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Old 06-09-2018, 09:56 PM
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rickoff rickoff is offline
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Quote:
Originally Posted by Cadman View Post
Rickoff,

I have been following this with interest.
Check to see if your pvc tubes are at the angles you anticipated after they are placed in the wheel.
I drew this out in CAD with a 4.5 radius and 1.05 OD tubes and it looks like the larger OD of the elbows may interfere, at least as compared to your drawing in post #2.

Regards

You are quite right, Cadman. With the pipes inserted in the bore holes, and positioned to touch the elbows of adjacent pipes, the angle that I measure is about 72 degrees (a guesstimate), which is 4 degrees larger than the 68 degree angle that I showed in my post #10 as being the optimal angle. The reason for this variance, of course, is that after figuring the correct proportions for the 3-inch build (3.5-inch pipe O.D. and 4-inch elbow O.D.) I figured my 3/4 inch build in a proportional scale. Since 3/4-inch pipe is 1/4 the stated scale of 3-inch pipe, if it actually was directly proportional then the 3/4 pipe O.D. should be 0.875-inch, and a 3/4-inch elbow should be 1-inch. In reality, the pipe O.D is 1.050-inch and the elbow O.D. is a whopping 1.318-inch. Since the pipe O.D. is actually 0.175-inch larger than expected by scaling, I should have moved the centers of my bore holes further outward by half that difference, or 0.0875-inch just to make up for the larger than expected pipe size in order to maintain a 68 degree angle. Of course I would need to move it even further outward to make up for the much larger than scale elbow O.D. which causes the adjacent pipe to lay against the elbow 0.159-inch (half of the.318-inch oversize) before expected even after correcting for the pipe O.D.

I had figured the distance to the bore hole centers, from the wheel center, to be 4.5-inches which is 1/4 the scale of the 3-inch build at 18-inches, but did not take into consideration the actual variance from scale of the smaller pipe and elbows. The info given for larger than 3-inch builds would work well enough as stated, but these small pipe sizes are out of whack with what they are supposed to be. For instance, a 3/4-inch pipe should have an inside diameter of 3/4-inch (0.750), but 3/4-inch PVC pipe has an actual inside diameter of 0.824 inch.

Here's a photo showing the prepared pipes inserted in the bore holes. In comparing this to the drawing shown in post #2, the bluish colored "clear" pipes in the photo are somewhat similar in position to pipes A and G in the drawing. Notice, though, that in the simplified drawing of post #2 the elbows are shown same O.D. as the pipes, while the #8 post drawing was more appropriately scaled to show the actual lay line and angles.




As you can see, even the 72 degree angle provides enough of an angle for the A pipe to allow water to flow outward before that pipe's elbow reaches the 12-o-clock position in a counter-clockwise rotation, and the G pipe would have its water flowing inward before reaching the 6-o-clock position. Therefore, I feel confident that the wheel would still rotate, although perhaps not as well as it would with the 68 degree angle. It's a tough call to make, because while the wider angle means that pipe positions A and G do not transfer water outward and inward quite as soon as with the lesser 68 degree angle, thus detracting from rotation, it also means that the water weight centers will be moved further outward from the vertical centerline, likely aiding rotation.

What I could do, to determine actual performance comparisons, would be to prepare two additional wheels from 1/4" hardboard, and move those bore holes further out. I could install the pipe caps for the current wheels using silicone sealer instead of PVC cement, and that way I could disassemble the build, after testing, to reinstall the pipes on the correctly bored wheels.

By the way, as can be seen, one of the pipes has a pipe plug installed at its outer end. I did this to measure for the amount of clearance I would need to allow for with the support fixture, which I found should be a minimum of 13 inches as measured from the top surface of the fixture to the center point of the wheel. That would be for the wheel as pictured, of course. A wheel bored correctly to achieve the desired 68 degree angle for this 3/4-inch build is probably going to be much larger in size. I'll figure the actual dimensions and show that in my next post.

Cadman - Seeing as you have already mapped this out in CAD, could you alter your drawing just enough to show the corrected dimensions for the pipes and elbows, and the distance from the bore hole centers to the wheel center, and then post it here? I'd really appreciate that, as it takes a huge amount of time to make drawings the way I have been doing it with Microsoft Paint. Thanks in advance for any such assistance you can provide.

Rick
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Last edited by rickoff; 12-01-2019 at 01:40 PM. Reason: updated for accuracy
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