Wheel and Wheel Motor Mounting Procedure

The LifeTrac Tractor wheel mount assembly is constructed from: (1), two wheel mount plates measuring 8 by 10 inches, 1/2 inch thick,  with a  flange bearing assembly, a 3” shaft hole,  and two 3/4 inch bolt holes at the top; (2),  the motor mount plate which measures 10 by 8 inches, 1/2 inch thick, with two 3/4 inch bolt holes and a 3 inch shaft hole; (3), the hydraulic motor assembly that includes a 6 by 8 inch, 1/2 inch thick hydraulic motor interface plate, and a coupler for the shaft with a female 6-spline coupler; and (4), a wheel assembly including a 16” truck wheel + a 1-7/8” diameter shaft with a bolt-hole at one end and a male 6-spline coupler at the other end + three double split lock collars, two large washers with a 1-7/8 inch inner diameter, and a three-quarter inch bolt, 4-1/2” long, for securing the wheel. See CAM files for exact geometry of plates. (Shonda: please generate an exploded part diagram for the wheel shaft assembly. Make the shaft 28” long. You can also find supporting cut list information at http://opensourceecology.org/wiki/April_2011_Production_Run_BOM . For example, the wheel shafts are 28” long.

This video covers the current (as of October, 2011) LifeTrac III prototype at Factor e Farm. I will refer to the orientation of the pieces as if we were sitting in the drivers seat of the LifeTrac: north is to the front end where the loader will be attached, south is behind us at the back of the tractor, west is on our left hand side and east is on our right hand side. All lateral measurements are from left to right, all measurements of depth are from front to back, and all measurements of height are from top to bottom. Each hole center is measured from the left or top edge of the plate to accommodate for inaccurate material dimensions. Pay careful attention to only measure from the top and left reference point. Do not attempt to convert and measure locations from the right nor bottom, as even slight inaccuracies can prevent bolts from aligning properly between pieces and create overall alignment problems which can make the construction fail or lead to catastrophic failure during operation of the LifeTrac that could result not only in serious damage to the tractor, but injury to the operator. Construction of sub-assemblies in this video (such as preparation of the shaft itself, the mounting plates and the wheel assembly) will be covered in detail in other videos. CAD and CAM files are already available for these assemblies on the open+pario project-hosting website which can be used with the torch table to automatically and precisely prepare these components. See http://openpario.mime.oregonstate.edu/documents/1237

The LifeTrac III assembly process involves some welding of mounting plates to the LifeTrac frame; however, the next version of LifeTrac will have a fully modular wheel mount assembly that will be readily detachable with only 4-6 bolts, eliminating the welding in the current version that limits the interchangeability of the wheel assembly between different machines. This will greatly enhance the serviceability of the LifeTrac, allowing a wheel mount assembly to be swapped readily with another LifeTrac or another Global Village Construction Set machine that also uses driven wheels, such as Microtractor, Combine, Truck, or Bulldozer). This will readily align this component with the overall GVCS strategy of simplicity and ease of service through radical hyper-modularity.

Prop the tractor up on blocks to allow the mounting plates to be attached to the frame. Mount the wheel mounting plates onto the frame by aligning the two bolt holes on the base plates of the wheel mount assemblies to the matching bolt holes at 13 and 17 inches for front wheels or 63 and 67 inches for the back wheels, as measured from the front of the north/south frame members. Attach each wheel mounting plate onto the frame with two 3/4 inch bolts (how long?), with the bearings facing outwards.

Insert the wheel shaft through the outer bearing (on the outer side of the outer lower north/south frame member); slide the two large washers onto the shaft after you pass it through the outer bearing. Continue inserting the shaft through the inner bearing until the male 6-spline coupler is sufficiently far to attach the hydraulic motor assembly with motor mounting plate to the coupler.

The hydraulic motor assembly consists of the hydraulic motor welded to the motor interface plate. The motor interface plate allows for the easy mounting of the hydraulic motor to their respective machines by means of two, ¾” bolts, as opposed to mounting via 4 smaller, harder to access 1/2” bolts on the hydraulic motor. This unit is attached to the motor mounting plate by means of 2 bolts, 3/4”x2” long, including a washer and lock washer. Install female 6-spline coupler of the motor assembly onto the male 6-spline coupler of the shaft. Make sure to insert the male 6-spline into the female completely, so there is no more than 1/8” separation between the female coupler and the shaft face. Adjust the coupling such that the motor assembly mount plate can be welded to the vertical frame member.

When the 6-spline coupling is connected as such, there is complete alignment between the shaft and the motor assembly. Tack weld the motor assembly mount plate onto the vertical frame while maintaining alignment. Finish the weld thoroughly. As mentioned, this weld will be done away with in a future iteration of the LifeTrac to make the entire wheel assembly modular, but a previous build lacking a welded mount resulted in a broken shaft when a bolt came loose, so this iteration of the LifeTrac includes the weld to prevent such damage.

On the outside (wheel) end of the shaft, mount the wheel onto the shaft, rotate as necessary to align the bolt through-holes of the wheel assembly with the matching bolt hole at the end of the shaft and secure with a 3/4 inch bolt, 4-1/2” long.

Grease the two 1-7/8” washers, and secure these with the double-split collar using allen wrenches - to prevent the shaft from moving outwards. Add two more double split collars – one outside the outer bearing, and one outside the inner bearing – to prevent the shaft from moving inwards. Grease the grease fittings on each bearing. Repeat this procedure for each wheel. When all the wheels are mounted – tack the wheel mount plates to the frame as backup for any bolts getting loose. This tack weld should be removable easily with a grinder as necessary for service.