2016:Drivetrain

12/21/2016

Frame information

• drive base dimensions: 25" wide x 37" long
• Front is straight across
• Rear is 16" straight
• Both ends are chamfered 4.5" width x 5" length
• 6 wheel design with pneumatic tires, wheel spacing is 9.5" between wheels
• Wheel axles are 9 inches from each end
• Center wheel dropped 1/4 inch
• Frame construction is "c-channel" and 1.125 wide x 1.250 tall and will be a welded construction
• We tested a frame mock up over all the defenses. The comment is the Frise will require a belly pan
• The moat will require a chamfer on the bottom edge of the rear and front members

Transmission

• CIMple box from Andy Mark 12 x 56 tooth (4.167:1 reduction)
• Speed sensor will be mounted on the Cimplebox ecoder take-off
• The secondary reduction will be 12 x 36 tooth for a 14:1 overall reduction
• the design wheel speed is 10.29 ft/s loaded
• (We are considering mounting the drive chains on the outboard side of the wheel channel to create more space in the center of the robot)
• The chain from the 36T front wheel sprockets will be routed around a high idler to keep it away from obstacles between the wheels.

Bumpers

• Scaling team requested bottom edge of bumper height to be 5 1/4" off the floor  

Gyro 

• Analog Devices ADW22307 1-axis Analog Gyroscope

Battery Box

• Battery box design is forthcoming. Placement may be able to help tune the robot CG, depending on the placement of the other robot mechanisms/systems.

Update Sunday 1/24/2016

• CAD design of wheel blocks
• Added chain to CAD model
• Completed CAD design of the Idler Support Block

Update Tuesday 1/26/2016

• Continued CAD work for the drive base.
• Added bumpers to drivebase CAD design
• Completed enough of the drive base to submit it for inclusion in final assembly

Update Wednesday 1/27/2016

• Fabricated the drive base frame
• Generated drawings for transmission mounting platform
• Generated drawings for drive base assembly

Update Thursday 1/28/2016

• Cut the transmission mounting platform spacers
• Cut the copper spacers for the wheels
• Fabrication of the drivebase transmission mounting platform
• Cut the front C-channel angles for the drive base frame.
• Prepared the drivebase frame for welding
• Delivered the frame to be welded at 8pm.

Update Saturday 1/30/2016

• Drive base returns from the welder. Thank you Dave Drelick for a fantastic job!
• Filed the drive base and painted it (black).
• Painted the Wheel blocks (red).
• Assembled the wheel blocks onto the drive base frame

Update Sunday 1/31/2016

• Assembly of the transmission mounting pads.  Had to reassemble several times due to several issues:
  •  Chain clearance cutouts had to be widened 
  • Spacers were different heights and had to be "graded" to get enough of approximately the same height
  • One wheel was assembled with the wrong spacer and had to be redone.
• Chained left side of robot.  Discovered that the idler sprocket bracket does not have enough adjustment for chain tensioning.

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Wheel Idler does not have chain tensioning adjustment range.  We forgot to account for the nut!

OriginalDriveBaseIdler.PNG

OriginalDriveBaseIdlerDetail.PNG

Update Tuesday 2/2/2016

• Assembly of the the drivebase continued.  
• Completed chaining of the drivetrain.
• Added shaft encoder to the CIMple box transmission.
• Finished fabricating blocks for the idler redesign.  The fabrication did not go well: tapped holes were too big, blocks did not have clearance to pass the tires, and alignment of the axle in the blocks proved almost impossible.  We shaved an angle off the blocks to fit around the wheels, but no one expects this to be the final design.  So back to the drawing board.

The robot drivetrain was weighed: 45 lbs

The drivetrain is tight.  Speculation is that the problem is not chronic--it is probably due to chaining too tight, wheel spacers too tight, and possibly gearbox not broken in.

Update Wednesday 2/3/2016

• Assembly of the drive base continued.
• Updated the wiki

Wheel Idler Block Modification

The original idler block did not permit enough adjustment for proper chain tensioning.  The second design was too difficult to adjust and came too close to the wheels.  The third design idea is to hang the idler from a block across the wheel channel by I-bolts.