Archive for June, 2011

Jari mower – working

June 20, 2011

On Sunday I finally got a chance to finish the rehab of the Jari mower that we bought off craigslist. In a previous post I described how we got it working except for the gas tank, which was rusted out. We ordered a replacement tank, but it didn’t quite fit, and in the end I found a used motor in Five Islands that had a compatible tank, so I used that one. I also had to diddle with the throttle cable to get it hooked up, since the assembly that connects the throttle cable to the governor through a spring attaches at the gas tank. I changed the oil, and it fired right up with a puff of ether in the carb.

Then I had to learn how to use it. It doesn’t have the usual safety features that come on mower these days; no dead-man switch, etc. – it will happily keep on mowing straight ahead, with or without the operator. It has one speed, and it goes at an impressive clip – you can throttle it back, but then the cutter bar doesn’t run fast enough to cut challenging grass. The drive system is such that you can’t power it forward without the cutter bar running. It can cut through small brush with no apparent struggle, and it handled an impressive thicket of tall, reedy grass amazingly well on the first pass through. Its biggest limitation became clear on subsequent passes – it is not happy about recutting grass that is already on the ground, and it is relatively easy to get into a mode where it pushes a big wad of grass ahead and mats down the material instead of cutting it. Then you have to disengage the drive, haul it backward to clear it, and raise it clear of the wad before resuming. It also binds up on really rank, fine soft grass, the kind that gets about 8″ high and then flops over. If you hold the bar higher it can shave the top off that stuff tolerably well though. The tendency for the bar to clog on fallen material from the previous pass leads to a temptation to err a bit wide of the previous swath, and I’m afraid the mowing job wasn’t as pretty as I would have liked, but it was broadly effective, and it was fast. I estimate I mowed about 2 acres in perhaps 4-5 hours – that’s a lot faster than the rotary walk-behind that we use in 5 Islands. It also leaves material that can be used as hay – though I think we were a little late of the optimum season (no critters to eat it yet, so not a big deal).

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Mowing, cheese

June 14, 2011

I finally got up to Five Islands for the first time since orchard weekend, and found the orchard completely overgrown with shoulder-high hay, with even the older trees half-buried. The orchard grass had gone bonkers, and the clover we planted last year was rank and knee-high, even taller in the two rows of spots where we put composted manure under the pumpkin hills. It is amazing the difference that a little effort seems to make in terms of the fertility of the soil – after the initial cultivation, we applied the amount of lime, phosphate rock, and greensand indicated by the soil test, and we’ve mowed a few times a year since, but basically that’s it – some of the compost etc that we’ve spread on the trees might be diffusing out between the rows, but we haven’t otherwise fertilized or amended in the orchard. At the beginning, despite correcting the macronutrients, the stand was thin and weedy, so much of the improvement must be due to the clover and vetch that we’ve planted as cover crops, and the frequent (but not too frequent) mowings.

The weather looked good Saturday AM and deteriorating thereafter, so I got right to it – I got a trailer and the small Kubota, and scooped up a load of composted chicken manure at the old homestead. I stashed the manure by the upper cabin and hooked up the four-foot Bush Hog. Mowing in the orchard was a trip – at first it was a sea of deep grass, then on the second pass a deep tunnel, and intense clouds of pollen lifted from the grass, turning the hood of the orange tractor yellow.


I also nearly mowed down a nesting hen turkey – she’s barely visible in this photo, taken from the seat of the tractor, but I mowed within 18 inches of her and she didn’t budge. Once I saw her I gave her a wide berth, leaving her a patch of grass for privacy:

Part way through the steering got really hard to turn, and I couldn’t figure out why. I went back to the barn and greased all the zerks on the front end, topped off the oil in the front axle, and filled the steering gearbox at the base of the column, which may have been dry. After that it was improved, but maybe not perfect – need to keep an eye on it so as not to do any permanent damage.

