Morgan Silva Track

Morgan skidder
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Morgan with fixed grapple
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This is the actual frame of the Morgan when it was under assembly. This is a rear view. The flip-flop is in the rear axle.
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This is a front view of the main frame providing a good look at a wheel motor.

The logging industry has always been innovative, but the development of the log skidder has been pretty much stuck in a rut for quite a number of years. In the beginning, 40 years ago, Wagner was innovative, and then there was a great rush to rubber tired skidders, with mostly small ones achieving the initial popularity, with the horsepower growing gradually over the last 30 years.

Indeed the machines have become very standardized. The most notable difference has been that John Deere has used a 'hard drive' and a powershift transmission adapted from their farm tractors, while everyone else has used a torque converter in the drive train. Otherwise the machines have all been from 100 to 200 hp, followed by a converter, drop box and drive axles with some sort of differential lock. there are just 4 tire sizes common to log skidders--a wide and narrow tire option for 25 and 32 inch wheels, with the latter being the norm on skidders over 150 hp.

With the dawn of 1996, Morgan Silva Com ( a Canadian start up company) and released a completely new idea in log skidders. To use a phrase of some political people, they have reinvented the log skidder. Nearly every log skidder ever made has been mechanically driven and steered via articulation. The only except that this writer knows of involve some early Pettibone skidders which were steered with steering axles on both ends, and a Portland company (Westfall) who briefly built a large skid steer log skidder. This writer saw a Westfall just once on a equipment lot in Portland in thte later 1960's. The machine was something else. It had Cummins power that went back to a 3rd member under the operators seat. From there the power went out to the rear wheels and then forward in chain boxes much like skid steer loaders of today. The machine was simply large however, as I recall mounted on 18x25 highpressure truck tires. There was a very little bit of steering designed into the front axle. It isn't clear to this writer if it turned in the chains or had a ball joint that would turn a little. Primary steering however was 'skid steer'. Behind the cab was a winch and on the back was a loader with forks for loading logs. There was a fair lead in the middle of the rack so you could yard logs with the winch using the loader as an adjustable height arch, and then pick up the logs on the forks and load them. The front of the machine had a blade. A wonderful all in one machine. Too bad it didn't work.

What Morgan SilvaCom has done with their Silva Track line of skidders is to dump all the conventional drive train in favor of a hydrostatic drive. The power unit simply runs a bank of hydraulic pumps. Hydraulic motors are installed in each wheel. The motors are direct drive with no gear reductions. This elimination of drive lines and drive axles also eliminates the engineering difficulties of providing 'steering' instead of articulation on the skidder. As an example of engineering overkill note the massive fabricated steel plates holding the kingpins. They were designed to the maximum size that would fit into a 32" wheel. Note also that the mounting points for the rear grapple are on the oscillicating portion of the rear unit. This is a 'better idea' , I guess, but this writer has no clue as to why it is a better idea. Oh well, engineers have to go weird sometimes.

Morgan followed through logically, and created a log skidder which is BOTH steered and Articulated, following the trend begun in Road Graders (which used to be only steered), but which are now often both steered and articulated). Steering drive axles have always been one more thing to break, but with a hydrostatic drive this excuse not not providing steering disappeared and we have the world's first 'green' log skidder. Poclain wobble plate motors in the wheels provide the power with no drive train at all. The only universal joints in the machine are in the steering column between the steering wheel and the orbitrol motor.

