Robot: Dohn Joe (Sub-section )

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The image above depicts the component assemblies that make up the wheels. There are 23 individual components to make a single wheel. Close inspection reveals four bearings per wheel. Two are radial bearings and the other two are needle thrust bearings. The thrust washers that ride on either side of the needle thrust bearings are hardened to RC-76. The outter race is made from 3/16 O-Ring material.

The next two images show the assembled wheel assembly. Here the close up of the driving belt pulley is clearly visible. I cut these from a solid log with a 0.030" slitting saw. The operations involve centering the round stock in an indexer (1'st op on lathe to put in centers). The setting the slitting saw centerline and removing the center cut material for all of the teeth. Next the slitting saw is set 14.5deg above centerline and each of the teeth are faced with the first angle. Finally, the process is repeated at -14.5degrees to cut the back face of every tooth.
Wheel Assembled Front:		Wheel Assembled Back:

Large Pulleys:	These parts carry a long sad story about how to hold components while they are being machined. I produced the initial components on my drill mill some many, many, years back. As a learning mistake, I held the pulleys in V-Blocks in my Kurt vice. As I slowly machined away the material the 0.080" toothed pulleys deformed. This allowed the eyeballing of threaded holes to fit correctly. The later sets of these pulleys were produced by my friend Jay on a production mill. This allowed the design flaw to be seen fully as in these parts. The parts function correctly, however the holes do break through the walls in some locations.
In the photos these parts don't look quite so hot as I hadn't cleaned them up yet. They have some grease markings and also rubberized PCB marking ink. Further below on this page there is a shot of two of the pulleys that have been cleaned up. These smaller pulleys were not fabricated, but rather, purchased as recovered stock from a surplus vendor named Vetco here in Pugetropolis.		Small Pulleys:

Berring Blocks:	These parts are the main bearing blocks. They encase two radial ball bearings and a surface needle thrust bearing. A second surface pin bearing rides along the front surface. A few of the bearings are depicted, below. The small MS-paint image, below right, shows the stack-up and retention of the bearings. Notice that even though the radial bearings have an interference fit to the cavity reamed to 0.0002" undersized in aluminum. they are retained by a head ground onto the wheel axle. This allows the entire assembly to be assembled left to right with a single retaining screw on the wheel side at the extreme right (not shown). To facilitate the head feature on the pin, an ejector pin was used for the robot's axle. The material these components are fabricated from is 1" thick aluminum extrusion.
Berrings:	Berrings:	Berring Blocks:

The radial berrings and washers are visible in the image below

New Motors:	These two motors will be the power plant for this robot. They are specialized 5-pole DC permenant magnet motors. The specialized 5-pole configuration gives extremely smooth and even torque at low RPM's. The original motors have been replaced by the clifton precision motors (left) that have much better specs and still provide the requisite torque at much less of a weight penalty.	The Motors:
Three Nickle-Cadnium 9.6v battery packs running in series will provide the power for the robot. Compared to the weight of the entire robot (with the exception of the motors) make up most of the mass. Therefore they require centerline mounting, low, to further lower the center of gravity.		Battery Hanger:
The battery hangers depicted in the photo (right) carry the three battery packs suspended (hanging) below the suspension. These parts look delecate but 0.100" aluminum can more than withstand the stresses applied. The only fear here is dropping the robot off a table or some other such catastrophy. In hoping to get this project done a little quicker I outsourced the fabrication of these parts to my friend Jay who did a wonderful job. Thanks, Jay!!! Notice that these spindly little parts are actually machined from 3/8" thick stock and the parts are nearly net with the stock on both faces, only a light sanding separates that. As such, the holes moved just a tiny bit when the material stress relieved. This is okay as the part is light weight enough and allowed to flex a bit in the final design.		Battery Hanger:
	Here are the motor hangers. Two of these parts will rise from the frame on each side of the robot and support / tension the motors and pulley belts. These highly custom parts will take a decent bit of setup to hold onto while cutting.	Motor Hanger:
New Motor Hanger	So ... the design has progressed a bit further down the proverbial path to reach the realization that a few concepts needed revisiting. The motors have been changed out for some that will lead towards a goal of higher battery life. The new motors are shorter and as such, simplify the motor hangers.	New Motor Hanger

