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Motion Control Specialists
with special interest in R/C model helicopter control
PO Box 101, Glossop SK13 5ZW, England.
email: tech@csm-ltd.co.uk       Tel: +44 (0)1457 854680
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Technical info on RevLock Engine Governors

Compatibility          Features        FAQ          Gassers & electrics            Optimizing Revlock without PC        Using the PC interface

RevLock 10 manual        RevLock 10 'At a glance' setup card

RevLock 20 manual         RevLock 20 'At a glance' card        RL20 PC software     RL20 PC instructions: page 1 page 2

RevLock 30 manual         RevLock 30 'At a Glance' card       RevLock 30 software    RevLock 30 PC instructions and tuning guide

RevLock 40 manual         RevLock 40 'At a Glance' card       RevLock 40 software    RevLock 40 PC instructions and tuning guide
Compatibility and Installation

RevLocks work by sensing the motion of a magnet attached to the engine fan and comparing this with a digital reference or 'virtual engine' moving at the correct speed - giving the quickest response to any RPM error. The magnet is easily installed by gluing it into a hole drilled in the engine fan - many engine fans now come pre-drilled for this purpose. The magnet can be installed either way around, so there is no need to test for polarity. The RevLock Sensor is then mounted beside the engine on the brackets supplied.

Model: RevLock 10 is designed as a basic engine governor for use with nitro powered model helicopters. RevLocks 20, 30 and 40 have PC interfaceability for improved customer control: RevLock 20 has a limiter option, RevLock 30 has Collective management, and Revlock 40 G-sensitive Collective management. The improved control of RevLock 20 means it is usuable in a wider range of models, and can be used in gasser (petrol) models - in some very slow-turning petrol engines, it may be necessary to fit two magnets rather than one (see the manual for details). Alternatively you may prefer to use the Stator Gator version of Revlock 20 for gasser models.

Servo: RevLocks can be used with any servo with a speed of 0.19s per 60 degrees or faster (most standard servos) and can be set to work with either digital or conventional servos.

Radio: May be used with any current radio, 35MHz or 2.4GHz. An auxiliary channel is required if you wish to use 'remote' mode (adjusting RPM and responsivity from the transmitter). However without this it may still be used in manual mode.

RL20, RL30 & RL40 only: Computer interface: These RevLocks make use of a PC interface and software. This is only usable with PCs, not with Mac computers. There are both LPT and USB interfaces available. The LPT interface works with all CSM PC-interfaceable products ever produced, the USB interface only works with current products.

Please do not use any other magnet or sensor than the one supplied! Spares are available. (For Gasser engines, please buy the version for use with the Stator Gator sensor. Do not try to use the standard version with the Stator Gator sensor)
Revlock 10 and all supplied accessories
Key to components (RevLock 10)

1. RevLock Unit (size 25 x 35 x 7 mm, weight 7g)
2. RevLock Sensor
3. RevLock Magnet
4. 300mm (standard) leads to Rx
5. Sensor Mounting Brackets (30, 50 and 60-90 size included)
6. Sensor/Mounting Bracket adhesive heatshrink sleeving
7. Mounting Pads

Also includes a pot adjuster and full instructions.

Other RevLocks include further leads as required, RL40 includes accelerometer head.

All accessories are available as spares, including alternative lengths of lead, and a counterweight to the magnet for those wishing to fit one. See our Spares page for details

All RevLocks:

Linear Hall-Effect Sensor: Poweful sensor with automatic signal level and direction check for total accuracy. It works regardless of magnet polarity, so you can fit the magnet either way around. For gasser models: please buy the version for use with the Stator Gator sensor. This sensor is available from www.statorgator.com

Neodymium iron boron magnet: Ultra strong magnet for easy installation and clear signal

Fully adjustable in flight: Pre-set two 'Remote' RPM modes, then switch between them or adjust them in flight from your transmitter. Typically, you can adjust head speed to within +/- 5 RPM of the rotor head. PLUS you can adjust responsivity in flight from your transmitter.
Please note: RevLock can also be set in 'manual' mode if your transmitter will not suport Remote modes, but you will not be able to alter responsivity in this mode.

Accurate RPM display: The initial RPM can be set to multiples of 250 RPM, which will be displayed using LEDs (you can then 'fine tune' to within approx. 6 RPM) There is no need for a tacho. Please remember that engine RPM is not the same as head speed - you will need to know the gearing ratio to work out the head speed.

