Quote:
Originally Posted by Michael Blake
So, a better representation would be:
Live-axle Mass = sprocket, hub(s), shaft, wheel, mounting screws
Dead-axle Mass = sprocket, wheel, mounting screws
BOTH approaches use bearings... the Live-axle would have at least _two_ friction points... and the Dead-axle would have only _one_ friction point...
We shouldn't underestimate the friction/drag created at each bearing-point on a Live-axel setup... if you insert a shaft into one secured flange-bearing and spin with your hand and then take the same shaft and insert into two secured flange-bearings and spin with your hand, you'll notice it takes more effort to spin the shaft... now times that by six wheels...
ALSO, the mechanics of the Live-axle setup causes more friction/resistance at the bearings because of the angular pressures caused by the shaft pivoting inside the bearings as the pressures on the attached wheel (at far end of the shaft) change...
I KNOW these are _minute_ differences (or, are they?)... but, it's fun to think this through...
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This is quite a bit off actually. You'd still have two bearings in a wheel in a dead axle system.
For a dead axle system, your axle is held by two plates, often inches apart, and any tolerance issues will make that shaft crooked and lead to extra friction on whatever is driving it.
The double bearing issue you mention for live axle has always been a nonissue for us, our bearing blocks are one piece for the bearings and use the same hole. The load from the cantilever is higher, that is true, but it's still well within the spec of the bearing. We slammed down HARD in 2010 and didn't have a single issue anywhere, and our drive was still nice and low friction at the end of the season. I'd argue that few teams had lower friction drivetrains than us.
If anyone wants to see our live axle drivetrain, check out my uploads. Our previous 5 robots are there, all using variations of the same system.