CSM 720 Gyro

Written by Ashley Davis Wednesday, 02 September 2009 21:25

CSM 720

The following is a review of the CSM 720 gyro. This is CSM's top of the range gyro which features a silicon sensor and full programming interface for changing the internal parameters of the gyro. I have tested this gyro on the T-Rex 600 and also on the 450 SE V2. This gyro was also used to compete in the UK 3D championship and I picked it specifically for that competition as I needed a consistent pirouette rate for one of my set maneuvers (pirouetting wall of death).

Programming the CSM 720

The gyro is programmed using either a parallel port connector or a USB connector with a servo plug on one end. The servo plug fits into the PC connection port on the gyro. CSM provide a small CD with the gyro which includes the communications software for interfacing with the gyro. Opening the software gives you access to all of the gyros internal settings via some editable fields. See below for a picture of the software interface.

The programming interface is extremely comprehensive and this is one of the advantages of the CSM 720 gyro in that it is extremely configurable. However, you do need to understand exactly what you are doing and what each of the parameters will change. Fortunately CSM has a very good help line and are always willing to help educate on how to get the best out of their gyros. The only downside to this programming interface is that if you want to change some of the more complex parameters at the field then you will need to take a laptop with you in order to be able to access and change them. Fortunately the more basic parameters can be accessed through a function called quick setup. Quick setup allows you to do any of the following functions:

Reverse the gyro
turn on the vibration filter
set the travel endpoints for the servo
Set the servo center pulse to 760 microseconds
Gyro Mounting

CSM gyros are quite sensitive to how they are mounted but on electric heli's where vibration is less prevalent they are much easier to get right. I always use the metal mounting plate and mount the gyro to the plate using the very thin CSM gyro tape. The metal plate I then mount to the machine using standard servo tape or futaba style gyro pads. This seems to give a good solid mount with adequate vibration protection. Certainly on the 600 I don't need the vibration filter switched on. However, the 450 did require the vibration filter to get rid of some persistent wag. I believe this is due to slightly off center gears on the rear tail pulley which is right next to where the gyro is mounted.

Flight Review

450 SE V2

Initially I decided to try the CSM gyro with the very popular Futaba and 9650 tail servo. I chose the servo as it is very prolific and used to great effect with the Futaba GY401. My only reservation was that the servo is not very fast and I knew that CSM gyros work best when matched with a very fast servo. My reservations were proved correct in that during flight testing the stops from a pirouette were much less than adequate. Very often I would overshoot or get an overly soft stop. I decided to move to a better tail servo as the 9650 is now looking a little dated compared to more recent offerings. I purchased the Robbe FS 61 BB carbon speed digital on recommendation from our own Rob Turnbull. This was fitted with a relatively long servo arm with the ball three holes out from center. Once again we headed to the field for flight testing. With this new servo the flight characteristics were transformed. Hard stops from a pirouette were now crisp and predictable. I was able to turn up the heading hold significantly without inducing tail wag and the overall holding power of the tail was much improved. A pirouette rate proved to be very consistent with no whipping. In fact the performance from my tail system now superseded any previous set up I have ever used. It was exceeding previous tested gyros performance by a significant margin. Not only this but very little setup had been required in order to achieve this outstanding level of performance.

Following this testing I tried the Futaba 9257 and the performance is comparable to the Robbe FS-61BB. Having said that the 9257 is much more robust and has better torque, so this has stayed on the machine.

600e

On the 600e I am using a Futaba 9256 from the Futaba GY611. The gyro is running pretty much stock settings apart from increasing the piro start/stop rates slightly. Also with the 600 I had to offset the servo horn one spline in order to get even throws left to right on the end points of rudder movement. With this combination I'm able to run 115% gain before tail wag starts to occur. This gives a very solid feel to the tail, stops are extremely precise, the hold is very good, certainly beyond what I can get with the GY611. Lastly pirouette consistency is outstanding, this is true CSM territory, it's extremely difficult to beat this gyro on it's pirouette consistency. So for those learning piro moves this is a very worthwhile investment. It certainly contributed greatly to my own learning of the pirouetting wall of death.

Flybarless

The last element worth mentioning (as it is an additional function that the CSM720 can provide) is flybarless gyro stabilisation. Two CSM 720s combined with the CSM cyclock do a very good job of creating a flybarless helicopter. This is quite a complex undertaking in terms of how to setup and configure the gyros as well as the mechanical changes needed in the helicopter itself. I won't go into detail as I have a separate article coming soon on this very subject. However, video 1 above is utilising the CSM flybarless system as well as using the CSM 720 as a tail gyro. I have a flybarless 8S T-Rex using the CSM flbarless system, it works very well but Colin Mill of CSM does point out that the system is currently beta testing and more work is required for it to be come a fully operational system for the masses.

Pros

Compact unit
Comprehensive programming options
Great hold, crisp stops, supreme piro consistency
Can be used in conjuction with a cyclock for flybarless stabilisation

Cons

Requires good technical knowledge to set up
Requires laptop/pc to setup your heli.
Can be picky about how it is mounted on nitro machines

Conclusion

There are many rumors about the CSM 720 being inconsistent, over complex and difficult to set up. For the most part these are exaggerations of the truth. I've used a 720 for quite a few months now and day to day it is consistent in the performance it delivers. Gyro's are complex by default and CSM don't try to hide this from the user, you can configure pretty much everything to the n'th degree. On a 50 sized machine the default settings are extremely good, so in many respects it's as plug and play as a GY611 for this type of model. However, the CSM takes things a step further than the GY611 in delivering true world class performance. If you are prepared to spend a little time on setting up (a couple of hours) then it becomes a very worthwhile investment. That said I would in most cases recommend a GY611 over the CSM if the user is not going to be stretching the limits of their gyro (hovering / sports flying). The GY611 is still the easiest to setup and for me the CSM 720 is for the more advanced pilot looking at doing pirouetting moves, 3D flying and needing more from their gyro than the GY611 has to offer. For beginners/sports flying the GY611 is hard to beat, for more advanced flying the CSM 720 is king. I would temper this further though by introducing personal preference in how the gyro 'feels'. The 720 is all about consistency and this also comes across on the sticks, where as the GY611 can be a bit erratic if you start moving the sticks quickly. The GY611 will piro faster if you move the stick fast, the 720 just gives a given yaw rate based on the position of the stick. This all contributes to the overall 'feel' and in this regard for me the CSM 720 feels a lot more solid.

For 3D pilots looking to take their flying a step further - highly recommended.

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