I finally got a chance to fully test out my slip ring last night with some servos.

I first had to finish soldering up my little boards that would handle signal routing and power.

Rather than try and explain in words and pictures how the setup works I made this short video to try and give a good overview and show the slip ring in action.

I still need to make little brackets to secure the D sockets to the boards, and decide the best place to locate them in Artoo.

See Also:

• Electrical System Update
• Slip Ring Spin Test
• Slip Ring – Cutting the Frame
• Slip Ring Update
• Slip Rings
• Variable 12-24V Converter

I stripped my first set of gears in a motor this weekend. I was goofing around on the driveway showing Artoo to some neighbors across the street when suddenly the dome stopped working. I heard this really bad crunching noise then a very quiet motor spinning.

I quickly pulled him into the workshop and the dome off to see what was up.

A couple of months ago I had lined the inside track of my dome bearing with some batting tape to help the dome wheel grip. It had been slipping and the resulting noise was very annoying. The tape seemed to be the perfect solution …… until the gearbox failed.

I think what had happened was I’d left R2 sitting in the van all day and when I finally unloaded him the glue on the tape had heated up and when I started to spin the dome it balled up – jamming the wheel and breaking the gearbox.

Gerard had a similar failure trying to fix the squeaky slipping wheel. He’d over tightened the tension spring which stopped the dome the moment the motor stopped – but again this put extra pressure on the gears in the Pittman motor causing them to fail.

So for now I’m back to having a squeaky dome.

I cut the hole for the slip ring tonight.

Started off by marking the center lines and then using a hole cutter to score the 7/8″ outline where the slip ring body would sit.

I then marked off and drilled holes where the slot would go for the cable plug to pass through

I used a Dremel and a hand saw to join the holes up

You can still just see the outline of the circle I’d marked

I then took a file and made the small circle notches either side of the slot to accommodate the slip ring

Testing that ring slip ring fit and that the plug will pass through

Top view of the slip ring secured in place

Now to solder up the connectors

I started work on my test slip ring tonight and hope to get it installed in the next few days and report back on a new group order.

The sample slip ring has eighteen 2A circuits and I plan on grouping together 6 or 8 for the +/- 12VDC uplink to the dome, leaving ten circuits for PWM/servo signals. To save on circuits I’m not planning on routing the +/- 5VDC from each of the PWM pairs through the slip ring. As a result each RC channel will require just one wire allocated on the slip ring. I’ll just tap of the 12VDC in the dome and re-create a separate 5VDC supply for the servos.

Out of the box the slip ring wires are loose and really needed protecting.

I bought some braided expandable nylon wire wrap from a local surplus electronics store for less than a dollar.

I wrapped the ends in electrical tape to hold things in place.

Now that I have the wire wrap in place I can start soldering the wires to the connectors.

Here’s an overview video on how I plan to implement the wiring

Here’s something else I’d forgotten I’d worked on before C4 and not posted.

The original dome periscope had a small raised lip around the side ports/windows. Neither my PVC or aluminum periscope kit has this so I improvised.

I used a 1″ Nylon gasket from the plumbing department at my local Ace Hardware store, and just superglued it in place. However, paint has a real hard time adhering to Nylon, so if I was to do this again I’d probably try and find an O ring made from something different. Also if you try and rough up it up you’ll get fine strands that will never go away.

I guess I’m posting this as an idea rather than a solution.

Here’s my latest short video tutorial, this time it’s on cutting your inner dome holes.

This was one of the first things I worked on a year ago, and I’ve finally mastered video editing enough to put something like this together.

Enjoy.

Related Posts:

• First Dome Hole Cut

Last week I made a new aluminum dome drive mech to replace the Daren Murrer’s HDPE version I’d been using. There wasn’t much wrong with the one I had to start with, but I gotten it in my head I wanted to try making one myself from aluminum to go with my new dome motor.

The one I created is a combination of Daren’s and the original Atomic Pickle design design. Here’s a photo of my original HDPE mechanism on my aluminum frame.

I used some 1/4″ scrap aluminum that already had a few holes in it, so I had to work around them using the original bracket as the template.

I don’t have a mill at home so everything would have to be either cut on the band saw, Dremeled, drilled or worked by hand tools like a file.

I rough cut the piece on the band saw and drilled the initial holes

The long hole in the center was greater from three smaller holes I’d drilled and filed away to create one big hole.

One issue I knew I would have was making the center hole/cut-out large enough to accommodate the approximate 1″ wide lip/step on on the motor. Also note how the drive shaft is off center due to the gear box.

At first I thought I could file away enough material but it would be slow going. I could also have bought a $40 1″ drill bit but I had another idea. My Dremel has a router attachment that could create a lip on the long slot that I’d created.

I forgot to take photos of the next few steps, but the rest of the mechanism that bolts to the frame is pretty simple, and just two blocks with a few holes in them. I made the main support piece a litte wider than on the Atomic Pickle design as I wanted to add extra support to the main bracket that holds the motor.

Here it is installed in the frame. Note, in some of these photos the motor is flipped the wrong way and the shaft should be toward the center of the frame.

At the pivot point I drilled and installed a bearing like the original Atomic Pickle design, but on hindsight I probably could have just stuck with Daren’s idea of just having a regular hole with a bolt through it.

Here’s the motor position correctly in the bracket

Overall I’m happy with how it came out and given a template and basic tools anyone could make one at home.

Here’s a short video of the new mechanism in action

Back when I was thinking about stepping up my Pittman dome motor to 24V, and not wanting to have the extra complication of tying two batteries together to make 24V, I’d ordered some small Voltage Converters from ebay to experiment with.

I’m probably not going to install it for the new Dome motor as it’s working fine at 12V, but I do have a 24V supply in the dome for the rear logic lights. This will allow me to have a single 12V battery and save some weight. There is a loss of energy and battery life due to the conversion, but it’s supposed to be in the 90% range.

Update 5/1/08: Andy tipped me off that these board can also be found here.