[hpv-boats] Magnetic Transmission

[v garza]

Thanks for the film clip, great concept. I use these guys who have a large 
selection of neodymium magnets to grade 52 http://www.kjmagnetics.com/  Some 
of their smaller magnets are very lightweight and low cost and so strong 
they can't be pulled apart. Plating may be a little thin for your type of 
project, though.

Vic
----- Original Message ----- 
From: "Rick Willoughby" <rickwill at bigpond.net.au>
To: "HPV Boat" <hpv-boats at bikelist.org>
Sent: Tuesday, January 18, 2011 1:08 AM
Subject: [hpv-boats] Magnetic Transmission


>I have been playing around with the idea of making a magnetic right  angle 
>drive unit for a while.  Over the past few months I invested in  some 
>magnets and built a prototype:
> http://www.youtube.com/watch?v=jCuCmzcjpao
>
> The video shows the torque test.  I have a 5kg weight suspended on a 
> lever arm connected to the output shaft.  The lever gets out to 230mm 
> before the magnets let go. This particular variant has a ratio of  1:3.3 
> and gives in at 11Nm on the output shaft.
>
> The torque at this ratio is ample for cruising to speed of up to  12.5kph 
> but would give out in a sprint.
>
> The unit was not executed to the initial design because I could not  get 
> the quantity of magnets of the particular size I wanted.  It was  intended 
> as a 1:5 step up but I could not get the alignment right  with only 4 
> magnets on the output so went up to 6 thus reducing the  ratio.  However I 
> got better than a commensurate increase in torque.
>
> This unit is extremely robust and heavier than I would want in a  boat. 
> One feature is that the weight is distributed at a large  radius so the 
> crank and output both have high rotational inertia -  flywheels if you 
> like.  This leads to smoother pedaling and can  compensate a little for a 
> torsionally compliant prop shaft.   Another  feature is the load limiting 
> on the prop shaft.
>
> If I made it to tighter tolerance I could get higher torque.  In a  way 
> this would defeat the original idea because I was exploring the  concept 
> for ease of building without need for precision machining.
>
> I expect with ideal magnet selection and simple method of  construction 
> this arrangement could be built for under AUD200.
>
> Rick Willoughby
>
>
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