Dick,

Since you indicated you did not wish to use a venturi, one alternative
that had been used in the 20-30s for sufficient vacuum/flowrate to reliably
operate a Turn and Bank is to tap off your motor's intake spider downstream
of the carb (on a Continental, you could use one of the pre-threaded primer
fitting holes). What you do is start with a fitting a small hole (~#40 or
so) and, by a series of iterative enlargements, adjust until the level of
desired vacuum was reached at cruise power. This is similar to the standby
vacuum systems now sold for modern aircraft but, as the old vacuum T&Bs
needed less vacuum levels/airflow, one would normally have sufficient vacuum
throughout most flight regimes.

Just a thought.

Mike Bednarek


"Dick" wrote in message
m...
Staring at my empty instrument panel while considering which instruments
and
their placement, I got wondering how old time Mail pilots flew if caught
in
IFR conditions.

On my project plane, I'm considering just a airspeed/altitude/ ball & tube
slip (no needle) indicator/compass setup in order to avoid the venturi or
vacuum pump setup. Since I consider "electric" too expensive and wondered
whether a dome style compass might be the key??

Any thoughts would be appreciated.

Thanks, Dick -Lakeland, Florida