[hpv-boats] Right Angle Gearbox

[Ken Pate]

Thanks for the links Rick.  The flex shaft is fascinating.  Not sure were
I'd find some spring steel shaft, but I'll look around.   

In the mean while I did figure out how else I could do this, and that is to
put the angle gearbox after, below, or on the swivel that the top end of the
drive shaft mounted to.  But this would point the propeller at a little bit
of a downward angle.  Not sure what that would do to the efficiency of the
prop.

Ken

-----Original Message-----
From: hpv-boats-bounces at bikelist.org [mailto:hpv-boats-bounces at bikelist.org]
On Behalf Of Rick Willoughby
Sent: Sunday, June 07, 2009 3:56 PM
To: HPV Boat
Subject: Re: [hpv-boats] Right Angle Gearbox

Ken
I expect the 0.5" shaft is the best.  You can use it with a 4:1  
ratio, which is reasonably easy to achieve with standard bike bits.

If you go on Ebay you can sometimes find low cost boxes that are  
quite good.  The Mitrpak is hard to beat though.

The universal joint will give you a jerky sensation on the pedals.   
One that will handle the torque will be quite large and contribute  
noticeable drag.  I have used one at higher rpm and it was OK.

The best set up I have found is a side mounted curved shaft.  I  
prefer a 8mm (5/16") spring steel for the shaft.  I paint them to  
reduce corrosion.  The best set up I have used is shown here:
http://www.rickwill.bigpondhosting.com/V11J_Dec_2008.jpg
The latest arrangement has carbon fibre tubing for the frame.

You can see the curved shaft running down the side of the hull.  The  
shaft strut has 2 small stainless steel bearings purchased from  
"smallparts".  It is very smooth in operation.

The shaft can be pulled up while on the water for inspection for weed  
or running in shallow water because it is flexible.  The strut is set  
up to stop the prop from hitting the hull but it is pivoted at the  
top, allowing it to swing outward freely.

Finding spring steel in the form of straight round bar is not that  
easy but it is worth the effort.  It can be cut with a hacksaw but  
the blade will need to be replaced afterwards.  I use a grinder.  You  
can use 1/4" round bar but it will feel jerky at high power level.

This is a link to a photo of the Cadence type boat that Mike referred  
to:
http://snorlax.lampi.us/images/Deception%20Pass%202008/PICT2138.JPG

Rick



Thanks Michael,

Maybe I don't need such a large shaft.  I'm new to this which is why  
I bring
it up here.  Also, these boats won't be racers by any means.  Just  
pleasure
craft, though any efficiency is always desirable.

I will need to able to raise the prop maybe 15 degrees to be able to  
protect
it in shallow water. Will the Love-Joy couplings have that much flex?

I'm unsure what you mean by the Cadence.  Is this another gearbox from
Mitrpak or is it a boat.  I think what you are saying is that Mitrpak  
makes
a smaller gear box that is on the Cadence which is a boat, maybe your  
boat.
I see a smaller gearbox at Mitrpak with a 3/8ths shaft.  Is this what  
you
mean?  Also,  if the Cadence is a boat would you have a link to it?

Thanks for your time,
Ken


Rick Willoughby
rickwill at bigpond.net.au
03 9796 2415
0419 104 821


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