Tuesday, December 08, 2020

Gin Is Unforgiving

Hmm. That came out wrong. I should have said, "A cotton gin is unforgiving." Oh well. As Pontius Pilate said, "What I have written, I have written." On with the show.

A cotton gin is a pretty simple device. You press two rollers together and counter rotate them. They grab the lint, take it through the rollers and squish out the seed. It turns out that the rollers need to spin freely and the gears need to keep the rollers together. When I built the Catican Gin Mark I this weekend, I figured that was a pretty forgiving process, so I didn't drag out my miter saw to cut the wood accurately. I also made the wooden gears too tight.

The end result was bound rollers and lopsided gears. Meh. The thing turned and all, but it turned all wobbly like and the friction on the rollers was such that the handle, screwed onto one of the rollers, started to rip its screws out of the wood. 

I tore it apart and began the Catican Gin Mark II yesterday. I used my miter saw and the frame now allows the rollers to spin nicely while holding them in place. I saw why the gears only sort of meshed and as soon as time allows, I'll cut new ones, this time with deeper voids and pointier teeth. Think of a gator's mouth and you'll get the idea.

In any case, here is a photo tour of the first version. Enjoy!

I designed the gears using this web app. I made them so their contact circles were a hair shy of 2" in diameter. That wasn't enough because my construction methods were so crude. The web app did a decent job designing them, but I had to use Photoshop to make sure the scaling was accurate.

Taking tips from a YouTube video about making gears, I used a drill to make the voids and a skill saw to make the teeth. Again, the process was too crude for the tolerances I had designed.

I dunno, Jethro. It sure looks like they're gonna work!

I was smart enough to know that the gears needed to be mounted pretty close to dead center on the rods. Using photoshop and a jpg of graph paper, I made a 2" diameter paper circle and that was my targeting system for drilling.

The Catican Gin Mark I, gear side. The turnbuckle was my own improvement to a design I saw a while back. Memo to self: get a hefty pair of cutters that can go through cable. Chewing your way through them with wire cutters is a drag.

The Catican Gin, Mark I, handle side. It was coming up on dinner time, so I just grabbed a piece of plywood and screwed it onto the top roller to try out the gin. By this time, I knew it wouldn't work properly, but I couldn't resist playing with it. The rollers spun and the gears did their work, but they were so lopsided and off-center that the rollers wobbled all over the place. The gap between the rollers didn't stay constant at all. When I tightened the turnbuckle, the handle's screws began to rip out of the roller.

I went inside and had some of wife kitteh's delicious Chicken Cacciatore.

So there you have it. A first stab at a cotton gin. The second version is well started. I should be able to finish it with ease by Saturday afternoon at the latest.


tim eisele said...

Cool! The whole point of a prototype is to fail in instructive ways, and it sounds like this one is doing its job.

K T Cat said...

Indeed. The first version teaches you about materials and methods.

Foxfier said...

Making my hands itch to try building stuff again. :D