RC Tanks Australia Forum

Spuddie. I'm sure that you have already figured this out but for servo recoil you will need to convert the radial servo movement into linear movement. My better designs have involved a pair or parallel guides with a sliding bar between them. Like the slide on a trombone. Hard to align the bars with the gun axis in a scratch build- but with a CAD design you're set. The better the alignment - less friction - more efficient and better looking recoil.

I have a Stug gun setup awaiting your results - so make two - I can then make edits to the MAKO and all my other servo recoil programs for optimal performance with your setup.

Cheers
KG

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Well KG here's what I've designed so far.

This is the custom recoil unit frame, only elevation and recoil have been provided for thus far.....







And here is how it is as it would look installed (more or less as since the image was taken the recoil servo arm has now been swapped from a type 3 to a type 1).....





If I can remember how to do it, I will attempt to create a motion study animation of the assembly and then make a short clip of it all in action.

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SpuD

Here are some barrel states.....

Barrel zero state


Barrel recoiled


Barrel raised


Barrel level


Barrel lowered


The states as shown above are more or less at the full extent of the available travel, however adjustments to the lengths of the tie rods (shorter or longer) will make fine tuning of this travel possible.

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SpuD

Spud,
I am concerned with this setup. In particular the recoil servo. I fear that as shown it will impart too much force in the vertical plane on the barrel. I have shown these forces below.
RED - force action during recoil
Purple - force action during return
The green triangle will be where the barrel will pivot.

spudrecoilC.jpg

To minimise the vertical forces you need to have the servo linkage arm inline/parallel with the barrel at about the midpoint of travel. You could get away with this design using a longer servo arm AND moving the recoil servo back. I will send you one of these better servos - they do fit into the same holes as the blue ones. Somewhere on this forum I'm sure I have posting something on this.

Also I would plan the use of ball joint linkages - yes more expensive than bent wire BUT length adjustable and more importantly will allow for movement in all 3 planes. Only one of my recoil setups was in good enough alignment for a simple rod. All others needed ball joints. Ball joints for the elevation too.

The smallest joints and linkages come as parts for those mini copters (maybe 450 size I'll have to check)

AND.... sorry if this is too much, just offering the advice. No one usually ever takes it.... If they did no one would own a Clark board I would have the barrel screw into a block and have the servo linkages attach to said block. I have found it really important to be able to easily remove the barrel.

Just here to help cos again I need you to make me one/several of these.

Cheers
KG

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G'day KG

I will take all you have said on board and do a review of my current design. One thing that may not be clear in the images is they way the barrel is itself is restricted to only being able to slide backwards and forwards, there should be next to no rotational moment allowed, thus keeping the forces longitudinal. I had contemplated moving the recoil servo further back but was mindful of keeping the unit design as short as possible, so that the unit would be able to fit into smaller turrets with less space.

As for a slide based solution, this is something I have also been kicking around in my head, but I thought I'd attempt a KISS system approach just to see if a more basic design concept would work in CAD, which hopefully will also translate to actually working in the real world.

I also was planning to model in some ball jointed ties, but as I have none on hand to base any modelling on, I have at this stage just used wire ties to confirm component alignments and limits of movement.

Let me also say that any and all advice and even criticism in regards to the designs are welcome and don't hold back.

Anyway, in the meantime......

Onward and upwards, here is my initial model for a traversing pivot, at present I have chosen to place the servo tie rod lugs onto the fixed portion (green) of the traverse pivot assembly, however this will only be useful if the traverse servo itself is attached to the recoil/elevation unit.

Alternatively if the traverse servo is to be mounted fixed somewhere to the interior of glacis, then instead the servo tie rod lugs will need to be either on the lower portion of the traverse pivot assembly (red) or added to the recoil/elevation unit (white) itself.

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SpuD

Some more random detail grabs of the traverse pivot components.

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SpuD

KG

Well at your suggestion I have now re-designed the recoil unit to incorporate a track guide on the travel bench, and there is now a separate travel block that attaches to the barrel end.

The track bench was lengthened by a massive 5.7 mm to allow for a much better balanced recoil travel, which by the way is now almost 20mm (or about 313mm ~ 12 inches at 1:1 scale), up from the stock HL recoil of only 12mm (192mm ~ 7.5 inches at 1:1 scale). Now I have absolutely no idea what the actual recoil travel amount should be, but even the one that I can obtain with my current design configuration would seem to less that what I've observed on archival footage?

Now I did have some early screenshots of the re-design ready to post, however I decided to do a little more refinement and general tweaking and then sadly ran out of time to take any new ones, so you'll have to wait until AU-AM tomorrow to see my progress.

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SpuD

So you've now got 12" - go on braggard

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I always give my lengths in mm, makes it sound more impressive.

Anywho here are the promised pics:

At rest



Recoiled

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SpuD

Looks brilliant - Don't forget to add an end stop so that when screwing in the barrel you don't push the block off the guide rails

Cheers

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