In a message dated 8/28/2006 1:15:18 P.M. Eastern Daylight Time,
echristley@nc.rr.com writes:
Finn
Lassen wrote:
> Only vaugely rotary related...
>
> I'm
driving myself nuts trying to build this thing level to within 1/8
> to
1/4" !
>
> I'm using a gardenhose, terminating in clear PVC tubing
at each end,
> to get reference points at the four
corners.
>
> The thing is that the level varies 1/2" or more over
hours.
The commercial versions that I have seen use all clear plastic tubing for
the full run, so you can be sure that there are no bubbles in the hose. If a
bubble sits in one place a while it tends not to move without more than nominal
pressure changes. It dries the wall of the hose and surface tension takes over.
If the tubing gets a slug of air between two low spots, that forms a "P" trap
like the one under the sink, and the water column will not move at all.
It is also good to keep the ends of the clear tubing mounted higher
than you highest construction and measure down from the fluid level. That keeps
much of the tubing running up hill and reduces bubble entrainment. Unless the
tubing runs are short as in the race car setup, they tend to be a pain to use.
Worse if left at ground level (pun).
Lynn E. Hanover