Quote:
Originally Posted by AdamHeard
Is this a west coast style drivetrain? What are the advantages of moving the chain inside?
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It's not like WCD, though I have thoroughly studied WCD and tried to deduce many of the design decisions along the way. Mainly the wheels aren't cantilevered and there's no need to add additional supports for bumpers. I know our welder would balk at a 973/254 side bumper rail, yet a couple of our mentors want more support than what 2793 and a few others had this year. The axles are live axles, which is why the 2x1 is needed. The big thing we lack is knowledge about automated CNC'ing*. While I understand we don't *need* CNC to do WCD-esque drives, I do have other mentors to convince (and they're a stubborn bunch). There are some other things that are 'wanted', like direct drive & a multi-level frame, yet we also have to live within our limitations. I think I've come up with a concept that can do those few things without increasing complexity of the drive train.
The sprockets are housed inside the box tubing blocks more for the fact that we won't have to purchase a hex broach and learn its process than anything. The 2x1 tubing will be in 4" segments, so the whole chain isn't inside the tubing. I still wonder about how much of a hassle it will be during assembly -- particularly with belts (I want to leave the option open for next year). We want live hex axles so there's a naturally-sturdy structure between the wheel blocks if we lathe the ends down for round bearings. We want live axles because we don't want slight imperfections in a bearing-wheel combination to throw off the chain on impact like it's done every year (e.g. Plaction wheel + pressed bearing was discovered this year). Hex axles will also allow us to use 4" AM performance wheels without an additional hub, which is a decent money saver when we're talking about 6 wheels. I may even try to find a sponsor with a 3D printer so we can get a custom wheel diameter and naturally-purple coloring (maybe).
We're going down to minimalistic mechanical mentor support for the Fall from what I can tell (work/school issues) so mechanical knowledge will be scarce. Additionally, we only have 1 mechanical FRC student returning this year. Sticking with what we know, at least for this year, will be key for us to expand upon our 2011 successes.
Jim, I'll look into the button head screws to see what's available. If we use 16T sprockets, there will be about 0.15" of clearance for a bolt head before a chain touches it.
*The year we tried auto-CNC at our knowledge level was disastrous (2009 ... record of 6-18-2 because we could barely move). We do have a no-slop, ~0.01" precision manual mill now, so I'm stepping up the game somewhat with direct drive.