What diam. prop shaft for 12″ long?

[David Harrison-OttawaParticipant @davidharrison-ottawa]

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.

[David Harrison-OttawaParticipant @davidharrison-ottawa]

[Dave MilbournParticipant @davemilbourn48782]

I would suggest a 4mm dia shaft with M4 thread for the prop. At this length you should be OK without centre bushes to prevent whipping. You might have a bit of difficulty obtaining ball-raced shafts this size but plain bearings are OK. Two useful UK manufacturers who will export are Steve Tranter **LINK** and Mark Windless **LINK** . I've used both and can recommend them.

Dave M

[David Harrison-OttawaParticipant @davidharrison-ottawa]

Dave, thanks. I can actually get 4mm bore miniature ball races from a company in Ontario if I decide to build my own.

There are also the excellent ready made Raboesch 4mm ball raced prop shafts that can be bought from either Cornwall Model Boats or a Canadian supplier can get them in, but they are pricey, about £30 or CAD$50 each.

[ashley needhamParticipant @ashleyneedham69188]

I will say it, and I dare say the camp on this one is divided, not that one will post, (just dont ask about lubricating the bloomin` thing) that I personally would use a 5mm shaft for this length.

ONLY on the basis that a 4mm shaft should, as DM says, be ok to use , BUT if there was any imbalance then really replacing it would be the only option and this entails a lot of remedial work.

There is no right or wrong on this. A decent quality 4mm shaft should be fine.

This is just my opinion.

Ashley

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