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>> Home > Forum > Electrical Related > Motor problem
Motor problem
(868 views)
Author Message
RichardSReade
(Sub-Lieutenant)





Forum Posts: 22
5th Nov 2017 15:32  
>> Permalink
mdlbt.com/35351

Hi All looking for some advice, A bit of background first, in the early sixties my late father and myself started to build a Sea Commander, when Mother and father separated, he took the model with him, it ended up in the loft of his new residence and stayed there untouched until he asked me to take it just before he passed away in 2000, it then sat in my workshop until I decided to finish it in 2015 after a hip operation, the first time I floated it was last weekend at Coate water in Swindon, I then spent a few hours in the bathroom when the wife was out to get it sorted with lead weights and a smaller battery than the big 12 volt alarm battery I had fitted, so with the 7.2 volt battery fitted I went back to Coate water and tried it out, I removed the weight from the stern and swapped the mid and Bow weights around and it sat just right and motored lovely with a nice Bow wave and a hollow wave at the stern with good rudder response. However after about 10 minutes the motor stopped, I still had rudder control and as it happened the boat was aiming for the jetty so had no problem recovering the boat, the motor however was smoking hot and burnt out. what is the best type of motor to use on one of these boats, photos of the boat and motor fitted and a photo of a spare working motor, thanks in advance.
Sorry for writing a book😊


Attached Files - Click To View Large


enjoyment is important.
RichardSReade
(Sub-Lieutenant)





Forum Posts: 22
5th Nov 2017 15:36  
>> Permalink
mdlbt.com/35352

I should have said I spent some time in the bathroom floating the boat in the bath tub when the wife was out to get the trim better.


enjoyment is important.
scout13
(Petty Officer)





Forum Posts: 5
5th Nov 2017 19:47  
>> Permalink
mdlbt.com/35383

how have you got the batteries connected each pack is 7*2v have you wired them so it is putting to much power to the motor
also looks as though you have covered up all the air vents to the motor
also try a fuse in the system it saves blowing up speed controllers hope this helps

Dave M
(Fleet Admiral!)





Forum Posts: 1398
5th Nov 2017 20:27  
>> Permalink
mdlbt.com/35388

Hi Richard
I suspect the prop fitted is too big for the motor. If the pond had lots of weed this will also have placed a heavy load on the motor.
Ideally the prop should be a lesser diameter than the motor and preferably not too coarse a pitch.
A 550 motor that you intend to fit should be fine. Do a quick run round the pond and bring into the bank to check the motor. If you can't touch without going ouch! its overloaded and you need a smaller prop.
Mention has already been made about the batteries. The motor is rated at 7.2 volts so one battery is the correct voltage. If you connect two batteries in series I suspect you will see some more smoke. To help the model to come onto the plane it will help if the bulk of the ballast and weight is towards the rear.
Hope this helps


Live long and prosper

Dave
jarvo
(Fleet Admiral!)





Forum Posts: 466
5th Nov 2017 21:09  
>> Permalink
mdlbt.com/35390

Hi Richard, as an extra to Dave M. the battery packs are different sizes, 5000mah and 3300mah, if both batteries are connected together they will cause problems with power balance, as said the cooling slots are covered. You said the motor was cooking, have you tried it since? maybe it was the ESC that cut out through the overloading with the prop to big. PS what size prop is fitted?
The 540 in the 4th pic may not be big enough, a 600 size or even an 850 would give a lot more torque and probably more speed, you can back off the throttle but a small motor will always struggle, and will probably be run at near full power a lot of the time.
Hope this helps
Mark


Etherow Model Boat Club
RichardSReade
(Sub-Lieutenant)





Forum Posts: 22
5th Nov 2017 21:23  
>> Permalink
mdlbt.com/35391

Scout13 I only have one battery connected at a time, with two batteries in situ I can use the other one when the first one is flagging,to give a longer running time, I could put them in Parallel but prefer to know I have a charged battery to use with an approx running time before it fails altogether. I have made a cover over the shaft coupling to prevent any cables coming into contact with it should they move, there is plenty of air space around this cover as well but the photo does not show it.Dave M the pond is weed free and the prop is the recommended one in the plans for the boat, as far as I am aware it is no larger dia. than the motor, but I will check that.As far as the weights I had to put lead in the front and mid section to get the boat down into the water as it was sitting on the hull and was not stable, I had some lead in the back as well as I used a spirit level when I was sorting it out in the bath, however when I first tried it in the pond the back end was too low in the water when it was going, so I took the heavier weight from the section just rear of the motor compartment and swapped it for the lighter weight just forward of the motor compartment, although this was better when tried again the stern was too low when it was moving so I removed the weights from the stern and as far as I could see it was just right, stationary the boat looked levelish but when moving on full throttle, the bow came up and had a nice bow wave with the stern down below the water level but with a (for want of the technical term) a hollow wave, when on a slower throttle it was fine and sailed nicely at all speed levels. What worries me is that the motor shown fitted in the boat was supposed to be the better motor than the photo of the one outside of the boat, would this benefit from a water cooled motor as to be honest I would not want to alter the top speed of the boat as it is just about right .
just to let you all know I have a background knowledge of electrics so do know the difference between parallel and series voltages😊


enjoyment is important.
RichardSReade
(Sub-Lieutenant)





