1/31 Drivetrain Update and Next Steps

This weekend Jane, Harry and others helped me push hard on getting the frame all welded up, and it is nearly complete. The ball-picker is also welded, with a special 9º “wrist kink” to make it easier to roll onto the ball and capture it without driving over it.

Both roll bars (or more properly “portcullis-crashing bars”) have been fabricated and attached to the lower frame perimeter, and the axle-mounting plates have been welded in place. The frame is very light (I guess about 10 lbs, without CIMS and wheels) and very, very rigid. 🙂 I estimate with CIMs, wheels and steering motors on the frame, the combined weight will be around 50 pounds.


Here are things I’d like folks to help with next. Please do what you can to get teams of kids working effectively on these:

  1. Grind and polish the welds. The fastest way to do this is with the angle grinder fitted with the flat “flappy wheel”. Sadly that tool can’t reach into the deep corners, so those will need to be filed by hand. After the welds are ground flat, wire brush the entire frame so it looks awesome! When it’s all pretty and the welding is 100% complete, we can hit it with car wax so it stays super-shiny!
  2. Use the chassis punch to expand the 4 axle holes to 3/4″, then install the axles with aluminum setscrew collars on both sides of the plate. Check clearances right away – if the CIMs can’t clear the frame, tell Kate so she can fab up some longer axles. With wheels on, check the rollbar height. It should be 15″ in the middle and 14″ at the tailgate.
  3. The upper frame perimeter is already welded into a rectangle, but needs to be notched and attached to the roll bars, frame and “breadpan”. Spacing between the upper and lower perimeter is 3″. Fit and weld a center-drilled rectangular plate in the rear on the centerline for the winch fairlead.
  4. After the upper frame is mounted, a section of the upper frame (upper only!) needs to be chopped out in front to accommodate the dozer. Test and determine if stiffening triangles will be needed to support the front bumper sections against collisions.
  5. Next, matching 1/4″ holes must be drilled in the frame perimeter and the wooden bumpers for studs. Make sure the top of the wooden bumpers cannot exceed 12″ from the floor (move them down to 11.5″) Install threaded studs in the wood bumper sides, pointed inward and secured with push nuts. Then install T-nuts in the front & rear bumper segments and secure them with an internal plate (large fender washer?) so they can’t be inadvertently knocked out into the insides of the bumper.
  6. With the bumpers “noodled” and in place, work out the correct placement of the pivot for the dozer.
  7. Devise a motor & mount for the dozer. I think a window motor, or a window/gearmotor hybrid would be good for this. Consider catapult space claims. Look at last year’s robot conveyor belt for an idea of how to build one, and consult with Freddy, who will need to build another hybrid motor for the climbing winch.
  8. Help Donald design and build the tie rods, drag link and steering motors (window or snowblower motors)
  9. Where does the ball shooter fit?
  10. Make a battery mount.

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