Help laying out a 4 spoke wheel.

Daryl I don't pretend to be anything more than a metal worker. Yeah I do have a pretty good handle on set up and basic use of the RT. I was just not sure on the layout for the spokes. not thanks to you guys I'm pretty sure I have it. I am using a sacifical piece of HDPE. It will be center drilled and also drilled in 4 spots (where the voids will be) along with the blank for the wheel. They will in fact be stacked and drilled. then the blank will be tapped, the HDPE will be counterbored and open opened to a snug clear hole. Then into the 4 jaw where it will be indicated to the center hole, then turned to dia., faced and the center bored to fit my centering pin on mt RT. the with the backing still attached on to the RT. to cut the spokes. The wheel will have a separate hub to mount it to the saw do to way it has to be machined to fit the saw. So I will not be able to get the deep spokes like yours.
Mark
 
Here is the little I got done today. I cut a blank from a 4x4 block. Also a piece of HDPE for a sacrificial backing plate.
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Drilled a center hole and 4 mounting holes in the part and the backing plate. Also tap the mounting holes in the part and counter bored the holes in the backing plate.
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Got it mounted in the lathe, and started turning.20150216_221052.jpg
 
I just laid it out in cad. You probably know this by now, but each quadrant, allowing for 1/4" tool diameter is 58.35* of rotation on the rotab.
 
Hey guys,
sorry it took so long to get back to you guys, but time has been tight and this took a little more time than I thought it would
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Machining the Spokes using the rotab. This was very time consuming.
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Back in the lathe to profile the back and bore the center to final size .625

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Finished hand Wheel.
Next is to make the spindle adapter. The saw's vice lead screw has 1.125 sticking out but 0.75 is milled flat on 2 sides to hold the floppy handle. (not sure the proper name for these type of handles) You know the type that is slotted so you have to flip/fold it from side to side. So since I don't want the new wheel hanging on a 0.5 piece of shaft, I am going to bore the adapter 0.75 deep and then slot along its axis picking up where the bore ends. sort of like a spindle bore with a MT tapper, you know the slot where you drive the wedge. the adapter will be 0.75 in dia. but will be reduced to form sholder. the wheel will be a light press fit and then fuse welded with TIG to the adapter. the adapter will also have a set screw to hold it to the screw.
Oh and of course I need to make a cranck handle.

Mark
 
BTW anyone found a link to let the mods know how you feel about the new software? I'm liken it! little learning curve but seems a lot easier to navigate
Mark
 
Figure out the angular positions and walk off 8 radial slots, 4 at the small radius and 4 at the large radius, off set the RT 1/2 the spoke width + tool off set in 1 axis and mill 4 connecting slots at 90º increments. Offset the RT the full spoke width + tool off set in the same axis in the opposite direction and mill 4 more connecting slots. Keep in mind that when milling an inside shape where the center drops out the tool will have a tendency to jam the drop against part when it comes loose.

In this drawing I used a 1/4" diameter tool, changing tool diameter will change the part radii and the spoke width accordingly. Since you are probably not making this to someone elses dimensions I would rough it with a 1/4" tool and finish with a 5/16" tool.
The angular dimensions are rounded off to whole minutes so they may be a bit off at the end, wasn't aiming for accuracy just giving you an idea of a way to do it. You can do the math yourself if more accuracy is required (-:
Good luck

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Hey,
Thanks again for all the ideas and help. Even though I changed my design it was all still helpful in gaining a better understanding.
Here is how in the end I decided to to do it. when I turned the ppart in the lathe adn faced the taper in the stokes, I also faced two rims. One at the outer dia. and one at the inner dia. these set refference points for the spoke lenghs. then I moved to the mill centered the rotab in the mill and then the part on the table. Next I moved the X axis left 0.2 and set Rotab at 348deg (12deg. off cen.). Next I touched off the two rims recorded these numbers adjusted to allow 0.020 for clean up. This gave me my start and stop points for the spokes. I cut each side of the spokes by moving X right or left 0.2 and advancing the rotab to the spoke angle.
Once all 4 spokes were rought out and I zeroed both axises. it was simply a matter of picking up the ends of the slots for the spokes, and turning the radius cuts. On the first space I just cut the 4 slots. this left the center in the way while doing the clean up. so live and learn, on the next 3 I milled the hole space out. This worked so much better. I then just repeated this all over again just this time using the final dimentions.
I do have to learn how to draw with a cad program. any body got a good web site for this. I have libreCad on my computer But still have not got it figured out.
Any way thanks again guys. And Daryl nice work on your handle.
Mark
 
So I finally got the time to finish the crank wheel for the saw. Here are some photos.
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The adapter for the end of the screw finished and ready to be welded onto the wheel. Note the slot at the bottom of the adapter, it is cut into the bore. this is because the end of the screw shaft is milled to a flat on two sides.
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The Crank wheel installed on the saw.
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The original Floppy crank. You can see here what I mean about the double flats on the end of the shaft. And why it was well past time for it to go.
Now with one good spin of the wheel I can move the vise jaw a good inch. I know it may seem like putting lipstick on a pig, but this little saw has cut anything I have been able to fit into it.
Thanks again to all those that chimed in to help.
Mark 20150222_192332.jpg
 
FYI - Swarfrat Enterprises has a 2 volume DVD entitled "Mini Machines 202: The Rotary Table" It's available from Little Machine Shop, their part number 3406. It does a pretty thorough job of covering how to use the rotary table - setup/centering, reading the degree vernier, use of dividing plates, etc. etc. Among the topics covered is a detailed description of how to make just such a 4-spoke wheel.

Cost from LMS is $40, and well worth it IMHO.
 
Thanks John, I'll add that to my tools to buy. Hey wait thats one of those things the wife could get for my birthday. and she still has time. My next project is to built that part you have as your picture.
Mark
 
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