Safety features: Smooth engagement and speed ramping make the RevLock safe to turn on and adjust in flight, and the Internal Fail-Safe gives enhanced safety with PPM radios.

Servo selection: Choose digital or non-digital servo option.

De-bug engine-setting

RevLocks 20, 30 and 40:

Optional PC Interface: Use the interface to change the Integral Gain and Minimum Control Point. RevLock will work with the CSM LPT interface (as supplied with older CSM products, now available separately) or with the USB interface. See our Spares and Accessories page. The PC interface is necessary to access the features of the RL20 and RL30 but, to save CSM gyro users from paying for more interfaces than they need, the PC interface is not included.

RL20 only: Due to popular demand, the RL20 can function either as a governor (adjusting for both over- and under-revving) or as a limiter (setting a maximum RPM). Please note this feature is accessible only through the PC Interface. Although you can switch between pre-set modes in flight, you can only set a mode to Limiter mode by using the PC interface and software

RL30 & RL40: These have Collective management which prevents engine RPM being bogged down below the power band. See Using the PC interface for details.

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Frequently Asked Questions

I've been flying for years - what can a governor do for me?
The CSM RevLock (RL10) was used by Duncan Osbourn in his winning flights at the 3D Masters 2005. The governor makes handling more consistent and predictable, and overcomes the inevitable imperfections in pitch and throttle curves. It also gives you maximum power without over-revving.

I've only just got into helicopters - is this going to help me or is it just another thing to worry about?
The governor will make the handling more consistent and predictable, and you won't have to worry about over-revving. As you progress, you would normally need to adjust your throttle curves. With RevLock this is not necessary.

Why should I buy the RL20, RL30 or RL40?
RL20 is the same as the RL10 but with PC interfaceability to be able to adjust parameters to cope with the most awkward engine setups. It also allows the RevLock to be used in limiter mode if required. However, it can only be used to its full potential with a PC interface. If you already have a PC interface (provided with earlier products) then you will not need to buy anything else to make full use of your RL20. Alternatively, you can buy a PC interface (LPT or USB) separately. If you have a PC interface, or you are likely to be getting one in the future, then buy the RL20.
The RL30 has Collective management which helps keep the RPM within the engines power band on high collective manouvres. RL40 is like RL30, but has an accelerometer head which senses when the model is under low g situations where more pitch can be allowed.

How does it work?
A magnet is fitted to the fan, and a sensor is fitted in a stationary place nearby. The sensor can sense the magnet going around and thus see whether the engine is going at the right speed. If the speed begins to go too high or too low, the governor will open or close the throttle.

Is it complicated to set up?
No. If you are using a moderately tuned 30/50 engine and a muffler, the RevLock should be pretty much fit and forget. Once the magnet and sensor have been installed, simply choose the engine speed you want using the display on the RevLock itself. There is no need for a tacho, and it doesn't even matter which way around you fit the magnet.
If you are using a highly tuned engine and want to get every last drop of performance, then the RevLock will take longer to set up. Remember that the guys at CSM are here to help.

Does it set the head speed or the engine speed?
The display on the RevLock shows the speed of the engine. To work out the head speed, you will need to know the gear ratios:
Engine Speed divided by Gear Ratio equals Head Speed

Why is it different to a limiter?
A limiter 'caps' the speed at a certain maximum. This will stop the engine from over-revving, but does not make the best use of your engine power.
RevLocks are governors, meaning they lock the engine to a certain RPM, and prevent both over-revving and under-speeding. RL20 can be set up as either a governor or a limiter (using the PC interface). In the majority of cases we would recommend using it as a governor. We do not recommend trying to use a limiter as a governor by setting high throttle curves - this makes the limiter less accurate, and can be dangerous if the limiter fails.

But RevLock sounds complicated - surely the complex calculations must make it slow?
No. The RevLock does not have to calculate the speed of the engine. It digitally synthesises the correct speed, and then looks out for any difference between this model and the actual engine. On average, RevLock takes about two revolutions of the engine to notice and respond to a small error in engine speed. This is actually quicker than your transmitter can communicate with the throttle servo!

I fly FAI - will it make height control more difficult?
No. This problem has been found with some governors, when doing hovering pirouettes, but CSM have resolved this problem.

What if I want to change the speed in flight?
You can do this if you have enough spare transmitter channels. You can swap between two previously selected speeds and finely adjust the RPM in flight. You can also alter how responsive the governor is, or disengage it completely during flight. The governor engages smoothly so there are no violent changes of engine speed.

