There’s a lot more detail on the technology of a ca. 1900 tide mill on pps 6-7 of the following newsletter: http://arrowsic.org/arrow/arrow9-08.pdf
Archive for November, 2009
A convergence of factors has had me thinking about tidal power and the history of Georgetown Island recently. First, the additional clearing for orchard expansion is opening up a vista almost from the height of land on the eastern peninsula down to the cove (at this time of year at least, when the leaves are off the trees). Though an unusual sight nowadays, open land was the rule rather than the exception in the 1800s into the early 1900s, as can be seen in the image below, sent to me by Will Ansel of Georgetown Center:
This is a photo of the Trafton Mill ca. 1900; it was located on a rock dam across the smaller west arm at the head of Robinhood Cove. A couple of posts ago I reported that Will and the students of the Georgetown elementary school are planning to build a demonstration tidal mill at the site of the former Trafton Mill, and though I knew from paddling around the remnants of the dams that these mills existed, the photo brought home to me how significant these structures were, and how recently they were in use and in apparent good repair.
As best I can tell from the photo, (at least some part of the house on the hillside is still intact, belonging to a one Dick Green whose son I went to school with) the mill building was actually located over the cove, extending from the breach upstream = to the south (presumably on wood piers, as rock supports would still be intact), with its long axis oriented with that of the cove. Of course the next question to a renewable energy engineer is, how much energy could this mill have potentially extracted?
I did a bit of modeling in order to help out Will and the kids, and now I’ve extended it to an estimate of the potential energy available in the impound above the dam. Will gives the dimensions as 1600′ long, 133′ wide, and 8′ deep. But I measure it on google maps as 1800 by an average of 320 feet. So I’ll use these numbers. Next I need a model of the cross section (since the volume of the cove is not a rectangular prism, but rather tapers significantly as it dries out on the ebb tide). Based on nothing more than recollection, I generated the model below:
I think if anything this under-estimates the volume of the impound (ie. the slope is initially steeper, and the mudflats are relatively flatter) – keep in mind that the scale is off by about a factor of 10.
I converted to SI units and calculated the potential energy of the water in the impound, in sixteen vertical slices. The number that results is approximately 1.4GJ, or about 390 kWh – about the energy content of 10 gallons of gas. Of course, a primitive tide mill probably isn’t going to extract more than about 30% of the potential energy that’s available, on the other hand, 30% is probably a generous estimate for the thermodynamic equivalent of a 10hp gas engine as well. The amount of energy in the impound could be considered impressive or pathetic, depending on how you think about it. On the one hand, the Trafton Mill would surely be a million-plus dollar facility if built today (by any but the most crafty scavenging hackers), and accesses an energy stream worth at most $35 per day (assuming 30% conversion, 2 tides a day, 15 cent electricity) – that’s a measly ~1% simple gross annual return on capital.
But in historical context, by the standards of the day, the energy stream corresponds to 289 man-days of human labor per day (assuming 30% conversion, 2 tides a day, 100W useful human effort 8 hours a day). In a time when the alternative was human or animal labor, a tide mill accessing the equivalent of 300 laborers would be a pretty sweet thing to have. And I recall from working on old houses around town as a kid, there were quite a lot of boards in them with the coarse linear saw marks characteristic of the sort of gang saw that would likely have been used in such a mill.
An episode of On Point on NPR caught my ear the other evening, inspired by a piece in the WSJ about the resurgence of tinkering in the US. The stories highlighted people using increasingly accessible fabrication technology to design and make tangible stuff, and featured Makerbot, a FDM-based tabletop rapid prototyping machine designed by and marketed to hacker types. Ashbrook focused on the question of whether this perceived increase in tinkering is basically just a human interest story, or whether the growing ranks of garage tinkerers might hold the key to getting the US economy out of the ditch.
