Then new dome motor (a surplus Pittman GM9236) arrived today and I thought I’d share a short video to compare it to the original underpowered GM9413 motor I had been using.

It’s still runs at 12V, so no need to upgrade my electrical system to 24V. It spins a lot faster and definitely has a lot more torque.

Here’s the original GM9413 for comparison.

And finally, here’s a quick side by side shot of the two motors, the GM9236 is on the left. It’s a little bit longer and has a small shaft at the bottom which I think is to connect an encoding wheel to.

I’ve continued to do research and testing on my dome drive system, and it does look like I need to change the motor out for something with a bit more humph.

It seem that a few people are happy with driving the recommended GM9413 Pittman motor at 24V instead of 12V with good results, but I really want to avoid introducing the complexity of 24V into my system just for one motor. It will complicate charging the batteries at best and the shorten the system run time between charges, and at worse reduce the overall battery life unnecessarily.

In the last day or so I’ve got a lot of great advice from fellow builders, including a lot of links that helped me decide which new motor to go with. I wanted to stay with a Pittman if I could to hopefully avoid redesigning the dome drive system, and it looks like one of the variations of the Pittman GM9236 would work. It comes in a few different gearings and voltage ratings.

There was one specific 12V version I was shopping around for, the GM2936S018, which delivers about 3 times the torque, and about twice the RPMs of my current motor, but it was around $130, and I’d rather find something a little cheaper if I could. Then Bob pointed me at another GM9236 model that was very similar, but only $23 at a surplus store. They’re used/surplus but probably worth the risk so I ordered one to try. It has very similar specs delivering a lot more torque and hopefully went it’s installed, spin the dome a little faster 🙂

So here’s the links I used for my research and where to find motors

• Pittman website – not very good if want to look up older models, and you need to register to download specs.
• Skycraft Surplus – carries a lot of surplus motors, and right now has the GM9236 in stock.
• Skycraft’s Pittman Motor Guide
• Click Automation’s Pittman Spec and Price List– good overview and side by side comparison of a lot of the Pittman’s out there.

Tonight I’ve started to work on some dome stuff, including the dome drive system which has been bugging me for months.

I’m using Darren’s dome drive kit (based on Atomic Pickle’s) and it uses the Pittman GM9413-2 geared motor. Spec’d at 12v, 19.7:1, 142RPM.

To me it seems sluggish and rotates slowly compared to a lot of other droids I’ve seen, especially when I change direction. It could be the weight of the dome, which is around 17lb with all the accessories. Including all alu parts, like HP’s, surrounds, radar eye, dome ring, and periscope, plus the batteries, smoke/fire-extinguisher etc. etc. But I’m sure I’m not the only one with a heavy dome.

I’m wondering if others are experiences sluggish domes who are using this Pittman either from Darren’s kit or from AP’s? Especially if your dome is heavy?

According to the GM9413-2 data sheet on the AP site, the motor is rated at 12v, which is what I’ve been running it at, but on the motor itself the label says 12/24v.

I’d rather not run it as 24v if I can help it – but if it would help I could re-configure some of my batteries as a last resort.

The only other thing I can think of is the slight sagging in the mounting, but the motor is making full contact with the rockler bearing. Maybe it’s not doing a great job of holding on or maybe pushing too hard against the rockler bearing?

I know many Sennaites are using the Saturn motors at 24v for the dome, but I’d rather not switch class of motors right now. I’ve posted to the Yahoo! Group to see if anyone has some suggestions specific to the Pittman motors.

Edited to add some videos. Here’s the Pittman running at 12v directly off a battery, no speed controller so startup is instant and it looks okay right now which I don’t understand. I’m wondering if it’s a speed controller issue, or maybe even a problem when he’s angled in 3 legged mode. mmm.

And here it is running at 24v – super fast I know, but I’d rather the top speed be fast and I can slow it down with the transmitter/speed controller commands.

Now to troubleshoot why the 12v spin seems okay.

I did some further testing tonight, and held the body at an angle while the dome spun. Man, is there a lot of force whipping around while it turns, even at the slower 12v. I can feel it struggle on the up swing as the two heavier side of the dome comes around. 24v helped a lot but I need to go back and put the speed controller back in the loop to confirm my test and see how snappy it is looking left and right.

I’ve come to the conclusion that external dome bump switches are a bad idea, for events at least.

I like the convenience of being able to quickly turn off the dome lights to save the battery, but kids quickly work out what they do and are constantly playing with them. They can’t do much damage but i’s very annoying, and I’m leaning toward replacing them with an internal switch even though it’ll be a pain to get at. I’m not sure if I’d leave the dead switches in place or replace them with simple bumps.

If you’re about to go down this route I’d personally recommend against having external switches of any kind.

Well I’m back working on R2. It’s been a while since I’ve done anything on him and I’ve still got a long list of big to-do’s. Sadly, instead of working on the small things I’ve been avoiding everything.

Inspired by reading Victors success with the Mist/Fire Extinguisher effect this week I decided I’d give it a go this weekend, hoping it would kick start me going back to work on more difficult things like the skins.

The mist is created by an inverted can of compress air normally used to dust PC’s and office equipment. When it’s inverted rather than spray air, a watery/icy mist comes out.