Can it be used with both Glow and Gasser engines?
RevLock 20 is available in two versions. The standard version comes with its own Hall Effect Sensor for use with glow engines. The gasser version comes without a sensor, and should be used with the Stator Gator sensor, supplied by www.thestatorgator.com  Please do not use the RevLock with any other sensor than the one it is intended for!

If you have any problems or questions please contact CSM on +44 (0) 1457 854680  or email tech@csm-ltd.co.uk

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RevLocks for Gassers and Electric Models

Gasser Engines:
Although RevLock can be used with petrol/gasser engines (the manual includes instructions on how to run RevLock at lower RPMs than standard), it can be difficult to find a place for the magnet and sensor so RevLock 20 is available in a version designed to work with the ‘Stator Gator’ sensor for gasser engines. The sensor is not supplied, and is available direct from www.thestatorgator.com (approx. 22)

Stator Gator RevLock 20 ...CSMGL20... RRP 39.95

Revlock 10 was available in a Stator gator version, but this has been discontinued.

Stator Gator Revlock 10 manual            'At a Glance' card
Stator Gator RevLock 20 manual           'At a Glance' card

Electric models:
Speed controllers have improved considerably since the first electric models were released, but many pilots still find they are not accurate enough for their needs. The problem is funding somewhere to put the magnet and sensor. Most of our experience is with the TRex range of models as these were the first to be popular, but the basic principles are the same for all brands.
Sensor bracket - the fitting on the TRexs are the same as the Synergy, but the angle of the sensor needs to be different, so we supply a pack containing a Synergy bracket, a wedge, and heatshrink to hold these together.

Synergy/TRex mounting bracket... CSMRL19.... RRP 2.50

The easiest place to put the magnet is to put six in the main gear: we supply a pack of six carriers and magnets for the TRex 600 and Trex 500 main gears. The RevLock should be set to 6 x the required head speed

Magnet carriers for TRex 600...CSMRL21...RRP 7.45
Magnet carriers for TRex 500....CSMRL23...RRP 7.45

Initially on electric models we found that there could be interference from the motor or speed controller, so designed a filter to go between the sensor and the RevLock unit. This has not proved to be a problem with more recent models/speed controllers, but we still produce it, just in case!

Filter for RevLock on Electric models...CSMRL22....RRP 5.95
Optimizing Revlock without a PC interface

 I am using RevLock RL10 in Manual mode so I don't have access to the Responsivity control. I find that the engine note warbles when I execute a violent manoeuvre. Your manual suggests lowering the Responsivity control to cure this but what can I do?
The throttle servo arm length and the responsivity of the governor are linked. Decreasing the servo arm length (and increasing the throttle ATVs to restore the correct throttle barrel movement) will act similarly to reducing the governor Responsivity. (Increasing the servo arm length acts to increase the responsivity). Remember that when you change the throttle ATVs you will need to tell RevLock about these changes by going through the Basic set-up procedure again. Note that when you do this RevLock's safety system will also zero all the Range values so you will need to restore these after the Basic set-up routine is completed.
Please note: With RL20, RL30 & RL40 you can adjust the responsivity for Manual mode using the PC interface.

I run a two-speed set-up and want to get the absolute maximum performance from the governor at both headspeeds. Since there is only one Responsivity control on the unit how can I optimise the response at both head speeds.
It is possible to change the balance of the responsivity between low and high head speeds by offsetting the throttle linkage to introduce some 'exponential' into the system. If, for example, you find that a lower RevLock responsivity setting is needed at low head speeds than at high then you should offset the throttle linkage so that the barrel moves more slowly near the throttle closed position than it does near the fully open position. From our experience It is unlikely that you will want to operate with the linkage significantly offset the other way (i.e. with rapid barrel movement near the idle position) 
servo arm offset    Suggested servo arm offset.

I want to have a convenient way of fine-tuning the RPM in flight. How can I do this?
If your transmitter has, say, a rotary control channel spare then you should mix this channel into the Governor's Remote channel. A 5% mix will give you a fine adjustment over the RPM with the full rotation of the control covering about 400 engine RPM (typically 50 rotor head RPM). A bigger mix percentage will cover a correspondingly wider RPM range. When setting this up check that the Mode LED on the governor stays on solidly over the full range of the rotary control. If at one end of the rotary control range the mode LED starts flashing then the governor will disengage at this point because the Remote channel signal has entered the dead-band between ModeA and ModeB. Unless you specifically want to use this as a way of disengaging the governor reduce the mix percentage until the Mode LED stays on solidly for the full adjustment range.