With the mowing done, I hitched up the disk, and Joanna used it to chop up the winter rye and weeds that had grown up in the strip where I failed to grow wheat and barley last year. I also hooked up the spring-tooth chisel plow (I have been calling it a spring-tooth harrow, but in looking online, the thing we’ve got looks way gnarlier than most spring-tooth harrows) to the larger tractor, since there were still a bunch of rocks and big roots, as it had been woods just 18 months before. Between us we got things pretty well turned in and smoothed out. It had started to rain by now, so rather than make things all mucky I went back to the east side and helped Dave clean out the stacks of scrap wood in the workshop. After supper it was just misting, so I borrowed a string trimmer and beat down the remaining tall grass in the rows, finishing basically at dark.

At dinner we sampled some of the goat cheese that Emily has been making, including the first wheel of aged hard cheese that she’d made, a colby:

Here’s the stash of aging cheese in their cellar:

It was raining again in the morning, so I helped Dave some more in the shop, then Emily and I spread manure in the orchard, making about 40 mounds for squash and pumpkins. Underseeding with clover seemed to work pretty well last year, so we’ll probably do that again – it would have been better if I had gotten it together to till the soil late last summer, and plant oats/clover: the oats would have nursed the clover and then winter killed, and the clover would have a beneficial head start, since it is slow to germinate. I also repaired the gate, which I caught with the corner of the tractor bucket, like a complete moron.

I had to leave Monday morning for work, and as I was going, Emily was filtering and chilling the morning’s milk, and starting another batch of cheese – this time a gouda:

rehabilitating an old Jari mower

June 10, 2011

There’s a 4′ PTO rear deck rotary mower and a 2′ walk-behind rotary mower (‘the whippah’) in Five Islands, but we need a mower for Gorham, and I’ve never been really happy with the performance of the rotary mowers – they tend to clump up and tangle the grass, making it basically not worth it to rake it up and use it for mulch. So we’ve had our eye out for a sickle bar mower, and Dave finally found a moderately old (maybe 10-20 years) Jari on craigslist, a ways upcountry. They don’t come up too often, so I took a chance and made the trip up there. The guy who advertised it wasn’t the most accurate; on the phone he said the bar was between 3 and 4 feet, while it was actually 32″, and while it was advertised ‘as is’ he said the only thing wrong with it was a broken pullcord on the engine, while in reality the cutter bar was all rusted up and the drive system was in several pieces and decidedly not functional. But all the pieces were there, and I got it for $125, so I’m not complaining (much). A new walk-behind sickle mower (new, better quality, and with swappable attachments) is well over $2000.

Anyway, I pieced the drive system back together to where I think it will work OK, tore apart and wirebrushed the cutter bar, reassembled, and lubed everything up. The only remaining problem is the fuel tank – it had supposedly been drained, but it was absolutely filthy inside with dime-sized chunks of rust. We took it off and tried brushing out the little float bowl on the underside of the top with a toothbrush, but it became obvious that it was shot – the metal was perforated so badly that it wouldn’t hold gas. Surprisingly, the pullcord mechanism just needed a bit of cleaning out and it actually worked fine, and even more amazingly it started right up with a squirt of ether in the carb. We demonstrated that the fuel feed system was working by holding a shot glass of gas under the intake tube (don’t try this at home, folks), which gave us enough confidence to go ahead and order a replacement fuel tank (which will cost about as much as the mower). It needs an oil change in a serious way, and probably some other things will rattle loose and require loctite, but hopefully we’ll have a nice tool for orchard mowing and microscale hay making.

The potential of pedal power

June 4, 2011

There have been some visitors here from an interesting article in a series on pedal power by Kris de Decker in Spain. It turns out that a significant amount of work on pedal-drive human-powered implements was done in the few decades between the invention of the bicycle and the widespread implementation of internal combustion and grid power, with another small bump during the 1970’s oil crises, and interesting demonstration projects here and there since.