I decided to put the air cannister and output in the dome instead of the body. I really liked the idea of popping open a dome hatch/side panel and having something come out, and I thought this would be perfect.

I’d already bought a cheap solenoid which was part of a trunk release kit I found on eBay. I had looked locally, but eBay seemed to be cheaper. Wiring it in was a snap and it’s only a few wires. It’s triggered with a spare channel on my RF remote.

I cut a 1 1/2″ acrylic strip and bent it into an L shape. I bolted it to the Dome Mounting Ring and then used clamps to hold the cannister and solenoid to it.

I drilled a small hole in the trigger of the air cannister and connected it to the solenoid with a bend paper clip.

Here’s a rough diagram of how it’s wired

Space in the dome is tight and I’m sure I’ll need to move things around or lower/angle the cannister more to accommodate the periscope lift mech.

Here a short movie clip of the first test with the dome off

Then with the dome on

I still need to add a hinge to the hatch and power it with a servo. I did tinker a bit with the Robart hinges but decided to leave this for tomorrow.

My dome has a self contained power system, and I wanted to use the dome bumps as switches. Rather than re-invest the wheel I decided to copy what Victor had already done as it looked like a great solution.

The switches are from Radio Shack, Part #275-693. The original surrounds on the switches are square’ish and need rounding.

Here’s the switches before and after sanding. I carefully spun them against a bench sander to remove the corners.

Here they are all painted and ready to install

There is a catch to painting them. You basically have to do it twice because once you flip the switch it exposes an area that the paint can’t reach on the first pass.

Next up I had to drill out the inner and outer dome for the switches, but the drill bit I had wasn’t quite big enough so I had to fill down the last bit to get a good fit.

I’ve not posted in a few days – Been feverishly working on R2 for C4. Hoping once I get back I’ll go through my photos and post some retro updates.

Unfortunately a few days ago I could have almost cried. I’ve spent months nurturing my dome and just as I was setting him down on the table after applying the Silicon to bond the two layers together he slipped out of my hands and hit the floor hard. This was the result 🙁

I almost gave up at this point, but I’ve muddled through the best I can and finished the dome and I will have an fully operational R2 at C4.

I can see me buying another one to do it all over again.

Lots more dome work in the last few days. Focus was to get all the internal stuff mounted – Holo Projectors, PSI and Front and Rear Logics.

I wasn’t very happy with my previous attempt of drilling holes through the inner dome and using counter sunk screws. By the time I’d counter sunk them enough the holes had gotten so big that the screws could pull through easily. Attempts to JB Weld the screws on the inside of the dome didn’t work so well either.

Here’s what my old mounting system looked like

It really looked like I may have to do what most other builders do and that’s goop the crap out of each part – Locking them in place for good.

But a quick visit to see my friend Richard resulted in a cool solution that I’d not seen done before. He came up with the idea of having a single mounting plate for each side of the dome which would hold everything and be easily removed if need be.

After a bunch of prototypes this is what we came up with. Just 3 screws holds everything in place. I can’t believe how simple the design is.

The PSI’s are inserted into a cut down pipe fitting secured with a screw, the HP’s just press fit to the dome by the plate and the logics are held on using the bracket/box.

We still needed to secure the plate in place, and the only good way to do it was to bolt it to the inner dome – which hadn’t worked too well previously. We tried JB Welding the screws to the surface of the dome but they came off easy.

Richard remember the trick of pulling aluminum into a cone/dimple like on the side of a home made Luke Graflex lightsaber – the tool used to be called a “Shoulder Puller” back in the day when people still made their own Graflex’s. Here’s what Richard used.

Simply drill a hole in the dome and insert the screw and tighten down on the collar which is on the inside of the dome. I think we started it off with a thinner screw then switched to the final size. I should name it the Dome Hole Puller.

In the end we used 1/2″ 10-32 screws which are much bigger than what was originally holding things in place a few months ago. No chance of things pulling through now.

Plate is somewhat flexible, so if someone pushes on things then it’ll give a bit rather than failing or things popping out of place.

I also decided to switch back to the old style logic surrounds. Not having the front outer plate on the new version was bugging me. I’m hoping to get the panels cleanup and painted tomorrow.

A couple of screw ups/lessons learned along the way. JB Weld didn’t want to hold the screws in place, even when going through the dome. So in the end I notched the underside of each screw a bunch of times and scored the hole with a dremel. As of right now things seem very solid and once the outer dome goes on there’s no way for things to move…hopefully.

A big notch was also cut in the dome ring by mistake while making room for a PSI. I’ve tried to fill it with a piece of aluminum and JB Weld and I’m hoping it will not be noticeable once the outer dome goes on.

The marks in the top band will be covered by the blue paint, but behind that is the patch which is visible. It wouldn’t be so bad if the dome touched the dome ring at the bottom, but there needs to be a slight gap.

I also had one hole from my previous attempt of mounting things that needed fixing. It fell on a panel seam line and I ended up plugging it with a aluminum rivet I filed down. You can hardly notice it with the outer dome on.

And tonight I finally got all the pie panels cut out, so I’m very close to being able to glue the two domes together.