| Title: | Welcome To The Radio Control Conference |
| Notice: | dir's in 11, who's who in 4, sales in 6, auctions 19 |
| Moderator: | VMSSG::FRIEDRICHS |
| Created: | Tue Jan 13 1987 |
| Last Modified: | Thu Jun 05 1997 |
| Last Successful Update: | Fri Jun 06 1997 |
| Number of topics: | 1706 |
| Total number of notes: | 27193 |
Of late I have been flying a new helicopter. It started out life
as a stock GMP King Cobra. Modifications were;
Miniature Aircraft large black Tuff struts.
" Boom support
New 1/8" vertical stab. Kind of like the Xcell.
Rear mounted rudder servo. Mounts to boom adjacent to frames.
Xcell 60 tail blades
GMP Legend canopy
Xcell 60 flybar paddles
Xcell 60 flybar weights
In addition to these parts changes I altered how the bell-hiller
mixing arms are mounted and added delta-3 hinging to the blade holders.
The mixing arm mod is simple. First you sand down the stock 4mm
nut that holds the flybar to app. 1/2 it's original thickness. Next
to cut off the original mixing arm mounting lugs from the center
bar. From here you assemble the flybar per the instructions and
then add the plastic mixing arm mounts to the inner ends of the
flybar. The mixing arm is pinned to this mount per the instructions.
You connect the control rods per the instructions.
For the delta-3 angle you simply remove the spaces added behind
the ball link. This effectively moves the ball closer to the blade
pitch arm. For older cobras you will need to buy a smaller ball
link like the ones used on the inner ring of the swashplate.
Latter (after lunch) I'll write why I did the changes.
Tom
| T.R | Title | User | Personal Name | Date | Lines |
|---|---|---|---|---|---|
| 1131.1 | why I did it | SA1794::TENEROWICZT | Wed May 02 1990 08:51 | 19 | |
Ok the why's...
I changed the mounting of the bell-hiller mixing arm to improbe
the flybars' athority over the blades. By moving the mount out
to the inside end of the flybar I'm able to get 70% bell-hiller
mixing as apposed to the stock set up of 50%. This helps in a hover
during windy conditions because when the wind hits the blades and
tries to change their pitch hence moving the rotor disk the wind
needs to over power the flybar. The more athority the flybar has
the harder the wind has to work to move the blades.
I removed the spacers hence adding 8 degrees of delta 3 hinging
into the blade holders for the same reasons. This sets up an angle
between the blade holder and the flybar. This angle (if done correctly
or the corredt side of the head) makes it more difficult for the
blades to move the flybar.
Tom
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| 1131.2 | XCELL40 mainshaft in a XCELL60 - NOT a good idea! | BSS::WALKER | Ralph Walker CSCs dtn=592-5701 | Thu Sep 20 1990 10:20 | 31 |
While assembling my X-CELL 40 I noticed the mainshaft is hollow for 3/4 of
its length, therefore lighter, and is secured in the machine by a bolt at
the bottom vs. the collar arrangement. I got to thinking if it would work
well in my X-CELL 60s. I installed one and was very pleased with myself
that I shaved some weight from my machine (not that at my skill level it
makes any difference but you know...). While on vacation the other week
I started to rebuild my other 60 which lost the argument with mother earth.
I installed a 40 mainshaft and built new blades and so on to get it in
flying condition.
On initial runup I heard a unusual blade noise, I reduced throttle to idle
and looked the ship over and didn't see anything out of the ordinary. I
ran it up the second time and started to lift it into a hover when it self
destructed. I have seen many crashes but this was the first time I saw a
mainshaft in two pieces.
I attempting to determine the cause I found the 40 mainshaft is at least a
two piece unit, a hollow shaft and a solid shaft with one end machined to
fit into one end of the hollow shaft. I don't know how they are fastened
together but the failed shaft broke at the seem where the hollow shaft
butts against the shoulder of the solid shaft. I removed the 40 shaft
from the 60 that was flying for inspection and found the joint between the
shafts to be ok but noticed the autorotation hub bearings were gouging the
lower portion of the shaft this was also true for the failed shaft with
only a minute or so of run time.
I showed the failed shaft to a machinist and he felt it had a crack in the
solid portion at the joint from the manufacturing process. My conclusion
is the 40 shafts cannot handle the rotating mass of the 60 blades and would
not recommend using the 40 shaft in anything but the 30/40 machine.
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