Monday, March 12, 2012

straw chopper pt. 2

Despite all of the stuff i put in my mouth I didn't die, or have to go to the hospital. And coming at it a week later, having learned my lesson, i did a little more snooping to figure out draining the gas. And, oh, what do you know, there's a fuel line that can be pulled out.

I propped the thing up on some bricks and drained the gas. I kept it in a container, knowing from my experience at maya pedal that i could use it as a de-greaser. Freeeee materials. Free cancer-causing materials.



I took the hoppers of the chipper for mobility and to get a closer look at what was running inside.


Right in the center, those are some blades. Actually, they are they only blades. I didn't know this. I assumed there were more, there had to be more. Those blades look kind of insufficient for chopping up lawn detritus, especially in large quantities.

The cover didn't want to come off though. Everything but one nut. One stupid nut. Crescent wrench wasn't doing the trick, so i opted for a trick i learned from Carlos. Weld a long piece of metal, to act as a lever, to the stubborn nut.


It took a fair amount of leverage to get it off, but it got there.



This was the moment where i found out there were no more blades. Just some rusty metal for bludgeoning things apart. This didn't bode well, but i kept going.


On the bottom end you can see the pull start, the black plastic part with the vents on it. I knew i had to get that thing off, whatever was inside was going to be my best shot at attaching it to a bike.


The cord for the start had been wrapped around the brass colored cup, or maybe around something that attached to the cup. In any event, the cup needed to come off, if i was going to attach a chainring or pulley to it. Besides, that nut in the middle might help me attach whatever was to come.


And though not rusted, this one was unusually hard to get off as well. No wrench could fit it there, too deep. Another maya pedal lesson- don't have a tool? make one.


Before attaching anything to the drive side, i decided to set it up in the vise and see what spinning it around might do, if anything.



video


Uh, yeah. Not much.


Okay, so what if goes faster? Of course, that was the plan all along, to use legs via a bike, get going fast and hope it chopped some shit up. My first thought was to attach a chain ring to that big metal wheel-thing where the pull cord had once been. Imaging that it would look something like this:


However, my attempt to weld the chain ring onto the bike directly didn't work. Dissimilar metal? Aluminum perhaps? Not sure.



Okay, so something else would have to happen. How about i bolt the chain ring on? I liked it. But the surface of the wheel with all those weird fins (who knows what the hell they were for anyway) wasn't going to work well. So i found a piece of thick plate metal, drew a circle on it and cut it out. I welded it to the chipper, and though not great, it stuck. I played with some angles and drew out where to attach bolts (i think its pretty funny it came out as a pentagram). Bolts on, now time for the chain ring.


Got a chain between the bike and the chipper. Now the moment of truth. Or, the moment in which i see what happens. Its true either way. Why do people say that? Its probably more accurate to say "now the moment of i get what i want."


I didn't get what i wanted, but i saw what happened. The gearing was terrible. Practically 1:1- which means lots of pedaling for almost nothing happening. No straw being chopped. Nothing.

Change the gear ratio? (Again, thinking, faster! It just needs to be faster). So i tried a compound gear train like i had with the flour mill. I didn't bother to calculate anything this time, i just needed to know if faster equaled functioning. Got it in the highest gear using a bike wheel to intermediate.


Second moment of 'will i get what i want?' And... no. Faster, yes. Chopping straw, no.

Okay, so what if it goes even faster? The fastest i can possibly make it go with my tenth of a horsepower speed legs?

To get that kind of gear ratio, i'd have to try something other than bike chain. Too much work to set up more gears, it would just get crazy. A belt would be the best option. Where would i find a belt? To the scrap pile.


I don't remember if i found this drier in the pile, or if it was one that i procured from the outside world (i think from the outside world) (eventually i ended up with like 10 of them, but i'll get to that later), but it was pretty much what i was looking for. High tension belt, pulleys, perfect.


I knew that i could use the high tension belt like this:


And considering how small the driven pulley was, the gear ratio would be immense. The speed, incredibly fast. Bolstered by this timely discovery, i began experimenting with how to attach the pulley to the chipper.


It was too short. Even if i took the chainring off, the bolts would be in the way of the belt. It seemed wiser to leave them on there, they may come in handy later.

I'd need to take apart the motor to get the shaft out that the pulley attached to. It was glued together with some kind of industrial epoxy. No screws, no bolts, no zippers. That meant one thing, cut it apart with the giant angle grinder.

(when the disc from the chop saw got too small to cut anything i'd take it off and use it on the angle grinder- dangerous? check. thrifty and also kind of fun? check.)


Once i had it down to the piece that i needed i was ready to try to weld it on to the plate. I knew it had to be centered, but eyeballing it didn't seem adequate. Unlike the bolts and the chainring, there would be no wiggle room here, it had to go on right the first time.

When i put the plate on i made sure to drill a hole in the middle to line up with the central bolt (that the cup was attached to) for centering purposes. It came in very handy for this next part of the process.


I would need a compass of sorts. But i had no compass. Nor anything remotely close to a compass. Mmm, okay, got it.

Found some fraying plastic rope, took apart the strands, tied a pencil to a star bit screwdriver, and voila, compass.


But that didn't work so well. The circle, though it looks okay in the picture, was pretty wobbly. I needed precision. Thousandths of an inch. Computer numerical control.

I had none of these.



What i did have, though, was an excess of wood offcuts. I took a small piece of dimensional lumber, measured the diameter of the base of the pulley apparatus, and then drilled two holes the distance of the radius. Pretty close to CNC.


It definitely worked a lot better. I got a stable, clear and, relatively, accurate circle.


Set the pulley up on it, lined up nice, welded it on. (In hindsight i didn't consider whether the base of the pulley was actually going to weld to the plate, after all that it might not have, but luckily it did.)


Then came the moment, i mean, another moment of maybe get what i want.


So all set up, got it in place, stood on the pedals- cause there's no seat- and the belt spun in place. Too fast. So fast it wouldn't go, or do anything. Not with my legs. Not without a tensioner (didn't know this then). If none of this is making sense to you, i'll explain, the more drastic the ratio between the driven gear (pulley) and the driving gear (cranks, but effectively the bike wheel) the faster the driven gear spins and the harder the driving gear is to operate. Effectively i set up a gear ratio so extreme that it was impossible for me to actually move the thing. This is where variable gearing helps, get it started in low, work up to high until you max out. Not an option here though. The chain was on the lowest gear of the cogsette on the wheel. Smaller wheel might have done it. Smaller wheel with a tensioner might have worked great, but only at getting speed. Frankly, at this point it was painfully obvious that the chipper was not the right machine. It was too heavy, and it wasn't based on cutting finely, with sharp blades. No, it was based on brute force, on smashing sticks around until they broke and then forcing them through a small hole with blades in the way. Even with gasoline in it, even with all those horses working away, it might not have even shredded straw. I had a sneaking suspicion from the start, but it was what i was given to work with. And it wasn't going to work.

But that didn't mean i was going to give up.