Forum Posts: 22
5th Nov 2017 22:13  
>> Permalink
mdlbt.com/35394

After reading your post Jarvo I went out to the workshop to check if the motor would run, it had got so hot it had melted the solder on the live feed connection so in a way saving it from going right up in smoke, an inline fuse may be a thing in the future, the motor is completely burnt out however the power box is OK.
Thank you for the information about the larger motor, I am not sure which is the larger out of the two, I have posted some photos of them both as I am not up to speed with the rating numbers of the motors,maybe you could answer that question.
However following up from Scout13 reply, although the cover over the prop shaft connection was in no way restricting air flow, ( I will drill some air flow holes in the cover to be 100% positive on that statement.
The motor fixing bracket and the RE540/1 motor recommended for the Sea Commander and sold to me by the model shop, (I was given the other motor by a club member as I was informed it was the better out of the two) looks like the problem, if you look at the photo's you can see that the air flow holes are completely blanked out by the bracket, something I missed when fitting it.


Attached Files - Click To View Large


enjoyment is important.
jarvo
(Fleet Admiral!)





Forum Posts: 466
5th Nov 2017 22:35  
>> Permalink
mdlbt.com/35395

Hi Richard, looking at the markings on the motor case, it might be a 550 type, and rated at 7.2 volts, so it would seem to be at the top end of its capacity, did you manage to get the prop diameter? also is it plastic or brass?
A 600 motor is a bit larger size and power wise but would still fit your motor mount, they are common in power drills so usually have plenty of torque, but can be power hungry. A prop to suit would be about 40mm, 2 blade or 35mm 3 blade both in brass, plastic props tend to be racing types with deep cuffs on the blades, possibly the cause of the burnout!
The 850 is a lot larger and more powerful but would need a new mount and again is power hungry, probably needing 12 volts as well.
Have a look on ebay 600 motors are about £5, but check to see what the rating of your ESC is, needs to be at least 20amps, although if it survived cooking the old motor it must have a good rating. Add a 15 - 20 amp fuse for protection.
Just had a thought, is the prop shaft stiff to turn? should spin freely without the motor connected, might have old oil or grease in the tube causing excessive drag, this could cook the motor as well.
A pic of the prop and its size would be a great help.
Hope this helps
Mark


Etherow Model Boat Club
RichardSReade
(Sub-Lieutenant)





Forum Posts: 22
5th Nov 2017 23:05  
>> Permalink
mdlbt.com/35396

reading my previous post I got it wrong the heavier weight is noe in the compartment behind the motor with the lighter one forward of the motor compartment,
The prop is a three bladed brass one so difficult to measure the diameter when on the boat, but each blade from the center is just 30mm, the power box is an Aquapower digital speed controller model AQP128. The prop shaft spins freely
Will be retiring to bed now so will check any replies tomorrow, thank you all for the help and advice


Attached Files - Click To View Large


enjoyment is important.
reilly4
(Lieutenant)





Forum Posts: 14
5th Nov 2017 23:13  
>> Permalink
mdlbt.com/35397

Hi Richard, If each blade is 30mm from the shaft centre, it is a 60mm diameter propeller and is far too big for that size motor.
For performance you need a larger motor say a Graupner 700 and I would still recommend a smaller propeller.

Haverlock
(Fleet Admiral!)





Forum Posts: 423
6th Nov 2017 01:10  
>> Permalink
mdlbt.com/35401

At the risk of being repetitive get yourself a watt meter that way you can see how much current your motor is drawing. If a motor overheats you are either running to high a voltage or to big a prop. If you are intending to push the envelope you can buy a cooling coil to fit over your brushed ( or inrunner brushless) motor and use a water scoop thus water cooling your setup.


"that's not a bug its just an undocumented creature."

Sir Terence David John "Terry" Pratchett, OBE (28 April 1948 - 12 March 2015)
RichardSReade
(Sub-Lieutenant)





Forum Posts: 22
6th Nov 2017 04:21  
>> Permalink
mdlbt.com/35402

Hi reilly4 I do not think it is as large as 60mm as it is a three bladed prop, if it was a two bladed one I would agree with you as the blades would be directly opposite each other hence 60mm, but being 3 bladed they are not 90 degrees to the centre point, without taking it off and drawing a circle around it to measure I would hazard a guess it is a 30mm prop. If memory serves me correctly the late Swindon Model Shop which was run by Yan who knew his stuff recommended the 540 motor along with the prop for the size of the boat. I will check the Sea Commander plans as I think it has the size of the required prop listed.
Haverlock the motor is rated 4.5 to 15 volts and the battery is 7.2 volt, I would have to run the boat in water to see what the motor is drawing under load, I may get a tad wet trying to keep up with it to read an amp meter, or sink the boat by sitting on it😉 I think the overheat problem was to do with the motor mounting braket covering the front air slots on the motor.
However I have a water scoop which I did not fit at the time of building so may retro fit and buy a new motor set up for water cooling, the next question would be where abouts do I fit it?


enjoyment is important.
reilly4
(Lieutenant)





Forum Posts: 14
6th Nov 2017 04:31  
>> Permalink
mdlbt.com/35403

Richard,
If as you said each blade from shaft centreline to tip of blade is 30mm then it would not matter if you had two blades or ten. If the radius (your measurement) is 30mm then the diameter is 60mm. Perhaps you can remove the prop and place it on a flat surface so you can see the swept circumference when rotated.

Haverlock
(Fleet Admiral!)