The discussion glossed over some important distinctions which I think ought to be understood, especially relating to the idea that rapid prototyping machines can “make just about anything”, and that with this technology you can design and manufacture whatever you want. I spent a few years in the MIT lab that invented 3D printing, and I have worked my entire career for companies that manufactured stuff or were attempting to manufacture stuff, so I have some background in this area. The basic fact is that in most fields of engineeering there is a chasm of difficulty and effort at least two orders of magnitude wide that separates designing and prototyping some device, and developing volume-manufactured goods that can be sold at a profit sufficient to pay back the capital investment and keep the operation afloat. Three-dimensional printing (and other related SFF techniques) are brilliant for making look-and-feel prototypes and reasonable short-term approximations to molded plastic components, but they are universally too slow, too expensive, and too limited in the palate of workable materials to be competitive for manufacturing. At the MIT lab, one of the smartest engineers I know struggled for 10 years to find some angle by which 3DP could get beyond Rapid Prototyping applications, and out of the half-dozen startup companies that came out of the lab, the only one that ever attained any kind of escape velocity was Zcorp, the one focused on RP. The closest 3DP came to manufacturing was the use of a Zcorp machine to print a complex plaster mold, which could in turn be used to pour aluminum castings, theoretically cheaper than the cost of alternative approaches. This product was on the market at least for a while, and I think it could actually be a viable, but as I understand the effort stalled due to lack of vision on the part of the team attempting to execute it and the sclerotic nature of the casting industry.
The basic theme here is not just that SFF is effectively limited to prototypes and hacking (for which it is admirably suited, and by appearance the Makerbot is a brilliant achievement), nor that displacing established manufacturing technologies is hard to do. More generally the point is that real product development and manufacturing is genuinely difficult, and not nearly so well suited to dorm-room tinkering. The reasons are fairly fundamental. Modern manufacturing has developed in a very competitive environment and benefited greatly from economies of scale; the basic techniques (such as injection molding, metal stamping, etc) are dramatically more cost effective and flexible than SFF, CNC machining, laser cutting, or other prototyping techniques, but they require massive machines costing hundreds of thousands of dollars, and part-specific tooling costing tens of thousands of dollars.
Another basic issue is that many of the hacker types I know have a certain artistic bent, such that the stuff they make, while incredibly impressive and cool, often tends towards the expressive and offbeat, rather than having an end-user product focus. Take for example the ubiquitous LED lighting projects, or the 10-foot long pair of wooden vice-grips, built for fun by my roommates when we lived in a warehouse in Central Square. Some might even claim that pedal-powered cidering equipment falls in this category;-)
It could be fairly argued that I’m picking nits here; and I want to emphasize that the physical hacking trend is really awesome, it combines some of the most admirable human traits of creativity, resourcefulness, innovation, and the noble calling of salvaging and repurposing cast-off technology. It gives people something to do that is active, engaging, and social, much more interesting than drinking beer and watching TV. If industrial society ever collapses, this kind of ingenuity and hacking (which has been going on continuously under the radar in farm country all along) will become immensely more important. And I do believe that the cost of doing real manufacturing is coming down and speeds increasing, probably mostly due to overseas competition – witness the rise of rapid low cost injection molding suppliers (where low cost is in the $3-10k range). But the engineering that interests me most is the development of technology that enables the provisioning of basic human needs (food, shelter, heat, light, transportation, information) in a more energy efficient and environmentally friendly way. And those areas seem to be the ones where competition, technology, and the economies of scale have been working hardest and longest. To make a real impact requires scale, scale requires cost-competitiveness, and cost competitiveness requires all the tools that engineering brings to bear – which these days far exceed the capabilities of even the coolest CNC router, Arduino, and 3D printer.
A talented boatbuilder of my acquaintance who lives at the head of Robinhood Cove is working with the kids in the local school to build a demonstration floating tidal mill at the site of the historic Trafton Mill, just a few hundred yards from the school. The plan involves hobie cat hulls procured for a different (but similarly unique) project by Keith Richtman; that project was postponed indefinitely and the hulls ended up in my parents’ yard, but now they are going to good use. This is a neat idea and a great educational opportunity, and I’ve attached the concept sketches so that the renewable energy engineers in the audience might provide some input. Will Ansel tide mill docs I did some quick calcs to get them started – just 50W mechanical at full flood – plenty of opportunity for optimization.
