Dozer Combat Robot Status Report
"The 'Best' is the Enemy of Good Enough"
Old Russian Engineering Proverb
Actual construction began early this month. As I'm getting used to working in this medium (I've worked with wood all my life, never with metal) - I'm finding the hardest part is knowing when stuff is "Good Enough" and to just leave it and move on to other things. Working with the tube steel I've chosen for the frame of Dozer was much easier thanks to the help of new Dozer team member Tom Deadrick. Tom has access to all of the proper tools like a horizontal bandsaw and a super TIG welding setup. More importantly, he has the experience to help me translate my pencil and paper drawings to real life. His welds are a thing of beauty, and his driving skills are second to none (Tom is another proud Impreza RS owner and an autocross monster!)
||The beginning of two transmission pod rails. There are four of these types of rails total, and these four rails are part of what will become the six frame rings that will form the tube frame of Dozer. Two transmission pod rails will be joined to form one of the modular transmission pods. I'm trying to keep the drivetrain/transmission pods and center/weapon pod totally modular - with an eye on possible BotBash, Lightweight, or even differently armed Middleweight entries in the future.|
|Here's a closeup of one of the uprights on the transmission pod rails. These will mount the Dayton bearing pillow blocks I got from Grainger.
You can also see one of Tom's contributions, some technology from the Kart-racing world. The trick mountings for the bearings are made from welded in stainless steel tubing. Rather than just cross drill the tubing (since it can be difficult to get accurately lined up holes since the drill bit tends to walk in the space between the walls of the tube), the tubing receives the bolts that will attach the bearing blocks. This gives a much stronger system to bolt to than if we had just drilled through the tubing.
||You might be a robot-building redneck if... you have robot parts up on blocks in your garage. Here I'm test fitting the bearing blocks, axle, and wheel for one of the transmission pods. The wheels are 10.5in Go-Kart wheels with a #35 60tooth sprocket attached. These were obtained from Northern. The axle shafts are actually 3/4" chromoly steel from IMS. Can't be beat for strength to weight!|
|Another shot of the test-fit wheel and bearings. The sprockets that are mounted will more than likely have to be drilled out for weight. These Dayton bearing blocks fit right in with the overbuilt-but-cheap theme of Dozer. They're not the lightest in the world (stamped steel), but they have a dynamic load capacity of nearly 3000lbs, and they're something like $12 each!
||Here I'm starting to lay out the Aluminum angle stock for the mounts for the drive motors. Since I don't have access to all of the cutting tools I need at home, I tend to work with large plates and pieces of tube and then cut them to size the next time I get access to the proper tools. So, this single piece of 1/4" plate will actually end up being two motor bases with mounts, and there will be enough left over for one of the other mounts I'll make later. The numbers in red correspond to the numbers on the plate. I'm just freehanding the mounting holes, so the angle blocks won't be interchangable with their respective mounts on the plate, but the numbering keeps things straight. Remember, "The Best is the Enemy of Good Enough!"|
|Starting to tap the holes in the base plates. Tapping Aluminum by hand is almost fun at this point. (Lets see if I still say that at the end of this project, at which time I will have probably tapped 200+ holes).
||Add a couple of modified hose clamps, and Voila! A completed motor mount. These mounts fit the 4" diameter pancake motors I bought from a local surplus places Industrial Liquidators and Gateway Electronics. These motors were apparently used in the EV Warrior Electric Bicycle before the company folded. I've seen these motors for sale on Ebay and it the Alltronics catalog, IIRC. Often for as low as $10 each. They're rated at 2000rpm at 12v. They're wound with a preferential direction in mind, so care must be taken to match the CW and CCW versions of the motors (different part #'s) with the correct application. Using a calibrated shunt (thanks to Dan Danknick of Team Delta) we tested these at ~4A No-Load and ~46A @ Stall at 12volts in the preferential direction. We'll see how they do at 24v! Mwuhoohoohahahaa! (Much evil laughter ensues)|
On to March
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