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Author Topic: Ok what am i doing wrong??  (Read 8047 times)

portside II

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Ok what am i doing wrong??
« on: June 16, 2007, 09:45:27 pm »

 ???
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portside II

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Re: Ok what am i doing wrong??
« Reply #1 on: June 16, 2007, 10:03:26 pm »

damn your quick  ;D
whoops lets try again

right dint know if its a wood trees thing but the wiring on my nangee is doing my head in
I have a pair of johnson motors out of a couple of B&D drills wired in parallel to an electronize FR15HVR esc .
which is powered by two 12v 7ah bat's .
the motors under load in the test tank with the meter on the battery draw 4.5 amps at full chatt and 2.5 amps at half speed .
then the probs start ,after a short while the esc heats up and starts to smoke/smell so it's foo with the power fast and after a few minutes all is well and the esc is OK
the amps dont change from bat to esc ??.
I have tried the same set up on 6v amd all is ok apart from the grunt, there isn't any which is no good as its supposed to be a tug ,
i have only to check the draw between the esc and the motors to see what that is whether that may show the problem i dont know as the battery's can supply 12v at 14 ah ?? .
a bit of advice would be appreciated as i don't want to kill the esc
daz
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FullLeatherJacket

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Re: Ok what am i doing wrong??
« Reply #2 on: June 16, 2007, 11:19:00 pm »

Daz

You is damn right! Hot speed controllers and smokey smells means that you ain't doin' nuthin' no good with what you got, mister!

For a start I wouldn't run two of these motors off one ESC, but that's a personal thing (and not just because I sell ESCs......). Have a look at my little article on Twin Motors on the main Mayhem website; you should concentrate on the option with 2 coupled speed controllers - that's the second diagram down.

In my book two motors should have two batteries and two speed controllers - it keeps it simple and it works every time for me. PM me if you need any further info.

FLJ
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gribeauval

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Re: Ok what am i doing wrong??
« Reply #3 on: June 16, 2007, 11:43:28 pm »

It may seem an elementary question but have you got the batteries wired to the esc in parallel, i.e 12v 14 AH or have you wired them in series, i.e 24v 7AH. If the latter then the esc WILL get hot and smelly!!! ???

Mike
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HS93 (RIP)

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Re: Ok what am i doing wrong??
« Reply #4 on: June 16, 2007, 11:57:14 pm »

What is wrong with 24 volts??

Peter
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FullLeatherJacket

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Re: Ok what am i doing wrong??
« Reply #5 on: June 17, 2007, 08:48:49 am »

Peter
In theory the Electronize ESCs will take up to 24 volts, but a fully-charged 12v gel-cell will pump out nearly 14v, so two in series is ANADI 28 volts. Why would you want or need 28 volts in a tug boat? It's a bit too near the edge for comfort for me!
FLJ
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HS93 (RIP)

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Re: Ok what am i doing wrong??
« Reply #6 on: June 17, 2007, 09:04:04 am »

Yes I know but I was talking about just 24 volt, you could say the same for people with nicads, a 12v pack is much higher straight of charge , and this happens as you say for most batteries ,  electronize FR15HVR  seem to run without problem on two gel cells without any problems, most train people use them that way as well , and they draw a lot on start.

Peter
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John W E

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Re: Ok what am i doing wrong??
« Reply #7 on: June 17, 2007, 10:05:08 am »

Hi there Portside II

Just a quick question to satisfy my curiosity - Ive had a similar problem on one of my models, and, what I found was that the prop-shafts were tight.

Basically, what its got to do with is the principal of the speed controller switching the motor on and off rapidly.  If the motor has a lot of resistance against it, it takes more out of the speed controller to turn the motor over more slowly. 

This speed controller you have has a peak stall rating of 100 amps.  It is rated at 15 amps continuous running at 24 volt.   They quite happily run at 28 amp at 18 volt  ;D ;D

The thermal overload does kick in when you get to the 24 volts at 20 amp.  How do I know  ??? ??? ::) ;D

To get back to your problem, I would disconnect the speed controller and measure the amperage draw directly between the motor and the battery, and, that will give you a true measurement of amperage drawn under load, as long as the model is in the test tub.   I think you might find that these Johnson motors will pull a little more than you are saying under load.

aye
john e
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Shipmate60

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Re: Ok what am i doing wrong??
« Reply #8 on: June 17, 2007, 10:32:56 am »

Just a thought, are the motors rated for 24 volts continuous running?

Bob
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Peterm

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Re: Ok what am i doing wrong??
« Reply #9 on: June 17, 2007, 04:19:33 pm »

FLJ,(Dave)  you mentioned your book earlier.  As one of you fans, any more details?   Pete M
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FullLeatherJacket

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Re: Ok what am i doing wrong??
« Reply #10 on: June 17, 2007, 05:09:01 pm »

Pete

Hardly a book! Just a thing I wrote for Model Boats a while ago which Martin has included on the main Mayhem website. Link is
http://www.modelboatmayhem.co.uk/Common/Electrics/Twin_motors.htm. Several modellers have found it very useful, so that's as I intended.

There is a book, published by Traplet and written by Hugh Bright (sadly no longer with us) on the electronics of model boats. I forget the proper title but my late friend and mentor Craig Talbot had a lot of input into it; what those two didn't know about the subject isn't worth spit. If you Google Traplet you'll find it. It isn't terribly technical and it should be compulsory reading for everyone who makes RC model boats.