We built our first pedal-powered apple grinder more or less on a lark, and we thought it was a good idea, but despite our expectations it was a real epiphany for me to see just how effective it was, and how pleasant it was to use. We went from operating a 3/4 horsepower electric garbage disposal right at the edge of its thermal limit, and cooling it (albeit in a grossly inefficient manner) with a 1 horsepower electric compressor, to a system powered by one pedaler that was much quieter, much faster, and produced nearly as fine a grind.

I think the real lesson here is less about pedal power than about the way that the availability of cheap energy and cheap goods leads to thoughtless waste, even among the well-intentioned. In cider year two, we had a pile of apples that would soon go soft, a brand new garbage disposal was 75 bucks, and the electricity to run it and the compressor cost a few pennies per hour – so we ended up using over 10x the energy we needed to do the job. The aesthetic attractiveness of pedal power mostly serves as a counter-incentive to cheap energy – ‘That would be so cool – let’s see if we can make this process efficient enough that we can power it with 100W…’ It took some engineering skill and some R&D time to figure out the right way to do it – over the next two years we fine-tuned the geometry of the grinding drum, added custom-machined post-crushers, etc. And the improvements we made are independent of the source of motive power – the same grinder assembly could easily be driven with a good quality electric motor with an efficiency of around 90%.

So once we started thinking that way, all sorts of possibilities came to mind. Right away we realized that the pressing half of the cider operation was another perfect case, where efficient application of well under 100W could do an impressive amount of practical work. Again, it took some engineering to select a suitable hydraulic pump, connect it appropriately to a bicycle drivetrain, and work out the picky details that only matter when you’re trying to be really efficient. For instance, we learned that a standard hydraulic check valve has a metal-to-metal seat, which leaks a tiny amount of oil when there’s significant back-pressure. We realized that we needed to get a check valve with a soft (o ring) seat, so that the press would hold pressure after the pedaler stopped pedaling. Normally this would not be an issue, since an engine-powered hydraulic system the engine is always running, so the pump is always working. Also, the pump would only make full pressure at a relatively high RPM, which was hard for pedalers to sustain for a long time, but with the check valve, a flywheel, and an accumulator we built out of an old dive tank, we could easily put in a short burst of vigorous pedaling and drive the system up to full pressure. The actual amount of mechanical work needed to press the cider is so modest that next year we’re going to demonstrate by hooking the press up to a junior-size bike, and let the growing crowd of kids press all 200 gallons.

Since then a whole list of promising practical applications have come to mind. High on the list is log splitting, where typically a large, loud single-cylinder gas engine runs at full-bore continuously, even though the full horsepower is only needed a tiny fraction of the time. I have a suspicion that our pedal-hydraulic power system could be hitched up almost unmodified to a log splitter with good effect, and there are probably other high force, low speed hydraulic applications as well. At the extreme end, it would be pretty sweet to see a mini excavator operating on the combined hydraulic power of five or six pedalers. Food preparation is another obvious area where a reasonable amount of work has been done, especially focused on the developing world. I’m interested to try a low-head pedal-powered irrigation pump, and possibly even a four-wheel, two station pedal-powered cultivation tractor, though the odds of any of these making it to the top of my engineering to-do-list are slim.

I guess the most obvious demonstration of the point I’m trying to make is those setups with a stationary bike where the pedaler attempts to make one or more incandescent light bulbs glow. Kris seems to go out of his way to point out that converting pedal power to electricity isn’t always the best approach; I think the discussion above should make it clear that his point is well taken here. But the futility of the pedal-light bulb demo isn’t really so much a demonstration of the limits of pedal power as it is of the lameness of incandescent bulbs – it would be interesting to do a demo with single pedaler, a well-engineered drive and generator, and an array of LEDs or compact fluorescents. I have a similar sense that a single pedaler could produce an impressive amount of audio, again given an efficient drive and a class D amplifier. And with the dramatic progress in low-power processors for mobile applications, and the availability of low-power electronic ink screens (developed by my former roommates, and used in e.g. the Kindle), pedaling could power an impressive amount of computation as well.