Hex vs. Dead axle

Ok, me (being new just last year) has to figure out what the pros/cons are to each of these set ups… also what the hex set up really is!

last year, the kitbot was appropriately set up to do what I know as a dead axil… where there is a bolt of the appropriate dimentions bolted to the chassis, and the skyway wheels have their berings on that bolt… and the sprocket is bolted to the skyway. Pretty sure we aren’t animateing the axil here.

Now comes this Hex boar from andymark, and some mention of hex driven drivetrains or something. Elighten me!!! Please?

So far, so good.

Basically, hex shafts (and round shafts with keyways) are both forms of live axles. With live axles, your bearings are held in pillow blocks to allow the shaft to rotate. This way, for example, a sprocket doesn’t have to be physically connected to a wheel to transmit power. This can yield some advantages in maintenance if you design correctly, and live axles can be cantilevered, where a bearing is not the outermost element on a shaft. (Look at the drivetrains of 254/968/60/22/4/980, and you’ll see what I mean).

The big advantage that hex shafts have over round shafts with a keyway is that the hex shaft is the key–power is transmitted in six places, as opposed to the usual one or two with a keyway. It also means you don’t have to fish for a new key when your original breaks…but generally at a higher cost, if you’ve got to broach your own. (1/2" hex broaches are by no means cheap.)


fyi: when people use hex it is just a form of a live axle, check out that thread, everything you need is there.

We used dead axels last year, and got sort of aggrivated. So this year we’re going to switch to live axels, but not in the form of hex, as we don’t have a hex broach.

As far as breaking a key… If you can break one, I’m not too sure you’re distributing your load properly…

Yeah, the advantage doesn’t come so much in not having to worry about breaking keys. It’s that you don’t have to worry about having keys. You just slide the wheel on the shaft and go.

cool thanks guys!