I have recently changed my throttle servo. Having adjusted the throttle ATVs to suit I went through the Basic set-up procedure. However I now find that the governor will not engage. What's wrong?
To ensure that the RPM range setting is not overlooked, and to avoid first time users accidentally running RevLock with an inappropriately high RPM range selected, RevLock always defaults the Range values to zero whenever the basic set-up procedure is entered. In the interests of safety we hope users will accept the inconvenience that having to restore RPM range values under these circumstances causes. Note that since RPM offset values are set either by the RevLock's ADJUST control (manual mode) or by the transmitter Remote channel ATV values these are not affected by going through the basic set-up procedure.

I notice that even when my helicopter is in a stationary hover the throttle servo arm is continually moving. What is wrong?
Probably nothing! The power output of a glow motor is subject to continuous slight fluctuations. RevLock is seeing the small changes in RPM that these cause and adjusting the throttle position to compensate. These servo movements generally increase as the mixture is richened so if you think the amount of servo movement is excessive you should try slightly leaning the mixture. Some people worry that this movement increases the throttle barrel wear however the wear of the throttle barrel is dominated by small vibration induced movements of the barrel. The servo movements will not significantly increase this.

When I fit the magnet to the fan should I also fit a counter weight?
Although we make and sell counter weights for RevLock we don't often use them in-house and here's why. The weight added to the fan by fitting the magnet is about 150mg. The imbalance this causes is typically less than 5% of the out-of-balance of the single cylinder engine it's attached to so its effect will be slight. In fact most engines are less than optimally balanced anyway. There is not enough room in the crankcase unless a high density tungsten balance weight is employed which is unusual. If you bolt the fan on so that with the piston at top dead centre the magnet is furthest from the cylinder head the magnet will slightly increase the counter weight effect and may even improve the overall balance. If it's not possible to bolt up the fan like this or the fan is already drilled for a counterweight then its probably right to fit one.

I have a glow powered heli and because of a previous governor installation the fan has two magnets already fitted. Can I leave these in place?
You will need to remove one of the magnets. RevLock will work with either the north or the south pole facing the sensor so it does not matter which magnet you remove. Stubborn magnets that have been glued in securely can usually be easily removed with the assistance of heat to soften the glue

I am changing my previous governor for a RevLock. Can I use the sensor from my previous governor with RevLock?
No. Because of the unique way RevLock's sensor is arranged RevLock will not accept the signal from other types of sensor.

My RevLock engages correctly in normal flight mode but I can not get it to fully engage in idle-up flight mode. I have set-up the rpm selection very carefully, but the throttle arm slowly goes to full power and stays at this position.
It is likely that your engine does not have enough power to reach the target speed and allow rev-lock to fully engage. This could be caused by the target speed being too high for the available engine power or the fuel mixture being too rich and causing a loss of power. Use the governor disable function to optimise the fuel mixture and if the problem persists, reduce the target speed to a level that the engine can sustain.

My RevLock engages OK, but will not disengage at the end of the flight.
RevLock disengages once the throttle is brought below a point 15% above the normal idle position as programmed into the unit at stage 1 of the basic set-up procedure. It is possible that you have used too low a throttle position during the RevLock basic set-up. You should establish where your normal idle position is and re-do the basic set-up routine making sure that the throttle is at this idle position for stage 1 of the basic set-up. (Remember that after the basic set-up you will need to restore the RPM Ranges to the desired values)

My RevLock works very well and the response from hover to full climb is excellent, but I can not eliminate an overspeed in long vertical descents.
This has two possible causes: -
1) Idle point is too high
RevLock uses the idle and full throttle position it has been given during basic set-up to determine the lowest usable throttle position for governor operation. A high tick-over position will mean a high minimum throttle point when governing. Check that you have not 'taught' RevLock an excessively high idle position as this will mean that RevLock may not be able to shut the throttle far enough to prevent overspeed in very low load situations. If needed re-do the Basic set-up with a revised (lower) idle position. (Remember that after the basic set-up you will need to restore the RPM Ranges to the desired values)
2) Mixture too lean
The very good throttle response indicates that the engine mixture is certainly not too rich and in fact it may be slightly too lean (not enough fuel). Refer to the engine manufacturers operating instructions and richen the slow running mixture slightly until a good compromise of response and reduced overspeed has been achieved. With some carburettors you may need a slight richening of both slow running and main mixture adjustments to obtain the desired results.