Forum Posts: 423
6th Nov 2017 05:52  
>> Permalink
mdlbt.com/35404

RE850 Motor 12.0 Volt with mount
Ref: MFA457RE850

8000 RPM at 11amps at maximum efficency. Ideal for large models and props up to 75mm with direct drive.

Output shaft dia is 1/4 in

http://www.model-dockyard.com/acatalog/Direct_Drive_Motors.h...

hope that's some help


"that's not a bug its just an undocumented creature."

Sir Terence David John "Terry" Pratchett, OBE (28 April 1948 - 12 March 2015)
canabus
(Admiral)





Forum Posts: 64
6th Nov 2017 07:27  
>> Permalink
mdlbt.com/35406

Hi
I use a Turnigy 180Amp watt meter and power analyzer(part No.9598000004-0) 0-60 volts , size 85 x 42 x 25mm, 82 grams.
Requires your battery connectors.
Use it in line with the main battery on board the boat.
We used it on my mate's Spearfish and got 72.88 Amps on a brushless motor at 37 KPH.

Canabus

RichardSReade
(Sub-Lieutenant)





Forum Posts: 22
6th Nov 2017 08:01  
>> Permalink
mdlbt.com/35407

Reilly, I stand corrected I see what you are saying, the speed of the boat is just about right, if I fit a smaller prop then I will need a much faster motor to keep it at that speed then I presume the battery will not last as long, in fact that is something I would like to work out, although I am ok with wiring and working out loads at mains voltage etc. my ohms law is useless with DC voltage and mAh
Haverlock I had a look at that motor but I see the recommended motor mount would block of the front air holes again (same mout as I have)
Canabus thanks for that sounds expensive besides which I have spent out nearly, my pension does not really extend to this hobby, but enjoyment is important.
I wonder if the last three words of the previous paragraph is a quote from some famous person I could add to the bottom of my posts😁


enjoyment is important.
jarvo
(Fleet Admiral!)





Forum Posts: 466
6th Nov 2017 08:02  
>> Permalink
mdlbt.com/35408

Hi Richard, Good morning, Prop first, if the blade to hub is 30mm, it is a 60mm diameter prop, think of the circle of sweep, twice the size that your 550 motor can take.
As the shaft is free running, we can discount drag, simply the motor working to extreme, so we need to prop down considerably,
If you are staying with the 540 motor in the pics, a 35mm 3 blade prop is the maximum, a rough guide is no bigger than the motor diameter.
I would save myself a lot of problems in the future and fit a larger motor, Canabus is right a watt meter will save its readings so you can get a proper idea what the motor is doing.
I would swing towards the 850, or the 700. Not expensive but safe to run with a smaller prop.
The 700 might fit your mounting but the 850 will need a new one, usually supplied in the box.
The Sea Commander will serve you well as a great sailing model, once you are past the teething problems.

Just looked back, your first post said the hull was built in the 60's, it might have a 4ba thread, not many ba props available these days, a 4mm prop will fit but it will be tight, don't forget the locking nut (to many props at the bottom of the lake) also a thrust washer to protect the motor bearings.
Mark


Etherow Model Boat Club
Haverlock
(Fleet Admiral!)





Forum Posts: 423
6th Nov 2017 08:14  
>> Permalink
mdlbt.com/35409

the scoop should be fitted behind the prop so prop wash is driving water through it whenever the motor is running and the cooling coil fits around the motor join the two up with fuel tube etc. then the other end of the coil connect to an outlet ( unless you want a self filling boat)

http://www.cornwallmodelboats.co.uk/acatalog/cooling-coils.h...

http://www.cornwallmodelboats.co.uk/cgi-bin/sh000029.pl?REFPAGE=http%3a%2f%2fwww%2ecornwallmodelboats%2eco%2euk%2facatalog%2fcooling%2dcoils%2ehtml&WD=scoop%20water&PN=water_cooling%2ehtml%23aG1427#aG1427


As to sitting on your boat you could put it in the water and get some one to hold it while you run the motor up and watch the current used.

closing off the cooling vents to an electric motor not used in a speed model shouldn't be any problem if you have the correct prop an electric motor should only get hand warm. The temps you indicate would have burned out your motor even if there had been no covering over the motor at all. With an electric ( brushed) motor the more you load it the higher the current flow and the hotter it gets. Stall current tend towards infinity you have what I think is a 60mm prop and that's a BIG prop being 3 bladed makes the situation worse since there is increased blade area against a 2 bladed prop. If you intend to use that prop then get a motor man enough to swing it.


"that's not a bug its just an undocumented creature."

Sir Terence David John "Terry" Pratchett, OBE (28 April 1948 - 12 March 2015)
RichardSReade
(Sub-Lieutenant)





Forum Posts: 22
6th Nov 2017 09:51  
>> Permalink
mdlbt.com/35413

Thank you gents, I will get a bigger motor and reduce the prop size as I do not want it any faster than it is, also a smaller prop as everyone has said will reduce the power drained from the battery, I have a water scoop and tubing so will be fitting that today and will fit a water jacket around the motor, also I am thinking weighing the lead weight fitted in the compartment behind the motor and replace some or all of it and fit a 12 volt 7 amph sealed lead acid battery, presumably this will last longer than the present batteries fitted, or will it?


enjoyment is important.
pmdevlin
(Fleet Admiral!)





