CSM Micro Cased SL 420 Gyro Smart Lock System (Revision 4e)

The SL range of gyros is now on Revision 4 internal software. If you wish to have your gyro upgraded, the cost is £12 including postage. Send your gyro to PO Box 101, Glossop, SK13 5ZW, with a cheque or credit card details. If you are outside the UK, or need further details, please contact us at tech@csm-ltd.co.uk 

If you are using a small electric helicopter we do not recommend upgrading from Revision 3 at this point. From now on, two separate versions (currently 4 and 4e) will be available for nitro/petrol and electric helicopters.

SL420 manual (full size)
Micro SL420 manual
Technical support for current users

Compatibility

Model: The revision 4 SL420 gyro is designed to work best with glow and petrol (gas) models. For electric models, please see the SL420e. Belt driven models can suffer from static interference. Please use an anti-static spray on the belt to protect your gyro.

RC System:  The wiring is compatible with JR, Futaba, Hi-Tec, Graupner and the current style (blue plug) Sanwa/Airtronics transmitters. If you wish to use the SL420 with any other make of radio, please check with the service centre in your country, or email CSM's technical support on tech@csm-ltd.co.uk

The gyro requires an auxiliary channel with travel adjustments to control the gyro mode/gain. It cannot be used with basic RC systems that lack such a channel. We recommend that you use an RC system that also provides travel adjustment on the rudder channel. Most current production computer RC transmitters have these facilities.

Servo choice: The SL420 makes the most of either a digital or a conventional servo, since you can select Super Servo support during Quick Setup. Warning: Use of the Super Servo facility with servos not designed to accept the high frame rate will result in damage to the servo and may cause malfunction in flight. The Quick-setup routine runs the servo in standard mode so it is always possible to access this routine with a standard servo in order to turn off the Super Servo facility.

For optimum performance, we recommend a high speed Super Servo or Digital Servo (0.1 seconds/60 degrees or less), e.g. Airtronics 94757, JR 8700G and Futaba S9253. The gyro will run with any digital servo using standard (1520us) pulsewidths. These servos will be run at 250 frames per second.

With "Super Servo" support off, the SL560 will work with any servo in the Futaba, JR and Sanwa ranges but we recommend a speed of 0.12 sec/60 deg. or better for best performance. These servos will be run at 70 frames per second.

Batteries, power consumption and wiring: Due to the SL420's two stage power supply regulation, the SL420 will accept a supply voltage range: 4.1v to 7.2v. Please note that your RC system may be more restrictive.

Although the power consumption of the gyro unit itself is very modest, high performance gyros work the tail rotor servos harder and the power consumption may be high. We recommend that you use a good quality battery state monitor and check it carefully before each flight. You may wish to consider maintaining the charge in your receiver battery between flights by the use of a quality Delta Peak type field charger.

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Features

If you haven't used a CSM SmartLock gyro before, these are some of the features which might be new to you:

Quick Setup: Quick Setup is a simple routine which gets the gyro up and ready to fly. You enter it by toggling the gain switch back and forth whilst the model is on the ground. You then set the Gyro Sense, Digital or Conventional servo and Servo Travel Limits using your transmitter sticks. The gyro will also automatically pick up your stick centre and information about your radio gear.

Quick Trim: Quick Trim is a simple method of correcting for any small linkage errors. Toggle the gain switch five times whilst in flight, and the gyro will correct the trim. Please do not use stick trim when flying the SL420 gyro as it may cause the stick centre information to become inaccurate.

Dual Mode switching: Two modes are available: SmartLock and Standard. SmartLock is an enhanced version of heading lock, whilst standard has the characteristics of a conventional gyro, but with Yaw Rate Demand to allow for fast turns at high gyro gain levels.

The gyro gain channel is used to control these modes - the gain switch switches between the two modes, and the travel adjust (ATV) of the gain channel is used to adjust the gain in each mode.

Optional digital servo support: In Quick Setup, the gyro can be set to work with either digital or conventional servos.

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Additional information on Revision 4

The internal code of the SL420 gyro has been changed to take account of recent trends in model helicopter design and equipment. In particular we have addressed the effects of engine governors on the gyro situation as well as the increasing vibration levels that the use of ever bigger capacity motors is creating.

How governors affect the gyro
With the use of an engine governor, such as CSM's RevLock, the gyro has the luxury of operating with much more consistent tail power. Even quite small rpm changes give rise to significant changes in tail power, meaning that the gyro gain has to be turned down to prevent the tail wagging when the helicopter rotor over-speeds. This is often the situation which limits the gain. Removing overspeed situations by using a governor allows significantly higher gains to be run.

However, a governor also increases the demands on the gyro. A governor maintains constant head speed by changing the torque output of the engine. So a governor generally introduces bigger variations in main rotor torque than are seen in un-governed systems and it is, of course, the responsibility of the gyro/tail rotor system to compensate for these torque variations.

In Revision 4, CSM’s gyro software has been extensively re-written to meet the new challenge. Those familiar with our Revision 3 gyros will notice a significant increase in lock and better suppression of tail swing in high torque situations.

Vibration
In Revision 4 we have addressed the problem of increased vibration levels. In many gyro systems these cause low receiver battery duration and high wear rates on tail servo gearboxes. While our earlier gyros were class leaders in conserving power and tail servos, in Revision 4 we have increased the lock capability without dramatically increasing the demands on the servo.