You saw my first post extolling the virtues of chain. Yes. That was before we actually built it. I don't like chain for these reasons now:
Heavy.
Dirty.
Prone to falls off.
inefficient
space consuming.
liable to jam.

First of all, in our drive system there were these stuffs:(i kan spel.)
2x 60 tooth sprockets
8x 10 tooth sprockets
2x 40 tooth sprockets
2x 45 tooth sprockets
2x 22 tooth clutch sprockets (big thingies that have built in friction clutch)
20 steel bearning blocks

all were 5/8th inch bore.
all was #35 chain.

so we had ungodly amounts of 5/8th inch shaft (heavy) lotsa large carbon steel sprockets (heavy even with holes in em) lotsa heavy steel chain, lotsa heavy steel bearing blocks.


and it was so inefficient and liable to jam . . . . . well, we fixed the jam part by locktite-ing everything where it was supposed to be, but still. Next year we are getting access to a good digital or CNC mill and making us a gearbox. actually we have several ideas for next year, but they all assume we will need a drivetrain at all. Which we probably will, but we will wait and see.

ooo, yes, I forgot space consuming. our bot was a box of 80/20, most of the innards were taken by our 4 motor drive system, while 45's drive system had 6 motors, but they kept it on one far end of the bot . . . hardly took any room at all. There is so much we learned this year. Its not even funny. And if thats not funny, there are lots of things that aren't even funnier . . .. nooo, no Catch22 here today.

We have never had a chain fall off or jam. For the ineficiency, I'm not sure. Gears can be just as ineficient if not meshed and aligned properly. As for space and weight, I can really debate that. But we like chains and sprockets just because of the simplicity and robustness. It is so easy to set up a chain drive with simple tools and make it very effective and robust too.

Our robot:
2 Drills
2 Chias
-- All sprockets carbon steel #35--
4 10T
4 32T
2 35T
2 48T

42 inches in total of 5/8 keyway shaft

Very heavy but if you saw our robot in action at Phoenix you wouldn't complain about the weight.

Being tedious is my point. Gage blocks and indicators were created in the mid 1800's. So precise measurement has been around a while. Laying out a drive setup with a height gage and drilling holes on a drill press will work, but you still need to precisely measure the hole locations if you want a smooth, frictionless system. I'm sure the Wright Brothers used Gage Blocks and indicators to build a gas powered motor. You can't get a precise piston to wall measurement from a pair of dividers and expect that the piston will not sieze or rattle itself out of the bore. Or correct oil clearance on the bearings without a bore gage.

You can only hold as tight a tolerence as the machinery that you have to work with. The better the tools, the better you can repeatedly hold a tight tolerence. Modern machinery dramatically reduces the time required to Accurately machine a part, and beinng we are only given 6 weeks to design and build a robot....all the time you save...:cool: