Luc
The current proa drives are reasonably compact and the result of looking at a range of possibilities.
There was some initial thought given to a curved shaft but finding suitable shaft material in size able to swing a 540mm prop is not easy. A curved shaft might work out economic for a lighter boat.
Even sourcing high strength stainless steel in 8mm diameter has been a challenge. People have found sources in Europe and USA. I still make shafts out of spring steel and sheath with glass sleeve. I have had one shaft made from carbon fibre, wound to my specification, that worked well but it would be very expensive to scale up.
One of the issues with scaling hardened steel is that the tempering loses consistency as the diameter increases so material endurance limit reduces as the diameter goes up. If you have an application in mind I could look at the geometry for the required shaft size. Usually diameter for the torque is lees than imagined.
On the pedal boats we are running a safety factor of at least 2 on the material endurance limit to allow for less than ideal geometry. Shafts with this factor of safety are not failing - at least after 1000km or so.
Rick
On 06/07/2014, at 11:21 PM, "lucjdekeyser@telenet.be [harryproa]" <harryproa@yahoogroups.com.au> wrote:
Rick, I came across some older threads discussing the potential of your flexible shaft propeller setup beyond pedal powered boats. Are there some fundamental reasons why you have not chosen this approach for the Melbourne proa electric driving?
Thank you. Luc
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Posted by: Rick Willoughby <rickwill@bigpond.net.au>
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