RadioMaster AG01 CNC gimbal - is it worth it?

The AG01 is a new, high-quality CNC gimbal for the TX16S transmitter. My TX16S came with version 1 gimbals, so I was very interested to try the AG01. Would it be easier to adjust? Would it deal with the drift issue? Would it improve my flying?

In this review I check out the AG01 in detail, so you can decide it it's worth the premium price!

Full disclosure - RadioMaster provided me with these units free of charge to evaluate and keep. RM did not seek or receive access to this review prior to publication, and all opinions are my own. 

Headline specs compared

The AG01 gimbal features Hall sensors, 4 ball bearings, some CNC aluminium components. Unusually, some adjustments can be made from the front.

The version 1 gimbals originally fitted also have ball bearings and Hall sensors. However all components are plastic. All adjustments must be made from the back of the unit, which means opening up the transmitter case.

[Edit: Some versions of the TX16S and TX16S Mk II are offered with V4 gimbals. These are an all-plastic version of the AG01. They offer most of the benefits of the AG01 except for the CNC feel and premium appearance.]

Unboxing the AG01 gimbals

Inside the package were a couple of smart little boxes:

Each box contains: one AG01 gimbal, a couple of pots marked ‘Lubricating oil’ and ‘Damping oil’, a pair of (soft) springs, and an Allen key. [Note: recent gimbals may be supplied without the oil.]

The 'damping oil' is highly viscous, and is for use with the throttle friction strap. The 'lubricating oil' is less viscous, and is for maintenance of the moving parts. Both oils are a translucent white.

Also included is an instruction sheet for adjusting the gimbal.

Style and construction 

The styling of the AG01 is rather striking! At first I thought it was too brash, but I've grown to like it.

The aluminium baseplate has a black anodised finish with nicely machined accents. There are five holes for making various adjustments.

The gimbal carrier is machined from aluminium. 

Perhaps surprisingly, the centring bars are made of a hard plastic (rather than metal as on the version 1 gimbals). Most of the smaller parts are also plastic. 

Some users of the original gimbals reported finding cracks the ball-race retainers. This won't be an issue with the AG01's.

Together, the two AG01's contribute an extra 60 g to the weight of the TX16S.

Adjustability

Now for a cool innovation: some adjustments can be made from the front. These adjustments are: 

• Self centring spring tension
• Vertical end stops
• Engage/disengage spring on throttle axis

Adjustments are made using the supplied Allen key. 

The friction and ratchet for the throttle cannot be adjusted from the front - for these, you have to open the case.

Changing the springs

In addition to the standard springs already fitted,  a pair of weaker springs is supplied. These have 17 coils compared with 14 on the standard springs.

The springs are a very tight fit over the tensioning hooks, and removing them is not as easy as it should  be. Fortunately '3dxspin' on RCGroups has found a solution, which involves releasing the lower tensioning hooks. It involves a little dismantling - details in his post on RCG.

Personally. I found the standard springs fine.

Installing the gimbals in the transmitter

Installing the gimbals is not difficult, but does involve several steps. It's not explained in the instructions, so here's a quick rundown (skip this section if you want to continue with the review):

1. First, disconnect and remove the battery, then pull off the side cheeks
2. Next, remove the back of the case (undo four screws at the back, and two on the antenna plate). 
3. Disconnect the existing gimbals from the motherboard
4. Undo the four screws holding each gimbal to the front moulding, and remove the gimbals.
5. Lift off the metal faceplates from the inside. These are no longer needed.

6. Screw the new gimbals in place, taking care not to cross-thread the holes.
7. Finalise the tension of the ratchet and friction bands (they cannot be adjusted from the front). 

8. A little extra damping oil can now be added between the friction band and the moulding. Be careful, though, as only a tiny amount is needed. 

9. Replace the back cover and side cheeks.
10. Reconnect the battery
11. Finally, calibrate via the OpenTX 'System' menu.

Gimbal friction

Friction shouldn’t be a problem on modern gimbals, nevertheless it can creep in due to poor assembly or lubrication. 

To test for friction on the AG01s, I simply pulled the top of the stick with a very thin rubber band - this magnifies any stickiness very effectively. The results were as follows:

• Gimbal 1: no detectable friction on both axes.
• Gimbal 2: very slight stickiness at one point in the x-axis, not noticeable in use. It doesn't affect centring.

The old gimbals both had no detectable friction.

Stick feel

Stick feel is subjective, but I'll do my best to describe it:

• The stick centre position is nicely defined (though this will depend on spring tension).
• Moving the stick, then releasing it, generates a brief well damped vibration. There's none of the irritating ‘ring’ that you get with other CNC gimbals.
• Hitting the extremes produces a reassuring 'clack' – enough to announce that you’ve got CNC sticks, without being objectionable. 

All in all, I prefer the feel of the AG01's over the already good plastic units. They’re also nicer than the M9 gimbals on my FrSky X9D+.

Just one niggle: the ratchet on the throttle is rather weak - a trait shared with the old gimbals. At least the ratchet hasn't worn down like the old ones.

Accuracy/repeatability

A decent gimbal should not drift with temperature. 

To monitor centring accuracy, I use my ShowItAll widget. This displays the stick values (-100% to +100% in 1% increments) on the main screen - not a lab test, but sufficient to indicate any major issue.

The good news is that there has been no measurable drift with the AG01’s – the centring was precise and repeatable both indoors and in the cold. The same applies to the extremes of movement.

In contrast, my old gimbals drifted by  up to +/-1%, and some users have experienced more severe drift. 

In use

So far I’ve had three flying sessions with the AG01's, controlling my Pike Precision 2 slope racer in temperatures of around 9C - 11C. 

After adjusting the tension (easily done on the field!), I quickly settled down to the new sticks. The first impression was one of silence from the servos, which suggests that electronics are less noisy than with the plastic units. 

Edit: since writing the above, I've had a lot more stick time, and the result is that I really like the AG01's - they just feel more refined all round.

Conclusion

The AG01's play very nicely with the TX16S. They're smooth as silk, centre precisely - and they look gorgeous! 

Compared with the outgoing gimbals, the AG01's have better build quality, more precise centring, zero drift, and the convenience of external adjustments. 

Issues are minor: changing to the softer springs requires partial dismantling as described earlier. Secondly, the teeth on the throttle ratchet could be a bit deeper. Finally - and not so much a niggle as a wish - it would be nice to have external adjustments for the throttle straps.

At around £60 a pop, the AG01 isn't cheap, but it's not outrageous either. If you fly fast models, or models with large control surfaces, then the extra precision will be handy, especially if your current gimbals suffer from excessive drift. If you just want to upgrade your system, then you'll appreciate the feel and quality construction.

Either way, the AG01 is proving very popular, proving there's a healthy market for quality addons for the TX16S. For those who are wedded to OpenTX for competition flying, it's good to see a manufacturer catering for this end of the market.

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Postscript - LED bezel for the AG01

For bling lovers and night flying addicts, RadioMaster also offer an LED ring bezel kit with a choice of blue or white leds. I didn't install them but it should be easy - no soldering is involved. A potential downside is the need to reduce the vertical stick movement in order to clear the bezel.