> Robin Wrote:
>
> I doubt if there is an absolute need for the
> vanes at the bottom of each rotating tube
> <SNIP>
Early versions didn't have vanes.
They had startup reliability problems.
The vanes fixed the startup issues.
The BEST solution for the bottom is
a radial that is a conical shape with
a very slight axial inflow.
I knew people would complain about
needing a lathe. I didn't want to
make an impeller that needed a 5
axis CNC machine to make :D
(The toy wheel was something to make
it easy for the average person to do)
> <SNIP>
> Likewise, I doubt that the three vertical
> strips you glued inside the tube would be
> necessary
> <SNIP>
Without the strips you do get banding.
I think it was Alien Relics here that tried
to make his tube with a spiral of holes
and found his banding was the exact distance
of the spirals.
RoelCNC made his tubes with a bottom bearing
and it does not have such banding. (even
without the dams/strips)
This indicates to me the out of round
condition is causing the issue.
> <SNIP>
> I didn't see any lower bearing. Do you
> have the end of the rotating tubes rubbing
> against the lower plastic framework?
No lower bearing. Thats why care is needed
in the building to keep it round.
> <SNIP>
> I think the problem of evenly distributing
> the etchant on the PCB might be solved to
> some degree by cycling the speed of
> rotation.
I have done this speed modulation and it did
even out the banding.
I have also used a gear head motor to slowy
cycle the PCB holder up and down.
Neither is now neccesary now I have the
banding issues sorted at the source.
> <SNIP>
> went to my
> brother's place for lunch. Lo and behold
> he had some of the same plastic containers
> in his pantry! The were made by Icon:
>
> http://www.iconplastics.com.au
>
> near Melbourne. He recalls he bought them
> at Bunnings.
Yes the one I used was "icon" brand from
bunnies (where lower prices where just at
the begining)