mini-artic-loader

h1. Preliminary Thoughts

While the kernel of this idea was growing we ran across "this build":http://machinebuildersnetwork.com/ubbthreads.php?ubb=showflat&Number=310#Post310 by GatorS, which inspired us.  It is a very nice, heavy-duty machine, and while we agree the CadTrak is too small, we think the GatorS is too big for our purposes - we already have tractors and other equipment for heavier work.  So we would like something in between.  The GatorS is over 6 feet wide and the CadTrac is 4 feet wide.   We 're thinking about 5 feet wide is right.  This lets us get through the barn aisle easily but still gives decent width for stability. It also gives a decent base for a 5-bale-wide hay grapple, which would only overhang the wheels by 20" or so on either side.  Height is also a consideration, as we need to be able to navigate under the overhung barn roofs for cleanup. 

For lift, we're thinking around 1500 (maybe up to 2000) lbs lift capacity, whereas the GatorS is over 2500 and the CadTrac is only 500.  The most important factor here is the lifting of the hay grapple high onto the wagon.  At 70 lbs each, 10 bales will only be 700 lbs total, but the grapple will be around 400 lbs.  The hay is almost never that heavy, but we like to factor in margins for safety.  Other chores can suffice with lesser capabilities, and just maybe take a little longer.  The one exception to this may be the weight of a snowblower or a firewood processor.  So the more lift capacity the better.  If need be, we can borrow the skid steer for firewood processing, though that isn 't ideal (especially since its aux circuit isn 't working), it 's only for a few days per year. 

At this time, the plan is follow GatorS 's example and base the running gear off a 4x4 vehicle.  This design eliminates several expensive hydraulic motors (it uses 1 vs 4) and also allows for manual speed changing for different situations.  For instance, collecting hay will benefit from a faster speed, while maintaining the driveway and other digging and loading operations will benefit from more torque in the lower gears.  Also, we like the idea of a very slow motion control for certain situations, like using the FEL with a boom as a lift mechanism for other projects, or as a man-lift (by adding a cage).  -For our size range, we 're thinking that a Suzuki Samurai or similar donor vehicle would be a great start.  There was some thought given to using an AWD vehicle as well, like a Subaru Legacy.  This may still be a viable path, though it would eliminate the ability to switch to high and low ranges.- Consensus from the "MBN Board":http://machinebuildersnetwork.com/ubbthreads.php?ubb=showflat&Number=3282#Post3282 is that this running gear will not hold up to the rigors of an articulating loader.  See [[Chassis]] for some technical details on that.  

So the initial design plan is a pair of 14-bolt GM 3/4 ton rear axles, shortened to the desired machine width, plus a 4x4 transfer case driven by a hydraulic motor.  The articulated steering feature requires a set of custom designed drive shafts with universal joints to apply torque to the rear axle.  The hydraulic motor is fed from the power plant, which is in the rear section of the loader where the weight is required.  There, a hydraulic pump is coupled to the power plant and plumbed to supply the drive motor and all auxiliary hydraulic circuits (more on this later). 

The two halves of the articulating frame are custom built to fit the dimensions of the donor parts while still allowing the drive train to function properly through its range of motion.  It pivots in both the X and Y planes, with physical stops limiting over-travel.  The X pivot provides the steering, the Y pivot provides ground-tracking to improve traction on uneven terrain. 

One aspect of the GatorS design that would be nice to deviate from would be the use of the steering axle in the front (see above).  This was done so the transfer case and the front differential would line up properly.  We want to investigate if it is possible to instead use a second rear axle in the front and eliminate the steering mechanics completely from that component.  The challenge there is that usually in the front axle, the differential is offset, while in the rear axle it is usually centered.  There may be other ways to deal with it, -like using different, non-articulating hubs instead of the steering hubs- (the axle lengths would be different due to the offset), so that requires some investigation. 

The power plant for this project has not been chosen.  We are thinking any of the stock engines from the Suzuki Samurai line would serve just fine, with one concern: RPM range.  Hydraulic pumps have a range they need to operate within.  Stock vehicle engines operate at relatively high RPM compared to those pump ranges.  This might require the addition of a chain-driven jack shaft to couple the hydraulic pump to the engine.  This design would increase the torque of the engine at lower RPM (which is good) and bring operation within range of the pump 's specifications.  It would also make it easier to incorporate a second pump for the working systems. One negative aspect of this is that it introduces side-load to the input shaft of the hydraulic pump, so that must be considered - a design could be made that does not do this.  This whole topic needs some research to fully understand it, but specific work on the design and ratios really isn't useful until a donor vehicle has been selected and the specs for it are known. Again, prior experience from the "MBN Board":http://machinebuildersnetwork.com/ubbthreads.php?ubb=showflat&Number=3282#Post3282 indicates that a 25 HP engine (like from lawn equipment) will properly power this machine. That opens up the possibilities and could really simplify things mechanically in the power plant module.

The main design aspect though - to decouple the power plant from the drivetrain using hydraulics lets us build in articulation and makes the power plant more of a module.  Rather than having to couple to a specific transmission (not too hard, really), it only has to couple to a jack shaft system.  We think this will lead to better maintainability and more flexibility if/when we find that our power plant is not up to the task - though 40 HP should be plenty for a machine of this type.