It is billed as a ''green" skidder because of its unusual ability to turn without sliding its wheels, and its ability to avoid tracking into its own ruts. You see, conventional skidders have a couple design problems that aggravate ground disturbance. First, the articulated steering (though very useful and necessary for a log skidder) guarantees that the rear wheels will follow on the front wheels. No matter how you turn it, the rear wheels always follow in the same wheel tracks as the front wheels. Accordingly to the extent that the wheels are disturbing the ground, it is guaranteed a 'double whammy' as both sets of wheels always go in the same place. This is not the case, however, with a machine that can be individually steered on both axles. The operator can readily set the wheels so the machine 'dog trots' so the rear tires do not follow the front tires in the same track greatly reducing the potential for ruts. Secondly, the hydrostatic drive eliminates the need for the 'differential lock' and drive train bind which forces wheels to slide or spin at least some every time the machine is turned. Intelligence designed into the hydrostatic drive allows the machine to turn freely without every binding which mechanically driven machines always do. The same intelligence prevents 'spinout' as well, and an override control is available to the operator where occasional extreme conditions mandate a '4 wheel lockup'..


The Morgan Silva Track will use the front and rear (Ackerman) steering plus the articulated frame to accomplish a tight inside turn radius of 15 feet which is pretty good for a machine with a 11.5 foot wheel base. It is shown here in a fixed boom grapple configuration along side a CAT 528 skidder with an Esco Swinging grapple.

Operational Controls

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The hydrostatic drive also provides a fail safe, and logger proof solution to the problems of skidder brakes. the machine doesn't even have a brake pedal. The brakes are spring set, hydraulic released and integrated into the hydraulic motors in each wheel. The machine has just 2 pedals on the floor, a 'Go forward" pedal, and a "go backward" pedal. If both are released (or the hydraulic pressure goes away for any reason) the brakes set up providing idiot proof parking. The parking brake, such as it is, is a switch which disables the "go pedals". This concept of auto braking is not new, as it is familiar in hydraulic drive excavators and log loaders. It has simply never been applied to log skidders which have a record of brake problems, and operator errors regarding the usage of brakes which are not possible with these automatic brakes. The friction brakes such as they are are actually only effectively parking brakes. Speed retardation (hold back on hills/slowdown) is normally done by the hydrostatic motors as they will not 'over run' so the same hydraulic power that drives the machine also retards it.

Besides 2 floor pedals, the machine is operated with a steering wheel and 2 joy sticks accessible to the right hand. The steering wheel controls an orbitrol motor which handles the articulated steering. The axle steering on this machine is managed by 4 push buttons on a joy stick. One pair of push buttons is left/right on the front axle, and the second set of push buttons provides a similar function on the rear axle. Elsewhere a logic control switch will allow the axles to be steered together either to turn or crab walk.

In addition to the 4 standard grapple functions the grapple has a 'squeeze' function which modestly continues to try to close the grapple as you travel. Closed center hydraulics make this nifty feature possible. There are two completely independent hydraulic systems on this machine, one for the drive and the other for the cylinder functions. This is intended to reduce the risk of contamination in the all vital drive circuit.

Highest Horsepower in the Industry

While they were at it, Morgan Silva Com has taken the horsepower race another click up and they offer a variety of engines ranging from the Detroit Penske 40 series set at 210 hp upwards to the Cummins NTA 335. The particular model joining the VanNatta collection, however, features a 260 hp Cummins C8.3 of their newer Bosch injected C Series.

Future Innovation

One of the nifty things about having a prototype is that model changes come fairly often as R & D continues. Already future production models are scheduled to be different in several particulars. The cab has been redesigned. In this unit, there is a single sliding door on the left with an opening rear window as the emergency escape hatch. The heater and airconditioner are on top of the cab, and overall the cab is crowded. a redesign has provided more space inside allowing the heater/airconditioner to be moved into the firewall--a place of much greater safety. A second sliding door has been added on the right and overall the space in the cab has been increased.

Joy stick driving

Gone is the steering wheel. Look ma-no steering wheel. Gone also are all the floor pedals. Instead a left hand joy stick has been added. Move it forward and back for travel, left and right for steerage. The entire seat, joysticks and all swivels inside the cab so the operator can turn sideways and avoid having to rotate his/her head 180 degrees while backing. This strongly rotated physical position has traditionally been a source of physical problems to operators over time. For some reason driving and bouncing along with the head and neck rotated 180 degrees sometimes overextends the neck muscles, but with a classic fixed grapple skidder this physical position is necessary in order to see to pick up the logs.

