Model Boat Mayhem

Technical, Techniques, Hints, and Tips => DC Motors (Brushed) and Speed Controllers => Topic started by: markrider on January 21, 2019, 05:15:53 pm

Title: best way to set props up for 3 prop boat
Post by: markrider on January 21, 2019, 05:15:53 pm

Hi all
So on a PT boat with 3 motors what's best set up for props
ie all the same rotation, 2 right 1 left , 2 left 1 right or something else ?
Thanks


Mark 

Title: Re: best way to set props up for 3 prop boat
Post by: TailUK on January 21, 2019, 06:25:53 pm

The only reference to Props I've seen relate to Elco 80ft boats.  They have 2 30inch props on the outside and a 28 inch prop in the center and they are all RH props (they turn clockwise as you look at them form the stern.)  Check out http://www.pt103.com/index.html and "Allied Coastal Forces of WW2 Vol 2 - Vospers and Elcos" by John Lambert and Al Ross.

Title: Re: best way to set props up for 3 prop boat
Post by: markrider on January 21, 2019, 07:10:53 pm

Seen lots about props on RC but can't seem to find anything now
Basically I have the Graupner Wiesel it's never been right turning or drive . Seems to twist to one side on fast runs .

Title: Re: best way to set props up for 3 prop boat
Post by: Ken G121 on January 21, 2019, 07:23:51 pm

The outside motors turn in opposite directions  the centre motor can be either but I believe clockwise is normal. The Robbe s100 kit came with 3 motors all set to rotate in the same direction. However set up like this it cornered very badly. Apparently does not to turn one way the other way it ticks into the turn tightly tending to lift one prop out of the water resulting in the turn suddenly straightening. So scary and unpredictable.
Cheers. Ken

Title: Re: best way to set props up for 3 prop boat
Post by: markrider on January 21, 2019, 07:40:48 pm

Great thanks Ken :-)

Title: Re: best way to set props up for 3 prop boat
Post by: malcolmfrary on January 22, 2019, 09:43:07 am

Since all three props on the real thing were driven by internal combustion engines that only turn one way, and the non-use of drive gearboxes at the time, all the props turned the same way.  The real things were noted for their poor turning ability at speed.  Thats WW2 launches, later boats and different types of vessel will be different.
On a model, things can be vastly improved by having the outboard props controlled differentially via a mixer, choose your favourite direction for the center prop.

Title: Re: best way to set props up for 3 prop boat
Post by: TailUK on January 22, 2019, 09:55:04 am

The majority of American Torpedo boats were powered by Packard 4M-2500 marine engines which had reverse gear and a double cone clutch.

Title: Re: best way to set props up for 3 prop boat
Post by: markrider on January 22, 2019, 10:07:36 am

Thanks all :-)

Title: Re: best way to set props up for 3 prop boat
Post by: malcolmfrary on January 22, 2019, 10:12:08 am

While they had a reverse gear, it was not intended for continuous use at full power, and for ease of maintainance and supply, it is logical that all 3 engines and drives would be the same.  The few pictures that I have seen showing the props look like they were all the same hand pitch. 
It is an area where the model can be an improvement, if only for the sake of being sure to get it back.

Title: Re: best way to set props up for 3 prop boat
Post by: Stan on January 29, 2019, 02:30:06 pm

Sadly the Graupner  Wiesel  should have 4 shafts not three. If you look under waships and military I did a build log on converting the Elco 596 kit to r/c operation. Have a look  at page one and find Elco 80ft plastic to r/c operation. I see no reason why the prop configuration cannot be changed on a model  mine has two props spinning on way and the other the other way sails a treat. No problems found with it pulling to one side.

Stan