|Morgan Fixed Boom|
The Silvatech folks have not been idle in their product development cycle. In 1996 they produced a fixed boom skidder which featured a mechanical logic box to control the wheels and provide 4 wheel drive. It featured 2 variable displacement pumps plus some logic to make all the wheels turn.
Sorry about the pictures below, but it was taken in a Safeway Parking lot as the machine was passing through town and almost after dark.
For 1997, they redesigned the hydraulic system completely. The 1997 model Morgan skidder features a 4 pump system -- one variable displacement pump for each wheel. Sensing devices measure the steering angles and feed the data into the an on board computer which then assigns the right amount of oil flow to each wheel so as to provide even power to the wheels regardless of whether they need to turn at the same speed -- as in when you are driving straight- or they need to turn at differing to facilitate a turn. The computer also monitors the engine RPM and if the engine is overloaded, it will back off on the speed a bit to allow the engine to maintain RPM instead of allowing the engine to die.
The rear unit is completely redesigned with improved ground clearance. A Rotek bearing has been substituted for an oscillating rear axle greatly simplifying the rear unit -- It is not one solid piece. As before the fuel tank is in the rear unit but the tank is now larger, and at 84 gallons should provide the traditional 14 hours of service between fuelings. Fuel consumption is observed to be around 5 gallons per hour. Space is always a problem in log skidders and more than one, I know of won't work a 10 hour day without a fuel call. Not only is the tank big enough, it is also shaped such that you can recover most of the fuel from it even if the machine is grossly off of level. Traditionally skidders become fuel starved when they are way out in the woods standing on their end or side trying to get to that hard to reach log. The rear unit is designed so that various attachments, including a winch, fixed grapple or swing grapple can be installed on any machine. This means that the base machine can be produced and the attachment of the customer's choice installed later.
As before all the hydraulics are electric controlled. There are 2 completely isolated hydraulic systems on board-- one for the wheel motors, and the axillary system for the blade, steering, and attachments. They even have dual oil tanks. This isolation minimizes the risk of contamination to the all important wheel motor circuits. There is also a difference in the operating pressure. The Wheel motors work at up to 6,000 lbs pressure, while the pressure on the auxiliary system is more modest.
Gone from the machine is a steering wheel, tiller or anything on the dashboard requiring serious attention. There is an electric joystick mounted on each armrest of the swivel seat which control all functions of the machine. There are no foot pedals, so the seat can be turned to any position and the controls will worked equally well. Our preferred position for operation is at 90 degrees or looked directly out the side of the machine. From that position you can look either forward or to the rear with equal ease. Visibility to the rear is actually much better than it is to the front. Other than the fact that the directional tires are set for going forward one direction works about as well as the other. Indeed many operators drag logs to the landing and then back out into the woods to save time in turning around.
TreeTow has produced the swing grapple for this machine. It has a 12 foot reach which is more than the reach provided by current production ESCO or Young Swing Grapples. The Swing grapple is particularly suited for thinning operations. They typically won't pull as much wood as a fixed grapple because of their positioning, but, you can fish trees out of the woods that you simply cannot get with a fixed grapple, and they will pile the logs in the landing without driving over the pile which reduced breakage. While the fixed grapple may be the choice for working behind a feller buncher or other mechanical harvester that leaves several logs in a pile, the swing grapple is the clear favorite for hard to get logs and thinnings.
One of the on going problems particularly in western softwood forests is brush control, especially along roads. Hardwoods of little or no commercial value are quick to regenerate on road shoulders, road cuts, while at the same time limbs from plantation regeneration will invade the roads right of way as well. While chemical applications of often used, they have the drawback in that the material is still obstructing the road--even if the chemical has killed it. According mechanical cutting is often a suitable alternative to chemical application.
This is where the PRO MAC cutter head comes it. it is a 36" rotating cutter designed not unlike a rotary lawnmower. The cutter wheel is heavy and doubles as a flywheel. it has carbide tipped cutters sticking out all over and is powered by a 50 HP hydraulic motor operated by the skidder hydraulic system.
Such cutters have been around for many years, but a practical carrier for them has always been a problem. The first ones I ever saw were mounted side saddle on a road grader. The grader was heavy enough to handle the cutter and boom but lacked a hydraulic system sufficient so an auxiliary engine was installed to power the hydraulic pump. The county Road department used it,and we called it the mail box chopper because that is about all the unwieldy thing was good for. the grader couldn't be maneuvered well and the starting and stopping quickly destroyed the clutch on the grader.
I've seen them on all sorts of other mounts, but on most they don't work well because you need to run the machine engine at a fairly high RPM to provide oil flow to keep the cutter running and you need to be able to maneuver the machine at the same t ime. Hard drive machines destroy their clutches and torque converter machines jump out of their pants if you try shifting at full throttle. For all practical purposes, a hydrostatic drive is the only sort of a machine drive that works right for this application. Since Morgan has produced the first hydrostatic drive skidder we are fairly confident that this is the first swing boom skidder to successfully use a mechanical brushing head. The mounting is simple. The grapple is removed and brush cutter is bolted on instead with a single large pin with a threaded nut. A small hydraulic cylinder is added on top to control the wrist action. The grapple close function manages the rotation of the cutter and the grapple rotate function becomes the wrist action.
Several forestry organizations have mounted similar mechanical cutters on a boom on a hydrostatic drive farm tractor. They have been around for a number of years. The drawback of the farm tractor solution for a carrier is that the farm tractor is badly out numbered. The side load does in the wheel bearings and really pushes the tractor beyond its design. Also, farm tractor can scarcely leave the relatively level road surface.
By comparison, the Brush cutter head doesn't weigh more than the grapple it replaces on the log skidder. Since the skidder is designed to go anywhere and have a log in the grapple too, the skidder is not over stressed operating the cutter. Whats more, with the classic log skidder go anywhere capability, one can within reason drive up and down the road banks to reach those hard to get items.
|Drilling for Tree planting|
It didn't take us long to determine that there were things besides dragging logs that a good skidder like this was good for. The hydrostatic drive makes it particularly suitable for brush cutting, but also for other things.
What we have done here is to simply drop off the grapple (easily done by pulling one pin and disconnecting the hydraulic lines), and have replaced it with a hydraulic digger assembly which spent its first life on a utility digger derrick truck.
When we decided the truck was at the end of its life we bagged the digger and adapted it to fit the skidder using the same circuit that closed the grapple. Here it is shown drilling holes to plant some hardwood nursery stock. You could I suppose dig in the nursery stock with a backhoe, but the drilled holes provide an even consistent hole with well pulverized soil and are our choice.
While 1997 produced a 4 pump design with computer control, and a redesigned rear unit with improved ground clearance, and a platform suitable for a swinging grapple, 1998 will see further refinements. The cab will be redesigned to be of a more simple design. The complex sliding doors (one large one on the 1996 model) and 2 smaller ones on the 1997 model will give way to more traditional swinging doors. Visibility will be improved and ingress and egress will be improved as well.
In 1998 look for the front unit to get a reworking for improved ground clearance, and exact fit to the Detroit Diesel 40 series which seems to be the engine of choice. Detroit recently signed an exclusive marking agreement with Navistar International for the Electronic version of this engine (called the IH 466 when sold by Navistar). Although the driving force for the 'E' versions of any diesel engine is emissions control, the 'E' Versions also provide opportunities for interfacing the engine computer to the hydraulic control computer. The result can be a 'power on demand' system where the engine throttle is adjusted by computer to match the the loading. This technology is already used in excavators and seemingly can be adapted to skidders as well providing some fuel economy opportunities.