Stab Test

[Stephen White]

This is truly why we need to develop working stabilisation for Armortek tanks...



Now, does one sixth of a stein full behave in the same way as the real thing?

Cheers. S

[mark lawson]

Is it not possible to use the gyro stabiliser from an RC helicopter

[Dennis Jones]

Mark,

I think you will find Stephen has been down that road and many other roads as well and as I gather still no success, am I correct Stephen ?

Dennis.

[Stephen White]

Well, my post was only supposed to lighten an otherwise dull Monday morning but Mark's reply deserves a serious response.

Once you've sorted out the mechanics (gun balancing, free movement, servo or direct drive and damping etc), which is relatively simple, you get to the difficult bit. How do you tell the gun where to point and how much to move in relation to a movement in the hull? You'd think it was similar to the problem on an RC heli but in that case, you're stabilising the platform, not one part of it. So the tank stab issue is more complex.

I tried heli gyro controllers but discounted them.

A more relevant technology is emerging with FPV camera gimbals. There, you want the camera to remain stable, whatever the platform is doing, and in some cases, to direct it at a specific point in 3D space. That is similar to the tank problem, although the gimbal needs stab in three dimensions (pitch, roll and yaw) whereas with tanks, the roll axis can largely be discounted.

The gimbal controllers have one crucial difference compared with most RC stabs. They combine more than one type of sensor. The rate gyros on the RC stabs only sense a rate of change of velocity, they have no absolute reference in space (ie the ability to sense change in a vector). To do that, gimbal controllers combine rate gyros and accelerometers. The combination of rate gyros and accelerometers should in theory allow a stab system to reference a point in space, each sensor compensating for the shortcomings of the other. In practice, many gimbal controllers add a third sensor type, GPS (and are then misleadingly called 6 DOF or 6 axis sensors). That really cements the ability to geo-reference a point in 3D space.

So that's where I've got to. I've got a cheap camera gimbal controller to trial. It would be easy enough to install were the manual and software tuning programme not written in Chinglish. That's the next challenge but I'm putting it off until the weather improves.

One last thought. I'm in two minds whether our models would benefit from both stab in traverse and elevation. I started by being convinced that elevation is the most relevant. For the bigger guns, the 20 pdr and 105mm on Cent (and dare one hope for something with a 120mm in the future), elevation probably is needed but it won't really show up unless the model is run over rough terrain. Stab in traverse becomes highly visible as soon as you turn the vehicle. Of course, you can simulate that well enough by traversing the turret manually in opposition to the hull but a stab system would take the pain out of it. On the basis that if you can crack one axis, the other is easy, I'm looking at two axis stab. A final footnote: for stab in traverse, installing roller bearings on the turret race is essential.

I'd be very happy to share whatever insights I may get on the Knowledge Base in the hope our collective engineering wisdom can crack a difficult challenge.

Stephen

[simon_manning]

i like these posts but cant help thinking about that guy that could leap over an egg and crack the top open with his big toe, interviewed on nationwide 30 years ago, he felt a compulsion to do it and that was it, regards simon.

[mark lawson]

Thanks for in-depth response Stephen, my thoughts were you only wanted one axis of stab but as you say correct one and the other is that little bit easier, sorry but I don’t have the time to follow all the vehicle sections on the forum I tend to concentrate on what I’m interested in at the time, my thoughts are if you do crack this enigma then you will truly transform your project from dare I say a mere model to a work of art for this I wish you good fortunes in your quest.

Again thinking out aloud without giving it much thought but PFV cameras work from a head set in that the direction you turn or tilt your head the camera follows suit would it not be possible to mount a smaller version of the head set in the tank I may be talking like a partition as in utter nonsense but this is just an ill thought out idea.

[John Heath]

I'm wondering if the Tamiya Gun Barrel Stabilizer could be adapted.
https://www.tamiyausa.com/product/item. ... t-id=53762

John

[Fabrice Le Roux]

Stephen,
"zwei Worten: ein Bier!"
my only German joke, alas.

The nagging issue with Camera Stab kits is that they are designed for light loads, and the mass-effects of inertia and momentum present in a moving Armortek model may only allow an approximation of stabilization. However, that may be good enough to create the illusion.

Speiberg ( or Lucas?) once commented about film miniature FX work that ,"..perfection is the enemy of good enough".

One of the best illusions of gun stab I saw some years ago was done with deft control of a two channel traverse/elevation setup, guided by a mk1 eyeball and an appreciation of what the real thing looks like.

This definitely makes a nice change from bin latches

regards
Fabrice

[Derek Attree]

Hi Stephen
I think it would be easier to just drink the beer

Derek