This is a short review of the CSM SL420 Micro Gyro.
The gyro is very compact and easily fits under the boom between the side frames of a T-Rex. As with all CSM gyros that I
have used this one has the standard CSM setup procedure. During power up of the gyro you switch between normal and heading
hold a couple of times and the gyro goes into it's auto setup sequence. The gyro signals this by moving the tail servo arm
back and forwards a couple of times. The gyro then takes you through a number of configuration settings. The first setting is
gyro sense, normal or reverse, this setting is to make sure the gyro is giving the correct commands to the servo to counteract
unwanted axial movement. The tail transmitter stick is pushed left or right to set normal or reversed gyro sense. Having set
this the gain switch is toggled and the gyro acknowledges by moving the servo arm backwards and forwards again. Next you
select whether the gyro uses digital servo support or not. Running digital mode on an ordinary servo can destroy it and I was
somewhat suprised to see that the gyro comes by default in digital servo mode. Therefore on initial power up I would recommend
not plugging in a servo and turning off the digital servo mode. Next is to set the maximum throws, the servo moves to maximum
left throw which you can then adjust with the tail stick to be either more or less, this is like setting end points for the
servo. Again toggling the gain accepts the setting and the opposite end point for the servo is set. Toggling the gain again
gets a conformation movement of the servo back and forwards and then all is done. The gyro must be powered off/on to take the
new settings.
The correct procedure for setting up this gyro in flight is as follows
:
1. switch to rate mode (not HH mode)
2. Hover heli and observer how much trim/stick is required to hold the
tail in place.
3. Adjust mechanical linkages until the model hovers with little or no
tail movement. Do not touch trims or try to trim the tail.
4. Switch to HH mode and you should have a solid tail, if not toggle the
gain switch in flight a few times with a second gap in between each 'toggle'.
This quick trims the HH mode to match rate mode.
5. Adjust the end points of the tail to get a reasoable pirouette rate.
So what sort of performance can you expect? Based on my flight testing
this gyro is absolutely superb. Tail hold is rock solid and short stabs
of tail command result in the tail moving in short movements with no tail
bounce or wagging. Gain in heading hold can be taken quite high before
any wagging is apparent, certainly a higher gain is achievable than with
a telebee type gyro. Yaw rate on the tail is controlled using the end points
for the tail channel. Having spent some time getting my mechanical setup
spot on I can now hover the T-Rex comfortably one handed without fear of
losing the tail. More flight testing is required (e.g fast backwards flight)
but on current performance this gyro works superbly in the T-Rex and makes
unpredictable / low gain / wagging tails a thing of the past.
