At long last I have finally got my moco rig working, thanks to a busy weekend with Roos Mattaar. It's a 6 axis rig with a crane arm and a 1.5m track. Connecting everything up has been quite a challenge, and I probably will be modifying some of the gears to improve performance.

But the ArcMoco interface with Dragonframe is excellent. We managed to produce a couple of moves, which have exciting potential. These are just the rough videos made from the live view, not proper shots, and we just slung some scenery and props in there to point the camera at not to create a particular scene.

http://www.youtube.com/watch?v=EjBSb_7-uUo

http://www.youtube.com/watch?v=cNsCpiBA7ok

We had to forego the focus control, as the driver was playing up and I managed to fry one (don't buy the Chinese copies!), and the tilt also took a holiday. Severe backlash from the rotation, which will be addressed somehow. Any suggestions gratefully received.

The track operates with a ballscrew, a bit slow but very positive. Rotation is via 25:125 gears. Crane uses belt drive, which seems good once tensioned. Pan and tilt are 25:100 gears and focus uses a 40 tooth gear onto a flexible 0.8mod gear ring.

But the great news is, after all this time it works!

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Great results! That opens up a lot of potential ideas. 

Dennis

very exciting. Love those sets too. Lovely detail.

The moves look pretty good - especially that second one from lower down, with some bold fast bits that I would hesitate to do manually in case they didn't work and wrecked the shot.  It would be nice to see the rig itself in action!

I think I have sorted the backlash problem by fixing the motor more securely. Will get some photos of the rig to post, and some video of it working. Although the shot looks fast, it does move very slowly! I will do a thread on how I made it sometime as well.

The challenge for getting a nice smooth motion seems to be animating between keyframes. Haven't got my head round this yet. It's simple enough to program a straight move, but an arc needs intermediate keyframes, and these can introduce all sorts of changes. That's why one of the tests accelerates and accelerates rather alarmingly.

Here are some pics of the rig itself. A bit homemade, but it works.

Here's a little video of the rig in action. The first shot shows it resetting to first position, which is when it moves quite fast. The second shows it going through a test move, when it captures the live view image. 

The next task is to see whether the rig will line up multiple passes with each other.

https://www.youtube.com/watch?v=vAi-rFOQ_Y8

Really exciting weekend! :)
I compared the two runs we did from the first test, and the two runs from the second test of the same shot but with less keyframes. In both cases the second shot has a lower angle than the first. I reckon that's the tilt playing up. Would be interesting to see a line up of multiple passes once you get the driver replaced, and see if that fixes it!
Here's a still of the split screen comparison. Otherwise it seems pretty accurate!

The rig looks nicely made!  Good solid chunks of aluminium.  That's the part I understand, the simple mechanics (though my engineering might not be up to making such a neat job of it).  The electronics and programming parts of it, not so much.

Very nice set to look at while we watch the moves, too!

Yes, the tilt driver is definitely not up to the job. It was failing to complete the move on another test I did yesterday. New drivers arriving today I hope!

I also found a backlash issue on the crane function, but cured that easily by adjusting the weights so it is always loaded in one direction. It's when the arm changes direction that the 'slop' occurs. 

Nick, I am also no expert at electronics or programming. I just watched a few videos made by people who had done it before, and hooked it all up. The Arduino board is basically a mini computer on a single board, very simple and with no memory. You just have to work out which wires go where. The clever bit - the programming - has all been done by Dragonframe, and it's just a matter of opening the folders and uploading the 'sketch', which is the Arduino mini-program. 

What this means is that motion control is within the reach of anyone with reasonable practical skills. The whole thing cost me about £1000.

Well, I don't even know what a tilt driver is - probably not like a bus driver?  Or where to buy the bits, or what bits I'd need.   So it's probably not quite within my reach.  But it would be great to do multiple passes of complex moves complete with ease-ins and outs, so I didn't have to choose between a moving shot with everything on set, or a composite shot with no moves (other than a little post-production pan).  

Sorry for the jargon. A driver is a little circuit board that is wired in between the Arduino computer board and the stepper motor. It effectively ramps the signal from the Arduino up into a 24volt squirt of power that turns the motor. The Arduino cannot drive the motor directly. Stepper motors are used for this type of motion control because they turn in multiple steps, tiny fractions of a rotation, so they are perfect for our purposes.

I referred to it as the tilt driver because it is the driver controlling the tilt motor, as opposed to the focus driver.

I'll take some more photos and do a thread on the making. With your skills, Nick, I am sure you would have no difficulty making a moco rig. The hard bit is learning what is needed and which part goes where.

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