The lumber and hardware arrived!
I modified the support posts to mount the new bearings & axle.I then cut the 2 x 6 spokes to their approximate length leaving enough for a final cut later once I can measure the exact length I need.
 |
| The Shopsmith configured as a disk sander |
To trim the ends of the spokes, I tried using the mitre saw to make the 22.50 cut, but I couldn’t get the saw to make such a shallow cut. Time to buy more tools! I came back from the store with a small mitre gauge. Marking the ends with a true 22.50 , I used my round saw to make the initial cut, and the sander on the Shopsmith to adjust the angle.
Next step: I need to lay out the spokes to mark and drill the mounting holes for the hub.
Question: How do you find the center of a circle? Easy - walk into the middle of the garage floor with a piece of chalk and put a dot where you want the middle to be. Well, that was easy.
 |
| An homage to the God of Octagons |
I laid out the eight spokes on the garage floor (around the pre-defined center), and was accused of conducting some kind of weird cult ritual. (In fact, I was making an homage to the God of Octagons for inspiration). How to mark out eight spokes at exactly 450 angles from the center? Well, the first two spokes were easy…take a long straight board about eight feet long and draw a line through the center of the circle. Two down…six to go. I tried cutting it in half, then half again like my other brother Darryl’s pizza, but that wasn’t going to cut it…so to speak.
The hub I bought has pre-drilled holes, each at 450. So if I mark the centers of the spokes, and lay the hub over them, I can get close…but if I am off a little bit, say even 1/8 of an inch, the ends could be off by a lot (I’m not going to calculate how much…but you can do it if you want. Extra credit if you do - but show your work).
Another Pop Quiz: If the spokes were exactly at 450, and if I measure the same distance from the center to the ends of each of the spokes, then the distance between the ends of adjacent spokes should all be the same. In fact (…wait for it…), we can calculate what that distance should be.
Again, that distance is the chord of an angle of 450, having a radius of 43 inches. Using the trig formula, the chord distance should be 32.9” or 32 7/8”.
(you can also use the online calculator at:
https://planetcalc.com/1421/ to figure the chord length)
 |
| The Shopsmith configured as a drill press |
Now I can layout all eight spokes, mark and drill the holes for the hub mounting. I configured the shopsmith as a drill press to ensure the holes are drilled straight.
 |
| Scalloped Rails |
I tried using some of the old siderail sections as templates…but they were not the right length…in fact all three of the rails I could salvage were built to different lengths. Why am I not surprised. I’ll have to build my own from scratch.
I cut some rails to the necessary length and trimmed the ends to the always necessary 22.50. The arc needs to start and stop from the ends of the two spokes, and arch up to a max thickness of seven inches, which is what the old siderails were. How to find the center of that arc so I can scribe it?
In other words, how do you find the center of a circle given three points on the circle?
Drawing (ahem) from our geometry days in high school, you locate three points on the intended curve: one at the start, another at the end, and a third in the middle. You then draw a straight line between each pair of points. Next, find the midpoint of each of these lines, and draw another line perpendicular. Where these two perpendicular lines intersect is the center of the circle.
Voila!
 |
| Scribing the arc on the new siderails |
Now I have a couple of siderails to use later as templates.
 |
| Ensuring proper clearance |
Finally, I mounted the hub/spokes/siderails assembly onto the axle just to check the clearance between the new wheel and the porch deck of the house.
Next Step: Start building the paddles.
No comments:
Post a Comment