I would like to run a very low head speed for slow 3-D aerobatics, but the RevLock unit hunts in dives.
There is a natural limit to any engine governing systems ability to provide smooth operation at very low rotor speeds. The limit is normally dictated by the cleanliness of the engine response and the overall set-up of engine, exhaust, blades, model weight etc. Firstly adjust the servo as highlighted in the earlier diagram to obtain finer control at low throttle openings and then find the lowest rotor speed you can run without problems. From here, slowly fine tune the engine and RevLock responsivity until you can lower the rotor speed further. In some cases, careful adjustments may allow the desired results, whilst other cases may dictate a compromise.

I would like to upgrade from my standard non-digital throttle servo and money is no object. What is the best servo to buy?
RevLock senses changes in engine rpm so efficiently, that you are unlikely to see any distinct advantage from high speed / high frame-rate / high cost servos. The use of any good quality digital servo with an operating speed below 0.20 for 60 degrees will allow for a very well optimised arrangement.

I have heard that it is important that my throttle is as least as fast as the collective servo. Is this true?
While this is a good principle the choice of servos is complicated by the very different loads the two servos carry. In the case of the throttle servo it drives a very light load with little friction and therefore operates at very close to its quoted (no-load) speed. The collective servo however is perhaps the most heavily loaded servo in the helicopter and as such may be moving very much slower than its rated speed. Remember that a 0.1s/60 deg servo running at half its rated torque will actually only be moving at about 0.2s/60 deg. In short, a 0.2s/60 deg throttle servo may well match a 0.1s/60 deg collective servo for speed under actual operating conditions.

How is my use of RevLock influenced by the exhaust system on the engine?
Tuned exhaust systems can have a very marked influence on the power output and throttling characteristics of the engine. By tightly controlling the engine rpm RevLock can help you to exploit the performance of very peaky tuned pipes. However this requires that you know the optimum operating speed for the engine/pipe combination you have. We suggest that you set RevLock to maintain the rpm at or just above the maximum power rpm for the engine and pipe. Often the throttle response can be quite poor below the peak power rpm and it is not advisable to try to govern the engine in this region.
If a two-speed set-up is required we recommend the use of a muffler which will generally provide good throttle response over a wide range of speeds. Some pipes may allow adequate throttling at speeds far below the resonance but some experimentation may be required to find what speeds can be used.

What determines the optimum RevLock Responsivity setting for a given model?
There are many aspects that influence the optimum RevLock Responsivity setting for a model. The following factors tend to reduce the optimum responsivity setting: -
1) Increased engine power.
2) Lighter main blades.
3) Higher gear reduction ratio.
4) Lower drag blades.
5) Lower target rpm.
6) Longer throttle servo arm (with correspondingly reduced throttle channel ATVs)
7) Poor throttle response.
As you can see, many of these factors are positive or neutral attributes of the model and only one - poor throttle response - is a negative factor. So you should not take a low optimum responsivity setting as an indication of a problem with the model. Only where a low responsivity setting is accompanied by poor rpm control should you look for the cause of the poor throttle response.

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Using the PC interface

In most cases, where the helicopter is well set up, the responsivity is all that will need to be adjusted (to avoid hunting at light loads). This guide is to help you optimise the governor's perfomance using the PC interface. Internal (PC access only) parameters are Integral Gain and Minimum Control Point.

Flight test: Engage the governor at the desired head speed (if you have set multiple head speeds, make the test for each speed, and adjust the parameter only for the relevant mode). With RevLock 30, the collective management should be inhibited for these first tests by setting the collective pull-off limit to zero and with the collective pitch range set to that which you would us with a conventional governo. Fly a series of full collective climbs followed by sustained steep descents of about 4 to 5 seconds. Fly the tests at a constant distance from you if possible, so as to be able to judge engine speed by ear without Doppler effects.

