you so''


I'm not going to be upset by an I told you so answer. My original question was lost in the maelstrom of other responses....


The way I've designed it I can bypass the pump and remove it in about 5 minutes. It's not going to break my heart, just wanted to try it.
Title: Re: Powering Water pump via BEC
Post by: malcolmfrary on June 22, 2015, 09:17:01 PM
Quote
As I want to run 6v to keep the pumping speed sensible I wondered about using one of the spare channels on my receiver purely to supply the pump with operating voltage.




Would this work? I believe the current should be within that delivered by the BEC, but I don't really want to drag huge amounts of current through the servo connectors. That said, many big servos draw serious current so surely that would be the same?
It would work for a time.  The continuous use of heavy (in RX terms) current could cook the tracks in the RX.  Heavy servos are usually only active in short bursts, and, if powered via the RX, need really good wiring throughout the system.  It might also run very close to, or exceed, the limitations of an ESCs built in BEC, so an external UBEC or separate battery would be needed.  Or a scoop.
Title: Re: Powering Water pump via BEC
Post by: NobbySideways on June 22, 2015, 11:03:46 PM
...Or a scoop.
{-)


Thanks Malcolm, I did suspect the internals wouldn't be that beefy, just a light PCB.


I'll trial it with and without the pump running, we've got some pretty good temperature data loggers at work that I will assess things with.
Title: Re: Powering Water pump via BEC
Post by: Calimero on June 22, 2015, 11:08:01 PM
Now that it is clear that this is just "building stuff for the sake of it "(which is perfectly legitimate), one more question: when unpowered does the water pump let water go through ?


It would be quite unfortunate to have  your little experiment actually turn harmful because you end up forgetting flicking the switch to get the pump running and end up with no water flow whatsoever. And water cooled ESC will require water cooling if you hit them hard (unlike car ESCs which come with large heatsinks and fans).
Title: Re: Powering Water pump via BEC
Post by: derekwarner on June 22, 2015, 11:16:05 PM
Well Nobby.......there is always another one & today it is me  %)

Guilty of over designing componentry :embarrassed:.....but then I think

1. what happens if you pick weed or contaminate in a water scoop?........20 foot from shore you can't  see the water cooling discharge = a fried ESC?
2. what quality of water do you intend to run on?
3. being a diaphragm pump, the only intentional limitation is number of pulses & they suggest up to 1200 hours life
4. even on a pump failure with such a design will still maintains water tight integrity
5. you could always install a large suction chamber with a course mesh element to keep the house bricks out.......the size of the suction chamber surface area could be x4 times the ID of the pump suction hose

Keep us posted on your chosen path....... Derek
Title: Re: Powering Water pump via BEC
Post by: NobbySideways on June 22, 2015, 11:33:12 PM
Now that it is clear that this is just "building stuff for the sake of it "(which is perfectly legitimate), one more question: when unpowered does the water pump let water go through ?



I believe so, when I pushed water through with my mouth (nice image for you all) it didn't seem difficult to overcome the pump; Its centrifugal rather than positive displacement.


Derek, I like the way you think. :)
Title: Re: Powering Water pump via BEC
Post by: derekwarner on June 22, 2015, 11:35:01 PM
Nobby....Camilero raises a good question here  :-))..surface cooling just like cars but in a marinised version!.......real ships used below hull surface water cooling tubes....for cooling of hydraulic systems O0

You could build a small closed loop fresh water heat exchanger with a matrix of underwater radiator tubes and powered by your diaphragm pump, this way no need for flushing the cooling water circuit after each days outing to cleanse the cooling internals of the ESC...

One must consider the thermal gradient of the exposed total external surface area of the tube matrix and the velocity or speed of the volume of sea water passing over the tubes as compared to the single slug of cooling water which is represented by the net column length of the ID of the tube from suction to discharge point

To take it to then next step in thermal efficiency you could also consider using ethelyene glycol as the cooling fluid......

For that matter you could also install a second diaphragm pump as an auxiliary O0.......

My only concern here is you may need to install a heater in the cooling circuit to ensure hell does not freeze over ........

It's all good fun Nobby ....solving these complex challenges.......remember if there is a simple answer.......with a little thought a technically superior solution exists.....but only waiting for our minds to stumble and be enlightened......Derek {-)
Title: Re: Powering Water pump via BEC
Post by: NobbySideways on June 22, 2015, 11:46:06 PM
It's hard to know if you are serious...  {-)


I notice the huntsman upper structure has cooling vents which Inertia designed to actually operate to aspirate the forward cabin...  :}
Title: Re: Powering Water pump via BEC
Post by: davidm1945 on June 22, 2015, 11:50:54 PM


 

For that matter you could also install a second diaphragm pump as an auxiliary O0 .......



Of course, powered by a wind turbine mounted on the cabin roof!

