Stronghold Drivetrain Review

[JesseK]

Basic:

• West Coast Drive, 6 tires
• WCP DS - 2 CIM - 14:60 & 24:50 reductions
• Random Amazon tires, 4.15" from middle axle center to floor @ 35 PSI with full robot weight (8.3" diameter wheel for calculations)
• VP Aluminum clamping bearing blocks
• 6WD Drop Center, using the WCP offsets to raise outer/front and lower middle - total drop = 1/8"
• VP Aluminum Hex shaft for wheel axles

Advanced:

• Tire pressures (F/M/R) were 30/35/35
• On the floor, the wheel raise is more like 3/16" due to the tire pressures
• Track Width = 24"
• Wheel Base = 10.5"
• Extra 18T -> 38T sprocket reduction after the gearbox, iirc maximum theoretical speed was 14 ft/s
• Eventually settled on VEX Pro #25 HD chain with VP HD master links (don't use normal master links!), and once we got them everywhere we had no chains come off

Control:

• Standard tank-steering with 2 joysticks
• Optional "Drive Straight" arcade mode, legacy carryover from 2012
• Talon SRX "Speed PID" mapped joystick input to a speed, where maximum joystick input = maximum speed limit set via a constant. Set limit to 9 ft/s early in the season, incrementally raised to 12.5 ft/s by the end of WCMPs.
• Not sure if the kids put in a conversion of ticks/s -> ft/s, or if the SRX has it. Nice feature though.
• Testing showed peak of 12.1 ft/s as read by the SRX's. (Who needs a simulator any more? )
• NavX to detect defense crossing - though rough terrain didn't register too well...

Maintenance:

• Check tire pressures 2x a day
• Turns out the middle wheel blocks were 'floating' on one side and therefore would put excess tension on the chain leading to the front wheels. This wasn't a problem once we switched everything to VP HD chain. Probably should have gone #35 in design though.
• There was no metal fatigue on any of the sprockets, but some of the black anodization came off of each sprocket
• Bent one of the rear axles, but since it's WCD it was crazy-easy to replace
• Had a CIM wobble loose at WCMPs. Found it during one of our half-day full robot inspections, so it didn't cause much wear on the gearbox.
• Lightly re-grease gearboxes at start of event and at start of elims