Aluminum

[Cory]

Originally Posted by Alan Ing

Cory, if you don't mind, how did you retain your wheels and sprockets? Did you use an external retaining ring with a washer, did you just tap the end of the aluminum and just use a screw with a washer? I was thinking we might try this method since we have both a 1/2" and a 7/16" hex broach. I know you guys used a key before. What in particular do you like about the hex shaft over the keyway?

I have always thought your team's drivetrain was one of the best 6 wheelers but was surprised to hear that you used 7075 aluminum for the axles. I know your machine took quite a few hits during last years competition and to hear that the axles were only 1/2" 7075 is a bit enlightening.

Oh yeah, are you also using 25 pitch chain?

as Dave said, we used external retaining rings. They work great provided you leave yourself a little bit of wiggle room. When cutting the grooves on your shafts you need to not put them flush with whatever you're trying to retain, or else the snapring will have a hard time properly seating itself. You could drill and tap the ends and use bolts and washers just as easily, though. This would be easier than cutting the snapring grooves.

The hex shaft is great for a couple reasons, the main one being simplified assembly. Instead of needing a key, you just slide the sprocket/wheel on the shaft. I wasn't around in 2005, but just from fixing that year's robots last year, I can tell you it takes significantly longer to seat a woodruff key, slide the sprocket/wheel on, and put on a retaining ring than it does to slide a hex broached sprocket/wheel onto the shaft. We can swap out all 6 wheels in under a minute.

We've never had a problem with keys wearing, but it transmits torque over a larger surface area, which could be beneficial as well.

The 7075 shafts have been a dream. If we were to degrease the ones on the robot right now, they'd look practically identical to when they were new. We haven't had a single failure, or wear problem.

Since you've got the broaches, I'd strongly suggest you investigate using hex shafts for power transmission this year.

P.S. We'd love to have you guys by our lab again either before or after SVR. Let us know if you'd like to come.