@ Dave McLaughlin - If you’re still looking for a slew ring, McMaster has light duty plastic ring style turntables near the diameter range you mentioned for around $10. They even have 3D CAD models.
Thanks Gene, I ended up order 2 of the Lazy Susan bears as they fit nicely in the design I am working on. As they are aluminium I can easily thread the existing holes so I can mount onto my housing.
@ Dave McLaughlin - i hadn’t really heard of jibo before. On the face of it it sounds really naff, but the video’s of it moving do look pretty darn cool. I couldnt really get my head round the geometry of the two rotational axis before, but now i get it. If you can make it run anything like as smoothly as that then it will be really cool.
I’ve ordered the bearings first. It these are not sloppy then I will get the plastics 3D printed. Price is around US$650 so not too bad considering the volume of the material. I also have a second option about the same size from Trossen Robotics if these first ones are no good. It all ginges on the quality of the bearing.
I’ve gone with a 10 degree angle on both so a combined 20 degree should be enough for it to “look around”
The video’s of Jibo are mainly marketing so most of the stuff looks to be CGI. The limited video’s of the real thing show what it will look like and sound like. Not quite the same and it does have some lag in the response as does my Amazon Echo as it has to fetch the information from the web. I am trying to see if I can use Amazon’s Echo as part of my software with the added bits to do face tracking and add some kind of human interaction. The Pi3 should be more than capable of this. I will have a separate motor controller board connected via serial link, possibly RS485, as I don’t have enough wires in the slip rings to accommodate them in the head and drive them from the Pi3.
I am actually having fun doing the mechanical design but the only downside is that my cad software doesn’t handle the smooth flow of the body parts, at least not without an upgrade to add the surfaces option.
@ Dave McLaughlin - have you built a test model to check the angles?
What CAD software do you use? It looks like it does a fairly good job.
Not built but using the software I can rotate in the CAD software and see the effects
I use Alibre Design which is now called Geomagic Design. It was under $1000 I think when I originally purchased if. Yearly maintenance to get the latest is cheap.
I did some tests tonight and I need to do some rework on the design. The angles don’t quite work out the way I wanted them too. I am also considering smaller motors that I found on DFRobot which will reduce the height of the overall design. The 3D cad models are cool to let you check things like this.
[quote=“Dave McLaughlin”]
I use Alibre Design which is now called Geomagic Design. It was under $1000 I think when I originally purchased if. Yearly maintenance to get the latest is cheap.[/quote]
Have you tried Fusion 360 yet? I’ve been really impressed so far. It’ll do all those same simulations but I really haven’t spent much time in that area yet. Would be curious to hear your review comparing the two if you have tried F360.
@ ianlee74 - I find that F360 is limiting. It feels like a cut down version of Inventor.
I think you need 3 motors to get a really good range of motion. That seems to be what JIBO has.
Using smaller motors will save you money on the 3d printing too.
Yeah, I was having a look at the design of Jibo last night and noticed that there is a third rotation in the very bottom. I am going to rework my design to use that 3rd one. Also using smaller motors means I can reduce the overall height.
The Seeed studio Kickstarter project is also going to allow me to get the voice interaction up and running a lot easier too so I am looking to how to mount that in the head next. 
Check this: http://s3files.core77.com/blog/images/290529_33852_37873_3zZ7czwOP.jpg if you havent seen it.
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Nice find.
They are using toothed belts instead of gears. Probably not a bad idea. Sparkfun offers them so I might just redesign using that instead.
@ Dave McLaughlin - “Toothed belts” are called timing belts.
I know that. :
Anyway, I decided to run with the gears as I could not find anything timing belt wise with a hole through the centre to allow the slip ring cables to pass through. I am trying to use as much as I can off the shelf so modifying one was not an option.
I’ve made quite a few changes to it, removing the rotate hub that stuck out the bottom from the head so that it looks better. Also created more of a globe shape than the half globe of the old design. Lots of work too, to reduce the material used with lots of slots to take out a lot of the material but not sacrifice the strength.
I change out the larger 37mm motors for smaller geared type with 60:1 ratio. They have heaps of torque for their small size and there is not a lot of weight to move around anyway.
With the recent Seeed Kickstarter for the speech recognition, that has boosted the work needed for that part. I am busy working on the QT5 interface on the Pi3 with OpenCV to do facial recognition.
I have a G80 dev board here and plan to test if that can handle the motor control and interrupt inputs from the motors. If that works, the G80 will become the motor controller for the design. An ATMEL AVR will take care of the LED ring in the base as I need something that can handle the strict timing on the LED’s.
@ Dave McLaughlin - much nicer looking design. I like it :dance:
What sort of speed can you get out of those motors with your additional gearing? Seems like it still needs to move fairly fast to look natural.
Thanks.
I actually changed my order for the motors to 300 rpm output speed and with the gearing ratio on the hub at 3:1 it should be around 100rpm at the body rotation points which should still allow it to rotate quite quickly. It’s easy to change out the motors for different ratio’s if my testing doesn’t work out. I have 2 motors and a speed controller on their way to test with. Should be here tomorrow. That will give me a good indication of what it can do. I’ll have to consider acceleration and deceleration depending on the start and end angles etc. Should be a nice learning exercise in motion control which will be something new to learn about although I do have PID experience for auto heading of ROV system this will be a little different.
motion control is next on your learning curve - looks like you have CAD down rock solid 
Before I was doing electronics and software, I spent my first 4 years as a mechanical engineering apprentice straight from school. I also working offshore on hydraulic ROV’s so I gained a good bit of mechanical know how
PS… The 3D CAD software makes designing a lot easier and you can almost make something fit 99.9% of the time.
Is that just a Neopixel ring? The G80 can handle it fine over SPI. I’ve done it using smaller boards. Check Codeshare for the driver.