RCSD-2012-11 - RC Soaring Digest

KST DS125MG servo
Bill & Bunny Kuhlman, bsquared@centurytel.net
The KST DS125MG is a thin, metal gear, digital servo. It is
designed and configured to be used to drive ailerons and flaps
on 2-servo, 4-servo or 6-servo wings.
During our evaluation, many comparisons were made with the
Hitec HS-5125MG, a similarly sized servo with which we are
extremely familiar, having used them extensively over the last
few years.
Our sample was provided by OleRC in Hong Kong
and arrived in the usual retail cardstock
box and was enclosed in a bubble packet. Included with the
servo were three plastic servo arms, a blue anodized aluminum
arm, three mounting screws and the servo arm set-screw as
shown in the title photo.
The body of the DS125MG is primarily machined aluminum.
There is a molded plastic portion which sits at the base of the
gear train. The case itself is very reminiscent of those produced
by Volz for model aircraft use - the flat sides of the motor are
flush with the case surface.
All of the gears in this servo are metal. There is no play in the
linkage and the sound in operation reflects the sturdiness with
which this servo is built. Operation is extremely smooth and the
measured travel with signals from 1.00μsec to 2.00μsec was
slightly more than 90 degrees.
In our testing, centering was consistently right on with no load,
and deviations of about 1/8th inch were measured with a load
of 48oz.in. (It should be noted that the nylon control arms
deflect substantially under this load as well.) With a 5-cell NiMH
pack, current draw is approximately 230mA with a load of
24oz.in, and 850mA with a load of 48oz.in. The maximum
measured current draw, 1.2A, occurred under full stall
conditions.
Because the DS125MG is slightly taller than the HiTEC
HS-5125MG and like servos, it may not be able to be used as
a direct replacement in most installations. For new installs,
wood frames need to be made slightly longer because of
the placement of the two “ear” holes. The KST DS125MG is
3gm/0.12oz heavier than the HS-5125 but is rated at about
50% more torque, so will be an advantageous choice in some
applications.
Sources:
OleRC:
KST:
60 R/C Soaring Digest