Regulating band saw speeds

For reference, the reason that you can't regulate the speed of an induction motor by just turning down the voltage (that's what a variac does) is how the motor controls the current draw under normal conditions. A motor is also a generator. When a motor starts turning, it starts generating a voltage (counter EMF or CEMF) that opposes the voltage that's making it turn (EMF) . When the CEMF balances the EMF, the speed and current stabilize.

If you put more load on the motor, the speed is reduced and the CEMF is reduced. Without the counter effect, the current increases, adding enough torque to the motor to hold the new, lower speed and set a new balance. If too much load is added, the rotor will stall and maximum current starts to flow. If the control system (or operator) doesn't shut it down, the high current will generate high heat in the windings, burning out the motor. Running at reduced speed and high current, even though still turning, will over-heat the motor and eventually damage it.

VFDs control speed by changing the frequency and adjusting voltage and current for optimum performance. This is quite easy to do on a 3-phase motor, not so easy on single-phase. I'm using a jack-shaft on my bandsaw conversion. Much easier and cheaper.

Thanks for that explaination.

I guess if I use the base from the AMT, I won't have enough room under there to mechnically regulate the rpms. (?)
 
Sat the Power King on the AMT base.. fits almost perfect. The Dayton motor turned out to be 1HP, twice the size of the old Craftsman.

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I like the smaller footprint.. it takes up less than half the space of the original stand. I plan on sand blasting and painting the base dark green. The Power King paint, although not too bad, definitely shows it's age, but I like that it is original. What do yall think, should I paint it too or leave it alone. Perhaps another color than forest green for the base and saw.. maybe gray?
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The lamp cleaned up nice. USA made by Dayton. This alone was worth the 10.00 to me. :)

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Heck yeah, it was worth $10.00. The light is nice.
Bet you moved the Band saw by the table when you broke the trunnions.
Looks like a Delta clone. That motor is about $200.00 new.
Thanks,
Tony
 
Heck yeah! As mr breeze said... Man, I gotta move to your town- no good deals like that by me! Not even on Craigslist! :)

Since you are asking opinions, I would leave as much of the original paint as possible- can't beat that experience these machines have been through in -100 years?! Fantastic.


Bernie
 
Heck yeah, it was worth $10.00. The light is nice.
Bet you moved the Band saw by the table when you broke the trunnions.
Looks like a Delta clone. That motor is about $200.00 new.
Thanks,
Tony

I laid it side ways in my truck and then shifted it 90 degrees so I could close the topper and the sudden weight on the table broke the trunnions. Poorly made. The Power King is all solid steel! Loaded it the same way and nothing broke.

Learned something though.. be careful when you load something in the truck. I was lucky I was only buying it for the base :))
 
Heck yeah! As mr breeze said... Man, I gotta move to your town- no good deals like that by me! Not even on Craigslist! :)

Since you are asking opinions, I would leave as much of the original paint as possible- can't beat that experience these machines have been through in -100 years?! Fantastic.


Bernie

I don't know about that.. I have seen some nice lathes for sale up north where you're at.. I rarely see any for sale down here. Rarely see any American made machine stuff at all.. I was just lucky and also the dude was a nice guy.
 
I like the original finish on the saw myself. I also like the original stand the saw was setting on though it is a bit clumsier I suppose. I don't suppose you want to sell your old original stand do you?????
 
I like the original finish on the saw myself. I also like the original stand the saw was setting on though it is a bit clumsier I suppose. I don't suppose you want to sell your old original stand do you?????

I thought about making a work table out of it, but If you were in South Florida, I would give it to you.

Nice that some one apperciates it, but to be honest with you, I don't want to go through the hassel of disassembling it and shipping it.. I know this sounds cold, but that's the way it is.. I would rather use it for something before going through that.

Now If you knew a forum member here who could pick it up for you..:))


Probably cost 1.98 back in the day.. It really isn't heavy duty, but it is structured and unique.. I like the way the legs curve..

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I thought about making a work table out of it, but If you were in South Florida, I would give it to you.

Nice that some one apperciates it, but to be honest with you, I don't want to go through the hassel of disassembling it and shipping it.. I know this sounds cold, but that's the way it is.. I would rather use it for something before going through that.

Now If you knew a forum member here who could pick it up for you..:))


Probably cost 1.98 back in the day.. It really isn't heavy duty, but it is structured and unique.. I like the way the legs curve..

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Actually, it is just real traditional. My vert bandsaw sets on a stand that could be it's twin. I have a 4" wood jointer on another stand that looks just like it as well. Those stands were the norm back when those machines were made.
 
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