Scarab Status Report
Part 2:

The work continues at a frenzied pace...


Pictures

Transmission, battery packs/side armour, front armour, and the weapon are in place. Starting to look like something. What, I don't know, but something. Also, you'll notice I've changed the bearing blocks along the way. I tried to use the same blocks I had for Dozer (stamped steel self aligning) but realized that when I tried to bring up the belt tension, the bearings "self aligned" themselves out of alignment and I ended up with a very funny looking drivetrain. These cast rigid blocks did a much better job of holding things aligned, but they were also VERY heavy. That, along with running out of time to lighten some key components, contributed significantly to my serious weight problem at BotBash...
Even before witnessing the awesome performance of Rhino at BBLV, I had always thought that the robotic equivalent of an M1-A tank or A-10 Warthog would be as little 'bot as possible built around as much gun (or in this case pneumatic pike) as possible. The cylinder is a 1 3/4" bore x 9" stroke surplus double-actuated cylinder found at Industrial Liquidators here in San Diego. An ideal pneumatic cylinder of this size would theoretically put about 360 pounds of punch into its throw at 150psi. Of course this cylinder is far from perfect, maybe even only 50% efficient (friction, and what-not), but some quick tests on the bench showed that whatever the output was, it was enough to split 2x4's and even do some damage to cinder-block.
One more look at the weapon. I love this thing. Its evil. A couple of people have asked about the point. Dare I give away my secret? Sure. Its a surveyer's plumb-weight. It had a small threaded hole for attachment to the plumb string. I bored that out on the drill press, and then tapped it for the funky thread on the cylinder. It took a little while to find a tap to match that thread. Found it at Junior's Tools (the only decent tool place in town that's open on Sundays, BTW).
The rear armour plate in process. I wanted this to be made from plexi, so that I would have someplace to attach the Rx antenna where I could be sure of good signal. Building an all-aluminum box wouldn't have done much for my receiver performance. This is scrap-bin stuff from local Ridout Plastics. When assembled, I looped the receiver wire back and forth across the plastic and just taped it down. (Sort of like the in-winshield AM car radio antennae). You can spot this in the upper left of the image below.
Oops, all the sudden, things got crowded in here! Actually, much of this work was in the final hours before I needed to pack and hit the road for BotBash (job got in the way of timely development), so I took a lot less pictures as I got to this point. A few things to point out: The Vantec RDFR23 at the top right, and the black cylinder is a LP Palmer "Stabilizer" regulator. This is a standard custom part from Palmer Pursuit Products with a special spring to allow it to work effectively down to tens of PSI (set to 140psi here). Most paintball stuff doesn't work below about 200, so you need to take care that the gear you get can do what you want. At the bottom you can see the solenoid valve that actuates the cylinder for the power stroke. This valve is from Grainger. It is connected with a braided steel line and quick-disconnect fitting which allows me to remove the tank/regulator assembly for filling.
Another interior shot where you can see the bracket I made to hold the Team Delta RCE47 mains disconnect switch. This was setup vertically and a hole was cut in the top armour so that the push-for-off action could be hit safely by a human, but was recessed to prevent (most?) accidental contact. The small holes in the button allowed me to turn on the mains by interting a scribe tool into the hole. This switch was wired to a small terminal block, which mainly just took the leads from the battery-block pair and distributed it to the Vantec and solenoid for the cylinder. The small project box in the upper right houses the receiver, Team Delta RCE200A e-switch, etc.
The solenoid valve is much larger than I needed for actuating the cylinder, I used this size due to the larger exhaust port which allowed it to retract with less resistance via these shock-cords. You can see them un-attached to the cylinder end in the photo above and attached to the piston via a custom aluminum "ear" at the front here. The zip-ties kept them organized so they wouldn't bind up on the edge of the front armour here. This system worked OK, but next time I'll leave more space and try a double-actuated approach. The ultra-slick pointy-end cover (USPEC) is a pvc joint...
Sitting on the bench on check-in night at botbash. We still didn't know how much we weighed (no scales at home), but my back-ometer told me we weren't going to be anywhere near the 30lb limit we were shooting for. I was right, we came in at about 45lbs! Let this be a lesson to all builders to have a scale on hand and use it frequently.
In this photo we've also just finished fitting our loaner Vantec '23. Turns out our Vantec was DOA from the factory and there was no time for a replacement. Dan Danknick of Team Delta was kind enough to loan us his spare. (With the usual u-breakit-u-buyit caveat). Without his generous offering, we'd have taken a lot of nice pictures and not had the wonderful experience of breaking our 'bot in short order. Having no working Vantec up to this point also meant that I did a crash-course in driving out in the parking lot. My only experience driving Scarab before the comp!
The only picture with the top on. This one courtesy of the BotBash site. The sign on top reads "DANGER: Unsafe. Do Not Use!". Unfortunately, due to the lighting, you can't really see the neat metallic green and gloss-black Scarab beetle paint job I applied right before going to bed on Thursday...


On to Competition


Copyright © 2000 Puppetmaster Robotics. All Rights Reserved. Original Images and Text are property of Puppetmaster Robotics.
Please contact webmaster@puppetmaster-robotics.com to request permission before reusing.