Using the table: Where there are multiple problems (eg hunting and underspeed), rectify them in the order they appear in the table (hunting first). Also check the possible causes in the order shown in the table (eg idle mixture before Minimum Control Point)
Note: If you need to alter the maximum collective pitch, then you may also need to alter the negative collective pitch. Ideally you could do this by repeating the flight tests inverted, but alternatively make an equal change.
Engine huntsResponsivity too high OR
Integral Gain too high
If Responsivity above half, reduce.
Otherwise reduce IG by 10%
Engine overspeeds throughout
sustained descent
Idle mixture too lean
Minimum Control Point too high
Richen idle mixture.
Reduce MCP by 5%
Engine falters at start of climbIdle mixture too rich
Minimum Control Point too low
Lean idle mixture.
Increase MCP by 5%
Engine underspeeds throughout
sustained climb
Main needle mixture too rich
Max. collective pitch too high
Lean main needle.
Reduce max. coll. pitch by 0.5 deg
Engine OK in climb,
but climb rate poor
Max. collective pitch too lowIncrease collective pitch by 0.5 deg
Excessive rev up at top of climb,
or excessive dip at end of descent.
Responsivity too low OR
Integral Gain too low
Servo too slow
If responsivity below half then increase. Otherwise increase IG by 10%.
If servo slower than 0.15s/60 deg., replace with faster servo
For RevLock 30:  Additional flight tests to assess Collective Management (RevLock 40 does this for you!)

Having performed the above tests with the Collective pull-off range set to zero, the same pattern of test flights should be flown with the Collctive pull-off range set to 25% and the Collective range increased by about 15% from that used with a conventional governor.
Engine overspeeds throughout sustained climb
(Collective Management active)
Narrow engine power-bandIncrease collective pull-off range
increase collective pull-off gain
Engine speed OK in climb but climb rate poor
(Collective Management active)
Maximum Collective pitch too low
Making poor use of engine power-band
Increase Collective pitch by 0.5 deg
Reduce collective pull-off range and/or
reduce Collective pull-off gain
Advanced technical advice for RevLock 20,30 and 40

Download this advice as a pdf document

These instructions are intended primarily for those wishing to use RL20, 30 or 40 for a non-standard application (e.g. gas turbine powered helicopters) but may be of interest to the contest pilot who wishes to establish the optimum performance from 'first principles'.

To avoid repeating the work the procedures outlined here should only be undertaken once the engine has been fully run-in and the mixture etc. has been set to provide a clean throttle response with minimal achievable lag both for increasing and decreasing power.

Start with the default settings but with the Integral Gain reduced to zero.

1. Test fly in a series of sustained climbs and descents and find the highest responsivity at which the engine does not hunt. Pay special attention to the light load situation in the descents. Note that with no integral gain set there will be some speed variation with load.

2. Re-test using acceleration gains above and below the default value (say 150% and 70%). Select the acceleration gain that allows the highest hunt-free responsivity to be used. The degree of fine-tuning you apply to this stage is a matter of personal preference.

3. Now set the integral gain to 40% and re-test. To avoid hunting a very small reduction in the responsivity relative to the no integral term case may be needed. In exceptional circumstances a large loss of responsivity may occur at 40% Integral Gain in which case an even lower value may need to be adopted.

4. At this stage the minimum control point can be set. Try descending the model steeply for several seconds with the governor engaged (e.g. in idle up). Set the minimum control point to the highest value that does not cause the engine to over speed in the descents. Where a multi speed setup is being used do this test at the lowest required headspeed.

5. Now the correct level of integral gain can be established. Fly with successively higher integral gain values, say 50%, 75%, 100%, and 125%. If little or no reduction in responsivity is needed to prevent hunting try increasing the integral gain further. If however a large reduction in responsivity is needed the integral gain is now too high and should be reduced again. As with the acceleration gain setting the degree of fine tuning you apply to this adjustment is a matter of personal preference.

The following adjustments of acceleration limit and acceleration threshold have only very slight effects in normal operation and the default values can be used in the majority of cases. However the following procedures are given for completeness.

Acceleration Limit
To find the best acceleration limit try a climb-out with the collective pitch just a little too high for the engine to maintain speed. Listen to the recovery of the headspeed at the top of the climb and reduce the acceleration limit to quicken recovery to normal engine speed. Don't reduce the acceleration limit so far that it starts to introduce hunting in light load situations.

Acceleration threshold
This reduces small amplitude servo activity that occurs if the engine does not run very consistently causing the speed to fluctuate a small amount from stroke to stroke. These movements can usually be reduced to low levels by the correct choice of plug and fuel together with correct mixture settings. In situations where a tuned exhaust is being used it may be necessary to reduce the compression ratio by increasing the shimming under the cylinder head of the engine. However, where the amount of servo activity remains high regardless of engine tuning an increase in the acceleration deadband can be used at some cost to the tightness of the rpm control to reduce the wear on the servo.

