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

[TheOrangeCrush]

Team 3026 Orange Crush is proud to present MecaTrak.


MecaTrak is a revolutionary and never before seen dual drive train that gives us the agility of mecanum wheels but by deploying two air cylinders it drops a set of custom made tracks to give us the needed power and traction for defenses and robot to robot challenges. The tracks are made of #35 attachment chain with riveted pads attached to the chain.

We started development in October 2015 and went through several iterations of prototypes before the final product made its way onto the competition bot.

Link to October 2015 Prototype
https://www.youtube.com/watch?v=2JImlM7Ed-Y

Youtube Video of MecaTrak
https://www.youtube.com/watch?v=z2TWEV4n0wQ

MecaTrak Specs

Mecanum

• 6 inch Andy Mark mecanum wheels
• Speed - 15 feet per second

Tracks

• Lifts the robot .5 inches off of the mecanum wheels
• #35 attachment chain with riveted pads
• Pads can hold a box at 25 degrees
• Speed – 8 feet per second

[1625Brennan]

on 1625 we used tank treads with a twist, we added omni wheels in the front by raising the tread, this allowed us to tighten the turning radius. Only the back pulley and omni made contact while on flat ground although when crossing a defense the tread would contact making it so we had little to no issues crossing. We had originally started with Brecoflex treads although after our first comp we opted to change to our Andymark treads due to wear. The only significant wear we encountered after that was damage to our omnis, they would "jam" and not allow a roller to move after repeated massive impacts. Our whole drivetrain was ran by Vex 775Pros, 2 powered each tank tread (4 total) and 1 for each omni (2 total) Overall we are quite pleased with our choices

[daliberator]

Originally Posted by JesseK

Maintenance:

• Check tire pressures 2x a day

We used Andymark pneumatic tires and didn't have any problems with air pressure. In fact, I'm pretty sure I can count on one hand the number of times we checked them throughout the season. Did you guys have to top yours off frequently?

[abbymarie]

We used 8 inch pneumatic wheel in a 6 wheel drive train, using the belts from the Kit of Parts. It worked amazing for breaching the defenses, we never got stuck on anything! Tire pressure was never a problem, we maybe checked it once or twice.

[daliberator]

Originally Posted by abbymarie

We used 8 inch pneumatic wheel in a 6 wheel drive train, using the belts from the Kit of Parts. It worked amazing for breaching the defenses, we never got stuck on anything! Tire pressure was never a problem, we maybe checked it once or twice.

What did you use for a chassis? Did you use AM wheels? The KoP belts worked very nice for us as well.

[BoilerMentor]

I never thought I'd see the day that we'd use a treaded drive, but this was the year.

Basic:
Waterjetted, folded aluminum drive pods with custom pulley layout
AM Rhino Belts
Rhino pulleys (replaced due to cracking during build season)
Custom single reduction, single speed gearbox ~6:1
2 cims and 1 mini cim per side
static belt tensioner per side

Advanced:
3 pulleys at "ground level" center ~1/8" lower
2 pulleys at "frame level"
Bevel at each end to allow crossing in either direction
~26" Width (outside to outside)
~30" length (outside to outside at frame level pulleys)
~20" of floor contact per side
Belt tension was entirely subjective, but we never threw a belt

Control:
3 Talon SRX motor controllers per side
split stick arcade drive scheme on a game pad

Maintenance:
gearboxes regreased at each competition
pulleys inspected for cracking (none observed through competition season)
belt tension verified
belts never replaced

Observations:
Despite my aversion to treaded drives, I'm very pleased with the behavior and performance of our drive train this season. If the game required it, I think we'd certainly dust this one off and use it again.

Power availability is going to drive our design and gearing decisions in the future. The brown out situation lost us some matches we really should have won, or at a minimum cost us some time because of added difficulty in executing crossings.

If we were approaching this problem again, I firmly believe the choice to neglect to add suspension is the right one. Yes, it would have reduced the wear and tear on the robot from hard impacts, but from observing behavior of other treaded drives that incorporate suspension it would appear that the issue of appropriate spring rates and damping aren't trivial and can lead to really problematic behavior through defense crossings.

[Nightwing430]

Originally Posted by abbymarie

We used 8 inch pneumatic wheel in a 6 wheel drive train, using the belts from the Kit of Parts. It worked amazing for breaching the defenses, we never got stuck on anything! Tire pressure was never a problem, we maybe checked it once or twice.

This is what my team used for our drive train. We though it worked really well for breaching and we didn't have to check the tires that much either. Boulders were a problem for my team when we ran over them but I'm not blaming that on the drive train we chose. We also modified it to were it was tank drive which is what our robot last year used so we had more experience driving it like that.

[Gdeaver]

We went with treads. This is what we did. Over all happy with the results.
http://wiki.team1640.com/index.php?t...II_Drive-Train

[daliberator]

Originally Posted by Gdeaver

We went with treads. This is what we did. Over all happy with the results.
http://wiki.team1640.com/index.php?t...II_Drive-Train

That looks really cool! I know you guys have been developing an amazing swerve drive for the past few years. Were there any thoughts of modifying it to work with 8" pneumatic wheels?

[qscgy]

We went with 6 8" pneumatic wheels and single-speed 3-CIM WC gearboxes. Front and back wheels were mounted in Versablocks, with 1/8" drop centers. Our team has been using 9mm belts for the past couple of years, but we used #35 chain and WCP cam tensioners this year due to space constraints, as we needed much larger belt pulleys than would fit.