Combines for the Small Farm

The Allis-Chalmers All Crop Harvester series combines are an example of the PTO-driven tow-behind combines manufactured in great profusion between the mid-1930s and the early 1960s. These combines were a very effective tool for family-sized farms, since they didn't require the investment or maintenance of a self-propelled unit. The A-C offering was particularly flexible, able to harvest various small grains and everything from flowers to various grass and legume crops for seed. Regrettably, hardly anyone in mainstream American farming has that sort of need anymore - hybrid seed comes from the big agribiz companies, and if you aren't growing grain by the thousands of bushels, nobody understands why you bother.

Allis-Chalmers Model 66 All Crop Harvester

Because of their flexibility, the mid-sized A-C All-Crop Harvesters were quite popular. The first combines shipped under that name in 1936, with a 60 inch sickle-bar and cylinder, and a cross-wise separator behind the cylinder. Later enhancements included a 66 inch cutting width, better grain handling, larger bins, etc. The All-Crop Harvesters had the cutter bar, reel and cylinder on their right side , and the grain bin and unloading auger on their left side . The basic model was PTO-powered, but a 4-cylinder gas power unit could be mounted on the tongue.

By the time the Model 72 replaced the 66 in 1960, about 300,000 had been built. The only other pull-behind combine I've seen surviving from that era in any numbers, at least around here, is the John Deere Model 12. Of the small combines that survive, most are rusting away in the weeds, displaced by bigger self-propelled combines. However, a few pull-behind combines are stored and maintained with care by people who still do their own grain and seed crops. Far Acres Farm has been harvesting organic small grains since 1997 using a late-model AC 66.

Our operational combine, Serial B-69872 , is a 1958 Series B with the 25 bushel grain bin (earlier combines had had an 18-bushel bin, or a bagging platform), a Scour Kleen grain cleaner above the bin, and an unloading auger emerging from the right side of the bin. This model is called the Big Bin 66 in Allis-Chalmers Farm Equipment 1914 - 1985 by Swinford. The photocopied manual I have is for the earlier version of the Series B , with the smaller grain bin (recognizable by the unloading auger on the front), and doesn't show the grain cleaner at all. I have given up on my manual distribution, as my copy is a second-generation photocopy and I wasn't satisfied with the results. As of 2006, a web search finds several sources of reproductions, notably Tom Yanowski's All Crop site and SSB Tractor.

The combine in the manual is 15' 10" long. The claimed width is 10' 6", but I think my later version is more like 11 feet wide over the fixed part of the unloading auger. The parts combine was even wider, as it had dual wheels on the RH side and an extended reel drive shaft. Height to the top of the grain cleaner is around 9', to the top of the unloading auger when raised back against the grain bin is about 12' 6". Wheel track is 7' 11". Empty weight is around 3,000 pounds.

I have run mine with a 33 PTO HP diesel John Deere 1050 tractor with unballasted turf tires. There was no shortage of power, but the combine is heavy enough to make the tires skid a few times while stopping it on pavement. Usually I use my other JD 1050, which has bar tires and ballast. The AC 66 is tricky to transport over the road, because even with the tractor's drawbar swung to one side, the tractor still extends a foot beyond the right side of the combine, making the total width almost 13 feet.

Pictures of B-69872 being moved over the road and in operation during the Summer of 2011 may be found in my Picasa album.

Repair and Refit

We got our Model 66 from the owners of St. Lawrence Nurseries in Potsdam, NY. They had bought it as a parts source for another Model 66, but it was a little too good to dismantle. In January, 1995, my wife towed it as far as South Hero, VT, but either the cold weather or a previously damaged wheel bearing conspired against her, and it came the rest of the way home on a ramp truck. It wasn't serviceable when it arrived, having spent years stored outside without being cleaned out after use. The wet grain ate through the bottom of the concave, someone patched it, and later it corroded through again at the edge of the patch. The cleanout doors at the bottoms of the grain and tailings elevators and the unloading auger were also swiss cheese. The concave bars were scrap, and the lower draper and the ledger plate rubber had rotted. On top of this, it now needed a wheel bearing and axle before it could go any distance.

The first step was to find out what was available for parts, and what would need to be made. Agco (the corporate heir of A-C) no longer sold the rubber-faced cylinder bars, so after a brief dialogue with Mr. Anvil, the straightened originals were set aside for later re-installation. Even had the concave still been available, I would have had to disassemble most of the combine to get it out; I decided to cover the holes with a stainless steel bottom sheet. The lip ahead of the ledger (shelling) plate wasn't available either, but it could be removed and repaired. Agco didn't have new stub axle/bearing assemblies, or manuals; at that time Jensales Reproductions, in Albert Lea MN had parts and accessories manuals, but not the operators' manual.

I started asking around, and hit paydirt with the New Hampshire Chapter of the Northeast Organic Farming Association . They directed me to a member three towns away who had both a working Model 66 and a parts combine! He let us copy his manual, and I traded the scored axle and some money for a good one (his parts combine only needs to roll in and out of its shed).

After I got the axle on, I called the Agco dealer and ordered what I could: new drapers, concave bars and rubber strips, and the ledger plate rubber. The new drapers were quite expensive - about $700 for both upper and lower. If I were doing it again, I'd follow the advice of the NOFA combine owner and have a sailmaker make them (they're more common in New England than in the Great Plains) particularly since my steel armored slats were intact and re-usable with new rivets. Everything arrived promptly and complete - they double-shipped the concave bars and rubbers (and didn't forget to charge me for either set) - I took this as a Sign and kept the extras.

