Model Boat Mayhem

Please login or register.

Login with username, password and session length.
Pages: [1]   Go Down

Author Topic: which prop and how to cool the motor  (Read 3211 times)

wild1

  • Shipmate
  • *
  • Offline Offline
  • Posts: 15
  • Model Boat Mayhem is Great!
  • Location: Malaysia
which prop and how to cool the motor
« on: July 17, 2017, 12:01:24 pm »

Hi and Good Evening,


I am guessing this topic has been knocked around before and I am no genius so please bear with me.
I recently have gotten really interested in model boats and more so because my 11 your old son has developed an interest in speed boats. Many years ago I bought for him a hydroplane boat but it got spoiled meaning the motor and esc got fried, so it got put on the shelf and forgotten.
Today whilst raking in my workshop I came across a Turnigy Aerodrive B650 -2300 motor in a box brand new. I also found a hobby wing 60 amp esc. I did a search and found these were bought for a RC motor bike we used to have years ago but now no more, I also read it was suitable for car and boat. So I wired it all up and put it into the boat, we are running this on a Gensace 4000mah 3s lipo.
The boat ran like a jet it was so so fast. I was excellent however after about 5 mins of running the boat stopped dead. I got it back into shore and opened it up to find the motor so hot it could easily burn your hand.


So here goes, the question is, Why is this?


I have no idea what prop is on this thing so If it is a prop issue what prop would suit this combo?
Can I put cooling around the motor will this do what I need?
Is there something I am missing?
I am complete novice here so I appologise for the stupidity of my questions.


After about 15 mins the motor had cooled again and the motor ran perfectly so luckily not spoiled.


Stephen
Logged

grasshopper

  • Full Mayhemer
  • *****
  • Offline Offline
  • Posts: 773
  • Location: Lincolnshire!
    • A1 Hobbies Ltd.
Re: which prop and how to cool the motor
« Reply #1 on: July 17, 2017, 12:30:26 pm »

Selamat paggi!
Could well be over-propped causing the ESC to heat up and shut down, it may have a built in thermal protector.


Try sourcing a smaller propellor or one of less pitch. Water cooling the ESC an motor could be beneficial,but to suggest anything would need photo's.
Logged

wild1

  • Shipmate
  • *
  • Offline Offline
  • Posts: 15
  • Model Boat Mayhem is Great!
  • Location: Malaysia
Re: which prop and how to cool the motor
« Reply #2 on: July 17, 2017, 01:16:31 pm »

Hi and thanks for the reply,


I dont know what prop is on and I got the motor wrong, It is the Turnigy Aerodrive B3850 2300 kv
I will send some pics tomorrow.
If someone could suggest what prop would suit this It would be a great help.
Would it be the esc that shut down or the motor itself?
Now is ok again but I wont run it until I sort out what I should do with it.


Stephen
Logged

Tug Fanatic

  • Full Mayhemer
  • *****
  • Offline Offline
  • Posts: 2,480
  • Location: England
Re: which prop and how to cool the motor
« Reply #3 on: July 17, 2017, 01:34:27 pm »


Lack of information is a problem here.


I cannot find any reference to a Turnigy B3850 & you have not told us much about the prop that is connected to it.


It sounds very over propped but it just might be that the Lipo reached its cut out voltage rather than that the ESC had an overheating cut out.



Logged

wild1

  • Shipmate
  • *
  • Offline Offline
  • Posts: 15
  • Model Boat Mayhem is Great!
  • Location: Malaysia
Re: which prop and how to cool the motor
« Reply #4 on: July 17, 2017, 11:22:06 pm »




Thank you for the replies,


Please advise me what information do you need?


I do not know what prop is on it, it came with the boat. All I know is that it is plastic, 2 blades, and 40mm dia.


The boat is a hydroplane design about 2 feet in length, I have no idea the brand or model?


I used to be into RC helicopters many years ago and have still a lot of stuff lying around in my workshop. The boat has sat on the shelf for about 5 years with a busted ESC and Motor.


We also used to have a Quanum 400 RC motor bike at that time too, This has long gone but the motor and ESC I have put in this boat were bought for that. After some searching I found that this motor is supposedly ok for boat or car.


The motor box states Turnigy B 3850 - 2300 which is what i typed earlier however this morning when I loosened it and took a closer look It has actually Turnigy Aerodrive B3650 - 2300 on it. The esc is a fan cooled Hobbywing 60amp.


I am completely new to boats and have no idea what else you need.


The battery is a 3s Lipo gens ace 4000mah.


When we run it the motor gets super hot and I mean burning hot. this morning I ran it on the kitchen table at half throttle and within 3 ,ins it was already too hot to touch. Does this mean it is not the prop because I am guessing there is no load on it running it dry?


Any suggestions of what prop to start with or should I up the ESC to 120 amp? will be appreciated or even some info as to why the motor is getting so hot.


Again if there is anything else needed please let me know I would like to get this going again so all advice is valuable to me.


I have tried to attach some pictures but not sure how to do this either sorry if they don't come through.



Logged

rnli12

  • Full Mayhemer
  • *****
  • Offline Offline
  • Posts: 715
  • Location: Cornwall
Re: which prop and how to cool the motor
« Reply #5 on: July 18, 2017, 07:16:19 am »

Hi,

If this is a hydroplane then I am thinking a 2 bladed surface drive propellor around 40mm but will need a picture of the boat as it depends on size, weight, voltage etc.

Rich
Logged
Regards,

Rich

wild1

  • Shipmate
  • *
  • Offline Offline
  • Posts: 15
  • Model Boat Mayhem is Great!
  • Location: Malaysia
Re: which prop and how to cool the motor
« Reply #6 on: July 18, 2017, 07:29:26 am »

Hi Rich,


I tried to post pics but cannot seem to get them uploaded so not sure yet how to do this.
yes is a hydroplane and it already has a 40mm propellor.


I am now wondering if it is the prop, because today I removed the motor from the boat and the flexi drive so purely just the motor nothing attached and then ran it in my hand. Within 1.5 minutes I could no longer hold it. So there is something else causing the overheating.


I am quite stuck.


Stephen
Logged

rnli12

  • Full Mayhemer
  • *****
  • Offline Offline
  • Posts: 715
  • Location: Cornwall
Re: which prop and how to cool the motor
« Reply #7 on: July 18, 2017, 07:34:52 am »

Hi Stephen,

I have a feeling the LiPo combination maybe too much for the motor, the free spin is over 20,000 revs I think at 11.1 v

Regards,

Rich
Logged
Regards,

Rich

wild1

  • Shipmate
  • *
  • Offline Offline
  • Posts: 15
  • Model Boat Mayhem is Great!
  • Location: Malaysia
Re: which prop and how to cool the motor
« Reply #8 on: July 18, 2017, 08:04:29 am »

Hi Rich,


Then what should I do?


Change ESC?
Go to a 4 or 5s battery?
Or dump it and start again?
Put a bigger prop?


If it is dump it then what motor ESC combination would be fast for this?


please be patient with my questions I am quite ignorant with regards to this.


Stephen
Logged

wild1

  • Shipmate
  • *
  • Offline Offline
  • Posts: 15
  • Model Boat Mayhem is Great!
  • Location: Malaysia
Re: which prop and how to cool the motor
« Reply #9 on: July 18, 2017, 12:11:57 pm »

To add to this thread today I took out the Turnigy motor and replaced it for a test with the T Motor 780kv mulitrotor motor.
I knew it would not be like the turnigy as far as speed went but it did run but not so fast. it ran quite long and no over heating.


So 3 s Lipo 4000mah battery,


Turnigy B3850 2300 KV gets super hot very fast,


The T motor Mulitrotor motor 780kv runs long time and barely gets warm.


What is needed to get the Turnigy motor to run in this boat?


Hope you all can help me with this.


I still have not been able to upload my pics yet.


Stephen
Logged

Tug Fanatic

  • Full Mayhemer
  • *****
  • Offline Offline
  • Posts: 2,480
  • Location: England
Re: which prop and how to cool the motor
« Reply #10 on: July 18, 2017, 12:49:54 pm »


You have largely answered your own question.


A  lower kv motor turns the prop slower making the boat less fast and using less amps.


Is the 780kv motor too slow for you?


To reduce the load on your 2300kv motor you have a number of choices. First reduce the voltage of your power pack - try a 2 cell pack and/or reduce the diameter/number of blades/pitch of your prop.  You could also try water cooled mounts to dissipate the heat better.


If you have access to a 2 cell pack which would probably only reduce the revs by around a quarter as you are currently overloading the motor but might well halve+ the heat that your motor is trying to dissipate.  I would try that first (no cost option) & see where it gets you.


You really need to be able to measure how many amps your motor is using and what ampage the motor is rated for on 3S?


 
Logged

wild1

  • Shipmate
  • *
  • Offline Offline
  • Posts: 15
  • Model Boat Mayhem is Great!
  • Location: Malaysia
Re: which prop and how to cool the motor
« Reply #11 on: July 19, 2017, 04:23:14 am »

Hi and Good morning,


Finally I am beginning to understand, I thank you for your patience and advice.


However this leaves me with a dilemma, please correct me if I am wrong.


Reducing the prop size reduces the load with in turn increases speed, but also reduces the amps am I correct?


Increasing the prop size then increases the load and in turn reduces the speed, but increase the amps am I correct?


What if the motor is getting super hot because it is running too fast?
So is there a risk of, by reducing the prop size of over speeding the motor and still getting super hot?
Or by increasing the prop size reducing speed but adding extra amps and also getting hot?


For an old guy like me it makes my head spin hahaha.


So taking your advice, today I have ordered 2 x 2200mah 2s 30-60c lipo packs. Reducing the voltage of course makes great sense.


My current prop is 40mm so I have also ordered 2 new props but no great difference one is 35mm and one is 47mm dia respectively. The reason is simply to do the testing to see which one is better and give some indication which direction to go. I also will have to make a cooling jacket if I can because if I measure correctly the motor is 35mm dia and I don't see a jacket for that size motor anywhere. However some say that this motor is 36mm and 540 size (not sure what this means) but I haven't got vernier to check. Also the motor although is a new one is no longer produced and out of stock so cannot find the motor specs anywhere.


With your advice and the new parts coming I hope to see some difference on the next run.


Thanks again.
Logged

Tug Fanatic

  • Full Mayhemer
  • *****
  • Offline Offline
  • Posts: 2,480
  • Location: England
Re: which prop and how to cool the motor
« Reply #12 on: July 19, 2017, 09:39:51 am »

OK. What I am saying is general. I do not know your motor, your boat nor your prop.

The prop puts a load on the motor which runs slower because of the load. The more the load the slower the motor turns and at the same time the more amps the motor uses. As you say reducing the load allows the motor to run faster and at the same time uses less amps. Reducing the prop size will reduce the load if the props are otherwise identical. If they are not identical then the number of blades, the propeller pitch and the actual design of the blades can all alter the load. Generally a smaller prop = a smaller load & less amps. At the apparently excessive load you are apparently putting on your motor you might well actually go quicker with a prop that puts less load on the motor. The exact best prop is found by black magic or having a number of props to try or perhaps one of the hydroplane guys here making a suggestion.

Increasing the prop size increases the load. Whether it reduces the speed depends on the motor. If the motor is powerful enough a bigger prop will go faster because the motor can cope with the prop. If the motor is not powerful enough the boat will go slower & the motor will overheat. Think of it like your car. If your family gear were geared to do 200mph (a big prop) it would not go any faster than how it is geared now to do say 120mph (a small prop). If you put a Ferrari engine in the car the 200mph gearing would work rather better.

A motor wants to run at a set rpm. In your case you have a 2300kv motor. 2300 is how many revs the motor wants to do with each volt it receives. In your case 2300 x 11.1v (a 3cell LiPo) = 25530rpm. As you put load onto the motor the amps the motor use goes up and the revs the motor achieves goes down. Brushless motors try very hard to keep most of those 25530 rpm and just keep using more amps trying to achieve it. In model aircraft we generally reckon that 80% of 25530 is about as low as we would want to load the motor but that is with a big fan out front keeping the motor cool. In a boat you would want to keep the load down & keep the rpm higher or go for water cooling. The motor will not do more than the 25530rpm with your 3S battery even if it does not have a prop at all. It would run pleasantly cool like that and use very few amps with what is effectively the smallest propeller that you can imagine (none).

If you look at the chart that I have linked below you can see the effect of load on the motor. It is not you motor & it is talking aero props but you can see all of what I have said if you study the 2S & 3S tables.
https://www.rcgroups.com/forums/showthread.php?2112708-Sunnysky-X2204-2300KV-Thrust-Test-2S-3S

When I suggested trying a 2S I suggested it as trying one at no cost (borrowing or if you already had one). Buying 2 is not the no cost option that I had in mind nor suggested. Fingers crossed it works well.




Logged

Ron Rees

  • Full Mayhemer
  • *****
  • Offline Offline
  • Posts: 152
  • Model Boat Mayhem is Great!
  • Location: Romford essex
Re: which prop and how to cool the motor
« Reply #13 on: July 19, 2017, 10:11:54 am »

Morning all


You are caught between the' devil and the deep blue sea ' with this one. The Turnigy motor you are using is designed for an aircraft. Hence the name Aerodrive and a Kv rating of 2300 is fairly common but it would be open to forced air coming from the propellor in a plane which cools it down...a lot.


An 11.1v Lipo times 2300 means a rotational speed of about 27,600 rpm if the battery is fully charged (12v. plus) which is the same speed as a high speed woodworkers router. It is probably pushing out at about 1/2 a horsepower as well!!!! Of course it is going to get very, very hot in a boat.


At the same time you want a racing hydroplane to go really fast so to do this people put bigger and bigger propellors on Like the 40mm you have, which makes it get even hotter still. That is until it blows up.


The motor is designed to run at that speed believe it or not but it needs to be cooled, a powerful fan will help but its not enough. You could change the mounting to a water-cooled one as well, there are several out there for a 35mm diameter motor, it does not have to be a matched turnigy one.
I would suggest a two bladed Hydro prop of about 35mm diameter, which that motor can drive at 26000 rpm . K-series Graupner props are good if you can find them where you live. Or look for an aluminium one of the same diameter, they are quite curved and are very efficient at high speeds. You may find that sizes even smaller work better in fact, like 30mm or 32mm.


Putting a 750 kv motor in will solve the heat problem a bit, but it will not go like a hydroplane.


I'm afraid the best other option would be a 50mm diameter by 70 long 2000 plus KV. inrunner with a watercooled jacket, a 120 amp ESC as minimum, and even then it will run a 35 K racing or Hydro prop. But it is designed for a boat and will do what you want....a lot of money though.


My thoughts only (Based on past experience).......have fun.


Ron.
Logged

wild1

  • Shipmate
  • *
  • Offline Offline
  • Posts: 15
  • Model Boat Mayhem is Great!
  • Location: Malaysia
Re: which prop and how to cool the motor
« Reply #14 on: July 25, 2017, 12:28:50 pm »

Hi Guys,

Finally did the test on the aero drive 2300 kv motor following your instructions,


First up was the 35mm prop 2s lipo and ran for 2 mins. 50 % battery showed on the battery checker at the end of the run.
The result was not as fast as we wanted but reasonable. The motor got sort of hot but not roasting hot. I could hold my fingers on it for more than 3 secs.


Second up was the 3s battery with 35mm prop, ran also for 2 mins.
The battery showed only 15 % used I thought surprising.
The motor was hotter and I could only hold my fingers on for 2 secs max, however the speed was not too bad, not record breaking but not so bad for us.

Thirdly was the 2s Battery and the original 40mm Prop speed was ok but the heat was quite hot being only able to hold my fingers on for about 2 secs.


Next up was the 2s battery and the 45mm prop, it ran not too bad but we could not check the temp because halfway through the run the propeller came of. I must not have fixed it properly.

The burning question (excuse the pun) is;

How hot is too hot?

My next test is a lower KV motor 1900 Scorpion out of one of my T Rex 500 Helicopters. I figure that this supposed to run at 6s so If I run the thing with 3s the amps should be lower and the temp better.

Thanks again for your input but I am beginning to think I am going to have to invest in a water cooled proper boat motor / ESC combo.