Alexis was stuck tending to the ICU all weekend, so I dropped her off at 6AM Saturday and headed down east. I arrived around 9A, and with rain forecast for the afternoon I quickly geared up – boots, chaps, helmet, fluorescent vest (hunting season) – and headed for the orchard. The goal is to add two more rows of apples to the west, merging the orchard with the pasture below. I started by clearing a bunch of scrubby growth, then Joshua and Kelsey came to lend a hand and with help of the rope-a-long felled three crooked white pines. Long about noon it started to drizzle so we packed up gear and headed for the other side, where we had some lunch and spent the afternoon talking renewable energy and catching up. My folks went off to dinner with some friends, we cooked some grub and played some tunes, then Kauf and Kelsey headed home to their new place in Portland.
The next morning it had stopped raining but was still foggy and damp, so I went over to the other side and racked the 6 carboys, consolidating into five substantially fuller ones. All but one or two were at 1.004 or so, so they should start settling pretty soon. The one that didn’t get sulfite was still at 1.02 or so; it didn’t seem to go off so fast, perhaps because it was a different mix of apples, or maybe there was some kind of competition from the natives. Round about 10:30 that was done, and I headed for the woods, joined by the folks. Between a short stint before lunch and a longer one after, we spent the daylight, and got about half the necessary clearing done. We stacked the brush in windrows to be chipped in the spring, and left the trunks to be sorted out with the excavator when the ground dries out or freezes – much too wet in the woods for machinery after 2.5″ of rain.
In addition to clearing and cider processing, I hatched a tentative scheme to build a treehouse in a very large branching red oak tree near the orchard, in a spot which would overlook the trees of the orchard to the east and down over the fields towards the cove to the west. The other big news is that my sister is moving east in December; she and the kids are going to take up residence in the old homestead and bring some youthful energy to the North End – I’m very excited to have her back on the east coast. On my way home I stopped for a fine dinner with Kauf and Kelsey and checked out their new place. All in all a busy and productive weekend.
With cider season wound down, I’ve got more time for playing fiddle, and I’ve been learning some new music, so I thought I’d write a post about resources for learning tunes. The stuff I play is a mixed bag centered roughly around traditional New England dance music, which has Irish, Scots, Quebec, Cape Breton, and Appalachian influences. I started off learning by ear, but I’ve gradually gotten better at decoding “dots” and learning tunes from books, to the point where learning from written music feels like cheating – learning by ear is generally considered by hardcore trad music types to be a superior way to internalize music. Anyway, here are some books that I consult regularly:
- The Portland Collection #1 and #2 – a huge amount of contradance music in two volumes, with comments, versions are reliable for the most part, except old time players snark about the settings of old time tunes
- Fiddler’s Fakebook – lots of tunes from various traditions. Over half of the time a tune I’m looking for will be in this or one of the Portland books.
- Waltz books, #1,2,3 – all waltzes, all the time.
- New England Fiddler’s Repertoire – “NEFR” thin book, lots of good tunes, mostly older I think.
- Along the River – Collection of tunes from w. MA and s. VT; I don’t use it much
- Jerry Holland’s Collection, volumes 1 and 2 – not just Jerry Holland’s (recently departed) compositions, a lot of music that’s played up Cape Breton way; good stuff
- Appalachian Fiddle, Miles Krassen – includes helpful material on learning, chording and double stops, 58 tunes.
- Beginning Old Time Fiddle, Alan Kaufman – also has useful intro material, 38 tunes
At least as useful as books are online tune collections:
- thesession.org – extensive collection of mostly celtic tunes (dots, ABC, MIDI), with active and useful discussion
- http://www.mustrad.udenap.org/lerepertoire.html – an extensive collection of French-Canadian tunes (dots, also plays MIDI I think)
Accessing and modifying tunes digitally is fairly straightforward nowadays thanks to the abc format, which is pretty much what it sounds like – there’s a header that describes the type of tune, key signature, etc., then you type letters (and other characters to indicate timing), and software (for instance freeware ABCexplorer) converts it into nicely formatted sheet music, and plays a sterile but recognizable midi version back to you. Using these tools, I transcribed my first tune, Cracked Pot by Maine fiddler Greg Boardman, and put it up on thesession (see http://www.thesession.org/tunes/display/10016 )
As for learning by ear, I recently shelled out $50 for The Amazing Slow Downer, a piece of software that processes mp3s and other music files, to change the tempo without changing the pitch; this is really handy for trying to decode what musicians are doing on fast-paced recordings.
