I’ve been working on this drive design for a while. Single speed gearboxes, speed of 10fps on the 4 inch wheels. Middle wheel is wider (I don’t want to go into the traction discussion again, so please take it to the appropriate threads) to aid pushing. Simple tensioning method using my normal bolt pull system.
What with the trend of flat fields, I think we’ll be climbing soon… It’s pretty easy to tweak this thing to use 6 inch wheels. Just swap one gear and the wheels.
Questions and comments welcome, also: I’ll email you the CAD if you want it. It’s in Inventor 08.
You definitely do not need a 2 speed transmission to climb things. All a 2 speed would really help with is allow you to be a bit more precise in maneuvering. The important things to consider when having to climb are approach/departure angle, breakover angle, center of gravity, and traction.
I do really like this design although I do favor 2 speed transmissions for the ability to push and to be agile when you want. I’m glad Ive inspired a little West Coast off of sorts. Who’s next?
I hate to say it, but this design was cooking long before you brought it up. It was you bringing it up that inspired me to post the render. Weight is around 35 for the entire assembly, and that’s with chain (not shown in the render)
The bumper mounts aren’t actually finished in this render. The final versions will have 4 .25" thick plates welded to each of the jutting extrusions pieces on each side. Each plate will have two 1/4-20 holes for mounting the bumper lock bars, something I’ve been cooking up to allow easy to swap bumpers. Imagine something akin to a door hinge, that allows a bolt to be put in the top on each peg to secure the side bumpers.
EDIT: Yeah Squirrel, it’s all 2x1x.125 wall extrusion. The goal was to keep the chassis to only one material to keep the cost down, and the BOM simpler
Actually, after reading over what you said, let’s see how many iterations of the West Coast Drive there are out there! If you’ve got one designed, put the render up on www.tinypic.com and throw it up here!
Nice design, that kind of set up has been proven to work tons of times. What kind of guts do you have in the transmissions? Are they completely stock components (minus sideplates), or do some of the shafts/gears need machining?
It certainly isn’t, the traction limit for roughtop or wedgetop drivetrains (2 CIMS) is closer to 6.5 ft/sec for a full weight robot. Still, we ran wedgetop tread on our single speed robot last year at about 11 ft/sec and didn’t have any problems. Of course, we didn’t have to push anyone either…
I made one a little while ago that’s similar to yours in that it is just a small single speed drive base, but uses cantilevered dead axles instead of live axles. Not really west coast, but still… :rolleyes: Comes in to about the same weight as yours, too, about 35 lbs with chain (says inventor). The transmissions are about as itty bitty as they can be.
You’re assuming that this is the complete assembly for climbing. It was mentioned that some small changes in the event of climbing being required are easily doable on this design. One gear change per box, and 6 inch wheel instead of 4 inchers. Or, I could leave one side open and put a roller on the front, much akin the 254 during raising the bar (I think theirs was to stop them from rolling over balls, but a few small mods and it would work for ramp climbing).
EDIT: I never sleep… I need to stop forum lurking…
ok, so I’ve been looking at these West Coast drives forever, but I still can’t figure out where the bearing blocks for the wheels come from. Are they an off the shelf part you can get from mcmaster by any chance? My team has no milling whatsoever so I’m stuck with finding parts from a store.