Forum Posts: 329
6th Nov 2017 10:13  
>> Permalink
mdlbt.com/35415

for the purpose of testing, don't go out and buy expensive props, just buy cheap plastic two blade ones, I always use "x" blade, they are a coarser pitch, "s" blade are less pitch. Get a few to test, 35mm, 40mm, 50mm. Fit, short run, see how hot things are. Whilst you don't want to go fast, don't forget this is a big heavy old girl, its better to be overpowered than under powered.

If it was me, I would get a graupner 700, watercool with a cooling coil, probably settle with 45 to 50mm two blade "x" prop, run on 12v, this will give some speed and durability. Don't assume that just because the model shop suggested it, its the holy grail, many many times we have seen evidence of very poor advice given by so called experts😡

https://www.ebay.co.uk/itm/Graupner-Speed-700-Turbo-Electric...

jarvo
(Fleet Admiral!)





Forum Posts: 466
6th Nov 2017 10:14  
>> Permalink
mdlbt.com/35416

Hi Richard, with a bigger motor and smaller prop you may not need the water cooling, none of my boats have cooling, what i would say is that switching to a gel battery will be heavy, stick with your 7.2v batteries and give it a try, it might last a bit longer but with your twin battery set up you will get about the same run time.
Mark


Etherow Model Boat Club
Haverlock
(Fleet Admiral!)





Forum Posts: 423
6th Nov 2017 10:43  
>> Permalink
mdlbt.com/35418

I had a quick look around and discovered this

hull matched 12V 750 Speed electric motor, hull matched 40mm 2 bladed prop this from

http://www.cornwallmodelboats.co.uk/acatalog/aerokits-sea-co...

However if you want performance

http://www.kingslynnmodelshop.co.uk/Motors_and_Speed_Control...

That should give the equivalent power output to a .40 IC engine and make the hull come to life the way it was intended to. Couple that to a LIPO battery and a suitable ESC.

Remember when the kit was originally made IC was the norm
The Sea Commander was introduced by Aerokits at Gorleston Norfolk in the early 1950s. Designed by L J Rowell the Sea Commander is a smaller version of the Sea Queen. The length is 34 1/4 inches by 10 3/4 inches and is almost identical except there is no mast. Intended for the ED Marine Racer and Hunter power plants


"that's not a bug its just an undocumented creature."

Sir Terence David John "Terry" Pratchett, OBE (28 April 1948 - 12 March 2015)
RichardSReade
(Sub-Lieutenant)





Forum Posts: 22
6th Nov 2017 18:41  
>> Permalink
mdlbt.com/35425

I looked at the Cornwall model site and saw that, what i have decided to do is to leave the two Ni cad batteries in situ and I have weighed the rear/mid section lead weight and it is just 56 grams heavier than the 12 volt 7 amp/h lead acid alarm battery so I will use the 12 volt battery and ditch the lead, the weight of the boat will be the same, I also trimmed the lead at the front end so the bow will come up a fraction more.
I have taken the prop of and measured it to be a 55mm, so I am going to fit the water intake, hopefully with some advice from the forum "techys"as to the position, in the photos this is where I can fit it so it is out of the way of the rudder and prop.what do you reckon, I can then get a suitable motor with a water jacket which will be happy to run on 12 volt with enough power not to get hot turning a 45 to 50 mm two blade "x" prop, as suggested by pmdevlin, I may get the Lloydsman up and running as all that needs is dusting of and batteries charging up, (two 12 volt 7amp/h in parallel) and the receiver from the commander fitted although I have not floated it I bought it as a complete working model in 2015, so it is about time it came out of dry dock, also I can look to repairing the rigging and finishing the Odessy Yacht I bought at the same time as the Llyodsman also in dry dock.


Attached Files - Click To View Large


enjoyment is important.
Haverlock
(Fleet Admiral!)





Forum Posts: 423
6th Nov 2017 21:23  
>> Permalink
mdlbt.com/35429

before you fit a water cooling system try a smaller prop. You need to think of the gearbox in a car. Too big a prop can be looked at as being like trying to drive off in top gear! A smaller prop will allow any given motor to spin faster and strange as it may seem use LESS not more current. If you keep the drawn current down to the limits set by the motor constructor then its probable you will need no extra cooling. If the boat moves faster than you want use the throttle its what its for. Throttling down also extends battery life. The air intakes on boats like this were intended for IC engines and they NEED air to work.


"that's not a bug its just an undocumented creature."

Sir Terence David John "Terry" Pratchett, OBE (28 April 1948 - 12 March 2015)
RichardSReade
(Sub-Lieutenant)





Forum Posts: 22
7th Nov 2017 12:18  
>> Permalink
mdlbt.com/35447

Hi all I have located an 850 motor and mount at Howes Models in Kiddlington not too far from where I live in Malmesbury, for £22.50 however the prop shaft is 4BA, the coupling is not a problem as I can get the insert for the larger motor to fit the existing red coupling, but I can only seem to find 4mm 40 or 45mm propellers which are a fraction bigger than the 4BA which I know will screw on but they would have a bit of a wobble on the threads and could give me an out of balance vibration, apart from drilling out the old propshaft assy and fitting a new 4mm one what else can I do? or does anyone have a old 4BA prop they can let me have?


enjoyment is important.
pmdevlin
(Fleet Admiral!)





