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Author Topic: Graupner Löschkreuzer  (Read 4034 times)

Vts99

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Graupner Löschkreuzer
« on: August 14, 2016, 09:45:58 PM »

Got the Graupner loschkruezer weser fire boat .

She's around a metre in length but quite light . Currently got 3 x 600 motors in it onto 2 x 45 mm 3 blade props and 1 x 40mm 3 blade brass prop on centre shaft . Centre motor runs separate from outboard motors also

So question is . Is this the correct setup as seem to be drawing a lot of power through speed controllers and they seem to heat up a lot so wondering if there's maybe a different prop that would solve it and reduce power consumption
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andrewh

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Re: Prop advice
« Reply #1 on: August 15, 2016, 04:59:44 AM »

Hi Vts99


Good question!  Please tell us more, and maybe photos
600 motors - all we can know (or guess) is that they were made for Graupner and probably therefore have a metal endbell.  They could be wound for any voltage between 3V and about 15V and be happy at currents between 30A and 1/2 Amp.


What voltage /batteries are you using and is there more writing on the motors?


If I came to this all unknowing, as I do, I would start at approx 30mm props and see how hot the motor is after a canter.  Hand-hot is a maximum for long life  Blood temp is ideal. 


If possible put an ammeter in the circuits and see what the static current draw is (with the boat held)


When you say "drawing a lot of power" how are you judging that?  Is it the motors or Speed controls that are heating up?


So many questions!


regards
andrew







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Vts99

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Re: Prop advice
« Reply #2 on: August 15, 2016, 09:39:17 AM »

Sorry about that they are mtronics 600 motors running at 12v

Using 12v 7ah lead acid battery but also tried 12v 1600 mah nimh battery pack and same conclusion

The speed controllers are the little blue Chinese ones supposed to be 50 a fwd and 20 a rev but I'm dubious about these

It's the actual speed controllers that are heating up plus I'm only getting around 20 mins run time on the model which I'm guessing isn't right and unable to put another lead acid in due to weight so wondering if I can increase the performance any other way as if it isn't the props it can only be the esc

I've been advised by my dad I may be better with 2 blade props but not sure as he's been away from hobby for about 20 years like myself so wondering if I changed to a different prop would I still get the speed along with longer run times or am I going to have to change the esc

As for pics I can't get them off my phone onto forum due to size unfortunately
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Vts99

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Re: Prop advice
« Reply #3 on: August 15, 2016, 09:40:56 AM »

Another note was the heat shrink around my wiring has been heating up also so this is why I'm guessing high current drain
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morley bill 1

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Re: Prop advice
« Reply #4 on: August 15, 2016, 09:50:33 AM »

Hi got two of these ESC one works great the other caught fire 30 seconds after I put the boat in the water so I went back to electronize
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Netleyned

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Re: Prop advice
« Reply #5 on: August 15, 2016, 09:54:51 AM »

Our Chairman buys these for club members and I think the
smoke seals are faulty as I have seen a lot of smoke around
boats using them %% %% %% >>:-(


Ned
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malcolmfrary

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Re: Prop advice
« Reply #6 on: August 15, 2016, 10:06:09 AM »

Heating heatshrink just causes it to shrink until it has reached its limit.  If the wiring is heating up because of current or because something that it is near is heating it, it will just grip tighter if it can.


An often repeated rule of thumb for direct drive brushed motors is that the prop diameter should not exceed the motor can diameter, and should preferably have fewer blades than the motor has poles.  You dad's advice is as sound now as it was then, there has been no fundamental change in the laws of physics in the past 20 years, apart from the Chinese method of reckoning current.
Losing weight on batteries will improve run time and performance.  There is a big difference between the amount of energy stored in a 12V 7AH SLA and a 12V 1.2AH NiMH - a higher capacity NiMH would be the way to go.  Less weight to drag around, more capable of sustained current delivery, the usual result is a faster boat that runs longer.
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Vts99

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Re: Prop advice
« Reply #7 on: August 15, 2016, 10:08:52 AM »

Yup guys that's what I've heard also . May need to bite the bullet and replace both . And thanks I'll invest in 2 blade props also and larger packs to see what happens
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andrewh

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Re: Prop advice
« Reply #8 on: August 15, 2016, 10:11:01 AM »

Hi, Vts99

Good news!  Your props are Grossly overloading these motors

Someone else had a similar problem and I seem to remember that the 400 version was good for about 20 Watts

If you are draining a 7AH battery in 20 mins (1/3rd of an hour) then you are pulling on average 21Amps
and 21 amps at 12V is 252 watts or about 84 watts per motor (all this is an estimate)

Just looked at http://www.mtroniks.net/prod/Motors-For-RC-Boats/M600.htm#description
and they are rated at 40Watts and 3.4 amps at peak efficiency

They are also fitted with plastic ends, which limit their current handling

I suggest you ask them what props they suggest.  These are very gentle motors  - start with very small props and work upwards till you find YOUR balance of run-time, speed and motor warmth.

I would collect some cheap plastic props and try them - start maybe at 25mm and work up.

Let the motors really spin and they will not overheat! 

If the motors are happy, probably the ESCs will also be less distressed

Hope this helps,
Andrew



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Vts99

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Re: Prop advice
« Reply #9 on: August 15, 2016, 10:18:02 AM »

Thank u will check it out and try that
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grasshopper

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Re: Prop advice
« Reply #10 on: August 15, 2016, 05:18:20 PM »

I have a similar boat bought second hand a long time ago, the original builder had removed the centre shaft and motor and plugged the hole. I ran the Weser on a 6v 10A gel cell with two 540 type motors turning two contra rotating 35mm, 3 bladed brass propellers, each motor controlled by a seperate 'electronize' ESC, I used to get quite a long run time and nothing got overly warm.


That combination gave her an over scale speed with her stern squatting and her bows cutting the wake like a destroyer, plus with those brass prop's and seperate controls on the motors I could easily manage to get her to rotate on the spot, not something that's easy to do with some of those moulded plastic scale props from Graupner.



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Vts99

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Re: Prop advice
« Reply #11 on: August 15, 2016, 07:12:28 PM »

Thanks for that . I'm going to try the other stuff first but may reduce prop size also . She flies through pond on single prop but when I switch to the twins half the boats out the water which I quite like if I have to move in a hurry . Still thinking it's these dam speed controllers that are killing me so may just rip them out and replace then reduce props to 35s and see if it helps
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Tug-Kenny

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Re: Prop advice
« Reply #12 on: August 15, 2016, 08:43:36 PM »


It might be a good idea to reduce the props as you say.   That's an awful lot of wake for a model boat.   %)

ken
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Vts99

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Re: Prop advice
« Reply #13 on: August 15, 2016, 09:49:17 PM »

Yeah that's what I was thinking plus it nearly capsized a few smaller models on Sunday  :-X
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ChrisF

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Re: Prop advice
« Reply #14 on: August 16, 2016, 02:10:00 PM »

As a newbie just trying to add to my knowledge, why did the boat have different prop sizes given that all three motors are the same power?
Having read the rest of the posts I guess it's because you never run all three at the same time, either the outer two or the middle one?
If it was all three they wouldn't all be working equally hard would they?
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Vts99

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Re: Prop advice
« Reply #15 on: August 16, 2016, 03:39:12 PM »

Yeah u only run either single or double . Triple would only be if u wanted the majority of the model out the water .

The reason I have different props is this was all that was available to me at the time and thought it may be better to have brass than the plastic ones supplied with the kit but I'm guessing I may have to resort back to these for now to test theories

The real ship has one large prop on centre and two smaller ones on outboards but don't know why as always lead to believe that twin props aid it to go straight in both directions and single props have a tenancy to pull to one side due to rotation

But only going on advice from others as I've been away from hobby since I was 15 and I'm now 35
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ChrisF

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Re: Prop advice
« Reply #16 on: August 17, 2016, 12:33:29 AM »

Thanks for the information.

Chris
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Vts99

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Brushed to brushless info for beginner
« Reply #17 on: September 13, 2016, 05:58:22 PM »

Hi all

With being away from the hobby for too long I've never used brushless setups and looking for advice
I have the Graupner loschkruezer weser and currently it's running 3 x m600 motors along with 2 speed controllers and I'm having all sorts of trouble with not only sail times being around 15 mins per battery but also speed controllers overheating when running at full speed

So my question is . Would I be better converting to brushless to gain on run times and speed and if so how would I go about it

Thank you in advance
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Vts99

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Re: Brushed to brushless info for beginner
« Reply #18 on: September 16, 2016, 06:47:52 PM »

Any advice would be most helpful folks
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Charlie

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Re: Brushed to brushless info for beginner
« Reply #19 on: September 16, 2016, 07:19:21 PM »

You probably aren't getting a response since very similar questions have been asked and answered numerous times before. If you scroll down this board you will see what i mean. Have you read any of these threads yet?
Also, try reading this thread - lots of useful info here: http://www.modelboatmayhem.co.uk/forum/index.php/topic,13538.0.html

Vts99

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Re: Brushed to brushless info for beginner
« Reply #20 on: September 18, 2016, 01:47:29 PM »

I've looked at the entire board I was hoping someone would be able to give me advice on what this model would need as in best type and size of motor plus speed controllers and if it's possible to still run the three props as I haven't saw any info that helps with conversion of m600 motors to brushless and what the benefits are going to brushless as currently all I seem to be getting is short run times and over heating speed controllers
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chas

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Re: Brushed to brushless info for beginner
« Reply #21 on: September 18, 2016, 02:39:21 PM »

Hi vts99, to help people give you an answer, can you supply some extra information.
 What battery (s) are you using?
What size props are you using?
 How much current does your present set up draw on load?
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Martin [Admin]

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Re: Brushed to brushless info for beginner
« Reply #22 on: September 18, 2016, 04:32:31 PM »


.... and what battery are you using and how old?

(  Topics merged  )
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Vts99

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Re: Graupner Löschkreuzer
« Reply #23 on: September 23, 2016, 01:11:41 AM »

Thanks Martin

Currently running standard 12v 7ah battery which I can sail all day with on my canning tug but only 15 mins on weser
Also running 40 mm brass 3 blade props but not sure of the current draw as not exactly sure how to check this

The kit came with 2 blade 25 mm plastic props but didn't think it would make much difference going to 40s

Main thing is she runs great for such a short period but then that's it

I've had my heat shrinks heating up . Brushed esc heating up so much u can't touch them and battery dead within the 15 min runtime

So wondering if a conversion to brushless may keep the speed up but give me longer runtimes
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Stavros

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Re: Graupner Löschkreuzer
« Reply #24 on: September 23, 2016, 07:48:47 AM »

Here lies your problem......12v 7a battery........45mm props 40 mm prop

No wonder your battery died in 15 mins the current draw due to the size of probs must be horrendous.that explains why your heat sinks let alone the ESC's are to hot to touch... really shocked that they have not burnt out let alone damaged.
Remedy
Ditch the lead acid batt and buy some 12v 4300minh stick batts....far lighter than your lead acid which weighs around 5 to 6 lb

Ditch the props and go back to the originals as Graupner would have calculated the proper prop size for max efficiency !

Dave
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