A conveyor or a winch?

Before I get into today’s trivia question, just one thing I feel needs to be addressed. I’m currently sitting in the lobby (to use a flattering word for what is basically the entrance door) of the Maharaja Hotel here in Samod watching what apparently passes for cricket nowadays, the Indian Premier League. So here’s my confusion- I’ve seen approximately 20 people that are obviously of European origin during my time here in India. That’s 20 out of 1.2 billion people- a pretty small percentage. However, apparently this percentage makes up 100% of the available cheerleading stock in India- given that the only cheerleaders you ever see at the IPL games are quite obviously not of- well let’s just say Indian ancestry, at least.

So today’s trivia question is one that I’m sure has baffled many a Business Strategy Manager across this little blue planet of ours- what is the most efficient way to get 300kg of harvested worming compost from the harvesting field to a sieve that separates saleable material from rubbish or bulk material?

Firstly you may well be asking- what the hell has that question got to do with Business Strategy anyway? Well, I hopefully can put it this way- part of the strategy in this business involves producing fertilizer, and that means that someone has to answer these questions. Given the current lack of availability of fertilizer production consultants- the responsibility then has to fall on someone. That someone basically means, to a large extent, me.

Here’s your basic sieve (lovingly drawn for your appreciation in Office Impress). It takes raw harvested composted material, shakes around a bit and only passes the finer material through a metal sheet with ½ cm holes cut into it. Larger material slides along the screen and falls off the end. The sieve weighs a ton (literally) and needs the input to flow onto the highest point. We don’t know at the moment how fast we can pour material onto the sieve for to work at its most efficient, but we’re estimating something like 20kg every 2 minutes.

The problem, then, is that raw input is being harvested at a site anything from 20-150m away from where the sieve is located. The output of the sieve needs to be packed into wondrous bags of Miracle fertilizer, and that packing area needs to be static, so moving the sieve really isn’t an option. The challenge then, quite simply, is to get the material from a harvesting site that can vary to the sieve. And a constant flow of material at that to keep the sieve working at maximum capacity.

A few things had to change then. We solved the varying location by getting a little motorized tuk-tuk that can be loaded at the harvesting site before driving to the sieve. Now you might be able to see the issue- we need to get the 300kg of material from a height of about 50cm into the sieve (at a constant rate) at a height of 1.5m. Simple problem, right? So we came up with several ideas.

A ramp seems like the simplest and cheapest solution, but tuk-tuks are normally not built to take 300kg, and trying to drive one to 1.5m off the ground would mean either an infinitely long ramp ;-) or a more powerful tuk-tuk, i.e. there were serious doubts if the tuk-tuk would make it.

A conveyor would allow us to unload the tuk-tuk a little bit away from the sieve (at a point more central to where we were harvesting) and with a decent enough design would allow us to unload the harvested material by just pushing it out of the tuk-tuk and having it “flow” onto the input of the conveyor. They’re not too expensive (about $400 for 8m) and would mean a constant input flow to the sieve. The most expensive solution (intuitively) and the least flexible- although the input we can tinker with a bit.

Then it was time for the creative solution- some kind of “bin” that the tuk-tuk can easily dump material into, but that we could easily then lift up to the height of the sieve and shovel the material in. Our solution was a joint creative effort- we have a “catcher at ground height or at least with sides no higher than the tuk-tuk floor, and then we find a way of lifting it up (either by a winch system or counterweights) and then the material is pushed out or slides out when it’s at 1.5m off the ground.

Pretty cool, huh? Of course there is a little problem contained in that simple word “lifting”. How do you lift almost half a tonne of material 1.5m off the ground? Using the best of my mechanical engineering memory (i.e. practically none) we came up with a few ideas. Didn’t I learn something about pulley systems that allowed you to lift lots of weights even if you were a bit of a weakling? Couldn’t we use a balance system and a counter-weight? What about a winch- they can do pretty amazing things with relatively little engineering right?

So after trying to conceptualise how this would work in our heads, we decided we didn’t want too many 300kg counter-weights jumping up and down around where people would be constantly working with the sieve- might result in some nasty stubbed toes. The winch seemed like the natural choice- basically doing a similar ratio transfer of a pulley, but stronger and simpler to operate (those wires were going to have to be fairly large through the pulleys- probably?) But who knew about making winches to lift a half tonne “bin” off the ground? Someone in Chomu apparently, who showed us a nice little system with a simple two cog pulley driving a steel wire reel to go up, with a safety catch to stop the thing from freewheeling back down, and a brake for when the bin had been unloaded. Almost perfect. Of course then we asked him the price he wanted for this thing- which turned out to be about 3x that that we were quote for the conveyor… :-/ So all this design work, a system that wasn’t quite as good as the conveyor, but I was pretty proud of how close we got… all for the bargain price of $1200.

Back to the… well, back to the conveyor manufacturer.