Forum Posts: 329
7th Nov 2017 20:28  
>> Permalink
mdlbt.com/35460

Hi Richard

I'm going to be blunt here, no intention to offend, but, You get a donation of some random ancient 4BA prop, you are no further on, as you are stuck with one prop. You have yet to decide which size prop will suit, and, as time goes by, and you consider updating your drive train, that 4BA is going to continually hold you back. Get it out, a new propshaft, 4mm, or even 5mm (all my boats run 5mm) might even fit your original outershaft and away you go.

Slightly off topic, but, the cost of very average brushed motors and yesterday technology is now more expensive than Brushless, which is way more efficient, I wonder how much longer the model shops can survive touting this over priced dated equipment, RC Boats is the only RC discipline holding on to this out of date technology.

Back on topic!🤐 You could also see if you have any room to cut the threaded end off, and visit the local engineering shop, get them to thread the end 4mm or whatever suits. I remember beiung in exactly the same position on my first serious boat, my 36" aerokits Fireboat, build in the sixties by my uncle. I was with my mate, and mentor, having the exact same conversation, I was holding on, saying I'm not changing the shaft, he dropped something on the floor, I bent down, when I stood up, he had a pair of molegrips dragging the propshaft out, I could have cried, but never looked back. I then did extensive testing with a load of cheap props, and when I got it sorted, treated myself to a real nice brass prop, size based on the testing results👍

RichardSReade
(Sub-Lieutenant)





Forum Posts: 22
7th Nov 2017 20:38  
>> Permalink
mdlbt.com/35464

I like Blunt, the guy a Howes model shop, who was into boats himself retired and only worked there a couple of mornings a week, also said to remove the complete shaft and replace it with a metric one much the same as yourself, it is just the thought of what damage I may do to the boat as I know I fixed it in really well, he also said to get a 4mm prop-shaft and to see if the shaft would fit into the existing tube, so I am going to take both your advice and at this time go for a 4mm but try the shaft first, however I do not think pulling it out with mole grips will work on this occasion.
Watch this space😡
Thanks


enjoyment is important.
pmdevlin
(Fleet Admiral!)





Forum Posts: 329
7th Nov 2017 21:40  
>> Permalink
mdlbt.com/35467

Hi Richard,

molegrips to get the lot out, outershaft and all, its very painful, squeeze tight and twist, you will be supruised how it comes out with some tapping.
You could get the bearings out of the top and bottom of your existing shaft, if they look like black plastic, put the shaft in, catch the edge from inside and knock out, they are opush fit, then replace with new 4mm/5mm aceteal, (no doubt spelt wrong)a quid or so each, and are water lubricated. SHG Marine do all of this, they are good at props. If they look metal, they will be either brass, or bronze, and you will prob have to heat the end of the shaft. Try the tapping method, you might get lucky.
so now, original outershaft still in place, no bearings either end, and you need a new mm shaft, get stainless. The trick is now, getting bearings to fit if its a real old shaft. Is a good time now to fit an oiler tube whilst everything is out, and clean using thinners etc any gungle inside the shaft. After all this, its not much more effort to get the old one out, and epoxy a new one in, you can buy it complete with inner and outer shafts, bearings, and the right thread, and a couple of test props whilst the wallet is out! Never said it was going to be easy😜

Haverlock
(Fleet Admiral!)





Forum Posts: 423
8th Nov 2017 05:33  
>> Permalink
mdlbt.com/35474

before you start ripping out your prop shaft an 850 should be able to use your existing prop.

Specifications of 800 and 850
Overall length 110mm (4.3/8’’) - Width (inc. fixing plate) 50mm (2’’) - Weight 585g (20.6OZ) - Voltage 12v DC (reversible by reversing polarity) - RPM for 800 (no load) 5100 & for 850 (no load) 9778 - Current consumption for 800 (no load) 1 amp- maximum efficiency 5.3amps-suggested maximum continuous 7 amps-current consumption stalled 28amps and for the 850 Current consumption 1.9amp (no load) - maximum efficiency 10.8 amps - suggested maximum continuous 13 amps - current consumption stalled 40 amps - Suggested prop size for both motors: 45,50,55 & 62mm in 2 blade nylon or equivalent 3 blade brass


"that's not a bug its just an undocumented creature."

Sir Terence David John "Terry" Pratchett, OBE (28 April 1948 - 12 March 2015)
RichardSReade
(Sub-Lieutenant)





Forum Posts: 22
8th Nov 2017 07:20  
>> Permalink
mdlbt.com/35475

I have a brass tube and stainless shaft with no bearings fitted at the moment.
I thought the advice was to fit a bigger motor and smaller prop, to keep the motor from running hot and to hopefully save the battery, you say an equivalent three blade prop, that is what is fitted (55mm 3 blade) so where does that come on the chart? as if it is still too big then I am no further forward


enjoyment is important.
Haverlock
(Fleet Admiral!)





Forum Posts: 423
8th Nov 2017 09:53  
>> Permalink
mdlbt.com/35479

Your original motor was a 650 and you had it over propped so its current draw was way to high so it burned out because it couldn't spin fast enough. The 850 is a MUCH more powerful motor and should be able to handle a 50mm prop. The 850 will spin faster so less current drawn ( I know that seems counter intuitive but its how it works) Your boat will probably go faster but you can throttle back to get the speed you want.


"that's not a bug its just an undocumented creature."

Sir Terence David John "Terry" Pratchett, OBE (28 April 1948 - 12 March 2015)
RichardSReade
(Sub-Lieutenant)





Forum Posts: 22
8th Nov 2017 10:14  
>> Permalink
mdlbt.com/35480

Great I will order the 850 motor and try it out before I do anything else
Thank you again for your help


enjoyment is important.
pmdevlin
(Fleet Admiral!)





