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Mister Ed
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Phil - I see the piece you are not connecting on. One of the same little bits that had me confused.
So 1'/(3/5)min or 1.67'/min would be the actual forward speed on the cutting stroke.
Now, lets take your rough degree examples and see how they come out using the logic in the text that I posted the link to. If I spread the dwell degrees across the Feed and Return strokes (didn't know what else to do with them) ... your shaper is closer to 4/7 feed and 3/7 return (per revolution).
I dropped a snippet of the formula into the spreadsheet below. We will substitute the 7/4 for the 5/3 (book example was 3/5 feed 2/5 return).
For this shaper (if your protractor was accurate ) you will have a constant of .1458 (using the 3/5 number it is actually .1389 ... they rounded to .14). Doing the math then, you would presumably have a speed of 1.75'/min, on the cutting stroke ... not that far different from the 1.67'/min above.
That is how I am understanding this shaper speed business after reading all those old documents for a day.
But, since you're only cutting on the forward stroke ... you only cut for 3/5 of that minute, and that is the key. The cutter is travelling 12" in 3/5 of a minute ... the other 2/5 of the minute it is going backwards 12".But to go back to the math, (and just for simplicity) if we used an RPM of 12 and a stroke length of 1" I calculate that to be 12"/minute, or 1'/min.
So 1'/(3/5)min or 1.67'/min would be the actual forward speed on the cutting stroke.
So now take that 3.5 times increase (42rpm vs 12rpm) ... 3.5 X 1.67'/min = 5.85'/min. My chart above is pretty close, rounded to 6'/min.If we up the speed to, (your slowest), 42 RPM, that is 3.5 times faster than 12 RPM, so now are we cutting at 3 1/2 ' per min???
Now, lets take your rough degree examples and see how they come out using the logic in the text that I posted the link to. If I spread the dwell degrees across the Feed and Return strokes (didn't know what else to do with them) ... your shaper is closer to 4/7 feed and 3/7 return (per revolution).
I dropped a snippet of the formula into the spreadsheet below. We will substitute the 7/4 for the 5/3 (book example was 3/5 feed 2/5 return).
For this shaper (if your protractor was accurate ) you will have a constant of .1458 (using the 3/5 number it is actually .1389 ... they rounded to .14). Doing the math then, you would presumably have a speed of 1.75'/min, on the cutting stroke ... not that far different from the 1.67'/min above.
That is how I am understanding this shaper speed business after reading all those old documents for a day.