Technical, Techniques, Hints, and Tips > DC Motors (Brushed) and Speed Controllers

LH & RH Propellers

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silverfern:
Hi Guys,
I'm scratch building a scale model of a commercial type LCT (landing craft 45m scaled to 140cm) and it will have twin high torque low speed motors. I don't understand why there are a LH & RH drive propellers available.


On a twin drive is it normal to fit LH & RH drive propellers? What is the effect v's say twin drive RH propellers?


I would like to purchase the drive lines including the motors from the UK before I start the build in order to fit the prop shafts early into the build before  the hull covering begins.


As I'm in Brisbane, Aust I would like to have a clear understanding before committing to an order.


Thank you in advance.

Peter Fitness:
This has been discussed on numerous occasions here on the forum, and a quick search may provide you with some answers. It is usual for twin screw vessels to have their props rotating in opposite directions, although there is much debate as to whether they should rotate outwards or inwards, viewed from the stern. Type propeller rotation into the search box, and be prepared to be totally confused :}


Peter.

BarryM:

Propellers not only drive a vessel forwards or backwards but also create a side force. This is inherent in the design of all props and, although designers try to minimise the effect, it cannot be eliminated.  Thus, if props are like-handed, there will always be a need for opposite helm to counteract the side thrust. This adversely effects speed and fuel consumption.
Set-ups employing RH and LH props running on separate shafts at the same speed will cancel each other out as far as side thrust is concerned. Similarly, LH and RH props that are mounted on a single shaft in tandem formation.
Whether you have inward or outward turning props is another question and plenty of info can be found by searching on this forum.
Barry M

silverfern:
Thanks Barry, good info for me.
Bob

Allnightin:
Can you be more specific about the LCT you are building please?  I'm a bit confused about any LCT being described as Commercial as the business of landing large armoured fighting vehicles is usually reserved for the armed forces!

In fact some of the types of LCT used in WW2 were built as simply and cheaply as possible so would have had all propellers turning the same way rather than have had to allow for different gearboxes and props.

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