Koehring 366 on a 466 undercarriage

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Rat maze of air lines
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House and cab removed
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Engine and Pump assembly on the ground
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Several views.
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Outer skid rail is not structural
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Note swing motor and drive motor
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Track pads pinned together
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Reversible pumps with air control
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The Bottom side
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Bolted lower unit
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Dog Clutch
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bevel gear
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Gear box on Deck. Drive gears and drive shaft on right, swing gear on left

Featured here is a Koehring 366 on a Koehring 466 undercarriage shown just before and as it went for scrap. The machine originally belonged to Mead logging company of Buxton Oregon and dates to the late 1960's or early 1970's. It is an American build hydraulic excavator aftermarket modified to a log loader. The modifications included the oversized undercarriage, and extra counterweight, elevated cab and a straight boom instead of the traditional dog legged boom used in excavators for digging deeper.

Koehring was an old line American cable shovel maker with a solid reputation, but like most of the US shovel makers, they didn't survive the 1980 economic bust. You can see the seeds of their destruction in this machine. They simply took their cable machine and put hydraulic drive inside of it instead of rethinking the machine from the ground up. When the Asians decided to enter the market they had no legacy designs so they produced a clean sheet hydraulic design which was vastly cheaper and less complex than this machine. For example you can see in the first photo the sloped door in the center for the cable passage way even though the machine had no cable. The second photo of the rats nest of air lines under the cab tells it all. What a mess. I'm sure when the machine was new the hoses were neatly arranged but the number of them is simply amazing.

The first generation hydraulic machines including the Hopto 900 and the American 35 featured elsewhere on this site (category big iron) had manual spool valves and levers to operate them while later versions used hydraulic pilot system with joy sticks. But not Koehring. Air was a traditional power assist for cable machines for setting clutches and brakes on the drums, and so air controls is what you find here. the cab had air joy sticks with a series of air finger switches which operated the functions not on the main joy sticks with a spider web of air lines flying through space in the cab to reach these switches. the spool valves were pretty much manual valves with air cylinders on them.

The real killer though in terms of complexity was the drive mechanism. Now the Asian design for a drive was simplicity in itself. --- a planetary gear reduction inside the sprocket with a hydraulic motor direct coupled. But did Koehring go that way. Not on your life. They retained all of the old mechanical drive, so you have a drive chain that runs from the sprocket to a cross shaft, then a bevel gear that goes up through the circle, and a be reduction gear box on the deck. The hydraulic drive motors are on the deck sticking in the holes that used to have a mechanical shaft form the engine connected. They didn't even think of reversing the oil flow with a spool valve. They have 2 reversible pumps with air cylinders on them to reverse them. As a consequence this machine has a total of 5 hydraulic pumps on it--4 native pumps, and one add on pump to handle the grapple rotate and open/close functions, and to elevate the cab.

The third photo shows how little there is there, once the house is removed. The engine (a Detroit 6V71) is mounted on a subframe and held in position by 4 bolts to the main frame. The fuel tank is directly under the engine. Instead of a flat plate deck, the main frame consists of a couple of I-Beams which run back to the counterweight.

The hand lever with the 2 air cans visible on the side of the bell housing is an overcenter disconnect clutch. If you have air you can set/release it with air control in the cab. For a cold start it could be manually disconnected.

The engine controls are largely electric however with both the regular shutdown and the emergency shutdown being electric solenoids---one of the few times this writer has ever seen a Detroit with other than a manual emergency shutdown. On a Detroit the regular shutdown move the fuel rack to the off position which should stop it, but occasionally something would go wrong with a Detroit and they wouldn't stop this way and might runaway, so they were equipped with an emergency shutdown which was a butterfly valve in the air intake. Once tripped the emergency shutdown cannot be released except by going to the engine and resetting the trip mechanism.

The lower unit is bolted together. The swing frames are bolted to two heavy I-beams which are in turn bolted to the lower structure. I found lots of stress cracks in the lower unit and all the bolts holding the assemblies together were loose. The drive technology is of an ancient design. Two air lines come downstairs through a hollow drive shaft. Each side has a dog clutch and a band brake which operate together on a single air can. When relaxed, the dog clutch is released and the brake set, and when aired up the brake releases and the dog clutch engages. This is the sort of drive that you would expect to find on the bottom side of a cable shovel. The modern thing here is that you don't have to lock the house and pick up a mechanical connection to operate the dog clutches.

Separating the machine at the rotec bearing is more than just undoing the bolts that hold the Rotec on the lower unit. You have to remove the air tubes that pass through the hollow center shaft which is accomplished by disconnecting the lines on the bottom inside the bevel gear box. and unbolting the hold down plate on top and pulling them out of the top side. The bevel gear on the drop shaft is held on the shaft with a snap ring which has to be removed before you can lift the upper unit off the rotec bearing. The upper gear reduction box still won't come off the deck even with the removal of that snap ring on the bevel gear. The swing gear has to be removed as well. As you can see from the photo of the upper gears the drive (center) shaft is splined on its gear and will pull up out of the center once the snap ring on the bevel gear is removed on the bottom. At this writing I still have not determined how you get the swing gear assembly out.

- - Updated 12/20/2012
- - Updated 04/10/2008
- - Updated 7/29/2007
- - Updated 03/27/2008