Okay now. Onward ho! As to the construction problems that I mentioned in my previous post, here's what I ran into. You may remember, back in post #40 I had stated a concern about whether the 3/8 x 6 inch shaft would be long enough to allow adequate space between the uprights so that the pipes, when assembled to the wheels, will not run into any interference from the uprights when the wheels are turning. I had calculated the overall width of the wheels assembly to be about 5.5 inches, and the space between the uprights to be about 6.375 inches, but that wasn't quite accurate. For one thing, while the Medium Density Fiberboard that both wheels were made from is listed as being 1/4 inch thickness, as seen from the label photo in post #52, the actual thickness is about 0.260, so that added 0.020 extra width. Also, while I had estimated that there would be an intervening space of 1 inch between the two wheels, the actual length of the rounded top pipe caps I had used was actually 1.082 inches, so that added 0.082. Lastly, the interference which came into play was at the mid-point of each upright, where the long stabilizing links were fastened. These are fastened to the inner sides of the uprights, and between the links being 1/8 inch thick, and the attachment screws adding another 1/8 inch, that decreased the 6.375 inch clearance between the uprights to 5.875 inches. Now you'd think that the actual 5.782 width of the wheel assembly would still allow about 0.046 of clearance to each of the two uprights at the mid-point link connection, but that didn't hold true, as the interference occurred due to the U-shaped plastic clamps which hold the pipes against their support blocks. While I could have solved that problem by re-positioning the long stabilizing links to the outer sides of the uprights, I didn't want to do that because the outer side, instead of being flat, is a channel, and thus attachment at the outer side would not have offered the stability and rigidity that was needed. So, I knew that my best option would be to look for some flat top pipe caps to use rather than the rounded top ones which I had installed. Thank goodness I had decided to install the rounded top caps with some silicone sealer instead of PVC pipe cement! I was able to remove the rounded top caps easily by twisting them with my channel lock pliers and pulling them off. I was able to order some flat top pipe caps online, and when I received and measured their height I found it to be 1.022 inches, or 0.060 less than the rounded top caps. I wanted to add even more clearance, though, so decided to cut these down to 0.750 inch height. The inside bore of the cut down flat top caps features a shoulder at a depth of 0.500 from the open end, so this required that I also cut the short pipes which extend from the elbows, and through the wheel thickness, down to where they would protrude less than 0.500 inch past the inner surface of each wheel. I decided to make that 0.400 inch to leave about a 0.100 space where I would lay a bead of silicone sealer. Here's a photo showing the completed cap and pipe cutting revisions:
Inner-pipe-end-cap-revision-details.jpg
Since the pipe caps for each wheel are staggered 30 degrees apart from each other in the rotation, and the wheels are locked to the shaft, no cap will come into contact with another. This revision would allow the flat top of one wheel's pipe cap to rest against the inner surface of the opposite wheel, except for the fact that each of the flanged shaft collars which I had made by epoxying a shaft collar to a heavy flat washer (as also shown in post #52) had an overall width of 0.500 inch, forcing a 1.000 inch intervening space. I decided to take the assembly apart and remove one of the shaft collars from its washer, so that I would decrease that space by the width of the shaft collar, or 0.375 inch. When I did that, I found that the collar came off the washer quite easily, and too easily in fact. The epoxy bond was not nearly as effective as I had hoped it would be. So, to avoid messing around any further, I looked for pre-made one piece flanged collars on the Internet. I did find a few that were made with a 3/8 inch shaft size bore, but they were very expensive - around $30 to $45 each. I noticed however that what came up in my searches more often, for flanged shaft collars, and at a far more reasonable price, were ones made to fit a 8mm shaft (0.315 inch), which of course would have a bore 0.060 inch smaller than what I wanted. Seeing as these came in a set of 4 for just $10.99, and already had mounting holes pre-drilled, I decided to get these and modify them as necessary. That only required passing a 3/8 inch drill bit through the shaft bores, and by passing a 11/64 inch drill through the