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[david.harrison]

Hi, I will be outfitting a 1/10 scale Amati Riva Aquarama with motors etc. for radio control and I need to decide what prop shaft diameter to use. The shaft will be 12" long approx., driven by a 540 size brushless motor - 1700kv on a 3S LiPo - 11.1V nominal. There will be two such motors. The props will be 3-blade 35mm diam. x 30mm pitch.

For a long prop shaft like this would 1/8" diam. be large enough or should I go for 4mm or 3/16". The stuffing box will be ball raced at the prop end and maybe also at the motor end, or else a bronze bushing at that end. I was wondering if shaft whipping would be an issue for a 1/8" shaft over a 12" length when driven at say 10,000rpm?

Any advice would be appreciated. Thanks.

[wee speug]

Whilst I am a relative newcomer to model boats,..i recently fitted a longer shaft..@ 14in,into my schnellboot  and i used a 4mm with the outer tube having a bearing at either end and one in the middle,...and it worked perfectly,...my motor revved up to 20,000 without any whipping of the shaft

[thething84]

by having a bearing in the centre of the prop length it supports the shaft theoretically halving the length of unsupported prop shaft.

[Tug-Kenny RIP]

If the bearing stays where it put.     


Ken

[derekwarner]

Guys.....many real ships have multiple shaft bearings.............between the engine & the propeller 

With life size vessels ....it is not the shaft speed that is of concern.........but the applied torque to be transmitted...........

So from this ....the suggestion fro tt84 is valid..........support the propeller shaft at logical positions.......... .....

One of the other points to keep in mind is to use amp meter to verify current draw with the newly built propeller shaft assembly.............Derek