Archive for December, 2011

no cheeseburger for you

December 11, 2011

Via Paul Krugman’s blog, a post explaining why you really couldn’t has cheezburger before the days of modern food technology.

Meanwhile, today was the Great Stroudwater Pumpkin Massacre of 2011. The pumpkins we harvested have been sitting in the link room since October, and some of them were starting to get soft spots, so I hacked up enough to stuff Kelsey’s big pressure canner, and cooked them down. It ended up making about six quarts, the majority of which went in the freezer. However, I’ve decided that butternut squash is basically in every way superior to pumpkin, so I’m going to advocate for a much higher ratio of those next summer.

Design drawing for post-crusher

December 4, 2011

Some folks have asked for more design details on the post-crushers we use in our pedal grinder. I’ve put a link to a PDF drawing under “Cider Equipment Plans” over on the right. If anybody wants actual CAD files, email me at firstinitiallastname at gmail.

The concept is basically that you want two drums with shallow ‘teeth’ that are deep enough to engage the apple pulp and draw it through, but not so deep as to get clogged up. We were constrained in designing the tooth shape by the cutters that were available at local stores (in the end we used a router bit that we found at Sears), but we played around a bit until we found something that made a decent interlocking shallow tooth. It’s not perfect, it’s not an involute, and you have to be careful that the shapes have clearance when the tooth is lined up directly with the slot on the mating drum, but also that they pass clearly into and out of that point – the ‘gearing mate’ feature in solidworks was handy if I remember correctly.

As to the fabrication process, IIRC it went something like this: UHMW Polyethylene round stock; it routinely comes larger than advertised, so 5″ should be fine – at least from McMaster. We bought a 12″ chunk and cut it into 2 pieces. Chucked it in the lathe with a 3-jaw chuck, and drilled it through at 3/4″ – may have reamed it too, if we were feeling anal. Then we broached it to 3/4″ hex. That hex broach will cost real money new, but Holly has managed to find decent used ones on Ebay for about $75. We then pressed in some pre-made shafts of 3/4″ stainless hex bar with the ends turned down to 5/8″ round. We’ve gotten lucky 2 out of 3 times with the hex bar coming in a little over dimension, so it makes a nice press fit. But it occurs to me that if you heated the PE rounds to above 50c or so in a water bath before broaching, it would probably broach like butter and shrink down to make a nice press fit even if the hex bar was at nominal dimension.

It could be argued that we gild the lily a bit by using stainless hex bar for our shafts; our philosophy has been that we’re building stuff that’s going to last the rest of our lives, and we want the core of it to be rock-solid. And the time we’ve invested making it is substantial enough that spending a few hundred dollars on good materials seems warranted – hell, some people spend way more than that on bicycles or HiFi equipement. Anyway, once the PE was pressed on the hex shafts, we put one end in a 5/8 collet and the other end in a live center, and turned the OD to dimension (5″) – I bet we cleaned up the ends and took them down to length as well.

The fussiest part of the whole thing was getting the setup on the mill to cut the teeth on the drums. We used a manual rotary table, propped upright on the mill table so its axis of rotation was horizontal and along the long dimension of the mill table. The rotary table came with a tailstock, IIRC, and we had to fuss around with the test indicator for a while to get the shaft parallel to the X axis and to the mill table. Then we cut the grooves; I think we did a roughing pass all around, then once again with a finishing pass. The surface finish was acceptable, but not fantastic, as it was a cheap carbide router bit running at less than 2000 RPM. A little roughness is OK, but you want to try for decent finish, cuz UHMW is hard to sand smooth.

I recall we fiddled with the groove dimensions in Solidworks once we had them rough cut on the machine; it’s likely that the woodworking bits aren’t super precise to the dimensions that they seem to be made to (it’s rare that a hardware store router bit comes with an actual dimensioned drawing; for instance, is a core box bit really actually hemispheric? Anyway, the dimensions shown will work, and other dimensions could be made to work, so long as you lay it out in CAD ahead of time and make sure it gives a nice uniform crush everywhere on the tooth profile. Here’s a screenshot of the profile we designed:

There are a couple more details to the setup that are important. The (cheap, lubed-for-short-life) pillow block bearings we use are from McM; they mount to T slot extrusion on either side so it’s easy to adjust distances etc to get clearances and chain tension right. To set up the post crushers, we basically fix one drum and then slide the other drum up until it touches, then tap it the minimum distance back to get some clearance – well under 1mm is OK; apple seeds, stems, and other hard stuff seem to feed through by elastically deforming the polyethylene or springing the shafts a bit – you really don’t want anything hard that’s much bigger than an apple stem to feed through there though, or it will put a big gouge in the drums (or worse).