I considered making the smaller pulley for this robot. I looked at a number of ways to produce the small flat flanges, and several methods for attaching them. All that done, I decided against that option. I dug through the bins at Vetco for a few weeks until a matched pair of small 0.080" pulleys came round. Eventually they did, however they were 1/4" shaft size, not 1/8". I decided to make a small set of stainless steel adapters. There is a clearance cut for the set screw from the small pulley to pass through and lock into the motor shaft. The adapters take a very light press fit to install into the pulley. I have yet to trim them to length in the photo to the right and this makes them easier to see...

These little black parts are the sensor mounting brackets. They attach to the sensor mount swing arm below. The pile here might look a little high. That is because there are 24 of them. The pile becomes a little high when you need to make 8 of them for each of three robots.		Sensor Hanger
New Wheel Stack	This pane shows the stack of new wheels. These wheels are cut directly from 1/2" thick plate stock. The new wheels have thicker hubs to give them more stability on the axels due to the large moment arms involved. Given the need to increase the area of contact with the axel, these wheel hubs have been machined from 1/2" extruded aluminum bar stock. The integral hub reamed for a tight fit on the ground axel pin makes for a quite stable mating. This methodology of producing a part from a monolithic chunk of material, however increases machining time.
Contact Pad Design	These are the fixed driving skids. In this first version of the robot troop, the stabilizing skids are fixed. A second compliant spring loaded version is planned, but as of yet undesigned. Also, if time permits, a silenode damped version allowing for stiff starts and stops and also the ability to switch over to compliant spring loaded mode for hill obstacle navigation. These components are carved from 3/4" thick 6061 extrusion.	Fixed drive skids
Encoder Mount Plate	Here the stack of new encoder mounting ring plates are visible. These are somewhat complex. They are complex in that the parts appear to connect both side at the same time. This is possible as once the encoder face plate is screwed on, the encoder snaps to it, which hides / covers the mounting screws.
Shown here, the new battery hangers. These are different from those shown above. The design was changed when the battery orientation was changed from horisontal to vertical. This is visible in the frames that follow.		New Battery Mounts

Check out the new sensor mounting arms. These arms extend in a counter clockwise fashion around the electronics & battery section of the robot to mount all of the sonar and infra-red sensors. The mating holes are tapped #4-40. A few frames above the sensor hangers (black plastic parts) can be seen. These parts attach to the hole patterns on these parts to form a ring of eight sensor platform mounts around the robot frame.		Sensor Extension Arms
Upper Roll Cage	Hear are the upper frame roll cage plates. It is hard to see in this photo, but there are several holes drilled perpendicular through the different edges of the plate. If one looks closely, they can see small flat bumps on the back of the diagonal member. These bumps are tapped for #4-40 and serve as stand-off's for the PCB's that bolt to them.
Display Mount Wings	These are the "flying wings" that precision align the LCD display screen to the mounting PCB below. The tollerance stack-up involves five components and is pretty cool. Yes, these parts are (2 in front) non-symetrical and completely different between the left pair and right pair. The second photo shows them installed. The screw threading in these parts is a mix of #4-40 and #2-56 as mandated by the interfacing components. Heads of the #2-56 socket head cap screws are visible in the picture to the right(black) mounting the display to the wings. Consider also the thickness of the material stock that these components are fabricated from. They have been cut from a monolithic block greater than 1" in thickness.	Display Mount Wings
Inverter Box Halves	These halves are flipped over and form a hollow plastic box to house the inverter. The inverter generates 1.7KV to run the back light tube for the display generating in the neighborhood of 400Nits (CD/m^2). The box is made from plastic to prevent an accidental shorting to the body frame. During later construction steps a thin foil inner lining will be applied that has a direct ground return to the power supply board (outside of the filter section). It's a bit hard to see in this photo, but there are some small bosses machined directly into the housing to mount the different components. Opposite sides are tapped to afford mounting/mating. Yeah, it's a bit hard to take a picture of machined matte black plastic.
There are more small machined parts than I care to recollect. If you want to see them all check the CAD files for exacting details. For a quick idea of size on these small parts, the holes in the end are tapped for #6-32.		Board Hanger Clamps
The assemblies depicted here show the push rods, clasps and retaining springs. These tie into the camera positioning motors to transfer the camera, laser, & Lighting sensor platform underneath the robot from the front of the bot to the motors at the back. In the snippet, below, the final version of the rods can be seen. The cheaper tin linkage has been replaced by 1/8" drill rods, turned down and threaded at each end.		Push Rod assemblies:

Bottom Cam Assy:	Here, the reader can see the bottom camera mounting plates. These parts connect the bottom frame of the robot. They support the batteries from the bottom and the servos that position the cameras as well. The bottom sensor boards also connect into these. In the photo, these are rotated 90deg right and left. When mounted the long post that is front/horisontal in this photo becomes the primary pivot/rotation point for the front mounted stereo video cameras. An 1/8" steel shaft runs down the center of these and a machined plastic cap captures the top and rings the outside to provide stability.	Bottom Bot Plates:
It is a bit surprising for such a small robot, the number of pieces carved from physically large stock. There are six pairs of components that are carved from stock measuring one or more inches in thickness. It just takes a lot of time to machine away all of that aluminum or plastic, but even more important, when the finished parts are as small as these, figuring out how to hold onto to them while the various contours are sculpted can be tricky to avoid chatter or even worse, accidentally tearing a part out of a fixture.
Front cam Plates:	Pictured here, the front camera mounts hold the stereo NTSC video cameras to the front of the robot. These mount to a pivot joint on the plates above. Along with the cameras, these also mount the lasers & field generator optics, along with white light LED imluminators and Infra Red LED illuminators. Consider the geometry of these parts. These parts are cut from 1" thick ABS stock. That much material removal in ABS leads to feature wandering as the ABS relieves internal stresses. I spent considerable time considering the effects imposed on the vision system if the camer and field of laser light do not meet certain considerations for parallelism. The trades are acceptable and the part is produced from a thick monolithic chunk.
Small plastic parts:
The part shown here is the front camera mount turning pin. The control arm is about 0.04" thick. It's pushed by a model aircraft push rod. This part is locked down onto the turning rod (also pictured) with a #6-32 set screw. The turning rod has a flat machined into it such that it does not displace material when the set screw is tightened thus facilitating removal later. Additionally, since the flat does not run off the end of the shaft, the small part will be captured should the set screw back itself out.		Cam Turn Control Arm:
GPS & Antenna Mount:	A set of three for the three versions of Dohn Joe I'll finally assemble, these three GPS board and antenna mounts are ready for installation. These lock into the upper roll cage assembly and support the GPS module, its carrier board and the antenna. I've chosen to use a mounting board just so I don't have to hassle with shorting out the connector as I did with one during initial test.
Bluetooth mount:	These little parts were just plain hard to photograph without getting all to much flash in the shot. The vertical holes will be chased with a hand reamer to open them up to just the size of the vertical frame bars. These parts then mount the Bluetooth wireless module on the side of the robot, right above the wheel. These components were machined from 3/4" thick aluminum extrusion.
This design has a good number of precision connecting rods, 10 total. Many of these connecting rods have machined flats at various locations and indexes around them. The machined flats facilitate the placement of set screws while still being able to disconnect the components later. The connecting rods are made from 1/8" drill rod stock. After making the first set of these without machined flats, my friend Jay produced the remaining sets.		Mounting Rodz:
Speaker Mounts:	These parts are the mounts for the speakers that can be viewed in a later electronics section of this page. The speakers are part of a sound absorption sensor used to evaluate the differences between absorbed / reflected frequency ranges towards an end of determining objects in the flight path of sound. The parts have been created with a fused deposition machine. The machine melts ABS plastic and "plots" it much like squeezing out tiny melted paths of toothpaste, one next to the next and letting them fuse together while cooling.

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