New Dome Drive Mech

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

Posted by Chris on January 3rd, 2008 in Dome, Electronics | 2 Comments

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Dome Drive / Pittman Motor

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.

Posted by Chris on December 4th, 2007 in Dome, Electronics | 3 Comments

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Center Leg Mount Plate/Block

Made a start on the Center Leg Mount last night. They’re based on a design by Atomic Pickle/JAG.

Started off with some aluminum plate and a nice block of 3/4″

I didn’t have access to a mill, so I rough cut the parts. I then sanded the block down on my bench sander till it fit and marked off the holes ready for cutting and tapping.

I’ll probably still go back at some point and mill out the center to reduce the weight.

Block inserted in leg

I still need to get some spacers to go between the plate and the frame.

Center Leg Attached

More photos

Posted by Chris on April 27th, 2007 in Legs | No Comments

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