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Posted: Tue Mar 29, 2011 10:28 am
by Gene Howe
[quote="hdtran"]Dusty, think of the old-fashioned pennyfarthing bicycles.
Some have huge wheels]
That 'sweet spot' eludes me. I never vary the speed, whether resawing or "scrolling", the dial remains on the slowest setting.
What seems to be more important is the relationship between speed and number of teeth in the wood. But, since I never change the speed, I suppose it's all irrelevant anyway.
Maybe when (if) I get a Power Pro, I'll fiddle more with speeds.
Posted: Tue Mar 29, 2011 7:31 pm
by jcraigie
This is one of the reasons I like this forum so much, there is as much or as little information as you want just there for the asking.
Posted: Tue Mar 29, 2011 7:44 pm
by dusty
michaeltoc wrote:Because blade/belt length has NOTHING to do with the its speed.
The speed is only a function of RPM and diameter. The formula I gave and the two from the Shopsmith manuals are exactly the same -
they simply plugged in 11" diameter for the bandsaw and 3" diameter for the belt sander.
Michael, help me understand. I realize that both formula yield the same answer when used as stated.
BUT
Where did they plug in the 11" number in 2.88*RPM = FPM or in
(9.42*RPM)/12 = FPM?
Posted: Tue Mar 29, 2011 8:04 pm
by JPG
dusty wrote:Michael, help me understand. I realize that both formula yield the same answer when used as stated.
BUT
Where did they plug in the 11" number in 2.88*RPM = FPM or in
(9.42*RPM)/12 = FPM?
Circumference = Pi x d Pi = 3.141 x 11[in] = 34.55 in
Divide by 12 [in/ft] = 34.55 / 12 = 2.879.... ft = distance per revolution
Multiply by RPM ........
For 3" belt sander Pi x d = 3.141 x 3 = 9.424 . . .
Capisce?
Posted: Wed Mar 30, 2011 6:39 am
by michaeltoc
dusty wrote:Michael, help me understand. I realize that both formula yield the same answer when used as stated.
BUT
Where did they plug in the 11" number in 2.88*RPM = FPM or in
(9.42*RPM)/12 = FPM?
0.262 x D x RPM = FPM
0.262 x 11" = 2.88
0.262 x 3" = 0.786, and 9.42/12 = 0.785 (difference due to rounding)
Posted: Wed Mar 30, 2011 7:57 am
by dusty
michaeltoc wrote:0.262 x D x RPM = FPM
0.262 x 11" = 2.88
0.262 x 3" = 0.786, and 9.42/12 = 0.785 (difference due to rounding)
Hmm. First year arithmetic.
Posted: Wed Mar 30, 2011 8:39 pm
by charlese
robinson46176 wrote:There is an old story of a young boy who asked his father "how does this light work?" His father then proceeds to explain how power is generated. How power is transmitted. How the house fuse box (I said it was an old story) was made. All of it was interspersed with all of the proper laws and theories of the process so that the lad would have a good understanding of the whole process. When the father was done the now properly confused boy turned to his mom and asked "How does this light work?" The mom just said "you just flip that switch over there on the wall..." The boy smiled and said "OK, thanks" and went on to something else...
I always liked that story.
Francis - That is an excellent story!!!!! Thanks!:D