The chain drive is not shown in the images, but we drive the primary cutter drum and the left-hand post-crusher at the same speed from the same piece of bike chain. As mentioned above, the left crusher drum won’t drive the right one passively; it will make a horrible chunking noise if you try. So we use a separate piece of light 25 pitch chain to keep them in time – there are photos on the blog that show how this looks. On one of the drums the sprockets are keyed to the shaft, but on the other it’s just set screws, since you need to be able to manually set the phase of the one drum to the other and then lock it down. It works fine until the set screws vibrate loose; better would be a keyed flange bushing on the driven crusher’s shaft, with a circular slot arrangement that would allow greater precision and strength for locking in the phase.

Alternatively, if someone comes up with a more sophisticated (but still fabricatable) crusher shape that does self-drive, that would be brilliant. We designed the shape we use basically on intuition and what cutters we could find, and we pretty much just got lucky – I’m not sure how many more times we would have tried, since it was a couple late nights in the shop to make the first set. It’s possible that a proper involute with substantially deeper teeth would still work and still fling the pulp out of the grooves, so long as you were spinning fast enough. Sadly, few enough people have access to even a bridgeport; I don’t expect many folks can do their own proper gear hobbing.


December 4, 2011

Jeff and Ellen sent an email the other day alerting us to a concert at the Portland high school of a unique musical group called Childsplay. It’s a big group of musicians who all (the fiddlers and violists, anyway) play instruments made by one guy – Bob Childs, formerly of Maine, now in Cambridge MA. There were some familiar faces, including Lissa Schneckenberger, Keith Murphy, and Hanneke Cassel, and a bunch of other great musicians I didn’t know. I’ve been pretty busy and not fiddling much, so it’s good to see a show and get some inspiration to play more.

Beautiful hydraulic tie-bar press by Lockehaven Farm

December 1, 2011

Some folks up in our old neighborhood have taken up the homebrew cider equipment torch, and produced a very attractive hydraulic tie-bar press made of hickory:

They then proceeded to make two bins(!) worth of cider using a hand-crank grinder – that is serious work! These folks obviously have the skills to build stuff, so I would imagine they’re thinking about new grinding equipment for next year.

They were powering the hydraulic press From a small tractor, and from their blog entry it sounds like they had some trouble with the fabric, and with the racks they used. I’m just speculating, but I suspect that these could be related. They started out using canvas, which sounds like it blew out, so then they switched to jersey (which is much weaker I think) – maybe they can clarify in the comments. Based on our experience, canvas should work OK if you’re careful. We use the heaviest muslin we could buy at the fabric store in West Lebanon, just north of I89 – it sounds like that same fabric store was flooded out by Irene. I think the material is sometimes called ‘drill’, but it feels just like a fine canvas. It occurs to me that Home Despot used to sell natural canvas drop cloths that might do in a pinch, though I doubt the material is very good quality, and I’d wash it a couple times in hot water, since it’s surely not food grade.

Anyway, even with the heaviest cotton fabric we could find, we have had blowouts when we applied pressure too quickly. The trick is to bring the ram down VERY slowly once the pressure starts to build. The hydraulic presses are capable of delivering between 50 and 100 PSI to the stack itself, and if the pomace is still liquid-y when you get up to pressure, or if the radius of curvature of the fabric isn’t good and tight, it will burst right through. This makes perfect sense from a mechanical engineering perspective in terms of hoop stress in pressure vessels, but it makes intuitive sense once you’ve seen the pomace streaming out through a bulging hernia in the fabric. You need to gradually ramp up the pressure so the partially-exhausted pomace helps form bridges between the gaps in the grates; then you can really hit it with pressure – we go up to ~2500psi on the 4″ cylinder, but not until the stack is nicely consolidated. Even then, our fabric has been in use several years and we’ve had a few ruptures, so now we use 2 layers just to be safe – the yield is not noticeably affected.

It sounds like the Lockehaven folks are going to try making grates with 1/4″ plastic next year; I would caution that the fabric is pretty good at poofing out and filling shallow gaps. Our grates are made of 3/4″ by 1.375″ slats with gaps about 5/8″ wide between them, and I wouldn’t want much less than the 3/4″ for cider to flow through. Some of our grates are made of basswood (much softer than hard maple) and others are red maple (also somewhat softer) and we’ve used them a few years now, so I suspect the issues they were having might have been related to too much speed.

Anyway, I’m glad to see other folks home-building serious cider equipment – nice work, guys!

PS. it looked like they might have been aiming to ferment some of the mac/cortland cider. I suspect that a lot of folks get into the situation where they want to make hard cider but can’t get decent tart or bittersweet apples. We had the issue last year where we bought a bin of Dabinet from Poverty Lane, but we couldn’t get any tart apples (due to the widespread frost), so we ended up with several tanks of seriously unbalanced cider. Steve Wood would probably swoon if he heard we were adulterating our brew, but Holly discovered that 3g of malic acid from the brew store took our cider from way-overbitter to pleasantly tart. 1.5g per liter was more to my taste, so that’s how we bottled some of our 2010 stuff. Better Living Through Chemistry, as Jillian Cooke would say – not everybody has the luxury of 100 acres of fruit to pick from in blending their cider. This year, Steve couldn’t sell us any bittersweets – the brew store also sells tannin; we haven’t tried that though.


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