FLJ
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portside II

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Re: Ok what am i doing wrong??
« Reply #11 on: June 17, 2007, 05:19:57 pm »

right firstly i am running 2 12v bats in parelel to produce 12v and 14amp's and if i run it on the same set up with 6v i dont get the problems .
will post more soon  as i do more checks .
daz
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anmo

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Re: Ok what am i doing wrong??
« Reply #12 on: June 17, 2007, 05:23:12 pm »

Pete


There is a book, published by Traplet and written by Hugh Bright (sadly no longer with us) on the electronics of model boats. I forget the proper title but my late friend and mentor Craig Talbot had a lot of input into it; what those two didn't know about the subject isn't worth spit. If you Google Traplet you'll find it. It isn't terribly technical and it should be compulsory reading for everyone who makes RC model boats.

FLJ

A useful work, highly recommended. It was getting a little out of date, so was given a fairly comprehensive update two or three years ago by James Ramsay, who was slightly miffed that by way of thanks, Traplet spelled his name wrongly on the title page, though as he told me, at least they got his name right on the cheque. James knows what he is talking about. We met a couple of years ago after he'd done a skilful rebuild on one of my old Skyleader radios, and he brought with him one of those little east European RTR plastic fireboats that Deans used to sell. That little boat had more working functions built into it than I've seen in ages.
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Doc

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Re: Ok what am i doing wrong??
« Reply #13 on: June 18, 2007, 09:49:13 am »

daz,
In those test, I think the one where you measure the current draw with the ESC removed, motors straight to the battery(s), will probably be the most 'telling'.  I wouldn't be surprised if the current draw is more than you'd think.  ...  maybe
 - 'Doc
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portside II

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Re: Ok what am i doing wrong??
« Reply #14 on: June 18, 2007, 05:09:00 pm »

oop's just back from the shed trying to se what the motors draw on 6v direct in the test tank ,meter on the deck and clips on the battery ,agh the back end of the tug dug in and pulled it under ,water flowing over the sides ,lifted the back and the meter went over the side and into the tank .
The last reading i saw before it was drowned was -0- which on the destructions means overload and it was set to 10a 20a max for 15 sec so you could be right there Doc and the motors may be thirstier than i thought and that was on 6v ,god knows what it would be like on 12v  ???
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Shipmate60

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Re: Ok what am i doing wrong??
« Reply #15 on: June 18, 2007, 07:52:46 pm »

Johnson motors are for sale on eBay, if your motors are the same as these they pull horrendous current.
Some Johnsons are good, the problem is identifying which ones they are.

Bob
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chingdevil

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Re: Ok what am i doing wrong??
« Reply #17 on: June 18, 2007, 09:00:42 pm »

Portside
I had a similar problem with my Johnson 540 I did not realise that it would pull 12.5 amps from a 6volt supply when the boat was in the water, I let the magic blue smoke out of my ampmeter to find that out ended up buying a bigger ESC.

Brian
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portside II

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Re: Ok what am i doing wrong??
« Reply #18 on: June 18, 2007, 10:34:45 pm »

That's the ones Shipmate60  :o well they look just like them with the rings around the can  :)
ooh so if they (thats if they are the same as yours chingdevil) pull 12.5 amps at 6v then in theory at 12v they should draw less than half that  ???
so i will throw caution to the wind / water and run them off an esc and a 12v battery each as i have another one spare and see what happens   ;D.
and if the dreaded blue smoke raises its ugly head then i will have to think about it again .
daz
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Shipmate60

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Re: Ok what am i doing wrong??
« Reply #19 on: June 18, 2007, 11:01:51 pm »

portside II,
Do NOT use these motors on 12 volts.
They don't pull half the current but go right off the scale.
On 6 volts they run at 9000 rpm, on 12 volts almost 20000.
These motors should only be used on 6 volts for scale boats.
Run on 12 volts with VERY HEAVY ESC's and wiring.
The ones I tested on 12 volts went off the 10 amp scale at very low load.
As you are running 2 on one ESC quite easy to get 20 amps on light load.

Bob
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portside II

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Re: Ok what am i doing wrong??
« Reply #20 on: June 18, 2007, 11:06:27 pm »

thanks bob that will save me the price of two esc's ,look like i will have to invest in a couple of dedicated motors,
 although i have a pair of speed 700 bb turbo's which i did intend to use but was not sure due to them being the turbo type .
what do you think ?.
daz
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Shipmate60

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Re: Ok what am i doing wrong??
« Reply #21 on: June 18, 2007, 11:35:17 pm »

What model is it and what size and make of props?

Bob
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portside II

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Re: Ok what am i doing wrong??
« Reply #22 on: June 18, 2007, 11:51:11 pm »

it;s a MMM nangee running a pair of 40mm (i think) 4 bladed brass props in stearable korts on bearing shafts
i say 40mm as i cant remember and the neibours would have a laugh watching me walk down to the shed in just a towell
daz
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Shipmate60

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Re: Ok what am i doing wrong??
« Reply #23 on: June 19, 2007, 12:01:53 am »

Daz,
Are they brass props?

Bob
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Shipmate60

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Re: Ok what am i doing wrong??
« Reply #24 on: June 19, 2007, 12:08:09 am »

MMM recommend the Type 6 car heater motor @ £13-50 each. They run on 12 volts.
The cost seems reasonable as a geared motor will be more expensive.

Bob
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