--- In Indoor_Construction_at_yahoogroups.com, "Slobodan Midic"
<slomi_at_E...> wrote:
Hi, Slobodan.
I have a real hard time with math beyond the basics of arithmetic. I
use a less scientific approach than yours, and have avoided adding
boron due to requirements of one flying site.
When trying to replace my first ROG, I knew the exact crushing point
of the motor tube - it started to collapse while attaching the motor
for the first official flight. I used that information to duplicate
the wound motor on a digital scale by lifting a mass. All I had to do
was push a motor tube into the scale, exceed the "relieved" mass the
wound motor yielded then test again after the hardware was added.
Since my new criteria were stronger and lighter M/s (of course), it
was more difficult and now I have about a dozen unfinished motor
sticks.
Bruce in Seattle
>
> > Make a small tube, glue edges together, push corcs from balsa
> in both end (glue ), and test both: bending deflection under weight
> (horizontally) or vertically push the tube on scale up to crash,
> or up to some preset force. Than you can calculate
> stiffness exactly, for thinnest sheet (if you know formulas).
>
> I don't test stiffness of thin C balsa sheets at all; I measure only
> specific
> weight, measure the thickness at more points, and regard the sheet
> structure (light across the sheet), and as last I slightly
> pressure the tube between thumb and forefinger to see if exsiste
> some pure points. If the tube is not "good" I make a new tube
> (but I have no very high criteriums, here the thin C sheets are
> pearl, and than come 2, three, or four boron fibers). With 4 boron
> fibers allmost all C sheets are good.
>
> SM
>
Received on Wed Jan 18 2006 - 20:08:49 CET
This archive was generated by Yannick on Sat Dec 14 2019 - 19:13:44 CET