Tuesday, 7 December 2021

RadioMaster AG01 CNC gimbal - is it worth it?

The AG01 is a new, high-quality CNC gimbal for the TX16S transmitter. As it happens, the TX16S is my go-to radio for F3F slope racing, so I was excited to try these new units!

In this review I check out a pair of AG01s, both on the bench and while flying. I also compare it with the original gimbals. And I'll be asking if it's worth the 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.

By contrast, the V1 Hall gimbals originally fitted are almost entirely plastic, and all adjustments must be made from the back of the unit, which means opening up the transmitter case.

There's also a plastic version of the AG01, as provided in the Eachine TX16S (identical to the RadioMaster TX16S save for the front moulding). However I have no experience of this unit.

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. 


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 front face of the AG01 is quite striking, with nicely machined accents. Notable are five holes for making various adjustments.

The main components - the baseplate and gimbal carriers - are made of aluminium. The baseplate has a black anodised finish.

Surprisingly, given that centring bars on the old gimbals are made of metal, those on the AG01 are made of a hard plastic. Most of the smaller parts, including the ball race retainers, are also plastic. 

Some users of the original gimbals reported finding cracks the ball-race retainers. This shouldn't be an issue with the AG01's, as the mouldings are of better quality.

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: 

  • Spring tension
  • Vertical end stops
  • Engage/disengage spring on throttle axis
Adjustments are made using the supplied Allen key. 


The friction and ratchet bands for the throttle are adjusted from the inside as normal.

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.


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


  1. 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. 

  1. Replace the back cover and side cheeks.
  2. Reconnect the battery
  3. 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 thin rubber band - this magnifies any stickiness very effectively. The results were as follows:

  • Gimbal 1: no detectable friction on both axes.
  • Gimbal 2: slight stickiness at one point in the x-axis. A little disappointing, fortunately it doesn't affect centring.
The old gimbals both had no detectable friction.

Stick feel

Stick feel is of course 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 subdued vibration. There's none of the irritating ‘ring’ that you get with some other sticks.
  • Hitting the extremes produces a solid '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 gimbal should provide a stable output, independent of temperature. To check for drift, 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. One up for the AG01!

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, 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. 

Upshot is that I like the AG01's a lot - they just feel more refined all round. 



Conclusion

The AG01's play very nicely with the TX16S. They’re silky smooth, centre precisely - and they look classy! 

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

I did encounter a couple of issues though: first, 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 useful, especially if your current gimbals suffer from excessive drift. Or if you just want to uprate 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.

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