The internal sub-responsivity values allow independent responsivity adjustment for each mode. In remote operation the sub-responsivities for Modes A and B act in conjunction with the master responsivity controlled by the 'Adjust' pot. The overall responsivity of Mode A, for example, depends both on the pot position and the internal Mode A sub-responsivity. If, for example you find that the engine tends, at a given 'adjust' position, to hunt in Mode A but not in Mode B then the internal responsivity of Mode A can be reduced to correct this until the onset of hunting occurs at the same adjust position for both modes. In general, where a tuned exhaust is employed, higher RPMs are more easily stabilised and can sustain higher responsivity than lower RPM settings.
Note that in manual operation The 'Adjust' pot is used for rpm setting so the internal Manual Mode responsivity value is the only way of adjusting the overall responsivity.

Full-Throttle throw limiter operation
By default the unit has this set to "all the time" and prevents the throttle servo being driven beyond the programmed full throttle point even when cyclic to throttle mixing is used on a transmitter that does not prevent overtravel of the throttle channel. Where specialist applications require it the "only while governor active" option turns off the limiter function when the governor is inactive.

Setting a mode to operate as an RPM limiter (RL20 only)
If you want RevLock to operate simply as an RPM limiter this is done by selecting the "RPM limiter only" option under the "RPM control action" heading for the mode or modes required.
Note that the integral term is not used for limiter operation. When using one of the modes for RPM limiter action you should adjust the proportional term gain to set the sharpness of the limiter action. Generally the proportional term gain will need to be increased from the default value for governor action. A proportional gain of 130 is a reasonable starting point and the responsivity should be adjusted so that under light load conditions (where the limiter will be active) the RPM are steady. An excess of responsivity will give rise to fairly rapid fluctuations in the engine RPM.

RevLocks 30 & 40 only:

Stick gain
This parameter sets the degree to which the governor makes use of the incoming throttle signal to assist in the control of the throttle. There are a two main considerations when setting this parameter:-
The higher the governor responsivity being used the lower the Stick gain should be set.
In the more violent 3D type of flying the incoming throttle signal is often not a good indicator of likely load and the governor becomes more accurate when lower Stick gain values are used.
Where you are using a crisp throttling engine (and consequently a high governor responsivity) and where you are doing hard 3D manoeuvres consider turning the Stick gain to zero.

RL30/40 Collective management
Collective management is a technique to allow a greater collective pitch range (or longer or broader chord blades) to be used without the pilot having to consciously limit the amount of collective used in order to prevent excessive loss of engine RPM in certain flight situations. With RL30 the Collective Management operates full time, while with RL40 the Collective Management is reduced at low g, and enhanced at high g. In the case of RL40 this simplifies the setup because it removes the compromise about the collective pitch range as the unit tailors the response to manage the flight situation.

The maximum collective pitch that can be sustained depends on the flight situation. In straight, fast forward flight for example higher collective pitch can be employed than in high g manoeuvres. Indeed maximum forward speed and maximum climb speeds are usually obtained by increasing the collective pitch to the point that the engine, even at full throttle is loaded to a point towards the bottom of its power band. Although this causes slightly less power to be produced the reduced blade speed causes less power to be expended overcoming the drag of the blades leaving a greater proportion to propel the helicopter forwards or upwards. The low g-loading on the blades in these situations mean that the loss of maximum lift capability is not significant. Neither is the slight reduction cyclic authority noticed. In aerobatic manoeuvres the maintenance of head speed is more important as reduced headspeed leads to a reduction in available thrust for high g as well as a reduction in the speed and crispness of the cyclic response. It is important to realise that the maximum thrust of the rotor falls off very rapidly with falling headspeed so higher g values are maintained by sacrificing small amounts of pitch in order to keep the speed up. It is this trade-off that RL30 manages for the pilot.

By relying on the inertia of the blades it is possible to make good momentary use of very high collective pitch angles. However, There is usually not enough power available to sustain these in high g situations beyond a fraction of a second without significant loss of headspeed.