This is getting silly, ennit.....
Title: Re: Powering Water pump via BEC
Post by: NobbySideways on June 22, 2015, 11:53:38 PM
Some of the best ideas start off with the craziest statements...  :}
Title: Re: Powering Water pump via BEC
Post by: derekwarner on June 23, 2015, 12:09:15 AM
Sorry David.......& despite my OZ slant on things :o ....thinking backwards ....the ethelyene glycol closed loop external heat exchanger has real technical advantages  O0 and would not be difficult to manufacture & install

In my steam build and installing a 6mm diameter x 5 mm stroke boiler make up water feed pump at first seemed OK, but was going to be limited by the low paddle shaft speed of ~~ 150 RPM.....

So to overcome this shortfall have installed an identical 6mm diameter x 5 mm stroke pump as an auxiliary drive by a 12V dc motor....which is not all that different to the original question posed by Nobby ......

Most early Australian paddle wheeler engines were non condensing, although a few engines were in fact under hull surfacing condensing.....so essentially no different to what I have suggested here  O0

Below are the images of both the axel driven pump & the 12 Vdc auxiliary....... Derek
Title: Re: Powering Water pump via BEC
Post by: derekwarner on June 23, 2015, 12:33:50 AM
Nobby....here is an example of a ships below hull surface water cooling tubes  :-)) ..... Derek

Title: Re: Powering Water pump via BEC
Post by: inertia on June 23, 2015, 08:45:33 AM
I notice the huntsman upper structure has cooling vents which Inertia designed to actually operate to aspirate the forward cabin...  :}
That was actually more to supply air for the carby (i/c engine, you see). The actual cooling was by.........................scoop and loop! In the end we punched out the front window glazing - far more effective.
DM
Title: Re: Powering Water pump via BEC
Post by: NobbySideways on June 23, 2015, 08:59:26 AM
Whether or not most of this is directly applicable to my application or not doesn't matter any more, I'm finding this all thoroughly interesting, thank you all.
Title: Re: Powering Water pump via BEC
Post by: Martin [Admin] on June 23, 2015, 09:17:01 AM
 
Me too!    O0
Title: Re: Powering Water pump via BEC
Post by: sparkey on June 23, 2015, 09:34:57 AM
 :-)) I say go for it Nobby and don't be put off,you never know you might find a new way of cooling motor and Esc's,the Wright brothers were told flight was impossible but they kept trying and the result is we are now all flying,anyway trail and error can be a lot of fun and you can learn a lot from it,I am always trying new things sometimes I get it right and sometimes I don't but always learn from it,if you have got the pump try it out and if does not work you can go back to just using the scoop,Ray. :-))     
Title: Re: Powering Water pump via BEC
Post by: Martin [Admin] on June 23, 2015, 09:56:29 AM
 
 I can't quite remember the configuration of the boat but once I did find that the water pumped itself due to the 'glow' engine heating (and expanding) the the water and the outlet tubing being bigger than the inlet tubing.... or something!
Title: Re: Powering Water pump via BEC
Post by: malcolmfrary on June 23, 2015, 03:43:35 PM
Looking at Derek's keel coolers picture, I feel that the most effective is the external pipe one, but that this would introduce unwanted extra drag on a fast boat.  Maybe solder copper pipes to a copper or brass plate and have the plate flush to the outside of the hull bottom.
Back in the elder days, I recall a magazine article about someone water cooling a 2N3055 power transistor by mounting it through his hull.  This was before PWM was the norm, so it would be effectively a linear regulator, and need a lot of heatsinking.  Direct contact with moving water is probably as infinite a heatsink as you can get.
Title: Re: Powering Water pump via BEC
Post by: Terry on June 23, 2015, 05:34:41 PM
I built a Sea Commodore a couple of years ago and wanted a pumped cooling system. Not to over engineer it, but to provide a scale like appearance to the water outlet, even working when the boat was not moving. I stripped out one of those oral hygiene gadgets that pumps water to the toothbrush and found a reciprocating piston pump perfect for the job. It runs quite happily off the 7.2v main drive battery and has lasted a couple of summers so far.
Cheers, Terry.
Title: Re: Powering Water pump via BEC
Post by: Netleyned on June 23, 2015, 05:47:41 PM
Seen one or two at the lake .
As Terry says it looks right when
pumped.
When a big tug was done the same way
and a pipe came adrift a tug became a
submarine :embarrassed: :embarrassed:

Ned
Title: Re: Powering Water pump via BEC
Post by: derekwarner on June 23, 2015, 10:44:30 PM
Malcolm.....the images shown are in fact five different examples...your thought couples both, the 'skin over the grid' arrangement.....

One point here, when I mentioned ethelyene glycol...that was simply to draw attention as in real practical terms this fluid whilst having a higher boiling point will not adsorb a significantly greater amount of heat than plain distilled water [@ a nominal 20 degrees C]

However it does have the advantage of chemical stabilizer inhibiters used universally in motor engine cooling systems with aluminium blocks of pump components ...so any commercial radiator fluid with antifreeze would suffice

In a perfect scale model application, a small fluid header tank [open to atmosphere] would also be advantageous O0.....as would small lengths of semi translucent synthetic tubing fastened securely with tubing barbs....to act as a sight glass and resilient elements between the hull and pump assembly...... Derek