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Author Topic: Prop and Motor  (Read 1397 times)

Nordsee

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Prop and Motor
« on: November 27, 2009, 02:19:38 PM »

I recently refurbished an old (20years) boat that I had built. It is ca 50 cms long, hard chine and fast! Originally powered with a cooking 540 (Weren't they all?) and either 6 or 8 1200 Nicads, she was really fast, turned beautifully and was a pleasure to drive. The propellor was a Graupner P35 and she would run flat out for about 5 to 6 minutes. No speed controller, simple on\off switch.Motor and batteries got warm but not hot.
  Well had a mad moment and stripped out the old motor and switch and installed a 23 turn ,540 size motor, 2,4 amp Nimhs and ESC.Kept the same prop.
Does it go? Well yes, but only for about 1 minute or so, then she slows drastically, remains drivable for a couple more minutes before having to be brought in. The motor gets very hot, the Batteries warm. So,  thinking about it I would say she is over propped, any ideas before I order extra props. No model shop, have to be postal and so increases both time and costs. Remember this is just a fun project, so not looking for the last fraction of a knot.Just want a reasonable running time with a good speed. (Aren't we all!!??)
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HS93 (RIP)

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Re: Prop and Motor
« Reply #1 on: November 27, 2009, 02:55:32 PM »


have a look on hear there is a chart for there 23 turn motor and prop sizes you should be able to get an idea what you want from it for your set up

http://www.electronize.co.uk/model_electronics_frames.htm

peter
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grasshopper

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Re: Prop and Motor
« Reply #2 on: November 27, 2009, 04:18:32 PM »

a standard 540 is usually a 3 pole 27 turn, so the change to a 23 turn is not that drastic and the P35 prop should be ok - how many cells are you running?

I used to run a 19 turn motor on 6 cells (7.2v) and they were only 1800 mAh, an x35 prop and used to get around 5 minutes of flat out running.
It makes me wonder if something else is tight, mis-aligned or duff (are the cells ok?)
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BJ

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Re: Prop and Motor
« Reply #3 on: November 29, 2009, 09:21:42 AM »

Just want a reasonable running time with a good speed. (Aren't we all!!??)

Motor & prop sizes choices are fairly reliable in the attached chart
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Nordsee

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Re: Prop and Motor
« Reply #4 on: November 29, 2009, 07:17:50 PM »

Thanks so much, will get in touch with Prop Shop and order, much appreciated thanks again..........
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