I made the new concave from 16 gauge stainless, which in retrospect was overkill. 18 gauge would have been strong enough, and a lot easier to work. I had a local sheet metal shop cut it and roll it to a 12" radius, which was another mistake - they either didn't think about spring-back, or assumed I'd allowed for it. The upshot of it was that while I could force the new sheet into place with the concave bar bolts during final assembly, I couldn't test fit it to make sure the holes were in the right places; I had a fiddly job of measuring and layout, and some suspense until I was sure it was right.

The hex head bolts holding the shelling plate had been eroded by the passing plant matter while the combine was in service, and corrosion afterwards sent me looking for my vise grips, torch, drill and screw extractors. I don't think I got more than one of the six out intact. When I reassembled it, I used stainless socket-head cap screws and Never-Seez. Overkill? A decade later, I'd do it that way again...

20 gauge galvanized sheet and steel pop rivets took care of the ruined elevator access doors. When I tried turning the cylinder over, I found that the new stainless strip I riveted to the lip & hinged plate between the shelling (ledger) plate and the top of the header didn't clear the draper slats. I either made it too long, or too curved. Some careful prying eventually created enough clearance.

The last obstacle was the long Separator Drive Belt on the rear : it runs with two twists in it, and a couple of the sheet metal pulleys had been damaged, apparently by backing into something. I eventually got them straight enough that the belt would stay on under load, but the twists come to rest about one pulley away from where other Model 66 owners tell me they should. This probably won't matter unless I start handling larger volumes of grain than the 2 to 10 acres I've been doing. In any case, taking the pulleys off the machine and straightening them helped, but the picture shows how much the belt dances around under load.

Other than the belt, all I had to do to get it working pretty well was normal crop changing adjustments. The spare hydraulic cylinder we had sitting around fit right into the mounting points; The A-C original, if it had come with the combine, would have been a high-pressure unit and might not have worked well with modern tractors. The latch on the trough-type PTO shield even fit right into the slot on the PTO shield of my 1980s Japanese tractor, and hasn't come loose in the field!

What to Do With A 50 Year-Old Combine?

The All Crop Harvester name implies versatility, and indeed the manual claims it'll combine anything from Alfalfa to Zinnias, by way of Kidney Beans, Flax and Sunflowers. So far, I've only used it on small grains like Wheat, Rye and Oats, so I haven't tried to find things like the "high lift attachment", though the "pickup attachment" would help deal with weedy crops. Also, I'd need to add extra bolts to hold the new stainless concave if I ever wanted to harvest something fragile (like navy beans) that required removing one or both concave bars. Some of the crops I want to try should probably wait until I can locate an appropriate "finishing sieve" and some different screens for the Scour-Kleen grain cleaner. These are long gone from the AGCO price list, but I'm slowly accumulating information on what was available, and how it was used - I've recently pinned the Scour-Kleen down pretty well.

The last crop my combine had harvested before it was put out to rot had been oats. With minor adjustments to the air gates and sieves, it worked just fine on Winter Rye. Since then, I've made occasional tweaks to the controls, but usually leave the setup unchanged from year to year, and wheat to rye.

B-69827's Diary over the next two decades has been moved to a separate file.

Maintenance and Parts Supply

Agricultural equipment of this vintage runs to grease fittings instead of sealed bearings. B-69872 has 75, on all sides, on top and underneath. It originally had 76, but a kludge welding job on the bracket for #28 (reel countershaft bearing, RH) filled the hole. The countershaft has a few years left before it wears it's way completely through the bearing; I ought to replace it from my parts combine. Of all the fittings, I find #66 (Grain elevator, bearing, lower front) the most tiresome to grease. One thing that looks as though it ought to have grease fittings but doesn't is the fan in the Scour Kleen grain cleaner - you're supposed to oil the axle and the tailings auger bearing when you take it apart to clean it out. I haven't really practiced enough to get into form, but I doubt I'll ever grease the whole machine in less than 45 minutes. Also, I'm quite glad I bought a 5 gallon bucket grease gun - otherwise I'd have to change cartridges three or four times.

On a later trip to St. Lawrence County, NY, I bought another combine, B-70104, a 1959 Model 66. It too has a damaged concave and rot in the bottom of the Scour-Kleen, but otherwise the sheet metal is as good or better than my first. It doesn't have the truck-height unloading auger - just an angled spout with a grain bag clip on the end - presumably a simplified substitute for the bagging platform. I found it while helping my friends in Potsdam retrieve an old bean combine they had been given. Now, B-70104 has been towed home (with much better results than the first) and is in my shed as a repairable parts supply. When I started out, I was 5 for 5 in finding mouse nests in the grain cleaners of stored combines. This hasn't been an issue since I started to shed it with the grain cleaner taken apart and open, in a place where there is a barn cat.

2016's harvest brought three new failures: First, the wooden rear bearing on the Scour-Kleen's tailings auger broke in pieces. I worked around that by removing the drive chain and fan, and removing a patch over a rusted through hole to let the grain fall through. Second, the A-C #912362 rivet connecting the upper draper drive roller to its stub axle and sheave failed. I was able to replace this by modifying a 1/4" x 2" tension (roll) pin; I used a motor-tool cutting disk to widen the slot to .060" and put a deeper chamfer on one end. Third, the chain driving the reel countershaft from the right wheel's hub broke a link. I replaced the whole thing and the new chain works much better.

A-C 66 Chain Types

Detachable-link agricultural chain is less common than it was when I first started using my AC-66, and not all size/numbers are given in the Owner's Manual. I'm making a list of the different types used: