Help building a rotating rod...thing!

[somersetpaul1969]

Morning all, I have been challenged to build something "arty", I'll do my best to describe it and what help I need (all measurements are approximates).

Imagine a 4ft high concrete pillar.
At the top there is a 3 inch hole in the centre, about 3 inches deep.
In that hole is a freely rotating metal disc with 3 x 1cm holes in the top.
Coming out of each of those holes is a 1cm metal rod, about 24 inches long.
The bottom half of the rod is fixed in to the disc, which rotates in the concrete hole.
Half way along the rod is a joint with the top half of the rod rotating around some bearings.

The idea is that the three fixed rods rotate around the hole in the concrete pillar and the top half of the rods rotates around the bottom half.

(have I described this OK?)

I think I can do the bottom bit, the metal disc which rotates in the top of the pillar with 3 rods protruding out of it.

So, my question is, how do I make a 2ft long 1cm metal rod which spins for the top half only?

Oh, and as it's arty it's got to look reasonably good....

 

[EddieM]

Ball and socket joint maybe?

 

[Tigercubrider]

A sketch would help!

 

[mattylad]

Have the bottom part of the rod hollow (a tube), this would enable a thinner rod (which is connected to whatever makes it spin) to then connect to the top spinning part of the 1cm rod.

I have no idea nor can picture this thing - but it's arty so that's not so unusual for me

 

[somersetpaul1969]

I am trying to replicate the turning mechanism of this....

http://www.stuartstockwell.co.uk/silver six oak.htm

 

[bernardgreen]

It appears to be a wind driven mechanism, with the three shafts fitted with pinion gears to drive them around a fixed central gear wheel as they rotate

Something similar to this but with ball bearings ( two per rod ) keep the three rods in place and able to rotate
.

and maybe constructed like this

Designing the leaves to be effective "sails" to rotate in the wind could be a difficult task. Google savonius rotor and then adapt the half can shapes to leafy shapes

 

[somersetpaul1969]

I don't think there are gears, it's not intended to generate anything, just turn in the wind....

 

[bernardgreen]

The gears only keep the rods in synchronised motion ensuring that leaves on one side of the pillar are facing and therefore catch the wind and those on the other side are edge on to the wind.

 

[somersetpaul1969]

This is the joint I am vexed with..

 

[mattylad]

The left side is a fixed tube, the right side is thinner when in the tube with a bit the same diameter as the tube, the bit inside may be a flexible shaft.

 

[bernardgreen]

When I proposed the gears to synchronise the three sets of leaves I had assumed the leaves of one rod could clash with leaves on a different rod if there was no means to prevent them clashing.

Looking at the video is is clear that each rod in the example has it's own "airspace" for it's leaves and that these airspaces do not over lap each other.