mounting holes I was able to re-use the mounting screws which I already had. Here's a link to where I found these flanged shaft collars at Amazon.com. Notice that each of these collars uses 2 set screws, which makes for a very secure hold on the shaft. I only used 3 of these when assembling the wheels to the shaft, as I reused on of my heavy washers as the inner hub on one wheel. Even though this allowed bringing the wheels much closer together, it was not quite enough so that the flat pipe caps would rest against the inner wheel surfaces. There remains a 1/16 inch space. The reason for that is illustrated in the below shown photo. The rather large Nylock nuts securing the heavy washer (at right) come into contact with the shaft collar seen at left. I didn't expect this to occur, since the same size Nylock nuts secure the flanged shaft collar seen at left, and these do clear the shaft. The only explanation, of course, would be that the factory drilled mounting holes on the outer right flanged collar were drilled closer together at the factory where made, and were probably from a different production run than the flanged shaft collar seen at left. This situation could be cured easily enough by reversing the screws holding the washer and the outer flanged shaft collar to the wheel at right, but I haven't done that yet, and it's really not a pressing matter because I now have plenty of rotational clearance and the wheels are securely mounted to the shaft with no wobble.
Flanged-inner-shaft-collar-to-washer-spacing.jpg
Inner-pipe-end-cap-revision-details.jpg
Since the pipe caps for each wheel are staggered 30 degrees apart from each other in the rotation, and the wheels are locked to the shaft, no cap will come into contact with another. This revision would allow the flat top of one wheel's pipe cap to rest against the inner surface of the opposite wheel, except for the fact that each of the flanged shaft collars which I had made by epoxying a shaft collar to a heavy flat washer (as also shown in post #52) had an overall width of 0.500 inch, forcing a 1.000 inch intervening space. I decided to take the assembly apart and remove one of the shaft collars from its washer, so that I would decrease that space by the width of the shaft collar, or 0.375 inch. When I did that, I found that the collar came off the washer quite easily, and too easily in fact. The epoxy bond was not nearly as effective as I had hoped it would be. So, to avoid messing around any further, I looked for pre-made one piece flanged collars on the Internet. I did find a few that were made with a 3/8 inch shaft size bore, but they were very expensive - around $30 to $45 each. I noticed however that what came up in my searches more often, for flanged shaft collars, and at a far more reasonable price, were ones made to fit a 8mm shaft (0.315 inch), which of course would have a bore 0.060 inch smaller than what I wanted. Seeing as these came in a set of 4 for just $10.99, and already had mounting holes pre-drilled, I decided to get these and modify them as necessary. That only required passing a 3/8 inch drill bit through the shaft bores, and by passing a 11/64 inch drill through the mounting holes I was able to re-use the mounting screws which I already had. Here's a link to where I found these flanged shaft collars at Amazon.com. Notice that each of these collars uses 2 set screws, which makes for a very secure hold on the shaft. I only used 3 of these when assembling the wheels to the shaft, as I reused on of my heavy washers as the inner hub on one wheel. Even though this allowed bringing the wheels much closer together, it was not quite enough so that the flat pipe caps would rest against the inner wheel surfaces. There remains a 1/16 inch space. The reason for that is illustrated in the below shown photo. The rather large Nylock nuts securing the heavy washer (at right) come into contact with the shaft collar seen at left. I didn't expect this to occur, since the same size Nylock nuts secure the flanged shaft collar seen at left, and these do clear the shaft. The only explanation, of course, would be that the factory drilled mounting holes on the outer right flanged collar were drilled closer together at the factory where made, and were probably from a different production run than the flanged shaft collar seen at left. This situation could be cured easily enough by reversing the screws holding the washer and the outer flanged shaft collar to the wheel at right, but I haven't done that yet, and it's really not a pressing matter because I now have plenty of rotational clearance and the wheels are securely mounted to the shaft with no wobble.
Flanged-inner-shaft-collar-to-washer-spacing.jpg
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