Forum Posts: 329
8th Nov 2017 13:04  
>> Permalink
mdlbt.com/35487

here is the problem Richard, when you ask for advise on an open forum, you get a few individual takes!😁
IMO, its not so much the motor at this stage, its the ba thread thing. You can stick a Ferrari v12 in there, but you still need to consider how to attach the thing that is actually going to drive you along, a prop, be it 2, 3 or more blades

Whilst buying the 850 motor, take the boat into the shop and get the bearings for your outer tube, and a new mm stainless shaft, and any couplings that are needed. If the outershaft is a size that will not accommodate any new bearings, then it will have to come out, regardless of the motor (don't forget a mount) that you buy.
The suggested nylon 2 blade prop sizes that Havelock has posted in the motor spec are what I suggested a few days ago. Don't forget, that spec etc is generic, its not going to be "fit all" its down to you to test and establish what works best for your boat, we don't know its weight, and the condition of your batteries etc.

pmdevlin
(Fleet Admiral!)





Forum Posts: 329
8th Nov 2017 13:25  
>> Permalink
mdlbt.com/35492

the good news is, (I should have mentioned this earlier), the contributors here are generally experienced, and have done it themselves, so rest assured everything you get is proven, you just need to pick out what is best for you. Some other forums are not as lucky, as you get a lot of "do this, try this", you go out spending the dosh, and the "advisor" when challenged has not actually done it himself, its just a load of crap.😡 really annoys me that this happens, and sometimes people on model shops can be just as bad. A mate of mine took his sons "toy" boat to a local model shop last year. His son had outgrown it, my mate wanted to paint it, make it his own, and ditch the "toys r us" running gear. I didn't know he had done this, when I saw what had been done, the money charged, we marched back to the shop, I gave the "expert" the crap back, and got a refund. 2nd hand 27mg 2 channel rx with the aerial chopped to 6 inches, a 4x1.5 aa battery holder for main propulsion, and a really tired 2 channel acoms 27mg tx £75😡
I found out when he asked me why the lights don't work from the tx like my boats, he had asked for this, 2 channel set, hmm....
later that month, with a 7.2v nims and a dx6 with now 6 channels, less than £50, experts eh! I know there are good, but this shop or at least the guy working there wasn't one of them

RichardSReade
(Sub-Lieutenant)





Forum Posts: 22
8th Nov 2017 13:35  
>> Permalink
mdlbt.com/35494

Fair enough pmdevlin I accept what you are saying, however it started as a motor not being big enough for the size of the propeller and then went on further as the shaft was 4BA not 4mm and I could not locate a smaller prop, a plain brass tube and stainless shaft has been fitted,way back in the 60's when it was first started and as I knew nothing about boats in 2015 when I finished the basic structure, I did not know that it would have been the smart thing to fit a shaft with bearings.
So this is the way I am going to go, I have ordered the 850 brush motor and the adapter to fit the motor shaft to my red coupling,this I have been assured will be more than big enough to drive the prop without getting hot or needing a water jacket, if this is the case when I fit it and sail it, then result, if not I will then have to go down the path that you suggest, I have nothing to lose trying the larger motor and everything to gain if it works.
By the way the batteries are all new


enjoyment is important.
pmdevlin
(Fleet Admiral!)





Forum Posts: 329
8th Nov 2017 13:45  
>> Permalink
mdlbt.com/35496

yeah I agree Richard, I sort of went away from topic there. I've had a look in the man shed, I have some 4ba taps, so if you need some props, get some mm ones (poss 3mm as 4 mm is bigger?) and if you need them I can drill and tap for you. Also, if you use a cheap plastic prop, you can use a 4ba nut on the shaft with some thread lock, and lock the 4mm prop up against it. Pity you are not closer, I would have done it for you whilst here.
Good luck!
Paul

Haverlock
(Fleet Admiral!)





Forum Posts: 423
8th Nov 2017 13:46  
>> Permalink
mdlbt.com/35497

do a test run in the bathtub you can leave the superstructure off and use the throttle while holding the boat in place make sure you wife is out so the bathroom has time to dry out afterwards. Give it a run and see how hot the motor gets. The 850 is specified such that your prop should be fine. Please remember to include a locknut otherwise if you select reverse your prop could unscrew while sailing and you may lose the prop. Let us all know how you get along and enjoy .


"that's not a bug its just an undocumented creature."

Sir Terence David John "Terry" Pratchett, OBE (28 April 1948 - 12 March 2015)
RichardSReade
(Sub-Lieutenant)





Forum Posts: 22
8th Nov 2017 14:16  
>> Permalink
mdlbt.com/35498

Thanks for the offer Paul, however I have a large amount of tools and equipment having been a service engineer, also into British motorcycles and old cars previously and had a magpie attitude to all things tools including taps and dies,helicoils and the like, I also have a boxford lathe so am capable of making the odd items when needed. Another thing I have learnt, 3mm props are available, and yes if needed I can drill and tap it to 4 BA (I have most of the BA taps and some dies) that will also save having to rip the boat apart.
Yes Haverlock trying it in the bath would be a good idea, however I have a friends pond just down the road and think it may be a bit prudent to use that.😆


enjoyment is important.
RichardSReade
(Sub-Lieutenant)