YouTube is great for finding recordings (widely varying in quality of course) of a new tune I’m trying to pick up. Pandora.com and last.fm have fragmentary but useful collections of traditional celt stuff, which is great for picking up new tunes, and I’m told that Rhapsody is pretty good, but haven’t gone that route.
Between all these resources and tools, the only thing keeping me from improving on the fiddle is time!
I hope that readers accustomed to the usual apple, ag, and energy-themed material will excuse a bit of indignant ranting social criticism. The 2009 cider madness was made possible by the generosity of a guy I scarcely knew at the time, a friend of a friend who lent us a tandem bike to power the grinder. It worked beautifully, grinding apples at an unprecedented rate and adding significantly to the social aspect of the cidering. What with busy schedules we’re only now arranging to get the tandem back to him. I hadn’t ever actually ridden a tandem on the road before, and it seemed only proper to make sure it was in good working order before returning it, so Holly and I hatched a plan to take it out to work one day, about a 12 mile ride.
Today was the day, and I am pleased to report that riding a tandem bike is very efficient and a lot of fun. The dynamics are a bit wobbly getting started, but once under way it smooths out and the inherent efficiency of double the power for the same amount of wind resistance becomes readily apparent, especially to the rider in front – it’s possible to go much faster with the same or less effort as compared to solo biking. And the social aspect of having a conversation going all the while makes the miles fly by. All in all a very cool piece of technology, and despite the inherent logistical issues definitely worth considering for serious bike commuting.
Now on to the rant part – what didn’t occur to either of us, but seems to occur to everyone else we talked to, is the assumption that two guys on a tandem bike must necessarily be homosexuals. It’s not as if anyone was actually rude to us or hecked or anything; this is Massachusetts after all, America’s own Gomorrah, but the guys at the gas station where we met up were clearly having a good time with the concept, and we passed by a young mother with two young children who smiled as if to say “aren’t we so progressive here in Cambridge” and pointed us out to the kids. Even at the place we work, which is an MIT solar cell startup company no less, not exactly a bastion of redneckedness, folks had the same impression – “I expect to see a guy and a girl on a tandem, or maybe two women who are really close friends. But two guys on a tandem – that’s gay.”
This brought back distant memories; as it turns out both Holly and I were the sort of kids who got called gay with some regularity back in high school, not because of anything specifically gay that we did, more probably because that’s just what kids at least in rural high schools say to taunt the nerdy kids who are even moderately intelligent, thoughtful, or quirky. And it’s genuinely easy to laugh about it now, having long since absolved ourselves in the nerd-heaven that is MIT, and having been married to our wives well over a decade between us. But I find myself shaking my head at the whole concept – isn’t this the 21st century? What is so gay about two guys on a tandem bicycle? I mean, football players dress up in skin-tight pants, line up, and bend over for the purpose of passing a hunk of leather between one anothers’ legs, and nobody is calling them gay. You aren’t even touching the other rider on a tandem bike. Are most guys so laden with leftover teenage trauma that they wouldn’t ride a tandem with another guy, so as not to risk getting verbally assaulted (or worse)? It can’t be that full-grown guys are actually that insecure in their sexuality – it must be more of a reflexive thing. And so what if there were two gay guys on a tandem bike? This is 2009 in New England, where last I knew all six states allow gay marriage (fingers crossed for my home state of Maine this election night). How are we ever going to arrive at an enlightened understanding of gender if two guys can’t ride the same tandem bicycle without folks sniggering? It puts me in mind of accounts from the time of Abe Lincoln, when it was apparently common for two (or more) men to share a bed without any implication of sodomy. So, gentlemen, if guys in 1850 could manage that, surely we can manage tandem bicyclery.