yes i realize that 1/4" axles wont work with the 1/2" pitch metal but at least more that a few times now we have twisted axles and have had to spend about half an hour to replace them.
the one thing i did find out is that with the high strength gears if you take out the insets 4 of the 1/8" axles will fit snugly into the axle. but the metal and bearings wont work with it.
To be honest, a lot of bent axles are not because of the strength of the materials but rather the design itself. I had a robot in Elevation where the bar was twisted into a tight corkscrew, yet it was because my robot was poorly designed. Always consider why something is happening and how you can avoid it before you take the easy way out and accuse the materials. They’re plenty strong.
I’ve twisted one, completely my fault. The only reason it will twist is if you are torquing it too much. If you can, try not to put too much stress on the axles, such as if you are using a 60 tooth or an 84 tooth gear, try bolting the gear to the piece of metal it is using. If you really want stronger axles, you can heat them with a blow torch and quickly quench them in water so harden them. They might break instead of bend or twist, however…
our design was superb and like wise for our execution the reason the axle twisted was because it is not strong enough to do the task we needed it to. What it had to do was lift a bucket to move the balls onto the other side of the court.
when the axle twisted to looked like it was laminated because of the crack that went straight down the center of the axle.
There are several ways to lift incredibly heavy objects using the Vex system - in your case, one solution is to screw the bucket straight into the gear. If that can’t be done on your current robot, then that would be the design flaw that Krummel was referring to.
I completely guarantee that Vex is not going to step up the thickness of their axle. Their axles fir the hole pattern which can essentially define Vex as being Vex. They might offer a higher strength alloy of axle but only if it was very essential, which it really isn’t at this point.
Seriously, the longer the axle the more your asking for it to bend and/or twist under strain. I strongly suggest building lifters, joins, shafts, etc. that are under 7". Most of my major joints use the 4" axle’s and I don’t have any bending issues.
If you do have a 7" - 12" shaft, MAKE SURE to used the black plastic axle aligners called flat bearings every 3" - 4" to keep the shaft strait and to push against any forces acting on the axle.
-Cody
There is no need for longer stronger axles. It seems like whenever something becomes difficult for somebody they ask vex to offer a new part when the real way to solve to problem is to design knowing that the axles are not wicked strong. Part of engineering is to design something with what you have.
~DK
Designing your tasks to working within the limits of the allowable materials is part of the problem. It sounds like your example is like bad2 below.
In general, twising off axles can be avoided by changing design such that no torque is transmitted through the axle, other than the initial motor shaft.
Examples:
Motor-axle-wheel : fine
Motor-axle-gear-gear-axle-wheel or other load: bad1
Motor-axle-gearc
Motor-axle-gear-gear-axle-gearstack-(gear_bolted_to_load) :bad2
Motor-axle-gear- gearstackbolted - gearstackbolted -
-(gear_bolted_to_load) : fine
But the reason I resurrected this thread is to point out that there are thicker axles available within the Vex system.
Use a Hex standoff as an axle, and use bolts at the ends through the bearing blocks. You may want to file off the threads of the bolt where they hit the bearin block.
Alternately, there are new shoulder bolts that might work with a bearing block, and probably work metal-on-metal without a bearing block.