Forum Posts: 22
9th Nov 2017 18:27  
>> Permalink
mdlbt.com/35601

the motor has arrived today so into the workshop this afternoon, of course it is not going to be straightforward, the motor is much larger than the 540 size so the motor platform is too high. I fixed it down well, I did not want this to come loose, managed to cut it out with one of those vibrating cutter, just leaving the glued pieces to remove , not too difficult with a small wood chisel. So in the process of making a motor platform with new stringers so the platform is lower in the hull, break for tea, now going in to workshop to fix down the stringers to the hull and bulkheads with 2 part epoxy, The motor mount has been fixed to the platform with small nuts and bolts with a locking washer, I am going to epoxy the heads to the underside of the platform, so I can undo the nuts without the bolt spinning, not sure how I will fix the platform in as there is not much depth on the stringers to use screws, so I guess two part epoxy again.
Should I start a blog as I think this may be an ongoing tale of woe😊


enjoyment is important.
RichardSReade
(Sub-Lieutenant)





Forum Posts: 22
9th Nov 2017 22:38  
>> Permalink
mdlbt.com/35625

Motor fitted to platform and luckily there was enough depth to screw the motor platform to the stringers, I have moved the reciever forward to where it was and resecured the powerbox in a better position, just the leads with the bullet connectors from the motor to fit, although I have fitted the sealed lead acid 12 volt battery instead of the lead ballast (same weight) I have left the7.2v in situ as I trimmed the boat with them in and will see how it goes, it may have too much power on 12 volt and at least if my finger on the stick lacks control on the speed, I can slow things down by swapping over to the 7.2v batteries.
If and when the sailing side is sorted, after seeing the pictures of members boats and ships, I think I will give it a good rub down and respray and smarten the inside up as well.
Eventually I will get on with the Lloydsman


Attached Files - Click To View Large


enjoyment is important.
Haverlock
(Fleet Admiral!)





Forum Posts: 423
9th Nov 2017 22:50  
>> Permalink
mdlbt.com/35626

using a lead acid is ok BUT a LIPO can deliver more current. See how things go and consider a LIPO in the future to increase performance.


"that's not a bug its just an undocumented creature."

Sir Terence David John "Terry" Pratchett, OBE (28 April 1948 - 12 March 2015)
jarvo
(Fleet Admiral!)





Forum Posts: 466
9th Nov 2017 23:32  
>> Permalink
mdlbt.com/35628

Hi Richard, did you mean you are sailing with the SLA and the 2 NiMh batteries on board?
She is a heavy model already, remove the NiMh packs to take some of the load off the motor, she needs to be able to plane, the extra weight will hold her down

Mark


Etherow Model Boat Club
Haverlock
(Fleet Admiral!)





Forum Posts: 423
10th Nov 2017 07:42  
>> Permalink
mdlbt.com/35635

I have to agree with jarvo remember the original boat was intended to have an IC engine and the radio control of the 1960s. Transistors were in use and the radio gear while it was bulky was not that heavy. Personally I would recommend you remove all of your batteries and stick in a decent 3cell LIPO. Where are you trying to ballast your boat down to? The originals ran with little if any extra ballast purist would say they were over scale speed but you have a throttle stick.


"that's not a bug its just an undocumented creature."

Sir Terence David John "Terry" Pratchett, OBE (28 April 1948 - 12 March 2015)
RichardSReade
(Sub-Lieutenant)





Forum Posts: 22
10th Nov 2017 09:22  
>> Permalink
mdlbt.com/35640

the first time I sailed the boat with the old motor she was fast and literally stood up in the water on half throttle with just the lead acid battery and no ballast, it was sitting with the back end about half an inch above the underside skins and the bow was well out of the water, I was advised by one of the club members that I needed to trim the boat so it was down at the front but keeping the stern approximately where it was, therfore the lead in the compartment forward of the motor and the battery in the compartment behind. However the 5000mAh and the 3300mAh batteries are not connect and are only held in place with a bit of velcro, also the lead in the front is just shaped to the hull and cannot move, but I can lift it out, so I will see how it runs next week


enjoyment is important.
pmdevlin
(Fleet Admiral!)





Forum Posts: 329
10th Nov 2017 10:23  
>> Permalink
mdlbt.com/35643

Hi Richard,

that lead acid is way too big and heavy. I Remember going on hols as a kid, car was loaded up, all family, roofrack, deck chairs, tent and so on, and Dads old Moggie Traveller would barely climb the Welsh hills! Same here, its just dead weight, ideal for a tug etc, no speed required, and ballast needed. This boat wasn't any slouch in its day, As Havelock says, it was originally built as a ic powered model so could stand being heavy.
To achieve balance, its a matter of moving things around, not adding, so just move things forward, you will be surprised how the weight increases once you start adding Deck clutter, fittings and so on. Lightweight, is good.
Your comment, stood up in the water at half throttle isn't going fast, its just bad weight displacement causing the bow tyo be too high. That setup would never have been that fast, the motor/battery combo will never cause a heavy ply boat to be going that fast its standing on end
Couple of things to consider. Your nimhs, how many times have these been cycled, and what sort of charger are you using? A reasonable charger will give the information, if I know what you are using, Ill advise accordingly as you might not be getting the best from these batteries
what prop are you on