Rotating Seat

With sealed doors, Lexan windows, heater, air conditioner and a swivel seat one is well on the way to having a degree of comfort. One can hope for a place for ye old grub bucket and even dream of an expresso machine in the corner. Our Machine has a pretty good place to hang the obligatory 2-way radio, and we even found a place for the regulated power supply to kick the voltage down from 24 to 12 volts to run the radio. Not everyone appreciates the problem, but actually, most loggers need to carry a couple radios with them. A CB radio for dispatch and traffic control around the landing, and an UHF (usually in the 457 mhz band) for distance communications.

ROTEK Bearing Oscillation

One of the most nifty things that is coming in subsequent models, however, is a redesigned rear unit with the elimination of the oscillation. Throughout the history of articulated machines oscillation has been handled either by an oscillating axle or by a swivel in the hinge, usually fabricated by welding a large thick wall tubing to the hinge unit and having it turn on brass bushings in the rear unit. Invariably the rear drive line of necessity was routed inside of this creature. The size of it was always limited by the back that it had to be centered over the driveline so increased size also implied reduced ground clearance.

With the elimination of the drive shafts, the point of oscillation no longer needs to be positioned to protect the drave shaft alignment. Apply a little free thinking and one realizes that the thickwall tubing solution of a center pivot is not a requirement if center oscillation is used as it is with a mechanical drive machine. This is good news. the Center oscillation is the least complex, but the the tube within a tube always seemed to have too much slack in it. Enough said. Watch for the next model Morgan to have a Rotek bearing handling the oscillation. Strong, no slack, and it allows the rear unit to be a single structural piece.

Morgan didn't exactly invent the idea of using a Rotek bearing in this application, as they are common in 'Arctic' trucks. (The Articulated Quarry trucks which are becoming ever more popular), but it is a good simple reliable solution to a problem.

Detroit Diesel 40 Series

Also new in the latest incarnation of the Morgan is the introduction of the Detroit Diesel 40 series engine instead of Cummins Power. It is not that there is anything wrong with Cummins, but the Detroit 40 series is a smaller less expensive package. Buyers tend to be a little skiddish about engines that they aren't familiar with and certainly all the Detroit-Penske engines have been in this category since Detroit had to abandon the 2 cycle models which they had featured since the 1930's. The good news is that one does not need to wonder whether the Detroit 40 series will 'work out' or not. It already has. The engine has been around for years. We know it and love it as the Navistar International 466. For highway applications Navistar has converted the classic 466 to an Electronic controlled engine, but Detroit is marketing the mechanical versions under the Detroit series 40 name for non-highway applications with the classic Bosch fuel injection system. This 2 gallon engine (There are 231 Cu In to the Gallon) has been around for about 20 years and its reputation for reliability is among the best in the industry. Mid range trucks and school busses with this engine are everywhere. If you get out your metric to inch converter you will observe that 7.6 liters (the number used by Detroit, and 466 Cu In. the number used by Navistar are very similar).

On board Computer

The real highlight of the 1997 rendition of the Morgan Skidder, however, is the on board computer. In the 1996 version (shown above) there are 2 variable displacement pumps (one for each end of the machine) and a flow divider to allocate the oil left and right with a manual 'lockup' system to force all wheels to spin. However, for 1997, they went to variable displacement pumps (one for each wheel), and a computer. The computer senses the angle of articulation, and the extent of steering on each axle, and the desired speed of the machine and commands the pumps to pump the right amount of oil to each wheel in order to execute the turn without wheel bind. The speed of the wheels is adjusted for the steering angles, but all four wheels will spin if the machine spins out and all will turn just as smoothly as can be. If a wheel looses traction, it doesn't even speed up, as the speed of the wheel rotation is determined by a computer relative to the other wheels considering the steering position so 'spin outs' simply can't happen.

For more see the page for 1997 Morgan Skidder

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