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Brutus

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Bob Abell01/12/2013 19:45:20
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I`ve seen drives like this somewhere.....Was it Hobbies or Hobby`s?

Don`t think you`ll need the flexible drive coupling, old chap!

Bob

Paul T01/12/2013 19:50:01
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7151 forum posts
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Thanks Colin I will have a look

Bob I hadn't thought about Hobbies and will have a look, unfortunately it looks as though I will need the flex coupling as I am fighting for space in this one.

Paul

Dave Milbourn02/12/2013 10:52:33
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Paul
I can't find anything like this on the Hobbies website. MFA used to do a belt reduction drive for 540-sized motors but it's been discontinued for a while now. Graupner also do a geared one but again it's a reduction type. Like Colin says I reckon your best bet would be a belt drive with identical pulleys. MFA carry a large range of pulleys and belts.
DM

(Unless you actually do gear down the motor speed and use larger props.....)

Edited By Dave Milbourn on 02/12/2013 11:00:28

Paul T02/12/2013 16:24:59
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For those interested in why I need such an odd drive.

In designing the Brutus I have given myself a problem......I don't have sufficient space within the hull to get the twin 600s where I want to position them.

I do not like steeply angled propshafts so it is important that the shaft angle doesn't exceed 3deg

From a weight distribution point of view the first image shows the ideal location however the hull is simply to narrow at this point to accommodate the motors.

brutus 01.jpg

On a conventional hull the simple solution would be move the motors toward the stern to a location between F3 and F4 where the hull is wide enough to accommodate the motors.

The problem with the Brutus design is its bow shaped keel which, if the motors were moved backward they are also forced upward and so increases the shaft angle beyond 3deg.

A solution might be to turn the motors around so that the drive is pointing forward and position them over their respective shafts. The second image shows how this might be achieved, with the motors in this position the batteries would be placed in the adjacent bay.(F3/F4)

brutus 02.jpg

Paul

Dave Milbourn02/12/2013 16:55:26
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Paul

The shaft angle on some modern power boats is over ten degrees (to accommodate gearboxes) and there's no lack of power there. Just a thought.............

Dave M

Paul T02/12/2013 17:13:38
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Hi Dave

Its just me I don't like steep shafts

The steep shafts change the propellers angle of attack which equals less efficiency with the resulting increase in prop size to compensate. To me its a compromise that doesn't need to be made especially when, with a little thought, the shaft angle can be kept shallow.

Paul

ashley needham02/12/2013 17:21:49
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6612 forum posts
153 photos

Add to the futuristic design by having some alternative engineering.

Have one motor under and one over (at a steep diagonal, anyway) like the Lightning fighter. , the top motor can drive its shaft by a 1:1 belt, this motor could face rearwards while the othr one faces forrard.

In fact, be really bold and indeed have the motors one on top.. the bottom could drive the shaft direct, and the other shaft could run under the bottom motor and be driven by a 1:1 belt, the belt being behind the bottom motor.

These motors could be mounted on a vertical bracket. I dont know how long the shafts are but this might give a very small outwards angle to the shafts rather than being parralell, but it would be only a very small angle.

???

Ashley

Bob Abell02/12/2013 18:04:07
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Paul

The propshafts on my Slo Mo Shun we're flexible

They were bent upwards and the props were perfectly horizontal

Can't believe they were all that efficient though

Bob

Paul T02/12/2013 18:18:49
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Ashley

Amazing proposition and if I were building a long thin racer then stacking the motors would make sense but with Brutus there is no need.

Bob

The only time that I have used flexishafts is in conjunction with IC engines and always thought that they robbed power from electric motors through friction

Paul

Edited By Paul T on 02/12/2013 18:27:27

Andy Stoneman02/12/2013 19:39:28
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Paul, I can see where your coming from regarding propshaft angle, If it is too steep when driving it will force the boats bow down and you wouldnt want that.

Andy

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