Think of an rc plane (if you fly them its easier) If the cog is too far back, the nose is pitching up, and its almost impossible to control, it almost porpoises in the air, and is very bad. COG is vital on a rc plane, nose heavy is better, only because its more controllable. COG is equally important with a boat, but harder to see the implications, the hull will give us false info, such as if the bow is up its on the plane, no, not necessarily, its not planing due to speed, its just out of balance. Shifting the weight radically will let you see this, sorry for the ramble, Wish you where closer to me I would love to help hands on👍

Ive tried to find a suitable video of my Huntman to display what I'm rambling on about. This video is poor quality, but it displays that boat moving very fast (25mph with on board data logger) but look how flat it is, its planning, as the forward 1/3 of the hull is out of the water, but its not standing on its tail, this is because its balanced. You boat is pretty similar in design to this so whilst you wont want to go this fast, the picture should look the same. This Huntsman weighs 6kg with batteries (lipos, you will NEVER get a nimh or lead acid to do this) and is 4 foot long, so quite a heavy old girl first constructed as an IC model in the early 70's.
https://www.youtube.com/watch?v=e5-YmmElIfk&t=34s

and here is a picture of my 3 foot aerokits fireboat, bow up, is it planing, no, its way out of balance, it wasnt actaully going that fast

Hope that helps
Paul


Attached Files - Click To View Large

RichardSReade
(Sub-Lieutenant)





Forum Posts: 22
10th Nov 2017 14:16  
>> Permalink
mdlbt.com/35651

very interesting Paul, I watched the video, I have weighed the boat as best I can, using the kitchen scales, the boat without any batteries or lead is 6Ib 3 oz (2815 gms)the lead ballast is 2 Lb (915 gms)the lead acid battery is 5Ib 9oz (grams) and the two NiMH batteries are 1Ib 10oz (747 gms) the boat now has an 850 motor with a 55mm 3 bladed prop, I do not have the experience to know whether the boat is sitting correctly without the ballast but do know that if I have the lead acid 12volt battery fitted in the only place it will fit then I need the ballast in the forward compartment making the boat weigh 13 Ib (6252 gms). if you are saying that I should keep it light then I could move theNiMH batteries to the compartment rear of the motor thus moving the weight towards the back and ditch the LA battery and lead ballast, I have no idea which part of the country you reside in, is it too far for me to drive to? as your sailing pond looks a lot better than the postage stamp we have to use in Swindon.


enjoyment is important.
RichardSReade
(Sub-Lieutenant)





Forum Posts: 22
10th Nov 2017 18:50  
>> Permalink
mdlbt.com/35655

further to my previous post, I have now fitted the two NiMH Batteries (not nicad as I kept saying)in the rear compartment, held in with Velcro, and tidied the wires up and fitted an inline fuse, yet to be wired, the boat is much lighter, however all the other Velcro is still in place so I can move them forward if needed and fit the lead or Lead acid battery, so one visit to a pond and hopefully I can get it sailing correctly, my problem is I would not know what is correct and what is not, at least I have Pauls video as a reference.


Attached Files - Click To View Large


enjoyment is important.
RichardSReade
(Sub-Lieutenant)





Forum Posts: 22
12th Nov 2017 21:33  
>> Permalink
mdlbt.com/35716

Sorry to keep asking questions but although I finished this in 2015 it is my first rc boat, in fact my first any boat, the first time I went to water so to speak, was three weeks ago, I am learning new things by reading the posts on this forum
I have just read the post by RMWall107 about his boat and someone mentioned the angle of the prop-shaft with regards to an ic and electric motor angle, as my father who started the build in the 60's and was into his r/c aircraft I suspect he was going to fit an ic motor and fitted the prop accordingly. Can someone tell me the correct angle for an electric motor with any tolerances and also what the problems will be if the angle is too far out.
Thanks


enjoyment is important.
jarvo
(Fleet Admiral!)





Forum Posts: 466
12th Nov 2017 21:57  
>> Permalink
mdlbt.com/35721

Hi Richard, the angle is steep to allow the starting flywheel of an i/c motor to clear the keel. This angle was quite steep, but with the motor's power it allowed the hull to run quite fast.
Electric motors are a lot smaller so a lower angle of about 15 degrees, will work well, this will give more forward thrust without forcing the bows down wasting power, lifting the stern upwards in the water.
Mark


Etherow Model Boat Club
canabus
(Admiral)





Forum Posts: 64
13th Nov 2017 06:33  
>> Permalink
mdlbt.com/35734

HI Richard
I drop my prop angle to 9 and 1/2 degrees on my Precedent Huntsman 34" after removing the old IC motor.
Running a 35 mm brushless motor on 3S and it's very quick!!
More a speed motor than a motor cruiser.
Canabus

RichardSReade
(Sub-Lieutenant)





Forum Posts: 22
13th Nov 2017 23:26  
>> Permalink
mdlbt.com/35781

Thanks chaps at a rough estimate and using the keel as the straight edge it is about correct for the electric motor. new cables and connectors along with a couple of mini servo's, arriving tomorrow, which I intend to rig up to operate some micro switches for lights and the like, cheaper than pukka switches.
Jarvo and pmdevlin, when I can get the boat to water I will take some photo's and maybe a video with the battery's in the rudder compartment and also in the compartment just rear of the motor to see what you both think.


enjoyment is important.
jarvo
(Fleet Admiral!)





Forum Posts: 466
13th Nov 2017 23:38  
>> Permalink
mdlbt.com/35782

Richard, its going to be great to see your boat on the water, video would help even more
Mark


Etherow Model Boat Club