Date: Mon, 12 Mar 2001 19:21:53 -0500
From: Mark Drela <[EMAIL PROTECTED]>
>I presume you're calculating the required wire length and driving
>a stepper to change the length? Wouldn't it be simpler to maintain
>a constant tension in the wire? This could be done by terminating
>the wire on a drum driven directly by a DC motor. The motor would
>operate stalled most of the time, with it's stall torque (and hence
>wire tension) controlled by the applied voltage.
I would NOT get rid of the bow.
The problem with anchoring the wire ends to the x,y traverses
is that they must now withstand the very substantial
wire tension. And when the wire is "swept" when cutting
a tapered wing, a significant component of the wire tension
must then be overcome by the stepper motors. This tremendously
increases the demands on the rigidity of the traverse frames
and the motor power compared to the external-bow design.
The wire tension is huge compared to the other loads.
- Mark
I fully agree, of course, on the consideration about the increase on demand
of rigidity and motor power (Mark, as usual, is topmost clear !).
But, if you really want to keep on this road, if I understand well, you
could also consider to tension the wire by hanging one substantial weight (5
Kg = 10 lbs.?) per side using pulleys. In this way only the structure should
be reinforced and the "complication" would be limited.
Anyhow I would stick with the bow, and a light one.
Ciao from Italy.
Tullio.
Ing. Tullio BONFIGLIO
Ansaldo Energia
ICI/IMT/AUT - F12 / P5
Via N. Lorenzi, 8
16152 Genoa - ITALY
Ph. : 39 (0)10 655 3267
Fax : 39 (0)10 655 3250 / 3894
E-Mail : [EMAIL PROTECTED]
RCSE-List facilities provided by Model Airplane News. Send "subscribe" and
"unsubscribe" requests to [EMAIL PROTECTED]
