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Author Topic: How to squeeze in motor and prop?  (Read 1776 times)

rmaddock

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How to squeeze in motor and prop?
« on: November 27, 2011, 03:30:32 pm »

Having found a minute of free time, my thoughts turned back to the Hearts of Oak and, more specifically, how to fit the auxiliary motor and prop into the available space.



This is the real boat.  The diesel engine is housed under the box in the middle of the cockpit and the prop shaft exits the hull to the right hand side as we're looking at it. I.e. it doesn't go through the keel.



The red card shows the position of the motor on the model.



And the red tube is the approximate size of the geared 500 I was thinking about using.  The problem is obvious, I think. I'm going to end up with a very short propshaft at a rather extreme angle.

So, how else could I do this?  Could I use a belt between the motor and the prop shaft so that the shaft itself could be lower in the hull?

How about some sort of flexible shaft? That'd let me put the motor somewhere further away....like the cabin, and run the drive shaft under the decking and out at a mroe reasonable angle.

Suggestions on metaphorical postcards please.  :-))
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Colin Bishop

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Re: How to squeeze in motor and prop?
« Reply #1 on: November 27, 2011, 05:14:03 pm »

Belt drive looks the way to go. Quiet, tolerant of slight misalignment and provides the opportunity to gear down the prop. As you say, it should also allow you to lower the shaft as long as there is room for the pulley. You can mount the motor on the side of the hull either in front of or alongside the shaft, whichever is more convenient. The motor weight can be offset by ballast on the other side or by positioning of the battery and/or other equipment.

You can use ordinary plain belt drive or, if you wish, go up market and use the toothed belts from the likes of SHG Models.

Below is the setup in my Caldercraft Cumbrae which uses double pulleys and O rings.

Colin
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rmaddock

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Re: How to squeeze in motor and prop?
« Reply #2 on: November 27, 2011, 08:20:20 pm »

Hmm, yes. I suppose that if I used the belt arrangement as the gearing then I could use a smaller motor....without the gearbox.
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triumphjon

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Re: How to squeeze in motor and prop?
« Reply #3 on: November 27, 2011, 11:50:41 pm »

can you not sit the motor above the keel , inside the hull ? my current build ive used a slightly longer thn scale shaft and made it exit the hull slightly further forward to the rear of the keel and managed to keep the motor on the centre line of my hull , my two servos , a speed controller , receiver and 7.2 v battery pack are mounted on a plywood platform above the static waterline . i will try to get a photo of the layout in the morning ! jon
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Jimmy James

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Re: How to squeeze in motor and prop?
« Reply #4 on: November 28, 2011, 11:09:47 am »

I think the way to go  would be keep the motor on the centre line and a longish shaft  this using a belt drive would avoid the extream angle , keep the weight on the centre and you have the motor in the best position for servicing the belts
Jimmy
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triumphjon

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Re: How to squeeze in motor and prop?
« Reply #5 on: November 28, 2011, 08:04:37 pm »







just a couple of shots of my current build , which has a 540 motor mounted above the internal keel , jon
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rmaddock

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Re: How to squeeze in motor and prop?
« Reply #6 on: November 28, 2011, 08:10:41 pm »

Hmm. Possible I suppose.
My problem is that the boat has an open cockpit and I really want to keep it as scale as possible.  Perhaps I need to bite the bullet, make a hole for a propshaft in the hull and then experiment with a length of something?
That might be a good next step....get an idea of where things really go.
Cheers!
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