RL30, when engaged, controls the throttle to ensure the engine RPM are maintained within a tight tolerance of the target RPM. However, once the throttle has been opened to the maximum no further power increase is possible and it is then only possible to manage the RPM by unloading the engine in a controlled manner to prevent the RPM dropping outside the power band of the engine. For each of its modes RL30 has 3 internal parameters which set how the unit acts on the collective during periods of reduced RPM. The following diagram shows how these parameters control the way RL30 reduces the maximum collective pitch when the RPM drop below the target value.

collective management graph

Collective pull-off gain
The higher the value of this gain the faster the maximum collective pitch will be reduced as the RPM falls and the faster the maximum collective pitch will be restored as the RPM recover towards the target value.

Collective pull-off limit
This sets the degree to which the collective pitch can be reduced. The default value of 25% means that if the maximum collective pitch is set to 12 degrees then RL30 will be allowed to reduce this by up to 25% or 3 degrees leaving at least 9 degrees of collective pitch even with large RPM loss. Note that during autorotations RevLock is disengaged and does not modify the collective pitch in any way.

Pull-off dead band
This parameter allows for a small RPM loss before any reduction of collective is applied. This allows for the brief use of the maximum collective pitch in manoeuvres such as tick-tocks where the inertia of the blades can be relied on to provide the extra energy needed during very short high g situations. The value displayed in the PC interface is the percentage of the target RPM by which the engine speed can fall before any collective reduction occurs.

Notes on adjusting the collective management parameters of RL30:
The default setup of the RL30 collective management system is applicable for the majority of models: we would recommend adjusting them only after significant flight testing has suggested an improvement is possible.

Climb speed and forward flight speed.
If the engine power output is high and the available collective pitch range is somewhat restricted so that it has not been possible to significantly increase the collective pitch when installing RL30 it may be that the collective management adversely affects these areas of performance. In these situations consider if it is possible to fit longer main blades without danger of a main-tail blade clash. Failing this a change of gear ratio to allow slightly higher headspeeds may also be of benefit. Failing all these options you may wish to modify the Collective management response of RL30 by reducing the collective pull-off range and/or reducing the collective pull-off gain.

Sustained high g manoeuvres
In sustained high g manoeuvres such as pie dishes RL30 should, where needed back off the collective in order to keep the engine speed in the power band. If the loss of head speed is too great in these situations then try slightly increasing the collective pull-off gain. If you find that there is something of a compromise between the ideal setup for climb and fast flight and high g situations consider the possibility of using RL30 in, say mode A for aerobatics and Mode B for fast forward flight and using different Collective management setups in each mode. This should not be needed so long as sufficient collective pitch range is available.

Transient high g manoeuvres.
In short-term high g situations such as tick tocks collective pitch reductions can usefully be delayed to allow extra thrust from the rotor disk to be used while absorbing inertia from the rotor disk. If you find that the headspeed is excessively low out of these 'punched' high g manoeuvres then try reducing the pull-off deadband. Generally, large models with heavy blades will accept larger value for the pull-off deadband than a small model with light blades.

RL40 only:

RL40 differs from RL30 in being g-sensitive. This allows the unit to distinguish between the high-g flight situations where loss of headspeed can critically reduce the available thrust from the main rotor (thus preventing high-g being sustained) and low-g situations - especially vertical climbs - where trading headspeed (and hence power expended on blade drag) for more pitch can improve climb speeds.

There are two internal parameters that control the way in which the g-sensitivity influences the collective management:-

Threshold Vertical g
This parameter sets the vertical g value below which the collective management remains inactive. The default value of 1g ensures that the helicopter performs vertical climbs and fast forward flight exploiting the full pitch range determined by the RC system setup.

Vertical g gain
This parameter determines how rapidly collective management is introduced as the vertical g experienced by the model increases. The default value of 100% causes the full collective management to be applied once the vertical g has reached 1g above the threshold (so by default full collective management is applied for more than 2g). Increasing the Vertical g gain brings the collective management in more rapidly as g increases while decreasing it brings the collective management in more slowly. So, for example, if the Vertical g gain is reduced to 50% full collective management is delayed until 2g above the threshold, 33% delays it until 3g above threshold, etc.

Adjusting the RL40 g parameters
The default values are applicable for a very wide range of models however if the model has a low power to weight ratio and a high disk loading (such as a heavy scale model) then reducing the threshold and increasing the gain will be appropriate. Conversely, very high power to weight models with low disk loadings may be able to use higher thresholds and/or lower gain values.

If you have any problems or questions, please contact CSM on +44(0)1457 854680 or email tech@csm-ltd.co.uk

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