So I don't play softball in any capacity. My hand eye coordination is just about good enough to get my hands on the keyboard (mostly), so swinging a bat at a fast moving object is impossible. But a good friend of mine who does play commissioned a project from me, to build a softball bat roller.
I had never heard of rolling softball bats before this. So I did a bunch of research.
With composite softball bats, what happens is every time you hit a ball with reasonable force, a small compression point occurs on the bat, breaking up the epoxy and crushing the fibers; thereby changing its elasticity. Once that occurs, if you hit a ball on the exact same spot, it is said that the ball can travel further than before, due to the elasticity change.
So basically it can be said that a composite softball bat gets better with age. I've read that a bat with 500+ hits can send softballs 40-50 feet further than brand new bats!
But who wants to hit a ball 500 times to get a juiced up bat??
So there is value in a machine that can speed up the aging process of composite bats, and replicate the numerous impacts required for a juiced bat. That's where bat rollers come in. The idea is to squeeze the bat shaft between two or more rollers that emulate the ball impact/compression. You then roll the bat around to try and get an even distribution of said compression along it's hitting surface.
I researched a fair bit about this subject before diving in to the design process. I wanted to see what kinds of rollers people were using, were they using bearings, what forces were they using, etc. I will try and detail as much as I can here, so if anyone else wants to build their own bat roller they will have a good starting point.
Here's some design characteristics I found:
Rollers
►Should be rigid enough to not bow or flex during rolling
►Generally made of nylon of some sort, with a steel shaft core
►Metal rollers may damage a bat too much, or mar the surface finish
►Should only have 6 to 7 inches of contact with the bat when rolling parallel to the bat
Rolling Technique
►You can roll parallel or perpendicular to the bat barrel
►There is not a standard rolling force, and it can vary between bats
►Most bat rollers you tighten by feel in 90° turns of your clamping handle
►Don't roll within 2" of the bat tip, as you may damage the end cap
There seems to be a lot more art than science in rolling these bats, as a lot of it is done by feel and experience.
Since I was on a budget for this build, I kept everything as simple as possible, while still retaining full assembly/disassembly privileges and a reasonable strong construction. I opted to use oil impregnated bronze bushings instead of ball bearings for the rollers due to cost constraints, and they still roll pretty well due to generous tolerances.
Everything else I burned out on the plasma table at work and welded together, with a few bolts here and there to allow disassembly (I wasn't banking on it working first try, and it didn't). The rollers are press fit and pinned to the steel shafts so they don't spin independently.
My friend wanted to paint it himself, so I just left it with a sandblast finish.
There's not much else to say about this build, but it was a fun little side project and I got paid to do it. These are a little expensive to buy online, but they are relatively simple to make without too many fancy tools, so if you are interested and handy, this might be a project for you.
Thanks for reading!