Also the water leaks back up the prop shaft a bit and I cant seem to get the flexi drive out.

Maybe we have to buy a new boat completely.



Logged

spearfish99

  • Full Mayhemer
  • *****
  • Offline Offline
  • Posts: 370
  • Location: Northampton
Re: which prop and how to cool the motor
« Reply #15 on: July 25, 2017, 10:11:00 pm »

 There are ways of cooling the motor, 1) a water jacket around the case of the motor. These can be home made or bought. You can probably get more idea about these from https://www.offshoreelectrics.com/, along with quite a bit of advice.   2) you can use a water cooled motor mount which basically cools one end of the motor but effectively sucks the heat out of the rest. You will see these on the above mentioned web site or they are advertised widely on Ebay. I use them for outrunner motor but they work just as well for inrunner motors such as you have. The photo shows two of them in use in a twin motored hull
Logged

wild1

  • Shipmate
  • *
  • Offline Offline
  • Posts: 15
  • Model Boat Mayhem is Great!
  • Location: Malaysia
Re: which prop and how to cool the motor
« Reply #16 on: July 28, 2017, 02:42:53 am »

To update this post,


I took out the Turnigy Aerodrive 2300kv in runner motor and replaced it with the Scorpion 1900 out runner motor from my Trex500 helicopter together with the Align esc. This was sitting on the shelf in the workshop for so long I thought I would give it a try. I ran it for a test yesterday using the original 40mm prop that came with the boat and 3s 4000mah battery. It ran great fast but not overly fast, but faster than the other motor. the motor was barely warm after 3 mins of running and still had 68% power left in the battery. On my quest to get it where I want it so both my son and I can enjoy it, today I will modify the motor mount so I can fit a 4s 5000mah battery inside.
I will try to post a link to a video clip of the next test.


On another note I now need to try to reduce the water coming the prop shaft, There doesn't seem to be any bushings or bearings in the tube just a flexi drive. Would it be ok to put grease all over the flexi drive? would this reduce the water leakage?


I thank everyone who has helped me with this I feel I have learned such a lot in a short time thanks to this forum. i have been out of RC for many years and never dabbled with boats so you all have been a good help, Thanks.


My target is to build a lifeboat hahaha but I need to learn some more before I get into that.


Stephen
Logged

jarvo

  • Full Mayhemer
  • *****
  • Offline Offline
  • Posts: 662
  • Etherow model boat club
  • Location: Bredbury Stockport Cheshire
Re: which prop and how to cool the motor
« Reply #17 on: July 28, 2017, 09:04:33 am »

Hi Stephen, your last post may give a clue. You said water was coming up the prop shaft, and it is a flexi drive, you have to grease the cable at least every sailing session, it may be the cable is dragging because of no lubrication.  Put a smear of grease along the whole length of the cable. As to losing the prop, try some nailvarnish as a nut lock, (this is removable)


You also mention testing the boat, was this free running? if not it will overheat as the prop is partly stalled in the water, causing extra drag.


Mark
Logged
Tugs are for pulling

wild1

  • Shipmate
  • *
  • Offline Offline
  • Posts: 15
  • Model Boat Mayhem is Great!
  • Location: Malaysia
Re: which prop and how to cool the motor
« Reply #18 on: August 01, 2017, 01:47:09 am »

Just to update my result of the thread.


The scorpion 1900 KV motor and Align ESC, Both are from my T-rex 500 helicopter and are awesome.


I ran the stock 40mm prop,
LIPO 6s 2600mah battery,
Scorpion 1900kv motor,
Align ESC,


The motor runs just warm and the runtime is quite good in excess of 5 mins.


The speed is fast in-fact so fast it is too fast for the small lake we use, so much so that we ran out of water before hitting full throttle.Throttling up has to be gentle as I think it goes so fast it may flip if pushed up hard.


This combination works nicely. the boat planes smooth and above the water.


My only issue now is there is some water getting in from somewhere and I don't know from where. I suspected the prop shaft but I filled that with grease.


I have attached some pics the action shot is a handphone shot so not so good.

Logged
Pages: [1]   Go Up
 

Page created in 0.098 seconds with 21 queries.